Growth and ovarian function of weanling and yearling beef heifers grazing endophyte-infected tall fescue pastures

BOARD-INVITED REVIEW: St. Anthony's Fire in livestock: Causes, mechanisms, and potential solutions1,2

“…Further, the extent of this reduction in reproductive performance in ruminants consuming ergot alkaloid-contaminated diets has not been consistent. Modest to severe reductions (7.6 to 39.2% decreases) in pregnancy rates of cows consuming endophyte-infested tall fescue have been reported Brown et al, 1992), whereas others failed to observe diminished conception and pregnancy rates in cows (Bnrke et al, 2001a,b) and heifers (Mahmood et al, 1994;Rorie et al, 1998). Obviously, an interactive relationship exists among several factors (e.g., ambient temperature, genetics, animal age, amonnt and length of exposure time, and nutritional management) with consumption of ergot alkaloids and reproductive dysfunction in ruminants.…”

“…Serum progesterone concentrations have been reported reduced in horses (Monroe et al, 1988), ewes (Burke et al, 2006a), and heifers fed endophyte-infested tall fescue or ergotamine tartrate (Jones et al, 2003;Seals et al, 2005). Mahmood et al (1994) suggested age of the animal may exacerbate ergot alkaloid effects on progesterone. Weaned heifers had reduced concentrations of progesterone when grazing endophyte-infested tall fescue, whereas yearling heifers were not as sensitive to the effects of ergot alkaloid-exposure (Mahmood et al, 1994).…”

“…Mahmood et al (1994) suggested age of the animal may exacerbate ergot alkaloid effects on progesterone. Weaned heifers had reduced concentrations of progesterone when grazing endophyte-infested tall fescue, whereas yearling heifers were not as sensitive to the effects of ergot alkaloid-exposure (Mahmood et al, 1994). There are several possible mechanisms that may be involved in reduced concentrations of progesterone.…”

Growth and reproductive performance of beef heifers grazing endophyte-free, endophyte-infected and novel endophyte-infected tall fescue

“…However, consumption of endophyte-infected fescue has been associated with reduced performance (Hoveland, 1993) and reproduction (Porter and Thompson, 1992) due to the production of ergot alkaloids by the endophyte. Reproductive effects in cattle have been reported to include: delayed puberty (Washburn and Green, 1991), lowered pregnancy rate (Schmidt et al, 1986;Gay et al, 1988) and impaired corpus luteum function (Ahmed et al, 1990;Estienne et al, 1990;Mahmood et al, 1994). It appears that elevated ambient temperature exacerbates the negative effects of ergot alkaloids and may be a key factor in the development of fescue toxicosis (Hemken et al, 1981;Aldrich et al, 1993;Burke et al, 2001a,b).…”

Effects of body condition on measures of intramuscular and rump fat, endocrine factors, and calving rate of beef cows grazing common bermudagrass or endophyte-infected tall fescue1,2

“…Cows in thin BC during the prepartum period and at parturition have an extended postpartum anestrous period and may not become pregnant during the breeding season (Selk et al, 1988;Hess et al, 2005). Modest to severe reductions (7.6 to 39.2% decrease) in pregnancy rates of cows consuming EI diets have been reported Brown et al, 1992), whereas others failed to observe diminished conception and pregnancy rates in cows (Watson et al, 2004) and heifers (Mahmood et al, 1994) consuming EI.…”