不同水平干苹果渣对育肥牛体外产气量、发酵参数、营养物质消化率和生长性能的影响

[目的] 研究不同水平干苹果渣替代精料补充料中部分能量饲料对西门塔尔育肥牛瘤胃体外产气量、发酵参数、营养物质消化率和生长性能的影响。[方法] 分别采用0、4%、8%、12%、16%干苹果渣替代肉牛精料补充料中部分玉米,应用体外产气法测定各组日粮体外发酵0~72 h的产气量;体外产气试验结束后,测定瘤胃液的发酵参数;体外发酵48 h测定人工瘤胃液营养成分体外消化率;利用4%、8%、12%干苹果渣替代精料补充料中部分玉米,测定饲喂不同替代比例日粮育肥牛的增重指标。[结果] 4%干苹果渣组总产气量显著（P<0.05）高于8%和16%干苹果渣组,各组样品产气主要集中在4~24 h,36~72 h产气量趋于平稳。产气后各组pH值均在正常范围;8%干苹果渣组氨态氮浓度显著（P<0.05）高于12%和16%干苹果渣组;4%和8%干苹果渣组的乙酸、异丁酸、丁酸、异戊酸和戊酸浓度显著（P<0.05）高于其他各组。对照组的干物质、粗蛋白和中性洗涤纤维消化率显著（P<0.05）高于其他各组,8%干苹果渣组酸性洗涤纤维消化率显著（P<0.05）高于其他各组。各组育肥牛的试验期间总增重和日增重差异均不显著（P>0.05）。[结论] 4%干苹果渣替代精料补充料中部分玉米可提高西门塔尔育肥牛瘤胃体外发酵产气量,4%和8%干苹果渣替代精料补充料中部分玉米可提高瘤胃液中氨态氮浓度及挥发性脂肪酸浓度,有利于瘤胃发酵和饲粮消化。     

体外产气法评定蒸汽压片玉米对牦牛体外瘤胃发酵参数及甲烷产量的影响

本试验采用体外产气法研究饲粮中蒸汽压片玉米替代比例对牦牛体外瘤胃发酵参数及甲烷产量的影响。体外培养底物精粗比为7∶3,采用单因素完全随机试验设计,设置11个组,蒸汽压片玉米替代精料中玉米的比例分别为0(对照组)、10%、20%、30%、40%、50%、60%、70%、80%、90%、100%,每组3个重复。发酵48 h后,测定总产气量、甲烷产量及培养液pH、氨态氮(NH_3-N)及挥发性脂肪酸(VFA)含量。结果表明:1)随着精料中蒸汽压片玉米替代比例的增加,24和48 h总产气量、产气速率、干物质降解率(DMD)均有上升趋势,100%蒸汽压片玉米组显著高于对照组(P0.05);100%蒸汽压片玉米组瘤胃培养液总挥发性脂肪酸(TVFA)、丙酸含量显著升高(P0.05),培养液乙酸含量和乙酸/丙酸(A/P)、NH_3-N含量显著降低(P0.05),对pH无显著影响(P0.05)。2)随着蒸汽压片玉米替代比例的增加,甲烷产量均有下降趋势,100%蒸汽压片玉米组甲烷产量显著低于对照组(P0.05)。综上所述,蒸汽压片玉米100%替代精料中玉米可显著降低甲烷产量,提高瘤胃液TVFA含量,降低A/P,具有较好的瘤胃发酵效果。     

