饲粮非纤维性碳水化合物/中性洗涤纤维对12月龄荷斯坦后备奶牛生长性能、营养物质表观消化率及瘤胃甲烷产量的影响

本试验旨在通过监测饲粮非纤维性碳水化合物/中性洗涤纤维(NFC/NDF)对12月龄荷斯坦后备奶牛生长性能、营养物质表观消化率及瘤胃甲烷(CH_4)产量的影响,获得我国生产模型下的CH_4排放规律和CH_4转化因子,为提高奶牛能量利用效率、建立国家或区域性温室气体排放清单和探索减排策略提供科学依据和支撑。选取45头体况良好的12月龄的荷斯坦后备奶牛,随机分为3组(每组15头):低NFC/NDF组(饲粮NFC/NDF=1.12)、中NFC/NDF组(饲粮NFC/NDF=1.36)和高NFC/NDF组(饲粮NFC/NDF=1.64),试验期为63 d,包括14 d的预试期和49 d的正试期。结果表明:1)高NFC/NDF组的干物质采食量(DMI)、有机物采食量(OMI)、非纤维性碳水化合物采食量(NFCI)、总能摄入量(GEI)、平均日增重(ADG)以及干物质(DM)和粗蛋白质(CP)表观消化率显著高于中NFC/NDF组和低NFC/NDF组(P0.05)。2)随着饲粮NFC/NDF的增加,CH_4产量、CH_4产量/代谢体重、CH_4产量/DMI、CH_4产量/OMI、CH_4产量/中性洗涤纤维采食量(NDFI)和甲烷能(CH_4-E)产量显著降低(P0.05)。作为CH_4转化因子的CH_4-E产量/GEI在中NFC/NDF组和高NFC/NDF组之间没有显著差异(P0.05),但二者均显著低于低NFC/NDF组(P0.05)。3)瘤胃CH_4排放量与荷斯坦后备奶牛的体重、DMI、饲粮NDF含量呈显著正相关关系(P0.05),而与饲粮NFC/NDF呈显著负相关(P0.05),其中基于DMI和NDFI的CH_4排放量预测模型的决定系数最高(0.86)。由此可见,将饲粮NFC/NDF由1.12提高至1.64时,能够显著提高12月龄荷斯坦后备奶牛的DMI、ADG以及DM和CP表观消化率,且能够显著降低瘤胃CH_4产量。可基于DMI和NDFI建立12月龄后备奶牛瘤胃CH_4排放量的预测模型。     

饲粮NDF/NFC对泌乳高峰期奶牛瘤胃甲烷排放量、营养物质表观消化率及生产性能的影响

本试验采用六氟化硫(SF6)示踪技术测定生产条件下泌乳奶牛瘤胃甲烷(CH4)排放量,旨在研究饲粮中性洗涤纤维/非纤维性碳水化合物(NDF/NFC)对泌乳高峰期奶牛甲烷排放量、营养物质表观消化率及生产性能的影响。试验选用体重(564.04±24.97)kg、胎次(1.58±0.23)胎、泌乳天数(88.00±15.32)d、产奶量(20.83±0.77)kg/d的荷斯坦奶牛12头,随机分成3组,每组4头。各组饲粮NDF/NFC分别为1.14、1.30、1.55。试验期为24 d,包括14 d预饲期和10 d正试期。结果表明:(1)低NDF组甲烷排放量、甲烷能极显著低于高NDF组(P≤0.01),甲烷/干物质采食量、甲烷能/总能摄入量在3个处理组间有极显著差异(P≤0.01);(2)各营养物质的表观消化率在3组间无显著差异(P> 0.05);(3)低NDF组日增重显著高于高NDF组(P <0.05)。综上,在不影响奶牛健康和生产性能的前提下,NDF/NFC为1.14的低NDF组饲粮能显著降低泌乳高峰期奶牛瘤胃甲烷排放量。     

