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1.
A net carbohydrate and protein system for evaluating cattle diets: I. Ruminal fermentation. 总被引：28，自引：0，他引：28
J B Russell J D O'Connor D G Fox P J Van Soest C J Sniffen 《Journal of animal science》1992,70(11):3551-3561
The Cornell Net Carbohydrate and Protein System (CNCPS) has a kinetic submodel that predicts ruminal fermentation. The ruminal microbial population is divided into bacteria that ferment structural carbohydrate (SC) and those that ferment nonstructural carbohydrate (NSC). Protozoa are accommodated by a decrease in the theoretical maximum growth yield (.50 vs .40 g of cells per gram of carbohydrate fermented), and the yields are adjusted for maintenance requirements (.05 vs .150 g of cell dry weight per gram of carbohydrate fermented per hour for SC and NSC bacteria, respectively). Bacterial yield is decreased when forage NDF is < 20% (2.5% for every 1% decrease in NDF). The SC bacteria utilize only ammonia as a N source, but the NSC bacteria can utilize either ammonia or peptides. The yield of NSC bacteria is enhanced by as much as 18.7% when proteins or peptides are available. The NSC bacteria produce less ammonia when the carbohydrate fermentation (growth) rate is rapid, but 34% of the ammonia production is insensitive to the rate of carbohydrate fermentation. Ammonia production rates are moderated by the rate of peptide and amino acid uptake (.07 g of peptide per gram of cells per hour), and peptides and amino acids can pass out of the rumen if the rate of proteolysis is faster than the rate of peptide utilization. The protein-sparing effect of ionophores is accommodated by decreasing the rate of peptide uptake by 34%. Validation with published data of microbial flow from the rumen gave a regression with a slope of .94 and an r2 of .88. 相似文献
2.
The objectives of this experiment were to study the regression relationship between the in vitro-estimated utilizable crude protein (uCP) and the Cornell Net Carbohydrate and Protein System (CNCPS) crude protein fractions, i.e. PA, PB1, PB2, PB3 and PC of feeds for ruminants, and the possibility of using CNCPS crude protein fractions for the estimation of uCP of feeds for ruminants. The CP, the non-protein nitrogen (NPN), the soluble cru de protein (SCP), the neutral detergent insoluble crude protein (NDICP) and the acid detergent insoluble crude protein (ADICP) of 30 single feeds were determined and the CP fractions, i.e. PA, PB1, PB2, PB3 and PC, were then calculated based on CNCPS. The uCP of the 30 feeds was estimated using the in vitro incubation technique of Zhao and Lebzien (2000). It was found that there was a significant multiple regression relationship between the uCP [g/kg dry matter (DM)] and the CNCPS crude protein fractions, i.e. PA (% DM), PB1 (% DM), PB2 (% DM), PB3 (% DM) and PC (% DM) of the feed samples. uCP = (9.95 +/-2.73)PA + (2.92 +/- 1.36)PB(1) + (7.24 +/- 0.86)PB(2) + (8.20 +/- 3.33)PB(3) + (17.67 +/- 3.79) PC + (63.26 +/- 18.02), r2 = 0.90, n = 30, p < 0.0001. It was suggested that the multiple regression relationship shown above could be used for the estimation of the uCP of feeds based on the CNCPS crude protein fractions PA, PB1, PB2, PB3 and PC of feeds for ruminants. 相似文献
3.
