scholarly journals Ruminal motility, reticuloruminal fill, and eating patterns in steers exposed to ergovaline

2019 ◽  
Vol 98 (1) ◽  
Author(s):  
Gyuchul Ahn ◽  
Kara Ricconi ◽  
Suelen Avila ◽  
James L Klotz ◽  
David L Harmon
Keyword(s):  
Tall Fescue ◽  
Rumen Content ◽  
Serum Prolactin ◽  
Fescue Toxicosis ◽  
Eating Patterns ◽  
Complete Understanding ◽  
Wireless System ◽  
Eating Pattern ◽  
Underlying Mechanisms ◽  
Pressure Changes

Abstract Fescue toxicosis is problematic for growing steers, causing lower DMI and productivity when fed endophyte-infected (E+) tall fescue. A complete understanding of underlying mechanisms of how fescue toxicosis affects growing steers is lacking. Therefore, the overall objective of this multiexperiment study was to determine whether ruminally dosed ergovaline (ERV) affects rumen motility, rumen contents, and eating patterns. In Exp. 1, an 8-h period to assess ruminal motility began 4 h after feeding by monitoring pressure changes using a wireless system for 21 d. Eight ruminally cannulated steers (283 kg BW) were pair fed with alfalfa cubes (1.5 × NEm) and assigned to endophyte free (E−; 0 μg ERV/kg BW/d) or E+ treatment (20 μg ERV/kg BW/d). Overall, E+ steers had more frequent rumen contractions (Seed P = 0.05 and day of feeding P = 0.02). On days 7 to 9, both treatments showed lower frequencies and E− steers had greater amplitude of contractions (P < 0.001) that corresponded with decreased DMI. In Exp. 2, steers remained in pairs assigned in Exp. 1 (322 kg BW), but reversed seed treatments while increasing ERV levels (titrated 0, 5, 10, 15, and 20 μg ERV/kg BW/d over 57 d). There were no differences between E− and E+ for frequency (P = 0.137) or amplitude of contractions (P = 0.951), but increasing ERV dosage, decreased frequency (P = 0.018) and amplitude (P = 0.005), coinciding with lower DMI. In Exp. 3, 8 steers (589 kg) were pair fed and ruminally dosed 15 μg ERV/kg BW/d, and rumen motility data were collected for 21 d. E− steers showed higher amplitude and lower frequency of contractions than E+ steers with seed (P < 0.001), day (P < 0.001), and seed × day (P < 0.04) effects, but rumen fill was not different between E− and E+ (P > 0.29). Serum prolactin concentrations were lower in E+ steers in Exp. 1 to 3. Eating patterns of pair-fed E− and E+ steers were relatively slower in E+ than E− (Exp. 4) by measuring every 2 h across 24 h. Number of meals were higher in E+ than E− steers, but meal duration and meal size were not different between treatments. Rumen content (DM%) tended to be higher in E+ than in E− when steers were fed once a day (P = 0.07), but there was no difference for rumen content (DM%) when E− and E+ steers were fed 12 times a day (P = 0.13). These results suggest the changes in rumen fill associated with fescue toxicosis may be driven more by changes in feeding behavior and eating pattern rather than by changes in motility.

Changes in Cytochrome P450 in Katahdin Ewes Fed Endophyte-infected Tall Fescue Seed Diets in Spring and Fall

2021 ◽  
Vol 99 (Supplement_2) ◽  
pp. 40-41
Author(s):  
Mohan Acharya ◽  
Joan M Burke ◽  
Erin Wood ◽  
Yan Huang ◽  
Palika Dias Morse ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Serum Concentration ◽  
Rectal Temperature ◽  
Tall Fescue ◽  
Repeated Measures ◽  
Ergot Alkaloids ◽  
Serum Prolactin ◽  
Fescue Toxicosis ◽  
Pregnancy Status ◽  
Soy Hulls

