The experiment was carried out to evaluate the development of beef heifers from 15 to 28 months of age, maintained on natural pasture under different herbage allowance (HA) managements. The treatments were fixed HA of 4, 8, 12 and 16% of the body weight (BW) over the year, and variable HA of 8-12%; 12-8%; and 16-12%, where the first value corresponded to the HA used in the spring and the second one to that used in the remainder of the year. Crossbreed beef heifers were used under continuous stocking with variable stocking rate, and the body weight, body condition score (BCS), average daily gain (ADG) and reproductive ability by blood progesterone concentration were evaluated. In addition, herbage mass, sward height, and effectively grazed area were evaluated to characterize the pasture. At 4%-HA the animals presented great decrease in weight at the end of summer and fall, and this HA removed from the experiment. Differences among HA were not verified among treatments for LW, BCS, and ADG. At 26 months of age, no difference for heifers estrus probability (EP) was detected, although HA of 16-12% showed EP of 50%. At 28 months of age, the HA 16-12% HA showed greater EP (86%) and was not different from the HA of 16% (50%) and 8-12% (50%). Such management strategies promoted a sward structure that was more adequate, or less limited, to heifer grazing.
progesterone; reproductive aptitude; stocking management; sward structure
