Modeling Variation in Range Calf Growth Under Conditions of Environmental Uncertainty

Abstract

Functional relationships between calf weights and various managerial and environmental factors were developed using 19 years of performance data from 8 cow-calf herds at the Texas Experimental Ranch. Six models were developed to estimate weights at (1) the first weighing at approximately 75 days of age, (2) the second weighing at approximately 152 days of age, (3) the second weighing, using the first weight as a dependent variable, (4) weaning at approximately 237 days of age, (5) weaning, using the first weight as a dependent variable, and (6) weaning, using the second weight as a dependent variable. R2 values for the equations were .79, .83, .90, .84, .89, and .89, respectively. Equations were functions of the grazing treatment (heavy continuous vs. moderate continuous vs. rotational grazing), level of winter supplementation, age of calf at weighing, crossbreeding, linear and quadratic accumulated production year precipitation, and winter/spring temperatures. Performance of the equations was examined by stochastically simulating them for 360 iterations using 36 years of historical precipitation.