الكاتب: Multiple References

There is concern over the recent drastic reduction by the Agricultral Research Council (ARC, 1980) in recommendations of calcium and, more particularly, of phosphorus requirements for sheep and cows at different stages of growth, pregnancy and lactation (Cooke, 1982; Gueguen, 1982). This reduction highlights the considerable variation in recommendations that is possible by different interpretations of the same research findings. For example, Table 1 shows recommendations for P by the ARC (1965, 1980), the (US) National Research Council (NRC, 1968, 1975) and the Institut National de la Recherche Agronomique (INRA, 1978) for a 50 kg sheep giving an average of 1-36 1 milk/d during the first 8-10 weeks of lactation. Whereas the ARC (1980) recently reduced their recommended requirement from 7.0 to 4.1 g/d, the NRC (1975) increased their recommendation from 4.6 to 7.8 g/d. INRA (1978), meanwhile, recommended an intermediate value of 5.8 g/d. The present work was carried out to test the adequacy of the recent ARC (1 980) Ca and P recommendations for pregnant and lactating ewes. At the same time, Ca and P metabolisms were compared throughout pregnancy and lactation in ewes fed according to these ARC (1980) recommendations and in ewes fed a plentiful supply of dietary Ca and P. The results of studies of P metabolism are presented in this paper, and those of Ca metabolism in the preceding paper (Braithwaite, 1983).