Green tea extract complex as a phytogenic supplement to reduce bile salt hydrolase activity and enhance growth performance in weaning pigs.

The postweaning period is stressful for pigs due to changes in their environment and diet. The occurrence of diarrhea at this stage is high. Growth promoters such as antibiotics and zinc oxide (ZnO) have been used not only to reduce postweaning diarrhea but also to improve the growth performance of weaning pigs. It has also been shown that the growth performance of pigs is negatively associated with bile salt hydrolase (BSH) in the gut. Antibiotic growth promoters (AGP) and ZnO administration have demonstrated effective inhibition of BSH, which is linked to enhanced growth performance in pigs. Therefore, this study evaluated the effects of a plant-based supplement, green tea extract, with butyric acid, and vitamin K (GBK), on growth performance, nutrient digestibility, fecal score, blood profile, and BSH activity of the gut microbiota of weaning pigs. Here, 192 crossbred weaning pigs [(Yorkshire × Landrace) × Duroc], aged 21 d, were subjected to a 4-wk-long feeding experiment. Pigs were divided into six treatments (n = 32 per treatment, 8 pens per treatment). After feeding, the average daily gain (ADG) and gain-to-feed (G:F) ratio improved linearly with GBK supplementation. During the feeding period, diarrhea was not observed in the treatment groups, and the fecal scores of the weaned pigs were not affected. Supplementation had no negative impact on the blood profile parameters of weaned pigs, including white blood cell count, red blood cell count, lymphocyte percentage, and blood urea nitrogen. Moreover, supplementation of GBK decreased the TNF-α and IL-6, while immunoglobulins (IgA, IgG) increased. In addition, GBK reduced the abundance of gut microbiota with BSH activity, including Clostridium sensu stricto 6, the Clostridia vadinBB60 group, Marvinbryantia, Muribaculaceae, and Enterococcus. Correlation analysis revealed that gut microbiota function related to secondary bile acid biosynthesis had a strong negative correlation with ADG, average daily feed intake, and G:F ratio of the pigs. The combination of green tea, butyric acid, and vitamin K is an effective alternative to AGP and ZnO for improving growth performance, feed efficiency, and diarrhea score of weaned pigs. In addition, this feeding strategy had a modulatory effect on the gut microbiome, altering BSH activity associated with improved growth performance in weaning pigs.