不同中性洗涤纤维与淀粉比例饲粮对体外瘤胃发酵的影响

本试验旨在探讨不同中性洗涤纤维与淀粉比例(NDF/starch)饲粮对体外瘤胃发酵的影响。选用玉米青贮、燕麦干草和玉米调整饲粮NDF/starch,配制0.86(Ⅰ)、1.13(Ⅱ)、1.56(Ⅲ)和2.38(Ⅳ)4种NDF/starch的全混合日粮,采用3头体况良好且装有永久性瘤胃瘘管的荷斯坦奶牛作为瘤胃液的供体动物,利用体外发酵试验结合动态产气实时记录技术,测定累积产气量(2、6、12、24、36、48 h)、产气动力学参数和瘤胃发酵特性指标。结果表明:1)随着饲粮NDF/starch的提高,发酵48 h体外干物质降解率逐渐下降,I、Ⅱ组均显著高于Ⅲ、Ⅳ组(P0.05);48h累积产气量和理论最大产气量呈下降趋势,Ⅳ组显著低于其他各组(P0.05);组间达1/2理论最大产气量的时间、最大产气速率无显著差异(P0.05)。2)NDF/starch对发酵液氨态氮和微生物蛋白浓度影响不显著(P0.05)。3)随着饲粮NDF/starch的增加,p H、乙酸/丙酸、乙酸/总挥发性脂肪酸呈显著或极显著增加(P0.05或P0.01),总挥发性脂肪酸、丙酸、丁酸浓度及丙酸/总挥发性脂肪酸呈显著或极显著下降(P0.05或P0.01)。4)不同NDF/starch饲粮营养水平与体外发酵参数相关性分析表明,48 h累积产气量、理论最大产气量与淀粉含量、中性洗涤可溶物(NDS)含量、中性洗涤可溶物/粗蛋白质(NDS/CP)、非纤维性碳水化合物(NFC)含量呈极显著正相关关系(P0.01),而与中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)含量呈极显著负相关关系(P0.01)。综合而言,本试验条件下,体外产气法测定饲粮NDF/starch在0.86~1.13之间对体外瘤胃发酵较好。     

牛至精油对绵羊瘤胃体外养分降解率、发酵特性及CH4产量的影响

试验旨在研究牛至精油对绵羊瘤胃体外养分降解率、发酵特性及CH₄产量的影响。采用单因素完全随机试验设计,在培养液中分别添加0(CON)、100(EO₁)、400(EO₂)、700(EO₃)和1000 mg·L^-1(EO₄)牛至精油,每组4个重复。发酵48 h后测定养分降解率、发酵参数及不同时间总产气量和CH₄产量。结果表明:1)与CON组相比,干物质降解率、粗蛋白降解率、中性洗涤纤维降解率在EO₁组中均显著升高(P<0.05),在EO₄组中均显著降低(P<0.05),EO₂组中均无显著差异(P>0.05),干物质降解率在EO₃组中显著降低(P<0.05),添加牛至精油对酸性洗涤纤维降解率(ADFD)无显著影响(P>0.05);2)EO₁组pH最低,而总挥发性脂肪酸(TVFA)、丙酸浓度最高,且乙酸浓度显著高于EO₂、EO₃和EO₄(P<0.05),但乙酸/总挥发性脂肪酸显著低于EO₃、EO₄组(P<0.05),乙酸/丙酸显著低于CON组(P<0.05)。与CON组相比,牛至精油组丁酸、丁酸/总挥发性脂肪酸和氨氮浓度显著降低(P<0.05);3)发酵36 h后,总产气量、甲烷产量均随牛至精油的添加而逐渐降低,与CON组相比,EO₁组发酵18~48 h总产气量显著降低(P<0.05),EO₂、EO₃和EO₄组总产气量、CH₄产量在发酵18 h后均显著降低(P<0.05),EO₄组甲烷百分比在发酵12~36 h显著降低(P<0.05)。综上所述,在绵羊瘤胃体外培养液中添加牛至精油能够提高饲粮养分降解率,调控瘤胃发酵,降低总产气量和甲烷产量,体外条件下添加量不应高于100 mg·L^-1。     

饲粮中添加燕麦干草对绵羊体外发酵的影响

为明确燕麦干草不同添加量对绵羊瘤胃体外发酵的影响,选用6头体况相似、体重 (70.24±2.03) kg且装有永久性瘤胃瘘管的杂种(美利奴♂×蒙古羊♀)公羊作为瘤胃液供体动物进行体外发酵试验,按粗饲料中燕麦干草和青贮玉米比例(干物质基础)将饲粮分为C₁组(精料+100%玉米青贮),C₂组(精料+50%玉米青贮+50%燕麦干草)和C₃组(精料+100%燕麦干草)。饲粮精粗比为35∶65。结果表明:1)饲粮中加入燕麦干草显著提高了体外发酵的产气量和甲烷产量(P<0.05);2)饲粮中加入燕麦干草对体外培养液pH没有明显影响,但显著提高了培养液NH₃-N浓度(P<0.05),未明显改变试羊瘤胃丙酸摩尔比,但TVFA浓度、乙酸、丁酸摩尔比以及乙酸/丙酸上升;3)燕麦干草的加入显著提高了绵羊瘤胃体外发酵的IVDMD和IVCPD,对饲粮中营养物质的降解有促进作用;4)多项指标综合指数以C₂组最高,C₁组最低。由此可知,在精料水平相同的条件下,燕麦干草与青贮玉米1∶1混合作为粗饲料能改善绵羊的瘤胃内环境,提高瘤胃发酵能力,得到最大组合效应。     