Abstract Objective was to examine the activity of cytochrome P450 (CYP), a liver enzyme that metabolizes ergot alkaloids which is hindered by this fescue toxin, as an indicator of fescue toxicosis in sheep. In spring and fall, ewes were blocked by age and BW, and randomly assigned to 1 kg/ewe/d of endophyte-infected (E+; 61% of diet in fall, 13% of diet in spring; 0.8 µg/g of ergovaline; and soy hulls, alfalfa pellets, cottonseed hulls, molasses) or non-infected (E-; same proportion of E+/season and same feeds) tall fescue seed supplement (n = 10/diet in each season) for 28 d, plus hay, mineral and water. Ewes were exposed to teaser, d -21 to 0, and intact rams, d 0 (first day of diet) to 30. Rectal temperature (RT), serum concentration of prolactin (using RIA), and CYP were determined every 7–14 d between d 0–28, and pregnancy status on d 56. PromegaTM P450-Glo assay was used to determine CYP from serum. Data were analyzed by using PROC MIXED with repeated measures (SAS). Rectal temperature of E+ compared with E- ewes was elevated on at least one day in fall and spring (diet × season × d, P < 0.001). Serum prolactin was lower in E+ compared with E- ewes (diet × d, P < 0.001) and lower in fall (P < 0.001). CYP was higher in E- ewes on d 28 in fall (diet × season × d, P = 0.008), but otherwise similar between diets, and higher in fall than spring (P < 0.001). There was an unexpected negative correlation between CYP and prolactin (R = -0.24; P < 0.009), but there appears to be a subpopulation of ewes with low prolactin and lower CYP. CYP activity in sera may not be a marker for fescue toxicosis in ewes.

scholarly journals 155 Evaluation of cytokine response as an indicator of genetic resistance to fescue toxicosis in purebred Angus cattle

2019 ◽  
Vol 97 (Supplement_1) ◽  
pp. 45-46
Author(s):  
Kyle Mayberry ◽  
Rebecca K Poole ◽  
McKayla A Newsome ◽  
Piush Khanal ◽  
Matthew H Poore ◽  
...  
Keyword(s):  
G Protein ◽  
Tall Fescue ◽  
Repeated Measures ◽  
Genetic Resistance ◽  
Cytokine Response ◽  
Serum Prolactin ◽  
Fescue Toxicosis ◽  
Animal Performance ◽  
Negative Effects ◽  
G Protein Coupled

Abstract Fescue toxicosis is a multifaceted syndrome common in cattle grazing endophyte-infected tall fescue. However, varying responses among cattle potentially implies genetic tolerance to the syndrome. Therefore, the objective was to evaluate the cytokine response of cows deemed either tolerant or susceptible to endophyte-infected fescue. Angus cows, 2–4 yrs old, grazed endophyte-infected tall fescue at two locations for 13 weeks starting mid-April 2016. A post-hoc analysis of animal performance was utilized to designate cattle into either tolerant (n = 20) or susceptible (n = 20) groups, based on physiological responses (changes in ADG) to chronic exposure to endophyte-infected fescue. Blood samples collected on weeks 1, 7, and 13 were used to evaluate serum prolactin (PRL) concentration. Cytokine concentrations were evaluated via Quantibody Bovine Cytokine Arrays. Data were analyzed using PROC MIXED of SAS with repeated measures. There were no differences by location or week. Tolerant cows tended to have decreased overall PRL concentrations compared to susceptible cows (98.3 and 138.4 ng/mL, respectively; P = 0.08). G protein-coupled receptor associated sorting protein (GASP)-1, a down-regulator of G protein-coupled receptors including D2-dopamine receptor a regulator of PRL secretion, was greater in tolerant cows when compared to susceptible cows (4.7 and 4.2 ng/mL; P = 0.03). Vascular endothelial growth factor (VEGF)-A was greater in tolerant cows when compared to susceptible cows (0.5 and 0.2 ng/mL; P = 0.02). Finally, interleukin (IL)-4, an anti-inflammatory cytokine, tended to be greater in tolerant cows when compared to susceptible cows (2.2 and 0.8 ng/mL, respectively; P = 0.07). Based on these data, greater concentrations of GASP-1, VEGF-A, and IL-4 in tolerant compared to susceptible cattle may mitigate the detrimental effects of fescue toxicosis, including suppressed PRL and vasoconstriction, leading to improved animal performance in a fescue environment. Additionally, these cytokines may serve as potential biomarkers for determining an animal’s tolerance or susceptibility to negative effects associated with endophyte-infected tall fescue

scholarly journals Effects of extended-release eprinomectin on fescue toxicosis, performance, and reproduction on fall-calving beef cows

