الكاتب: Multiple References

Phosphorus deficiency is a major problem in many areas of the world. Most of the normal forages consumed by ruminants are little more than adequate with respect to their P content. Furthermore, increasing use of poor-quality roughages and by-products such as sugar-beet pulp, generally deficient in P, tends to exacerbate the problem. It has frequently been shown that feeding P-deficient diets could lead to decreased voluntary feed intake (Preston & Pfander, 1964; Coombe et al. 1971 ; Smith, 1984) with consequent effects on growth rate, milk production, etc. (Hemingway, 1967). These effects may be at least in part a result of impaired rumen function (Fishwick et al. 1977, Bass et al. 198 1 ; Durand et al. 1982; Breves & Holler, 1983). In general, ruminant feeds sustain the symbiotic rumen micro-organisms and only indirectly the host animal (Hungate, 1966) and it has been suggested that the P requirements of these organisms may be greater than that of the host animal (Preston & Pfander, 1964). There is, however, a strong interaction between the host animal and the rumen micro-organisms with respect to P supply and utilization, and in order to ascertain precise requirements of the micro-organisms, studies need to be carried out in situations which are not influenced by the host animal.