饲粮蛋白质和脂肪水平对育成期雌性水貂生长性能、营养物质消化率及氮代谢的影响

本试验旨在探讨饲粮蛋白质和脂肪水平对育成期雌性水貂生长性能、营养物质消化率及氮代谢的影响,以确定育成期雌性水貂饲粮中蛋白质和脂肪的适宜水平。采用2×3因子试验设计,设32%(L)、36%(H)2个蛋白质水平与10%(L)、20%(M)、30%(H)3个脂肪水平,共配制6种试验饲粮。按照蛋白质和脂肪水平,将6种试验饲粮分别命名为LL、LM、LH、HL、HM和HH。选取90只60日龄健康雌性水貂,随机分成6组,每组15个重复,每个重复1只水貂。预试期7 d,正试期60 d。结果表明:LH组水貂末重和平均日增重均最高,显著高于LL和HL组(P0.05),并且随着饲粮脂肪水平的增加呈上升趋势。平均日采食量和料重比均以LH组最低;30%脂肪水平组水貂的平均日采食量极显著低于20%脂肪水平组(P0.01);料重比随着饲粮脂肪水平的增加而升高,30%脂肪水平组极显著低于10%和20%脂肪水平组(P0.01)。LL和HL组水貂的干物质消化率、脂肪消化率极显著低于其他组(P0.01);HH组水貂的蛋白质消化率显著高于LL、LH和HL组(P0.05)。随着饲粮蛋白质水平的增加,蛋白质消化率和脂肪消化率分别显著(P0.05)和极显著(P0.01)升高;10%脂肪水平组的干物质消化率和蛋白质消化率极显著低于20%和30%脂肪水平组(P0.01);随着饲粮脂肪水平的增加,脂肪消化率呈升高趋势;碳水化合物消化率则以30%脂肪水平组最低,极显著低于10%和20%脂肪水平组(P0.01)。水貂食入氮以HM组最高,极显著高于其他各组(P0.01);粪氮排出量以HL组最高,显著高于LH和HH组(P0.05);尿氮排出量以LH组最低,而氮沉积和氮生物学效价则以LH组最高。随着饲粮蛋白质水平由32%增加到36%,食入氮和尿氮排出量极显著增加(P0.01),而氮生物学效价则显著降低(P0.05)。20%脂肪水平组食入氮最高,极显著高于30%脂肪水平组(P0.01);粪氮排出量和尿氮排出量均以30%脂肪水平组最低,与10%和20%脂肪水平组存在显著(P0.05)或极显著(P0.01)差异;随着饲粮脂肪水平的增加,氮沉积呈先升高后降低的趋势,而氮生物学效价呈升高的趋势。综合各项指标,在本试验条件下,当饲粮蛋白质水平为32%、脂肪水平为20%~30%时,育成期雌性水貂生长性能最佳,且能够降低尿氮排出量,提高水貂对饲粮蛋白质的利用率。

Effects of Dietary Protein and Fat Levels on Growth Performance,Nutrient Digestibility and Nitrogen Metabolism of Female Minks during Growing Period

This experiment was conducted to investigate the effects of dietary protein and fat levels on growth performance, nutrient digestibility and nitrogen metabolism of female minks during growing period, in order to determine the optimum dietary protein and fat levels of female minks during growing period. A 2 × 3 factorial design was adopted in this experiment to designed 6 kinds of experimental diets with 2 protein levels [ 32%( L) and 36% ( H) ] and 3 fat levels [ 10% ( L) , 20% ( M) and 30% ( H) ] . In accordance with protein and fat levels, six kinds of experimental diets were named as LL, LM, LH, HL, HM and HH, respectively. A to-tal of 90 healthy female minks at the age of 60 days were randomly assigned into 6 groups with 15 replicates per group and 1 mink per replicate. The adaptation period lasted for 7 days and the formal period lasted for 60 days. The results showed as follows: the highest values of final weight and average daily gain ( ADG) were found in LH group, they were significantly higher than those in LL and HL groups ( P<0.05) , and they had a increasing trend with dietary fat level increasing. Average daily feed intake ( ADFI) and feed/gain ( F/G) were the lowest in LH group; the ADFI in 30% fat level group was extremely significantly lower than that in 20% fat level group ( P<0.01); the F/G was increased with dietary fat level increasing, and that in 30% fat level group was extremely significantly lower than that in 10% and 20% fat level groups ( P<0.01) . Dry matter digestibility and fat digestibility in LL and HL groups were extremely significantly lower than those in other groups ( P<0. 01); protein digestibility in HH group was significantly higher than that in LL, LH and HL groups ( P<0.05) . With dietary protein level increasing, protein digestibility and fat digestibility were signifi-cantly (P<0.05) and extremely significantly (P<0.01) increased, respectively. Dry matter digestibility and fat digestibility in 10% fat level group were extremely significantly lower than those in 20% and 30% fat level groups ( P<0.01); the fat digestibility showed an increasing trend with dietary fat level increasing; carbohy-drate digestibility in 30% fat level group was the lowest, and extremely significantly lower than that in 10%and 20% fat level groups ( P<0.01) . Nitrogen intake in HM group was the highest, and extremely significantly higher than that in other groups ( P<0.01);fecal nitrogen output in HL group was the highest, and significant-ly higher than that in LH and HH groups ( P<0.05);the lowest value of urine nitrogen output was found in LH group, while the highest values of nitrogen deposition and biological value of nitrogen were found in LH group. With protein level from 32% increased to 36%, the nitrogen intake and urine nitrogen output were extremely significantly increased ( P<0. 01 ) , while the biological value of nitrogen was significantly decreased ( P<0.05) . The nitrogen intake in 20% fat level group was the highest, and extremely significantly higher than that in 30% fat level group ( P<0.01); the fecal nitrogen output and urine nitrogen output in 30% fat level group were the lowest, and had significant ( P<0.05) or extremely significant ( P<0.01) differences compared with 10% and 20% fat level groups; with dietary fat level increasing, the nitrogen deposition was firstly increased and then down, while the biological value of nitrogen was increased. Considering all the indices, when the di-etary protein level is 32% and the fat level is 20% to 30% under the condition of this experiment, the female minks during growing period can get the best growth performance. Furthermore, suitable protein and fat levels of diets for minks can decrease urine nitrogen output and improve protein utilization.