Piglet weaning is an important stage in production where changes in the environment and diet can cause problems such as intestinal inflammation and diarrhea. Vitamin A is an essential nutrient for human and animal growth and has immunomodulatory and inflammatory effects. A large body of literature has previously reported on the use of vitamin A in piglet production, so our experiment added different concentrations of vitamin A (0, 1100, 2200, 4400, 8800, and 17,600 IU/kg) to weaned piglet diets to study the effects of different doses on growth performance, intestinal barrier, inflammation, and flora in weaned piglets. We selected 4400 IU/kg as the optimum concentration of vitamin A in relation to average daily weight gain, feed intake, feed-to-weight ratio, and diarrhea rate, and subsequently tested the inflammatory factors, immunoglobulin content, antioxidant levels, and intestinal flora of weaned piglets. Results: We observed that the diarrhea rate of weaned piglets was significantly lower after the addition of 4400 IU/kg of vitamin A to the diet (p < 0.05). A control group and a 4400 IU/kg VA group were selected for subsequent experiments. We found that after the addition of vitamin A, the serum CAT level of weaned piglets increased significantly, the expression of Claudin-1 in the jejunum and ileum increased significantly, the expression of Occludin gene in the jejunum increased significantly, the expression of IL-5 and IL-10 in the ileum increased significantly (p < 0.05), and the expression of IL-4, IL-5, and IL-10 in the ileum increased significantly (p < 0.05). Meanwhile, in the colonic flora of vitamin A-added weaned piglets, the relative abundance of Actinobacteria and Erysipelotrichales decreased significantly, while the relative abundance of Bacteroidales increased significantly (p < 0.05). The results of this study indicated that vitamin A at 4400 IU/kg reduces diarrhea in weaned piglets by increasing antioxidant levels, increasing intestinal tight junction protein gene expression, and regulating colonic gut microbiota.

Transport stress prior to slaughter frequently induces a stress response, negatively affecting meat quality. This study investigated the impact of dietary potassium magnesium sulphate (PMS) supplementation during the fattening stage on the stress response and meat quality in finishing pigs subjected to transport stress. The experiment involved two phases. Initially, 48 finishing pigs (68.00 ± 0.40 kg) were randomly allocated into two groups: a control group receiving a basal diet (CON) and a PMS-supplemented group receiving the basal diet with 0.50% PMS. Each group was housed in six pens, with four pigs per pen. After 60 days of feeding, in the second phase, two pigs from each pen were randomly selected for slaughter, with one pig subjected to a 4 h transportation stress prior to slaughter. Pigs were categorized into four treatment groups based on diet and stress: (1) control without transport stress, (2) control with transport stress, (3) PMS-supplemented without transport stress, and (4) PMS-supplemented with transport stress. Serum, jejunum, and longissimus thoracis muscle (LM) samples were collected. The results indicated that dietary PMS supplementation did not significantly affect growth performance during the fattening stage (p > 0.05). However, following transport, the PMS pigs showed a reduction in norepinephrine and cortisol concentrations (p = 0.09, p < 0.05) and a significant increase in serum glutathione peroxidase (GSH-Px) activity (p < 0.05). Furthermore, PMS supplementation significantly increased serum catalase (CAT), total antioxidant capacity (T-AOC), alkaline phosphatase (AKP) activity, and high-density lipoprotein cholesterol (HDL-C) levels (p < 0.05), while significantly reducing cholesterol (CHO) levels (p < 0.05). Transport stress adversely affected the intestinal health of finishing pigs, as evidenced by a decrease in intestinal villus height (0.05 < p < 0.1), a condition ameliorated by PMS supplementation. Additionally, transported pigs exhibited a higher drip loss_24h in LM (p < 0.05), which was also alleviated through PMS supplementation. In conclusion, PMS supplementation mitigates transport stress and improves meat quality in finishing pigs.