Evaluation of protein quality of poultry feedingstuffs. 2. Fish meal

Abstract

SummaryThe present study was made to evaluate the protein quality of 11 samples of fish meal (FM) covering a wide range of nutrient content to find a suitable laboratory method for predicting nutritive quality. The nutrient content of the samples ranged from 34 to 62% in crude protein, 28 to 48% in true protein and 0·99 to 2·87% in available lysine. The true protein content of FM was further partitioned into myogen, myosin and stroma proteins. The stroma protein accounted for 61% of total crude protein suggesting that a large portion of FM comprised scales, viscera, cartilage, bones and other inedible parts of fish (head, tail, etc.). Neither true protein nor its different fractions was found suitable to detect differences in protein quality of FM although there was an inverse relationship between stroma protein and nitrogen solubility.Available lysine content and relative nutritive value (RNV) were found accurate and reliable laboratory tests for assessing the protein quality of FM. The linear equations to predict gross protein value (GPV) from available lysine content and RNV areGPV = 11·2×% available lysine+34·5;GPV = 0·55×RNV+51.The correlation coefficients between biologically assayed and predicted GPV from available lysine and RNV were 0·71 and 0·62, respectively. The findings suggest that the screening of FM samples for their nutrient content is essential before compounding diets for different categories of chickens.