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

Abstract

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)

Growth and subsequent feedlot performance of estradiol-implanted vs nonimplanted steers grazing fall-accumulated endophyte-infested or low-endophyte tall fescue

“…Nonetheless, ADG of implanted steers grazing HE KY-31 were 14% less than ADG of nonimplanted steers grazing LE KY-31, suggesting that use of estradiol 17-p was at best a partially effective means of minimizing fescue toxicosis. These data are in agreement with those of Davenport et al (1993).…”

“…High ambient temperature and humidity can exacerbate fescue toxicosis (Hemken et al, 1981); therefore, fescue toxicosis might not be as severe when fescue is grazed as stockpiled forage during the fall and early winter months or by feeding ensiled vegetative regrowth during the colder winter months. Limited information (Brazle and Coffey 1991;Davenport et al, 1993) suggests that the growth-decreasing effects of fescue toxicosis can be partly alleviated by implantation with anabolic agents. Objectives of this research were 1) to evaluate effects of an estradiol 17-0 implant on performance of steers grazing fall-accumulated endophyte-infested and low-endophyte ( LE) fescue cultivars, 2 ) to compare performance of steers subsequently fed either endophyte-infested or LE haylage, and 3 ) to evaluate feedlot performance for carryover effects associated with previous consumption of endophyte-infested fescue.…”

Summer-Long Grazing of High vs. Low Endophyte (Neotyphodium coenophialum)-Infected Tall Fescue by Growing Beef Steers Results in Distinct Temporal Blood Analyte Response Patterns, with Poor Correlation to Serum Prolactin Levels

“…However, only prolactin, albumin, and cholesterol were consistently affected in each of the three periods. Decreased serum prolactin is the most consistently observed, and accepted, indicator of cattle suffering from fescue toxicosis ( 2 , 8 , 17 , 18 ). The accompanying decreased serum cholesterol also is consistent with that found by others for cattle suffering from fescue toxicosis and is thought to be caused by elevated body temperatures ( 19 – 21 ).…”

Forms of selenium in vitamin–mineral mixes differentially affect the expression of genes responsible for prolactin, ACTH, and α-MSH synthesis and mitochondrial dysfunction in pituitaries of steers grazing endophyte-infected tall fescue1

“…Fescue toxicosis results from consumption of ergot alkaloids found in Epichloe coenophialum-infected tall fescue (Lolium arundinaceum) pastures and is a clinical condition consisting of impaired metabolic, vascular, growth, and reproductive processes in cattle (Strickland et al, 2011). Reduced serum prolactin is a recognized marker of fescue toxicosis (Goetsch et al, 1987;Davenport et al, 1993). Selenium-poor soils in this same geographic region result in Se-deficient forages necessitating the need to provide supplemental Se (Dargatz and Ross, 1996).…”