Effects of short-term tryptophan supplementation in late-pregnant sows on reproductive performance and piglet growth.

Proper nutrition in late pregnancy is crucial for postpartum recovery and piglet growth. Improper management can lead to various physiological stresses in sows, resulting in reduced reproductive performance. This study aimed to assess the potential benefits of short-term supplementation with tryptophan on late-pregnant sows, fed from day 99 to day 114 of gestation. We divided 21 Landrace hybrid sows into three groups. The control group was fed a basal diet, while the experimental groups were fed basal diets supplemented with 0.1 % and 0.2 % tryptophan, respectively. Results indicated that feeding 0.1-0.2 % tryptophan had no significant effect on sows' glucose and lipid metabolism. However, compared to the control group, tryptophan supplementation significantly increased reproductive hormone (E2) levels in sows, with no significant impact on immune function and oxidative status. Furthermore, sows showed significant improvements in reproductive performance after tryptophan supplementation, particularly in weaning survival rate, and average litter weight at birth,. Further investigation revealed that tryptophan supplementation significantly increased melatonin levels in sows. Given melatonin's beneficial effects on mammalian reproductive activity, it is inferred that these effects are partly mediated by tryptophan derived melatonin. In conclusion, supplementation with tryptophan in late pregnancy positively influences reproductive activity in sows and the growth of newborn piglets. Due to the limitation of sample size, these effects are only preliminary assessments. In the future, we will expand the sample size and further explore its mechanism.