Response in antioxidant activity and shelf life of meat from broilers fed on incremental levels of Vachellia tortilis leaf meal.
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The broad objective of the study was to determine the antioxidant activity and shelf life of meat from boilers fed on incremental levels of Vachellia tortilis leaf meal. One hundred and twenty Cobb-500-day old unsexed broilers were assigned in a completely randomized block design to six experimental diets containing 0, 30, 60, 90, 120 and 150 g/kg DM of Vachellia tortilis leaf meal. Each diet was offered ad libitum to 10 broilers in each pen, with a total of 12 pens. Each diet had one replicate. After overnight fasting and slaughtering of chickens, skinless and boneless chicken samples (breast and thigh) were collected, vacuum sealed and packed at 4°C until analysis. The determination of antioxidant properties in meat samples was measured using three assays; 2, 2-diphenyl-1-picryhydrazyl (DPPH), ferric reducing power (FRAP) and β-carotene-linoleic acid assay. The antioxidant activity using the DPPH model did not go beyond 50 % in all the inclusion levels. The FRAP assay exhibited a concentration-dependent linear response to the inclusion of V. tortilis leaf meal. The β-carotene-linoleic acid had the highest activity of 48.9 and 40.99 % recorded at 60 and 90 g/kg inclusion level respectively. The β-carotene-linoleic acid displayed a quadratic response, with the equation (𝑦𝑦=−0.0037𝑥𝑥2+0.7756𝑥𝑥+2.7811) showing 104.8 g/kg to be useful in improving the potency of natural antioxidants. Broiler breast and thigh samples were collected for the determination of shelf life. Drip loss (%) was measured after 24 hours of slaughter, meat pH, colour (L*, a* and b*), texture and v cooking loss (%) were measured at day 0, 7, 14 and 21 days. Broilers assigned to diets containing high levels of Vachellia tortilis leaf meal had tougher meat. High values of Warner-Bratzler Shear Force (WBSF) were recorded on day 21. Effect of leaf meal and days on texture had a linear response. High cooking loss results were obtained from the study, whilst there was no significant effect of leaf meal on the drip loss. The redness of meat had a quadratic response (𝑦𝑦=−0.0107 𝑥𝑥2+0.2779𝑥𝑥+6.145) over storage time. A period of not more than 13 days was found to be more ideal at retaining meat quality without development of lipid oxidation. An inclusion level of 94.5 g/kg of leaf meal improved the redness and yellowness of broiler breast and thigh meat samples respectively. In conclusion, Vachellia tortilis leaf meal can be incorporated in broiler diet up to 90 g/kg for improved storage time and antioxidant activity