低淀粉饲粮条件下不同瘤胃降解淀粉水平对体外瘤胃发酵的影响

本试验旨在研究玉米作为淀粉来源的低淀粉饲粮条件下不同瘤胃降解淀粉(RDS)水平对体外瘤胃发酵的影响。以3头安装有永久性瘤胃瘘管的健康荷斯坦奶牛作为瘤胃液供体,各组分别以不同RDS水平饲粮作为发酵底物,体外产气法测定培养48 h时产气量和瘤胃发酵参数以及24 h时瘤胃微生物区系变化。结果表明:1)随着饲粮RDS水平的提高,体外培养48 h时产气量、潜在产气部分和产气速率呈线性升高(P0.05),快速发酵部分产气量呈线性下降(P0.05),干物质消失率呈线性升高(P0.05);2)随着饲粮RDS水平的提高,体外培养48 h时发酵液微生物蛋白、乙酸、丙酸、丁酸和总挥发性脂肪酸浓度呈线性升高(P0.05),pH和氨态氮浓度没有显著变化(P0.05);3)随着饲粮RDS水平的提高,体外培养24 h时发酵液中白色瘤胃球菌和嗜淀粉瘤胃杆菌的相对数量呈线性升高(P0.05),黄色瘤胃球菌、琥珀酸丝状杆菌、溶纤维丁酸弧菌、牛链球菌和溶淀粉琥珀酸单胞菌的相对数量没有显著变化(P0.05)。综合考虑,低淀粉饲粮条件下提高RDS水平有利于瘤胃发酵。     

冷季放牧补饲对甘肃高山细毛后备母羊瘤胃代谢参数及瘤胃微生物数量的影响

旨在筛选出甘肃高山细毛羊后备母羊科学合理的补饲料,改变牧区由于营养供给不足导致甘肃高山细毛羊2.5岁才能配种的饲养方式。试验选择甘肃高山细毛羊(12月龄)48只,随机分为试验a(1号料)、b(2号料)、c(3号料)组和对照组(不补饲),进行90 d放牧补饲试验。结果表明,1)瘤胃pH试验a组和b组差异极显著(P<0.01)、c组显著(P<0.05)低于对照组,瘤胃氨态氮、蛋白氮、总氮浓度试验组均极显著高于对照组(P<0.01),总挥发性脂肪酸(VFA)试验a组和b组均极显著高于对照组(P<0.01),b组显著高于c组(P<0.05);乙酸和丙酸摩尔比a组极显著高于对照组(P<0.01),b和c组显著高于对照组(P<0.05);丁酸摩尔比a组极显著高于c组(P<0.01);乙/丙b组显著低于对照组(P<0.05)。2)瘤胃纤维降解菌和原虫数目试验组均极显著(P<0.01)或显著(P<0.05)高于对照组。综上所述,补饲均能正向影响甘肃高山细毛羊后备母羊瘤胃代谢参数及瘤胃微生物数量,以1号料补饲效果最优,2号料也能起到理想效果。     

