Body-weight gain, protein efficiency ratio (PER), standardized protein efficiency ratio (Std PER) and gross protein value (GPV, GPV X and GPV 2 ) bioassays were compared with nitrogen incorporation efficiency (NTE) for their accuracy and precision to determine protein quality of fish meal (FM), groundnut cake (GN), mustard cake (MS) and cottonseed cake (CS) for poultry. Results showed that all the bioassays were significantly (P < 0-05) correlated with NIE and were equally effective in ranking the samples of FM, GN, MS and CS according to their protein quality although body-weight gain procedure was less sensitive.
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.
A study was made to evaluate the protein quality of groundnut cake (GN), mustard cake (MS) and cottonseed cake (CS) and to find a suitable laboratory test for predicting the protein quality of these cakes for chicks. Different oilseed cakes varied considerably in their crude protein, true protein and crude fibre content. The nitrogen solubility was higher in GN (87-7%) followed by MS (78-7%) and CS (60-9%). A similar trend was evident with regard to in vitro protein digestibility. The GN protein was, however, lower in available lysine (2-54%) than MS (3-97%) or CS (3-19%). The albumin, globulin, prolamin and glutelin fractions accounted for 74-1, 57-0 and 48-0% in GN, MS and CS, respectively. The nitrogen solubility, globulin content and modified relative nutritive value (RNV) correlated (P < 0-05) with gross protein value (GPV). The accuracy and precision of various regression equations for predicting the quality of protein in GN, MS and CS are discussed.
The proximate analysis of different types of rice bran (raw, parboiled, stabilised and deoiled) showed wide differences in the oil, fibre, ash and available carbohydrate contents. Free fatty acids in the fat extracted from the raw, parboiled and stabilised rice brans were 500.6, 277.8 and 163.1 g kg-l respectively. Palmitic, oleic and linoleic acids constituted about 94.5 %of the total fatty acids in oils extracted from those rice bran types.In chick growth trials, the average metabolisable energy of raw, parboiled, stabilised and deoiled rice brans was found to be 12.34, 11.67, 12.11 and 9.08 MJ kg-1 DM, respectively. The bodyweight gain of broiler chicks over a period of 6 weeks was depressed by 183, 79, 49 and 200 g when the level of the respective brans was raised from 200 to 400 g kg-1 in the diet. However, the food and protein conversions were significantly depressed at both levels of rice bran in the diets.
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