肉牛常见饲料干物质和蛋白质瘤胃降解特性和小肠消化率研究

[方法]选用装有瘤胃瘘管和小肠瘘管的肉牛作为试验动物,尼龙袋法测定肉牛常见饲料干物质(DM)和粗蛋白(CP)的瘤胃降解特性和小肠消化率。[结果]结果表明,DM瘤胃有效降解率由高到低为玉米粉、麦麸、苜蓿干草、豆粕、菜籽粕、玉米青贮、醋糟、白酒糟;CP瘤胃有效降解率由高到低为苜蓿干草、麦麸、豆粕、醋糟、玉米粉、玉米青贮、菜籽粕、白酒糟;DM小肠消化率由高到低为豆粕、菜籽粕、玉米粉、白酒糟、醋糟、麦麸、苜蓿干草、玉米青贮;CP小肠消化率由高到低为豆粕、菜籽粕、玉米粉、苜蓿干草、麦麸、白酒糟、玉米青贮、醋糟。[结论]试验表明,不同饲料瘤胃降解特性不同,为小肠提供过瘤胃可消化蛋白的能力不同,且饲料的DM小肠消化率小于CP小肠消化率。     

Comparing relative feed value with degradation parameters of grass and legume forages

Relative feed value (RFV) was evaluated relative to in situ degradation parameters of grass and legume forages. Early-cut alfalfa (n = 20), late-cut alfalfa (n = 26), cool-season grass (n = 11), warm-season grass (n = 4), and grass-legume (n = 20) samples were collected from duplicate hay bales submitted to the 2002 and 2003 Missouri State Fair Hay Contests. Subsamples were incubated in the rumen of 2 lactating Holstein cows for 0, 6 or 8, 12, 24, and 48 h to determine in situ degradation of DM, ADF, NDF, CP, and hemicellulose over time. Degradation data were fit to a variety of candidate models to estimate degradation parameters. Correlation coefficients between degradation parameter estimates [sorted according to forage (early-cut alfalfa, late-cut alfalfa, grass, or grass-legume)] and RFV were determined. For further comparison, correlations between NDF degradation parameter estimates and digestible DMI were determined with data from a previous study. Degradation data were best fit to a single, gamma 2-distributed pool model without a lag phase. Relative feed value was significantly correlated (P < 0.05) with potentially digestible DM and CP for early-cut alfalfa, potentially digestible DM for late-cut alfalfa, and potentially digestible DM, NDF, and hemicellulose for grass-legume. The percentage of significant correlations (10.7%) across the entire data set was low and no correlations were significant for grass. Relative feed value did not account for the variation in degradation parameters, especially for grasses. A further correlation analysis, which compared digestible DMI with degradation parameter estimates reported from another data set, revealed that digestible DMI and degradation parameter estimates were related for grass but not for alfalfa forages. These results suggest that RFV is limited by its failure to include degradation parameters.     

Calculation of utilizable crude protein at the duodenum of cattle by two different approaches.

The duodenal flow of utilizable crude protein (crude protein minus endogenous protein) in cows was estimated using dietary parameters, first by multiple regression and secondly by the addition of microbial protein and undegraded feed protein. These estimates were compared with 327 results from experiments conducted with fistulated cows in Braunschweig-V?lkenrode and Rostock-Dummerstorf. The regressions and the measurements for microbial protein synthesis as well as feed protein degradation and organic matter fermentation in the rumen were based on the same experimental data set. The prediction of utilizable crude protein (uCP) at the duodenum by regression with digested organic matter (kg DOM) and undegraded feed protein (g UDP) as predicting variables, was more accurate than the value given by microbial protein synthesis and rumen protein degradability. The regression model [g uCP = [188.5-(116.5 (UDP/CP))] DOM + 1.03 UDP] had the highest coefficient of determination (r2 = 0.91) and the lowest coefficient of variation (cv = 8.6); indicating the model's superiority over the other method of estimation.     

奶牛常用蛋白质饲料和粗饲料的瘤胃降解特性研究

本研究旨在评定不同蛋白质饲料(豆粕、双低菜籽粕、膨化大豆、玉米蛋白粉、棉籽粕)和粗饲料(苜蓿干草、全株玉米青贮、燕麦草、苜蓿青贮、羊草)的营养价值,并研究其奶牛瘤胃降解特性.选择5头安装永久性瘤胃瘘管的健康荷斯坦牛,采用尼龙袋评定法评定饲料瘤胃有效降解率和动态降解率.结果表明:1)各蛋白质饲料干物质(DM)含量差异不显...     