复合酶制剂对瘤胃发酵及泌乳早期奶牛生产性能的影响

本试验旨在研究添加不同水平复合酶制剂对瘤胃发酵及奶牛生产性能的影响。试验一以奶牛全混合日粮作为底物进行体外瘤胃发酵试验,分为4组,即对照组不添加酶制剂,试验1、2和3组的酶制剂添加量分别为日粮浓度的0.10%、0.15%和0.20%,每组设9个重复。每个重复准确称取0.500 g底物,在体外发酵产气自动记录装置上发酵48 h,测定其发酵参数和营养物质降解率。结果表明:复合酶制剂显著提高发酵液中总挥发性脂肪酸和乙酸浓度(P<0.05);试验组中粗蛋白(P<0.05)和中性洗涤纤维(P<0.01)降解率显著高于对照组。试验二选择体重、胎次、泌乳天数和产奶量相近的泌乳早期荷斯坦奶牛36头,采用随机区组设计分为4组,即对照组和试验1、2和3组,对照组不添加酶制剂,试验1、2和3组分别添加0.10%、0.15%和0.20%的酶制剂,每组9个重复,试验期8周,测定产奶量和乳成分含量,计算3.5%乳脂校正乳。结果表明:复合酶制剂显著提高3.5%乳脂校正乳产量(P<0.05),0.10%、0.15%和0.20%组比对照组分别提高3.88、4.27和2.26 kg·d^-1。0.15%组的乳脂率显著高于对照组(P<0.05),比对照组高12.7%。结论添加复合酶制剂有利于瘤胃发酵和提高生产性能,且添加量为0.15%时效果较好。     

甜高粱的饲用价值及其绵羊体外瘤胃发酵产气性能研究

本试验旨在研究不同收割时期饲用甜高粱的饲用价值及其绵羊体外瘤胃发酵产气性能,分别对8-11月收割的甜高粱(大奖3180,标记为S₁、S₂、S₃与S₄)的养分含量及相对饲喂价值(RFV)、总可消化养分(TDN)、干物质采食量(DMI)、可消化干物质(DDM)和牧草相对饲用品质(RFQ)进行评价。利用体外模拟发酵产气技术评定不同收割时期的甜高粱在3、6、9、12、24、36和48 h体外产气规律,估算降解率。结果表明,1)不同收割时期的甜高粱的干物质(DM)、粗蛋白(CP)、中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)、粗脂肪(EE)和粗灰分(Ash)含量差异均显著(P<0.05)。2)不同收割时期的甜高粱的RFV、DMI、RFQ呈现出S₁>S₄>S₃>S₂,差异极显著(P<0.001)。S₁和S₄的TDN和DDM含量差异不显著(P>0.05),但极显著高于S₂和S₃(P<0.001)。3)在培养12 h之前,不同收割时期的甜高粱产气量(GP)差异极显著(P<0.001),且S₃的GP最高;24 h后,S₄的GP显著高于S₂(P<0.05);培养36 h后不同收割时期的甜高粱GP差异不显著(P>0.05)。4)不同时期收割的甜高粱在发酵12、24、48 h的干物质消失率(DMD)均无显著差异(P>0.05)。综上结果,8月对黄土高原丘陵沟壑区甜高粱进行收割时饲用价值最好。     

不同添加剂对薯渣与玉米秸秆混贮饲料发酵品质及牛瘤胃降解率的影响

研究4种不同添加剂对薯渣与玉米秸秆混贮饲料发酵品质以及牛瘤胃降解率的影响,并筛选出适宜的添加剂。试验采用密封塑料桶进行混贮,薯渣和玉米秸秆混贮水分含量控制在70%(混贮比例为1∶2),设置了对照组(CK)、微贮博士组(处理1)、青贮邦组(处理2)、拉巴克思复合添加剂组(处理3)以及亚芯组(处理4)5个处理,每个处理3个重复,贮存期60 d。采用实验室化学分析法及半体内试验测定第60天发酵品质、有氧稳定性、瘤胃降解率。结果表明各处理组和对照组(CK组)的感官评定结果无明显差异;经过发酵品质分析测定,4种添加剂处理均改善了薯渣饲料的发酵品质,其中处理4组的乳酸含量最高(P<0.01),pH和氨态氮含量最低(P<0.05);各添加剂处理均提高了薯渣混贮饲料的有氧稳定性,其中以处理4组效果最佳(P<0.01),有氧稳定时间为162 h,比CK组延长50 h,其次是处理2组(P<0.01)、处理3组(P<0.01),处理1组改善效果不明显;在瘤胃中培养48 h后,处理组干物质(DM)瘤胃降解率显著高于CK组(P<0.05),粗蛋白质(CP)瘤胃降解率极显著高于CK组(P<0.01);处理4组的NDF瘤胃降解率最高,显著高于处理3(P<0.05),但与其他处理组的NDF瘤胃降解率差异不显著(P>0.05);处理4组的ADF瘤胃降解率显著高于3组和CK组(P<0.05),与处理1组和处理2组差异不显著(P>0.05)。处理1组的淀粉瘤胃降解率比CK提高2.83%(P<0.01),其他各处理组间淀粉的牛瘤胃降解率无显著差异(P>0.05)。综上,添加剂处理对薯渣与玉米秸秆混贮饲料的发酵品质、有氧稳定性、瘤胃降解率等均有改善作用,其中以亚芯组处理效果最好。     

