Over time the dairy industry has encountered the challenge of declining trends for fertility and overall health, across diverse production systems. A number of reasons may explain this performance slope, including changes in cow physiology related to greater milk production, challenges in nutritional management, housing, increased herd size, reduced estrous expression and changes in the genetic makeup
As fertility and health traits are multifactorial, assessing the degree of involvement of genetics is difficult. For example, genetic variation may be directly involved in the physiology of reproductive and immune processes, or could indirectly determine the behavior of other related traits that have an impact on fertility, fitness and health.
In the idea of addressing some of these questions, our team of scientists from different U.S. institutions was awarded a five-year grant to explore genomic variation (markers) associated with reproductive traits in dairy cattle.
The grant, from the USDA National Institute of Food and Agriculture (NIFA), funds the study named Genomic Selection for Improved Fertility of Dairy Cows with Emphases on Cyclicity and Pregnancy. This integrated project, including Colorado State University, Texas A&M, University of Florida, University of Wisconsin, Ohio State University, Cornell University, University of Illinois and University of Minnesota, is focused on a precise characterization of fertility and health phenotypes, paired with an in-depth assessment of genomic variation in a large population of cows.
The final goal is the identification of genetic markers linked to traits that include uterine health (metritis and endometritis), resumption of postpartum ovulation and conception and maintenance of pregnancy. Regarding health, metabolic diseases, lameness, mastitis and respiratory disorders were also considered.
At this point, our group has collected accurate fertility and health phenotypes (observable characteristics) in 12,000 Holstein cows on 16 farms in four regions of the U.S., encompassing different management and environments. Preliminary genome-wide analyses are confirming that there is potential for genomic selection in the traits of interest. This large-scale evaluation will eventually be combined with current selection traits to further refine genomic selection of cattle by dairy producers.
As the cost of genotyping decreases in time, the number of animals with genomic evaluations is expected to increase. If adequate markers for fertility, health and fitness are identified, molecular breeding values will be more accurately estimated for each trait, enabling the adoption of efficient selection throughout the entire dairy industry.
Research team:
Pablo Pinedo, Jose E.P. Santos, Gustavo M. Schuenemann, Rodrigo C. Bicalho, Ricardo C. Chebel, Klibs N.A. Galvão, Robert O. Gilbert, Sandra Rodrigez-Zas, Guilherme J.M. Rosa, Christopher Seabury, John Fetrow and William W. Thatcher 
Pablo Pinedo is with Colorado State University.
