Chemical composition, anti-oxidative activity and in vitro dry matter degradability of Kinnow mandarin fruit waste

Aim: Fruit processing and consumption yield a significant amount of by-products as waste, which can be used as potential nutrient suppliers for livestock. “Kinnow” (Citrus nobilis Lour x Citrus deliciosa Tenora) is one of the most important citrus fruit crops of North Indian States. Its residues are rich in carbohydrates but poor in protein and account for approximately 55-60% of the raw weight of the fruit. Present study assessed the chemical composition and anti-oxidative activity of Kinnow mandarin fruit waste (KMW) and scrutinized the impact of dietary incorporation of variable levels of KMW on in vitro dry matter digestibility (IVDMD). Materials and Methods: Sun dried and ground KMW was analyzed for proximate composition, fibre fractions and calcium and phosphorus content. Antioxidant potential of KMW as total phenolic count and 1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity was assayed in an alcoholic extract of KMW. The effect of inclusion of KMW at variable levels (0-40%) in the isonitrogenous concentrate mixtures on in vitro degradability of composite feed (concentrate mixture:Wheat straw; 40:60) was also carried out. Results: KMW after sun-drying contained 92.05% dry matter. The crude protein content of 7.60% indicates it being marginal in protein content, whereas nitrogen free extract content of 73.69% suggests that it is primarily a carbonaceous feedstuff. This observation was also supported by low neutral detergent fiber and acid detergent fiber content of 26.35% and 19.50%, respectively. High calcium content (0.92%) vis-à-vis low phosphorus content (0.08%), resulted in wide Ca:P ratio (11.5) in KMW. High anti-oxidative potential of KMW is indicated by total phenolic content values of 17.1±1.04 mg gallic acid equivalents/g and DPPH free radicle scavenging activity 96.2 μg/ml (effective concentration 50). Mean IVDMD% of all the composite rations was found to be comparable (p>0.05) irrespective of the level of KMW inclusion, indicating no negative effect of KMW inclusion on in vitro nutrient utilization. Conclusion: KMW is a carbonaceous feedstuff and may be incorporated in ruminant ration up to the level of 40% (w/w basis) without affecting in vitro degradability.