不同厚度蒸汽压片处理对玉米活体外瘤胃发酵的影响

试验以未处理的玉米及两种不同厚度蒸汽压片玉米(压片厚度为1.5mm,SFC 1.5;压片厚度为2.0mm,SFC 2.0)为材料,采用营养成分分析、活体外人工瘤胃产气量试验,研究不同厚度蒸汽压片处理对玉米营养成分、淀粉糊化度和活体外发酵特性的影响。结果表明,不同厚度蒸汽压片处理显著降低玉米粗蛋白质和粗脂肪含量(P0.05),显著提高了玉米的淀粉糊化度(P0.05);并且显著提高了玉米在瘤胃液内的淀粉降解率和体外产气速度(P0.05),显著降低了瘤胃液中氨态氮(NH3-N)浓度(P0.05);降低压片厚度(1.5和2.0mm),蒸汽压片玉米淀粉糊化度增加约17%(88.76%和71.60%),SFC 1.5的体外产气速度、4h干物质和淀粉产气率显著高于SFC 2.0(P0.05)。不同厚度蒸汽压片处理对玉米瘤胃48h产气量、12和24h瘤胃液pH、总挥发性脂肪酸产量及乙酸、丙酸、乙酸/丙酸、异丁酸、异戊酸、戊酸摩尔比影响均不显著(P0.05)。综上所述,不同厚度蒸汽压片处理可显著提高玉米在瘤胃内淀粉降解率和降解速度,降低瘤胃液中氨态氮浓度,而对48h产气量及其他发酵参数没有明显影响。     

Effects of wet corn gluten feed and intake level on diet digestibility and ruminal passage rate in steers

Twelve ruminally cannulated Jersey steers (BW = 534 kg) were used in an incomplete Latin square design experiment with a 2 x 2 factorial arrangement of treatments to determine the effects of wet corn gluten feed (WCGF) and total DMI level on diet digestibility and ruminal passage rate. Treatments consisted of diets formulated to contain (DM basis) steam-flaked corn, 20% coarsely ground alfalfa hay, and either 0 or 40% WCGF offered once daily for ad libitum consumption or limited to 1.6% of BW (DM basis). Two consecutive 24-d periods were used, each consisting of 18 d for adaptation, 4 d for collection, and a 2-d in situ period. Rumens of all steers were evacuated once daily at 0, 4, 8, and 12 h after feeding. Chromic oxide (10 g/[steer*d]) was fed as a digestibility marker, and steers were pulse-dosed with Yb-labeled alfalfa hay to measure ruminal particulate passage rate. Dacron bags containing 5 g of steam-flaked corn, WCGF, or ground (2-mm screen) alfalfa hay were placed into the rumens of all steers and removed after 3, 6, 12, or 48 h. Wet corn gluten feed increased percent apparent total-tract digestion of OM (P < 0.01), NDF (P < 0.01), and starch (P < 0.03), decreased (P < 0.01) ruminal total VFA concentration, increased (P < 0.01) ruminal NH3 concentration, and increased (P < 0.01) ruminal pH. Wet corn gluten feed also increased (P < 0.01) ruminal passage rate of Yb. Limit feeding decreased (P < 0.01) percent apparent total-tract digestion of both OM and NDF, ruminal total VFA concentration (P < 0.01), and ruminal fill (P < 0.01), but increased (P < 0.01) ruminal NH3 concentration. Apparent total-tract digestion of starch was not affected (P = 0.70) by level of DMI. A DMI level x hour interaction (P < 0.01) occurred for ruminal pH. Limit feeding increased ruminal pH before and 12 h after feeding, but decreased ruminal pH 4 h after feeding compared with diets offered ad libitum. A diet x DMI level interaction (P < 0.02) occurred for in situ degradation of alfalfa hay, with dietary addition of WCGF increasing (P < 0.02) the extent of in situ alfalfa hay degradation in steers fed for ad libitum consumption. This study suggests that WCGF increases OM and NDF digestion, and that limit feeding diets once daily might depress OM and NDF digestion, possibly due to decreased stability of the ruminal environment.     

