Reproductive performance and lamb weight gains for ewes grazing fungus-infected tall fescue.
Bond J. | Lynch G.P. | Bolt D.J. | Hawk H.W. | Jackson C. Jr. | Wall R.J.
Four studies were conducted to determine specific physiological effects of grazing fungus-infected tall fescue or hay made from such pastures on growth and reproductive performance of ewes as well as growth of their lambs. In study 1, 36 and in study 2, 46 crossbred ewes were alloted to six .5 ha paddocks: two contained infected (G1-307) and two non-infected (KY31) tall fescue with the other two of orchardgrass (OG). In study 3, 116 ewes were assigned to 5 paddocks each of G1-307, KY31, and OG. To access fertilization rate, one or two ewes from each paddock were necropsied 3 d after mating and ova examined for cleavage. In study 4, 80 ewes were assigned to one of four paddocks of G1-307 or one of four paddocks of OG. Body weights and jugular blood samples were obtained biweekly. In studies 1, 2, and 3, serum samples were used for a metabolic profile analysis. In studies 3 and 4, plasma was measured by radioimmunoassay for prolactin (PRL) and progesterone (P4). P4 was used to determine ovarian activity. Ewe body weight gains did not differ (P greater than .05) among treatments in any of four studies. Serum cholesterol and plasma PRL were lower in ewes grazing G1-307 than in the ewes grazing the other grasses. Conception was delayed in ewes fed G1-307 compared to the other ewes in all studies except 4. In study 3, delayed conception appeared to be due mostly to embryonic deaths and some to a later onset of estrous activity. Ewe gestation length, average number of lambs born, lamb birth weight and lamb survival and gain to weaning were not affected by treatments.
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