Consumption of Endophyte Infected Fescue During Gestation in Beef Cows

Tall fescue is a widely grown, cool season grass prevalent in the eastern United States that is known for its resistance to abiotic and biotic stresses. A main reason for tall fescue's resistance to these stresses is attributed to the presence of a fungal endophyte. Unfortunately, this endophyte also adversely affects cattle production. Cows consuming the ergot alkaloids produced by these endophytes can exhibit decreased feed intake, growth performance, organ vasoconstriction, and increased rectal temperature. This work is interested in examining how endophyte toxin exposure impacts pregnancy in cattle. Reduced blood flow to the fetus and inadequate maternal nutrition contributes to intra uterine growth restriction (IUGR), and this work proposed that fescue endophyte toxicity affects the gestating cow and fetus. Three studies were completed.

In experiment 1, gestating cows grazed high or low endophyte fescue pastures during late gestation to determine if exposure to ergot alkaloids in utero results in IUGR and if calves from these pregnancies have altered growth performance. Creep feeding was evaluated as a mitigation strategy for impaired calf growth due to fescue toxicity, and feedlot performance was evaluated to determine if consuming fescue during gestation and creep feeding would affect feedlot performance. Calf BW was different (P < 0.01) by treatment x time. Birth weights of calves were similar , prior to creep feeding calves exposed to high endophyte fescue were lower, and post-supplementation creep fed calves had increased BW. Days on feed and dressing percentage were decreased in the supplemented group, and marbling score was decreased for both the supplemented and unsupplemented groups following the completion of the feedlot phase (P < 0.05). The second study was setup similar to study one, however cows were exposed to fescue pastures from d 170 of gestation until calving. Calf birth weights did not differ, but weights were increased in the supplemented group post creep feeding (P < 0.05). Average daily gains (ADG) of supplemented calves were greater during the supplementation period (P < 0.01). In the third study, indwelling vaginal temperature probes were used to evaluate differences in body temperature of cows fed fescue seed with high or low levels of ergot alkaloids during early gestation, and in varying environmental conditions. In the winter trial, body temperature was measured hourly from days 0-14 of gestation. In the summer trial, body temperature was measured hourly from days 0-32 of gestation. Body temperatures were different (P < 0.01) between treatments during both trials.