Composition, preservation and digestibility by sheep of wet by-products from the food industry

• Aspergillus residue and soy okara are highly digestible by sheep.
• Aspergillus residue has high aerobic stability unlike soy okara.
• Pomegranate pulp has restricted consumption and low digestibility by sheep.
• Grape and avocado pulps have low digestibility by sheep and low stability.

This study examined the chemical composition, in vitro and in vivo digestibility, aerobic stability and ensiling capability of the fresh wet fibrous by-products Aspergillus residue, soy pulp (okara), pomegranate pulp, grape pulp and avocado pulp. Ensiling was assessed in glass silos, and aerobic stability in open PVC containers. Intake and in vivo digestibility were measured in mature male Assaf lambs (four lambs/replicates per dietary treatment) held in individual metabolic cages, and ad libitum-fed one of the total mixed rations containing the examined fresh by-product and appropriate supplement. Aspergillus residue is an acidic, fibrous by-product, characterized by high in vivo digestibility of organic matter (OM, 0.85) and neutral detergent fiber (NDF, 0.95), and high stability under aerobic exposure. Ensiling results give large dry matter (DM) losses (41.2%) and continuous yeast fermentation to ethanol and volatiles. Okara is an acidic, fibrous by-product that is rich in protein (290 g/kg DM), characterized by high in vivo digestibility of OM and NDF (0.88 and 0.93, respectively), but low stability under aerobic exposure. It can be ensiled with moderate DM losses (16%), producing butyrate and acetate. Pomegranate pulp contains high levels of soluble phenolics and sugars and its voluntary consumption by sheep is low. When fed to sheep it is characterized by low in vivo OM and NDF digestibility (0.44 and 0.20, respectively), and low aerobic stability. However, it can be ensiled with moderate DM losses (20%). Grape is rich in ethanol and avocado pulps in fat content, and both byproducts are rich in lignin content and therefore have low in vivo OM digestibility (0.30 and 0.43, respectively) originating from their low NDF digestibility (0.12 and 0.31, respectively). These by-products are characterized by low stability under aerobic exposure. Both by-products can be ensiled without any DM losses or NDF solubilization.