Mammary antioxidant status and inflammatory markers associated with oxidative stress are improved in lactating dairy goats fed alfalfa silage inoculated with Limosilactobacillus reuteri A4-2 with feruloyl esterase

Due to the ability to hydrolyze ferulic acid ester bonds in lignocellulose, feruloyl esterase-producing lactic acid bacteria (FLAB) have received special attention as silage inoculants. Free ferulic acid is a potent antioxidant but whether it can have such function in the mammary gland of lactating ruminants is unknown. This study investigated the effects of feeding alfalfa silage inoculated with FLAB on mammary gland and milk antioxidant activity, and mRNA abundance of genes associated with the antioxidant response and inflammation in lactating dairy goats. Alfalfa (Medicago sativa L.) was treated with control (CON) and one of Limosilactobacillus reuteri strains (YM13 and A4-2) at an application rate of 5 × 105 cfu/g fresh grass, respectively. Sampling was conducted on d 20, 40, and 60 of ensiling. In vitro DM digestibility of silage was analyzed using PROC MIXED (SPSS 21.0, SPSS, Inc., Chicago, IL, United States). After 1 mo of silage fermentation, a 60-d feeding experiment was conducted. Forty-two lactating dairy goats [days in milk (mean ± standard deviation; 53 ± 4); body weight (37.2 ± 2.3 kg)] were randomly assigned to 1 of 3 dietary treatments (n = 14/treatment) prepared with the above alfalfa silages. Composite samples of feed were taken weekly. Dairy goats were milked twice daily and milk samples were taken on d 58 to 60 of feeding period. Ruminal fluid samples were harvested on d 60 before the morning feeding. Five dairy goats from each group were slaughtered at the end of the experiment, and mammary gland tissue samples were collected for analyses. Data were analyzed using PROC GLM (SPSS 21.0, SPSS, Inc., Chicago, IL, United States). Compared with CON and YM13, the A4-2–treated silage had greater in vitro DM digestibility. Goats fed A4-2–treated silage-based diet had greater ruminal total volatile fatty acids and acetate, and mammary SOD, CAT, GPX activities and T-AOC concentration, but lower malondialdehyde (MDA) and nitric oxide (NO) concentrations as compared with CON and YM13. Compared with the milk from CON, feeding A4-2–treated silage-based diet resulted in greater milk activity of GPX and T-AOC concentration, and lower pro-inflammatory cytokine concentrations of IL-6 and TNF-γ. Compared with CON and YM13, overall mRNA abundance of NFE2L2, HMOX1, NQO1, SOD2, GPX1, GPX2, and GSR was greater in mammary tissue of goats fed A4-2–treated silage-based diet. However, the relative abundance of NFKB1, RELA, and TNF was lower due to feeding A4-2–treated silage-based diet compared with CON and YM13. In addition, goats fed A4-2–treated silage-based diet had greater mammary CAT but lower IFNG and NOX4 abundance compared with CON. Overall, feruloyl esterase-producing lactic acid bacteria used as silage inoculant shows a great potential in preventing mammary infections in lactating dairy goats induced by oxidative stress.