Using tall fescue in a complementary grazing program for spring calving beef cows in southern Arkansas

Authors: BECK, PAUL - University Of Arkansas; STEWART, C. - University Of Arkansas; GRAY, H. - University Of Arkansas; GADBERRY, M. - University Of Arkansas; Gunter, Stacey; YOUNG, C. - Samuel Roberts Noble Foundation, Inc; HOPKINS, A. - Samuel Roberts Noble Foundation, Inc

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2014
Publication Date: 7/1/2014
Publication URL: http://handle.nal.usda.gov/10113/59410
Citation: Beck, P., Stewart, C.B., Gray, H.C., Gadberry, M.S., Gunter, S.A., Young, C., Hopkins, A.A. 2014. Using tall fescue in a complementary grazing program for spring calving beef cows in southern Arkansas. Professional Animal Scientist. 30:423-431.

Interpretive Summary: Research has shown that adding clovers to endophyte-infected tall fescue pastures improves the performance of grazing cattle compared to pure stands of endophyte-infected tall fescue. Research to alleviate the negative affects of fungal endophytes in tall fescues have resulted in the selection on funguses that don’t produce the toxic alkaloids like the endemic endophytes. These novel-endophytes have been widely adopted by livestock producers using tall fescue for pastures because of the improved performance displayed by grazing livestock. As a result of the change in the type of endophytes now used in new varieties of tall fescues, a new question is posed: is the addition of clovers to an old pasture as effective as replacing the entire pasture with a new variety of tall fescue infected with non-toxic endophyte? A 3-year experiment was conducted in southern Arkansas to answer this question. Cows grazed pastures of tall fescue with either toxic or non-toxic endophytes. Also, half of the pastures with toxic endophyte were interseeded with white, red, and crimson clovers. Over the 3-year period, cow body weight did not differ among the pasture types, but at calving the cows tended to be fatter for toxic endophyte pastures with or without clovers than non-toxic pastures. Again at weaning, cows grazing non-toxic pastures had less fat cover than cows on toxic pastures. However, pregnancy rate was 29% greater for cows on non-toxic pastures than the toxic endophyte pastures with or without clovers. Calf body weight at pre-breeding and weaning was not affected by endophyte type or clover additions. But, because of the difference seen in pregnancy rate, weaning weight per cow exposed to bulls was greater for non-toxic pastures than toxic endophyte pastures with or without clovers. Hence, non-toxic endophytes did not improve calf performance or cow body weight at weaning compared with toxic endophyte pastures with or without clovers, but improvements in pregnancy rates lead to increased calf body weight at weaning per cow, an important indicator of profitability.

Technical Abstract: The objective of this experiment was to determine the effect of endophyte toxicity in clover additions to tall fescue pastures used as a limit-grazed complement to warm-season grass pastures. Over 3 years, beef cows (n = 108, Year 1; n = 72, Year 2 and 3; initial fall body weight = 480 ± 8.6 kg, body condition score = 5.5 ± 0.07; age = 6 ± 2.6 years) grazed 6 warm-season grass pastures (4.8 ha) in the summer and fall and were fed warm-season grass hay and limit-grazed tall fescue (festuca arundicea) pastures (2.4 ha) during the winter and spring. Limit-grazed pastures were: non-toxic endophyte tall fescue (NETF) or toxic endophyte tall fescue (TETF) or the same pastures established with clovers [(TECL) white, red, and crimson clovers]. Although cow body weight did not differ among treatments throughout the experiment, body condition score at calving tended to be less for NETF than TETF and TECL, but was significantly greater for NETF than TETF and TECL in April before breeding and TEF tended to have greater body condition score than TECL. At weaning in October, body condition score of NETF was significantly less than TETF and TECL. Pregnancy percentage was 18 percentage units greater for NETF than the average of TETF and TECL. Further, pregnancy percentage was also 16 percentage units greater for TETF than TECL. Calf BW at birth, pre-breeding in April, and at weaning in October was not significantly affected by treatment, but weaning body weight per cow exposed to a bull was greater for NETF than TETF and TECL. The results of this experiment indicate that although NETF did not improve calf performance or body weight at weaning compared with TETF or TECL, improvements in breeding rates lead to increased calf body weight at weaning per cow exposed to a bull, an important profitability indicator. Including clovers in TETF pastures did not improve calf performance or breeding rates compared with TETF.