Studies on the evaluation of feed protein for ruminants. 1. Passage of nitrogen fractions to the duodenum of dairy cows fed different protein and carbohydrate sources

The duodenal passages of non-ammonia nitrogen (NAN), amino acid N (AA-N) and microbial N (MN) were measured in seven duodenal fistulated dairy cows (6130 kg FCM/305 d) during lactation receiving 30 different rations similar to those used in dairy practice. The rations consisted of roughage (protein-rich silages, hay) and concentrate mixture (corn, barley, oat) in a ratio of 60:40 on a DM basis or roughage/concentrate mixture/fodder beets in the proportions 60:20:20 or 60:0:40 respectively. N supplements consisted of soya bean meal and peas meal (untreated or treated with formaldehyde in each case), rapeseed meal, fish meal and urea. DM intake varied between 9.6 and 19.1 kg/d, the crude fibre content between 166 and 270 g/kg DM, the crude protein (CP) content between 111 and 184 g/kg DM, the AA content (N basis) of the CP between 51 and 82%, the unfermentable CP content of the CP between 23 and 49% and the organic matter digestibility between 70 and 79%. The duodenal passage of NAN was 24.2 +/- 2.7 g/kg DM intake, 34.9 +/- 4.1 g/kg apparently digestible organic matter (in total tract, DOM), 43.3 +/- 5.5 g/kg apparently digestible carbohydrates or 4.2 +/- 0.5 g/MJ net energy fat, (y +/- s, n = 90). The value measured for AA-N was 16.8 +/- 2.9 g/kg DM intake, and that for RNA-labelled microbial CP was 146 +/- 26 g/kg DOM. NAN passage (g/kg DM intake) correlated more closely with the duodenal digesta flow rate (DFR) (kg digesta/kg DM intake) as an intrinsic animal factor (r = 0.78) and with the rumen content dilution rate (RDR) (passage of microbial-free organic matter at duodenum/kg BW0.75.h) as a ration dependent factor (r = 0.64) than with the UDP fraction (% of ration CP) (r = 0.50) or other ration parameters. It was concluded that the specific effect of protein concentrates in mixed rations on duodenal NAN yields in lactating dairy cows is lower than hitherto assumed. The duodenal NAN yield of a single feedstuff or ration (g/kg DM) in cows is dependent on animal and feeding factors. The DFR could represents a suitable target for breeding activities.     

Development of an in vitro incubation technique for the estimation of the utilizable crude protein (uCP) in feeds for cattle.

An in vitro incubation technique based on the first stage of the in vitro digestion technique published by Tilley and Terry (1963) was developed to estimate the utilizable crude protein (uCP) of single feeds and feed mixtures as non ammonia-N after 24 h of incubation. The results of 25 feed samples showed that there was a significant relationship between the uCP values calculated by regression based on in vivo data sets (Y, CP [g.kg-1 DM]) and those measured by the in vitro incubation technique (X, CP [g.kg-1 DM], 24 h incubation): y = 0.85x + 18.0, r2 = 0.84, P < or = 0.001. It was concluded that it can be possible to determine the uCP value of single feeds or feed mixtures by this in vitro incubation technique and to estimate the uCP value of feeds by this regression equation.     

Effective rumen degradation of dry matter, crude protein and neutral detergent fibre in forage determined by near infrared reflectance spectroscopy

