【作者】 孟杰；

【导师】 孟庆翔；

【作者基本信息】 中国农业大学 ， 动物营养与饲料科学， 2014， 博士

【摘要】 为了探究不同农副产品饲料资源提高牛肉生产的可能性,本试验通过全国农副产品饲料资源预测、活体外瘤胃发酵试验、肉牛饲养试验、血液指标测定、屠宰试验以及胴体和肉品质分析，研究了不同农副产品饲料资源对于肉牛的营养价值，以期在一定程度上为肉牛生产提供相关技术指导。试验一：目的是提出我国2012年农副产品饲料产量估测值,并分析我国农副产品饲料玉米秸、大豆秸和白酒糟的化学成分与能量价值,为三种农副产品饲料在肉牛生产中的应用提供技术依据。根据农作物草谷比公式,推算出2012年我国农副产品饲料中玉米秸产量为24960万吨,大豆秸产量为2048万吨,白酒糟产量为2882.9万吨。分析证实,在几种农副产品饲料中,有机物含量由高到低依次为白酒糟、玉米秸、大豆秸、裹包玉米秸,且各自差异显著(P<0.05)。白酒糟粗脂肪、粗蛋白、中性洗涤不溶氮和酸性洗涤不溶氮含量显著高于其它原料(P<0.05)。裹包玉米秸的粗灰分、中性洗涤纤维和酸性洗涤纤维含量显著高于其它秸秆(p<0.05)。根据INRA模型估测的玉米秸、大豆秸、白酒糟和裹包玉米秸总能分别为18.45、18.33、20.88和17.91MJ/kgDM;维持净能值分别为5.52、5.19、1.38和4.18MJ/kgDM;增重净能分别为2.80、2.55、0.21和1.80MJ/kgDM。小结：我国农副产品饲料玉米秸、大豆秸和白酒糟的产量巨大,且各类原料均适合作为反刍动物的粗饲料。试验二：研究不同农副产品饲料及其组成的全混合饲粮的活体外产气量、瘤胃发酵、甲烷产生和瘤胃消化率变化。结果表明,不同副产品饲料的体外发酵72h的产气量(B),大豆秸显著高于其它饲料(P<0.05),且产气速率(c)显著快于其它饲料(P<0.05)。关于体外发酵24h后测定气体成分,裹包发酵玉米秸的甲烷产量显著高于白酒糟(P<0.05)。不同农副产品饲料的活体外瘤胃发酵24h的瘤胃pH值和总挥发性脂肪酸均无显著差异,白酒糟的氨态氮、丙酸、异戊酸和戊酸含量显著高于其它饲料(P<0.05),但其乙酸含量显著低于其他组(P<0.05)。就体外瘤胃消化48h干物质消化率而言,大豆秸显著高于其它饲料(P<0.05),裹包玉米秸青贮显著低于玉米秸和大豆秸(P<0.05)。关于由不同副产品组成的混合饲粮,其体外发酵72h各处理饲粮间理论产气量(B)、产气速率(c)和发酵延滞期(1ag)差异均不显著(P>0.05),体外发酵24hC后H4产量与CO2无显著差异(P>0.05)。大豆秸饲粮组和裹包玉米秸饲粮组的氨态氮含量显著高于玉米秸组(P<0.05)；体外瘤胃消化48h的干物质消化率各组间均无显著差异(P>0.05)。小结：与玉米秸相比,大豆秸改善了瘤胃发酵类型,是较优良的粗饲料资源,具有较大的开发利用潜力。试验三：本试验研究不同农副产品饲料按照干物质基础取代部分玉米秸饲喂肉牛,对肉牛生长性能的影响。选取12月龄左右、体重一致的西门塔尔×本地杂种公牛60头(平均体重335±15kg),根据体重随机分成4组,每组15头,单栏栓系饲养。试验期分为22周,其中包含预饲期1周。试验日粮为全混合日粮,精粗比6：4,大豆秸组(SBD)使用大豆秸取代玉米秸的30%,白酒糟组(DDD)使用白酒糟取代30%的玉米秸,裹包玉米秸(PMSD)使用发酵裹包玉米秸取代玉米秸,替代比例均为干物质基础。实验结果表明,0-7周和8-14周两个阶段PMSD组干物质采食量显著高于MSD组和SBD组(P<0.05)；15-21周PMSD组干物质采食量显著高于SBD组。0-21周干物质采食量和单位体重的干物质采食量方面DDD组与PMSD组显著高于MSD组与SBD组(P<0.05)。平均日增重MSD组、SBD组、DDD组和PMSD组分别为1.56kg、1.68kg、1.58kg和1.72kg,但是差异不显著。小结：使用酒糟替代部分玉米秸在本试验中表现出可以促进动物的采食量；使用玉米秸发酵饲草完全替代玉米秸的PMSD组,显著的提高了采食量,在数值上表现出最优的日增重。小结：饲喂PMSD饲粮可以促进肉牛采食,提高日增重。试验四：研究不同农副产品饲料按照干物质基础取代部分玉米秸饲喂肉牛对肉牛血液生化指标的影响。在试验末期,于晨饲前空腹静脉采血,进行血清生化指标的测定。试验结果表明,MSD组血糖含量显著高于DDD组(P<0.05)；MSD组和DDD组尿素氮的含量显著高于SBD组(P<0.05),结合试验三的结果,血液当中较低的尿素氮含量证实了MSD组和DDD组日增重相对较少的原因。不同农副产品饲料饲喂肉牛对血清当中总胆固醇、甘油三酯和总蛋白含量差异不显著。小结：白酒糟组在糖代谢方面优于玉米秸组,大豆秸组在促进氮沉积方面要优于玉米秸组和白酒糟组。综合血液指标认为,用大豆秸和裹包玉米秸青贮饲喂肉牛,可以获得较好的氮沉积效果。试验五：本试验研究不同农副产品饲料饲喂肉牛对屠宰性能和胴体肉品质的影响。饲养试验结束后,从每个处理组随机抽取10头体况相近的牛只进行屠宰,测定屠宰性能、胴体品质和肉质指标。结果表明,MSD组和DDD组肌纤维剪切力值显著大于SBD组(P<0.05)；排酸后pH值MSD组和SBD组显著低于DDD组和PMSD组(P<0.05)；MSD组蒸煮损失显著高于SBD组和DDD组(P<0.05),PMSD组与MSD组和DDD组差异不显著。DDD组脂肪色亮度(L*)显著大于SBD组和PMSD组(P<0.05)。DDD组和PMSD组胆固醇含量显著高于MSD组和SBD组(P<0.05)。小结：各处理组之间屠宰率、净肉率、高档部位重、眼肌面积、大理石纹等级、肉色和肉常规成分方面没有显著差异。但是对影响口感的剪切力、排酸后pH值、蒸煮损失和胆固醇方面差异显著。结果显示,使用一部分大豆秸替代玉米秸饲喂肉牛,似乎对改善与牛肉风味有关的品质特征有某种作用。更多还原

【Abstract】 In order to explore the possibilities for different alternative feed sources (AFS) to improving beef production, a study was conducted to predict the amount of alternative feed sources, to compare the nutritive values of different alternative feed sources, growth performance,carcass traits and meat quality of beef cattle using in vitro gas production experiment, feeding-slaughtering trial.Experiment1:This study was designed to estimate the national amount of alternative feed sources in2012and to analyze the chemical composition and energetic values of maize stover, soybean straw, dry distiller’s grain and packed maize stover silage. According to the ratio of grains to straw, we