Final Report for OS13-070
A comparison of compost bedded pack barn and deep-bedded sand freestall barn dairy herds to determine if differences exist regarding cow health and comfort. To date, no significant differences between mastitis incidence, cow cleanliness, or lameness have been noted. Bacterial data from the compost bedded pack barns has also been collected to determine how management of the barns affects health and cleanliness. No analysis has been run at this time, but shifts in population based on moisture content and internal compost temperature have been observed.
Recently, the popularity of compost bedded pack barns has unquestionably increased in the Southeast (at least 80 compost bedded pack barns have been constructed in Kentucky and interest has also been high in other Southeastern states). To the producer, the ultimate measure of compost bedded pack barn success is either bulk tank somatic cell count or clinical mastitis incidence. Improved milk quality, as evidenced by reduced somatic cell counts (SCC) and reduced clinical incidence of mastitis, is often cited as an advantage of the compost bedded pack barn. Nevertheless, the mechanisms for this relationship are not clear at this point, although it is certain that mastitis and housing interactions are complicated by the multifactorial nature of mastitis. In this project, we propose a longitudinal study of 5 compost bedded pack barns and 5 freestall barns for a full year to quantify how changes in pack performance relate to changes in milk quality at both the cow and the herd level. By examining trends in somatic cell counts and bacterial culturing of milk from all cows with clinical mastitis, we will develop an increased understanding of the pathogens of importance in compost bedded pack barns. Also, we will be able to relate changes in somatic cell count and mastitis incidence, by pathogen, to changes in compost performance and bacterial populations within the pack.
Compost barns may improve the quality of milk produced in the Southeast, where milk quality has historically been a major source of competitive disadvantage. Improved milk quality, as evidenced by reduced somatic cell counts (SCC) and reduced clinical incidence of mastitis, is another commonly discussed benefit. This improved quality is particularly evident in herds in which cows had previously been pastured year-round without access to any housing. Kentucky dairies with compost bedded pack barns reported an average SCC of 247,000 cells/mL. Among farms with DHIA records, the average SCC was reduced from 407,000 to 259,000 (P < 0.05) after moving into a compost bedded pack barn (Black et al., 2011). While this result may seem to contradict conventional wisdom that more direct exposure to manure in bedding would increase mastitis risk, most producers believe that keeping the cows dry and clean minimizes exposure to pathogens and thus improves milk quality. Because of the warm climate, the compost bedded pack barn fits the Southeast particularly well. This system has already provided many dairy producers with improved milk quality and cow welfare. However, additional management information and understanding is needed to full capitalize on the potential of this system. With so little objective information available for any of these areas, the outcomes of this project could have a significant impact on the sustainability of compost bedded pack barns in the Southeast. The resulting systems-based outreach programs and publications will lead to improved compost bedded pack barn construction, management, and subsequent economic viability of these dairy farms, with reduced environmental impact and less stress for the farm managers.
Historically, conventional bedded pack systems have been associated with poor cow hygiene scores and increased mastitis incidence (Berry, 1998, Peeler et al., 2000, Ward et al., 2002). Producers and scientists expect that compost bedded pack barn systems will behave the same way in regard to cow hygiene. Barberg et al.(2007) observed a mean hygiene score of 2.66 for the 12 compost bedded pack barns visited while Shane et al.(2010) reported a mean hygiene score of 3.1 for six compost bedded pack barns. Additionally, Lobeck et al. (2011) and Fulwider et al. (2007) compared compost bedded pack barns to more common housing and bedding systems. Lobeck et al. (2011) found that compost bedded pack barns had a higher hygiene score (3.18) compared with cross-ventilated (2.83) and naturally ventilated (2.77) barns. However, there was no statistical difference between the three concerning mastitis incidences (33.4%, 26.8%, and 26.8% respectively). Conversely, Fulwider et al. (2007) found that compost bedded pack barns, mattress based freestalls, sand based freestalls, and waterbed based freestalls reported similar hygiene score for all systems (2.2, 2.2, 2.3, and 2.2, respectively). Klaas et al. (2010) determined 51.2% of cows scored as dirty (a score of 3 or 4) in three compost bedded pack barns in Israel, ranging from 10% to 90%. The CBP with higher temperatures housed cleaner cows compared to the two farms not generating optimal composting heat, suggesting that cow hygiene score reflects compost performance. Researchers observed SCC of 133,000 cells/mL, 214,000 cells/mL, and 229,000 cells/mL for the three barns (Klaas, 2010). Previous experimental results suggest the compost bedded pack barn provides the potential for excellent udder health given that management in the parlor and CBP management are excellent.
The purpose of this study is to explore the differences in clinical mastitis incidence between compost bedded pack barns and sand based freestalls in Kentucky. Until now, there has been no research looking strictly at mastitis incidence in compost bedded pack barns. Improved milk quality, as evidenced by reduced somatic cell counts (SCC) and reduced clinical incidence of mastitis, is often cited as an advantage of the compost bedded pack barn. Nevertheless, the mechanisms for this relationship are not clear at this point, although it is certain that mastitis and housing interactions are complicated by the multifactorial nature of mastitis. In this project, we propose a longitudinal study of 5 compost bedded pack barns and 5 sand bedded freestalls for a full year to quantify how each systems performance relates to changes in milk quality at both the cow and the herd level. By examining trends in somatic cell counts and bacterial culturing of milk from all cows with clinical mastitis, we will develop an increased understanding of the pathogens of importance in compost bedded pack barns and sand freestalls. Also, we will be able to relate changes in somatic cell count and mastitis incidence, by pathogen, to differences between housing systems. Moreover, we will examine similar relationships between housing system and cow locomotion, cleanliness, and mastitis severity score.
Objective 1: Cow Health and Welfare Dynamics, Key Personnel: Bewley, Arnold, Coyne
Data will be collected from eight farms participating in a comprehensive field study for 2 years. The following data will be collected and compared with compost success metrics (Objective 2):
- Establish cow and herd level benchmark monitoring criteria (including somatic cell counts, clinical mastitis incidence, mastitis pathogen prevalence, locomotion scores, and hygiene scores). Emphasis will be placed on standards for animal care outlined in the National Dairy FARM (Farmers Assuring Responsible Management) Animal Care Guide).
- Dairy producers in the project will be asked to rank important cow and herd based criteria for judging compost bedded pack barn performance. Periodic feedback will be requested from producers throughout the project.
- Bi-weekly bacteriological evaluation of sampled compost material from compost bedded pack barns will be conducted including total bacterial and fungal counts; staphylococcus counts; streptococcus counts; and coliform counts (fecal and total (240 samples collected for 10 farms over a 2 year period).
- Aseptic quarter milk samples will be collected from all clinical mastitis cases from 10 farms to evaluate mastitis pathogen prevalence within this system and compare to pack bacteria levels.
- Daily bulk tank milk yields and number of cows milked will be collected to determine average milk yield for each farm.
- Individual animal somatic cell counts and milk yields will be collected from Dairy Herd Improvement Association records.
- Herd level estrus detection and culling rates will be collected from Dairy Herd Improvement Association records.
