Elwood Kirkpatrick Dairy Science Research Endowment: A Completed Project
The Elwood Kirkpatrick Dairy Science Research Endowment was started in 2007 to honor the work and support of Mr. Elwood Kirkpatrick for the dairy industry of Michigan and Michigan State University. The Endowment along with partnership support from the Department of Animal Science, Michigan Milk Producers Association, the Clinton E. Meadows Endowment, the College of Agriculture and Natural Resources, and Michigan AgBioResearch (formerly Michigan Agricultural Experiment Station) has partially funded several MSU dairy research projects addressing a wide range of topics. Reported in this issue is the summary of a completed project.
Michigan Bovine Leukosis Study
However, the possibility that the disease can cause less obvious changes in dairy cattle productivity is controversial. Early studies found no influence on milk production, incidence of mastitis, or reproductive performance [Jacobs et al., 1991]. In contrast, other studies reported negative effects of BLV infection on reproductive performance, milk production, and in particular, longevity [Pollari et al., 1993; Brenner et al., 1989; Pelzer, 1997; Ott et al., 2003]. It is probable that the negative effects of BLV on milk production and reproduction are reduced by early culling of poor-performing infected cows, and therefore the major effect of BLV in many herds may be primarily realized by reduced cow longevity. As part of the USDA-NAHMS 1996 dairy study, the estimated average reduction in productivity was approximately $59/cow for BLV test-positive herds [Ott et al., 2003]. A Virginia study suggested a loss of over $400/case of lymphosarcoma; however, subclinical cost was $64/cow per yr in herds with a BLV prevalence of 50% [Rhodes et al., 2003].
Herds were visited once during the summer of 2010 to complete a survey regarding facilities, history, and management practices. Additionally, DHI technicians collected milk samples during one routine test day for submission to the laboratory (AntelBio) for ELISA testing of BLV antibodies. We designed a herd profile as a practical method to estimate the herd prevalence of BLV- infected cows and the relationship of age to infection.
For the profile, we collected 40 milk samples per herd on the study; 10 samples each from first, second, third, and fourth or greater lactation cows. We also selected cows that recently calved, based on calving dates recorded from the previous month test date. To validate the BLV herd profile, we compared BLV milk ELISA with serum ELISA in 142 cows, and compared our profile sample size with whole herd milk ELISA in four herds. We determined that there was a 95% agreement between BLV milk and serum ELISA. Finally, with profile testing, we estimated herd prevalence of BLV-infected cows consistent with that obtained from whole herd testing.
The percentage of BLV-infected cows in herds ranged from 0% to 76%. The prevalence of infection in first-lactation cows (18%) was less than third-lactation and greater cows (42%). This may reflect the slow progression of the disease and/or exposure to transmission risks, e.g., through more frequent injections of adult cattle vs. heifers. Higher risk of BLV infection also was associated with larger herds, especially those that added replacement animals in the last 3 years.
We determined that higher prevalence of BLV infection in herds was associated with lower milk production per cow (annual rolling herd average basis), which agrees with previous research. Herds with higher prevalence of BLV infection had significantly lower proportions of older cows (third lactation or greater), which suggests that increased prevalence of BLV infection is associated with decreased longevity. Risk factors associated with the transmission of BLV are related to exposure of blood from infected animals. Thus, shared needles, palpation, tattoo pliers, dehorning, and to a lesser extent, nasal discharges, colostrum, and flies, all have been incriminated as sources of infection. Analysis of our survey data could not determine any single management practice that was significantly associated with increased risk of BLV infection. This suggests that the control of this disease is complex, and will result from multiple management practices that are part of a comprehensive herd plan.
Enhancing Fertility of Lactating Dairy Cows
Kirkpatrick Project: Bovine Leukosis
Lesson in Milk Marketing
Feed Margins & Risk Management
Manure Transport & Land Application
Raw Milk Worth the Risk?
Thumb H20 Project: Part 2
CMT & Milk Quality
Over $80,000 Scholarship Opportunities