calculated the annual amount of AFS in China2012, indicating249.6million tons for maize stover,2048million tons for soybean straw,2882.9million tons for dry distiller’s grain, respectively. Chemical analysis showed that dry distiller’s grain had the highest organic content, followed by maize stover, soybean straw and packed maize stover silage. Dry distiller’s grain had highest (P<0.05) contents of EE, CP, NDIN and ADIN than other AFS, while packed maize stover silage had higher (P<0.05) Ash, NDF and ADF than other AFS. According to the INRA model, the GE content of maize stover, soybean straw, dry distillers grains and packed maize stover silage were18.45,18.33,20.88and17.91MJ/kgDM, respectively; the content of NEm was5.52,5.19,1.38and4.18MJ/kgDM, respectively; the content of NEg was2.80,2.55,0.21and1.80MJ/kgDM, respectively. In conclusion, a huge amount of the alternative feed sources annually available in China such as maize stover, soybean straw and dry distiller’s grain, would be used as ruminant feed resources.Experiment2:This experiment was conducted to evaluate the effect of AFSs and their mixed ration on in vitro gas production GP, ruminal fermentation, methane production and ruminal digestibility. The results showed that soybean straw had significantly higher (P<0.05)72h GP and rate of GP (c) than other AFS. The yield of methane production was significantly higher (P<0.05) for packed maize stover silage than dry distiller’s grains. There were no significant differences (P>0.05) in pH values and total volatile fatty acids between groups. Dry distiller’s grains had significantly higher(P<0.05) concentrations of NH3-N, propionate, isovalerate and valerate, but lower acetate than other AFS. As to in vitro DM digestibility, soybean straw was the highest, followed by maize stover, dry distiller’s grains and packed maize stover silage. The ration mixed with AFS showed that there were no significant differences (P>0.05) in potential GP (B), rate of GP (c), fermentation lag time (lag) among rations. Also there were no significant difference (P>0.05) in CH4and CO2production between rations for24h in vitro fermentation. The concentration of NH3-N were significantly higher (P<0.05) for soybean straw ration and packed maize stover silage ration than maize stover ration. Also there was no significant difference (P>0.05) in in vitro digestibility among rations. In conclusion, compared with maize stover, soybean straw has a positively impact on the rumen fermentation pattern and may be potentially used as a good roughage source for ruminant feeding. Experiment3:This experiment was conducted to investigate the effect of feeding different AFS to growing and finishing cattle on growth performance. Sixty crossbred Simmental x local breed bulls aged12months old (average bodyweight335±15kg) were selected and allotted to4treatment diets with15bulls in each of treatments. All bulls were tethered using neck straps in tie stalls and were individually fed. The trial period was22weeks including1-wk for adaptation and21-wk for data collection. The treatment diets were:(1) maize stover diet with40%maize stover (MSD);(2) soybean straw diet with30%maize stover replaced by