不同种类粗饲料及添加缓冲剂对绵羊瘤胃发酵的影响
摘要
本研究包括两个试验。试验一以4只安装有瘤胃瘘管的绵羊（平均体重26±1.4kg）为试验动物，采用4×4拉丁方试验设计，按精粗比6∶4配合日粮，比较苜蓿干草、玉米秸秆、全株玉米青贮、羊草干草4种粗饲料对绵羊瘤胃发酵的影响。试验二以3只同样条件的绵羊为试验动物，采用3×3拉丁方试验设计，以羊草为粗饲料，日粮精粗比6∶4，试验料Ⅰ和Ⅱ分别在对照基础上添加精料比例1.5%和3%的复合缓冲剂（NaHCO3∶MgO=2∶1），研究以羊草为粗饲料的日粮中添加不同剂量缓冲剂对绵羊瘤胃发酵的影响。试验测定的发酵指标主要包括：pH值、缓冲力（BC）、氨态氮（NH3-N）浓度、挥发性脂肪酸（VFA）浓度和瘤胃液稀释率（LDR）。结果如下：
试验一：不同粗饲料在相同时间点所对应的瘤胃液pH值差异显著（p<0.05）。苜蓿对应的pH值在8h内变化幅度最大（0.81），秸秆对应的pH值变化幅度最小（0.5）；平均值也是苜蓿组的最低，秸秆组的最高。苜蓿、青贮和羊草对应的瘤胃液缓冲力之间的差异不显著（p>0.05），秸秆对应的瘤胃液缓冲力高于其它三组，且差异显著（p<0.05）。苜蓿对应的NH3-N浓度最高值最大，采食秸秆的绵羊，其瘤胃NH3-N浓度最高值最低，但各组在同一时间点的浓度差异不显著（p>0.05）。0h至采食后2～8h内各组的变化趋势一致。绵羊采食后2h，苜蓿对应的乙酸浓度和TVFA浓度显著高于其它各组（p<0.05），其余各种VFA及TVFA浓度在各时间点的差异均不显著（p>.05）。各试验组的乙酸、丙酸比例在2～3之间变动，相同时间点之间差异不显著（p>0.05）。各种粗饲料对瘤胃液稀释率的影响很小，差异不显著（p>0.05）。
试验二：添加缓冲剂的两种试验料对应的pH值在0h高于对照，但差异不显著（p>0.05）。各组的瘤胃pH值均在采食后2～4h内降至最低，两试验料的瘤胃pH值在各时间点均高出对照大约0.2，且与对照相比差异显著（p<0.05）。但两试验料之间差异不显著（p>.05）。采食后8h内，对照的平均pH值显著低于两试验料，两试验料之间差异不显著（p>0.05）。缓冲剂添加量增加，瘤胃缓冲力呈上升趋势，试验料Ⅱ显著高于对照，其余各组之间差异不显著（p>0.05）。在0h点，试验料Ⅰ对应的NH3-N浓度最低，与对照相比差异显著，与试验料Ⅱ相比不显著。其余时间点两试验料对应的NH3-N浓度低于对照，但差异不显著。两试验料对应的乙酸浓度比对照偏低，但除第4h外，其余各点均差异不显著（p>0.05）。试验料对应的丙酸和丁酸浓度也略低于对照，但差异均不显著。在第4h，试验料对应的TVFA浓度显著（p<0.05）低于对照，两试验料间差异不显著（p>.05）。两试验料对应的乙丙比略高于对照，但各组之间均差异不显著（p>0.05）。添加缓冲剂对绵羊的瘤胃液稀释率有提高的趋势，试验料Ⅱ对应的瘤胃液稀释率显著高于对照（p<0.05），其余各组之间差异不显著（p>.05）。
根据本试验结果可得到的结论是：1）玉米秸秆对应的瘤胃液缓冲力大，pH值下降幅度小，无需添加缓冲剂；用苜蓿干草作为粗饲料饲喂绵羊，瘤胃液缓冲力小，pH值下降速度快，幅度大，需要添加缓冲剂；羊草干草和全株玉米青贮作为粗饲料饲喂绵羊，瘤胃液缓冲力小，pH值变化较大，可以考虑添加缓冲剂。2）羊草干草、玉米秸秆和玉
米青贮对绵羊瘤胃的NH3-N浓度、VFA浓度和瘤胃液稀释率影响较小；苜蓿干草的NDF含量较少，CP含量较高，对瘤胃发酵的影响有一定的特殊性。3）缓冲剂可以增加瘤胃液缓冲力，维持正常pH值和增加瘤胃液稀释率，但对NH3-N浓度和VFA浓度影响较小。
This research work content two parts of experiments.4 ruminally cannulated sheep（weighed about 26kg ） were used as trial animal in a 4×4 Latin square design to study the effects of 4 sorts of roughages（alfalfa，maize stover，maize silage，leymus chinensis） on rumen fermentation in sheep. the measured parameters mainly content pH，buffer capacity，concentration of NH3-N，concentration of VFA and ruminal liquid dilution rate. Each period of every experiment included 15 days for adaption，and 4 days for sample collecting.