饲粮NDF/NFC对泌乳中期奶牛瘤胃甲烷排放量、营养物质表观消化率及生产性能的影响

试验采用六氟化硫(SF_6)示踪技术测定生产条件下泌乳奶牛瘤胃甲烷排放量,旨在研究饲粮NDF/NFC(中性洗涤纤维/非纤维性碳水化合物)对泌乳中期奶牛甲烷排放量、营养物质表观消化率和生产性能的影响。试验选用体重(649.54±18.44)kg、胎次(1.42±0.15)胎、泌乳天数(170.08±19.04)d、产奶量(18.46±0.89)kg/d的荷斯坦奶牛12头,随机分配到3组,每组4头。各组饲粮NDF/NFC分别为1.44、1.65、1.82。试验期为28 d,包括14 d预饲期和14 d正试期。结果表明:①泌乳中期奶牛瘤胃甲烷排放量、甲烷能、甲烷/干物质采食量及甲烷能/总能摄入量在3个处理组间均有极显著差异(P0.01);②低NDF组NFC的表观消化率显著高于高NDF组(P0.05);③生产性能和日增重在3组间无显著差异(P0.05)。综上,在不影响奶牛健康和生产性能的前提下,NDF/NFC为1.44的低NDF组饲粮能显著降低泌乳中期奶牛瘤胃甲烷排放量。     

饲粮NDF/NFC对泌乳后期奶牛瘤胃甲烷排放量、营养物质表观消化率及生产性能的影响

为研究不同中性洗涤纤维/非纤维性碳水化合物(NDF/NFC)饲粮对泌乳后期奶牛甲烷排放量、营养物质消化率和生产性能的影响,试验选用体重(777.46±27.31)kg、胎次(1.5±0.15)胎、泌乳天数(242.92±15.28)d、产奶量(18.75±0.62)kg/d的奶牛12头,随机分配到3组,每组4头。各组饲粮NDF/NFC分别为2.10(精粗比为42:58)、1.96(精粗比为37:63)、1.52(精粗比为30:70),采用六氟化硫(SF_6)示踪技术测定自然状态下泌乳奶牛甲烷排放量。预试期14 d,正试期9 d。结果表明:饲喂不同NDF/NFC饲粮的泌乳后期奶牛甲烷排放量、甲烷能、单位干物质采食量的甲烷排放量以及单位总能摄入量的甲烷能均有显著差异;随着NDF/NFC降低,奶牛生产性能、饲料转化率和营养物质消化率无显著差异。综上,在不影响奶牛健康和生产性能的前提下,NDF/NFC为1.52的低NDF组饲料能显著降低泌乳后期奶牛瘤胃甲烷排放量。     

不同NDF水平饲粮对羔羊生长性能、营养物质消化、消化道重量及瘤胃乳头发育的影响

本试验旨在研究不同中性洗涤纤维（NDF）水平饲粮对羔羊生长性能、营养物质表观消化率、消化道重量及瘤胃乳头发育的影响。选用60只体况良好,体重为（3.23±0.20）kg的初生母羔羊,随机分为4组,每组5个重复,每个重复3只羊。试验羔羊于10日龄补饲开食料,开食料NDF水平分别为12%（12NDF组）、16%（16NDF组）、20%（20NDF组）和24%（24NDF组）的饲粮。试验期60 d,饲养试验所有羔羊均随母哺乳,消化试验所有羔羊不随母哺乳。结果显示：1）随着日龄的增加,羔羊的体重极显著增加（P<0.01）;各日龄阶段日增重均差异不显著（P>0.05）;随日龄的增加,羔羊干物质采食量（DMI）极显著增加（P<0.01）,饲喂不同NDF水平饲粮,各组羔羊DMI差异不显著（P>0.05）。2）24NDF组羔羊干物质（DM）、有机物（OM）采食量和总能（GE）摄入量显著高于16NDF、20NDF组（P<0.05）。24NDF组羔羊粗蛋白（CP）采食量显著高于20NDF组（P<0.05）;24NDF组羔羊中性洗涤纤维（NDF）、酸性洗涤纤维（ADF）采食量极显著高于20NDF组（P<0.01）,20NDF组极显著高于16NDF、12NDF组（P<0.01）;24NDF组羔羊DM、OM表观消化率显著低于12NDF、16NDF组（P<0.05）,24NDF组GE表观消化率显著低于16NDF组（P<0.05）,但20NDF、24NDF组NDF、ADF表观消化率显著或极显著高于12NDF组（P<0.05或P<0.01）;24NDF组羔羊粪能显著高于12NDF、16NDF和24NDF组（P<0.05）。各试验组CP表观消化率和消化能差异不显著（P>0.05）。3）12NDF组羔羊全胃重显著高于16NDF、20NDF组（P<0.05）。12NDF组羔羊瘤胃重显著高于20NDF组（P<0.05）。12NDF组羔羊瘤胃占宰前活重的比例显著高于16NDF、20NDF和24NDF组（P<0.05）。12NDF组羔羊十二指肠重及十二指肠占宰前活重的比例显著高于16NDF组（P<0.05）。其余各指标均差异不显著（P>0.05）。综上所述,母羔羊在0~60日龄最适的NDF水平为16%~20%。     

