Effects of Glycine Supplementation in Drinking Water on the Growth Performance, Intestinal Development, and Genes Expression in the Jejunum of Chicks

SIMPLE SUMMARY: The objective of this study was to investigate the effects of glycine supplementation in drinking water on the growth performance and intestinal development of newborn chicks. Parameters such as body weight, organ indexes, intestinal villus development, and the expression of genes in the intestine were assessed. The findings revealed that glycine supplementation in drinking water resulted in an increase in the average daily gain (ADG) of chicks aged 7 to 14 days. An increase in jejunum villus height and the ratio of villus height to crypt depth was also observed, which could be considered the possible factor contributing to the enhanced ADG. Furthermore, glycine supplementation in drinking water resulted in changes in the expression of a few genes related to mucosal immune barrier, cellular capacity against oxidation, and amino acid transporter in jejunum. These findings indicate that glycine supplementation in drinking water has the potential to enhance growth efficiency and promote intestinal health in chicks. ABSTRACT: Glycine, the most basic amino acid found in nature, is considered an essential amino acid for chicks. However, the precise understanding of high concentrations of glycine’s significance in promoting the growth performance of chicks, as well as its impact on intestinal development, re-mains limited. Consequently, the objective of this study was to investigate the effects of glycine supplementation in drinking water on growth performance, intestine morphology, and development in newly hatched chicks. In this study, 200 newly born chicks were selected and pro-vided with a supplementation of 0.5%, 1%, and 2% glycine in their drinking water during their first week of life. The results revealed that glycine supplementation in drinking water could significantly increase the average daily gain of chicks from days 7 to 14. Furthermore, a significant difference was observed between the group supplemented with 1% glycine and the control group. Concurrently, this glycine supplementation increased the villus height and the ratio of the villus height to crypt depth in jejunum on both day 7 and day 14. Glycine supplementation in drinking water significantly affected the mRNA expression level of the ZO-1, GCLM, and rBAT genes in jejunum, which may have certain effects on the mucosal immune defense, cellular antioxidant stress capacity, and amino acid absorption. Overall, the findings of this study indicate that glycine supplementation in drinking water can enhance the growth performance of chicks and promote their intestine development.