- Bi-weekly locomotion, hygiene, and hock scores will be assessed by the animal sciences graduate student using the standards established in the National Dairy FARM (Farmers Assuring Responsible Management) Animal Care Guide.
- Compost Bedded Pack Sample Collection & Culture. On a bi-weekly basis, shortly after routine mixing of the compost, composite samples from nine locations in each barn will be collected at depths of 0-6 inches (0-15 cm) and transported to UK where it will be stored at 4 C until use. At UK the samples will be mixed, and a representative portion sent to Regulatory Services for nutrient analysis. Portions of the remaining samples will be suspended in buffer, shaken to release bound microbes, diluted, and plated in triplicate on SMA or PDA agar (for isolation of bacteria and fungi, respectively). After incubation at 25 C for a period of at least one week the colony forming units representing viable bacteria and fungi in the samples will be counted. Repeated measures analysis of colony forming units for each compost depth will be performed to assess the effect of barn, time, and position on the microbial properties of the compost. These values will be related to chemical properties of the compost at each sample period.
- Clinical Mastitis Sample Collection & Culture
Bacteriological cultures and SCC will be collected for all quarters when any quarter is diagnosed with clinical mastitis. Approximately 5 ml of milk will be collected aseptically from all four quarters of a cow diagnosed with clinical mastitis. These samples will be frozen and shipped weekly for bacterial evaluation. Samples will be taken aseptically according to procedures recommended by the National Mastitis Council (Hogan et al., 1999). Teat ends will be washed thoroughly, dried with individual disposable paper towels, and then cleaned with 70% isopropyl alcohol swabs. Milk samples for microbiological analysis will be collected into sterile pop-cap tubes and taken directly to the lab or kept frozen until evaluation. Another 5 ml of milk will be sampled from each quarter for SCC samples, which will be taken directly after bacteriological cultures are taken in non-sterile pop-cap tubes. These samples will be preserved and refrigerated until taken to UK’s Regulatory Services. Milk samples will be examined following procedures recommended by the National Mastitis Council (Oliver et al., 2004b) and as described by Oliver et al. (1994). Briefly, foremilk samples (10 ml) from each mastitis sample will be plated onto one quadrant of a trypticase soy agar plate supplemented with 5% defibrinated sheep blood (Becton Dickinson and Company, Franklin Lakes, NJ). Plates will be incubated at 37°C and bacterial growth will be observed at 24-hr intervals for 3d. Bacteria on primary culture medium will be identified tentatively according to colony morphologic features, hemolytic characteristics, and catalase test. Isolates identified presumptively as staphylococci will be tested for coagulase by the tube coagulase method (Remel, Lenexa, KS), Mannitol salt (Becton Dickinson and Company) and DNase agar (Becton Dickinson and Company). Isolates identified presumptively as streptococci will be evaluated for growth in 6.5% NaCl, hydrolysis of esculin and CAMP-reaction. Streptococcal organisms will be identified to the species level using the API 20 Strep System (bioMérieux Inc.). Gram-negative isolates were evaluated by their biochemical reactions on the following: MacConkey agar (Becton Dickinson and Company), triple sugar iron agar (Becton Dickinson and Company), urea agar (Becton Dickinson and Company), oxidase (Becton Dickinson and Company), motility, indole and ornithine decarboxylase (Becton Dickinson and Company) and identified to the species level using the API 20E System (bioMérieux Inc.).
- DHIA and Cow Observations.
Daily bulk tank milk yields will be collected from milk cooperatives along with number of milking cows to calculate average daily milk yield. Dairy Herd Improvement Association records (DHIA) will be utilized to collect individual animal somatic cell counts, milk yields, estrus detection rates, and culling rates. These metrics will help in relating compost performance to herd-based metrics used in daily management by dairy producers. Lastly, locomotion, hygiene, and hock scores will be collected bi-weekly from each cooperating farm (n=8) by a graduate student using the standards for each subjective measurement established in the National Dairy FARM (Farmers Assuring Responsible Management) Animal Care Guide (NMPF, 2009).
This study was conducted using seven Kentucky sand bedded freestall barns (SFB) and eight compost bedded pack barns (CBP) barns from May 2013 and May 2014. Each farm was visited every 2-weeks for a total of 26 visits over the study period. The study focused on housing effects on cow hygiene, locomotion, and mastitis indicators. All barns were used as the primary housing facility for lactating cows. All herds on this study were enrolled in DHIA. To be enrolled in the study, herds needed to maintain a yearly mean SCC < 300,000 in 80% of the herd during the year before enrollment in the study. Overall, 48 ± 5 cows were scored by the same observer per farm. All herds were fed a total mixed ration, used fans to cool cows in the barn, and had regular bedding additions. Sand bedded freestalls had fresh sand added at least once every two weeks and were groomed daily. Compost bedded pack barns were tilled twice daily for all but three farms. Two producers tilled the barn once daily from December through early February. One producer chose not to till the barn at all from December through early February and added fresh bedding daily.
An initial survey included specifics concerning the farm, milking technique, dry cow treatment, and mastitis management. Performance records from DHIA were collected with the permission of participating farmers. Records included in subsequent analyses were: test day milk production (kg per cow), average herd SCC (cells/mL), mastitis infection prevalence (MIP; % of animals in each herd with a test day SCC ≥ 200,000 cells/mL), and lactating herd number. Bulk tank somatic cell count (BTSCC) from every milk pick-up was obtained from fluid-milk buyers with farmer permission. Researchers provided cooperating herds with a Tycon ProWeatherStation (model # TP1080WC; Tycon Systems, Buffdale, Utah) to record barn temperature and humidity, ambient temperature and humidity, and wind speed. Supplemental ambient temperature, humidity, wind speed, and precipitation data was collected from University of Kentucky’s Weather Center stations. Hourly ambient temperature and relative humidity were collected from the cities of Bowling Green, Covington, Fort Knox, Frankfort, Glasgow, Hopkinsville, Lexington, and Somerset. Daily wind speed and precipitation were collected from the counties of Adair, Barren, Boone, Casey, Franklin, Logan, Madison, Metcalfe, Taylor, and Warren.
Herd locomotion, hygiene, and hock health. Locomotion, hygiene, and hock scores were collected for each farm every 2 weeks (n = 26 visits per farm). Over the study period, the same observer scored 50 cows at each farm visit. If fewer than 50 cows were housed in the primary housing facility, all cows were scored. If herd size was 100 to 150, cows with even identification numbers were scored. One herd included ≥ 400 cows housed in four compost barns. For this study, a single compost barn was selected as a representation of the farm, limiting the number of animals recorded to the range of 100 to 150 cows. If herd size was 150 to ≥ 200, cows with identification numbers ending in 3, 6, or 9 were scored.
Locomotion was assessed using the 5-point scoring system of Sprecher et al., (1997) where 1 = normal, 2 = mildly lame, 3 = moderately lame, 4 = lame, and 5 = severely lame. Observations were collected by encouraging the animal to move on a concrete surface, such as the feed alley or parlor exit, and evaluating the legs and back arch. Locomotion scores ≥ 3 were classified as clinically lame, with scores ≥ 4 classified severely lame. Hygiene evaluation was conducted using the 4-point system of Cook and Reinemann (2007) where: 1 = clean, 2 = moderate dirt, 3 = plaques of dirt with hair visible and 4 = confluent plaques of dirt with no hair visible. Hocks were evaluated as 1 = no swelling or missing hair, 2 = no swelling with missing hair, and 3 = swelling or lesion through hide (Nocek, 2010).
