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

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.

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.
To be eligible for this study, herds must:
1. Have at least 10 DHIA tests from the previous year.
2. At least 80% of cows within each herd have DHI linear somatic cell score of <5.
3. Farm owners are willing to participate in this study for 52 consecutive weeks.
4. Five must be sand based freestall barns that have fresh sand added ?1x a week, and groomed ?2x a day.
5. Five must be compost bedded pack barns stirred consistently ?2x a day, and stay consistently below a moisture content of 65%.
6. All farms must use gloves, forestrip, pre- and post-dip, use an individual drying towel for each cow, and dry cow treat.
7. All farms must utilize a coliform mastitis vaccine.

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, hock scores, and teat end condition scores will be collected monthly from each cooperating farm (n=10) 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). During compost bedded pack barn visits, the compost bedded section of a barn will be divided into 9 equal areas (3 × 3) and monthly samples will be collected from the center of each section. Temperature will be measured at the surface with an infrared thermometer and at depths of 10, 20, and 30 cm with a compost thermometer. Bedding samples will be collected at 10 cm depth for moisture and nutrient content with samples analyzed by UK Regulatory Services.

All farms will remain on the study for 52 consecutive weeks. Cows entering the herd will have single aseptic quarter milk samples taken between days 2 and 5 of lactation. Similarly, all cows will have single aseptic quarter milk samples taken within the last 7 days before being dried off. Clinical mastitis cases will be determined by the presence of abnormal milk secretion (i.e. clots, flakes, or watery appearance). Single quarter milk samples will be taken aseptically from the infected quarter(s), labeled with the quarter they were taken from, and frozen immediately after collection. Samples will be frozen no longer than 10 days until laboratory analysis.

A written record will be kept of all cows with clinical mastitis. Clinical mastitis cases have been determined to be 14 days in length (Hogan et al., 1989a, Hogan et al., 1989b, Smith et al., 1985). Therefore, a new case of clinical mastitis will be declared if:
1. 14 days have passed between reports of first clinical signs of mastitis
2. A different pathogen is isolated from a clinical quarter (after treatment withdrawal period) regardless of whether 14 days have passed since isolation of the original pathogen
3. A new case is not recorded if the same pathogen is isolated (after treatment withdrawal period) when less than 14 days elapsed between reports of clinical signs.

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. 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 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.).

Statistical analyses (chi-squares) will be performed to compare pathogen-specific clinical mastitis incidence within and across farms and between systems. The MIXED procedure of SAS will be used to model management factors affecting clinical mastitis incidence.