Cow-Calf Response to Stocking Rates, Grazing Systems, and Winter Supplementation at the Texas Experimental Ranch

Abstract

Cow-calf performance from 1960 through 1978 was contrasted between three grazing treatments at the Texas Experimental Ranch. Grazing treatments were yearlong continuous stocked at annual rates averaging 5.1 and 7.6 ha/ cow and a 4-pasture, 3-herd deferred rotation system stocked at an annual rate averaging 7.2 ha/cow. Averaged across three weighing periods, cows in the deferred rotation treatment averaged 447 kg while weight of cows in the heavily and moderately stocked continuous treatmentsaveraged 427 and 438 kg, respectively. Calf weaning weights averaged 204,212, and 217 kg for the heavy continuous, moderate continuous, and Merrill rotation treatments, respectively. Production/cow averaged 182,189, and 202 kg while production/ha averaged 35.9, 25.2, and 27.8 kg, respectively, for the heavy continuous, moderate continuous, and deferred rotation treatments. Cows fed winter supplement were significantly heavier in early spring and summer than nonsupplemented cows with no sign&ant differences in weights by late summer. Supplemented cows weaned calves averaging 214 kg as compared to 208 kg for calves weaned from nonsupplemented cows. Winter supplementation significantly increased production in the heavily stocked treatment but not in either of the moderately stocked treatments. Numerous statistically significant interactions accompanied the significant main effects, and the biological significance of each was examined. The Texas Experimental Ranch was created in 19S9 to provide researchers with the necessary facilities to evaluate the longterm responses of both livestock and vegetation to various grazing systems and rates of stocking. Kothmann et al. (1970, 1971) concluded from a thorough analysis of the cow-calf performance data collected at the ranch from 1961 through 1968 that no economic advantages were apparent from either yearlong continuous grazing at a light rate of stocking (I 1.5 ha/ AU) or from a 2-pasture, l-herd deferred rotation system (Joubert 1958) stocked at a moderate rate (8.4 ha/ AU) when contrasted to continuous grazing and a 4-pasture, 3-herd deferred rotation system (Merrill 1954) stocked at a moderate rate (8.0 ha/AU). In addition, it was concluded that feeding cottonseed meal (41% CP) as a winter supplement at a rate exceeding 0.68 kg/day was not economically justifiable in any of the grazing treatments. Thus, in 1969 only three grazing treatments that had been initiated in 1960 were continued. These treatments were yearlong continuous grazing at moderate and heavy rates of stocking and the 4-pasture, 3-herd deferred rotation system.