2019 ◽  
Vol 3 (4) ◽  
pp. 1423-1434
Author(s):  
Mareah J Volk ◽  
Taylor R Krause ◽  
Rebecca S Stokes ◽  
Frank A Ireland ◽  
Daniel W Shike
Keyword(s):  
Milk Production ◽  
Tall Fescue ◽  
Extended Release ◽  
Treatment Time ◽  
Beef Cows ◽  
Serum Prolactin ◽  
Fescue Toxicosis ◽  
Time Interaction ◽  
Tick Count ◽  
Fall Calving

Abstract The objective of this experiment was to evaluate effects of extended-release eprinomectin on fescue toxicosis and impacts on performance and reproduction in fall-calving beef cows. Fall-calving Angus × Simmental multiparous cows [n = 335; age = 5.8 ± 2.1 yr; 586.5 ± 6.0 kg body weight (BW); 5.48 ± 0.05 body condition score (BCS)] were stratified by BW, age, and BCS and randomly assigned to one of three treatments. Treatments included a spring injection of extended-release eprinomectin (SERE) on day 0, a fall injection of extended-release eprinomectin injection (FERE) on day 84, and a saline control (CON). All treatments were administered at a rate of 1 mL/50 kg BW. Prior to the experiment, all cows were treated with oral fenbendazole to minimize parasite load. Cows grazed endophyte-infected tall fescue. Hair coat score (HCS), BW, and BCS were recorded on all cattle. Fecal egg count (FEC), respiration rate (RR), horn fly and tick count, hematocrit (% packed cell volume, PCV), and serum prolactin were analyzed on a subset of cows (35/treatment). On day 194, cows were artificially inseminated (AI) and 11 d following AI were exposed to bulls for 51 d. Milk production was estimated on day 210 on a subset of 85 cow–calf pairs (28–29/treatment). There was a tendency for a treatment × time interaction (P = 0.07) for FEC likely driven by an increase in FEC of the CON cattle at day 126 compared to SERE and FERE. There was a tendency for a treatment × time interaction (P = 0.06) for cow BW, largely driven by time differences; however, there was no effect of treatment (P = 0.84) on BW. There was no difference (P ≥ 0.13) in cow PCV, fly and tick count, BCS, HCS, RR, and serum prolactin throughout the experiment. Additionally, there was no difference (P ≥ 0.46) in Julian calving date, calf birth BW, or milk production between treatments. Interestingly, heifer calves born to FERE dams tended to have greater (P = 0.06) weaning BW compared to heifer calves born to CON dams. In addition, there was no difference (P ≥ 0.17) in heat patch scores, AI conception rates, or overall pregnancy rates between treatments. Extended-release eprinomectin did not impact cow growth performance, reproductive performance or fescue toxicity symptoms when grazing endophyte-infected tall fescue; however, calf weaning BW tended to be improved.

scholarly journals Effects of endophyte-infected tall fescue seed and red clover isoflavones on rumen microbial populations and physiological parameters of beef cattle1,2

2018 ◽  
Vol 3 (1) ◽  
pp. 315-328 ◽  
Author(s):  
Emily A Melchior ◽  
Jason K Smith ◽  
Liesel G Schneider ◽  
J Travis Mulliniks ◽  
Gary E Bates ◽  
...  
Keyword(s):  
Tall Fescue ◽  
Feed Efficiency ◽  
Red Clover ◽  
The United States ◽  
Serum Prolactin ◽  
Fescue Toxicosis ◽  
Seed Type ◽  
Final Body Weight ◽  
Nonesterified Fatty Acids ◽  
Tall Fescue Toxicosis

