Influence of L-threonine Supplementation on Goblet Cell Numbers, Histological Structure and Antioxidant Enzyme Activities of Laying Hens Reared in a Hot and Humid Climate

1. A previous experiment in our laboratory found that L-threonine supplementation at 0.2 and 0.3% increased egg production and the concentration of serum IgG, respectively. The objective of this current trial was to determine if both supplementation levels can positively influence histological structure, goblet cell numbers, or antioxidant enzyme activities. 2. Babcock Brown layers (n=576), 40 weeks of age, were allocated to three treatment groups, each of which included 6 replicates of 32 hens. Each group received the same basal diet formulated with maize, peanut meal and crystalline amino acids. L-threonine was added to the basal diet at 0 (control), 0.2, and 0.3%, respectively for 8 weeks. Chemical analysis of the diets for threonine values were 0.47, 0.66 and 0.74 %, respectively. 3. The numbers of goblet cells did not change due to L-threonine supplementation. Also, L-threonine had no affect on the villus height and mucosal thickness. No differences were found due to treatments among groups in the activity of alkaline phosphatase (ALP) in jejunum or ileum. L-threonine supplementation at 0.2% maximised the concentration of superoxide dismutases (SOD) in both serum and liver. 4. In conclusion, L-threonine supplementation had no affect on gut morphology but may have an antioxidant function at 0.2%.