体外产气法评价青海高原反刍家畜常用粗饲料组合效应

采用体外产气法评价青海高原反刍家畜的3种常用粗饲料青贮玉米（Zea mays）秸秆、苜蓿（Medicago sativa）青干草和燕麦（Arrhenatherum elatius）青干草按0∶100、25∶75、50∶50、75∶25和100∶0的比例两两组合时的发酵特性。结果表明,理论最大产气量、48 h产气量分别与中性洗涤可溶物/粗蛋白（NDS/CP）（P＜0.001）、有机物（OM）（P＜0.01）,中性洗涤可溶物（NDS）（P＜0.05）呈正相关关系,分别与酸性洗涤纤维（ADF）（P＜0.001）、中性洗涤纤维（NDF）（P＜0.05）和粗蛋白（CP）（P＜0.05）呈负相关关系;产气速率常数分别与OM（P＜0.001）、NDS（P＜0.001）和NDS/CP（P＜0.01）呈正相关关系,分别与ADF、NDF均呈极显著负相关关系（P＜0.001）;产气延滞时间与ADF（P＜0.01）和NDF（P＜0.05）呈正相关关系,分别与OM（P＜0.01）、NDS（P＜0.05）和NDS/CP（P＜0.05）呈负相关关系,说明了组合牧草体外发酵产气程度主要受非结构性碳水化合物与粗蛋白比例的影响。3种粗饲料两两组合搭配时,青贮玉米秸秆与苜蓿青干草以25∶75比例、青贮玉米秸秆与燕麦青干草以50∶50比例、苜蓿青干草与燕麦青干草以25∶75或50∶50比例组合时较为合适,且随着发酵时间的延长,各组合均呈现组合效应量逐渐减弱的变化趋势。     

小麦秸秆与米糠粕瘤胃体外发酵组合效应研究

为了探讨小麦秸秆与米糠粕间的组合效应,采用体外产气法评价了小麦秸秆与米糠粕按100:0(RBM0)、75:25(RBM25)、50:50(RBM50)、25:75(RBM75)、0:100(RBM100)的比例组合后的发酵特性。结果表明,1)在产气特性方面,随着米糠粕比例的增加,12,24,48 h累计产气量(GP)、理论最大产气量(HM)和产气速率(B)逐渐增大,而体外延滞时间(Lag)逐渐降低,各比例之间差异显著(P<0.05)。2)在体外发酵12,24,48 h时,当米糠粕占25%时,小麦秸秆与米糠粕的产气量产生最大组合效应(P<0.05)。3)当米糠粕占75%时,小麦秸秆与米糠粕的干物质降解率(DMD)、中性洗涤纤维降解率(NDFD)、酸性洗涤纤维降解率(ADFD)最大,各比例之间差异显著(P<0.05);当米糠粕占25%时,小麦秸秆与米糠粕的DMD产生最大的组合效应(P<0.05);当米糠粕占75%时,小麦秸秆与米糠粕的NDFD、ADFD产生最大组合效应(P<0.05)。4)当米糠粕占75%时,小麦秸秆与米糠粕组合体外发酵48 h的乙酸、丙酸、丁酸以及总挥发性脂肪酸浓度最高,乙酸/丙酸最低。5)48 h累计产气量、产气速率与干物质(DM)、粗蛋白(CP)、粗灰分(Ash)以及中性洗涤可溶物(NDS)极显著正相关(P<0.01),与中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)、有机物(OM)、半纤维(HC)以及中性洗涤可溶物/粗蛋白(NDS/CP)呈极显著负相关(P<0.01);理论最大产气量与DM、CP、Ash、NDS显著正相关(P<0.05),与NDF、ADF、OM和HC显著负相关(P<0.05);Lag与NDS/CP极显著正相关(P<0.01)。本试验结果提示,在本试验条件下,从产气量及干物质降解率的组合效应方面来看,小麦秸秆与米糠粕的最优组合是75:25;从纤维降解率的组合效应方面来看,小麦秸秆与米糠粕的最优组合是25:75。     

