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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Ruminant Diseases and Immunology Research » Research » Publications at this Location » Publication #62249
Title: GENETIC EPIDEMIOLOGY FOR QUANTITATIVE TRAIT LOCI: BOLA CLASS II ALLELES AS RISK FACTORS FOR HIGH SOMATIC CELL COUNTS IN LACTATING DAIRY COWS

Author
item DIETZ, ALLAN - FORMERLY USDA, ARS, NAC
item COHEN, NOAH - TEXAS A&M, COLL.STA., TX
item TIMMS, LEO - IA STATE UNIV., AMES, IA
item Kehrli Jr, Marcus

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Mastitis is an infection of the mammary gland that affects more than half of the dairy cows on over 95% of all dairy farms. On average, the US dairy farmer will lose more than $180 per cow annually. Mastitis is also a legitimate concern to consumers because of potential antibiotic residues as a result of treating cows for mastitis. The main benefit of the work reported here was the identification of a genetic identification scheme that identifies variability among cows for mastitis. A potential benefit of this type of research would be less use of antibiotics in cows to treat mastitis through selection of genetically superior breeding stock.

Technical Abstract: Lactating Holstein cows (n=100) from 93 dairy herds in Iowa, Wisconsin, Minnesota, and Illinois were genotyped for the major histocompatibility Class II, BoLA DRB3.2 locus using a PCR-RFLP genotyping system. DNA was obtained from milk samples after processing at a Dairy Herd Improvement Association (DHIA) facility. DHIA somatic cell count (SCC) scores were used to classify animals as acutely elevated (one test of SCC >500,000), chronically elevated (3 consecutive tests of SCC >300,000 or two consecutive tests of >5000,000), or healthy and, therefore, eligible as controls. For each cow with elevated SCC, control cows were selected that were matched for breed, lactation, herd, and days in milk (within 60 days). These cows were genotyped and a conditional step-wise logistic regression model was used to determine the relative odds for the ten alleles with a frequency >3% (3, 7, 8, 11, 12, 16, 22, 23, 24, and 27). BoLA class II DRB3.2*16 was found to be significantly associated (P <0.05) with the risk of acute increases in SCC when 516 cases and their controls were considered. No associated alleles were significantly associated with chronically elevated SCC. Therefore, we have identified the DRB3.2*16 allele as a potential risk factor for acute intramammary infection and established that use of DHIA milk samples is a satisfactory source of DNA for genetic epidemiologic studies.