Abstract:
Animal Production in Australia EFFECTS OF CALCIUM AND PHOSPHORUS DEPLETION AND REPLETION IN LAMBS C.C. SEVILLA and J.H. TERNOUTH* in In ed of Supplementation of lambs on a low Ca low P diet with P but not Ca resulted increased dry matter (DM) intake and digestibility (Sevilla and Ternouth 1980). lambs fed a low P diet; Young et al.(l966) found that P supplementation increasabsorption of P but not Ca. Our study was conducted to determine the effects Ca and/or P repletion after a period of Ca and P depletion. Twenty 4-month old Corriedale wethers were randomly alloted to 5 treatment groups and kept in metabolism cages for an 18 week experiment. One group (control) was fed a high (H) Ca-HP diet and another group fed a low (L) Ca-LP diet during the entire experiment. The other three groups were fed the LCaLP diet for 12 weeks and then repletion diets - LCaHP, HCaLP or HCaHP. The basal (LCaLP) diet of 55% barley straw, 36% sugar, 6.8% gluten, 1.4% urea and 0.7% mineral-vitamin mix, was fed ad lib. The basal diet contained 1.25g Ca and 0.656g P/kg DM and CaC03 and Na2 HP04 were added to achieve the H dietary levels of 5.Og Ca and 4.5g P/kg DM. During the depletion period, the depleted lambs had significantly lower liveweight gains (16.5 v. 102.4g/d), daily DMintake (57.4~. 64.6g/kg'.75) and digestibility (63.2 - 69.z) and plasma P (3.48 - 6.94mg%) than the control lambs. v. v. TABLE 1 The effect of calcium and phosphorus repletion During the repletion period, the lambs fed diet HCaLP had liveweight gains and DM intakes similar to the control group. The sheep fed the HP diets ate more food than those fed the LP diets. The liveweight changes were in the same order as the DM intakes (i.e. HCaLP <LCaLP <LCaHP CHCaHP). The HCaLP diet was digestedleast well. Ca and P repletion generally increased the plasma Ca and P levels although when diets LCaHP and HCaLP were fed, the.changes in plasma levels were exaggerated. When repletion occurred, the ribs had increased concentration of Ca and P. The results show that after a period of Ca and P depletion, both minerals have to be resupplied to enable completely normal growth to occur as a result of higher food intakes and digestibility. A HCaLP diet seems to be particularly disadvantageous. SEVILLA, C.C. and TERNOUTH, J.H. (1980). Proc. Aust. Soc. Anim. Prod. 13:449. = Br. J.Nutr. YOUNG, V-R., RICHARDS, W.P.C., LOFGREEN, G.P. and LUICK, J.R. (1966). 20:783. * Dept. of Animal Production, University of Queensland, 633 St. Lucia, Qld 4067.