西北地区4种优质饲草的肉牛体外瘤胃发酵性能研究

An in vitro study of fermentation properties of four high-quality forages and their mixtures treated with rumen fluid from beef cattle in northwest China

本试验选用黄土高丘陵沟壑区推广应用的玉米、燕麦、苜蓿裹包青贮及苜蓿干草为试验材料,旨在研究其在肉牛体外瘤胃发酵性能及组合效应,为其科学应用提供技术支持。将4种优质饲草按干物质基础组成7种不同比例组合,即C 1(50%玉米青贮+50%燕麦青贮)、C 2(50%玉米青贮+50%苜蓿青贮)、C 3(80%玉米青贮+20%苜蓿干草)、C 4(50%燕麦青贮+50%苜蓿干草)、C 5(70%玉米青贮+10%燕麦青贮+20%苜蓿青贮)、C 6(65%玉米青贮+15%燕麦青贮+25%苜蓿青贮)和C 7(50%玉米青贮+20%燕麦青贮+30%苜蓿青贮)共构成11种发酵底物。结果表明:4种单一饲料在各时间点的产气量(GP)玉米青贮最高,苜蓿青贮最低(P<0.05);7种组合不同时间点产气特点为,C 3的GP最高,C 4最低(P<0.05)。4种单一饲料的快速降解部分产气量(a)和产气速率常数(c)分别为玉米青贮和苜蓿干草最高,与其他单一饲料存在显著差异(P<0.05);7种组合中的a和c均以C 2最高;慢速降解部分产气量(b)和潜在产气量(a+b)均以C 3最高,亦均显著高于其他组合(P<0.05)。体外发酵48 h后,4种单一饲料中玉米青贮的干物质消失率(DMD)显著高于其他3种(P<0.05);培养液的pH介于6.27~6.72,且各组间差异显著(P<0.05);氨态氮(NH 3-N)浓度燕麦青贮最高(P<0.05)。7种组合的DMDC 2显著低于C 5和C 7(P<0.05);pH介于6.40~6.69,其中C 3显著低于其他6种(P<0.05);NH 3-N的浓度C 1与C 2显著高于其他5种(P<0.05)。4种单一粗饲料的总挥发性脂肪酸(TVFA)为玉米青贮显著高于苜蓿青贮和干草(P<0.05);7种组合培养48 h后,培养液的TVFA浓度C 2和C 4显著低于C 5和C 6(P<0.05)。综上,玉米青贮的体外发酵GP、DMD、TVFA及乙酸浓度均最高;苜蓿青贮的体外发酵GP较低,发酵速度慢;不同组合的综合组合效应值(MFAEI)均为正值,由高到低依次为C 4、C 2、C 5、C 1、C 3、C 6、C 7。

The aim of this study was to investigate the fermentation performance and combination effect of high-quality forages treated with beef cattle rumen fluid in vitro.The four forages studied were packaged silage of maize,oat and alfalfa,and alfalfa hay.The feeds were sourced from the Loess Plateau region.Seven mixtures of the four forages were also tested:C 1(50%maize silage+50%oat silage),C 2(50%maize silage+50%alfalfa silage),C 3(80%maize silage+20%alfalfa hay),C 4(50%oat silage+50%alfalfa hay),C 5(70%maize silage+10%oat silage+20%alfalfa silage),C 6(65%maize silage+15%oat silage+25%alfalfa silage)and C 7(50%maize silage+20%oat silage+30%alfalfa silage).It was found that:at each time point,the gas production(GP)was highest for maize silage and lowest for alfalfa silage,among the four forages tested singly(P<0.05).For the seven mixtures,the highest and lowest GP was from C 3 and C 4,respectively(P<0.05).Gas production was partitioned into a rapid degradation component(a),a slow degradation component(b),and a gas production rate constant(c).Among the four single feeds,maize silage had the highest value of a,while alfalfa hay had the highest value of c,and values differed significantly(P<0.05)between the four single feeds for both a and c.Among the seven feed mixtures,the highest values of a and c occurred in mixture C 2,while values of c,and potential gas production(a+b)were higher(P<0.05)in mixture C 3,than in the other mixtures.Among the four single feeds,the highest dry matter digestibility(DMD)after 48 h was for maize silage,and there were also significant differences among the other three forages(P<0.05);the pH values differed among the four feeds(P<0.05),and ranged from 6.27 to 6.72;while the NH 3-N concentration was the highest in oat silage(P<0.05).For the seven feed mixtures,the DMD of C 2 was lower than C 5 and C 7(P<0.05);the pH values ranged from 6.40 to 6.69,and the pH value of C 3 was significantly lower than that of the other six feed mixtures(P<0.05);The NH 3-N concentration of C 1 and C 2 was higher than that of the other five feed mixtures(P<0.05).Among the four single forages,the total volatile fatty acids(TVFA)alfalfa silage and hay were significantly lower than for maize and oat silage(P<0.05).Among the feed mixtures,the TVFA concentrations of C 2 and C 4 were significantly lower than those of C 5 and C 6(P<0.05).In conclusion,the GP,DMD,TVFA and acetic acid production from maize silage was the highest,while the lowest GP occurred in alfalfa silage.For the seven feed mixtures positive associative effects were detected,and according to the‘MAFEI’index,these effects ranked C 4>C 2>C 5>C 1>C 3>C 6>C 7.