Calving rate was highest (0.9870.016; Po0.05) for cows that
grazed bermudagrass in the breeding season, and those grazing
endophyte-free fescue had a higher (P¼0.002) calving rate than
those grazing endophyte-infected tall fescue (0.9470.022 and
0.8570.033, respectively). Weaning rate means for cows grazing
bermudagrass and endophyte-free tall fescue did not differ
(0.9370.029 and 0.8870.029, respectively; P¼0.13); both were larger (Po0.05) than that for endophyte-infected tall fescue
(0.7870.037). No interaction of forage type with any breed type
effect parameterization was detected for either trait (P40.24). The
statistical adjustment for forage type did not substantially change
estimates of heterosis or direct effects for Romosinuano (the
maximum difference was 0.02), which might have been expected
if the toxins associated with endophyte-infected tall fescue augmented
the heterosis estimates. Brown et al. (2000) reported
heterosis for calving rate in Brahman–Angus that was 3 times
greater for cows grazing endophyte-infected tall fescue than for
cows grazing bermudagrass.