Effects of Coix seed polyphenol extract on rumen fermentation, milk production, fatty acid profile, antioxidant activity, and polyphenol content in dairy goats

The transfer of natural antioxidants from feed to milk has become a research hotspot. Polyphenols are a source of potent natural antioxidants that may play important roles in improving antioxidant activity and milk quality in dairy goats. The aim of this study was to evaluate the effects of polyphenol-rich Coix seed extract (CSE) on rumen fermentation, milk production, fatty acid profile, antioxidant activity, and polyphenol content in milk from lactating dairy goats. Forty dairy goats were allocated to 4 treatments, and the treatments containing 0, 1.5, 3.0, or 4.5 g of CSE per kg of total mixed ration. The results indicated that the ruminal fluid total volatile fatty acid level increased linearly and quadratically, the acetic acid concentration and acetate:propionate ratio decreased quadratically, and the propionic acid level increased quadratically with increasing CSE concentration. An increase in dietary CSE linearly and quadratically increased milk production parameters, and quadratically increased milk protein, lactose, and solids-not-fat. The concentrations of C18:3n-3, C20:3n-3, and C22:5n-3 in milk were affected by the treatment, and increased quadratically, whereas those of C18:2n-6c, C20:3n-6, and C20:4n-6 decreased quadratically with increasing CSE. An increase in the concentration of CSE in the diet linearly and quadratically increased 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity in plasma and total antioxidant capacity (TAC) and catalase (CAT) activities in milk. The levels of gallic acid, protocatechuic acid, catechin, apigenin, kaempferol, and bergapten in milk were affected by the treatment, and linearly and quadratically increased with increasing dietary CSE levels. Significant positive correlations were detected between TAC, CAT, and DPPH scavenging activity and gallic acid, protocatechuic acid, apigenin, kaempferol, and bergapten, and positive correlations were detected between CAT and DPPH scavenging activity and catechin concentration in milk. In addition, significant positive correlations were detected between DPPH scavenging activity in plasma and TAC, DPPH scavenging activity in milk. Taken together, these findings indicate that dietary supplementation with CSE appears to be a promising strategy for improving the production performance of lactating dairy goats. Overall, the appropriate supplemental level of CSE was 1.5 g/kg in dairy goats under the conditions of the current experiment.