Effects of feeding XXXX on lamb performance in a heat stress environment.

@entity742 @entity894 @entity18960 @entity18959 @entity1017 @entity8956
@entity742 exposed to a heat-stressed environment (33 degrees C, 50% relative humidity) were used in three experiments to determine whether @entity18960 (EV) is the primary toxin involved in fescue @entity8956 . The first study evaluated the effects of feeding diets containing increasing levels of endophyte-infected @entity18959 seed (E+) and decreasing levels of endophyte-free @entity18959 seed (E-). The second and third study evaluated the response to a diet that contained synthetic EV added to an E- diet and the response to a diet containing endophyte-infected ryegrass seed (R+) with an elevated concentration of EV. In Exp. 1, @entity742 were fed diets of: 1) 10% E- and 0% E+, 2) 5% E- and 5% E+, or 3) 0% E- and 10% E+. Increasing the percentage of E+ in the diet resulted in a linear decrease (P < 0.01) in feed intake (as-fed basis), skin temperature, @entity894 ( @entity894 ), and serum prolactin. Body @entity1017 also decreased (P < 0.06). Respiratory rate and core body temperature were not affected by the 5 or 10% E+ diets. In Exp. 2, @entity742 were fed diets that contained: 1) 10% E-, 2) 10% E- with synthetic EV added at a level equivalent to the 10% E+ diet, or 3) 10% E+. Feed intake (as-fed basis), body @entity1017 , and skin temperature did not differ for @entity742 fed the E- and EV diets. The EV diet elicited a decrease (P < 0.05) in @entity894 and prolactin compared with the E- diet. The @entity894 for @entity742 fed EV did not differ (P > 0.10) from the E+ lambs; however, serum prolactin was lower (P < 0.05) for @entity742 on the E+ diet than for those fed EV. Core body temperature was not affected (P > 0.10) by feeding EV or E+ fescue seed in Exp. 2. In Exp. 3, @entity742 were fed diets that contained: 1) 10% E-, 2) 3.24% R+ and 6.76% E-, which added an equivalent amount of EV to E+ diets but reduced concentrations of other ergot alkaloids, or 3) 10% E+. @entity742 fed the E+ diet and maintained at 33 degrees C had lowered feed intake (as-fed basis), skin temperature, and @entity894 compared with @entity742 fed the E- or R+ diets (P < 0.05). @entity742 fed the E+ diet had increased rectal temperatures and lowered serum prolactin compared with @entity742 on the R+ diet (P < 0.05). @entity742 on the R+ diet had a greater rectal temperature and lower serum prolactin than @entity742 on the E- diet (P < 0.05). These results suggest that EV is a fescue toxin; however, other alkaloids might work synergistically with EV, causing the full expression of fescue @entity8956 .
