Effects Of Dietary NDF Content On Growth Performance And Rumen Development Of Lambs

The aim of this study was to assess the effects of neutral detergent fiber level of diet on growth performance and rumen development.One hundred Hu lambs(18 ± 2 d of age and 6.10 kg ± 0.10 kg of BW)were divided among 20 pens and assigned to 1 of 4 dietary treatments(25 lambs per group)in a completely randomized design.Dietary treatments contained different NDF contents:1)10%(N10),2)15%(N15),3)20%(N20),4)25%(N25).The growth performance was determined by feeding experiment.slaughter performance and ruminal histomorphology were observed in slaughtering experiment.Experiment 2 was conducted to study the effect of early feeding different NDF level diets on growth performance and rumen of lambs at fattening stages.Results of present research were showed as follows.Experiment 1:Effects of dietary NDF levels on growth performance and rumen development of early-weaned Hu lambsThis experiment was conducted to study the effects of neutral detergent fiber level of diet on growth performance,serum indices,slaughter performance and rumen development of early-weaned Hu lambs.The results showed as followed:1)At 50,60 and 90 days of age,body weight in 20N group and 25N group was significantly higher than that of 10N group(P<0.05);Average daily gain and dry matter intake in 20N group and 25N group were significantly higher than that of 10N group during 40 to 90 days of age(P<0.05).Feed to gain ratio of lambs did not differ among groups except at 51 to 60 days of age(P>0.05).2)Bloodβ-hydroxybutyrate concentrations in 15N,20N and 25N group were higher than in 10N group(P<0.05).3)Group of 20N and 25N had a greater live weight before slaughter and carcass weight than that in 10N group(P<0.05).Head percentage of live weight before slaughter was significantly lower for lambs in 25N group than that in 10N group,while feet,heart,liver and spleen weight in 25N were higher than that in 10N group(P<0.05);group of 20N had a greater heart and liver weight than that in 10N group(P<0.05).4)The apparent digestibility of DM,GE,NDF and nitrogen in 20N and 25N was lower than that of 10N(P<0.05).Nitrogen intake,fecal nitrogen and nitrogen excretion in 20N and 25N were higher than those of 10N(P<0.05).5)The reticulorumen weight expressed as a percentage of stomach complex decreased linearly,while the abomasum and omasum weight expressed as a percentage of stomach complex increased linearly with the increase of dietary NDF levels.when expressed relative to stomach complex,the reticulorumen weight declined(P<0.05)in 25N compared with ION and 15N lambs.The abomasum and omasum expressed as a percentage of stomach complex in 20N and 25N were higher than those of 10N.6)pH values increased linearly(P<0.05)with the rise of dietary NDF levels and the acetate to propionate ratio and the molar proportion of propionate were lower(P<0.05)in lambs fed 20N and 25N than in lambs fed ION and 15N.However,lambs fed 20N and 25N showed a greater(P<0.05)molar proportion of acetate compared with lambs fed ION and 15N.7)Lambs fed 15N,20N and 25N decreased keratin layer thickness and papillae width(P<0.05),whereas increased(P<0.05)muscle layers thickness when compared with lambs fed ION.Furthermore,epithelium thickness was thinner in 25N than that in other treatments.NDF can be concentrate up to 20%in lamb starter during days 20 to 90,because it benefits growth and slaughter performance and rumen development.Experiment 2:Effects of early feeding different NDF level diets on growth performance and rumen development of lambs at fattening stagesThis experiment was conducted to study the effect of early feeding different NDF level diets on growth performance,serum indices and slaughter performance of lambs at fattening stages.After 90 days of age,all the lambs were fed a same total mixed ration ad libitum.The results showed as followed:1)At 90 days of age,body weight in 15N,20N and 25N group was significantly higher than that of 10N group(P<0.05).At 120 days of age,body weight in 20N group and 25N group was significantly higher than that of 10N group,while there was an increasing trend at 150 days of age(P=0.079).Average daily gain in 20N and 25N groups was significantly higher than that of 10N group during 90 to 120 days of age(P<0.05),while it was significantly higher in 10N and 15N groups than that of 20N and 25 groups during 120 to 150 days of age(P<0.05).Dry matter intake in 20N group was significantly higher than that of 10N group during 90 to 120 days of age(P<0.05),but no significant difference was found in feed conversion at different stages(P>0.05).2)Blood TP concentrations in 20N group were higher than in 10N group(P<0.05);blood(β-hydroxybutyrate concentrations in 25N group were higher than in 10N and 15N groups(P<0.05).3)Carcass weight in 20N and 25N groups had an increasing trend than that in 10N group(P=0.061).4)Percentage of head to live weight before slaughter was significantly higher for lambs in 10N group than that in 20N group,and no significant differences were found in other parameters(P>0.05).5)There were no difference in the apparent digestibility of DM,GE,NDF and nitrogen among treatments(P>0.05).6)There were no difference in rumen fermentation parameters among treatments(P>0.05).7)Lambs fed N20 and N25 increased(P<0.05)epithelium thickness and muscle layers thickness when compared with lambs fed 10N.early feeding different NDF level dietsIn conclusion,under the present experimental condition,feeding high NDF level diets improved the growth performance,slaughter performance and rumen development Early feeding high NDF level diets promoted ADG of lambs at early fattening stages,but ADG declined at latter fattening stages.Further,the results showed that the appropriate dietary NDF level could not be determined only according to the early traits of lamb and it was more scientific to explore the dietary NDF level from long-term growth performance.Our study suggests that dietary NDF at level up to 15%can be incorporated in diets.