饲粮非纤维性碳水化合物(NFC)与中性洗涤纤维(NDF)比例对育成期杜寒杂交母羊生长性能、营养物质消化率和甲烷产量的影响

旨在借助开路式循环呼吸测热系统研究饲粮不同非纤维性碳水化合物/中性洗涤纤维(NFC/NDF)比例对育成期(48~55kg)杜寒杂交母羊生产性能、营养物质消化率及甲烷产量的影响。选用30只体重(48±0.50)kg的杜泊(♂)×小尾寒羊(♀))母羊,采用单因素试验设计,将试验动物随机分到饲粮NFC/NDF=0.78组(精粗比为35∶65,自由采食)、NFC/NDF=1.03组(精粗比为50∶50,限饲)和NFC/NDF=2.17组(精粗比为65∶35,限饲)3个处理组中,每个处理组10只羊。试验期为32d,包括17d预试期和15d正试期。试验分为自由采食组和限饲组两种饲养模式,各组的能量和粗蛋白质采食量均相同,以饲粮NFC/NDF为0.78自由采食组的平均日增重作为NFC/NDF为1.03组和2.17组的限饲标准。试验羊只定期晨饲前称重,记录每日采食量;在正试期内测定甲烷产量、饲粮能量和饲粮营养物质表观消化率。结果表明:1)限饲条件下饲粮NFC/NDF为2.17组的饲料转化效率显著高于自由采食条件下饲粮NFC/NDF为0.78组的饲粮转化效率(P0.05),饲粮NFC/NDF为1.03组与另外两组皆无显著性差异(P0.05)。2)当饲粮NFC/NDF比例由0.78增加至2.17时,3个处理组的干物质表观消化率、有机物表观消化率、总能表观消化率和总能代谢率皆显著提高(P0.05),NFC/NDF=2.17组的粗蛋白质表观消化率显著高于NFC/NDF=0.78组(P0.05),两组皆与NFC/NDF=1.03组无显著差异(P0.05)。另外,随着饲粮NFC/NDF比例的增加,NFC/NDF=2.17组的NDF表观消化率显著高于NFC/NDF=0.78组和NFC/NDF=1.03组(P0.05),后两组间无显著差异(P0.05)。3)NFC/NDF=2.17组的甲烷日排放量为32.53L·d~(-1),显著低于NFC/NDF=0.78组的58.03L·d~(-1)和NFC/NDF=1.03组的63.17L·d~(-1)(P0.05),后两组间的甲烷日排放量无显著差异(P0.05),3组的单位代谢体重的甲烷日排放量具有相同的变化规律。随着饲粮NFC/NDF比例的增加,NFC/NDF=2.17组的单位干物质采食量的甲烷排放量、单位有机物采食量的甲烷排放量和单位可消化有机物的甲烷排放量皆显著低于NFC/NDF=1.03组(P0.05),NFC/NDF=0.78组的以上指标与另外两组相比皆无显著差异(P0.05);单位总能摄入量的甲烷能排放量、单位消化能摄入量的甲烷能排放量、单位代谢能摄入量的甲烷能排放量具有相同的变化规律。NFC/NDF=1.03组的单位中性洗涤纤维采食量的甲烷排放量和单位可消化中性洗涤纤维采食量的甲烷排放量显著高于NFC/NDF=0.78组和NFC/NDF=2.17组(P0.05),后两组间无显著差异(P0.05)。另外,单位日增重的甲烷排放量和单位可消化酸性洗涤纤维的甲烷排放量在3个处理组之间无显著差异(P0.05)。综合生长性能、饲粮各营养物质表观消化率、能量代谢及甲烷排放水平,对育成期(48~55kg)杜寒杂交母羊限制饲喂NFC/NDF为2.17的饲粮是最佳的碳减排措施。     

