Evaluation of Hydrated Lime Treatment of Free-stall Bedding and Efficacy of Teat Sealant on Incidence of Dairy Cow Mastitis

Abstract

Dairy cow mastitis is the inflammation of the mammary gland caused by trauma, chemical irritations and by infection caused by microorganisms. Mastitis is estimated to cost the US dairy industry about $1.8 billion annually. Infectious mastitis can be contracted from several sources including the cow’s environment such as wet, muddy, and manure-soiled paddocks and stalls where the cow lies down. The cow spends most of the time lying in a stall between milking periods where the teat ends can come in contact with contaminated bedding resulting in environmentally-acquired mastitis. A 12-month study was conducted to evaluate the use of hydrated lime as a germicidal treatment for dairy cow bedding to control mastitis. All Holstein cows at the E.V. Smith Research Center Dairy were evaluated by Dairy Herd Improvement Association (DHIA) records, and by analysis of the quarter, foremilk for somatic cell count (SCC), and for microbes by blood agar culture. These analyses were used to determine the udder health status of the cows and to allocate the animals to two study groups of 16 cows each. To each stall of both groups of cows, 0.77 kg of peanut hulls was spread over the stall. Fifty grams of hydrated lime was applied to the back 1/3 of the stalls for the lime bedding treatment group of cows. Fresh bedding was applied daily to the stalls of both groups of cows and new lime was added daily to the stalls of the treatment cows. Udder quarter, foremilk, collected prior to afternoon milking, was collected monthly from each of the cows in the two groups. The quarter milk was analyzed for somatic cell count (SCC) by the Wisconsin mastitis test and for Staphylococcus, Streptococcus, coliforms, and other bacteria by blood agar culture. Also on a monthly basis, the DHIA records of the study cows were used to collect composite SCC data. The SCC in milk increases in response to infection in the mammary gland, and according to published reports, a SCC in milk of >200,000/ml is indicative of an intra-mammary infection. Four levels of SCC were selected to compare the number of quarters in each cow group (control and lime-treated bedding) to determine the number of quarters that exceeded each SCC level. There were 43.65% and 38.04% fewer infected quarters in the lime-treated cow group compared to the control cow group at the >165,000/ml and > 200,000/ml SCC levels during 12-month study period, respectively. Based on DHIA composite milk data at the >165,000 SCC/ml and >200,000 SCC/ml levels, there were 9.96% and 32.88% fewer infected cows in the lime treatment group compared to the control group, respectively. The SCC legal cut off limit for sale of raw milk is =750,000/ml. There was a 47.08% reduction (P<0.03) in the number of quarters with >750,000 SCC/ml for the lime treatment cow group. Cows in the lime-treated bedding group had 73.2% fewer quarters infected with Staphylococcus, 72.84% fewer coliforms, and 73.95% fewer other bacteria compared to quarters of cows in the control group. The reduction rates for Staphylococcus (P<0.01) and coliform (P<0.01) infected quarters were significant for the cows bedded on the lime treated bedding. The study revealed that the application of 50 grams of hydrated lime daily to the back 1/3 of dairy cow free-stalls bedded daily with 0.77 kg of fresh peanut hulls reduced the incidence of mastitis in quarters of the cows using the lime-bedded stalls by approximately 45%. The cost to treat one lime stall was calculated to be $.011/day, or $4.02/cow/year. The economic benefit of the lime treatment was estimated to improve milk production by $42.51 ($46.53 - $4.02) /cow/year. Corollary to the lime study the efficacy of Orbeseal (a teat sealant) was also evaluated to reduce the incidence of mastitis. Orbeseal was administered with the antibiotic Cephapirin at the time of cow dry-off in all cows at the farm except the non-lime and lime-treatment study cows