Inclusion of mopane worm meal in Jumbo quail diets : nutrient utilization, physiological and meat quality responses

Abstract

There is an urgent need to mitigate the negative impact of soybean production on the environment while ensuring sustainable poultry production to meet the protein requirements for the growing human population. Insect meals such as mopane worm (Imbrasia belina) are considered as sustainable alternative protein sources because of their high biological value, small carbon footprint, and less water and space requirements compared to plant protein sources, particularly soybean. Replacing soybean products in poultry diets with insect protein sources could ensure sustainable intensification and profitable commercialisation of the poultry industry. This would also allow the diversification of the industry with poultry species such as quail (Coturnix coturnix) to complement the supply of dietary protein for human consumption. Therefore, this study was undertaken to determine the effect of partial substitution of soybean products with graded levels of mopane worm meal (MWM) on feed utilisation, growth performance, serum biochemistry, carcass characteristics, internal organ sizes, and meat quality parameters in Jumbo quails. A total of 384, two-week-old mixed-gender quails (71.2 ± 5.40 g live-weight), were evenly and randomly allocated to 32 replicate pens (experimental units) and reared using four isoproteic and isoenergetic experimental diets formulated by replacing soybean products in a commercial standard grower diet as follows: 1) MWM0 = a commercial standard grower diet without mopane worm meal; 2) MWM5 = a commercial standard grower diet in which 50 g/kg of soybean products were replaced with mopane worm meal; 3) MWM10 = a commercial standard grower diet in which 100 g/kg of soybean products were replaced with mopane worm meal; and 4) MWM15 = a commercial standard grower diet in which 150 g/kg of soybean products were replaced with mopane worm meal. Average weekly gain-to-feed ratio (G:F) was calculated using average weekly body weight gain (ABWG) and average weekly feed intake (AWFI) measured during the four-week feeding trial. At six weeks of age, two quails per experimental unit were left behind for apparent nutrient

digestibility measurements and the rest of the birds were taken to a local abattoir for slaughter. During slaughter, blood was collected from two birds that were randomly selected per pen for analysis of serum biochemistry. Thereafter, the carcasses were eviscerated and used to measure carcass characteristics, internal organ sizes and meat quality parameters. Repeated measures analysis showed no significant week × diet interaction effect on AWFI, ABWG, and G:F. There were neither linear nor quadratic effects (P >0.05) on overall feed intake, overall body weight gain, final body weight, and overall G:F in response to increasing levels of MWM. Similarly, no significant dietary effects were observed on overall feed intake and overall growth performance traits of the quails. No significant linear and quadratic trends were observed for dry matter digestibility (DMD), organic matter digestibility (OMD), neutral detergent fibre digestibility (NDFD) and crude protein digestibility (CPD) with the exception of acid detergent fibre digestibility (ADFD), which linearly declined [y = 403.7 (±27.43) - 0.26 (±0.88) x; R2 = 0.338, P = 0.003] in response to increasing levels of dietary MWM. Likewise, experimental diets affected (P >0.05) only ADFD. Regression analyses also showed no linear and quadratic responses for serum biochemical parameters as MWM levels increased. Similarly, no dietary influence (P >0.05) were observed on all serum biochemical indices. There were no significant linear or quadratic trends for all carcass traits and internal organs, except for weights and lengths of large intestines which linearly declined [R2 = 0.138; P = 0.040] with MWM inclusion levels. At 24 h post-mortem, quadratic trends (P <0.05) were observed for breast meat redness (a*) [R2 = 0.118; P = 0.046], yellowness (b*) [R2 = 0.094; P = 0.001] and chroma [R2 = 0.312; P = 0.0004] as MWM levels increased. There were significant dietary effects on b*, chroma and shear force. Diets MWM5 and MWM10 promoted higher (P <0.05) b* and chroma values than the control diet MWM0. Breast meat from quails on diet MWM5 had the highest (P <0.05) shear force (2.39 N) than breast meat from quails fed diets MWM0 and MWM10. It was concluded that MWM has a potential to replace soybean products because it promoted similar

growth performance, nutrient utilisation, serum biochemical indices, and carcass traits as the soybean-based control diet. An optimum inclusion level of MWM could not be determined using the measured parameters, suggesting a need to further investigate levels beyond 150 g/kg of MWM in diets of Jumbo quails.