刈割时期和加工方式对柠条锦鸡儿饲用价值的影响

选用4头装有瘤胃瘘管的西门答尔牛,用常规全收粪法测定柠条锦鸡儿(Caraganakorshinskii)的消化率,用瘤胃尼龙袋法测定瘤胃降解率;选用荷斯坦育成母牛54头,分别饲喂当年生花期、结实期和2年生结实期切碎、揉碎及粉碎柠条锦鸡儿,测定饲喂效果。结果表明:干物质(DM)、有机质(OM)、粗蛋白质(CP)瘤胃降解率以开花期最高(P<0.05),当年生结实期显著高于2年生结实期老枝(P<0.05);中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)和瘤胃降解率,当年生开花期与结实期差异不显著,但皆显著高于2年生老枝(P<0.05);OM消化率以花期揉碎处理最高(P<0.05),结实期揉碎和花期切碎间差异不显著,但显著高于其它处理;CP、NDF和ADF消化率均以花期揉碎最高,与结实期揉碎差异不显著,但显著高于其它处理;每千克代谢体重柠条锦鸡儿和日粮干物质采食量均以结实期较高;加工方式以粉碎采食量高;结实期揉碎处理的采食率、日增重最高(P<0.05),每千克增重消耗精料最少,增重成本最低。     

饲粮peNDF对奶公牛反刍、消化、生产性能及瘤胃发酵的影响

试验通过研究饲粮不同物理有效中性洗涤纤维（peNDF）含量对育肥奶公牛反刍、消化、生产性能和瘤胃发酵的影响,旨在为奶公牛生产中配制适宜peNDF含量的全混合日粮（TMR）提供依据。选择30头11月龄、体重（345.57±23.53） kg、健康的中国荷斯坦奶公牛（未阉割）,随机分为试验Ⅰ、Ⅱ和Ⅲ组,每组10头,分别饲喂8.00 mm孔径筛上物peNDF （peNDF_8.00）含量为12.40%、13.75%和14.85%的3种饲粮。结果表明：试验Ⅰ组奶公牛的饲粮采食次数显著高于Ⅱ和Ⅲ组（P<0.05）,试验Ⅱ和Ⅲ组反刍时间、每千克干物质和中性洗涤纤维反刍时间显著高于试验Ⅰ组（P<0.05）。3组间干物质采食量（DMI）、peNDF采食量、平均日增重（ADG）、料重比（F/G）及干物质（DM）、粗蛋白质（CP）、中性洗涤纤维（NDF）、酸性洗涤纤维（ADF）、钙（Ca）和磷（P）表观消化率差异均不显著（P>0.05）。试验Ⅲ组瘤胃pH显著高于Ⅰ和Ⅱ组（P<0.05）,而丙酸浓度显著低于其他2组（P<0.05）。试验Ⅱ和Ⅲ组瘤胃乙丙比、乙酸和氨态氮（NH₃-N）浓度显著高于试验Ⅰ组（P<0.05）。在本试验条件下,3种不同peNDF_8.00水平饲粮对育肥奶公牛生产性能和养分表观消化率影响不显著,饲粮peNDF_8.00为13.75%和14.85%时,奶公牛反刍时间、瘤胃乙丙比、乙酸和NH₃-N浓度显著增加,可使奶公牛保持较佳瘤胃发酵性能。     

不同饲养模式下饲粮非纤维性碳水化合物/中性洗涤纤维对生长期杜寒杂交母羊生长性能、营养物质表观消化率和甲烷产量的影响

本试验旨在借助开路式呼吸测热系统研究饲粮非纤维性碳水化合物(NFC)/中性洗涤纤维(NDF)对生长期杜寒杂交母羊生长性能、营养物质表观消化率及甲烷产量的影响。采用单因素试验设计,选取体况良好、体重为(27.8±0.5)kg的母羊30只,根据体重一致原则,分配到3组,各组饲粮NFC/NDF分别为0.78(精粗比为35∶65)、1.03(精粗比为50∶50)、2.17(精粗比为65∶35),每组10只羊。试验期为25 d,包括3 d调整期、7 d预试期和15 d正试期。结果表明:在NFC/NDF=0.78组自由采食和其他组限饲条件下,3组试验羊的初始体重和结束体重以及平均日增重无显著性差异(P0.05)。当饲粮NFC/NDF由0.78增加至2.17时,干物质采食量显著降低(P0.05),干物质、有机物和粗蛋白质表观消化率显著增加(P0.05),NDF和酸性洗涤纤维(ADF)表观消化率无显著性差异(P0.05)。当饲粮NFC/NDF由0.78增加至2.17时,甲烷能、单位干物质采食量的甲烷产量、单位总能摄入量的甲烷能产量显著降低(P0.05)。结果提示,在平均日增重一致的前提下,高NFC/NDF饲粮料重比较低,且甲烷转化效率较低;对生长期杜寒杂交母羊来说,限饲条件下饲喂NFC/NDF为2.17的饲粮在提高生产效益的同时又兼顾甲烷减排,效果相对最佳。     

