123 Effect of a hydrolyzed yeast product on cow behavior, body eeight, body condition score, and hair coat score in cows grazing pastures containing endophyte-infected tall fescue

Abstract

Abstract The objective of this study was to determine if the addition of a hydrolyzed yeast product would alleviate the symptoms of fescue toxicosis in beef cattle. Thirty-eight Angus cow-calf pairs were stratified by cow age and body weight then randomly allotted to one of two treatments; control mineral (CON) or hydrolyzed yeast mineral (HYM). Cattle in both groups were allowed access to mineral for 126 d while they grazed the same eight pastures (1.21 ha each) in a rotational pattern. Mineral was provided at a target rate of 113.4 g·hd-1·d-1 every 28 d. Each pasture was grazed by cattle groups for 7 d. Mixed grass pastures containing tall fescue were utilized and evaluated for endophyte level prior to the start of the project. Due to pasture endophyte level variability (44%-73% endophyte), both groups of cattle rotationally grazed each pasture at least 2 times starting in June. Prior to entering a new pasture weekly, cows were weighed and assigned a BCS and hair coat score (HC) by two independent, trained personnel. Cow behavior was measured every 15-min within a 2-h block weekly. Percentage of cows active or inactive, outside or inside was recorded. Data were analyzed using the MIXED procedure of SAS. Cow BW change was unaffected by treatment (P > 0.23). Cow BCS significantly increased in HYM vs. CON cows (0.4 vs. 0.1; P = 0.02; SEM = 0.1) through the 126 d project. No treatment effect was observed on HC (P > 0.19). Cow behavior was impacted by treatment, as HYM cows spent more time outside compared to CON cows (P < 0.01). Results of this trial suggest that HYM cows may have experienced less heat stress as a result of fescue toxicosis as they were willing to spend more time outside and increased BCS.