Estrous behavior was determined in

Estrous behavior was determined in nonpregnant, nonlactating Angus and Angus × Hereford (n = 32)
cows that were 4.1 ± 1.4 yr of age, had BW of 541 ± 5 kg, and had a BCS of 5.8 ± 0.8 (1 = emaciated, 9 = obese; Wagner et al., 1988), in 2 replicates; replicate 1 in January and February, and replicate 2 in July and August in Oklahoma. At the beginning of each replicate, cows were stratified by BCS and age and were randomly allotted to a 60 × 100 m drylot or a 12-ha pasture to evaluate the effect of animal density on estrous behavior. There were 16 cows in each confinement area during each replication. Six cows from replicate 1 did not respond to synchronization in replicate 2 and were replaced with cows of similar age, BW, and BCS. The pasture group grazed little bluestem (Andropogon scoparius) and big bluestem (Andropogon gerardii). Both groups were fed 38% CP supplement and prairie hay as needed to maintain BCS ≥5.0. The drylot had a 2.7 × 10.0 m artificial shade and wind break. The pasture group had adequate trees for shade and protection from wind. The drylot had an automatic water fountain,
and the pasture had a metal tank for water.