الكاتب: Multiple References

Recommendations of calcium and phosphorus requirements for sheep and cows at different stages of growth, pregnancy and lactation are published periodically by the Agricultural Research Council (ARC; 1965, 1980), the (US) National Research Council (NRC; 1968, 1975) and the Institut National de la Recherche Agronomique (INRA; 1978). These recommendations, which are based on all relevant research findings, vary considerably between the different sources, and indeed between successive publications from the same source.