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Journal of Animal Science, Vol 71, Issue 3 757-764, Copyright © 1993 by American Society of Animal Science

JOURNAL ARTICLE

Growth and endocrine responses of cattle to implantation of estradiol-17 beta during continuous or discontinuous grazing of high- and low-endophyte-infected tall fescue

G. M. Davenport, J. A. Boling and C. H. Rahe
Department of Animal and Dairy Sciences, Alabama Agricultural Experiment Station, Auburn University 36849-5415.

Forty-eight Angus x Hereford steers (initial BW = 336 +/- 8.3 kg) were used in a 56-d study to evaluate growth and endocrine responses to continuous or discontinuous grazing of high-endophyte-infected Kentucky-31 (K; > 57% infestation rate) or low-endophyte-infected Johnstone tall fescue (J; < 1% infestation rate) and implantation with 0 or 24 mg/steer of estradiol-17 beta (E2; Compudose). Steers were allotted by weight to eight 3-ha paddocks (four paddocks of each fescue variety) with six steers per paddock. Two paddocks of each variety were grazed continuously (KK and JJ), whereas steers on the remaining four paddocks were rotated every 14 d from K to J (KJ) or from J to K (JK). Three steers in each paddock were implanted with E2 on d 0. The study extended from May 25, 1988 to July 20, 1988 with steers exposed to potential heat-stress conditions for 52 d of the 56-d study. Body weights were obtained on d 0, 28, and 56, and blood samples were taken on d 28 and 56. Overall ADG, serum prolactin, and serum alkaline phosphatase activity were greater (P < .05) in JJ than in KK steers. Rotation from K to J did not increase overall ADG, prolactin, insulin-like growth factor I (IGF-I), or alkaline phosphatase activity compared with the continuously grazed KK, whereas JK steers had lower (P < .10) ADG, prolactin, and alkaline phosphatase activity than JJ steers. Estradiol-17 beta increased (P < .10) IGF-I in JJ, KJ, and JK steers but not in KK steers.(ABSTRACT TRUNCATED AT 250 WORDS)


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R. Browning Jr.
Effects of endophyte-infected tall fescue on indicators of thermal status and growth in Hereford and Senepol steers
J Anim Sci, February 1, 2004; 82(2): 634 - 643.
[Abstract] [Full Text] [PDF]


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Copyright © 1993 by the American Society of Animal Science.