Effects Of Tannin On Rumen Fermentation Parameters,Nutrient Digestibility And Methane Emission In Sheep

The effects of tannin from Caragana korshinskii on rumen fermentation parameters,apparent digestibility of total digestive tract nutrients and methane emission in sheep were studied in this paper.This study is divided into two parts:in vitro and in vivo experiments.In vitro fermentation experiment,concentrate,hay and tannin acid were used as fermentation substrates.The effects of different levels of tannic acid(0.5%,1%,1.5%,2%,3%,4%)on rumen fermentation parameters,total gas production,methane yield,dry matter and crude protein degradation in sheep in vitro were studied,and the suitable content of tannin in diet was screened for in vivo fermentation experiment.Fifteen Dumont crossbred sheep aged 1?1.5 years and weighing about 40 kg were selected in vivo.The experimental animals were randomly divided into three groups according to the principle of similar weight,with 5 sheep in each group.The pre-feeding period was 14 days and the formal period was 60 days.The experiment was designed by single factor complete randomized experiment.The experiment was divided into three groups:group I(control group,diet without tannin),group ?(diet containing 2%tannin)and group III(diet containing 4%tannin).Caragana was used as the source of tannin in the diet.The concentrate-to-roughage ratio of the three groups was 4:6,which was formulated according to the principle of equal energy and equal nitrogen.Rumen fluid was collected before(0 h)morning feeding and 3,6 and 9 h after morning feeding for the determination of rumen environmental parameters(pH,NH3-N concentration,BCP concentration and VFA concentration).Apparent digestibility and nitrogen metabolic rate of nutrients were measured by total fecal collection digestion and metabolic test.Average daily gain was calculated by weighing every 15 days in the formal period.Respiratory metabolic measurement system of terrestrial animals was used to measure the rumen environmental parameters(pH,NH3-N concentration,BCP concentration and VFA concentration).Methane emissions from experimental animals were measured.The test results show that:(1)The addition of tannin had no significant effect on the pH value of rumen fermentation in vitro(P>0.05);the addition of 2%,3%and 4%tannin significantly reduced NH3-N concentration,acetic acid concentration,ethylene-propylene ratio,total gas production and methane production in rumen fermentation in vitro(P<0.05).Addition of 2%,3%and 4%tannins significantly increased the concentration of mycelial protein in rumen sheep fermentation in vitro(P<0.05).(2)Addition of 2%,3%and 4%tannin significantly reduced total rumen fermentation gas production and methane production in sheep(P<0.05);the degradation rate of dry matter in rumen fermentation in vitro in each tannin supplementation group was significantly lower than that in control group(P<0.05);the degradation rate of crude protein in rumen fermentation in vitro in 0.5%,1%,1.5%,2%and 4%tannin supplementation group was significantly lower than that in control group(P<0.05).(3)Tannin containing 2%and 4%from Caragana korshinskii had no significant effect on rumen pH value of sheep before and 3,6 and 9 hours after feeding(P>0.05).Dietary tannins containing 2%and 4%significantly reduced rumen ammonia nitrogen concentration of sheep at 3 and 6 hours after feeding(P<0.05),and significantly increased rumen bacterial protein concentration at 6 and 9 hours after feeding(P<0.05).At 9 hours after morning feeding,the concentration of acetic acid and total volatile fatty acids in rumen of sheep was significantly decreased by 2%and 4%tannins in diet(P<0.05).(4)Dietary tannin containing 2%and 4%had no significant effect on DM,CP,OM,NDF and ADF digestibility and daily gain of sheep(P>0.05).(5)2%and 4%of the tannin from Caragana korshinskii in the diet increased the digestible nitrogen utilization rate.4%tannin from Caragana korshinskii in diet significantly increased deposition nitrogen and retention rate in sheep.The diet containing 2%and 4%condensed tannins from Caragana korshinskii had no significant effect on digestible nitrogen,nitrogen digestibility,excretion of fecal nitrogen and ratio of fecal to urinary nitrogen.(6)The daily methane emission of sheep in 2%and 4%tannin group was significantly lower than that of control group(P<0.05);the daily methane emission of sheep in 2%and 4%tannin group was significantly lower than that of control group(P<0.05).