饲粮不同采食水平下肉羊氮沉积和尿中嘌呤衍生物排出规律的研究

本试验旨在研究饲粮不同采食水平下肉羊氮沉积和尿中嘌呤衍生物(PD)的排出规律.试验选用12只平均体重为(41.3±2.8)kg的杜寒杂交绵羊公羔,随机平均分为3组,按照自由采食、自由采食量的70％和自由采食量的40％3个干物质采食水平饲喂,试验期为12d,其中预试期7d,正试期5d.结果表明:随着饲粮采食水平的降低,营养物质消化率均显著上升(P＜0.05),粪氮和尿氮排出量均显著降低(P＜0.05),沉积氮与摄入氮之间存在线性相关(R2=0.92).尿中PD排出量和微生物氮(MN)产量均随采食水平的降低而显著降低(P＜0.05),嘌呤氮指数(PNI)与氮沉积率和氮吸收率均表现出相同变化趋势.由此可见,PD排出量与可消化有机物采食量(DOMI)以及MN产量之间均存在线性相关,相关方程分别为y=21.41X-1.81(R2=0.94)和Y=0.91X+2.57(R2=0.94)；PNI能够将氮平衡和PD排出量有机结合起来,用于评价饲粮氮的利用效率.

Nitrogen Retention and Urinary Excretion of Purine Derivatives of Mutton Sheep at Different Levels of Feed Intake

This experiment was aimed to investigate N retention and urinary excretion of purine derivatives(PD) of mutton sheep at different levels of feed intake.Twelve Dorper thin-tailed Han crossbred,non-castrated male lambs with an average bodyweight of(41.3 ± 2.8) kg were randomly assigned to three levels of dry matter intake: ad libitum intake,70% of the ad libitum intake,and 40% of the ad libitum intake.The experiment lasted for 12 days(7 days for adaptation and 5 days for trial period).The results showed that the nutrient digestibility was significantly increased with decreasing feed intake(P<0.05),whereas both fecal and urinary N excretion were significantly decreased with decreasing feed intake(P<0.05).A linear relationship was found between N retention and N intake(R2=0.92).With the reduction of feed intake,urinary excretion of PD as well as microbial N(MN) yield were significantly decreased(P<0.05).Purine nitrogen index(PNI) showed the same trend as N retention and N absorption.In conclusion,there are linear equations between urinary PD excretion,digestible organic matter intake(DOMI) and also MN yield.The equations are Y=21.41X-1.81(R2=0.94) and Y=0.91X+2.57(R2=0.94),respectively.The combination of both N balance and PD excretion can be expressed as PNI,which can be used to evaluate utilization of dietary nitrogen.