soybean straw (SBD);(3) dry distiller’s grains diet with30%maize stover replaced by dry distiller’s grain (DDD);(4) packed maize stover diet with40%packed maize stover silage (PMSD). The results showed that dry matter intakes were significantly higher (P<0.05) for PMSD than MSD and SBD during0-7week and8-14week, for PMSD than SBD during15-21week, and for DDD and PMSD than MSD and SBD during0-21weeks. The ADG values were1.56,1.68,1.58and1.72kg for MSD, SBD, DDD and PMSD respectively, although their differences were not significant (P>0.05). In conclusion, dry distiller’s grains and packed maize stover silage used as replacement of maize stover had a promotion effect on feed intake. The packed maize stover silage showed a potential function in improvement of average daily gain, feed intake and feed conversion of beef cattle.Experiment4:This study was conducted to investigate the effect of replacement of different AFS for corn stover in beef cattle diets on blood biochemical indicators. At the end of the feeding trial, the blood samples were taken through the neck before the morning feeding for serum biochemical parameters. The results showed that blood glucose concentration was significantly higher (P<0.05) for MSD than DDD. Urea nitrogen content were significantly higher (P<0.05) for MSD and DDD than that of SBD. The results combined with Experiment3showed that lower blood urea nitrogen was in line with the relatively low average daily gain for MSD and DDD. There were no significant differences (P>0.05) in serum total cholesterol, triglycerides and total protein content, respectively. In summary, DDD was better in glucose metabolism than MSD; SBD was better in promotion of nitrogen deposition than MSD and DDD. Based on blood biochemical indicators, feeding beef cattle with soybean straw and packed maize stover silage would be beneficial to nitrogen deposition.Experiment5:This study was designed to investigate the effect of different AFS on slaughtering performance and carcass quality. Ten bulls with similar body weight were selected at the end of feeding trial and slaughtered for measurement of slaughtering performance, carcass quality and meat chemical composition. The results showed that MSD and DDD groups had significantly higher (P<0.05) shear force values than SBD group. The pH values were significantly (P<0.05) lower for MSD and SBD groups than DDD and PMSD groups. The cooking loss were significantly higher (P<0.05) for MSD than SBD and DDD. The fat color brightness (L*) was significantly greater (P<0.05) for DDD group than SBD and PMSD groups. The cholesterol content was significantly higher (P<0.05) for DDD and PMSD groups than MSD and SBD groups. In summary, there were no significant differences in dressing percentage, meat percentage, high-priced meat cuts, ribeye area, marbling score, meat colour and meat chemical compositions among dietary treatment. There were significant differences in shear force, pH values, cooking loss and cholesterol compositions. In general, the use of soybean straw to replace some maize stovers in the beef cattle diet showed a potential to some extent for improvement of beef quality in relation to its flavor.更多还原