EFFECT OF CALCIUM LEVEL AND TRACE MINERALS ON THE RESPONSE OF YOUNG PIGS TO UNIDENTIFIED GROWTH FACTORS

Abstract

Variable results have been reported when different sources of unidentified growth factors have been fed to early weaned pigs and to growing and finishing swine. Gard et al. (1955) using weanling pigs fed purified diets, reported no clear cut evidence that dried brewers yeast, dried whey or menhaden fish solubles contained unidentified growth factors; but, a grass juice concentrate produced significant growth responses. Noland et al. 1955 reported variable results with condensed tuna fish solubles but obtained a significant growth response from cod liver mycelium. Meade (1956) reported that the addition of several sources of unidentified growth factors in pig starters did not result in a consistent increase in gains. In contrast, recent studies with chicks (Camp et al., 1956; Morrison et al., 1956; Supplee et al., 1956) have shown that several sources of unidentified growth factors as well as the ash of these growth factors will stimulate growth in chicks when added to purified diets. The objectives of this study were: (1) to formulate and test a “semi-purified” diet suitable for studying various sources of unidentified growth factors; (2) to study various levels of minerals as they effect the response to unidentified growth factors; (3) to study the effect of various crude and pure sources of unidentified growth factors on the young pig. This study was composed of five experiments in which early weaned pigs 21 days of age were fed for a period of 6 to 10 weeks. These pigs averaged about 10 lb. initially and were allotted