Clinical Mastitis Incidence in Compost Bedded Pack Barns as Compared to Freestall Barns

View the project final report

• 2014 annual report

Commodities

• Animal Products: dairy

Practices

• Animal Production: housing
• Education and Training: on-farm/ranch research
• Soil Management: composting

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.

Introduction

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):

1. 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).

1. 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.
2. 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).
3. 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.
4. Daily bulk tank milk yields and number of cows milked will be collected to determine average milk yield for each farm.
5. Individual animal somatic cell counts and milk yields will be collected from Dairy Herd Improvement Association records.
6. Herd level estrus detection and culling rates will be collected from Dairy Herd Improvement Association records.
7. 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.

1. 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.

1. 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.).

1. 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).