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Evaluation of a Model of Beef Cattle Growth and Composition

University of California^,3, Davis 95616

Abstract

A dynamic computer model of beef cattle growth based on fundamental biological concepts was evaluated with regard to body composition, frame size and type. The model was used to simulate body weight and composition of steers varying in condition and energy intake. In general, as total energy intake increases, fat composition of steers of a given body weight increases. Body composition is nearly similar at a given body weight for animals fed different quantities of diets of high energy concentration; at lower diet energy concentrations, animals with restricted feed intake are less fat at a given body weight than ad libitum-fed animals. Fatter animals fed a high energy diet ad libitum remain fatter throughout subsequent growth, although with compensatory growth, composition of thin animals approaches that of fatter animals at greater body weights. The body weight where the two become similar is greater if the animals were initially larger or more different in composition. At usual slaughter weights, small- and average-frame steers have similar composition for most nutritional regimens. Larger-frame steers fed lower energy diets are significantly leaner than those fed high concentrate diets. When predicted performance of steers of various types was compared with actual data, no systematic error of prediction with frame size was observed for empty body protein, fat or weight. However, fat content of certain breeds was overpredicted, apparently due to increased maintenance requirements. When compared with three commonly used prediction systems, the model's body weight estimates were less biased and Standard errors of prediction were as good or better for both data used in model development and independent data sets. In particular, frame size effects were best accounted for by the model. This demonstrates that a model based on fundamental biological concepts can be aggregated to the whole animal level and possess greater predictive accuracy and wider application than empirically derived models such as those currently available and in use.

¹ Current address is Dept. of Anim. Sci., Univ. of Oklahoma, Stillwater.

² Please address all correspondence to R. L. Baldwin.

³ Dept. of Anim. Sci.

This article has been cited by other articles:

				C. L. Ferrell and J. W. Oltjen ASAS CENTENNIAL PAPER: Net energy systems for beef cattle--Concepts, application, and future models J Anim Sci, October 1, 2008; 86(10): 2779 - 2794. [Abstract] [Full Text] [PDF]