Utilization of some fruit rinds in small ruminant feeding: nutritional characteristics determination

Every year, thousands of tons of fruit wastes are produced worldwide while most of them remain unused and are released into the environment. Incorporation of these wastes to feedstuffs reduces competition between food and feed, and reduces environmental risks or methane yield in ruminants. Nevertheless, no comprehensive research was available on the nutritional properties of rinds of different fruits in small ruminant feeding. Hence, this research investigates the nutritional potential of some fruit's rinds (Kiwi, Tangerine, Grapefruit, Sweet lemon, Sour lemon, Banana, Mango, Orange, Apple, Peach, and Persimmon) by in vitro ruminal-microbial and standard laboratory methods. Persimmon rind had the higher total phenolic contents (TPC, 22 mg gallic acid equivalents/g dry matter: DM) than the other treatments (P < 0.0001). The ether extract (EE), neutral detergent fiber (NDF), acid detergent fiber (ADF), and ash contents of banana rind were greater (P < 0.0001), however its DM, relative feed value (RFV), and non-fiber carbohydrates (NFC) were lower than the other treatments (P < 0.0001). A different range of minerals was observed among fruit rinds along with a higher content of potassium (42.5 g/kg DM) and manganese (49 mg/kg DM) in banana rind (P < 0.0001). Persimmon (45.7 ml/200 mg DM) and sweet lemon (75.7 ml/200 mg DM) rinds recorded the lowest and highest potential gas production, respectively (P < 0.0001). Persimmon exhibited a lower percentage of methane (11.5%) rather than other rinds (P < 0.0001). The total volatile fatty acids (TVFA) and metabolizable energy (ME) in sweet lemon, and dry matter digestibility (DMD) and organic matter digestibility (OMD) in tangerine were greater compared with other rinds. The rind of the banana exhibited the highest amounts of titratable acidity (283 mEq×10^- 3), acid-buffering capacity (200 mEq×10^- 3), and acid-base buffering capacity (260 mEq×10^- 3) (P < 0.0001). In conclusion, the present rinds differed in chemical-nutritional characteristics. These rinds may feed as a substitute for conventional forages in the diets of small ruminants on a large scale throughout the year; however, these in vitro findings need to be scientifically validated under in vivo experiments.