Effect of dietary crude protein level on apparent nutrient digestibility of Yunnan memi-fine wool ewes during pregnancy
The aim of this experiment was to investigate the effect of dietary crude protein(CP)levels on the apparent nutrient digestibility of Yunnan semi-fine wool eves during pregnancy.Select 50 Yunnan semi-fine wool eves in good condition,of the same age and breeding date,with a weight of(46.52±4.58)kg and 2 fetuses,and randomly divide them into 5 groups,with 10 replicates in each group,with 1 sheep in each replicate.Starting from the 46th day of pregnancy,a feeding experiment was conducted with a pre-trial period of 14 days and a trial period of 90 days.In the early pregnancy(1st to 30th day of the trial period)and mid pregnancy(31st to 60th day of the trial period),experimental diets with crude protein levels of 6.65%(group 1),9.02%(group 2),10.97%(group 3),12.43%(group 4)and 13.95%(group 5)were fed,respectively.In the late pregnancy(61～90th day of the trial period),experimental diets with crude protein levels of 6.31%(group 1),7.77%(group 2),10.47%(group 3),12.69%(group 4),and 15.25%(group 5)were fed,respectively.On the 11th to 15th day,41st to 45th day,and 71st to 75th day of the trial period,5 experimental sheep were selected from each group to conduct a 5-day digestion and metabolism experiment.The results showed that:(1)In the early and middle stages of pregnancy,except for the first group,there was no significant difference in the apparent digestibility of dry matter(DM)among the other four groups(P>0.05).In the later stages of pregnancy,the apparent digestibility of DM in the third and fifth groups increased by 9.15%and 7.25%,respectively,compared with the first group(P<0.05).(2)In the early pregnancy,the nitrogen(N)apparent digestibility of the last three groups increased by at least 34.25%compared with the first two groups(P<0.01).In the middle pregnancy,the N apparent digestibility of the fourth and fifth groups increased by at least 43.66%compared with the first two groups(P<0.01).In the late pregnancy,the N apparent digestibility of the fifth group increased by 61.88%,45.02%,and 19.07%compared with the first,second and third groups,respectively(P<0.01).(3)The digestibility of neutral detergent fiber(NDF)increased with the increase of dietary CP levels.In early pregnancy,the apparent digestibility of NDF in groups 4 and 5 increased by 22.25%and 21.06%,respectively,compared with group 1(P<0.05).In mid pregnancy,the apparent digestibility of NDF in the last three groups increased by at least 26.67%compared with groups 1 and 2(P<0.01).In late pregnancy,the apparent digestibility of NDF in groups 4 and 5 increased by at least 30.67%compared with groups 1 and 2(P<0.01).(4)In the first trimester,the digestibility of acid washing fibers(ADF)in the last four groups increased by at least 31.26%(P<0.01)compared with the first group.In the second trimester,the apparent digestibility of ADF in the fifth group increased by 60.98%(P<0.01)compared with the first group.In the later trimester,the apparent digestibility of ADF in the third group increased by 50.20%and 38.90%(P<0.01)compared with the first and second groups,respectively.(5)There was no significant difference in the digestibility of calcium(Ca)and phosphorus(P)among the groups throughout the entire pregnancy period(P>0.05).(6)In the early stages of pregnancy,the apparent digestibility of total energy(GE)in groups 2,3 and 4 increased by 3.35%,2.90%and 2.10%compared with group 5(P<0.05),while it increased by 13.60%,12.41%and 11.50%compared with group 1(P<0.01).There was no significant difference in GE apparent digestibility between the groups in the middle and late stages of pregnancy(P>0.05).In summary,during the pre,mid,and post pregnancy stages,when the dietary crude protein levels were 10.97%,12.43%and 15.25%,the apparent digestibility of dietary nitrogen(N)was the highest.The dietary crude protein level had no effect on the apparent digestibility of Ca and P.
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