Abstract: 【Objective】The effects of photoperiod and melatonin on nitrogen partitioning in Inner Mongolia White Cashmere goats in telogen were investigated. 【Method】Eighteen castrated mature goats, 23-25 kg of liveweight, were divided into three groups randomly, which were treated with different photoperiods, in each of the groups half of the goats were implanted melatonin. Total deposited nitrogen (TN) was tested by general digestive and metabolism method. Body nitrogen deposited (BN) was measured by isotope dilution technique of tritiated water at the beginning and the end of the experiment, fur nitrogen deposited (FN) were calculated by FN= TN- BN. 【Result】Results showed that there was a significant difference in BN and FN partitioning. Hormones relative to nitrogen partitioning and body composition also varied with different treatments. As a result, there was a competitive nitrogen partitioning between body and fur regulated by hormones induced by photoperiod and implanted melatonin. Corresponding to increasing concentration of melatonin in goats blood, there was an additive cashmere in SDPP and implanted groups. Average cashmere production was 338.83±72 g in SDPP and implanted groups, increased by 73.86%. The length of the new grown cashmere was 5.95±0.26-6.32±0.22 cm, the diameter of new cashmere was 14.43±0.28-15.03±0.51 ?m, which was decreased by 0.1-0.71 ?m compared with the previous cashmere. Although cashmere break strength was reduced by 0.94-1.62 cN, it was still in the range of textile standard. Overall, the textile value of new cashmere was up to grade A, except only one group fall in grade B. 【Conclusion】This study has provided evidences that melatonin and photoperiod can be used to improve the cashmere production in practice, the technique can be extended in Inner Mongolia and other areas in north China.

Key words: Photoperiod, Melatonin, Cashmere goats, Nitrogen partitioning, Cashmere