Genetic Polymorphisms of Blood and Milk and Reproduction in Holstein Cattle1,2

Abstract

Associations of blood and milk protein polymorphisms with reproductive performance were examined in more than 32,000 services in 15,000 service periods of 6,000 cows and 700 service sires in Holsteins. Seven blood groups, one serum protein, and four milk proteins were analyzed for relation to reproductive traits including conception rate and days open. Associations between polymorphic systems and reproductive traits in 15 of 112 analyses were significant. The S blood system appeared most influential, having statistical significance in five of ten traits. These were conception rates in all services for female phenotypes, male phenotypes, and male by female phenotypes combined, conception rate in first services for female phenotypes, and probability of conception for female phenotypes. The FV system influenced conception rates in all services and in first services for male by female phenotypes combined. Four of the polymorphic systems had no effect on any of the reproductive traits. Maternal-fetal incompatibility was not evident from comparing parental combinations of aborted fetuses and normal calves. Conception rates declined with age of cow. For animals that ultimately conceived, conception rates did not decline consistently from first to later services within a service period.