Soybean isoflavones (SIFs), a group of secondary metabolites, have antioxidant, anti-inflammatory, and hormone-like activities. Supplementation with SIFs in the diet was reported to promote lactation performance in ruminants. The present study was performed to further decipher the effect of various concentrations of SIFs on growth and slaughter performance, serum parameters, meat quality, and ruminal microbiota in fattening goats. After a two-week acclimation, a total of 27 5-month-old Guanzhong male goats (18.29 ± 0.44 kg) were randomly assigned to control (NC), 100 mg/d SIF (SIF1), or 200 mg/d SIF (SIF2) groups. The experimental period lasted 56 days. The weight of the large intestine was greater (p < 0.05) in the SIF1 and SIF2 groups compared with the NC group. Meat quality parameters indicated that SIF1 supplementation led to lower (p < 0.05) cooking loss and shear force (0.05 < p < 0.10). The 16S rRNA sequencing analysis demonstrated that SIF1 supplementation led to lower (p < 0.05) proportions of Papillibacter and Prevotellaceae_UCG-004 but greater (p < 0.05) CAG-352 abundance in the rumen; these responses might have contributed to the improvement in production performance. In conclusion, meat quality and ruminal microbiome could be manipulated in a positive way by oral supplementation with 100 mg/d of SIFs in fattening goats. Thus, this study provides new insights and practical evidence for the introduction of SIFs as a novel additive in goat husbandry.

Lactoferrin (LF) is believed to be an important active protein in goat milk, which plays an anti-inflammatory role. Although LF has been reported to be associated with body health, its exact underlying mechanism remains unclear. Here, we aimed to elucidate the mechanism of this anti-inflammatory effect of LF in vitro. We first identified that miR-214-5p inhibited the expression of LF mRNA and protein in cells through the 3′UTR of LF mRNA. We next identified the alterations in miRNA following LF overexpression in goat mammary epithelial cells (GEMCs). Overexpression of LF significantly increased (p < 0.05) miR-224-5p expression. We further revealed that transcriptional activation of ADAM17, TNF-α, IL-1β, and IL-6 was efficiently decreased (p < 0.05) in GMECs treated by miR-224-5p mimic. Conversely, knockdown of miR-224-5p increased (p < 0.05) ADAM17, TNF-α, IL-1β, and IL-6 expression. Additionally, TNF-α, IL-1β, and IL-6 expression levels were dramatically decreased in GMECs after administration of siADAM17. Herein, we indicate that the miR-214-5p/LF/miR-224-5p/ADAM17 axis is involved in the immune regulation of GEMCs.