Abstract Lolium arundinaceum [(Darbyshire) tall fescue] toxicosis is responsible for substantial beef production losses in the United States, due to its negative effects on reproduction, growth, and feed efficiency. These effects are consequences of toxic alkaloids within tall fescue. Interseeding legumes, such as Trifolium pratense (red clover), into pastures has been shown to mitigate a portion of these effects. Clovers contain isoflavones, which may play a role in tall fescue toxicosis mitigation. The present study utilized 36 Angus steers to determine the effects of daily supplementation with a red clover-isolated isoflavone feed additive on physiological symptoms of tall fescue toxicosis and the rumen microbial environment over a 21-d period. Angus steers were initially stratified based upon their single nucleotide polymorphism genotype at the DRD2 receptor. Treatments were then randomly assigned in a 2 × 2 factorial arrangement within a completely randomized design, where treatment factors consisted of tall fescue seed type (endophyte-infected tall fescue seed vs. endophyte-free tall fescue seed) supplemented with and without the isoflavone additive. Steers that consumed endophyte-infected tall fescue seed had lower serum prolactin concentrations (P = 0.0007), average daily gain (ADG; P = 0.003), final body weight (BW; P = 0.004), and feed efficiency (P = 0.018) when compared with steers that consumed endophyte-free tall fescue seed. Serum insulin-like growth factor-1 (IGF-1) tended to be reduced with supplementation of isoflavones (P = 0.06) but was unaffected by seed type (P ≥ 0.10) and seed by treatment interaction (P ≥ 0.10). Isoflavones reduced serum glucose levels (P = 0.023), but neither seed type, isoflavones, or their interaction affected serum urea nitrogen (SUN), nonesterified fatty acids (NEFA), or insulin (P ≥ 0.10). Volatile fatty acid concentrations, dry matter intake (DMI), ruminal pH, and overall feeding behaviors were also unaffected by seed type or isoflavone treatments (P ≥ 0.10). Twenty-eight ruminal bacteria taxa shifted as a result of seed type or isoflavone treatment (P < 0.05). In this experiment, feeding isoflavones to Angus cattle did not completely mitigate all symptoms of fescue toxicosis. However, dose–response trials may aid future research to determine if dietary supplementation with isoflavones alleviates fescue toxicosis symptoms and promotes livestock growth and performance.

scholarly journals Urinary Alkaloid Excretion as a Diagnostic Tool for Fescue Toxicosis in Cattle

2000 ◽  
Vol 12 (3) ◽  
pp. 210-217 ◽  
Author(s):  
N. S. Hill ◽  
F. N. Thompson ◽  
J. A. Stuedemann ◽  
D. L. Dawe ◽  
E. E. Hiatt
Keyword(s):  
Tall Fescue ◽  
Ergot Alkaloid ◽  
Regression Coefficient ◽  
Health Assessment ◽  
Daily Weight Gain ◽  
Serum Prolactin ◽  
Fescue Toxicosis ◽  
Average Daily Weight Gain ◽  
Seasonal Factors ◽  
Physiologic Condition

Fescue toxicosis research studies have often included serum prolactin as a physiologic index of the disorder. Serum prolactin has not been used as a clinical measure of fescue toxicosis because of variation associated with sex and physiologic condition of the animal and climatic and seasonal factors. The primary excretory route of the alkaloids responsible for this toxicosis is the urine. Three pasture experiments were conducted to examine serum prolactin and urinary ergot alkaloid variability among steers continuously grazing endophyte-infected (E+) or endophyte-free (E-) tall fescue and among steers that were switched from one pasture form to the other. A fourth grazing experiment was used to examine how to best to manage the steers prior to sampling for urinary ergot alkaloid excretion. Coefficients of variability for urinary alkaloid excretion were consistently lower (46–65%) than serum prolactin (64–142%). Urinary alkaloid excretion patterns changed within 12 hours following switching steers from E+ to E- pasture or visa versa, but serum prolactin was recalcitrant to change. Because it is less variable and more dynamic than serum prolactin, urinary alkaloid excretion can be used for health assessment of steers grazing E+ and E- pastures. Regression analysis established a quadratic relationship between alkaloid excretion and average daily weight gain, with a regression coefficient of 0.86. Urinary alkaloid analysis was useful in determining whether cattle were consuming toxic tall fescue.

177 Ad Libitum Consumption of a 1:1 Blend of inorganic:organic Se by Steers Grazing Endophyte-infected Tall Fescue Increases Serum Prolactin and Alkaline Phosphatase Activity, but Not Average Daily Gain

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 94-95
Author(s):  
Kelsie Webb ◽  
Ronald J Trotta ◽  
Phillip Bridges ◽  
James Matthews
Keyword(s):  
Alkaline Phosphatase ◽  
Phosphatase Activity ◽  
Alkaline Phosphatase Activity ◽  
Tall Fescue ◽  
Average Daily Gain ◽  
Serum Prolactin ◽  
Negative Effects ◽  
Ad Libitum ◽  
Ad Libitum Intake ◽  
Daily Gain

