Effects of complex vertebral malformation gene on production and reproduction M. T. Kuhn*, J. L. Hutchison, and C. P. Van Tassell Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD Abstract T INTRODUCTION ◆ Complex vertebral malformation (CVM) is a congenital defect found in Holstein calves that causes stillborn and aborted fetuses ◆ CVM is inherited through a single recessive gene ◆ Malformed legs, shortened neck, and dwarfism are physical defects caused by CVM ◆ Progenitor of CVM: Penstate Ivanhoe Star born January 1963 ◆ In 2002, Sattler reported a gene frequency of 5 to 9% in current Holstein cows OBJECTIVES ◆ Estimate the effect of the CVM allele on lactational milk, fat, and protein yield, SCS, and days open (DO) MATERIALS & METHODS ◆ Holstein cows calving from 2000 to 2004 ◆ Sire required to have a valid NAAB id and a known CVM genotype for analysis 10% of available records deleted because of unknown sire genotype ◆ Total of 4,458,541 records (459,731 CV records; 3,998,810 TV records) and 27,710 herds ◆ Model included: y = HY + YSM + parity + sire genotype + PE + A + e y = ME milk, ME fat, ME protein, SCS, or DO HY = herd-year of calving YSM = year-state-month of calving Parity = lactation 1 or 2+ Sire genotype = CV or TV CV: Tested for CVM and found to carry the gene TV: Tested, or verified by pedigree, to be free of CVM PE = permanent environment effect A = animal effect RESULTS Frequencies of CV, TV, and unknown bulls 1 Number of CV, TV, and unknown bulls that entered AI from 1964 through qMilk, kgFat, kgProtein, kgSCSDO no adj Phenotypic differences between CV and TV cows Due to Mendelian sampling and matings to cows of various CVM genotypes, daughters of CV (Cc) bulls could be homozygous normal and daughters of TV (CC) bulls could be heterozygous. Thus, the mean (daughter) difference between these 2 groups of bulls does not estimate Cc-CC; rather, it estimates the quantity: where q is the frequency of the CVM allele. Therefore, the mean difference between CV and TV bulls was multiplied by (q+1)(q+2) for varying levels of q to get an estimate of the effect of the CVM genotype, unbiased by genotypic frequencies of daughters. Phenotypic differences for milk, fat, protein, SCS, and DO between CV and TV daughters with no adjustment (no adj.), 0, 5, and 10% gene frequencies (q). 2 Year entered AI % CV bulls % TV bulls % unknown bulls CONCLUSIONS ◆ Prior to 2002, about 25 to 40% of bulls with NAAB codes were of unknown CVM genotype. Since 2002, about 6 to 8% have unknown genotype. Decisions on whether to test a bull for CVM may depend on outcome of early proofs. ◆ There appears to be some effect of CVM on milk, fat, and protein yield (carrier advantage) but little or no effect on fertility or SCS. ◆ The small effect on DO could be due to carrier x carrier matings. FUTURE RESEARCH ◆ Investigate use of mixture models to account for bulls with an unknown CVM genotype ◆ Estimate the effects of the CVM allele on type traits 1 Unknown bulls are potential CVM carriers because they had a known carrier ancestor but were not tested for CVM 2 Positive differences indicate higher mean for CV cows Percent of CV, TV, and unknown bulls that entered AI from 1990 through CV unknown TV