Physiological responses and meat quality of Potchefstroom koekoek cockerels offered canola meal as an alternative to soybean meal
The current study was conducted to assess growth performance, protein utilisation efficiency, blood parameters, meat quality, bone breaking strength, density and mineral composition of Potchefstroom Koekoek (PK) cockerels offered canola meal as an alternative to soybean meal. The aim of the study was to evaluate the potential use of canola meal (CM) to replace soybean meal (SBM) in broiler grower diet as protein source. This was achieved through feeding indigenous chickens diets with incremental levels of CM with the expectation that the chicken’s performance would have negatively affected. A hundred and seventy-five, 36-day old PK cockerels were randomly allocated to the dietary treatments: Control = diet with no canola meal inclusion, CM37.5 = 37.5 g canola meal/kg soybean meal, CM62.5 = 62.5 g canola meal/kg soybean meal, CM87.5 = 87.5 g canola meal /kg soybean meal, CM175 = 175 g canola meal/kg soybean meal. Canola meal had numerically higher average concentration of ash, crude fibre while dry matter, organic matter and crude protein were higher in SBM. The concentration of calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na) and sulphur (S) was numerically higher in SBM while copper (Cu), manganese (Mn) and iron (Fe) were higher in CM. Formulated diets had similar (P > 0.05) apparent digestibility values for minerals, dry matter and fibre but higher inclusion of CM reduced (P < 0.05) crude protein (CP) digestibility. Diet significantly affected growth performance parameters, protein utilisation efficiency and serum biochemistry of the PK cockerels. All the mean values of the haematological parameters were within the normal range regardless of the inclusion levels of CM. The PK cockerels fed control diet had the lowest (P<0.05) breast muscle, wing, drumstick and vertebrae weight. The PK cockerel fed control diet had the lowest (P<0.05) heart (22.20g) and liver weights (7.9 g). Higher (P<0.05) small intestine weights were observed on the PK cockerels fed diet CM175. The L* value and b* value of the breast muscle from the PK cockerels fed diet CM37.5 were significantly higher than those fed the control diet. The a* value of the breast muscle increased significantly with the inclusion levels of CM. The pHu (Ultimate pH) values of the meat from PK cockerels fed diet CM37.5 (5.97) were significantly lower (P<0.05) than those fed control diet (6.18). However, the PK cockerels fed the control and CM37.5 diets had the lowest shear force values. Breast muscle from cockerels fed the control diet had the highest (P<0.05) concentration of Ca, Mg, P, Na and K. There were no significant dietary effects on tibia length, weight, width, density, diameter proximal end, diameter distal end, breaking strength and ash percentage. Diets, however, had a significant effect on macro and trace mineral concentrations of the tibia. Tibia from cockerels fed diet CM175 had the lowest (P<0.05) Ca and P content. Lower (P<0.05) tibia Mg and Na concentration were observed in the cockerels fed diets CM87.5 and CM175 compared to tibia of those cockerels fed on the other diets. The findings of this study concluded that CM shown to have potential as an alternative to SBM in grower broiler diets and the indigenous chickens fed CM can be a tool for curbing sodium, potassium and iron and can be used to improve the meat quality of indigenous chickens in Africa.