Abstract To test the hypothesis that average daily gain (ADG) and clinical parameters of steers grazing novel non-toxic (NTE) or toxic KY-31 (TE) endophyte-infected tall fescue would be improved by ad libitum intake of vitamin-mineral mixes (V-M) that contain 27 ppm Se as a 1:1 blend of SELPLEX:sodium selenite (MIX) vs sodium selenite (ISe), 32 TE-naïve beef steers depleted of Se were randomly assigned to ad libitum consumption ISe vs MIX for 35 d and fed enough of a NTE/alfalfa/grain diet to achieve 0.57 kg BW gain/d. Within Se-form treatments, 2 steers were randomly assigned to each of 4, 2-acre NTE (ISe = 316 ± 31 kg, MIX = 315 ± 22 kg) or TE (ISe = 316 ± 37 kg, MIX = 314 ± 39 kg) paddocks for 84 d and had ad libitum access to their respective V-M. The MIXED procedure of SAS was used to assess effects of day, Se-form (ISe, MIX) and endophyte (NTE, TE) treatments, and their interactions. Whole blood Se decreased (P < 0.01) 31% from d 0 to 84 and was 6.2% greater (P < 0.01) for MIX steers. Serum prolactin decreased (P < 0.01) 18% for NTE and 48% for TE steers from d 0 to 84 and was 17% greater (P = 0.01) for MIX vs. ISe TE steers. Alkaline phosphatase activity (AP) decreased (P < 0.02) 27% from d 0 to 84 and was 15% greater (P < 0.02) for MIX steers. Serum urea nitrogen increased (P < 0.02) 8.2% from d 0 to 84 for TE but not NTE steers. Average daily gain (kg/d) was less (P < 0.01) in TE (-0.18) vs NTE (0.09) steers. We conclude that the ad libitum intake of MIX ameliorated the negative effects of consuming TE on serum prolactin and AP but not ADG.

scholarly journals Adopting a Mediterranean-Style Eating Pattern with Different Amounts of Lean Unprocessed Red Meat Does Not Influence Short-Term Subjective Personal Well-Being in Adults with Overweight or Obesity

2018 ◽  
Vol 148 (12) ◽  
pp. 1917-1923 ◽  
Author(s):  
Lauren E O'Connor ◽  
Sarah L Biberstine ◽  
Douglas Paddon-Jones ◽  
A J Schwichtenberg ◽  
Wayne W Campbell
Keyword(s):  
Quality Of Life ◽  
Well Being ◽  
Red Meat ◽  
Eating Patterns ◽  
Short Term ◽  
Eating Pattern ◽  
Meat Intake ◽  
Perceived Quality Of Life ◽  
Red Meat Intake

ABSTRACT Background Reducing red meat intake is commonly recommended. Limited observational studies suggest that healthy eating patterns with red meat are associated with improved quality of life. Objective The secondary objectives of this randomized crossover controlled-feeding trial were to assess the effects of following a Mediterranean-style eating pattern (Med-Pattern) with different amounts of red meat on indexes of personal well-being (i.e., perceived quality of life, mood, and sleep) in overweight or obese adults. We hypothesized that following a Med-Pattern would improve these outcomes, independent of red meat intake amount. Methods Forty-one participants [aged 46 ± 2 y; body mass index (kg/m2): 30.5 ± 0.6;n = 28 women,n = 13 men) were provided Med-Pattern foods for two 5-wk periods separated by 4 wk of self-selected eating. The Med-Red Pattern contained ∼500 g/wk (typical US intake), and the Med-Control Pattern contained ∼200 g/wk (commonly recommended intake in heart-healthy eating patterns) of lean, unprocessed beef or pork compensated with mainly poultry and dairy. Baseline and postintervention outcomes measured were perceived quality of life via the MOS 36-Item Short-Form Health Survey, version 2 (SF-36v2), daily mood states via the Profile of Mood States (POMS), sleep perceptions via the Pittsburgh Sleep Quality Index, and sleep patterns via actigraphy. Data were analyzed via a doubly repeated-measures ANOVA adjusted for age, sex, and body mass at each time point. Results Following a Med-Pattern did not change domains of physical health, mental health, total mood disturbances, sleep perceptions, and sleep patterns but improved subdomains of physical health role limitations (SF-36v2: 93.6–96.7%;P = 0.038), vitality (SF-36v2: 57.9–63.0%;P = 0.020), and fatigue (POMS: 2.9–2.5 arbitrary units;P = 0.039). There were no differences between the Med-Red and Med-Control Patterns (time × pattern,P-interaction > 0.05). Conclusion Following a Med-Pattern, independent of lean, unprocessed red meat intake, may not be an effective short-term strategy to meaningfully improve indexes of personal well-being in adults who are overweight or obese. This trial was registered atclinicaltrials.gov as NCT02573129.

