In vitro and in vivo evaluations of wine lees as feeds for ruminants: Effects on ruminal fermentation characteristics, nutrient digestibility, blood metabolites and antioxidant status

Wine lees are by-products of wine-manufacturing, but the usefulness as animal by-product feed has not yet been revealed. The present study was aimed to investigate the usability of wine lees as feed for ruminants in fattening conditions by in vitro and in vivo trials. In in vitro experiments (in vitro I and II), the following four treatments were prepared: 100% dry matter (DM) rolled barley as a control (WL0), and replaced 7.5% DM, 15.0% DM, and 22.5% DM of wine lees as three treatments (WL7.5, WL15, WL22.5, respectively). A linear decrease in gas production was observed at 48 h after incubation with an increase in the percentage of wine lees in the substrate (P < 0.01). The DM and crude protein (CP) digestibility were linearly decreased with wine lees inclusion (P < 0.01), while neutral detergent fiber expressed exclusive of residual ash (NDFom) digestibility was linearly increased (P < 0.05). The polyphenolic contents and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability of fermented residue were linearly increased with wine lees inclusion (P < 0.01 and 0.05, respectively). The proportion of α-linolenic acid and total polyunsaturated fatty acids (PUFA) in the residues after incubation was linearly increased with wine lees inclusion (P < 0.01). Additionally, in in vivo experiment, four cannulated wethers were used in a 4 × 4 Latin square design experiment and each wether was assigned to one of the following feeding treatments: C, basal concentrate without wine lees; L, 6.7% DM of concentrate was replaced with wine lees; M, 13.3% DM of concentrate was replaced with wine lees; H, 20.0% DM of concentrate was replaced with wine lees. The apparent digestibilities of DM, CP, and NDFom did not differ among the treatments (P > 0.05). As wine lees increased, the proportion of ruminal propionate at 4 h after feeding and plasma malondialdehyde, which is one of the oxidative stress markers, were decreased (P < 0.05), and inorganic phosphorus concentration in plasma was increased (P < 0.05). No significant difference was observed in the nitrogen balance between the treatments. Conclusively, the wine lees substituted for the fattening ration up to 20% DM had no adverse effects on apparent digestibility, ruminal fermentation, and nitrogen balance and decreased an oxidative stress marker in plasma in vivo. Although the gas production and DM and CP digestibility were decreased in vitro, wine lees inclusion protected PUFA from ruminal biohydrogenation during ruminal fermentation. Thus, wine lees have a potential to be an important alternative as a partial substitute for antioxidant products.