米曲霉对奶牛瘤胃降解率及日粮表观消化率的影响

[目的]本文旨在研究不同水平的米曲霉日粮对奶牛瘤胃降解率及日粮表观消化率的影响。[方法]试验选用三头安装永久性瘤胃瘘管的健康荷斯坦奶牛,采用3×3拉丁方试验设计,试验分为三组,A组为基础日粮,B组和C组分别为基础日粮添加米曲0.04%和0.08%DM。[结果]米曲霉显著提高了日粮干物质、粗蛋白、酸性洗涤纤维和中性洗涤纤维的瘤胃降解率,其中B组的瘤胃降解率影响效果优于A组和C组,且差异显著（P〈0.05）。三组日粮干物质和酸性洗涤纤维的表观消化率大小顺序为B〉C〉A,但各组间差异不显著（P〉0.05）;B组日粮CP和NDF消化率均显著高于A组和C组（P〈0.05）,但A组和C组差异均不显著（P〉0.05）。[结论]适量添加米曲霉（0.04%DM）有利于提高奶牛瘤胃DM、CP、ADF和NDF的降解率及日粮CP和NDF的表观消化率。     

Effects of dietary nonprotein nitrogen on performance, digestibility, ruminal characteristics, and microbial efficiency in crossbred steers

Two trials were conducted to evaluate the effects of dietary NPN levels on animal performance, diet digestibility, ruminal characteristics, and microbial efficiency. Experiment 1 was conducted with 24 Holstein x Nellore crossbred steers (350 +/- 20 kg of BW) distributed in 6 blocks to evaluate intake and digestibility of nutrients and performance. The diets consisted of 70% corn silage and 30% concentrate (DM basis) and were formulated to contain 12.5% CP (DM basis). Treatments consisted of 0, 15.5, 31, and 46.5% of dietary N as NPN. There were no treatment differences in the daily intakes of DM (P = 0.47), OM (P = 0.60), CP (P = 0.24), nonfiber carbohydrates (NFC; P = 0.74), or TDN (P = 0.63); however, NDF intake decreased linearly as NPN increased (P = 0.02). Additionally, no effects of NPN were observed on apparent total tract digestibility of DM (P = 0.50), OM (P = 0.53), NDF (P = 0.63), or NFC (P = 0.44). The apparent total tract digestibility of CP increased linearly (P = 0.01), but ADG (1.14 kg/d) was not influenced (P = 0.96) as NPN increased. In Exp. 2, 4 ruminally and abomasally cannulated steers (300 +/- 55 kg of BW) were fed the same diet used in Exp. 1 to evaluate the effects of NPN levels on intake and digestibility of nutrients, ruminal characteristics, and microbial efficiency. There were no differences in the daily intakes of DM (P = 0.22), OM (P = 0.17), CP (P = 0.31), NDF (P = 0.29), or TDN (P = 0.49). However, NFC intake increased linearly (P = 0.02), and there was a quadratic effect (P = 0.01) on intake of ether extract as NPN increased. Ruminal digestibility of CP increased linearly (P = 0.01) with the increase of dietary NPN. There were no differences (P >or= 0.28) in microbial protein synthesis and microbial efficiency among the treatments. The results of these trials suggest that dietary NPN levels (up to 46.5% of total N) can be fed to crossbred steers receiving corn silage-based diets without affecting their growth performance or ruminal protein synthesis.     

