Effects Of Taurine On Growth Performance, Histopathology And Intestinal Health Of Weaned Piglets

Taurine (Tau) has been extensively developed in the animal industry as an essential functional feed additive. However, the studies of Tau supplementation on pigs were minimal and controversial, and less is known about the impact of Tau at high levels of intake on piglet health and performance. Therefore, it is necessary to assess the safety limit of Tau to avoid potential danger and to make full use of Tau. This study was conducted to investigate the effects of dietary Tau supplementation on growth performance and health of weaned pigs, and to evaluate whether Tau could have negative effects on piglet health as well as the possible mechanisms. A total of ninety six 28-d old barrows weaned at 21±2 d (Duroc x Landrace x Yorkshire; initial average BW= 7.39±0.40 kg) were allotted randomly on the basis of the initial body weights (BW) to 4 treatments, consisting of formulated Tau supplementation of 0,0.3,1.5, and 3%. Each treatment had 6 replicate pens, and each pen had 4 pigs. The experimental period lasted 28 d. In the morning of d 29,1 pig with a close average BW per pen was selected for bleeding via the jugular veins under fasting for 12 h and blood samples were collected. After the blood collecting, these pigs were slaughtered. The results were as follows:(1) Dietary supplementation with 3% Tau decreased F/G (d 1 to 14 and d 1 to 28) compared with the control diet (P< 0.05). F/G (d 1 to 14, d 15 to 28 and d 1 to 28) was higher (P< 0.05) in pigs fed 3% Tau diets compared with those fed 0.3% Tau (P< 0.05).(2) Dietary supplementation with 0.3% Tau decreased the diarrhea index by 29% (P< 0.05) compared with the control diet. However, dietary supplementation with 1.5 and 3% Tau increased the diarrhea index by 55 and 88%(P< 0.05), respectively, compared with the control diet.(3) The AST levels were higher (P< 0.05) in pigs fed 1.5 and 3% Tau than those fed 0.3% Tau. The concentrations of serum Tau were higher (P<0.05) in pigs fed 1.5 and 3% Tau than those fed 0 and 0.3% Tau. Pigs fed diets with 3% Tau had higher concentrations of serum Met than did pigs fed other diets (P< 0.05).(4) Dietary supplementation with 3% Tau increased the levels of MDA in the serum and liver, decreased the activity of SOD in the serum, the activities of GSH-Px and T-AOC in the liver compared with 0.3% Tau diet (P< 0.05). Compared with the control diet, dietary supplementation with 0.3% Tau increased the activities of SOD in the serum and liver, and increased the activities of GSH-Px and T-AOC in the liver (P< 0.05). However, dietary supplementation with 1.5% Tau increased the activity of SOD in the serum and the level of MDA in the liver (P< 0.05), dietary supplementation with 3% Tau increased the level of MDA in the liver (P< 0.05).(5) Livers, cerebrums, kidneys and spleens of pigs fed diets with 0 and 0.3% Tau had normal histological structure. Dietary supplementation with 1.5% Tau resulted in mild swelling of livers. Dietary supplementation with 3% Tau resulted in severe swelling of livers, mild engorgement of some cerebrums and kidneys.(6) Dietary supplementation with 0.3% Tau increased (P< 0.05) villus heights in jejunum and ileum compared with the control diet. However, dietary supplementation with 3% Tau decreased villus height in duodenum and increased crypt depths in jejunum and ileum compared with the control diet (P< 0.05). In addition, Pigs fed diet with 3% Tau had lower (P< 0.05) villus heights and deeper (P< 0.05) crypt depths in duodenum, jejunum, and ileum than did pigs fed 0.3% Tau.(7) Dietary supplementation with 0.3% Tau decreased mucosal TNF-a levels in the duodenum and mucosal Caspase-3 expression levels in the jejunum, and increased mucosal GLP-2 levels in the duodenum compared with control diet (P< 0.05). Dietary supplementation with 3% Tau increased mucosal IL-6 and TNF-a levels in the jejunum and ileum, mucosal Caspase-3 levels in the duodenum and jejunum, and mucosal Caspase-3 expression levels in the duodenum and ileum compared with control diet(P<0.05). Dietary supplementation with 3% Tau increased mucosal IL-6, TNF-α and Caspase-3 levels in the duodenum, jejunum and ileum, decreased mucosal GLP-2 levels in the duodenum and jejunum compared with 0.3% Tau diet (P< 0.05). Dietary supplementation with 3% Tau increased mucosal IL-6, Caspased-3 levels in the duodenum, mucosal TNF-a levels in the ileum, and mucosal Caspase-3 expression levels in the duodenum, jejunum and ileum compared with 1.5% Tau diet (P< 0.05).In summary, the conclusions of this study were as follows:(1) Appropriate (0.3%) Tau supplementation in diets had certain degrees of beneficial effects on piglet growth and health. Dietary supplementation 1.5% Tau could increase diarrhea index and induce mild liver damage. Excessive (3%) Tau could increase F/G and diarrhea index, had adverse effects on intestinal health, and induce the damage of liver, cerebrums, kidneys etc., which was related with higher oxidative stress and toxic effects.(2) In our study, the safety dietary Tau supplementation was 0.3%.(3) Excessive Tau supplementation augmented inflammatory cytokines (IL-6 and TNF-a) and Caspase-3 release, upregulated Caspase-3 gene expression and abated GLP-2 secretion, which may contribute to toxic effects on intestinal functions in weaned pigs.