![]() ![]() The ergot alkaloids that cause fescue toxicosis also disrupt the hair follicle growth cycle, which interferes with hair coat shedding and, in turn, further increases the potential for heat stress. In cattle, one side-effect of fescue toxicosis is peripheral vasoconstriction, which reduces the animal’s ability to dissipate heat. coenophiala produces ergot alkaloids that benefit the forage by increasing drought tolerance and pathogen resistance, but negatively impact livestock to varying degrees. Tall fescue ( Lolium arundinaceum) is the most widely available forage in the United States, thanks in part to its symbiotic relationship with the endophytic fungus Epichloë coenophiala. In the United States, much of the beef herd that is at risk of heat stress is also at risk for fescue toxicosis. However, there is currently no national-scale genetic evaluation for heat tolerance. In the cow-calf sector, a portion of this economic impact is a result of lowered calf weaning weights caused by reduced dam productivity. beef cattle industry more than $360 million each year in 2003, which equates to ~ $518 million in 2020 after adjustment for inflation. Economic losses attributable to heat stress cost the U.S. Late-shedding cattle will need to partition energy that could have gone towards growth and production towards overcoming heat stress. In warm climates, cattle that shed their winter coat earlier and more completely have an adaptive advantage over later-shedding herd-mates. There is evidence of quantitative variation in the rate and timing of this yearly shedding across taxa, including cattle. Our results will aid beef cattle producers in selecting more sustainable and climate-adapted cattle, as well as enable the development of similar routine genetic evaluations in other breeds.Īt the beginning of the summer, many mammalian species molt thick winter coats in response to changing day length in order to prepare for warmer temperatures. This work contributes to a continuing trend in the development of genetic evaluations for environmental adaptation. Functional enrichment analyses using genes that were located within 50 kb of these variants identified pathways involved in keratin formation, prolactin signalling, host-virus interaction, and other biological processes. GWAA identified 176 variants significant at FDR < 0.05. Together, these results indicate that economic gains can be made by using hair shedding score breeding values to select for heat-tolerant cattle. Our results suggest modestly negative genetic and phenotypic correlations between a dam’s hair shedding score (lower score is earlier shedding) and the weaning weight of her calf, which is one metric of performance. Hair shedding score was moderately heritable ( h 2 = 0.34 to 0.40), with different repeatability estimates between cattle grazing versus not grazing endophyte-infected tall fescue. Here, we developed parameters for routine genetic evaluation of hair shedding score in American Angus cattle, and identified genomic loci associated with variation in hair shedding score via genome-wide association analysis (GWAA). Both heat stress and fescue toxicosis reduce profitability partly via indirect maternal effects on calf weaning weight. Furthermore, research suggests that early-summer hair shedding may reflect tolerance to fescue toxicosis, since vasoconstriction induced by fescue toxicosis limits the ability of an animal to shed its winter coat. The rate at which a beef cow sheds her winter coat early in the summer is an indicator of adaptation to heat and an economically relevant trait in temperate or subtropical parts of the world. Heat stress and fescue toxicosis caused by ingesting tall fescue infected with the endophytic fungus Epichloë coenophiala represent two of the most prevalent stressors to beef cattle in the United States and cost the beef industry millions of dollars each year. ![]()
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