The results of experiment 1 showed that 4 sorts of roughages affect ruminal pH significantly at the same time points（p<0.05）.The biggest varying range of pH（0.81） during 8 hours after feeding as well as average pH appeared in sheep fed on alfalfa，and the smallest varying range（0.5） and average pH appeared in sheep fed on maize stover. sheep fed on maize stover got the biggest ruminal liquid buffer capacity（p<0.05）compared with others，and the differences between alfalfa，maize silage，leymus chinensis were not significant（p>0.05）.The concentration of NH3-N were not significantly affected by sorts of roughages，though sheep fed on alfalfa reached the highest NH3-N concentration，and maize stover group was of the lowest level. The varying trend of VFA were roughly the same among sheep fed on different sorts of roughages, except that the concentration of acetic acid at 2 hours after feeding was significantly（p<0.05）higher in sheep fed on alfalfa. And the ratio of acet/prop were not significantly affected by sorts of roughages. These had little effect on ruminal liquid dilution rate, either.
In experiment 2，addition of buffer significantly increased pH at almost every time point compared with the control diet（p<0.05），except at 0 hour point，the average amount of pH increase was 0.2，and the difference between two trial diet was not significant（p>0.05）. And as the addition of buffer increased，buffer capacity of ruminal liquid increased as well，but it was not affected by the amount of buffer in a linear pattern. Two trial diets increased BC significantly，but the difference in between was not significant（p>0.05）. The concentration of NH3-N were relatively higher in sheep fed on control diet，but the difference was insignificant，the two trial diets had similar NH3-N concentrations. Addition of buffer decreased the concentrations of VFA at almost every time point，but the difference were insignificant（p>0.05）. except when it comes to the concentration of acetic acid and TVFA at 4 hour after feeding. Acet/prop varied in the range of 2 to 3，addition of buffer slightly increased the rate of acetic acid，but it was not significant. the effect of the trialⅠand trial Ⅱ
were almost the same. Addition of buffer had the trend of increasing LDR，and the difference between trialⅡand control was significant，while others were not.
Conclusions can be drew as follows: 1）when sheep was fed with high rate of concentrate，maize stover can ensure high level of ruminal BC，and relatively normal pH，so it is not necessary to add buffer in diet; When feed on alfalfa，ruminal BC is relative low，pH can be very low，so adding buffer is necessary; leymus chinensis and maize silage bring medium pH，maybe a little lower than normal level，so it is recommended to add certain dose of buffer.2）Maize stover，maize silage and leymus chinensis has little effect on NH3-N or VFA，alfalfa may affect ruminal fermentation at certain level，maybe because of its relative high level of CP .3）Addition of buffer can effectively affect ruminal fermentation on pH and BC and LDR，but its effect on NH3-N and VFA is not as significant，at least at this in vivo experimental level.
