Abstract:
Animal Production in Australia EFFECT OF DIFFERENT DIETARY LEVELS OF CALCIUM AND PHOSPHORUS IN SHEEP C.C. SEVILLA* and J.H. TERNOUTH* The reasons for the reduction in food intake due to low P diets are not fully understood because of other interrelated factors such as Ca:P ratio, degree of deficiency and physiological state of the animal. This study was conducted to investigate the response of lambs fed high and low levels of Ca and P in the diet (and to induce P deficiency in lambs for subsequent studies), Twelve 6-month-old Corriedale wether lambs (21.1-31.6 kg) were fed 4 diets containing high (H) and low (L) concentrations of Ca and P, in metabolism crates for 120 days. A basal diet composed of 60% barley straw, 31% refined sugar, 6.4% gluten, 1.7% urea and 0.9% mineral-vitamin supplement and estimated to contain 9.92 MJ ME, 130 g crude protein, 1.35 g Ca and 0.72 g P/kgDM was fed to animals on low Ca and P diets. For high concentration diets, the levels of Ca and P were increased to 8.2 and 4.5 g/kgDM,respectively. Live weight,food intake,dry matter digestibility (DMD), apparent P absorption and plasma Ca and P were measured. TABLE 1 Response of sheep fed high and low concentrations of Ca and P? The basal diet was initially consumed by all sheep but by the fourth week, the intake of the LP lambs had decreased so that over the whole experiment there were marked differences in intake (Table 1), which were reflected in the liveweight change. The difference in liveweight change between the HCaLP and LCaLP diets was significant (~~0.05). Plasma P levels were related to the concentration in the diet but plasma Ca levels were only reduced for LCaHP diet. DMD was reduced in HCaLP diet. Apparent P absorption was negative for LP diets. With HP diets,lambs on LCa diets had higher apparent P absorption over those on HCa diets. The results support the observation of Field et al. (1975) that low P diets cause significant reductions in food intake, the effect being due to the depletion of P reserves of the animal rather than the dietary levels per se. The low P diets used in this experiment resulted in negative P absorption. The lower DMD of the LP diets agree with earlier results obtained in our laboratory (Milton and Temouth 1979). FIELD, AX., SUTTLE, N.F. and NISBET, D-1. (1975). J. Agric. Sci. gz: 435. MILTON, J.T.B. and TERNOUTH, J.H. (1979). Proc. Nutr. Soc. Aust. 4: 150. = * Department of Animal Production, University of Queensland, St,Lucia Qld. 449 4067.