D G Fox C J Sniffen J D O'Connor J B Russell P J Van Soest 《Journal of animal science》1992,70(11):3578-3596
The Cornell Net Carbohydrate and Protein System (CNCPS) has equations for predicting nutrient requirements, feed intake, and feed utilization over wide variations in cattle (frame size, body condition, and stage of growth), feed carbohydrate and protein fractions and their digestion and passage rates, and environmental conditions. Independent data were used to validate the ability of the CNCPS to predict responses compared to National Research Council (NRC) systems. With DMI in steers, the CNCPS had a 12% lower standard error of the Y estimate (Sy.x) and three percentage units less bias than the NRC system. For DMI in heifers, both systems had a similar Sy.x but the NRC had four percentage units less bias. With lactating dairy cows' DMI, the CNCPS had a 12% lower Sy.x. Observed NEm requirement averaged 5% under NRC and 6% under CNCPS predicted values at temperatures above 9 degrees C but were 18% over NRC and 9% under CNCPS at temperatures under 9 degrees C. Energy retained was predicted with an R2 of .80 and .95 and a bias of 8 and 4% for the NRC and CNCPS, respectively. Protein retained was predicted with an R2 of .75 and .85 with a bias of 0 and -1% for NRC and CNCPS, respectively. Biases due to frame size, implant, or NEg were small. Body condition scores predicted body fat percentage in dairy cows with an R2 of .93 and a Sy.x of 2.35% body fat. The CNCPS predicted metabolizable protein allowable ADG with a bias of 1.6% with a Sy.x of .07 kg compared to values of -30% and .10 kg, respectively for the NRC system. 相似文献
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为准确评价不同来源的DDGS作为反刍动物饲料的营养价值,研究采用美国康奈尔大学净碳水化合物和净蛋白质体系(CNCPS)的原理和方法,测定和分析了8种不同来源的玉米干酒糟及其可溶物(DDGS)的营养价值及营养特性,并且把DDGS和当地的玉米、豆粕的营养价值进行了比较。经测定,8种DDGS常规营养成分(占干物质%)的平均数为:粗蛋白(28.28±2.56)%,粗脂肪(11.01±1.03)%,碳水化合物CHO(56.10±5.65)%,NDF(45.06±4.24)%,ADF(18.94±1.52)%,木质素(3.67±0.35)%。在蛋白组分中,PA、PB1、PB2、PB3和PC分别占粗蛋白的(5.67±0.27)%、(4.9±0.51)%、(22.89±2.39)%、(49.8±4.77)%和(16.68±2.61)%,其中,PA、PC的含量变化大,变异系数分别为8.8%和16.7%。在碳水化合物组分中,CA、CB1、CB2和CC分别占CHO的(25.74±0.82)%、(13.74±3.14)%、(44.76±4.49)%和(15.76±1.23)%。作为能量饲料和玉米相比,DDGS的载能物质主要是脂肪和可消化纤维,所估计的产奶净能低于玉米(6.56MJ/kg比7.73MJ/kg)。作为蛋白质饲料和豆粕相比,DDGS中主要的蛋白质组分是慢速降解蛋白(PB3),且能为小肠提供多于豆粕的过瘤胃蛋白(96.50g/kg比62.57g/kg)。上述结果表明,不同来源或不同生产工艺产生的DDGS营养价值差异较大,可溶性蛋白的含量和酸性洗涤不溶蛋白质含量的变化是引起DDGS营养价值变化的主要原因。因此,改善玉米DDGS的加工工艺,准确测定DDGS蛋白质组分和碳水化合物组分的含量是科学利用DDGS饲料产品的必要条件。 相似文献
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The objective of this study was to investigate rumen available soluble, insoluble and total protein (CP), estimated structural (SC) and non‐structural carbohydrate (starch: ST), degradation characteristic ratios and hourly effective degradation of six barley varieties during three consecutive growth years (2003, 2004, 2005). The magnitude of the differences was determined between the varieties and growth years. Measured degradation kinetics included soluble fraction (S), undegradable fraction (U), lag time (T0) and rate of degradation (Kd) of the insoluble but degradable fraction (D). Rumen available soluble, insoluble, and total N, SC and ST and the rumen degradation characteristic ratios were determined using the Tamminga rumen degradation ratio system. Characteristics of the hourly effective degradation between N and carbohydrate (CHO) among the six barley varieties for 3 years were also studied. The degradation ratios included were total rumen available N and carbohydrate ratio (FN/FCHO), rumen available soluble N and carbohydrate ratio (SN/SCHO), and rumen available insoluble N and carbohydrate ratio (EN/ECHO). Results show that both the barley variety and growth year had a significant effect on degradation kinetics (S, D, U, T0 and/or Kd). Differences in the ratio of FN/FCHO among varieties ranged from 16.6 to 19.0 g/kg (p < 0.01). There was no difference in SN/SCHO (p > 0.05) with an average of 4.9 g/kg. The difference in the EN/ECHO ratio tended to be significant among the varieties (p = 0.069) ranging from 18.4 to 21.3 g/kg. Differences in the hourly effective degradation between N and CHO were relatively small at shorter incubation times (2–4 h) However, as the length of rumen incubation increased (12–24 h), much larger differences in the rate of effective hourly degradation were observed. In conclusion, both barley variety and growth year had significant effects on rumen degradation kinetics. The mean FN/FCHO ratio of 17.2 (16.6–19.0) was observed for the six barley varieties in this experiment. All barley varieties exhibited a less optimal rumen fermentation ratio (17.2 < optimum: FN/FCHO = 25 to 33 g N per kg CHO). The large differences in the degradation kinetics, characteristics ratios and hourly effective degradation among barley varieties and growth years may help to explain some of the large variations that are seen in cattle performance. 相似文献
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本试验旨在应用康奈尔净碳水化合物-蛋白质体系(CNCPS)和NRC模型评价4种粮食加工副产物的营养价值。从东北地区4个不同牧场采集了玉米纤维饲料、大豆皮、甜菜粕和豆渣4种粮食加工副产物,测定其营养成分,应用CNCPS模型对蛋白质和碳水化合物组分进行剖分,并预测其潜在营养价值供给量,应用NRC模型估测可消化养分和能值。结果表明:1)中性洗涤纤维(NDF)的含量由高到低依次为大豆皮、甜菜粕、玉米纤维饲料和豆渣;非蛋白氮(NPN)的含量由高到低依次为玉米纤维饲料、豆渣、甜菜粕和大豆皮;甜菜粕的酸性洗涤不溶粗蛋白质(ADICP)含量最高,其余依次为大豆皮、豆渣和玉米纤维饲料,其中玉米纤维饲料和豆渣的ADICP含量差异不显著(P0.05)。2)非蛋白氮(PA,即NPN)含量由高到低依次为玉米纤维饲料、豆渣、甜菜粕和大豆皮;真蛋白质(PB)含量由高到低依次为大豆皮、甜菜粕、豆渣和玉米纤维饲料;不可降解氮(PC)的含量由高到低依次为豆渣、甜菜粕、大豆皮和玉米纤维饲料。3)可代谢蛋白质(MP)含量由高到低依次为豆渣、大豆皮、甜菜粕和玉米纤维饲料。4)玉米纤维饲料和豆渣的维持水平总可消化养分(TDNm)含量较高,二者差异不显著(P0.05);生产水平泌乳净能(NELP)值由高到低依次为豆渣、玉米纤维饲料、大豆皮和甜菜粕,其中玉米纤维饲料的NELP值与豆渣、大豆皮差异均不显著(P0.05);生产水平代谢能(MEP)值由高到低依次为豆渣、玉米纤维饲料、甜菜粕和大豆皮。由此可见,玉米纤维饲料和大豆皮可以作为奶牛的纤维源饲料;豆渣的过瘤胃蛋白质(RUP)、MP含量最高,可以作为奶牛的蛋白质源饲料。4种粮食加工副产物的能值由高到低依次为豆渣、玉米纤维饲料、大豆皮、甜菜粕。 相似文献
9.
辽宁绒山羊常用饲料营养价值评定 总被引：1，自引：0，他引：1
采集辽宁绒山羊常用饲料17种23个样品,应用康奈尔净碳水化合物-蛋白体系(CNCPS)提出的原理和方法对饲料营养价值进行评价。测定饲料原料常规营养成分以及非蛋白氮(NPN)、可溶性蛋白(SCP)、酸性洗涤不溶蛋白(ADFIP)、中性洗涤不溶蛋白(NDFIP)及酸性洗涤纤维(ADF)、中性洗涤纤维(NDF)、木质素(LIGNIN)和淀粉,并对饲料原料的蛋白质和碳水化合物进行分类分析。结果表明:粗饲料可溶性蛋白质主要是NPN,真蛋白含量少,3种蛋白质饲料可溶蛋白主要是真蛋白,NPN含量少;所采集灌木类饲料纤维含量尤其是慢速降解细胞壁成分含量低,可快速降解糖类和可利用蛋白质含量高,质量优于秸秆和干草等其他粗饲料;棉粕的不可消化纤维和不可消化蛋白质含量高,可消化利用性较差。豆皮的蛋白质含量较低,主要是慢速降解纤维成分占绝大多数。 相似文献
10.
