This experiment investigated the effects of different levels of bile acid (BA) additives in diets on the lactation performance, serum antioxidant metabolites, and serum biochemical indices of 60 multiparous mid-lactation dairy cows. The cows were randomized to receive one of the four homogeneous treatments, with the BA preparation supplemented at 0, 6, 12, and 18 g/head/d. The experiment lasted for 14 weeks. The first 2 weeks were the pre-feeding period. The milk yield and composition data were recorded weekly, and the dry matter intake and antioxidative blood index were analyzed on the 6th, 10th, and 14th weeks of the study. On the 84th day of the experiment, the experimental group exhibited significantly higher levels of total protein and albumin, by 57.5% and 55.6%, respectively, compared to the control group (p < 0.05). On both the 28th and 84th days of the trial, the experimental group showed a markedly higher lipase content compared to the control group, by 26.5% and 25.2%, respectively (p < 0.05). Furthermore, the experimental group displayed notably elevated levels of superoxide dismutase, glutathione peroxidase, and total antioxidant capacity, surpassing the control group by 17.4%, 21.6%, and 8.7%, respectively. In conclusion, BA additives improve the serum antioxidant indices of dairy cows, thereby enhancing the performance of these cows.

Glucose and amino acids are important sources of nutrients in the synthetic milk of dairy cows, and understanding the fate of amino acids is essential to optimize the utilization of amino acids in milk protein synthesis, thereby reducing nutrient inefficiencies during lactation. The purpose of this study was to investigate the effects of LPS and different concentrations of glucose on (1) the expression of inflammatory factors and genes, (2) the glucose metabolism, and (3) amino acid utilization in BMECs. The results showed that there was an interaction (LPS × glucose, p < 0.05) between LPS and glucose content in the inflammatory cytokine genes (IL-6 and TNF-α) and the inflammatory regulatory genes (CXCL2, CXCL8, and CCL5). With the addition of LPS, the HG + LPS group caused downregulated (p < 0.05) expression of IL-6 and TNF-α, compared with the LG + LPS group. Interestingly, compared with the LG + LPS group, the HG + LPS group upregulated (p < 0.05) the expression of CXCL2, CXCL8, and CCL5. LPS supplementation increased (p = 0.056) the consumption of glucose and GLUT1 gene expression (p < 0.05) and tended to increase (p = 0.084) the LDHA gene expression of BMECs under conditions of different concentrations of glucose culture. High glucose content increased (p < 0.001) the consumption of glucose and enhanced (p < 0.05) the GLUT1, HK1, HK2, and LDHA gene expression of BMECs with or without LPS incubation, and there was an interaction (LPS × glucose, p < 0.05) between LPS and glucose concentrations in GLUT1 gene expression. In this study, LPS enhanced (p < 0.05) the consumption of amino acids such as tryptophan, leucine, isoleucine, methionine, valine, histidine, and glutamate, while high levels of glucose decreased (p < 0.01) consumption, except in the case of tyrosine. For histidine, leucine, isoleucine, and valine consumption, there was an interaction (LPS × glucose, p < 0.05) between LPS and glucose levels. Overall, these findings suggest that relatively high glucose concentrations may lessen the LPS-induced BMEC inflammatory response and reduce amino acid consumption, while low glucose concentrations may increase the demand for most amino acids through proinflammatory responses.