Barn analysis. Sand freestalls and compost bedded pack barns were visited every 2-weeks (n = 26 visits) on the same day as herd locomotion, hygiene, and hock scoring. Surface temperature was collected in three predetermined stalls in each row of freestalls from the center of the back one-third of the stall using an infrared thermometer (accuracy of ± 1?C; Fluke, model 62, Everett, WA, USA). The observer stood behind the stall and pointed the laser light at the center of the stall. The temperature was recorded when the digital readout no longer fluctuated. Stalls were located on both ends and the center of the freestall row. If an even number of stalls existed in a row, the center stall was offset with one side having a single stall less between the center stall and the end stall. If a double row of freestalls had an even number of stalls on each side, the offset occurred on different ends of the freestall barn.
Each CBP was divided into 9 sections (adapted from Black et al., 2013). At the center of each section, the observed collected surface temperature using an infrared thermometer (accuracy of ± 1?C; Fluke, model 62, Everett, WA, USA). The observer pointed the laser light at the center of the section. The temperature was recorded when the digital readout no longer fluctuated. Samples of compost material were collected at the same site using a 59.1 cm3 measuring cup for a 118.3 cm3 composite sample in a 3.8 L plastic bag. Each bag was thoroughly mixed and stored on ice until transfer to a freezer at 4.44°C at the University of Kentucky. University of Kentucky Regulatory Services laboratory personnel determined moisture concentrations using procedures defined by Peters et al. (2003).
Clinical mastitis identification and collection. All participating farmers were provided a kit including alcohol soaked cotton balls in a sealed container, sterile sample collection tubes (14 ml tube with snap top, Fisher Scientific Company LLC, Hanover Park, IL, USA), a laminated instruction sheet, and a binder containing recording material. The instruction sheet included steps for sterile milk collection and a mastitis severity guide adapted from Hogan et al. (1989). Mastitis severity was reported as 1 = abnormal milk (flakes, clots, or watery appearance) without swelling of the affected quarter, 2 = normal or abnormal milk and swelling of the affected quarter, or 3 = abnormal milk, swelling of the affected quarter, and systemic signs (fever, reduced rumen function, dehydration, weakness, depression, loss of appetite, or rapid pulse; Hogan et al., 1989a, Bramley et al., 1996). Samples were frozen following the milking collected and picked-up for culturing at each 2-week visit. Samples were stored in a -18°C freezer at the University of Kentucky until culturing the week following each visit period.
Clinical mastitis culturing. Clinical mastitis culturing occurred at the University of Kentucky Animal and Food Science Department microbiology laboratory. Clinical mastitis samples were thawed at room temperature and plated in duplicate. A 0.1 mL sample was inoculated onto a half of a Difco (BD Diagnostic Systems, Detroit, MI) Columbia blood esculin agar plate with 5% calf’s blood using a plastic L-shaped agar spreader. Plates were incubated for 48 h at 37°C followed by bacterial growth observation. Use of colony morphology and hemolytic characteristic analysis allowed for tentative bacteria identification on the primary culture medium. Mastitis pathogen isolates were placed in brain-heart-infusion broth and incubated for 24 h at 37 °C. Heat fixing of 10 µL of each broth culture to a microscope slide was conducted, followed by Gram staining. Gram stains were performed by drenching each slide in crystal violet for 1 min, Gram’s iodine for 1 min, alcohol for 30 s, and safranin for 30 s. Between steps, slides were rinsed with water and blotted with bibulous paper. Slides were examined under a microscope for gram-negative (retain crystal violet; purple shade) and gram-positive (fail to retain crystal violet and take counter-stain color; pink to red shade) identification and all isolates were further evaluated by Vitek 2 Compact (bioMérieux, Durham, NC). A milk sample returning ≥ 3 colony types was deemed contaminated.
Additional analyses. To remove bias from well-managed herds, an additional analysis was conducted using bulk tank somatic cell counts from all herds in Kentucky enrolled in DHIA from January 2013 to January 2014. Data was collected from the Kentucky Milk Safety Branch. The Kentucky Dairy Development Council was contacted, and the housing systems for all herds included in the analysis were determined from past experiences with the dairy producers. Housing facilities were identified as compost bedded pack barns, freestall barns, tie-stall barns, conventional bedded pack barns, or pasture based housing. Some dairy producers used multiple types of housing, referred to as mixed housing. One subset of mixed housing was included in the analysis as compost bedded pack barn with freestall housing. All other housing combinations were referred to as mixed housing.
Inclusion criteria. To limit bias from lack of data, inclusion criteria were determined before analyses. All analyses including DHIA data required a minimum of 6 DHIA tests on file for the study period (half the year accounted for). One herd was excluded from locomotion, hygiene, hock, and bulk tank SCC analyses because of lack of DHIA data (< 6 tests for the year). Two farmers on DHIA test declined participation in the SCC analysis provided by DHIA as an additional service. Consequently, 2 herds were excluded from mastitis infection prevalence and SCC analyses because of lack of somatic cell data from DHIA. Several farmers on the study were not sampling all mastitis cases. One farmer did not continue taking samples after August 2013, another after November 2013. To include herds that were consistently sampling, reported clinical mastitis incidence analyses required 13 weeks of data. Four compost bedded pack and 3 sand freestall herds were excluded from the reported clinical mastitis incidence analyses because of lack of mastitis data (< 13 weeks of data for the year).
Herd information. The MEANS procedure of SAS 9.3 (SAS Inst. Inc., Cary, NC) was used to determine the lactating cow number, DHIA test day milk yield, DHIA SCC, BTSCC, and stocking density for each herd in the study. The MEANS procedure of SAS was also used to create a herd mean locomotion, hygiene, and hock score and the BTSCC for each herd at each visit period. The means were included in the MIXED analyses in SAS comparing variables between barn types. The FREQ procedure of SAS was used to determine the percentage of cows in each herd and barn type with perfect hock scores, perfect locomotion, clinical lameness, and severe lameness.
Housing comparison. The MIXED procedure of SAS was used to develop all models for all barn type comparison analyses. Somatic cell count and MIP data for 12 herds across the study period were adjusted for 5th and 95th percentiles to remove the impact of extreme outliers. Reported clinical mastitis incidence data for 8 herds across the study period were adjusted for 5th and 95th percentiles to remove the impact of extreme outliers. Explanatory variables for locomotion, hygiene, and hock score included barn type and maximum ambient temperature humidity index (THI) group. Temperature humidity index was calculated using the following equation (NOAA, 1976):
THI = temperature (°F) - (0.55 - (0.55 * relative humidity/100))
* (temperature (°F) - 58.8)
Temperature humidity index was adjusted for 5th and 95th percentiles to remove the impact of extreme outliers. Adjusted THI data was grouped as cool or warm defined as below or above the median maximum ambient THI of 66.30, respectively. Locomotion, hygiene, and hock score were compared as a herd mean for each farm and visit period across time. Variables were repeated by visit period with farm as subject. Stepwise backwards elimination was used to remove non-significant 2-way interactions (P ≥ 0.05). All main effects remained in the model regardless of significance. The model generated LSMeans (± SE) for locomotion, hygiene, and hock scores for each barn type and THI group.
