Abstract
A dose-response experiment assessing 6 total dietary vitamin A (VA) levels (0, 3,000, 6,000, 9,000, 12,000, and 15,000 IU/kg) was conducted to study the effects of different levels of VA on growth performance and bone indexes of 0 to 28 d goslings. A total of 360 healthy 1-day-old goslings with similar body weights were randomly divided into 6 groups with 6 replicates in each group and 10 goslings in each replicate. The experiment duration was 28 d. The experimental results showed that the VA content in the serum and liver of gosling increased with increasing VA amount (P < 0.05). When the diet was supplemented with 9,000 IU/kg VA, the content of vitamin D in serum and the liver was higher than those in other groups (P < 0.05). The 28-day body weight and average daily gain in gosling in the 9,000 IU/kg VA group were higher than those in the 0, 3,000 and 15,000 IU/kg VA groups (P < 0.05). Growth hormone, thyroxine, and parathyroid hormone levels in the 9,000 IU/kg VA group were higher than those in the 0, 3,000, 6,000 and 15,000 IU/kg VA groups (P < 0.05). The insulin level in the 9,000 IU/kg VA group was higher than those in the other groups (P < 0.05). The osteocalcin (BGP) levels in the VA supplementation groups were higher than that in the no VA groups (P < 0.05). The tibia length and phosphorus content in the 9,000 IU/kg VA group were higher than those in the 12,000 IU/kg VA group and 15,000 IU/kg VA group (P < 0.05). The tibia shear hardness values in the 6,000, 9,000 and 12,000 IU/kg VA groups were higher than those in the 0, 3,000 and 15,000 IU/kg VA groups (P < 0.05). The tibia calcium content in the 9,000 IU/kg VA group was higher than those in the 0 and 15,000 IU/kg VA groups (P < 0.05). The tibia crude ash content in the 9,000 IU/kg VA group was higher than that in the 15,000 IU/kg VA group (P < 0.05). In conclusion, the optimum dietary VA supplementation for 0- to 8 day gosling was 9,000 IU/kg.