Evaluation of groundnut meal protein for poultry

Abstract

Five samples of Iraqi groundnut meals used by feed manufacturers in Lebanon were subjected to three animal assays and several chemical assays commonly used for evaluating proteins. Orange G binding capacity was highly correlated with crude protein content of the five meals (r=O.98). Available lysine values did not differ, with the exception of one meal which contained considerably less than the others and also less total lysine. There was considerable difference in nitrogen solubility ranging from 18 to 53 %. True protein values were highly correlated with crude protein values (r -0.99). Amido nitrogen ranged between 3 . 4 and 6.5%. In all meals methionine and lysine were limiting amino acids, these being the first and second limiting respectively. Some also contained limiting threonine, tryptophan and isoleucine; the order of limitation changed when a cereal base was used with groundnut as the major protein source rather than the only source. The protein efficiency ratios (PER) of groundnut meals did not differ significantly, but were all significantly lower than for soyabean meal. Amino acid supplementation of groundnut meals resulted in an improvement in PER but not all meals responded in the same way, which indicates that the poor nutritive value of certain Iraqi groundnut meals is not due to amino acid limitation alone, but also to toxic substances. A modification of Anwar's method of calculating the gross protein value is presented; it gives a higher correlation with the available lysine value than the methods of Anwar or Robertson et al. Statistical analysis of the gain in body weight showed significant differences (P< 0.01) between meals studied. Net protein utilisation operative values ranged from 3440% in contrast to soyabean meal which gave a value of 52. Variation in net dietary protein calories ?( followed the same trend as NPU(op) values. IntroductionAs a source of protein for poultry, groundnut meal is of considerable importance in the Middle East, since other protein supplements such as soyabean, fish and meat meals imported from Europe and the U.S.A. are more expensive. Many studies on protein quality of groundnut meal have been published but little is known about meals produced in this area, which seem to vary in composition and protein quality as observed from previous feeding trials in this laboratory.1The commonly used methods for evaluating proteins were applied in this study to five samples of these meals received by feed manufacturers in Lebanon from Iraq. The methods used consisted of three animal assays and several chemical assays. The animal assays were: gross protein value (GPV) and protein efficiency ratio (PER) with chicks and net protein utilisation operative (NPU(op)) with rats. Gross energy of diets was also determined and the metabolisable energy and