试验一：不同粗饲料在相同时间点所对应的瘤胃液pH值差异显著（p<0.05）。苜蓿对应的pH值在8h内变化幅度最大（0.81），秸秆对应的pH值变化幅度最小（0.5）；平均值也是苜蓿组的最低，秸秆组的最高。苜蓿、青贮和羊草对应的瘤胃液缓冲力之间的差异不显著（p>0.05），秸秆对应的瘤胃液缓冲力高于其它三组，且差异显著（p<0.05）。苜蓿对应的NH3-N浓度最高值最大，采食秸秆的绵羊，其瘤胃NH3-N浓度最高值最低，但各组在同一时间点的浓度差异不显著（p>0.05）。0h至采食后2～8h内各组的变化趋势一致。绵羊采食后2h，苜蓿对应的乙酸浓度和TVFA浓度显著高于其它各组（p<0.05），其余各种VFA及TVFA浓度在各时间点的差异均不显著（p>.05）。各试验组的乙酸、丙酸比例在2～3之间变动，相同时间点之间差异不显著（p>0.05）。各种粗饲料对瘤胃液稀释率的影响很小，差异不显著（p>0.05）。
试验二：添加缓冲剂的两种试验料对应的pH值在0h高于对照，但差异不显著（p>0.05）。各组的瘤胃pH值均在采食后2～4h内降至最低，两试验料的瘤胃pH值在各时间点均高出对照大约0.2，且与对照相比差异显著（p<0.05）。但两试验料之间差异不显著（p>.05）。采食后8h内，对照的平均pH值显著低于两试验料，两试验料之间差异不显著（p>0.05）。缓冲剂添加量增加，瘤胃缓冲力呈上升趋势，试验料Ⅱ显著高于对照，其余各组之间差异不显著（p>0.05）。在0h点，试验料Ⅰ对应的NH3-N浓度最低，与对照相比差异显著，与试验料Ⅱ相比不显著。其余时间点两试验料对应的NH3-N浓度低于对照，但差异不显著。两试验料对应的乙酸浓度比对照偏低，但除第4h外，其余各点均差异不显著（p>0.05）。试验料对应的丙酸和丁酸浓度也略低于对照，但差异均不显著。在第4h，试验料对应的TVFA浓度显著（p<0.05）低于对照，两试验料间差异不显著（p>.05）。两试验料对应的乙丙比略高于对照，但各组之间均差异不显著（p>0.05）。添加缓冲剂对绵羊的瘤胃液稀释率有提高的趋势，试验料Ⅱ对应的瘤胃液稀释率显著高于对照（p<0.05），其余各组之间差异不显著（p>.05）。
根据本试验结果可得到的结论是：1）玉米秸秆对应的瘤胃液缓冲力大，pH值下降幅度小，无需添加缓冲剂；用苜蓿干草作为粗饲料饲喂绵羊，瘤胃液缓冲力小，pH值下降速度快，幅度大，需要添加缓冲剂；羊草干草和全株玉米青贮作为粗饲料饲喂绵羊，瘤胃液缓冲力小，pH值变化较大，可以考虑添加缓冲剂。2）羊草干草、玉米秸秆和玉
米青贮对绵羊瘤胃的NH3-N浓度、VFA浓度和瘤胃液稀释率影响较小；苜蓿干草的NDF含量较少，CP含量较高，对瘤胃发酵的影响有一定的特殊性。3）缓冲剂可以增加瘤胃液缓冲力，维持正常pH值和增加瘤胃液稀释率，但对NH3-N浓度和VFA浓度影响较小。
This research work content two parts of experiments.4 ruminally cannulated sheep（weighed about 26kg ） were used as trial animal in a 4×4 Latin square design to study the effects of 4 sorts of roughages（alfalfa，maize stover，maize silage，leymus chinensis） on rumen fermentation in sheep. the measured parameters mainly content pH，buffer capacity，concentration of NH3-N，concentration of VFA and ruminal liquid dilution rate. Each period of every experiment included 15 days for adaption，and 4 days for sample collecting.
The results of experiment 1 showed that 4 sorts of roughages affect ruminal pH significantly at the same time points（p<0.05）.The biggest varying range of pH（0.81） during 8 hours after feeding as well as average pH appeared in sheep fed on alfalfa，and the smallest varying range（0.5） and average pH appeared in sheep fed on maize stover. sheep fed on maize stover got the biggest ruminal liquid buffer capacity（p<0.05）compared with others，and the differences between alfalfa，maize silage，leymus chinensis were not significant（p>0.05）.The concentration of NH3-N were not significantly affected by sorts of roughages，though sheep fed on alfalfa reached the highest NH3-N concentration，and maize stover group was of the lowest level. The varying trend of VFA were roughly the same among sheep fed on different sorts of roughages, except that the concentration of acetic acid at 2 hours after feeding was significantly（p<0.05）higher in sheep fed on alfalfa. And the ratio of acet/prop were not significantly affected by sorts of roughages. These had little effect on ruminal liquid dilution rate, either.
