Growth rate, diet digestibility, and serum proclactin of yearling horses fed non-infected and infected tall fescue hay

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To determine to effect of feeding tall fescue hay infected with endophyte on growth rate, diet digestibility, and serum prolactin, 17 Quarter Horse yearlings were fed a diet of 60% concentrate and 40% tall fescue hay for 5 months. Diets were formulated to meet 1989 NRC recommendations for moderate growth. The dietary treatments included either non-infected (E-, n=9) or infected (E+, n=8) tall fescue hay. Field sampling determined a 52% infection rate of the E+ hay with the endophyte Acremonium coenophialum. Initially and at 29-day intervals, yearlings were weighed and measured for skeletal growth including: (1) height at the withers, (2) length of bone between knee and fetlock, (3) length of bone between hock and fetlock, and (4) the circumference of fore and rear cannon bones. Total fecal collection from the 10 geldings during the last month of the trial permitted the calculation of diet digestibility. Serum samples were taken throughout the trial to determine prolactin response to dietary treatments. The E+ fescue hay did not affect (P〉.05) growth rate of yearling horses. Yearlings gained .40 and .38 kg/d when consuming the E− and E+ based diets, respectively. Geldings gained more (P<.05) than fillies. Changes in height at the wither and length and circumference of the fore and rear cannon were positive but did not differ between hay treatments or sexes. E+ fescue hay diets tended to be lower in dry matter, apparent energy, and crude protein digestibility, but values were not statistically different. Fiber digestibility was lower (P<.01) for the diet based on E+ hay. Neutral detergent fiber digestibility averaged 66.2 and 54.4% for E− and E+ diets, respectively.Acid detergent fiber digestibility averaged 78.9 and 64.5% for E− and E+ diets, respectively. Although fiber digestibility of E+ tall fescue hay was lower than E-hay, grain supplementation supportive of a moderate growth rate produced equal growth among yearling horses. Also, no differences in prolactin were apparent between the yearlings fed E− and E+ tall fescue hay. © 1992, William E. Jones. All Rights Reserved.. All rights reserved.

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Journal of Equine Veterinary Science

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