The objective of the present study was to examine if near infrared reflectance spectroscopy (NIRS) could be used to predict degradation parameters and effective degradation from scans of original forage samples. Degradability of dry matter (DM), crude protein (CP) and neutral detergent fibre (NDF) of 61 samples of perennial ryegrass (Lolium perenne L.) and orchardgrass (Dactylis glomerata L.) was tested by using the in situ technique. The grass samples were harvested at three different stages, early vegetative growth, early reproductive growth and late reproductive growth. Degradability was described in terms of immediately rumen soluble fraction (a fraction, for DM and CP only as NDF does not contain a soluble fraction), the degradable but not soluble faction (b fraction) and the rate of degradation of the b fraction (c value). Overall effective degradability of DM, CP and NDF was also calculated. Near infrared reflectance spectroscopy was examined for its ability to predict degradation parameters and to make a direct prediction of effective degradation from scans of the original samples of perennial ryegrass and orchardgrass. Prediction of effective degradation of the different feed fractions showed different accuracy. The coefficients of determination (R(2)) from regressions of predicted vs. measured effective degradation, using a cross-validation method, were 0.92 for DM, 0.78 for CP and 0.61 for NDF. The attempt to predict the degradation parameters (a, b and c) by NIRS was less successful as the coefficients of determination for the degradation parameters were low. Concentrations of CP and NDF in the original samples were predicted by using NIRS and the validated R(2) value was 0.98 for CP and 0.92 for NDF. It is concluded that using NIRS predictions from scans of original samples is a promising method to obtain values for the effective degradation of DM, CP and NDF in ruminant feeds, but that larger calibration sets are necessary for obtaining improved accuracy.     

Relationship between the in vitro-estimated utilizable crude protein and the Cornell Net Carbohydrate and Protein System crude protein fractions in feeds for ruminants

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.     

6种饲料原料瘤胃降解特性和瘤胃非降解蛋白质的小肠消化率

本试验旨在研究新疆地区玉米青贮、棉籽壳、苜蓿草粉、苜蓿干草、葡萄籽粕、蕃茄酱渣6种奶牛饲料原料的瘤胃降解特性和瘤胃非降解蛋白质(RUP)的小肠消化率(Idg)。选用3头装有永久性瘤胃瘘管的泌乳荷斯坦奶牛,采用尼龙袋法和改进三步体外法测定饲料原料的干物质(DM)、粗蛋白质(CP)、中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)的瘤胃降解特性以及RUP的Idg和小肠可消化粗蛋白质(IDCP)含量。结果表明:1)苜蓿草粉和玉米青贮的DM有效降解率最高,显著高于次之的苜蓿干草、番茄酱渣(P0.05),葡萄籽粕、棉籽壳最低,显著低于其他原料(P0.05);CP有效降解率为番茄酱渣苜蓿草粉玉米青贮苜蓿干草棉籽壳葡萄籽粕,各原料间差异显著(P0.05);NDF有效降解率为玉米青贮苜蓿草粉棉籽壳苜蓿干草番茄酱渣葡萄籽粕,各组饲料原料间差异显著(P0.05);ADF有效降解率为玉米青贮棉籽壳苜蓿干草番茄酱渣苜蓿草粉葡萄籽粕,各组饲料原料间差异显著(P0.05)。2)苜蓿草粉RUP的Idg和IDCP含量最高,Idg显著高于依次降低的苜蓿干草、玉米青贮、番茄酱渣、葡萄籽粕、棉籽壳(P0.05),IDCP含量与苜蓿干草差异不显著(P0.05),显著高于依次降低的玉米青贮、番茄酱渣、葡萄籽粕、棉籽壳(P0.05)。综上所述,不同饲料原料具有不同的瘤胃降解特性,进入小肠IDCP的含量也不同。玉米青贮的DM、NDF和ADF在瘤胃的有效降解率较高,苜蓿草粉RUP的Idg较高,苜蓿草粉和苜蓿干草的IDCP含量较高。     

Evaluation of the fermentation dynamics of soluble crude protein from three protein sources in continuous culture fermenters

Eight dual-flow continuous culture fermenters (1.03 +/- 0.05 L) were used to assess differences in microbial degradation of the soluble CP fraction of canola meal (CMSCP), soybean meal (SBMSCP), and fish meal (FMSCP) using a completely randomized design with two 9-d experimental periods and a solution of tryptone as a control treatment (control). All fermenters received the same basal diet (58% ground corn, 40% canary grass hay, 0.4% vitamin-mineral premix, 1% CaCO(3), 0.6% salt on a DM basis) in 8 equal portions daily. During sampling on the last 3 d of each period, 90-mL doses containing soluble CP were infused into the fermenters 30 min after the beginning of the first and last feedings of the day. The total amount of soluble CP supplied by the infusions of FMSCP, CMSCP, and SBMSCP was 3.2 g/d, representing 24% of the daily dietary CP intake. Infusion of FMSCP resulted in the greatest (P < 0.05) NH(3)-N concentration (4.6 +/- 0.40 mg/dL) compared with the other treatments (0.5 +/- 0.40 mg/dL). Microbial N flow (g/d) from the fermenters was also greatest (P < 0.05) with FMSCP (1.42 +/- 0.062) compared with the other soluble CP fractions (1.08 +/- 0.062). The efficiency of microbial protein synthesis tended to be lowest with the control diet, and the efficiency of N utilization was lowest with FMSCP treatment. These results indicate that N was limiting microbial growth in the control diet, and there was more rumen-available N with the FMSCP diet compared with the other dietary treatments. The extent of degradation of the soluble CP fraction from fish meal, soybean meal, and canola meal was determined to be 99, 30, and 37% of soluble CP, respectively. These results indicate that the soluble CP fraction is not 100% degraded in all feeds and that assuming a high degradation extent of the soluble CP fraction from soybean meal and canola meal may result in an underestimation of the supply of undegradable protein from these protein sources.     