Evaluation of finishing performance,carcass characteristics,acid-resistant E. coli and total coliforms from steers fed combinations of wet corn gluten feed and steam-flaked corn

Crossbred beef steers (n = 615) were used in a 152-d experiment to compare steam-flaked corn (SFC) diets containing 0, 30, or 60% wet corn gluten feed (WCGF). On d 114 to 118, ruminal and fecal samples were collected from 180 steers and analyzed for pH, VFA, and total and acid-resistant Escherichia coli and coliforms. Acid resistance of E. coli and coliform populations was determined by exposure of the samples for 1 h in pH 2, 4, and 7 citric acid/sodium phosphate buffers. Increasing levels of WCGF linearly decreased total ruminal VFA (P = 0.01) and total fecal VFA (P = 0.06), but linearly increased ruminal and fecal acetate:propionate (P < 0.01) ratio and ruminal and fecal pH (P < 0.05). Feeding increasing WCGF levels resulted in a quadratic response (P < 0.05) with respect to numbers of ruminal E. coli and total coliform populations resistant to pH 4 exposure. Steers fed 30% WCGF had higher (0.7 log units) ruminal E. coli and total coliforms after exposure at pH 4 compared to steers fed 0 or 60% WCGF. Populations of E. coli and total coliforms at pH 2 and 7 were similar for all dietary treatments. Dietary WCGF linearly increased DMI (P = 0.07) and liver abscesses (P = 0.03) and linearly decreased dietary NEg (P = 0.02). Average daily gain and feed efficiencies were greatest when steers were offered 30% WCGF (quadratic, P < 0.05). Dietary manipulations that reduce acid concentrations may not correspond to changes in acid resistance of E. coli and total coliform populations detected in the gastrointestinal tracts of cattle. Moderate levels of WCGF complement SFC finishing diets.     

不同品种玉米的化学成分、淀粉糊化度及活体外发酵特性的比较

本试验以常规玉米品种农大108(CAU108)、优质蛋白玉米9409(HQPC9409)和高油玉米(HOC)为材料,采用化学成分分析、活体外人工瘤胃消化试验和产气量试验,研究玉米品种对化学成分、淀粉糊化度和活体外瘤胃发酵特性的影响。结果表明,3个不同玉米品种的蛋白质、脂肪、淀粉含量、淀粉糊化度、48 h产气量、产气速度、理论最大产气量、12和24 h干物质及淀粉消化率均存在显著差异(P<0.05),在3个品种中,CAU108品种的各项能量指标均优于HQPC9409和HOC,但不同品种玉米的活体外瘤胃发酵参数(pH、NH3-N、VFA)差异不显著(P>0.05)。由本试验得出,CAU108玉米较其他2个品种具有提高反刍动物生产性能和饲料转化效率的潜力。     

玉米的加工处理对饲料营养物质消化率的影响

选用3头装有永久瘤胃瘘管的云南黄牛,饲喂5种含不同加工处理（粉碎、粉碎蒸汽、干碾压、湿碾压、蒸汽压片）玉米的日粮,在精粗比为50：50的条件下,采用5×5不完全拉丁方设计,测定5种日粮中干物质,有机物质、蛋白质、淀粉、中性洗涤纤维、酸性洗涤纤维的消化率以研究不同处理对饲料消化率的影响。试验结果表明,在5组处理玉米日粮中,蒸汽压片玉米日粮组干物质（DM）、有机物质（OM）和粗蛋白（cP）全消化道消化率显著提高（P〈0．05）。全消化道淀粉消化率各处理玉米日粮组间存在差异,蒸汽压片与粉碎蒸汽玉米日粮组显著高于干碾压与湿碾压玉米日根组（P〈0．05）,而与粉碎玉米日粮组间没有显著差异（P〉0．05）。中性洗涤纤维（NDF）与酸性洗涤纤维（ADF）的消化率在5组处理玉米日粮间没有显著差异（P〉0．05）．     

Influence of dietary urea level on digestive function and growth performance of cattle fed steam-flaked barley-based finishing diets

