本试验旨在利用体外瘤胃发酵法评定不同类型饲料的营养价值。试验1比较了不同粗饲料(麦壳、羊草、稻草、高能饲草、美国苜蓿、国产苜蓿、全株玉米青贮、花生秧青贮、玉米秸青贮和杂交高粱青贮)的体外发酵特性,试验2比较了不同蛋白质饲料(豆粕、棉籽粕、菜籽粕、芝麻粕和棕榈粕)的体外发酵特性,试验3比较了不同饲料组合(稻草组合、苜蓿组合、羊草组合和麦壳组合,各组合精料相同)的体外发酵特性。结果表明:玉米青贮(包括全株玉米青贮和玉米秸青贮)和苜蓿(包括美国苜蓿和国产苜蓿)体外发酵48 h的产气量(GP)、干物质降解率(DMD)和总挥发性脂肪酸(TVFA)浓度均显著高于其他粗饲料(P<0.05);麦壳的GP和DMD则显著低于其他粗饲料(P<0.05)。豆粕体外发酵48 h的GP最高,其发酵速度最快。不同蛋白质饲料的有机物降解率(OMD)和DMD差异较大,以豆粕的OMD与DMD最高,显著高于其他蛋白质饲料(P<0.05);微生物蛋白(MCP)浓度也以豆粕最高,显著高于芝麻粕和棕榈粕(P<0.05)。对于不同饲料组合,中性洗涤纤维与粗蛋白质比值(NDF/CP)越小,其发酵速度越快、降解率越高。相关性分析显示,NDF/CP与DMD呈显著负相关(P<0.05)。结果提示:1)对于粗饲料,玉米青贮和苜蓿类饲料的体外发酵GP较高,发酵速度较快;麦壳的体外发酵GP较低,发酵速度较慢。2)对于蛋白质饲料,豆粕的体外发酵GP、发酵速度和MCP浓度均高于其他蛋白质饲料。3)对于饲料组合,NDF/CP会影响体外发酵特性,NDF/CP越小,其发酵延滞期越短、发酵速度越快、降解率越高。

This experiment was conducted to evaluate the nutritive value of different feeds by in vitro ruminal fermentation method. Experiment 1 was used to compare the in vitro fermentation characteristics of different forages (wheat husk, Chinese wildrye hay, rice straw, high-energy forage, American alfalfa, Chinese alfalfa, whole-plant corn silage, peanut vine silage, corn straw silage and hybrid sorghum silage), experiment 2 was used to compare the in vitro fermentation characteristics of different protein feeds (soybean meal, cottonseed meal, rapeseed meal, sesame meal and palm meal), and experiment 3 was used to compare the in vitro fermentation characteristics of different feed combinations (rice straw combination, alfalfa combination, Chinese wildrye hay combination and wheat husk combination, and the concentrate in those combinations was the same). The results showed as follows: after 48 h in vitro fermentation, the corn silages (including whole-plant corn silage and corn straw silage) and alfalfas (including American alfalfa and Chinese alfalfa) had higher gas production (GP), dry matter degradability (DMD) and total volatile fatty acid (TVFA) concentration compared with other forages (P<0.05), while the GP and DMD of wheat husk were significantly lower than those of other forages (P<0.05). After 48 h in vitro fermentation, soybean meal had the highest GP and the fastest fermentation rate. There were greater differences in organic matter degradability (OMD) and DMD among different protein feeds, and the OMD and DMD of soybean meal were the highest and significantly higher than those of other protein feeds (P<0.05); the microbial crude protein (MCP) concentration of soybean meal was also the highest and significantly higher than that of sesame meal and palm meal (P<0.05). For different feed combinations, the smaller neutral detergent fiber/crude protein (NDF/CP), the faster fermentation rate, and the higher degradability. The correlation analysis showed that the NDF/CP was negatively correlated to DMD (P<0.05). These results suggest that, 1) for forages, corn silages and alfalfas have the higher GP and faster fermentation rate, while the wheat husk has the lower GP and the slower fermentation rate; 2) for protein feeds, the GP, fermentation rate and MCP concentration of soybean meal are higher than those of other protein feeds; 3) for feed combinations, NDF/CP affect the in vitro fermentation characteristics of feeds, which is manifested as the smaller NDF/CP, the shorter fermentation lag phase, the faster fermentation rate, and the higher degradability.