饲粮非纤维性碳水化合物/中性洗涤纤维对黔北麻羊瘤胃发酵参数、血浆生化指标和养分消化率的影响

本试验旨在研究不同饲粮非纤维性碳水化合物(NFC)/中性洗涤纤维(NDF)对黔北麻羊瘤胃发酵参数、血浆生化指标和养分消化率的影响。采用3×3拉丁方试验设计,选取6只健康成年黔北麻羊为试验动物,将其分为3组,每组2个重复,每个重复1只羊。试验Ⅰ组、试验Ⅱ组、试验Ⅲ组饲粮NFC/NDF分别为2.14∶1.00、1.05∶1.00、0.40∶1.00(实测值)。试验分3期,每期15 d,包括10 d预试期和5 d正试期。检测指标包括:饲粮养分消化率、瘤胃发酵参数(pH、缓冲力、氨态氮和挥发性脂肪酸浓度、纤维素酶活性)、血浆生化指标(脂多糖、白蛋白、尿素氮、葡萄糖含量及过氧化氢酶、谷草转氨酶、超氧化物歧化酶、谷胱甘肽过氧化物酶活性)。结果显示:1)3个试验组干物质采食量差异不显著(P0.05),试验Ⅲ组各养分消化率均显著低于试验Ⅰ组、试验Ⅱ组(P0.05)。2)试验Ⅰ组瘤胃液pH显著低于试验Ⅱ组、试验Ⅲ组(P0.05);试验Ⅲ组瘤胃液缓冲力显著高于试验Ⅰ组(P0.05),纤维二糖酶活性、乙酸浓度显著低于试验Ⅰ组(P0.05),总挥发性脂肪酸、丁酸浓度显著低于另外2组(P0.05);试验Ⅰ组、试验Ⅱ组、试验Ⅲ组瘤胃液乙酸/丙酸依次升高、丙酸浓度依次下降,各组间差异显著(P0.05);3组间瘤胃液羧甲基纤维素酶、木聚糖酶、微晶纤维素酶活性差异不显著(P0.05)。3)试验Ⅰ组、试验Ⅱ组、试验Ⅲ组血浆脂多糖含量依次显著下降(P0.05),其余血浆生化指标差异不显著(P0.05)。综合来看,过高NFC/NDF对黔北麻羊瘤胃发酵参数和血浆生化指标有不良影响,本试验条件下,饲粮NFC/NDF以1.05∶1.00为宜。     

Neutral detergent fiber concentration of corn silage and rumen inert bulk influences dry matter intake and ruminal digesta kinetics of growing steers

Corn silage with high NDF concentration has the potential to reduce DMI because it has a greater filling effect in the rumen than low-NDF corn silage. Our objective was to determine whether ruminal fill influences DMI to the same extent with low- or high-NDF corn silage-based diets. Eight ruminally cannulated Holstein steers (198 +/- 13 kg) were randomly assigned to a 2 x 2 factorial arrangement of treatments in a replicated 4 x 4 Latin square design with 16-d periods. Treatments were diets containing corn silage from a normal hybrid (low-fiber; LF) or its male-sterile isogenic counterpart (high-fiber; HF), offered for ad libitum consumption to steers with or without rumen inert bulk (RIB). The LF and HF diets contained 33.8 and 50.8% dietary NDF, respectively. Rumen inert bulk was added at 25% of pretrial ruminal volume in the form of plastic-coated tennis balls filled with sand to achieve a specific gravity of 1.1 and a total volume of 7.5 L. No fiber level x inert bulk interactions were detected for DMI or NDF intake (P > 0.10), suggesting that DMI was limited to the same extent by physical fill at both levels of dietary fiber. Addition of RIB decreased DMI by an average of 10.7%, which was 65.5 g/L of added bulk. The HF diet depressed DMI by an average of 15.5%, increased NDF intake 27.1%, and reduced ruminal NDF turnover time by 21.0% compared to the LF diet (P < 0.01), with no effect on ruminal volume or amount of NDF in the rumen (P > 0.10). Addition of RIB also reduced ruminal NDF turnover time and amount of NDF in the rumen (11.8% and 20.7%, respectively; P < 0.01), with no change in ruminal digesta volume (P > 0.10). The HF treatment decreased digestibility of DM and GE (5.5 and 5.7%, respectively; P < 0.01) but increased NDF digestibility (10.4%; P < 0.01) compared to LF. Rumen inert bulk had no effect on digestibility of DM, NDF, or GE (P > 0.10). The lack of reduction in digesta volume with addition of inert fill suggests that DMI of light-weight steers receiving corn silage-based diets within a wide range of NDF concentrations was not regulated by ruminal distension alone.     

