Dietary effects of Marula (sclerocarya birrea caffra) nut meal on the growth, health and meat quality of broiler guinea fowl (numida meleagris)

Abstract

The sub-Saharan poultry feed industry depends on imported soyabean meal (SBM) as a dietary rotein (DP) source in feeds. This makes poultry production costly hence the need to develop local alternatives. Marula nut meal (MNM), a by-product of oil extraction from Marula kernels, has a high crude protein (CP) content and has been successfully used in quail feeds but has not been evaluated in Guinea fowl (GF) feeds. This study evaluated the potential of MNM to substitute SBM as a DP source in GF grower and finisher diets by determining its effects on the growth performance, health and meat quality of GF. Five grower diets wherein MNM substituted SBM on a CP basis at 0, 25, 50, 75 and 100% were formulated. Thirty eight 4-week old keets were randomly assigned to the diets (n =7 to 8) and fed for 5 weeks after which they were transferred onto corresponding finisher diets and fed for 3 weeks. Weekly body weight, daily feed intake (FI) and terminal body weight (TBW) were determined. Body weight gain (BWG), average daily weight gain (ADG) and feed conversion ratio (FCR) were computed. On slaughter blood was collected. Haematocrit, blood glucose and triglyceride concentration were determined. Surrogate markers of liver and kidney function were determined and lipid peroxidation estimated. Viscera macro-morphometry, carcass weight and dressing percentage were determined and liver lipid content was also determined. Tibiae and femora mass, length and their mass to length ratio were measured. The meat’s pH [initial (pHi) and ultimate (pHu)], colour, proximate and fatty acid composition were determined. Dietary MNM had no effect (P>0.05) on the GF’s haematocrit, blood glucose and triglyceride concentration, liver lipid content and TBW. During the grower phase, except for week 2 where GF fed diet 3 had the highest (P<0.05) BWG and the highest ADG (P<0.05), dietary MNM did not affect (P>0.05) the GF’s BWG, ADG, FI and FCR. In week 5 of the grower phase GF fed diet 5 had the highest (P<0.01) FI. During the finisher phase, dietary MNM did not affect GF’s weekly BWG, ADG, FI. However, in week 3 of the finisher phase, GF fed diet 3 had the highest (P<0.05) FCR. Overall (grower and finisher phases) dietary MNM had no effect on BWG, ADG and FI. However, GF reared on diet 3 had the highest (P<0.05) FCR. Dietary MNM did not affect (P>0.05) the tibiae and femora indices of the GF neither did it affect their viscera macro-morphometry, liver and kidney function and lipid peroxidation (P>0.05). Marula nut meal did not affect (P>0.05) the pH, colour and tenderness of the GF’s meat. Breast meat of GF fed diet 3 and 4 had the highest (P < 0.0001) fat vi content. Meat from GF fed diet 1 and 3 had the highest (P < 0.0001) calcium content. Dietary MNM did not affect the lipid (total saturated fatty acids, total monounsaturated fatty acids and total polyunsaturated fatty acids) content of the meat but the oleic acid (OA) content of the meat increased non-significantly (P>0.05) with an increase in dietary MNM inclusion. Dietary MNM at 25%, 75% and 100% (CP basis) can potentially substitute SBM in grower and finisher GF feeds without compromising growth performance, liver and kidney function as well as meat quality. Importantly, it can be exploited to increase the OA content of the meat. However caution must be taken as its use at at 50% inclusion level compromised feed utilisation efficiency