The potential of Mimusops zeyheri seed meal as a dietary energy source in broiler quail diets
The shortage of dietary energy sources for poultry feeds contributes to increased feed costs hence the need to search and develop alternative sources. Mimusops zeyheri seed meal (MZSM) has high energy content. This study evaluated the potential of MZSM to replace maize meal (MM) as an energy source in broiler quail finisher diets. The effects of dietary MZSM on the growth performance, feed utilisation efficiency, viscera morphometry, general health and meat quality of broiler quail were determined. Thirty-two 5-week old male broiler quails were randomly allocated to 4 diets wherein MZSM replaced MM on gross energy basis at 0%, 12.5%, 25% and 37.5% (diet 1 to 4) and fed for 4 weeks. Body mass and feed intake (FI) was measured. Body mass gain (BMG), average daily gain (ADG) and feed conversion ratio (FCR) were computed. On slaughter, the carcasses were eviscerated and viscera macro-morphometry determined. pH and colour of the breast muscle were measured. Tissues were collected for physico-biochemical and histological assays. At 37.5% inclusion MZSM reduced (p<0.05) FI. Dietary MZSM did not affect (p>0.05) BMG, ADG and FCR but increased (p<0.0001) the mass of proventriculi, ventriculi and small intestine mass and the small intestine length of the quail. Visceral fat decreased (p<0.0001) with an increase in dietary MZSM. At 25% and 37.5% inclusion, MZSM increased (p <0.05) villus height and width, crypt depth and villus height:crypt depth ratio. MZSM had no effect (p>0.05) on fasting blood glucose concentration but at 25% inclusion level it increased (p<0.05) fasting blood triglyceride concentration. Dietary MZSM decreased (p<0.05) hepatic lipid content. At 25% inclusion MZSM increased (p<0.05) plasma urea concentration. Dietary MZSM did not affect (p>0.05) plasma uric acid concentration. At 25% inclusion, MZSM increased (p<0.05) plasma ALT activity and at 12.5% and 37.5% it increased (p<0.05) plasma ALP activity while at 25% and 37.5% inclusion it significantly increased (p<0.05) TBARs concentration. Dietary MZSM (25% and 37.5% inclusion) increased (p<0.05) plasma total bilirubin concentration. It had no effect on pHi and colour of the quail breast muscle (meat). MZSM had no effect (p>0.05) on pHu but at 37.5% inclusion it decreased (p<0.05) redness of the meat 24-hours post-slaughter. Dietary MZSM increased (p<0.05) water holding capacity of the meat. At 12.5% inclusion it reduced (p<0.05) cooking loss. MZSM (25% and 37.5% inclusion) decreased (p<0.05) shear force required to cut through fillets. Dietary MZSM had no effect (p>0.05) on the meat’s moisture, dry matter and ash content. The meat’s crude protein content increased (p<0.05) with an increase in the meal and its fat decreased (p<0.05) with an increase in the meal. MZSM had no effect (p>0.05) on the meat’s total saturated, monounsaturated and polyunsaturated fatty acid content. At 25% and 37.5% inclusion, MZSM decreased (p<0.05) the meat’s trans and Cis fatty acid content but increased (p<0.05) the omega-3, -6 and -9 content. Mimusops zeyheri seed meal can partially replace MM in quail finisher diets without compromising growth performance and feed utilisation efficiency, as well as viscera morphometry and meat quality. Caution has to be exercised in the use of M. zeyheri as a dietary energy source as it may compromise liver function and increase lipid peroxidation in the birds.
A dissertation submitted to the Faculty of Health Sciences, University of Witwatersrand, School of Physiology, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Medicine Johannesburg, 2019