Amino Acid Reference Values For Selected Feedstuffs Used In The Nigerian Poultry Industry

ABSTRACT

The main objective of this study was to establish reference protein composition values for selected local feedstuffs such as dry brewers spent grain (DBSG), cassava meal (CAM), palm kernel cake (PKC) and groundnut cake (GNC) for the Nigerian feed industry by determining amino acids profiles and amino acids compositional quality scores. The selected local feedstuffs were each sourced from five locations from northern and southern parts of Nigeria such that there were five samples for each raw material and 20 samples in all. The samples were analysed at Evonik Industry Laboratory, Germany. Results were generated on dry matter (DM), crude protein (CP) standardized to a dry matter content of 88%, CP as is, total amino acids (Taa) without NH₃, and NH₃ content. Total amino acids Essential amino acids, non-essential amino acids, amino acid scores such as qualitative, quantitative and chemical scores were calculated and values subjected to descriptive statistics such as mean, standard deviation and coefficient of variation across samples values from different locations. This study showed that all the sampled local feedstuffs were high in dry matter content, with values ranging from 89.304 ± 0.857% recorded for CAM to 93.006 ± 0.456% recorded for PKC. However, the coefficient of DM variation was less than 1.00%. CP content of the DBSG, CAM, PKC and GNC sampled (as is), ranged from 0.988 ± 0.230% for CAM to 44.430 ± 6.600% for GNC, while the CV between the different samples ranged from 4.518% recorded for PKC to 23.279% recorded for CAM. The Taa ranged from 0.837 ± 0.182% recorded for CAM to 40.025 ±5.831% recorded for GNC, with high CVs of 21.744% for CAM and 14.568% recorded for GNC values, indicating wide variations in Taa of samples from different locations. Methionine content of the feedstuff ranged from the 0.014 ± 0.005% recorded for CAM to the 0.441 ± 0.039% recorded for DBSG, with CVs of 35.714% and 11.004 for CAM and GNC respectively. Lysin values ranged from 0.045 ± 0.006% recorded for CAM to 1.439 ± 0.162% recorded for GNC, with CVs across five samples of each material being generally higher than 10% except for PKC. Again, threonine concentrations ranged from the 0.039 ± 0.008% recorded for CAM to the 1.150 ± 0.146% recorded for GNC, while coefficient of variations between individual sample of DBSG and PKC were less than 10% CV, but wide between samples of CAM and GNC. Isoleucine values ranged from 0.035 ± 0.011% recorded for CAM to 1.499 ± 0.225% recorded for GNC, however, the CV between CAM and GNC were greater than 10%, while DBSG and PKC recorded less than 10% CVs. Mean values of leucine ranged from 0.068 ± 0.032% recorded for CAM to 2.771 ± 0.394% recorded for GNC, while the phenylalanine content ranged from 0.047 ± 0.017 recorded for CAM to 2.262 ± 0.354% recorded for GNC. Qualitative amino acid scores showed that GNC was the richest protein source and was rich in all the essential amino acids with exception of methionine. DBSG was rich in four essential amino acids (leucine, valine, phenylalanine and arginine), while PKC was rich only in arginine and moderate in isoleucine, leucine, valine and phenylalanine. CAM was poor in all essential and non essential amino acids contents. The quantitative scores of the amino acid profiles of the sampled feedstuffs showed that on mean Taa bases, PKC contained 47.92% essential amino acids while GNC contained 43.24%, DBSG (42.21%) and CAM (41.19%). The percentage mean total neutral amino acids in the feedstuffs ranged from 67.58% recorded in PKC to 90.68% recorded in DBSG indicating that these are the most abundant amino acids in the feedstuffs. It was concluded that Nigerian GNC based diets should be supplemented with synthetic methionine, while DBSG based diets should be supplemented with lysine, methionine and to some extent threonine for them to drive optimal performance in monogastric animals. Nigerian PKC cannot be regarded as a protein source since it requires fortification with synthetic sources of almost all the essential amino acids. CAM based diets should be supplemented with all the synthetic amino acids, especially the limiting amino acids. Practical feeding trials with monogastric livestock should be carried out to validate these results, since the study was limited to laboratory analysis.