Effects of physically effective fiber on chewing activity, ruminal fermentation, and digestibility in goats

The objective of this study was to evaluate the effects of physically effective NDF (peNDF) in goat diets containing alfalfa hay as the sole forage source on feed intake, chewing activity, ruminal fermentation, and nutrient digestibility. Four rumen-fistulated goats were fed different proportions of chopped and ground alfalfa hay in a 4 × 4 Latin square design. Diets were chemically similar but varied in peNDF content: low, moderate low, moderate high, and high. Dietary peNDF content was determined using the Penn State Particle Separator with 2 sieves (8 and 19 mm) or 3 sieves (1.18, 8, and 19 mm). The dietary peNDF content ranged from 1.9 to 11.7% using the 2 sieves and from 15.2 to 20.0% using the 3 sieves. Increasing forage particle length increased intake of peNDF, but decreased DMI linearly (P = 0.05). Ruminating and total chewing time (min/d) were increased linearly (P = 0.001 and 0.007, respectively) with increased dietary peNDF, resulting in a linear reduction (P < 0.001) in the duration of time that ruminal pH was less than 5.8 (10.9, 9.0, 1.2, and 0.3 h/d, respectively). Increasing dietary peNDF tended to increase the molar proportion of propionate linearly (P = 0.08) and decrease the molar proportion of butyrate (P = 0.09), but did not affect total VFA concentration. Increasing dietary peNDF linearly decreased the apparent digestibility of OM, NDF, and ADF in the total tract (P = 0.009, 0.003, and 0.008, respectively). This study demonstrated that increasing the dietary peNDF contained in alfalfa hay forage stimulated chewing activity and improved ruminal pH status, but reduced nutrient intake and efficiency of feed use.     

日粮不同NFC/NDF比对奶山羊瘤胃pH值、挥发性脂肪酸及乳酸含量的影响

试验旨在探讨日粮不同非纤维性碳水化合物/中性洗涤纤维比（NFC/NDF）对奶山羊瘤胃发酵参数的影响。选择6只安装有永久性瘤胃瘘管的关中奶山羊作为试验动物,采用自身对照试验法,共分为4组（分4期进行）,每期10d,依次饲喂NFC/NDF比分别为1.02（Ⅰ期）、1.24（Ⅱ期）、1.63（Ⅲ期）、2.58（Ⅳ期）的4种日粮。结果表明,随着日粮NFC/NDF比的提高瘤胃pH值降低,瘤胃pH值下降速率和下降幅度及pH值低于5.2、5.5、5.8、6.0的持续时间随之加快、延长;瘤胃丙酸、丁酸及总挥发性脂肪酸（TVFA）含量随日粮NFC/NDF比提高呈增加趋势,而乙酸含量及乙酸/丙酸则呈降低趋势;血浆乙酸、丙酸、丁酸及TVFA均呈增加趋势。当日粮NFC/NDF比达2.58时,瘤胃pH值在5.2～5.5之间持续时间每日达7h以上,此时瘤胃乳酸含量较低,血浆及瘤胃TVFA含量显著提高（P〈0.05）。结果表明,随着日粮NFC/NDF比的提高,使瘤胃逐渐处于酸性环境,改变了瘤胃发酵模式;瘤胃pH值的下降主要源于瘤胃TVFA增多,而非乳酸;当日粮NFC/NDF比为2.58时,奶山羊发生亚急性瘤胃酸中毒。     

不同中性洗涤纤维与非纤维性碳水化合物比值饲粮对肉用绵羊甲烷排放的影响

本试验旨在研究不同中性洗涤纤维(NDF)与非纤维性碳水化合物(NFC)比值(NDF/NFC)饲粮对肉用绵羊甲烷排放的影响。试验采用4×4完全拉丁方试验设计,将16只杜泊×小尾寒羊杂交羯羊随机分成4组,每组4只,按维持水平饲喂NDF/NFC分别为3.02(饲粮1)、2.32(饲粮2)、1.58(饲粮3)、1.04(饲粮4)的全混合颗粒饲粮(玉米秸秆为粗饲料来源)。试验共进行4期,每期18 d,包括3 d的调整期、7 d的预试期和8 d的正试期,在正试期内测定甲烷产量、饲粮总能和营养物质表观消化率。结果表明:饲粮2的甲烷日排放量显著高于饲粮3和4(43.43 L/d vs.38.88和35.98 L/d;P0.05)。与饲粮1相比,饲粮2和3的每千克干物质采食量(DMI)甲烷排放量显著增加(38.00 L/kg DMI vs.42.24、41.69 L/kg DMI;P0.05),但是饲粮2、3和4之间差异不显著(P0.05)。随着NDF/NFC的降低,每千克可消化有机物(DOM)的甲烷排放量逐渐降低,饲粮4的每千克DOM的甲烷排放量显著低于饲粮1、2和3(58.78 L/kg DOM vs.75.00、73.35和64.11 L/kg DOM;P0.05)。随着NDF/NFC的降低,每千克中性洗涤纤维采食量(NDFI)或酸性洗涤纤维采食量(ADFI)的甲烷排放量逐渐增加,且各饲粮之间差异显著(P0.05)。综上所述,结合各营养物质表观消化率和甲烷排放效率,在维持水平下,采用NDF/NFC为1.04的玉米秸秆饲粮作为肉用绵羊甲烷减排的饲粮最合适。     