The Cornell Net Carbohydrate and Protein System (CNCPS) prediction of fiber digestion and microbial mass production from ruminally degraded carbohydrate has been adjusted to accommodate a ruminal N deficiency. The steps for the adjustment are as follows: 1) the ruminal available peptide and ammonia pools are used to determine the N allowable microbial growth; 2) this value is subtracted from the energy allowable microbial growth to obtain the reduction in microbial mass; 3) this mass reduction is allocated between pools of bacteria digesting fiber (FC) and nonfiber (NFC) carbohydrate according to their original proportions in the energy allowable microbial growth; 4) the reduction in fermented FC is computed as the FC bacterial mass reduction divided by its yield (g bacteria/g FC digested); and 5) this reduction is added to the FC fraction escaping the rumen. Five published studies included information that allowed us to evaluate the response of animals to added dietary N. These evaluations compared observed and CNCPS-predicted ADG with and without this adjustment. The adjustment decreased the CNCPS overprediction of ADG from 19.2 to 4.7%, mean bias declined from .16 to .04 kg/d, and the r2 of the regression between observed and metabolizable energy (ME) or metabolizable protein allowable ADG was increased from .83 to .88 with the adjustment. When the observed dry matter intake was regressed against CNCPS-predicted DMI with an adjustment for reduction in cell wall digestibility, the r2 was increased from .77 to .88. These results indicated the adjustment for ruminal nitrogen deficiency increased the accuracy of the CNCPS model in evaluating diets of growing animals when ruminally degraded N is deficient. 相似文献
11.
为了预测奶牛常用饲料中可利用氨基酸(u AA)的含量,本试验采集了21个奶牛饲料原料样品,测定了饲料样品的粗蛋白质(CP)、粗脂肪(EE)、粗灰分(ash)、中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)、可溶性粗蛋白质(SCP)、非蛋白氮(NPN)、中性洗涤剂不溶粗蛋白质(NDIP)、酸性洗涤剂不溶粗蛋白质(ADIP)含量,并根据康奈尔净碳水化合物-蛋白质体系(CNCPS)对饲料含氮化合物组分的划分方法,计算出饲料样品的含氮化合物组分非蛋白氮(PA)、快速降解真蛋白质(PB1)、中速降解真蛋白质(PB2)、慢速降解真蛋白质(PB3)和不可利用蛋白质(PC)的含量,测定了饲料的氨基酸含量,同时利用饲料氨基酸含量与u AA含量之间的关系估测出饲料的u AA含量。结果表明,奶牛常用饲料的CNCPS含氮化合物组分(PA、PB1、PB2、PB3、PC)含量(%DM)与u AA、可利用蛋氨酸(utilizable methionine,u Met)、可利用赖氨酸(utilizable lysine,u Lys)、可利用亮氨酸(utilizable leucine,u Leu)含量(%DM)存在显著的相关关系,回归方程如下:u AA=0.171PA+0.134PB1+0.364PB2+0.370PB3+0.148PC+7.785,R2=0.99,P0.01;u M et=0.019PA-0.031PB1+0.024PB2+0.078PB3-0.004PC-0.071,R2=0.93,P0.01;u Lys=-0.045PA-0.020PB1+0.072PB2+0.038PB3-0.011PC+0.780,R2=0.92,P0.01;u Leu=0.071PA+0.033PB1+0.093PB2+0.189PB3+0.003PC+0.006,R2=0.94,P0.01。结果显示,根据CNCPS含氮化合物组分和本试验所建立的方程,可以准确地预测奶牛饲料的u AA、u M et、u Lys和u Leu含量。 相似文献
12.