Bulk tank SCC and DHIA herd SCC explanatory variables were barn type, maximum ambient THI group, and mean herd rear cow hygiene score. Variables were repeated by visit period with herd as subject. Stepwise backwards elimination was used to remove non-significant 2-way interactions (P ≥ 0.05). All main effects remained in the model regardless of significance. The model generated LSMeans (± SE) for BTSCC and DHIA herd SCC for each barn type and THI group.
Mastitis infection prevalence and RCMI explanatory variables were barn type, maximum ambient THI group, and mean herd rear hygiene score. Mastitis infection prevalence and RCMI were calculated as a herd percentage for each visit period. Mastitis infection prevalence was the % of the herd with a DHIA SCC ≥ 200,000 cells/mL at each visit period. Reported clinical mastitis incidence was calculated using the following equation:
Variables were repeated by visit period with herd as subject. Stepwise backwards elimination was used to remove non-significant 2-way interactions (P ≥ 0.05). All main effects remained in the model regardless of significance. The model generated LSMeans (± SE) for MIP and RCMI for each barn type and THI group.
Mastitis pathogens. To determine differences in proportion of clinical pathogens, χ2 analyses were conducted using the FREQ procedure of SAS at a < 0.05 significance level. Tables were generated with pathogen group as a percentage of total isolates per barn type. Nine groups of pathogens were included in the analysis: no growth, coagulase-negative staphylococci, environmental streptococci, Escherichia coli, Klebsiella species, Staphylococcus aureus, yeast species, other gram-negative species, and other gram-positive species. To determine differences in mastitis severity, χ2 analyses were conducted using the FREQ procedure of SAS at a < 0.05 significance level. Tables were generated with severity code (1, 2, and 3) as a percentage of total isolates per barn type.
Yearly changes. The GLM procedure of SAS 9.3 was used to determine differences between compost bedded pack and sand freestall barns at each visit period. Hygiene score, locomotion score, lying surface temperature (°C), DHIA herd somatic cell count (cells/mL), and bulk tank somatic cell count (cells/mL) were included in the analyses, with the LSMeans (± SE) for each barn type compared by each visit period. Tukey’s test for multiple comparisons was used with a < 0.05 significance level.
An additional analysis was conducted using the GLM procedure of SAS 9.3 to determine the differences in BTSCC among all housing types in Kentucky using the DHIA management system. Housing types included in the analysis were compost bedded pack barns, freestall barns, tie-stall barns, bedded pack barns, pasture based, and mixed housing. The LSMeans (± SE) for each housing type was compared for the period between January 2013 and January 2014. Tukey’s test for multiple comparisons was used with a < 0.05 significance level.
During the study, 178 ± 108 and 84 ± 37 cows were housed in compost bedded pack and sand bedded freestall barns, respectively. Dairy Herd Information Association reported mean daily milk production over the year was 33.69 ± 4.29 and 32.15 ± 4.83 kg per cow per day for compost bedded pack barns and sand bedded freestalls, respectively. All farmers pre- and post-dipped their cows with iodine based (pre - 7 herds; post – 10 herds), chlorine based (pre - 4 herds; post – 2 herds), peroxide based (pre - 4 herds; post - none), or a mixture of lactic acid, phosphoric acid, and sodium chlorite (pre – none; post – 3 herds) teat dips. Cloth or paper towels were used to dry the teats of cows before milking unit attachment. Cows were milked in herringbone (7 herds), parallel (4 herds), and parabone (2 herds) parlors. Most (7 herds) milked twice daily, with 4 herds milking 3 times per day seasonally and 2 herds milking 3 times per day continuously.
Yearly mean (± SD) daily milk yield, DHIA weighted average SCC, BTSCC, total cow resting area, and stocking density for each cooperating herd are reported in Table 2.2. Through the questionnaire, researchers asked farmers to report the dimensions of the compost bedded pack area (m2) or the number of stalls available to cows in a freestall barn. Space per cow was calculated as the amount of stalls available for cows in freestall barns (100 cows in 100 stalls = 100% stocking density). Space per cow was based on providing 9.3 m2 per cow in compost bedded pack barns (9.3 m2 per cow = 100% stocking density).
Sand bedding is a non-insulator, maintaining a cool surface temperature even in warm ambient temperatures (Stowell and Inglis, 2000). In a previous Kentucky study, compost bedded pack barn surface temperatures remained near ambient temperatures (9.9 ± 9.4 and 10.5 ± 8.0°C for surface and ambient temperature, respectively). This was achieved through evaporative cooling of the compost surface coupled with barn ventilation (Black et al., 2013). In the current study, the temperature of each barn type’s lying surface was not different between barn types over the year (17.81 ± 9.03°C and 16.12 ± 8.52°C for compost bedded pack and sand freestall barns, respectively; P = 0.95), although similar variations in surface temperature at each visit period occurred throughout the year in both barns (P < 0.001). The changes over the year corresponded to changes in ambient temperature and maximum THI. Drastic increases in the surface temperature in both barns occurred at cooler ambient temperatures (< 10°C) at the same visit period (December 21, 2013). The surface temperature increases may be because of cow body heat warming the lying surface, or a warmer visit period than the mean ambient temperature for the preceding and following 2-wk periods.
Hock health. Overall, LSMeans (± SE) of hock score were not different between barn types (1.00 ± 0.00 for both housing types; P = 0.12). Of all mean herd hock scores, 88.72% were equal to a score of 1 (no swelling or lesion), with no herd having a mean score greater than 2 (n = 390, 1 to 1.08). In each barn type, percentages of scores equal to 1 were 91.35 and 85.71% in compost bedded pack and sand bedded freestall barns, respectively. The lack of difference may be because of the cow comfort aspects of both the compost bedded pack barns and the sand freestall barns. Sand allows movement with the animal, reducing friction on the hocks and increasing the cushion provided to the cow (Bickert, 1999). Compost bedded pack barns maintain a soft and dry lying surface, which may be why excellent hock health was maintained in this study.
van Gastelen et al. (2011) reported decreasing hock injuries with softer and dryer bedding (r = -0.41; P = 0.05). Freestalls using foam mattresses maintained a lower incidence of cows with healthy hocks (no swelling or lesions) than those using box compost, sand, or horse manure (20.5 ± 6.7 vs. 64.0 ± 10.5, 54.6 ± 8.2, and 54.6 ± 4.5%, respectively; P < 0.001). When only hock lesion incidence was considered, cows housed in freestalls using box compost (composted biodegradable household waste) held the lowest incidence compared to sand or foam mattresses (25.8 ± 3.8 vs. 41.4 ± 6.5 and 42.1 ± 9.6%, respectively; P = 0.006 and 0.002). Hock swelling occurred at a higher prevalence on foam mattresses compared to sand freestalls (10.6 ± 3.4 vs. 2.1 ± 1.7%, respectively; P = 0.005). Severely damaged hocks (both lesions and swelling) occurred most often on foam mattresses, with sand having the lowest incidence followed by box compost and horse manure (26.8 ± 3.2 vs. 2.0 ± 2.8, 3.5 ± 4.7, and 5.5 ± 5.4%, respectively; P < 0.001; van Gastelen et al., 2011). These results were similar to the current study, with sand bedded freestalls and box compost bedded freestalls having the most desirable hock scores. Although box compost is different from compost bedded pack barns, these results show that sand and compost were both able to maintain a high incidence of healthy hocks as a freestall base.
