Abstract: 【Objective】 The aims of the present study were to investigate the effect of dietary phosphorus level on the performance and phosphorus excretion to environment in lactating cows. 【Method】 Thirty lactating Chinese Holstein cows were randomly allocated respectively into 3 treatments with 10 duplicates each. The phosphorus contents in the dietary of each treatment were 0.32%, 0.44% or 0.56% (dry matter basis), respectively. The trial lasted 75 days with 15-d adaptation period and 60-d experimental period. Samples were collected in the last 5 days. 【Result】Dietary phosphorus level of dairy cows showed no effects on the dry matter intake, milk yield and milk composition (P＞0.05). The contents of calcium, phosphorus, alkaline phosphatase and hydroxyproline in the serum and the saliva phosphorus content were all in the normal range. Daily phosphorus excretion to the environment through manure and urine of group fed diet with 0.32% P was decreased by 20.40 g and 45.84 g compared with the group fed diet with 0.44% P and 0.56% P, respectively. Fecal water-soluble phosphorus emissions from dairy cow fed diet with 0.32% P was respectively decreased by 15.24 g (P＜0.01) and 45.61 g (P＜0.01) compared with that fed diet with 0.44% P and 0.56% P. The daily feeding cost was respectively decreased by 0.60 yuan/cow and 0.40 yuan/cow. 【Conclusion】Therefore, dietary phosphorus level was 0.32% (dry matter basis) not only had no negative effect on the performance, but also significantlly decreased the fecal phosphorus excretion and improved economic benefit and ecological benefit of feeding. The recommended dietary allowance of phosphorus is 0.32%-0.44%.

Key words: phosphorus, lactating cow, performance, phosphorus excretion