Phosphorus in the feeding of pigs : effect of diet on the absorption and retention of phosphorus by growing pigs

<p>An extensive review is given of the literature concerning phosphorus feeding of pigs. Subjects dealt with are: 1. physiological background, regulation and effect of diet composition and nutrient supply on phosphorus absorption and retention; 2. estimation of the amount of P present in the bodies of pigs using several models and 3. estimations of the P requirements of slaughter pigs from results of balance and slaughter experiments.</p><p>In the own experiments -using balance, slaughter, digestibility and feeding trials- on growing pigs the following aspects were studied: accuracy of measurements ; P absorption and retention as related to diet composition and nutrient supply; the effects of reduced P supply on performance and, possibly, on locomotory disturbances. It was shown that in phosphorus balance studies, because of carry-over effects, the adaptation period should be at least 21 days when there is a substantial change in phosphorus supply. Effects of dietary energy and protein on P absorption and retention could best be explained by their effect on the daily amount of protein and fat retention. The retention of P measured by the balance was only six per cent (25 + 17 g P) higher than measured by the comparative slaughter technique. Animals with a normal type of daily gain retained 5.0 to 5.1 g P/kg live weight gain, those with a leaner gain 0.2 to 0.3 g P/kg live weight gain more.</p><p>A technique was described to measure the digestibility of P in various feedstuffs and feed phosphates; substantial differences in digestibility of P between various feedstuffs and feed phosphates were observed. Maximal utilization of P was found at a dietary Ca/digestible P ratio between 2.9 and 3.5.</p><p>In various feeding trials, leg weakness was not observed any more frequently when slaughter pigs from 30 kg live weight onwards received diets with very low concentrations of phosphorus (g/kg feed) and calcium. However, calcification of the bones was poorer than that of the control animals.</p><p>Both optimal and just sufficient P requirements for slaughter pigs, were derived. These were expressed as the concentration of digestible P per kg diet.</p&gt