Barberg et al. (2007b) reported a greater percentage of all animals scored presenting a hock lesion in compost bedded pack barns than the current study (25.1 vs. 8.7%, respectively). Klaas et al. (2010) reported no hock or body lesions on cows housed in Israeli compost barns. These researchers also observed fewer herds (n = 3) over a shorter period than the current study which may explain the absence of lesions in these herds (Klaas et al., 2010).
Contrary to this study, Lobeck et al. (2011) and Fulwider et al. (2007) reported a lower incidence of hock lesions in compost bedded pack barns compared to sand, waterbeds, or rubber-filled mattresses in freestalls. Lobeck et al. (2011) noted that lesion prevalence (score ≥ 2 divided by number of animals scored) was 3.8% in compost bedded pack barns with a higher percentage of 31.2 and 23.9% in cross-ventilated and naturally ventilated sand freestall barns (P < 0.001). No lesions were recorded for cows housed in compost barns by Fulwider et al. (2007). Researchers did report lesions on 25, 35.2, and 71.6% of herds housed on sand, waterbeds, or rubber-filled mattresses. No statistical analyses were conducted between compost barns and freestall systems and only numerical differences between the housing types were reported (Fulwider et al., 2007).
Locomotion. Herd locomotion score (LSMeans ± SE) was not different between compost bedded pack (2.22 ± 0.05) and sand bedded freestall barns (2.27 ± 0.06) (P = 0.57). In compost bedded pack barns, 27.44% of animals were scored as 1 (perfect locomotion) and the same score was observed in 28.79% of cows in sand freestall barns. The highest percentage of cows were scored mildly lame (score 2) for both barn types (33.31 and 30.42% for CBP and SFB, respectively). Percent of cows in each barn type scored clinically lame (score ≥ 3) were 39.24 and 40.80% in compost bedded pack and sand freestall barns, respectively. The percent scored severely lame (score ≥ 4) were 10.71 and 13.33% in compost bedded pack and sand freestalls barns, respectively. No differences between barn types at each visit period was observed (P = 0.99), although locomotion score did vary over the year in both housing systems (P < 0.001).
Black et al. (2013) reported 69.3% of all cows housed in Kentucky compost bedded pack barns as perfect locomotion (score 1) versus the 27.44% in the current study. Lower clinical and severe lameness prevalence was noted in Kentucky compost bedded pack barns (11.9 and 5.0 %, respectively; Black et al., 2013). Shane et al. (2010) observed the amount of lame and severely lame cows over a year (one visit every season) in 6 compost bedded pack barns. The percentages of lame cows were 7.1, 9.7, 10.2, and 9.2% in fall, spring, summer, and winter, respectively. Percentages of severely lame (locomotion score ≥ 4) cows were recorded as 2.0, 2.4, 2.0, and 3.8 % in fall, spring, summer, and winter, respectively. Overall, 9.1 % were lame (locomotion score ≥ 3) and 2.5 % severely lame (Shane et al., 2010). This was slightly greater than the 7.8 % of reported cases of clinical lameness in 12 compost bedded pack barns by Barberg et al. (2007b). Less clinical lameness was likely because of 2 herds with no lame cows (Barberg et al., 2007b).
Contrary to the current study, Lobeck et al., (2011) reported that cows housed in compost bedded pack barns exhibited decreased lameness incidence compared to cows housed in low-profile cross-ventilated and naturally ventilated sand freestall barns with 4.4, 13.1, and 15.9% of herds having a locomotion score ≥ 3. Severe lameness incidence did not differ between housing types (0.8, 1.0, 1.4%, P ≥ 0.05;). Similarly, New York researchers observed decreased lameness prevalence after transitioning to compost bedded pack barns (23.7 to 3.4% of the herd; Petzen et al., 2009), reducing treatment costs to the dairy producer by $33,000. Researchers noted that lameness prevalence seemed to be lower in compost bedded pack barns than freestalls that were not bedded with sand and lower than bedded pack barns. However, no visual differences were noted between compost bedded pack barns and sand bedded freestalls similar to this study (Klaas and Bjerg, 2011).
Hygiene. Unlike other studies, no differences were observed between mean herd rear cow hygiene score (mean of flank, upper leg and flank, and udder hygiene scores) between compost bedded pack barns (2.21 ± 0.05) and sand bedded freestall barns (2.27 ± 0.05; P = 0.38). Black et al. (2013) reported a similar mean herd hygiene score of 2.2 ± 0.7 (n = 1,699) for compost bedded pack barns in Kentucky. Both housing types on this study were below the mean herd hygiene score for 50 herds housed in freestalls in Minnesota, USA (no stall base information) reported as 2.82 ± 0.5 (Barberg et al., 2007b). Shane et al. (2010) reported a mean herd hygiene score of 3.1 (range 2.2 to 3.8) for all cows housed in CBP with several different bedding materials. A slightly lower mean hygiene score (2.66 ± 0.19) was reported by Barberg et al. (2007b) for compost bedded pack barn housed cows in Minnesota. The differences were likely because of inclusion of compost bedded pack barns that were maintaining 20 cm internal temperatures and moisture contents within the recommended ranges, which was not a requirement for some previous studies. This enforces the importance of bedding management in compost bedded pack barns.
The higher mean herd hygiene score reported by Shane et al. (2010) corresponded to maintenance for a lower moisture content than the moisture content in the current study (29.6 to 45.8% moisture vs. 59.9 ± 6.6%, respectively). This observation by Shane et al. (2010) was contrary to results in a companion study (Eckelkamp et al., 2014) in which increasing moisture content increased hygiene score (P < 0.001). Minnesota dairy producers and researchers also noted difficulty in maintaining a clean and dry barn environment in winter, when moisture content was greater (Barberg et al., 2007b). Lobeck et al. (2011) found that animals housed in compost barns exhibited greater overall hygiene score than sand bedded cross-ventilated and naturally ventilated freestall barns (3.18, 2.83, and 2.77; P = 0.024 and P = 0.010, respectively). The increase was because of greater winter hygiene scores in compost barns than in sand bedded cross-ventilated and naturally ventilated freestall barns (P = 0.007 and P = 0.029, respectively; Lobeck et al., 2011).
Hygiene scores for cows housed on compost barns were similar to those housed on waterbeds in freestalls, and lower than for cows housed in sand freestalls or rubber-filled mattresses. A greater percentage of cows had lower hygiene scores (1 or 2) in waterbeds (80.8%), mattresses (84.4%), and CBP (79.0%) than sand bedded freestalls (73.6%, P < 0.0001; Fulwider et al., 2007). However, when compared to straw bedding, cows using straw stalls were dirtier than those using sand (6.04 vs. 4.19, P < 0.001; Norring et al., 2008).
