Dietary vitamin D3 requirement of magang goslings from 1–21 days of age

The present study was conducted to investigate the effect of dietary vitamin D₃ levels (0, 200, 400, 800, 1600, and 3200 IU/kg) on growth performance, calcium-phosphorus metabolism, and tibia development of goslings from 1 to 21 days of age. A total of 720 one-day-old Magang male goslings with similar initial body weight were randomly divided into 6 treatments with 6 replicates per treatment and 20 geese per replicate. The goslings fed with 400 IU vitamin D₃/kg of diet obtained the maximum average daily gain, while vitamin D₃ supplementation significantly improved the feed/gain of goslings aged from 1 to 21 days (P < 0.05). The vitamin D₃ requirement of gosling aged from 1 to 21 days for optimal feed/gain ratio and average daily gain were estimated from three regression models (one-slope straight, two-slope straight, and quadratic broken-line model) to be 246–352 IU/kg diet and 400–518 IU/kg diet, respectively. Serum calcium and phosphorus contents, parathyroid hormone level, and 25-hydroxycholecalciferol level responded to increasing dietary vitamin D₃ levels (P < 0.05) and reached a plateau at 800, 0, and 200 IU vitamin D₃/kg diet, respectively. The mRNA expressions of target genes related to calcium homeostasis such as vitamin D₃ receptor, Na⁺/Ca²⁺ exchanger 1, and plasma membrane calcium ATPase 1b in the duodenum and kidney (P < 0.05) and parathyroid hormone receptor mRNA expression in the kidney (P < 0.05) were increased linearly and quadratically with the increasing dietary vitamin D₃ levels, respectively. Graded doses of dietary vitamin D₃ from 0 to 3200 IU/kg produced linear responses in tibial density (P < 0.05). The vitamin D₃ requirement of gosling aged from 1 to 21 days ranged from 519 to 698 IU/kg diet when tibial density as an evaluation criterion. In conclusion, the vitamin D₃ requirement of gosling aged from 1 to 21 days for optimal growth performance (feed/gain and average daily gain) and tibial density was estimated to be 246–352 IU/kg of diet, 400–518 IU/kg of diet, and 519–698 IU/kg of diet based on three regression models (one-slope straight, two-slope straight, and quadratic broken-line model), respectively. The most appropriate vitamin D₃ requirement was recommended at 602 IU/kg of diet of young geese based on the mean estimated values of three regression models for the tibial density with the highest coefficient of determination and lowest mean square error.