FOR years, dairy producers have been selectively breeding their herds to encourage milk production, but such efforts may be hindering the cow herd's ability to bear offspring.
Scientists from five veterinary colleges across the country aim to investigate the issue using a new $3 million, multi-state U.S. Department of Agriculture grant.
According to an announcement from Cornell University, scientists will identify 12,000 cows that represent different breeding protocols, different U.S. geographic regions and different types of facilities.
Phenotypes will be explored using traditional time intervals and conception results, with physiologic measures and intermediate events such as resumption of ovarian cyclicity, postpartum uterine health and early embryonic and fetal loss. In addition, DNA will be collected from every cow.
With these data, the research team will identify cows in two groups — the most and least fertile — and compare changes in the DNA and corresponding fertility traits using genome-wide analysis, the announcement explained. Researchers will also identify significant molecular markers to be included in fertility DNA analysis kits.
"It is our central hypothesis that reproductive efficiency depends, to some extent, on biological factors that are influenced and modulated by genetic variation," said Dr. Rodrigo Bicalho, assistant professor of dairy production medicine at Cornell and a co-principal investigator for the project with Dr. Robert Gilbert at Cornell. "Because of this, we expect to find differences in the DNA for the most-fertile cows as compared to the least-fertile cows.
"With these data, we can develop a genetic test that can be used to predict fertility immediately after birth, eliminating our current reliance on the very time-consuming and costly process of selecting from registered and phenotypically beautiful animals with good pedigrees," he said. "Sometimes, looks and lineage can be deceiving, but currently, it takes years to confirm this."
The grant also will fund the development and delivery of a comprehensive, research-based extension program that will share the best selection practices for bull studs and for on-farm use with the replacement heifers that will most improve fertility and the overall productivity of dairy herds.
In addition to "extension road shows," the research findings will be shared with the USDA Agricultural Research Service's Animal Improvement Programs Laboratory and artificial insemination companies to incorporate fertility breeding values into the national genetic improvement program for dairy cattle.
"Fertility plays a key role in the efficiency of modern dairy production systems, and failure to attain timely conception is one of the major reasons that cows are separated from herds," Bicalho said. "The proposed genetic test will allow producers to make rational and cost-effective management decisions regarding cow uterine health and fertility. In effect, it will allow producers to identify superstar bulls by testing newborn calves.
"Instead of gambling on good looks, producers can evaluate the bulls' genes before incorporating them into the breeding program. To know which bull to use as a sire is the equivalent of winning the lottery," he added.