A slight increase in hygiene score occurred in the current study at the THI group below the median THI compared to the THI group above the median THI (2.27 vs. 2.20 ± 0.04 below and above, respectively; P = 0.02). However, the interaction between barn type and THI group was not significant (P = 0.76). The increase in hygiene score in the cooler THI group was 0.07 points higher than the warm THI group. Both hygiene scores were within the range of 2 to 3, indicating splashes of manure, but no confluent plaques of manure. No differences were observed between barn types over time (P = 0.99; Figure 2.5), with some variation between study periods over the year (P < 0.001). Lobeck et al. (2011) reported that animals housed in compost barns exhibited greater overall hygiene score than sand bedded cross-ventilated and naturally ventilated freestall barns (3.18, 2.83, and 2.77; P = 0.024 and P = 0.010, respectively). The greater overall hygiene score was likely because of greater winter hygiene scores in compost barns than in sand bedded cross-ventilated and naturally ventilated freestall barns (P = 0.007 and P = 0.029, respectively). Producers reported difficulty keeping compost barns at optimal moisture and temperature in winter (Lobeck et al., 2011). Although overall differences did not occur between barn types, the slight increase at the cooler THI level could indicate a similar situation in compost bedded pack barns and sand freestall barns.
Somatic cell count. Herd average somatic cell count from DHIA showed no differences between barn types, THI group, or hygiene score (P ≥ 0.05). Compost bedded pack and sand freestall barns both had yearly LSMeans (± SE) of 241,716 ± 21,450 and 228,796 ± 22,761 cells/mL respectively (P = 0.69). Sand bedded freestall barns were below the Kentucky state average of 237,000 cells/mL with compost bedded pack barns slightly above the state average (Norman and Walton, 2013). Black et al. (2014) reported similar findings with SCC in Kentucky compost bedded pack housed cows having a SCC of 252,860 cells/mL, below the Kentucky state average of 313,000 cells/mL. After transitioning to compost bedded pack barns, Minnesota dairy producers reported SCC as 325,000 ± 172,000 cells/mL (88,000 to 658,000 cells/mL), below the state average of 357,000 cells/mL (Barberg et al., 2007b).
No differences in SCC were observed between barn types over time (P = 0.58), with some variation in SCC between study periods over the year (P = 0.04). The lowest SCC in both barns occurred at the when lying surface temperatures were lowest in compost bedded pack and sand freestall barns. The mechanisms behind this phenomena are not fully understood, as mean rear cow hygiene score, pack moisture content, 20 cm internal temperature, and compost bedded pack bacterial counts all increased when SCC was lowest (Eckelkamp et al., 2014). Similar to observations by Barberg et al. (2007a), Klaas and Bjerg (2011), and Shane et al. (2010), excellent milking procedures were required to maintain low SCC and mastitis control. In the current study, all herds pre- and post- dipped their cows, used a clean paper or cloth towel to clean individual cows, and all but 1 herd dry-treated their cows. These practices may explain the low SCC over the year, even when the compost bedded pack barns were high in moisture content and low in composting temperature.
The lack of difference in hygiene score between barn types was reflected in the somatic cell count. Shane et al. (2010) reported a greater hygiene score of 3.1 (range 2.2 to 3.8) for all cows housed in CBP with several different bedding materials. Somatic cell count was only reported for the summer months (range 224,000 to 729,000 cells/mL) but was greater than that reported in this study (Shane et al., 2010). A slightly lower mean hygiene score (2.66 ± 0.19) was reported by Barberg et al. (2007b) with a corresponding reduction in mean SCC (325,000 ± 172,000 cells/mL). Again, these results were higher than this study reported for both hygiene score and SCC. Klaas et al. (2010) reported hygiene and SCC for three Israeli compost bedded pack barns (farm 1 (n = 59 cows), 2 (n = 458 cows), and 3 (n = 280 cows)). Unlike the previous studies, Farm 3 exhibited the cleanest cows on the study (10% scored as dirty vs. 90% scored as dirty on farm 2, mean 51.2 %) and returned the highest mean SCC (133, 000 ± 35,000, 214,000 ± 41,000, and 229,000 ± 46,000 cells/mL for farm 1, 2, and 3, respectively; Klaas et al., 2010).
Mastitis. Mastitis was measured in two ways in this study: producer reported clinical mastitis incidence and subclinical mastitis infection prevalence. Mastitis infection prevalence was not different between barn types, ambient THI group, and hygiene score or their interactions (P ≥ 0.05). The LSMeans (± SE) of mastitis infection prevalence were 21.79 ± 1.96 and 19.43 ± 2.08% for compost bedded pack and sand bedded freestall barns, respectively (P = 0.43). Similarly, mastitis infection prevalence showed no difference among compost bedded pack barns, cross-ventilated, or naturally ventilated sand freestalls (33.4, 26.8, and 26.8%, respectively; P ≥ 0.05; Lobeck et al., 2011). Conversely, the average mastitis infection prevalence was decreased after moving into the compost bedded pack barn from previous housing facilities (35.4% before, 27.7% after; P < 0.05; Barberg et al., 2007b).
Producer reported clinical mastitis incidence (RCMI) was not different between barn types, ambient THI group, or hygiene score (P ≥ 0.05). The LSMeans (± SE) of RCMI were 1.16 ± 0.13 and 1.18 ± 0.14% for compost bedded pack and sand bedded freestall barns, respectively (P = 0.90). A 12 month study from Canada reported incidence rate of clinical mastitis (IRCM per 100 cow years) over 3 barn types and 101 farms (Olde Riekerink et al., 2008). No differences were reported between tie-stalls, freestalls, or other housing (including straw yards and pasture-based herds) when all pathogens isolated from samples were considered (IRCM of 26.6, 19.1, and 19.5%, respectively; P ≥ 0.05). The results of this study indicated that all housing systems affected clinical mastitis similarly (Olde Riekerink et al., 2008). In 216 Finnish farms, cows were housed in tie-stall (89.8%) or loose-housing systems (10.2%). At the end of 2000, mean clinical mastitis prevalence was 30.6%. In the current study and previous studies, some samples may have been missed or not reported. The current study attempted to compensate by restricting the herds included in the analysis to those with at least 13 of the 26 visit periods with RCMI.
Causative pathogen. Mastitis causing pathogens were different between compost bedded pack and sand freestall barns (P = 0.03). Plates that were identified as No Growth (no growth occurred in the media) constituted 19.8 and 20.13% in CBP and SFB, respectively. The highest percentages of pathogens isolated in CBP were Escherichia coli (28.8%; n = 83 isolates) and environmental streptococci (17.4%; n = 50 isolates). The opposite was true for SFB with environmental streptococci (25.5%; n = 38 isolates) and E. coli (17.5%; n = 26 isolates) being the highest percentages of pathogens isolated. Overall, the highest percentages of isolates for both groups were E. coli and environmental streptococci (46.2 and 42.9% for compost bedded pack and sand-bedded freestall barns, respectively). In a companion study, the larger population of bacteria in the compost bedded pack were streptococci species compared to coliform species (7.22 ± 0.72 and 6.20 ± 0.62 log10 cfu/g on a dry matter basis (Eckelkamp et al., 2014). This was similar to studies by Barberg et al. (2007a) and Black et al. (2014) where environmental streptococci constituted larger percentages than coliforms (39.40 and 20.61% vs. 10.70 and 1.86% for environmental streptococci and coliforms in Minnesota and Kentucky CBP, respectively). The reason for higher E. coli isolates compared to environmental streptococci isolates was not fully understood. However, both bacterial types are present in the CBP environment in high numbers.