Effects of limit‐feeding diets with different forage‐to‐concentrate ratios on nutrient intake,rumination, ruminal fermentation,digestibility, blood parameters and growth in Holstein heifers

The objective of this study was using a wide range of dietary concentrate levels to investigate the major effects of limit‐feeding on heifers. Twenty‐four Holstein heifers were blocked into six groups and fed with one of four diets containing different levels of concentrate (20%, 40%, 60% and 80% on a dry matter (DM) basis) but with same intakes of metabolizable energy for 28 days. Increasing levels of dietary concentrate caused decreased (P ≤ 0.02) intakes of dry matter (DMI) and neutral detergent fiber and total rumination time, but increased (P < 0.01) nonfiberous carbohydrates intake, ruminal concentrations of NH₃‐N, propionate and butyrate, and digestibility of DM and crude protein. Dietary concentrate levels had no significant effect on most plasma concentrations and body measurements. The corrected average daily gain (CADG) and feed efficency (ADG/DMI, CFE) were linearly increased (P < 0.01) with increasing dietary concentrate levels when gut fill impact was removed. In conclusion, heifers limit‐fed high concentrate diets increased most ruminal fermentation parameters, CADG and CFE with similar body growth and blood metabolites as heifers fed low concentrate diets, and had the potential to be used as an effective feeding strategy in dairy heifers.     

Influence of different supplements and sugarcane (Saccharum officinarum L.) cultivars on intake, digestible variables and methane production of dairy heifers under tropical conditions

The sulphur hexafluoride (SF(6)) gas tracer method was used to measure methane (CH(4)) production of crossbred (3/4 Holstein x Zebu) dairy heifers fed two types of sugarcane (Saccharum officinarum L.; cultivar IAC-862480 (CC1) or cultivar IAC-873184 (CC2)) and supplemented with urea or concentrate. The study was performed at Embrapa Southeast Cattle, S?o Carlos, SP, Brazil, using a completely randomised design. Differences between treatments were significant for digestibility of dry matter, organic matter and energy. When animals were supplemented with urea differences between sugarcane cultivars did occur for NDF consumption, but not for daily methane production. This suggest that variation in chemical composition of sugarcane did not affect bovine ruminal CH(4) emissions. Concentrate inclusion in animal diet increased digestible organic matter intake, improving the nutrient intake by animals, but did not reduce CH(4) production expressed as a percentage of gross energy intake.     

饲粮不同NFC/NDF对肉用绵羊瘤胃pH、氨态氮和挥发性脂肪酸的影响

本试验旨在研究饲粮不同非纤维性碳水化合物/中性洗涤纤维(NFC/NDF)对肉用绵羊瘤胃pH、氨态氮和挥发性脂肪酸的影响.选用(47.21±1.01)kg安装有瘤胃瘘管的杜泊羊(♂)×小尾寒羊(♀)杂交1代肉用公羊12只,采用12×4不完全拉丁方设计,试验分4期进行,每期16 d,分别饲喂NFC/NDF为0.25、0.34、0.36、0.52、0.60、0.80、0.87、1.13、1.30、1.58、2.17和2.49的12种饲粮.结果表明:随着NFC/NDF的增加,试验羊瘤胃pH极显著线性降低(P＜0.01),氨态氮浓度极显著线性增加(P＜0.01),瘤胃总挥发性脂肪酸及丁酸比例呈显著三次曲线变化(P＜0.05),总挥发性脂肪酸中的丙酸、戊酸和异戊酸比例极显著线性增加(P＜0.01),乙酸比例和乙酸/丙酸极显著线性降低(P＜0.01).由此可见,饲粮NFC/NDF对瘤胃pH、氨态氮和挥发性脂肪酸具有显著影响.