Abstract:
Proc. Aust, Soc. Anim. Prod. Vol. 18 PREDICTION OF LIVEWEIGHT CHANGE IN PERFORMANCE TESTED CATTLE D.M. MURRAY*, P. MADSEN** and B. Bech ANDERSEN** Performance testing depends on accurate assessment of live weight at the start and finish of the test period. Such accuracy is difficult to obtain, however, due to variation in gut 'fill? An alternative method to determine these weights by prediction has been studied. This was done by fitting a cubic polynomial growth model to recorded cattle weights at 210, 238, 266, 294, 322, 350, 378 and 392 days of age for animals at Danish Test Stations which are tested between 294 and 392 days. Recorded weights were obtained for individual bulls of the following breeds (no. animals): Simmental (20), Angus (36), Hereford (53), Charolais (51) and Limousin (44). Feeding and management procedures at these Stations are described by Andersen et al. (1989). Results shown in Table 1 illustrate that differences between actual (A) and predicted (P) live weights were consistently greater at 294 than 392 days. Studies in progress suggest that this was due to an incremental growth response of animals following a change from loose to individual housing at 280 days. The correlations between A and P values were highly significant (Table 1) which suggest that both assessment methods were of similar accuracy overall. Despite this however, there may be important differences which need to be resolved when a small number of animals are to be selected. For example, within-breed selection for the top three animals in gain by both methods showed that two animals were common for both Sixnmental and Hereford, and only one for each other breed. Table 1 Mean values finish (392 differences correlations (kg) for actual (A) live weights at the start (294 d), d) and gain during test (294 to 392 d) together with mean (2 s-d.) between A and predicted (P) live weights and between A and P ANDERSEN, B-B., MADSEN, P., ELASTRUP, S. and OVESEN, E. (1989). Inst. Anim. Sci. Res. Bull. No. 653. Danish Nat. + Dept Wool and Animal Science, University of N.S.W., Kensington, N.S.W. 2033. ** National Institute of Animal Science, P-0, Box 39, 8830 Tjele, Denmark. 533