In a Canadian study, cows in tie-stall barns exhibited a higher reported incidence of Streptococcus uberis and Streptococcus species than freestall barns (IRCM of 2.19 vs. 0.67% and 1.21 vs. 0.37%, respectively; P ≤ 0.05; Olde Riekerink et al., 2008). In a Finnish study, environmental streptococci and coliforms made up a small percentage of 3.5% and 0.4% of all clinical mastitis isolates unlike the current study (Pitkälä et al., 2004). In a Wisconsin study, 50 herds using freestalls bedded with sand, sawdust, mattresses, a combination sand and sawdust, or mattresses with sawdust were observed. In these herds, E. coli was the most prevalent pathogen (22.5%), followed by environmental streptococci (12.8%; Oliveira et al., 2013). The differences between the North American studies and the Finnish study may be because of changes in climate and management differences between the countries.
Klebsiella species in the current study constituted a small percentage of causative pathogens in compost bedded pack housed cows (1.4%; n = 4 isolates) and sand bedded freestall barn housed cows (3.4%; n = 5 isolates). The amount of Klebsiella spp. isolates in this study were similar between housing types. However, Klebsiella spp. as a percent of total isolates was greater in sand bedded freestall housed cows (3.4 vs. 1.4%). Conversely, Newman and Kowalski (1973) intimated that green sawdust bedding increased Klebsiella species and mastitis incidence when compared to sand bedding. However, Verbist et al. (2011) reported that most Klebsiella pneumoniae was isolated from feces (125 isolates) and not from used sawdust bedding (20 isolates) or unused sawdust bedding (6 isolates) and concluded that K. pneumoniae could be prevalent in the environment without causing mastitis. In a Canadian study, Klebsiella species reported incidence in tie-stall barns was lower than that in freestall barns (IRCM of 0.40 vs. 1.00%, respectively; P ≤ 0.05). Relative to other pathogens in the Canadian study, Klebsiella spp. constituted a greater percentage than the in the current study (Olde Riekerink et al., 2008). In a Wisconsin study, Klebsiella spp. constituted a larger percentage of isolates (6.9%) than the current study in freestall housed cows. The difference may be due to climate changes, bedding differences, or management changes between Wisconsin, Kentucky, and Canada. In the current study, yeast species also constituted a small percentage of causative pathogens in compost bedded pack housed cows (2.8%; n = 8 isolates) and sand bedded freestall barn housed cows (2.7%; n = 4 isolates).
Staphylococcus aureus comprised a greater percentage of causative pathogens, with a slightly greater percent isolated from sand-freestall housed cows (6.7%; n = 10 isolates) than compost bedded pack housed cows (4.5%; n =13 isolates). In a Canadian study, cows housed in freestall barns had IRCM of 1.62% (per 100 cow years). This was the largest percentage of pathogens in freestall barn housed cows (Olde Riekerink et al., 2008). In the current study, coagulase negative staphylococci made up a larger percentage of isolates in compost bedded pack housed cows (7.6%; n = 22 isolates) compared to sand bedded freestall housed cows (4.0%; n = 6 isolates). In a Canadian study, CNS was the third most often isolated pathogen in freestall barns (0.68%) following Staphylococcus aureus and Klebsiella spp. (Olde Riekerink et al., 2008). In a Wisconsin study, freestall housed cows exhibited greater CNS (6.1%) than the freestall housed cows in the current study (3.5%) (Oliveira et al., 2013). The percentage was closer to that from compost bedded pack housed cows (6.3%). Unlike previously mentioned studies, CNS was most often isolated from Finnish cows (49.6%), with C. bovis (34.4%; environmental streptococci), and Staph. aureus (10.2%) as the next most commonly isolated pathogens (Pitkälä et al., 2004).
Other gram-negative species constituted 13.2% (n = 38 isolates) in compost bedded pack housed cows compared to 10.7% (n = 16 isolates) in sand bedded freestall housed cows. Other gram-negative species isolated included: Achromobacter xylosoxidans, Acinetobacter lwoffii, Brevundimonas species, Chryseobacterium indologenes, Citrobacter koseri, Enterobacter species, Pasturella species, Proteus mirabilis, Pseudomonas luteola, Rhizobium radiobacter, Salmonella species, Serratia marcescens, Sphingomonas paucimobilis, and Stenotrophomanos maltophilia. Other gram-positive species constituted 4.5% (n = 13 isolates) in compost bedded pack housed cows compared to 9.4% (n = 14 isolates) in sand bedded freestall housed cows. Other gram-positive species included: Arcanobacterium pyogenes, Bacillus circulans, Bacillus lentus, Bacillus licheniformis, Bacillus pumilus, Kocuria rosea, Kocuria varians, Lactococcus lactis, Lactococcus garvieae, Microbacterium species, and Paenibacillus amylolyticus.
Mastitis severity. Mastitis infection severity was different between CBP and SFB (P < 0.001). Some variance may have occurred between farms based on milking staffs’ interpretation of the severity scale. Severity score of 1 (abnormal milk but no swelling) made up the highest percentage of scores for both housing systems (66.8 and 51.1% of scores for CBP and SFB, respectively). The severity score of 2 (abnormal milk with swelling) was 29.9 and 32.1% of scores for CBP and SFB, respectively. The largest difference was the severity score of 3 (systemic signs). The most severe cases of mastitis were most often seen in SFB (16.8% of scores) compared to CBP (3.4%). In SFB, 43.5% (n = 10 isolates) of the cases scored as 3 were caused by E. coli. Similarly, in CBP 66.7% (n = 6 isolates) of the cases scored as 3 were cause by E. coli. Coliforms cause acute or peracute mastitis with occasional subclinical infections. Typically, coliforms cause no extensive damage or decrease in milk production. In some instances, endotoxemia from coliform mastitis may cause death within a few days (Jain, 1979). These results emphasize the importance of managing environmental mastitis pathogens regardless of bedding type.
Bulk tank somatic cell count. Previous research has suggested maintaining excellent cow preparation procedures and effective management in the barn and the milk parlor results in a low BTSCC (Barberg et al., 2007b). In the current study, no effect of barn type, ambient maximum THI group, and hygiene score or their interactions occurred for bulk tank SCC (P ≥ 0.05). Mean bulk tank somatic cell count remained below 300,000 cells/mL for both barn types (229,582 ± 18,478 and 205,131 ± 19,581 cells/mL for CBP and SFB, respectively; P = 0.38). No differences were observed between barn types over time (P = 0.63), with some variation between study periods over the year (P < 0.001). The changes over the year were similar to the changes in DHIA herd SCC over the year. Herd SCC was a monthly snapshot of herd performance, whereas BTSCC was a constant measure in all herds recorded with every milk load pick-up. Bulk tank SCC may be a more accurate representation of what occurred in each barn type on a herd level.
