The effects of low nitrogen and phosphorus diets on pregnant and lactating ewes.

Abstract

Proc. Aust. Soc. Anim. Prod. Vol. 18 THE EFFECTS OF LOW NITROGEN AND PHOSPHORUS DIRTS ON PREGNANT AND LACTATING EWES S.P.S.BUDHI* and J.H.TERNOUTH* Reductions in food intake have been reported in growing lambs receiving diets deficient in nitrogen (N) and phosphorus (P) (McLachlan and Ternouth 1985). This experiment was designed to investigate the effects of dietary N and P deficiency in pregnant and lactating ewes. Twenty-four pregnant ewes (38 kg) were randomly allocated to a 2 x 2 experiment; the four dietary regimens containing high (H) and low (L) concentrations of-N and P. The basal diet (LNLP) was barley straw (4.07 g N and 0.55 g P/kg DM) fed ad libitum with fixed quantities of molasses( 210 g), 50 g wheat gluten and minerals. After lambing the quantity of supplements was increased by 25%. The high N and P treatments were created by the addition of urea and NaH2P03 so the H and L diets contained 99.3 and 64.3 g rumen Food intake was degradable protein and 3.02 and 0.66 g P/kg DM respectively. monitored daily and ewe and lamb live weight weekly. Milk intake of the lambs was measured at 21 and 28 days-of-age by tritium dilution (Dove and Freer 1979). Table 1 The effects of feeding ewes N and P deficient diets The intakes of the barley straw were significantly reduced in N deficient diet before and after parturition (P <O-01) but There were depressed intake after lambing only (P <O.OS). between the N and P deficiencies on intake. The differences are reflected in the liveweight changes in the ewes and the drunk by the lambs. There were no differences in lamb weight the ewes fed the the low P diets no interactions in straw intake amounts of milk at birth. The results are consistent with the earlier results of McLachlan and Ternouth (1985) that dietary deficiencies of N and P will depress food intake. The N deficiency appears to have an immediate effect upon food intake but the effect of the P deficiency was delayed due to the reserves of skeletal P and the lower P requirements of the pregnancy compared to lactation (Bass et al. 1981; Bortolussi et al. 1988). The food intake of milking goats fed P deficient diets was decreased by over 30% (Muschen et al. 1988). J.M.,FISHWICK, G., HEMINGWAY, R-G., PARKINS, J.J. and RITCHIE, N-S. (1981). J. Agric. Sci, 97: 365. BORTOLUSSI, G., TERNOUTH, J.H. and McMENIMAN, N.P. (1988). Proc. Aust. Nutr. Soc. 13: 124. DOVE, H. and Freer, M. (1979). Aust. J. Agric. Res. 30: 725. McEACHLAN, B.P. and TERNOUTH, J-H, (1985). Proc.Nutr.Soc.Aust. 10:148. _ MUSCHEN, H., PETRI, A., BREVES, G. and PFEFFER, E. (1988) J. Agric. Sci. 111: 255. BASS, * Department of Agriculture, University of Queensland, Qld. 4067. 459