In experiment 2，addition of buffer significantly increased pH at almost every time point compared with the control diet（p<0.05），except at 0 hour point，the average amount of pH increase was 0.2，and the difference between two trial diet was not significant（p>0.05）. And as the addition of buffer increased，buffer capacity of ruminal liquid increased as well，but it was not affected by the amount of buffer in a linear pattern. Two trial diets increased BC significantly，but the difference in between was not significant（p>0.05）. The concentration of NH3-N were relatively higher in sheep fed on control diet，but the difference was insignificant，the two trial diets had similar NH3-N concentrations. Addition of buffer decreased the concentrations of VFA at almost every time point，but the difference were insignificant（p>0.05）. except when it comes to the concentration of acetic acid and TVFA at 4 hour after feeding. Acet/prop varied in the range of 2 to 3，addition of buffer slightly increased the rate of acetic acid，but it was not significant. the effect of the trialⅠand trial Ⅱ
were almost the same. Addition of buffer had the trend of increasing LDR，and the difference between trialⅡand control was significant，while others were not.
Conclusions can be drew as follows: 1）when sheep was fed with high rate of concentrate，maize stover can ensure high level of ruminal BC，and relatively normal pH，so it is not necessary to add buffer in diet; When feed on alfalfa，ruminal BC is relative low，pH can be very low，so adding buffer is necessary; leymus chinensis and maize silage bring medium pH，maybe a little lower than normal level，so it is recommended to add certain dose of buffer.2）Maize stover，maize silage and leymus chinensis has little effect on NH3-N or VFA，alfalfa may affect ruminal fermentation at certain level，maybe because of its relative high level of CP .3）Addition of buffer can effectively affect ruminal fermentation on pH and BC and LDR，but its effect on NH3-N and VFA is not as significant，at least at this in vivo experimental level.
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Beauchemin K.A. and Buchanan-Smith J.G. Effects of fiber source and method of feeding on chewing activities, digestive function, and productivity of dairy cows. J. Dairy Sci. 1990 73:749-762.?
Beauchemin K.A., Rode L.M. and Eliason M.V. Chewing activities and milk production of dairy cows fed alfalfa as hay, silage, or dried cubes of hay or silage. J. Dairy Sci. 1997 80:324-333.?
Beauchemin, K. A., and J. G. Buchanan-Smith. 1990.Effects of fiber source and method of feeding on chewing activities, digestive function, and productivity of dairy cows. J. Dairy Sci. 73:749
Beaumont, R.,A.Grasland, and A. Detour. 1998. Methods of conservation of ryegrass and short-term feeding preferences. Fourrages 155:397-402.
Campbell C.P., Marshall S.A., Mandell I.B. and Wilton J.W. Effects of source of dietary neutral detergent fiber on chewing behavior in beef cattle fed pelleted concentrates with or without supplemental roughage. J. Anim. Sci. 1992 70: 894-903.?
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Castle, M. W., W. C. Retter, and J. N. Watson. 1979.Silage and milk production: comparisons between grass silage of three different chop lengths. Grass Forage Sci. W293.
Chesson A., Forsberg C.W. Polysaccharide degradation by rumen microorganisms. The Rumen microbial ecosystem. Elsevier Applied Science, c1988:251-284.
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Clark P.W. and Armentano L. E. Effectiveness of neutral detergent fiber in whole cottonseed and dried distillers grains compared with alfalfa haylage. J. Dairy Sci. 1993 76:2644-2650.?
Cole N.A., Greene L.W., McCollum F.T., Montgomery T. and McBride K. Influence of oscillating dietary crude protein concentration on performance, acid-base balance, and nitrogen excretion of steers. J. Anim Sci. 2003 81:2660-2668.?
Cone J.W., Van Gelder A.H., Soliman I.A., De Visser H. and Van Vuuren A.M. Different techniques to study rumen fermentation characteristics of maturing grass and grass silage. J. Dairy Sci. 1999 82:957-966.?