Four Holstein steers (282 kg) with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square experiment to evaluate the influence of dietary urea level (0, 0.4, 0.8, and 1.2%, DM basis) in a steam-flaked barley-based finishing diet on digestive function. There were no treatment effects (P > 0.20) on ruminal digestion of OM and ADF. Increasing dietary urea level increased (linear, P < 0.01) ruminal starch digestion. Ruminal degradability of protein in the basal diet (no supplemental urea) was 60%. Increasing dietary urea level did not increase (P > 0.20) ruminal microbial protein synthesis or nonammonia N flow to the small intestine. There were no treatment effects (P > 0.20) on total-tract ADF digestion. Total tract digestion of OM (quadratic, P < 0.01) and starch (linear, P < 0.05) increased slightly with increasing urea level. Urea supplementation increased (linear, P < 0.01) ruminal pH 1 h after feeding; however, by 3 h after feeding, ruminal pH was lower (cubic, P < 0.05) with urea-supplemented diets. Urea supplementation did not affect (P > 0.20) ruminal molar proportions of acetate and propionate. One hundred twenty crossbred steers (252 kg; approximately 25% Brahman breeding) were used in an 84-d feeding trial (five pens per treatment) to evaluate treatment effects on growth performance. Daily weight gain increased (linear, P = 0.01) with increasing urea level, tending to be maximal (1.53 kg/d; quadratic, P = 0.13) at the 0.8% level of urea supplementation. Improvements in ADG were due to treatment effects (linear, P < 0.01) on DMI. Urea supplementation did not affect (P > 0.20) the NE value of the diet for maintenance and gain. Observed dietary NE values, based on growth performance, were in close agreement with expected based on tabular values for individual feed ingredients, averaging 100.4%. We conclude that with steam-flaked barely-based finishing diets, ruminal and total-tract digestion of OM and ruminal microbial protein synthesis may not be increased by urea supplementation. In contrast, ADG was optimized by dietary inclusion of 0.8% urea. Urea supplementation may not enhance the net energy value of steam-flaked barely-based finishing diets when degradable intake protein is greater than 85% of microbial protein synthesis.     

Effects of adding polyclonal antibody preparations on ruminal fermentation patterns and digestibility of cows fed different energy sources

Nine ruminally cannulated cows fed different energy sources were used to evaluate an avian-derived polyclonal antibody preparation (PAP-MV) against the specific ruminal bacteria Streptococcus bovis, Fusobacterium necrophorum, Clostridium aminophilum, Peptostreptococcus anaerobius, and Clostridium sticklandii and monensin (MON) on ruminal fermentation patterns and in vivo digestibility. The experimental design was three 3 × 3 Latin squares distinguished by the main energy source in the diet [dry-ground corn grain (CG), high-moisture corn silage (HMCS), or citrus pulp (CiPu)]. Inside each Latin square, animals received one of the feed additives per period [none (CON), MON, or PAP-MV]. Dry matter intake and ruminal fermentation variables such as pH, total short-chain fatty acids (tSCFA), which included acetate, propionate, and butyrate, as well as lactic acid and NH(3)-N concentration were analyzed in this trial. Total tract DM apparent digestibility and its fractions were estimated using chromic oxide as an external marker. Each experimental period lasted 21 d. Ruminal fluid sampling was carried out on the last day of the period at 0, 2, 4, 6, 8, 10, and 12 h after the morning meal. Ruminal pH was higher (P = 0.006) 4 h postfeeding in MON and PAP-MV groups when compared with CON. Acetate:propionate ratio was greater in PAP-MV compared with MON across sampling times. Polyclonal antibodies did not alter (P > 0.05) tSCFA, molar proportion of acetate and butyrate, or lactic acid and NH(3)-N concentration. Ruminal pH was higher (P = 0.01), 4 h postfeeding in CiPu diets compared with CG and HMCS. There was no interaction between feed additive and energy source (P > 0.05) for any of the digestibility coefficients analyzed. Starch digestibility was less (P = 0.008) in PAP-MV when compared with CON and MON. In relation to energy sources, NDF digestibility was greater (P = 0.007) in CG and CiPu vs. the HMCS diet. The digestibility of ADF was greater (P = 0.002) in CiPu diets followed by CG and HMCS. Feeding PAP-MV or monensin altered ruminal fermentation patterns and digestive function in cows; however, those changes were independent of the main energy source of the diet.