The use of bodyweight, total body water and red cell volume to predict muscle weight of breed cattle.

Abstract

THE USE OF BODY WEIGHT, TOTAL BODY WATER AND RED CELL VOLUME TO `PREDICT MUSCLE WEIGHT OF BEEF CATTLE P. H. SPRINGELL*, R. M. BUTTERFIELD, E. R. JOHNSON, and R. M. SEEBECK* Water -and red two breeds and fed Muscle weight weight alone, or in cell volumes were determined in twelve steers belonging to on three diets, before their dressed carcasses were dissected. was predicted by a logarithmic relationship, using fasted body combination with total body water and red cell volume. Summary I. INTRODUCTION Water and red cell volumes have been used for predicting fat and muscle content of carcasses (Hansard 1963; Doornenbal and Martin 1965). Although promising results have been claimed, these predictors may not be superior to applying the average relationship between dissected components and the body weight (Tulloh l964). The use of body weight, red cell volume `and total body water in equations predicting muscle weight is examined in this paper. II. EXPERIMENTAL Eight British and four Fl Brahman x British steers were given three diets that produced different rates of live weight gain (Table 1). Two diets, low (L) and high (H) (Springell 1968a), were supplied for 15 months before nine animals (aged 30 months) were slaughtered. Three steers, previously on diet L, were put on improved pasture for 11 weeks and were then given lucerne hay in yards until they were slaughtered at the age of 39 months. The mean fasted body weight at slaughter (401 * 29 kg) of this group (L/H), was not significantly different from that of the six animals which prior to slaughter had been given diet H (423 f- 12 kg). Cattle were slaughtered and dissected (Butterfield 1963) within a few days of the total body water (tritium dilution) and red cell volume (Wr) determinations (Springell 1968a, b). The mean 16 h fasted body weights at the time when isotopic determinations were made and when slaughter took place, differed by only 7.3 t- 3 kg, so that no major composition changes were probable in the interim. Methods of computation were similar to those described by Seebeck and Campion (1964). Four models, representing alI or parts of the following general model, were used: *Division of Animal Genetics, C.S.I.R.O., Cattle Research Laboratory, Rockhampton, Queensland. TDepartment of Veterinary Anatomy, University of Queensland, Brisbane. $Present address: Department of Veterinary Anatomy, University of Sydney, N.S.W. 314 where Y = muscle weight (kg), p = intercept, B = breed effect, N = nutrition effect, FBW = fasted body weight (kg), TBW = total body water (l.), RCV = red cell volume (l.), and e = error term. Interaction between breed and nutrition was found to be non-significant. III. RESULTS AND DISCUSSION The pre- and post-slaughter data are given in Table 1, and the effectiveness with which combinations of various parameters can be used for muscle weight prediction is summarized in Table 2. No significant breed or diet effects were observed (Table 2) apart from the breed effect (P < 0.05) in Model III. Fasted body weight made a highly significant contribution to total variability in all four models. Contributions by the total body water never reached the 5% significance level, while red cell volume reached that level once. The inclusion of red cell volume in Models II and IV reduced the breed effects and altered the magnitude of the standard expected values. On the other hand, the increase in nutritional effects in Model IV was a drawback. However, Model IV was better for muscle weight prediction than the other models, since there was a substantial reduction in the residual variance. TABLE 1 315 Furthermore, the standard error of prediction in Model IV (3.5%) was also appreciably lower than the corresponding values of 5.9, 4.7 and 5.4% for Models I to III respectively. Nevertheless, if considerations such as cost, labor, time etc. are taken into account, then it becomes questionable whether the improved prediction, obtained by including estimates of the water and red cell volume, is of sufficient magnitude to justify their use in preference to weighing alone. An attempt to predict fat weight from the present data by similar means proved unsuccessful. IV. ACKNOWLEDGMENTS We wish to thank Mr. D. A. Baker, Mr. A. K. Duffield and Miss S. J. Shepherd for their skilful technical assistance. The work was supported in part by the Australian Meat Research Committee. V. REFERENCES , R. M. ( 1964). In: 'Carcase composition and appraisal of meat animals.' (D. E. Tribe, Ed.). Tech. Conf. 2MeZbourne. (C.S.I.R.O.: Melbourne.) DOORNENBAL, H., and M ARTIN , A. H. (1965). Canad. J. Anim. Sci. 45: 203. H ANSARD, S. L. ( 1963 ) . Ann. NY. A cad. Sci. 110: 229. SEEBECK, R. M., and CAMPION, E. J. ( 1964). Aust. J. agric. Res. 15: 471. S PRINGELL, P. H. ( 1968a). Aust. J. agric. Res. 19: 129. S PRINGELL , P. H. (1968b). Aust. J. agric. Res. 19: 145. T ULLOH. N. M. (1964). In: 'Carcase composition and appraisal of meat animals'. (D. E. Tribe, Ed.). Tech. Conf. MeZbcwne. (C.S.I.R.O.: Melbourne.) B UTTERFIELD 317