Cooper D., Kyriazakis I. and Oldham J.D. The effects of physical form of feed, carbohydrate source, and inclusion of sodium bicarbonate on the diet selections of sheep. J. Anim Sci. 1996 74:1240-1251
Crawford Ladell., In vitro interaction of food fiber with some regularly prescribed drugs. Nutr-Rep-Int. 1983 28（3）:481-486.
Friggens N.C., Oldham J.D., Dewhurst R.J. and Horgan G. Proportions of volatile fatty acids in relation to the chemical composition of feeds based on grass silage. J. Dairy Sci. 1998 81:1331-1344.?
Froetschel M.A. and Amos H.E. Effects of dietary fiber and feeding frequency on ruminal fermentation, digesta water-holding capacity, and fractional turnover of contents. J. Anim Sci. 1991 69:1312-1321.?
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Goad D.W., Goad C.L. and Nagaraja T.G. Ruminal microbial and fermentative changes associated with experimentally induced subacute acidosis in steers. J. Anim Sci. 1998 76:234-241.?
Grant R.J. Interactions among forages and nonforage fiber sources. J. Dairy Sci. 1997 80:1438-1446.?
Harmison B., Eastridge M.L., and Firkins J.L. Effect of percentage of dietary forage neutral detergent fiber and source of starch on performance of lactating Jersey cows. J.Dairy Sci. 1997 80:905-911.?
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Beauchemin K.A. and Buchanan-Smith J.G. Effects of fiber source and method of feeding on chewing activities, digestive function, and productivity of dairy cows. J. Dairy Sci. 1990 73:749-762.?
Beauchemin K.A., Rode L.M. and Eliason M.V. Chewing activities and milk production of dairy cows fed alfalfa as hay, silage, or dried cubes of hay or silage. J. Dairy Sci. 1997 80:324-333.?
Beauchemin, K. A., and J. G. Buchanan-Smith. 1990.Effects of fiber source and method of feeding on chewing activities, digestive function, and productivity of dairy cows. J. Dairy Sci. 73:749
Beaumont, R.,A.Grasland, and A. Detour. 1998. Methods of conservation of ryegrass and short-term feeding preferences. Fourrages 155:397-402.
Campbell C.P., Marshall S.A., Mandell I.B. and Wilton J.W. Effects of source of dietary neutral detergent fiber on chewing behavior in beef cattle fed pelleted concentrates with or without supplemental roughage. J. Anim. Sci. 1992 70: 894-903.?
Carter R.R. and Grovum W. L. A review of the physiological significance of hypertonic body fluids on feed intake and ruminal function: salivation, motility and microbes. J. Anim Sci. 1990 68:2811-2832.?
Castle, M. W., W. C. Retter, and J. N. Watson. 1979.Silage and milk production: comparisons between grass silage of three different chop lengths. Grass Forage Sci. W293.
Chesson A., Forsberg C.W. Polysaccharide degradation by rumen microorganisms. The Rumen microbial ecosystem. Elsevier Applied Science, c1988:251-284.
Christiansen M.L. and Webb K.E. Intestinal acid flow, dry matter, starch and protein digestibility and amino acid absorption in beef cattle fed a high-concentrate diet with defluorinated rock phosphate, limestone or magnesium oxide. J. Anim Sci. 1990 68:2105-2118.?
Clark P.W. and Armentano L. E. Effectiveness of neutral detergent fiber in whole cottonseed and dried distillers grains compared with alfalfa haylage. J. Dairy Sci. 1993 76:2644-2650.?
Cole N.A., Greene L.W., McCollum F.T., Montgomery T. and McBride K. Influence of oscillating dietary crude protein concentration on performance, acid-base balance, and nitrogen excretion of steers. J. Anim Sci. 2003 81:2660-2668.?
Cone J.W., Van Gelder A.H., Soliman I.A., De Visser H. and Van Vuuren A.M. Different techniques to study rumen fermentation characteristics of maturing grass and grass silage. J. Dairy Sci. 1999 82:957-966.?
