Protein value and amino-acid balance of condensed herring solubles and spontaneously heated herring meal. Chick experiments

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Abstract
1. In a series of tests chicks were fed up to 4 weeks of age on a ‘purified’ diet supplemented with 10% of protein from either herring meal or condensed herring solubles. 2. The solubles alone appeared of negligible value as a protein source, but certain mixtures of solubles and meal protein proved superior to meal alone, although the levels of the essential amino acids plus cystine and tyrosine were lower in the mixture than in meal alone. The supplementary effect may possibly be due to changes in the aminoacid ratio or balance. 3. Only tryptophan improved growth and viability when free amino acids were added singly to the solubles. Simultaneous supply of all 10 essential amino acids elevated growth to about 80% of that on meal alone. A combination of tryptophan, isoleucine, histidine and phenylalanine appeared nearly as effective as the 10. Depressant effects of free amino acids at the low levels used were also met with. The chick results followed closely the predictions made from the results of microbiological assays of the amino-acid composition of the solubles, and these were in conformity with the composition of the ‘ideal’ amino-acid mixture for chicks proposed by Fisher & Johnson (1957). 4. The small weight gains of the chicks on solubles alone consisted largely of water rather than true tissue. Appetite appeared to be governed by the balance of amino acids, this appearing to be more important than the absolute levels fed. This applied to diets with heated meal as well as the solubles.

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