Similar results were observed when all herds on DHIA were compared. Compost bedded pack barns coupled with freestall barns had the lowest BTSCC (227,695 ± 22,706 cells/mL), with compost bedded pack barns, freestall barns, tie-stall barns, and mixed housing following but not significantly different (258,252 ± 24,526 to 260,411 ± 11,353 cells/mL; P ≥ 0.05). Bedded pack barns and pasture only housing were different from compost bedded pack barns coupled with freestall barns (303,612 ± 34,685, 316,896 ± 17,342, and 227,695 ± 22,706 cells/mL, respectively; P < 0.05). In Kentucky, many producers used compost bedded pack barns as special needs housing for lame cows, or cows with difficulty lying in stalls. This practice may improve the overall health status of the animal, by increasing lying time and limiting lying in alleyways, resulting in the decreased BTSCC for all herds using this practice in Kentucky.
A greater BTSCC of 261.17 × 1,000 cells/mL was reported in 12 compost bedded pack barns in Minnesota (Endres and Barberg, 2007). Barberg et al. (2007b) reported 3 of the 7 compost bedded pack barns in Minnesota included in the bulk tank analysis had a reduction in BTSCC of 90.31 ± 50.34 × 1,000 cells/mL (32.60 to 125.10 × 1,000 cells/mL; P < 0.01) after transitioning to compost bedded pack barn housing. One of the herds included in the analysis experienced an increase in BTSCC after the transition of 54.60 × 1,000 cells/mL (P < 0.01). In 12 Kentucky herds, BTSCC decreased after transitioning to compost bedded pack barn housing (323.69 ± 7.30 vs. 252.86 ± 7.11 × 1,000 cells/mL before and after transition, respectively; Black et al., 2013). This BTSCC for Kentucky compost bedded pack herds was slightly greater than that reported for compost bedded pack and sand bedded freestall barns in the current study.
In a national study, freestall, loose housing, tiestall, and pasture based systems were used on 52.9, 13.9, 26.9, and 6.3% of all operations (n = 1,013 dairies in 21 states). Housing was related to BTSCC (P = 0.01). In all housing systems, most herds had BTSCC between 200,000 to 400,000 cells/mL, with pasture-based herds having a greater percentage over 400,000 cells/mL (32.3% vs. 12.3, 24.6, and 19.3% in pasture, freestall, loose housing, and tiestalls, respectively). Sand, mattress, and newspaper bedding decreased BTSCC (P = 0.02, 0.006, and < 0.001, respectively). Composted manure and straw bedding was not significantly associated with BTSCC (P = 0.08 and 0.22; Wenz et al., 2007). These results differed from the current study, with all bedding types effecting BTSCC similarly. However, like the current study pasture based systems had a greater BTSCC than freestall, compost bedded pack, tiestall, compost bedded pack and freestall, and other mixed housing types (P ≥ 0.05). Moisture content of the lying surface affected BTSCC in winter and summer. During the winter, bedding that was usually dry or bedding that was wet 50% of the time made up a greater percentage of the herds with BTSCC > 400,000 cells/mL than bedding that was almost always wet (20.7 and 19.6 vs. 10.5%, respectively; P = 0.009). Similarly, bedding that was usually dry or bedding that was wet 50% of the time made up a greater percentage of the herds in summer with BTSCC > 400,000 cells/mL than bedding that was almost always wet (20.6 and 15.7 vs. 8.8%, respectively; P = 0.02; Wenz et al., 2007). In a companion study, compost bedded pack moisture content had no effect on BTSCC (P ≥ 0.05) but no evaluation on sand bedding moisture content was conducted.
Educational & Outreach Activities
Eckelkamp, E. A., J. L. Taraba, R. J. Harmon, K. A. Akers, J. M. Bewley. 2014. Somatic cell counts, mastitis infection prevalence, and mastitis pathogen distribution in compost bedded pack and sand freestall farms. 2014 ADSA-ASAS-CSAS Joint Annual Meeting. July 20 - 24, 2014, Kansas City, MO, ASAS.
Eckelkamp, E. A. 2014. Interactions of compost bedded pack barn moisture and temperature with dairy cow mastitis and locomotion. MS Thesis (unpublished), University of Kentucky, Lexington, KY.
Over the past two years, the University of Kentucky has participated in education opportunities for students and dairy farmers throughout Kentucky. On October 26, 2013, a Dare to Dairy event was held in which information about compost bedded pack barns as a housing system was given. Dare to Dairy is an event for elementary through high school students in the agriculture community that provides information and interactive learning opportunities involving milking practices, mastitis management, reproduction management, and housing facility information. On October 30, 2013, information on compost bedded pack barn management and effects on cattle was given as part of the National FFA convention farm tours. From March 11th to 13th, 2014 a short-course was provided for dairy producers in Kentucky. As part of this short-course, a 15 minute presentation was given on compost management, building guidelines, and effects of compost bedded pack barn housing on locomotion status and mastitis on dairy cattle. On August 27th, 2014, a Kentucky Milk Quality Conference was held to provide dairy producers and dairy food processors and marketers with information. A 5 minute presentation on the effects of compost bedded pack barn and sand bedded freestall housing on the locomotion status and mastitis incidence on dairy cattle.
To date, the project has indicated that there are no significant differences regarding lameness, observed clinical mastitis, subclinical mastitis, or bulk tank somatic cell count between compost bedded pack barns and sand bedded freestall barns in Kentucky herds. The results of this project also indicate that compost bedded pack barns and sand bedded freestall barns equally affect locomotion status, hygiene score, and hock health in Kentucky herds. Both barn types effect animals housed within similarly throughout the year, with changes in temperature and humidity having no interaction effects with barn type. In the future, the project may assist dairy producers in making housing decisions.
Adoption of compost bedded pack barns has increased in Kentucky, increasing from 47 barns in 2011 to over 80 in 2014. A companion study suggested a different goal for stocking density in compost bedded pack barns. Providing 116 ft2 per cow may increase the length of time a load of bedding will last in compost bedded pack barns and reduce the effects of rain and humidity on compost moisture content. This may decrease the costs associated with additional bedding farmers must pay to maintain a compost bedded pack barn. Farmers should maintain excellent milking procedures to maintain a low level of clinical and subclinical mastitis, regardless of housing type.
Areas needing additional study
Areas needing additional study are the impact of compost bedded pack barn housing in herds that are not maintaining a low herd somatic cell count throughout the year. This is necessary to identify how the compost bedded pack barns affect locomotion status and mastitis when they are not rigorously maintained at adequate levels. Further study would also be beneficial into the immune function of cows housed in compost bedded pack barns. It would be advantageous to assess if the difference in resting surface improves immune function, and to what extent the differences between other housing systems exist. The sleep positions in compost bedded pack barns also differ from freestall and tiestall barns. Studies assessing if the sleep cycles and duration of sleep differ in compost bedded pack barns may also affect the immune function and over well-being of cows housed within them.