Utilizing genomic information to increase genetic gain and minimize
the unfavorable effects of inbreeding in the US Holstein population.

PRINCIPAL INVESTIGATOR: Dr. Christian Maltecca, North Carolina State University

DURATION OF PROJECT: January 1, 2018 to June 30, 2019

Executive summary of proposal: Within this proposal we aim at developing and utilize novel metrics of genomic relatedness and inbreeding to curtail the accumulation of harmful recessive loci in the population as well as maximizing the amount of additive variation available for selection in order to maintain maximum genetic progress per generation. Software to efficiently decrease the overall genomic load while maximizing genetic gain will be developed and tested in the US Holstein population. A list of unfavorable haplotypes across traits will be obtained and efficient methods to manage these haplotypes in the population deployed.

Breeding Holstein cows for heat tolerance using the slick hair gene.

PRINCIPAL INVESTIGATOR: Dr. Anna Denicol, University of California Davis

DURATION OF PROJECT: January 1, 2019 to June 30, 2022

Executive summary of proposal: Heat stress is estimated to cost the US dairy and beef industries $1.7 billion annually due to decreased milk production, reproductive failure and higher culling rates. In total, 45% of US dairy cows are located in areas affected by heat stress; by 2040-2060 average summer temperatures are projected to be warmer than the warmest temperatures on record. One way to decrease heat stress is to breed Holstein cows for heat tolerance based on the slick gene. The slick gene was first described in Senepol cattle and introduced into the Holstein breed by crossbreeding. Holstein cows carrying the slick genetics have shorter, sleek hair coats, higher sweating rate and are more tolerant to heat stress. Importantly, milk production is less affected in slick cows during heat stress, but there is currently no information about performance of young animals carrying the slick gene. Our aim is to produce slick Holstein calves and non-slick half-sisters, and compare their performance from birth to the first 30 days of lactation and beyond in commercial farms in California and Florida. Results from this project will be crucial to provide permanent solutions to heat stress through genetics and provide profitable dairy production in a warming world.

Identification of genetic and physiological aspects of double ovulation
and twinning in Holstein lactating cows.

PRINCIPAL INVESTIGATOR: Dr. Joao Paulo (JP) Martins, University of Wisconsin-Madison

DURATION OF PROJECT: January 1, 2020 to December 31, 2021

Executive summary of proposal: Twin pregnancies cause an estimated loss of $96 million/year on US dairy farms. Twinning is associated with increased pregnancy losses and metabolic and infectious diseases, and with reduced productivity and conception rates. Double ovulation is the primary cause of twinning in Holstein cows. Compelling evidence indicates that genetic factors and milk production are strongly associated with double ovulation and twinning rates. Milk production per Holstein cow will likely continue to increase significantly over the next 50 years, creating an expectation that both double ovulation and twinning rates will only rise unless strategies are identified to lessen the risk. The incidence of twins at calving is not the true reflection of twin pregnancies since there is a higher incidence of pregnancy losses in double ovulating cows. Thus, double ovulation phenotype is most likely the best way to determine genetic aspects associated with twin pregnancies and associated pregnancy losses in Holstein cows. Our objective is to identify SNPs and genomic regions and physiological aspects associated with double ovulation in Holstein cows. The results of this proposal will be critical for the development of genetic selection and treatment strategies to reduce double ovulation, twinning rates, and related economic losses in Holstein cows.

Genomic evaluation of diet digestibility

PRINCIPAL INVESTIGATOR: Dr. Chad Dechow, The Pennsylvania State University

DURATION OF PROJECT: January 1, 2021 to December 31, 2023

Executive summary of proposal: Future feed efficiency genomic evaluations will combine previously available data such as body weight composite with genetic evaluations for feed intake; the feed intake component of these evaluations will have low reliability and will not provide information on why certain cows appear more efficient. Mechanistic measures of feed utilization, such as diet digestibility, would be a valuable complement to such evaluations. We previously developed a cost-effective method to determine how effectively cows digest feed using fecal samples and demonstrated that higher digestive efficiency is genetically associated with milk-fat production. We propose to collect 1,400 fecal samples from approximately 900 genotyped cows over a two-year period. These samples will be used to conduct a preliminary genomic evaluation of digestive efficiency and we will determine genetic relationships to other traits. If genetic evaluation of diet digestibility via fecal sampling is established as a viable mechanism to select for feed efficiency, Holstein breeders will be included in the process of collecting feed efficiency phenotypes and feed efficiency evaluations will have higher reliability. Ultimately, increased feed efficiency will enhance the economic sustainability of dairy production.

Evaluation of feedlot performance, carcass traits, and sensory characteristics of SimAngus x Holstein steers and heifers, Holstein steers, and SimAngus beef steers

PRINCIPAL INVESTIGATOR: Dr. Jerad R. Jaborek, Michigan State University

DURATION OF PROJECT: January 1, 2022 to December 31, 2025

Executive summary of proposal (adapted version): Breeding dairy cows with beef sires has become an increasingly popular practice in the U.S. Some dairy farmers commonly use inexpensive semen simply to create a black-hided calf as their main beef sire selection criteria. This practice has given dairy beef cattle a poor reputation because of inconsistent feedlot performance and carcass yields. Breeding Holstein cows to beef without having genetic information about the sire could reduce profit potential. Many of these dairy beef cattle fall well short of producing a beef-type carcass and/or qualifying for the intended Certified Angus Beef premium. Additionally, publicly available comparisons are not available between dairy beef cattle, Holstein steers, and native beef cattle, regarding feedlot performance, quality grade, cut-out yield, and the eating characteristics of their beef. We propose the use of specifically selected SimAngus beef sires in a breeding strategy with Holstein cows to produce dairy beef cattle that will be compared with Holstein and native beef steers for feedlot performance, carcass quality, carcass yield, eating acceptability, and financial value.

Evaluating the impacts of heat stress on milk production of US Holstein cattle in Texas and Wisconsin and developing a genomic selection program for heat tolerance

PRINCIPAL INVESTIGATOR: Dr. Breno Fragomeni, University of Connecticut

DURATION OF PROJECT: January 1, 2023 to December 31, 2025

Executive summary of proposal: Heat stress accounted ~$1 billion in annual losses in 2003. Twenty years later, national evaluations do not yet account for heat stress or genotype-by-environment interactions across states with different overall climates. Texas and Wisconsin Holsteins represent high performing cows in contrasting climate regions. We will compare these two populations by characterizing production losses due to high temperature/humidity events and total heat load over a lactation. The genetic parameters of heat tolerance will be estimated and milk yield breeding values for bulls accounting for heat stress will be generated. Genotype-by-environment interactions will be evaluated to determine whether climate-specific selection programs for states with different average temperatures would be beneficial. Key outcomes from this work include current estimations of heat-related economic losses for US Holsteins, identification of critical heat stress thresholds, and optimized methods for genomic selection accounting for heat stress. While this proposal details plans to develop methodology on a 2 state subset, this analysis will be extrapolated to the entire population of US Holstein in future. Breeding for temperature resilient cows has obvious impacts for US dairy producers, and the ability to promote bulls with high evaluations for heat tolerance will be key to expanding into other markets, especially in East Asia.