Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2005
Publication Date: 7/24/2005
Citation: Kuhn, M.T., Hutchison, J.L., Van Tassell, C.P. 2005. Effects of complex vertebral malformation gene on production and reproduction [abstract]. Journal of Dairy Science. 88(Suppl. 1):140. Interpretive Summary:
Technical Abstract: Approximately 3 million records from about 1.7 million daughters of sires with known genotype for complex vertebral malformation (CVM) were used to estimate the effect of the CVM allele on lactational milk, fat, and protein yield, SCS, and days open. The linear model used for analysis included the fixed effects of herd-year-season, parity, age-at-calving, CVM status of sire, and the random effects of animal, permanent environment, and error. With random mating, the difference between carrier and homozygous normal bulls estimates the quantity (true effect)/[(q + 1)*(q + 2)] where q is the frequency of the CVM allele and "true effect" is the true difference between homozygous normal and carrier cows. Estimates of CVM gene frequency, based on random samples of the cow population, do not appear to be available. Thus, estimates from the linear model were doubled (corresponding to q = 0) which provides a lower limit for the estimate of the true effects. Using a gene frequency even as high as 0.1 (an upper limit estimate for q, based on usage of CVM sires) had only a small effect on the estimates beyond doubling. For all traits, effects were minor. Lactational milk yield was 160 kg higher for carriers while lactational fat and protein were 4 and 5 kg higher, respectively, for cows from carrier sires. The difference in SCS between carriers and normals was only 0.03 and carriers averaged only 2 more days open than non-carriers. Given the lethal aspect of CVM, the small effect on days open may be a result of intentional avoidance of inbreeding which, to date, may have led to the avoidance of most carrier x carrier matings. These results indicate that elimination of the CVM allele from the population would not have any direct detriment for performance traits. Exclusion of cows whose sires have unknown genotype, as done in this study, could lead to bias. Further research will be done to ascertain the potential magnitude of such a bias and possible methods to correct for such a bias, if it exits.