不同泌乳阶段奶牛饲料中N、P、Ca的生物学利用率研究

试验选用体况、胎次、产奶量相近的中国荷斯坦新产牛和泌乳高峰牛各6头,分别在第0 d、5 d、10 d测定（估测）各生理阶段奶牛产奶量、饲料采食量和粪尿排放量,同时,采集其饲料、牛奶、粪便和尿样进行N、P、Ca百分含量测定,通过分析饲料、牛奶、粪便和尿中N、P、Ca含量,计算出各泌乳期奶牛N、P、Ca的生物学利用率。结果表明,新产牛对N、P、Ca的表观吸收率分别为77.21%±1.91%、56.08%±8.22%和47.62%±7.47%,表观存留率分别为15.6%±9.70%、12.38%±12.07%和32.5 2%±7.93%;泌乳高峰牛对N、P、Ca的表观吸收率分别为76.37%±3.08%、60.15%±8.54%和49.58%±9.89%,表观存留率分别为18.26%±6.35%、23.65%±9.57%和36.56%±10.96%。新产牛对N、P、Ca的表观吸收率与泌乳高峰牛对N、P、Ca的表观吸收率之间均无显著差异（P〉0.05）,而对N、P、Ca的表观存留率,泌乳高峰牛均高于新产牛。

Evaluation of N, P, Ca Metabolism in Transition and Peak Dairy Cows

In this experiment,six high-yield Holstein cows and six transition cows which were close in body condition,births and milk yield were chosen.Determine their milk yield,feed intake,urine and faces amount in different lactation stages which are 0 d,5 d,and 10 d.Meanwhile,collect their forage,milk,urine and faces and determine the N,P and Ca content in specimens.Figure out the Biological Value of N,P and Ca by analyzing specimens＇ content.This experiment provided direction for milk produce,veterinary and animal husbandry.The result indicated that early postpartum cows′ apparent absorptive of N,P and Ca werre 77.21 %± 1.91 %,56.08 %±8.22 % and 47.62 %±7.47 % while apparent retention rate are 15.6 %±9.70 %,12.38 %±12.07 % and 32.52 % ±7.93 %.The high-yield cows′ apparent absorptive of N,P and Ca are 76.39 %±3.08 %,60.15 %±8.54 % and 49.58 %± 9.89 % while apparent retention rate were 18.26 %±6.35 %,23.65 %±9.57 % and 36.56 %±10.96 %.There was not remarkable difference between apparent absorptive of N,P and Ca of early postpartum cows and high-yield cows.The apparent retention rate of N,P and Ca of high-yield cows was higher than that of early postpartum cows.