Effects of tallow in swine rations on utilization of calcium and phosphorus.

T HE relationship of dietary fat to calcium and phosphorus utilization has been reported for the rat b y many investigators (Haldi et al., 1939; French, 1942; Calverley and Kennedy, 1949; Cheng et al., 1949 and Swell et al., 1956). High dietary levels of fat have increased fecal calcium in monogastric animals through the formation of insoluble sQaps.~(Boyd et al., 1932 and Fedde et al., 1960). Existing relationships between calcium and phosphorus have led to assumptions that an effect on calcium brings about an effect on phosphorus behavior. Radiochemical methods for quantitative estimation of endogenous mineral losses permit the calculation of t rue absorption from the dietary source, and make possible quantitative measurements of factors affecting excretion and utilization (Hansard et al., 1961). Basic data, however, are lacking on the effects of added fat on nutrient digestibility, I t is known that interactions of energy intake and specific nutrients exist. Thus, the addition of animal fats to swine diets may create deficiencies not normally observed. The need for information on calcium and phosphorus interrelationships in swine, and the effects of added fat on the utilization of these minerals by swine prompted this study.