饲喂水平对冬毛生长期北极狐能量、氮及气体代谢的影响

Effects of Feeding Level on Energy,Nitrogen and Gas Metabolism of Arctic Foxes during Winter Fur Growth Period

本试验旨在研究饲喂水平对冬毛生长期北极狐能量、氮及气体代谢的影响。选取36只161日龄、平均体重为(7285±6)g的健康雄性北极狐,随机分成4组,每组9个重复,每个重复1只。各组北极狐饲喂相同的饲粮,但饲喂水平分别为自由采食(Ⅰ组)、自由采食量的80%(Ⅱ组)、自由采食量的60%(Ⅲ组)和自由采食量的40%(Ⅳ组)。试验共分6期完成,每个饲喂水平进行3期,每期选取6只北极狐随机放到6个呼吸代谢室中,每个呼吸代谢室中放入1只北极狐。采用狐用呼吸测热装置完成消化代谢试验、呼吸测热试验和绝食代谢试验。试验从2017年10月2日开始至2017年12月14日结束。结果显示:1)随着饲喂水平的降低,摄入总能(GEI)、粪能(FE)、尿能(UE)、消化能(DE)、代谢能(ME)和净能(NE)均极显著降低(P<0.01),总能消化率(DE/GE)和总能代谢率(ME/GE)未发生显著变化(P>0.05),但消化能转化成代谢能的效率(ME/DE)和代谢能转化成净能的效率(NE/ME)显著或极显著降低(P<0.05或P<0.01);此外,饲粮净能摄入(NEI)显著降低(P<0.05),而饲粮消化能摄入(DEI)和代谢能摄入(MEI)无显著变化(P>0.05)。2)随着饲喂水平的降低,摄入氮(NI)、粪氮(FN)、尿氮(UN)、沉积氮(RN)、RN/NI和RN/消化氮(DN)均显著或极显著降低(P<0.05或P<0.01),而氮表观消化率未受饲喂水平的显著影响(P>0.05)。3)在呼吸测热试验中,Ⅲ组的呼吸商(RQ)极显著高于其他3组(P<0.01),Ⅱ组的O 2消耗量(VO 2)和CO 2产生量(VCO 2)显著高于其他3组(P<0.05);在绝食代谢试验中,饲喂水平对RQ、VO 2和VCO 2无显著影响(P>0.05)。由此得出,在本试验条件下,限饲显著降低了冬毛生长期北极狐各种有效能的摄入与利用及DE和ME的转化效率、氮的摄入与沉积;同时,适量限饲未显著降低冬毛生长期北极狐对氮的利用,且提高了营养物质氧化代谢的程度,增加了O 2消耗和CO 2排出;通过建立RN与NI的回归方程,推算冬毛生长期北极狐的维持净氮和净蛋白质需要量分别为676.3 mg/(kg BW 0.75·d)和4.227 g/(kg BW 0.75·d)。

This experiment was conducted to study the effects of feeding levels on the metabolism of energy,nitrogen and gas of Arctic foxes during winter fur growth period.Thirty-six 161-day-old male Arctic foxes with average body weight of(7285±6)g were randomly divided into 4 groups with 9 replicates per group and 1 fox per replicate.All foxes fed the same diet,but the feeding level was ad libitum feeding(Ⅰgroup),80%ad libitum intake(Ⅱgroup),60%ad libitum intake(Ⅲgroup)and 40%ad libitum intake(Ⅳgroup),respectively.The experiment was completed in 6 phases with 3 phases for each feeding level.Six Arctic foxes were selected for each phase and randomly placed into 6 respiratory metabolism chambers,and 1 Arctic fox was put into each respiratory metabolism chamber.The digestion and metabolism trial,respiratory calorimetry measurement test and fasting metabolism test were carried out by the respiration calorimetry measurement device for fox.The trial began on October 2,2017 and ended on December 14,2017.The results showed as follows:1)as the feeding level decreasing,the gross energy intake(GEI),feces energy(FE),urine energy(UE),digestible energy(DE),metabolizable energy(ME),net energy(NE)were extremely significantly reduced(P<0.01),the ME/DE and NE/ME were significantly or extremely significantly decreased(P<0.05 or P<0.01),however,the DE/GE and ME/GE were not significantly influenced(P>0.05);in addition,dietary net energy intake(NEI)was significantly decreased(P<0.05),but the digestible energy intake(DEI)and metabolizable energy intake(MEI)were not significantly affected(P>0.05).2)As the feeding level decreasing,the nitrogen intake(NI),fecal nitrogen(FN),urinary nitrogen(UN),nitrogen retention(RN),RN/NI and RN/digestible nitrogen(DN)were significantly or extremely significantly reduced(P<0.05 or P<0.01),however,the nitrogen apparent digestibility was not significantly influenced by feeding level(P>0.05).3)In the respiration heat test,the respiratory quotient(RQ)in groupⅢwas extremely significantly higher than that in the other three groups(P<0.01),and the O 2 consumption and CO 2 emission in groupⅡwere significantly higher than those in the other three groups(P<0.05).In the fasting metabolism test,feeding level had no significant effects on RQ,O 2 consumption and CO 2 emission(P>0.05).In conclusion,under the conditions of this experiment,restricted feeding significantly reduces the intake and utilization of all kinds of effective energy,the conversion efficiency of DE and ME,and the intake and retention of nitrogen during the winter fur growth period of Arctic fox.Meanwhile,appropriate restriction of feeding does not significantly reduce the utilization of nitrogen,and improves the degree of oxidative metabolism of nutrients,increases O 2 consumption and CO 2 emission.The regression equations of NI and RN are established,and the maintenance net nitrogen and protein requirements for Arctic foxes during the winter fur growth period are 676.3 mg/(kg BW 0.75·d)and 4.227 g/(kg BW 0.75·d),respectively.