不同处理方式的苜蓿草对犊牛生长性能、瘤胃发酵及微生物蛋白合成的影响

文章旨在评估苜蓿草的不同处理方式及饲料形式对犊牛生长性能、瘤胃发酵及微生物蛋白合成的影响.试验将60头均重为40.01 kg的刚出生犊牛随机分为4组,每组5个重复,每个重复3头牛.试验日粮采用多因素方差设计,2种苜蓿草处理方式(切碎和制粒)和2种饲料形式(粉料和颗粒料).T1组为切碎苜蓿草+粉料,T2组为制粒苜蓿草+粉...     

Duodenal bacterial and nonbacterial protein supply in steers fed forage and grain diets

Four beef steers (avg wt 300 kg) fitted with duodenal re-entrant cannulae were used to study the effect of dietary concentrate to forage ratio on bacterial and nonbacterial N flow in the duodenum. According to a change-over design, the steers were designated to receive an all forage (83% alfalfa hay and 17% wheat straw) and an 80% sorghum grain diet. Lignin (ADL) and chromium oxide (Cr2O3) ratio techniques were compared with automated total collection (ATC) of digesta for quantitating duodenal protein flow and efficiency of bacterial N yield in the rumen. Estimates of bacterial protein synthesis and ruminal escape of feed protein based on Cr2O3 and lignin tended to be higher by 8 to 16% than those obtained by ATC. Efficiency of ruminal bacterial protein yield estimated by these two markers tended to be greater than that based on ATC (16 vs 12 g of bacterial protein/100 g ruminal true digestion of dry matter corrected for bacterial cell synthesis). Efficiency values did not differ between diets. Crude protein flow into the duodenum was about 33% greater (P less than .01) for the grain than the forage diet, although protein intake was about 10% less on the grain diet. Duodenal bacterial protein, rather than feed protein escaping ruminal degradation, accounted for most of this difference. Average duodenal flow of N, expressed as g/Mcal metabolizable energy (ME) intake, was 11.9 for the forage diet and 10.3 for the grain diet.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative analysis of ensiling characteristics and protein degradation of alfalfa silage prepared with corn or sweet sorghum in semiarid region of Inner Mongolia

This study was conducted to evaluate silage fermentation and protein degradation of alfalfa prepared with corn or sweet sorghum (SS) at different mixing ratios. The chemical composition, ensiling characteristics, and protein degradation of alfalfa prepared with and without corn or SS at mixing ratios of 7:3, 1:1, and 3:7 on a fresh matter (FM) basis were studied. The alfalfa had the highest crude protein (CP) content and lactate buffering capacity (LBC), but lower water‐soluble carbohydrate (WSC) content than corn and SS. After 60 days of ensiling, the corn and SS silages had good quality, with lower pH and ammonia‐N content, and higher dry matter (DM) content than the alfalfa silages. In the alfalfa and corn mixture silages, the DM contents linearly increased with an increase in the proportion of corn, while the pH, non‐protein N (NPN), ammonia‐N, and peptide‐N contents linearly decreased. In the alfalfa and SS mixture silages, the DM and NPN contents linearly increased with an increase in the proportion of SS, while the pH, lactic acid, and ammonia‐N contents linearly decreased. This study suggests that alfalfa silage prepared with corn has more positive effect on fermentation quality and inhibiting protein degradation than addition of SS.     