为了评定不同生育期虉草的营养价值,分析体外产气法和CNCPS法两种营养评价方法的相关性。采用体外产气法测定抽穗期、开花期、灌浆期、乳熟期4个生育期虉草的体外发酵产气量、发酵参数(a、b、c)、DM消化率、NDF和ADF降解率,用康奈尔净碳水化合物和蛋白质体系(cornell net carbohydrate and protein system,CNCPS)分析方法测定相应组分,评价其营养价值,并比较研究两种方法评价结果的相关性。结果表明,体外发酵至72 h结束,累计总产气量和产气参数a以开花期最高(122.68 和4.46 mL),显著高于各组(P<0.05),且从抽穗期、灌浆期、乳熟期有降低的趋势;抽穗期和开花期的DM消化率、NDF和ADF降解率分别显著高于灌浆期和乳熟期(P<0.05)。随着虉草生育期的延长,CP和SOLP呈递减趋势,即抽穗期和开花期显著高于灌浆期和乳熟期(P<0.05);NDF、ADF和ADL呈递增趋势,但NDFIP、ADFIP呈递减趋势。灌浆期和乳熟期的CHO含量显著高于抽穗期和开花期(P<0.05),而CA和CNSC含量则相反,且CC含量同样以灌浆期与乳熟期较高;蛋白质组分中,PA与CA及CC与PC组分呈现同样的趋势。虉草CNSC、CA、CB1、CB2、PA、PB3组分含量与不同时间点产气量呈显著或极显著的相关性(P<0.05或P<0.01)。因此,开花期虉草营养价值最高,其次为抽穗期、灌浆期和乳熟期,产气法和CNCPS评价牧草具有相关性,用体外产气量估测牧草CNCPS组分是可行的。 相似文献
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康奈尔净碳水化合物—蛋白质体系在中国的研究进展及发展趋势 总被引：2，自引：2，他引：0
作者从康奈尔净碳水化合物—蛋白质体系(Cornell net carbohydrate and protein system, CNCPS)饲料组分评定、基础数据库建设、模型验证及模型改进等方面综述了CNCPS在中国的研究进展,并从建设标准饲料组分剖分方法、扩大基础数据库、校正品种因子、改进瘤胃和小肠模型、开发计算机软件等方面提出了CNCPS在中国的发展趋势。随着CNCPS在中国的发展及转化,它将对中国畜牧业的发展起着重要推动作用。 相似文献
14.
W K Coblentz J O Fritz W H Fick R C Cochran J E Shirley J E Turner 《Journal of animal science》1999,77(10):2803-2809
In situ digestion kinetics of neutral detergent insoluble nitrogen (NDIN) from alfalfa (Medicago sativa L.) harvested at one-tenth bloom and eastern gamagrass (Tripsacum dactyloides L.) harvested at the boot (GGB), anthesis (GGA), and physiological maturity (GGM) stages of growth were determined with nonlinear regression techniques. Whole-plant tissue and associated leaf and stem fractions were incubated in the ventral rumen simultaneously. On a wholeplant basis, potential extents of degradation were particularly high (> or =904 g/kg NDIN) for GGB and GGA, relative to those of GGM and alfalfa (772 and 658 g/kg NDIN, respectively). For all plant parts, degradation rates of NDIN were faster (P<.05) for alfalfa than for all gamagrass forages. Degradation rate of NDIN did not differ (P>.05) across maturities for any gamagrass tissue type. These results indicate 1) that phenological development and lignification do not limit the rate of NDIN degradation in gamagrass forages but do markedly limit the potential extent of NDIN availability and 2) that most of the NDIN in these forages is potentially available in the rumen and can contribute to the ruminal N supply. Our secondary objective was to compare estimates of N escaping ruminal degradation that were determined on the basis of NDIN degradation kinetics (NDIN method) with those determined traditionally, on the basis of total residual N. The NDIN method mathematically eliminates all neutral detergent soluble N from consideration as part of the pool of dietary N potentially escaping the rumen intact. Estimates of rumen escape nitrogen determined on the basis of degradation rates of NDIN were consistently less than corresponding estimates that were determined on the basis of total residual N. When ruminal escape N that was determined with the NDIN method was regressed on corresponding estimates with the total residual N method, the slopes of the regression lines were .53 and .66 for assumed passage rates of .02 and .06 h(-1), respectively. For the forages evaluated in this study, these results indicate that neutral detergent soluble N may make important contributions to the pool of N escaping ruminal degradation. 相似文献
15.
