Abstract
OBJECTIVE: This study was conducted to evaluate the effect of dietary supplementation of vitamin A (VA) on the tibial growth, calcium (Ca) and phosphorus (P) metabolism, VA, and vitamin D (VD) deposition, and associated gene expression in goslings. METHODS: A total of 180 healthy, 1-day-old male goslings were randomly divided into 3 treatment groups (0, 9,000, and 15,000 IU VA/kg), with 6 replicates containing 10 goslings each. They were weighed and sampled on days 14, 28, 42, 56, and 70. RESULTS: No addition of VA reduced VA content in the serum and liver of goslings, and supplementation of 15,000 IU/kg VA increased VA content from day 14 (p<0.05). The trend of VA concentration in the serum and liver was in line with the relative mRNA expression of retinoic acid receptor β in the jejunal mucosa. In both no addition of VA and supplementation of 15,000 IU/kg VA reduced 25-hydroxycholecalciferol (25-OH-VD3) content in the serum and VD content in the liver (p<0.05). From day 28, no addition of VA or supplementation of 15,000 IU/kg VA had a negative effect on tibia length, strength, and Ca, P, and ash content in goslings (p<0.05). Tibia P content was lower in the supplementation of 15,000 IU/kg VA group than in the no addition of VA group (p<0.05). No addition of VA or supplementation of 15,000 IU/kg VA had the most effect on early serum parathyroid hormone (PTH) levels in goslings (p<0.05). The effect of no addition of VA on the bone Gla protein (BGP) content of goslings started from day 14 (p<0.05). The relative mRNA expression of bone Gla-protein (BGLAP) and bone morphogenetic protein 4 (BMP4) in the liver and jejunal mucosa was decreased by either no addition of VA or supplementation of 15,000 IU/kg VA (p<0.05). CONCLUSION: Both no addition of VA and supplementation of 15,000 IU/kg VA affected the mineralization process of the bone, and ultimately reduced tibial quality.