摘要：We estimate the weight gain for range calves as a polynomial function of calf ageaccounting for weather, sex, lagged calf weights relative to the growth function, andcompensatory gains. Birth weights plus single day weighings that occurred around 3, 8,12, and 20 months of age are the data used to estimate our growth function. This functionis then used to determine the economic trade-off between herd size and calf sale weights,for both spring and fall sale dates. In addition, we evaluate the profitability of feedingsupplement by increasing the rate of gain associated with our growth function whenforage and nutrients are limiting for the two grazing environments of Southeast andCentral Arizona. Using prices from 1980 to 1998, results indicate that the most profitableherd mix, sale date, and feeding protocol is 450 lb. calf sales with no supplementalfeeding and sales occurring in May for both regions. Although, feeding supplement wasnot associated with the most profitable outcome, supplement increased the average returnby $45 to $70 per AUY for sale weights of 550, 650, and 750 lbs.
关键词：animal unit year; growth function; sale weight; supplement
