fescue, toxicity, cows


The objective was to test the effect of fescue cultivars and supplemental feeding of cows grazing fescue pastures on cow performance and pasture management. Primiparous and multiparous Angus-based crossed cows (n = 45) averaging 151 ± 7 d of gestation at turnout, were randomly allocated and stratified to pasture treatment by parity. Each pasture contained 3 cows of different ages, consisting of a young (first-calf heifer), middle-aged (3-5 yrs.), and old (≥ 6 yrs.) cow. Treatment was a 2 by 2 factorial design with two types of pasture (toxin producing or non-toxin producing fescue) and two levels of supplemental feeding (non-supplemented or supplemented at 1% of body weight on a DM basis of corn silage). Toxic fescue pastures consisted of K-31 endophyte infected tall fescue (n = 8) tested at 507 ppm ± 0.82 SEM for ergot alkaloids with a 92.5% infection rate. Non-toxic pastures consisted of novel (MaxQ) and endophyte free varieties (n = 7). Cows were fed silage (32-42% DM and 7.83% CP) daily in fence-line bunks, with feeding amount being adjusted at each weigh date. Cows were weighed on 2 consecutive days prior to turnout (middle of the second trimester), midpoint (beginning of the third trimester), and at about 2 weeks prior to the estimated calving date for herd. Body weight, body condition score, hair score, and rump fat measurements were taken at each weigh date. Supplementation tended (P = 0.07) to increase body weight gain and rump fat (P = 0.06) regardless of fescue type. Cattle grazing toxic fescue tended to have longer hair (P = 0.09) and did not “slick” off as quickly as those that were supplemented (P = 0.08). Cattle grazing toxic fescue exhibited classic fescue toxicosis symptoms, and supplementation improved cow performance regardless of fescue cultivar.

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