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Phosphorus and calcium metabolism in growing calves with special emphasis on phosphorus homoeostasis: 2. Studies of the effect of different levels of phosphorus, infused abomasally, on phosphorus metabolism

  • J. Challa (a1) and G. D. Braithwaite (a1)

Summary

Calves, fed continuously a P-deficient basal diet, were infused abomasally with a phosphate solution supplying either 0, 3, 6 or 9 g P/day in a 4 × 4 latin-square design experiment. Once steady-state conditions were achieved (after 2 weeks of infusion), 32P kinetic studies were carried out. At the same time, P and Ca balances and rates of flow of P at the reticulum were measured.

The rate of dietary P absorbed increased significantly with increasing P supply as did the serum P concentration. The rate of salivary P secretion was directly related to the serum P concentration and hence to P absorption, but the efficiency of absorption of salivary P remained relatively constant, ranging from 70 to 74% depending on treatment.

Despite the high requirements for P, the rate of endogenous faecal P loss increased directly with increased P supply and absorption, suggesting that some increased loss of P with increased P supply was inevitable. Urinary P secretion was negligible when the P supply was low but increased substantially as the serum P concentration increased from 2 to 4 mmol/1, possibly because the renal threshold was exceeded.

The rates of retention of P and Ca were low on the low-P treatment but increased significantly with increased P supply until this reached about 70 mg/day per kg live weight, beyond which they remained fairly constant, presumably because requirements had been met. Since the growth rate did not reach a maximum until the P supply exceeded 65 mg/day per kg live weight, it is suggested that the Agricultural Research Council (1980) recommendations of P requirements (34 mg/day per kg live weight) for these growing calves must be inadequate.

These results suggest that loss of P in saliva and urine may be determined by the serum P concentration whereas the efficiency of absorption of P from the intestine may be regulated according to P requirements.

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Agricultural Research Council (1980). The Nutrient Requirements of Ruminant Livestock. Farnham Royal: Commonwealth Agricultural Bureaux.
Boxebeld, A., Gueguen, L., Hannequart, G. & Durand, M. (1983). Utilization of phosphorus and calcium and minimal maintenance requirement for phosphorus in growing sheep fed a low-phosphorus diet. Reproduction Nutrition Développement 23, 10431053.
Braithwaite, G. D. (1984). Some observations of phosphorus homeostasis and requirements of sheep. Journal of Agricultural Science, Cambridge 102, 295306.
Braithwaite, G. D. (1985). Endogenous faecal loss of phosphorus in growing lambs and the calculation of phosphorus requirements. Journal of Agricultural Science, Cambridge 105, 6772.
Challa, J. (1986). Phosphorus and calcium metabolism in growing calves with special emphasis on phosphorus homoeostasis. Ph.D. thesis, University of Reading.
Challa, J. & Braithwaite, G. D. (1988). Phosphorus and calcium metabolism in growing calves with special emphasis on phosphorus homoeostasis. I. Studies on the effect of changes in the dietary phosphorus intake on phosphorus and calcium metabolism. Journal of Agricultural Science, Cambridge 110, 573581.
Clark, R. C., Budtz-Olsen, O. E., Cross, R. B., Finnamore, P. & Bauert, P. A. (1973). The importance of the salivary glands in the maintenance of phosphorus homeostasis in the sheep. Australian Journal of Agricultural Research 24, 913919.
Grace, N. D. (1980). Effect of increasing phosphorus intake on the P faecal endogenous loss in the sheep. Proceedings of the New Zealand Society of Animal Production 40, 221225.
Preston, R. L. & Pfander, W. H. (1964). Phosphorus metabolism in lambs fed varying phosphorus intakes. Journal of Nutrition 83, 369378.
Scott, D. & McLean, A. F. (1981). Control of mineral metabolism in ruminants. Proceedings of the Nutrition Society 40, 257266.
Scott, D., McLean, A. F. & Buchan, W. (1984). The effect of variation in phosphorus intake on net intestinal phosphorus absorption, salivary phosphorus secretion and pathway of excretion in sheep fed roughage diets. Quarterly Journal of Experimental Physiology 69, 439452.
Scott, D., Whitelaw, F. G., Buchan, W. & Bruce, L. A. (1985). The effect of variation in phosphorus secretion, net intestinal phosphorus absorption and faecal endogenous phosphorus excretion in sheep. Journal of Agricultural Science, Cambridge 105, 271277.
Snedecor, G. W. & Cochran, W. G. (1967). Statistical Methods, 6th edn.Iowa: Iowa State University Press.
Vipperman, P. E. Jun., Preston, R. L., Kitner, I. D. & Pfander, W. H. (1969). Role of calcium in the nutritional aetiology of a metabolic disorder in ruminants fed a high grain ration. Journal of Nutrition 97, 449462.
Young, V. R., Lofgreen, G. P. & Luick, J. R. (1966). The effects of phosphorus depletion, and of calcium and phosphorus intake, on the endogenous excretion of these elements by sheep. British Journal of Nutrition 20, 795805.

Phosphorus and calcium metabolism in growing calves with special emphasis on phosphorus homoeostasis: 2. Studies of the effect of different levels of phosphorus, infused abomasally, on phosphorus metabolism

  • J. Challa (a1) and G. D. Braithwaite (a1)

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