Sources of Unidentified Factors for the Pig

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Abstract
A total of 158 weanling pigs was used in a series of five factorial experiments to test dehydrated alfalfa meal, menhaden fish solubles, grass juice concentrate, dried brewers' yeast, a dried whey-product with whey fermentation solubles, and a streptomycin residue, as possible sources of unidentified growth factors. The pigs were allotted at random to the treatments from litter outcome groups. Individual feed consumption data were collected in 3 of the experiments. Both purified and practical diets were used. All rations within an experiment were equalized for crude protein. The final weights for each experiment were analyzed according to the method of covariance to adjust for differences in initial weight. In the tests where individual feed consumption data were available final weights were also adjusted for differences in feed consumption. According to the statistical analyses of adjusted final weights, grass juice concentrate produced a significant growth response. This growth response approached significance when final weights were also adjusted for differences in feed consumption. The significant interactions of grass juice concentrate with dried whey and of menhaden fish solubles with dried whey were not significant when feed consumption was considered. These ingredients influenced the voluntary feed intake and, in addition, grass juice concentrate may be supplying an unidentified growth factor. An assay of the grass juice concentrate for estrogenic activity indicated that 1 ml. contained no more than the equivalent of 0.016 mg. of estradiol benzoate. Dehydrated alfalfa meal fed at the 10 percent level depressed growth. The crude fiber content of the dehydrated alfalfa meal was not the primary factor causing this growth depression because a crude fiber equivalent did not depress growth. A streptomycin residue depressed growth and feed efficiency when incorporated in a purified diet at the 3.0 percent level but promoted growth when included in a practical ration at the 1.8 percent level. There was no clear-cut evidence that dried brewers' yeast, dried whey-product with whey fermentation solubles, or menhaden fish solubles contained unidentified growth factors for the pig. Copyright © . .