Cooper D., Kyriazakis I. and Oldham J.D. The effects of physical form of feed, carbohydrate source, and inclusion of sodium bicarbonate on the diet selections of sheep. J. Anim Sci. 1996 74:1240-1251
Crawford Ladell., In vitro interaction of food fiber with some regularly prescribed drugs. Nutr-Rep-Int. 1983 28（3）:481-486.
Friggens N.C., Oldham J.D., Dewhurst R.J. and Horgan G. Proportions of volatile fatty acids in relation to the chemical composition of feeds based on grass silage. J. Dairy Sci. 1998 81:1331-1344.?
Froetschel M.A. and Amos H.E. Effects of dietary fiber and feeding frequency on ruminal fermentation, digesta water-holding capacity, and fractional turnover of contents. J. Anim Sci. 1991 69:1312-1321.?
Fry S.C. The structure and functions of xyloglucan. J-Exp-Bot. Oxford : Oxford
University Press. 1989 40（10）:1-11.
Fuchigami M., Senshu T., Horiguchi M. A simple continuous culture system for rumen microbial digestion study and effects of defaunation and dilution rates. and polysaccharides fractionated by successive extraction. J. Dairy Sci1989 72（11）:3070-3080.
Goad D.W., Goad C.L. and Nagaraja T.G. Ruminal microbial and fermentative changes associated with experimentally induced subacute acidosis in steers. J. Anim Sci. 1998 76:234-241.?
Grant R.J. Interactions among forages and nonforage fiber sources. J. Dairy Sci. 1997 80:1438-1446.?
Harmison B., Eastridge M.L., and Firkins J.L. Effect of percentage of dietary forage neutral detergent fiber and source of starch on performance of lactating Jersey cows. J.Dairy Sci. 1997 80:905-911.?
Harris K.B., Thomas V.M., Peterson M.K., Kachman S.D., McInerney M.J. Influence of minerals on rate of digestion and percentage degradable in vitro neutral detergent fiber. Nutr-Rep-Int. 1989 40（2）:219-226.
Hart S. P. and Glimp H.A. Effect of diet composition and feed intake level on diet digestibility and ruminal metabolism in growing lambs. J. Anim Sci. 1991 69:1636-1644.?
Heitmann R N., Bergman E N. Transport of amino acids in whole blood and plasma of sheep. Am J Physiol.1980 239:E242-E247
Hino T, Russell J B. Relation contributions of Ruminal bacteria and protozoa to the degradation of protein in vitro. J Anima Sci, 1987 64:261-270
Hsu J.T., Fahey G.C., Clark J.H., Berger L.L., and Merchen N.R. Effects of urea and sodium bicarbonate supplementation of a high-fiber diet on nutrient digestion and ruminal characteristics of defaunated sheep. J. Anim Sci. 1991 69:1300-1311.?
James B.Russell. Another Theory for the Action of Ruminal Buffer Salts: Decreased Starch Fermentation and Propionate Production. J.Dairy.Sci. 1993 76:826-830
Jaster, E. H., and M. R. Murphy. 1983. Effects of varying particle size of forage on digestion and chewing behavior of dairy heifers. J. Dairy Sci. 66:802.
Kennedy PM.and Milligan. Effects of cold exposure on digestion, microbial synthesis and nitrogen transformations in sheep. Br.J Nutr, 1978 39（1）:105-117.
Khorasani G.R., and Kennelly J.J. Influence of carbohydrate source and buffer on rumen fermentation characteristics, milk yield, and milk composition in late-lactation Holstein cows. J. Dairy Sci. 2001 84:1707-1716.?
Lammers B.P., Buckmaster D.R.and Heinrichs A. J. A simple method for the analysis of particle sizes of forage and total mixed rations. J.Dairy Sci. 1996 79: 922-928.
Le Ruyet P., Tucker W.B., Hogue J.F., Aslam M., Lema M., Shin I.S., Miller T.P. and
Adams G.D. Influence of dietary fiber and buffer value index on the ruminal milieu of lactating dairy cows. J.Dairy Sci. 1992 75:2394-2408.?
Maekawa M., Beauchemin K.A. andChristensen D.A. Effect of concentrate level and feeding management on chewing activities, saliva production, and ruminal pH of lactating dairy cows. J.Dairy Sci. 2002 85:1165-1175.?
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