本文旨在研究添加可溶性淀粉对降解后的白酒糟体外发酵特性的影响,并确定影响发酵的最佳结构性碳水化合物(SC)与非结构性碳水化合物(NSC)的比例.采用黄孢原毛平革菌发酵白酒糟20 d,以降解其木质素含量.在体外发酵各组中添加可溶性淀粉使SC/NSC比分别为1.66、2.06、2.46、2.86、3.26和3.66.每组设5个重复.结果表明,通过黄孢原毛平革菌发酵,白酒糟中酸性洗涤木质素的含量降低了16.4%(P＜0.01),而粗蛋白质含量提高了6.04%(P＜0.01).在体外发酵试验中,随着可溶性淀粉添加量的增加,累计产气量显著增加(P＜0.01).增加可溶性淀粉添加量改变SC/NSC比可显著影响微生物蛋白(MCP)、总挥发性脂肪酸(TVFA)和氨氮(NH3-N)浓度(P＜0.01).通过SC/NSC比(x)与MCP(y)的回归分析(y=-0.826x2+3.947x+1.189)得出,体外发酵最佳SC/NSC比为2.39.添加可溶性淀粉提高了丙酸在TVFA中的比例(P＜0.05),而降低了乙酸与丙酸比例(P＜0.05).由结果可知,添加可溶性淀粉可提高降解后白酒糟的消化率,并得出体外发酵最佳SC/NSC比为2.39. 相似文献
16.
用CNCPS评定反刍动物几种常用精料营养价值的研究 总被引：3，自引：0，他引：3
[目的]为了验证CNCPS评定方法的可靠性.[方法]分别从黑龙江省的大庆、哈尔滨、双鸭山、佳木斯、牡丹江、集贤和五常等地采集反刍动物常用精饲料样品19种, 应用康奈尔净碳水化合物-蛋白质体系(CNCPS)提出的碳水化合物和蛋白质分类方法, 分别测定了饲料的粗蛋白质(CP)、非蛋白氮(NPN)、可溶性粗蛋白(SCP)、酸性洗涤不溶粗蛋白(ADFIP)和中性洗涤不溶粗蛋白(NDFIP)、酸性洗涤纤维(ADF)、中性洗涤纤维(NDF)、木质素和淀粉.并根据CNCPS提出的计算方法计算了饲料粗蛋白质中的非蛋白氮(PA)、快速降解蛋白质(PB1)、结合蛋白质(PC)、中度降解蛋白质(PB2)、慢速降解蛋白质(PB3)和碳水化合物中的不可利用纤维(CC)、可利用纤维(CB2)、果胶(CB1)和糖类(CA).[结果]通过CNCPS饲料评定技术可对反刍动物常用精饲料营养价值分析评定.[结论]说明CNCPS可广泛用于对刍动物饲料营养价值的评定. 相似文献
17.
常用粗饲料营养成分和饲用价值分析 总被引：2，自引：0，他引：2
通过常规化学分析法和康奈尔净碳水化合物-蛋白质体系(CNCPS)评定不同粗饲料的营养成分并比较其组成差异,结合粗饲料品质评定预测公式评定其饲用价值。结果表明,1)黑麦草、甘薯蔓与牛鞭草的粗蛋白质(CP)、粗脂肪(EE)、可溶性粗蛋白质(SCP)和非蛋白氮(NPN)含量显著高于玉米秸秆和稻草,中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)含量显著低于玉米秸秆和稻草。 2)黑麦草和甘薯蔓的糖类(CA)、快速降解真蛋白(PB1)含量显著高于其他粗饲料,甘薯蔓、黑麦草和牛鞭草淀粉和果胶(CB1)、非结构碳水化合物(NSC)和慢速降解真蛋白(PB3)显著高于稻草和玉米秸秆。稻草的可利用纤维(CB2)含量显著高于其他粗饲料,玉米秸秆的碳水化合物(CHO)、不可利用碳水化合物(CC)和中速降解蛋白质部分(PB2)含量显著高于其他粗饲料。3)不同粗饲料氨基酸(AA)组成差异大,提供限制性氨基酸的潜力不同,黑麦草的总氨基酸(TAA)、必需氨基酸(EAA)和限制性氨基酸(LAA)的含量显著高于其他粗饲料,玉米秸秆和稻草最低。4)黑麦草的可消化干物质量(DDM)和粗饲料相对值(RFV)均显著高于其他粗饲料,甘薯蔓的干物质随意采食(DMI)和RFV显著高于牛鞭草,玉米秸秆和稻草的DMI、DDM和RFV均为最低,且两者差异不显著。因此,黑麦草的营养价值最高,其次为牛鞭草和甘薯蔓,玉米秸秆和稻草最低。 相似文献
18.
In situ neutral detergent insoluble nitrogen as a method for measuring forage protein degradability.
