Ingestive behavior and performance of female lambs under grazing

The ingestive behavior and performance of female lambs grazing on Marandu pasture submitted to different stocking rates during the rainy and transition season were evaluated. The experimental area with 4.500 m2 was divided into 45 paddocks of 100 m2 each. Twenty-seven Santa Ines female lambs (purebred) 4 months old and 22 kg of initial body weight were distributed in a completely randomized design, with nine replicates. Lambs were divided into 9 groups with the same initial weight and submitted to three stocking rates: 2, 3 and 4 lambs/paddock, which corresponded to 40, 60 and 80 lambs/ha, respectively. Each group of animals had a module of five paddocks, managed on intermittent grazing system, with 7 days of occupation and 28 d of rest. The feeding behavior of animals was assessed one day before the end of each experimental period, from 8:00 AM to 5:00 PM, observing the activities of grazing, rumination, rest and water or mineral intake at every 15 minutes. Only activity happening in the moment of observation was considered. The liveweight gain of animals was calculated by the difference between weighing dates. The average daily gain was obtained dividing the WG by the total of the experimental period days. Weight gain per area was calculated by multiplying the number of animals per hectare in each stoking rate and their respective weight gain. Increase on time of grazing and reduction on time of ruminating and resting were observed as stocking rates increased. As the activities of behavior are mutually exclusive, animals of the stocking rates of 60 and 80 animals / ha showed lower rumination and resting times when compared with the lower stocking rate. Thus, animals in the stocking rates of about 80 to 60, showed 41% reduction in resting time. We observed the existence of a negative linear effect for average daily gain. Lambs at stocking rates of 40, 60 and 80 lambs / ha had gains of 90, 67.64 and 45.62 grams per day, respectively. This is mainly due to the reduction in herbage mass and total mass of green leaf blade, caused by increasing the number of animals per paddock. It is noteworthy that the lowest daily earnings are also related to higher grazing time. The largest gain occurred in the area with 60 lambs / ha, 3.8 kg / ha / day. For the lowest and highest stocking rates, the gains for the respective areas were 3.58 and 3.45 kg / ha / day. Even with a higher number of lambs / ha, the highest stocking rate did not result in higher gain per unit area, probably due to the effect of lower gain (45.62 g / day) for the group.