178 Grazing Toxic Endophyte-infected Tall Fescue Alters Monocyte Abundance and White Blood Cell Expression of Prolactin and NF-kB Pathway Genes in Beef Steers

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 95-95
Author(s):  
Cecilia Winfrey ◽  
Merlin D Lindemann ◽  
James Matthews
Keyword(s):  
Tall Fescue ◽  
Sodium Selenite ◽  
Serum Prolactin ◽  
Experimental Unit ◽  
Beef Steers ◽  
Rt Pcr ◽  
Mrna Content ◽  
Ad Libitum ◽  
Ad Libitum Intake ◽  
Cell Expression

Abstract The hypotheses tested were that (a) summer-long (84 d) grazing of endophyte-infected tall fescue (TE) would alter the count of circulating leukocytes (WBC) and WBC expression of key prolactin and NF-kB pathway genes and (b) that ad libitum intake of an 1:1 blend (MIX) sodium selenite (ISe) and SELPLEX vs ISe in a vitamin-mineral mix (V-M, 27 ppm Se) would ameliorate negative TE effects. Sixteen TE-naïve beef steers depleted of Se were randomly assigned to ad libitum consumption of ISe vs MIX for 35 d. Within Se-form treatments, 2 steers (ISe = 316±37 kg, MIX = 314±39 kg) were randomly assigned to graze each of 4, 2-acre TE paddocks for 84 d and had ad libitum access to their respective V-M. Paddock was the experimental unit (n = 4). The MIXED procedure of SAS was used to assess effect of grazing TE (d 0 vs 84), Se-form (ISe vs MIX), and their interaction on clinical parameters WBC, and relative mRNA content (RT-PCR) in blood. Whole blood Se was 24% greater (P < 0.01) for MIX steers and decreased (P < 0.01) 34% by d 84. Serum prolactin decreased 88% by d 84 and was 98% greater (P < 0.01) for MIX steers on d 84. Monocytes decreased (P < 0.01) 47% with TE and were 67% lower (P = 0.04) in MIX steers. Grazing of TE altered mRNA content of CISH, STA5B, PPIB, AGAP2, and SPRLR; and IL-8, RELA, NFKBIA, TLR, IKBKG, ZAP70, and LCK; of the prolactin (P ≤ 0.05) and NF-kB (P ≤ 0.04) pathways, respectively. In contrast, Se form had no effect (P ≥ 0.07) on mRNA content. Summer-long consumption of TE by steers altered monocyte numbers and expression of prolactin and NF-kB genes, but ad libitum intake of MIX Se forms did not ameliorate these effects.

scholarly journals Development of a genetic evaluation for hair shedding in American Angus cattle to improve thermotolerance

2020 ◽  
Vol 52 (1) ◽  
Author(s):  
Harly J. Durbin ◽  
Duc Lu ◽  
Helen Yampara-Iquise ◽  
Stephen P. Miller ◽  
Jared E. Decker
Keyword(s):  
Heat Stress ◽  
Beef Cattle ◽  
Tall Fescue ◽  
The United States ◽  
Genetic Evaluation ◽  
Functional Enrichment ◽  
Fescue Toxicosis ◽  
Weaning Weight ◽  
Angus Cattle ◽  
Genetic Evaluations

Abstract Background 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. 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. 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. Both heat stress and fescue toxicosis reduce profitability partly via indirect maternal effects on calf weaning weight. 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). Results Hair shedding score was moderately heritable (h2 = 0.34 to 0.40), with different repeatability estimates between cattle grazing versus not grazing endophyte-infected tall fescue. 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. Together, these results indicate that economic gains can be made by using hair shedding score breeding values to select for heat-tolerant cattle. GWAA identified 176 variants significant at FDR < 0.05. 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. Conclusions This work contributes to a continuing trend in the development of genetic evaluations for environmental adaptation. 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.

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