A method of estimating the undegraded intake protein (UIP) concentration of forages was developed and validated with a series of in situ experiments. The hypothesis was that UIP calculated from in situ neutral detergent insoluble N (NDIN) is equal to total in situ N minus the microbial N that is estimated from purines (MN). The in situ disappearance rates of total in situ N (TN), MN, and NDIN were measured for six hay samples and two range masticate samples. Hypothetical rates of passage (2 or 5%/h) were used to calculate UIP (% of DM) for each N pool. Estimates of UIP from TN were higher (P = .0001) than those from either MN or NDIN, and MN estimates of UIP were similar (P = .48) to NDIN estimates. A low-N fiber source (solka floc) was incubated in situ for 8 h. Analysis of the residue detected purines before, but not after, neutral detergent extraction. Several in situ incubation (i.e., Dacron bag size and number of Dacron bags in a mesh bag) and neutral detergent extraction conditions were tested. None of the factors tested affected in situ NDIN disappearance (P > .05). The hypothesis that NDIN is completely digestible in the rumen was tested. Estimates of the extent of NDIN digestion were made using 96-h in situ incubations, and UIP was recalculated for the test samples. Mean in situ UIP concentration decreased upon recalculation (P = .05). In situ NDIN provides estimates of forage UIP that are equal to estimates from MN. Forage UIP estimates are less when extent of N degradation is estimated and included in the calculation. 相似文献
19.
试验旨在运用康奈尔净碳水化合物—蛋白质体系(CNCPS)和NRC模型分析比较发酵湿玉米纤维饲料(FWCGF)、湿玉米纤维饲料(WCGF)、苜蓿和青贮玉米(CS)的营养价值,预测FWCGF替代或部分替代反刍动物常用粗饲料的可行性。从黑龙江省不同牧场采集饲料样品,测出4种原料的常规营养成分,然后利用CNCPS模型剖分4种原料的蛋白质和碳水化合物组分,再通过NRC模型估测待测饲料的可消化养分和能值。结果表明:FWCGF的粗蛋白质含量高于其他3种饲料(P<0.05),FWCGF的酸性洗涤纤维含量最低(P<0.05);FWCGF的真蛋白质最高(P<0.05),FWCGF的瘤胃可降解蛋白质、可代谢蛋白质、总可消化养分和净能最高(P<0.05)。由此可见,相对于其他原料,FWCGF的可利用蛋白和纤维含量丰富,是奶牛日粮中纤维类、蛋白类粗饲料的有效替代品。 相似文献
20.
A 2(3) factorial arrangement of treatments was used to study main effects and interactions between particle size of prairie hay (chopped vs ground), two levels of feed intake (60 and 90% of ad libitum) and ruminal degradability of protein sources [dry corn gluten feed (DCGF) vs dry distillers grains (DDG)] on ruminal and total tract digestion in eight ruminal- and duodenal-cannulated steers. Steers were fed every 2 h to approach steady-state feeding conditions. Steers fed ground hay diets digested higher (P less than .05) percentages of total digestible organic matter (OM) and neutral detergent fiber (NDF) in the rumen and had lower (P less than .05) nonammonia-nonbacterial N (NANBN) flows to the duodenum than did those fed chopped hay, probably because greater surface area of ground hay allowed more extensive ruminal fermentation. Protein source X intake interactions were noted for ruminal OM and NDF digestion when expressed as percentages of total digestion. At low intakes, steers fed DCGF had higher (P less than .05) percentages of total digestible OM and NDF disappearing in the rumen than did those fed DDG. Steers fed DCGF had lower total N, NANBN and total amino acid (AA) flows at the duodenum than did those fed DDG, indicating that less DCGF protein escaped ruminal degradation. Steers fed DDG had greater (P less than .05) total tract NDF digestion, suggesting that escape protein from DDG may stimulate hindgut fermentation and thereby affect site and extent of nutrient digestion. Regression analysis indicated that extent of ruminal fermentation and efficiency of microbial growth in vivo are associated with ruminal rates of passage within individual animals. When steers were fed at high-intake levels (1.6% of body weight), ruminal dilution rates were not increased (P less than .05) due to forage particle size or level of intake treatments, accounting, in part, for the lack of expected treatment differences in efficiency of bacterial growth and duodenal N flow, and for the low number of interactions between main effects. 相似文献