Reproductive effects of E+ tall fescue ingestion on beef bulls have not been studied extensively. Beef cattle herds in the southeastern United States that depend on E+ tall fescue as the predominant forage tend to be small herds averaging about 25 cows. These herds are usually one-bull operations, and the risk of reproductive failure is great if the bull is affected adversely by grazing E+ tall fescue. Limited research has been conducted on the effects of N. coenophialum on herd sires. Schuenemann et al. (2005a) fed ergotamine tartrate to bulls to simulate the effect of the ergots found in E+ tall fescue. Bulls consuming ergotamine tartrate exhibited signs of toxicosis, as reflected by reduced animal performance and increased rectal temperatures. Semen collected from ergotamine tartrate-fed bulls was compared with semen collected from control animals. Cleavage rates of embryos derived from in vitro fertilization with semen from bulls fed ergotamine tartrate were reduced compared to the control. However, the development of cleaved embryos to blastocysts did not differ between control and ergotamine treatments. These findings indicate that bulls exposed to ergot alkaloids appear to have reduced fertilization potential.

Schuenemann et al. (2005b) reported on the development of oocytes fertilized in vitro with semen from bulls grazing KY-31 E+ or ‘Jesup' tall fescue containing MaxQ. Semen collected from bulls did not differ between treatments in mobility or morphology at time of collection and at in vitro fertilization. However, embryos resulting from semen from bulls grazing E+ tall fescue had reduced cleavage rates compared to bulls grazing MaxQ tall fescue. Development of cleaved embryos to 8-cell and blastocyst stages did not differ between treatments. Reduced cleavage rates may lower reproductive performance of bulls due to reduced fertilization potential. Based on the ergotamine tartrate and the grazing trials, the reproductive problems in beef bulls appear to be related to ability of the semen to fertilize the oocyte rather than to further embryo development. Vasoconstriction effects were evident in bulls consuming E+ tall fescue; they had reduced scrotal temperature compared to bulls grazing MaxQ tall fescue in early May and late June (Schuenemann et al., 2005b). Blood serum prolactin levels, which are greatly depressed in cows and steers, did not seem to be affected in bulls consuming E+ tall fescue pasture (Schrick et al., 2003).


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