Date of Award


Document Type


Degree Name

Master of Science (MS)

Legacy Department

Plant and Environmental Science


Andrae, John G

Committee Member

Duckett , Susan K

Committee Member

Pratt , Scott L


Research was conducted to determine the effect of tall fescue and alternative management regimens on reproduction in replacement beef heifers. Angus _ Simmental heifers (n = 48; 318 ± 4.99 kg initial BW) stratified by weight and pubertal status were assigned to one of three replicated grazing treatments: (1) toxic endophyte-infected tall fescue (TF); (2) toxic endophyte-infected tall fescue with a soybean oil supplement (TFO); or (3) mixed winter annual species (cereal rye, annual ryegrass, crimson clover and hybrid turnip) (M). Tall fescue endophyte infection level was between 74 and 94%. Pastures were grazed from December 12 to April 24. Oil was supplemented once daily at a rate of 1 g/kg BW with a soy hull (4 g/kg BW) carrier. Heifers grazing M had higher ADG than TFO which was higher than TF (P < 0.01). Total standing heats and mounts per standing heat did not differ among treatments (P = 0.89 and P = 0.21). Conception rate did not differ among treatments. Serum cholesterol (P < 0.01) and total fatty acids (P < 0.01) were greater in TFO than in TF and M heifers. Serum concentrations of 16:0, 18:0, 18:1, 18:2 and 20:4 were greater in TFO heifers than in the TF and M treatments (P < 0.01) whereas 18:3 concentration was greatest in the M heifers (P < 0.01). While diet affected gain, prolactin, serum fatty acid and cholesterol concentrations, no differences were observed in heifer estrus measures or conception rates.

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