Effects of Fusarium toxin-contaminated wheat grain on nutrient turnover, microbial protein synthesis and metabolism of deoxynivalenol and zearalenone in the rumen of dairy cows

The aim of the present study was to examine the effects of feeding Fusarium toxin-contaminated wheat to dairy cows on nutrient utilization in the rumen and on duodenal flow of deoxynivalenol (DON), zearalenone (ZON) and their metabolites. Six dairy cows fitted with a large rumen cannula and a simple T-shaped cannula at the proximal duodenum was used in two experiments. The experiments included a control period in which the uncontaminated control wheat was fed and a period in which the control wheat was replaced by the Fusarium toxin-contaminated wheat (8.05 and 7.15 mg DON/kg and 0.26 and 0.1 mg ZON/kg in Expts 1 and 2 respectively). The wheat portion of the daily ration amounted to 50% on a dry matter (DM) basis and rations were completed with hay or grass silage. Five of the six cows were non-lactating and the total daily DM-intake ranged between 4 and 12 kg. The pH-values and the concentration of volatile fatty acids in ruminal fluid were not significantly influenced by feeding the contaminated wheat. In contrast, the postprandial ammonia concentration was consistently higher when the mycotoxin-contaminated wheat was fed. Moreover, the flow of microbial protein and utilizable protein at the duodenum were reduced at the same time. The concentrations of DON and ZON and of their metabolites in freeze-dried duodenal digesta were either not detectable or negligible during the control periods whereas distinct concentrations were measured during the periods where the contaminated wheat was fed. DON was nearly completely metabolized to de-epoxy-DON and the flow at the duodenum ranged between 4% and 28% of DON-intake. The ZON metabolites alpha-zearalenol (ZOL) and beta-ZOL were recovered at the duodenum beside the parent toxin ZON. Their recovery as a percentage of ZON-intake ranged between 43% and 132%. In conclusion, feeding of Fusarium toxin-contaminated wheat altered the ruminal protein utilization. The question of whether this effect was a result of the mycotoxin being present in the rumen or of Fusarium growth-related structural (cell wall) changes of the wheat grain needs to be clarified. The low recovery of DON at the duodenum would indicate either a nearly complete degradation of the molecule in the rumen or an absorption by the mucosa of the rumen, whereas the higher ZON recovery would suggest a lower degradation of the parent toxin in the rumen and/or recovery of some bile-originating entero-hepatic cycling ZON/metabolites.     

Ruminal protein metabolism and intestinal amino acid utilization as affected by dietary protein and carbohydrate sources in sheep.

Eight wether lambs fitted with ruminal, duodenal, and ileal cannulas were used in a replicated 4 x 4 Latin square design to study the effects of carbohydrate and protein sources on ruminal protein metabolism and carbohydrate fermentation and intestinal amino acid (AA) absorption. Treatments were arranged as a 2 x 2 factorial. Carbohydrate sources were corn and barley; protein sources were soybean meal (SBM) and fish meal (FM). Diets contained 15.5% CP, of which 40% was supplied by SBM or FM. Corn or barley provided 39% of dietary DM that contained equal amounts of grass hay and wheat straw. Fish meal diets produced a lower (P less than .05) ruminal NH3 concentration and resulted in less CP degradation and bacterial protein flow to the duodenum than did SBM diets. Replacing SBM with FM increased (P less than .05) ruminal digestion of all fiber fractions. In addition, cellulose and hemicellulose digestibilities in the rumen tended to increase (P greater than .05) when barley replaced corn in the FM diets. Carbohydrate x protein interactions (P less than .05) were observed for OM digestion in the rumen and AA absorption in the small intestine (percentage of AA entering); these interactions were highest for the barley-FM diet. These results suggest that feeding FM with barley, which is high in both degradable carbohydrate and protein, might benefit ruminants more than feeding FM with corn, which is high in degradable carbohydrate but relatively low in degradable protein.     

不同牧草在黄牛瘤胃内的降解特性

选择装有永久性瘤胃瘘管的云南黄牛3只,用尼龙袋法测定六种牧草干物质(DM)、粗蛋白质(CP)的瘤胃降解率。结果表明,苜蓿草和一年生黑麦草的干物质有效降解率显著高于苜蓿草块、光叶紫花苕、大麦秸、非洲狗尾草(P<0.01),但两者之间无显著差异(P>0.05);苜蓿草蛋白质的有效降解率极显著高于苜蓿草块、一年生黑麦草、光叶紫花苕、大麦秸、非洲狗尾草(P<0.01),且大小顺序为:苜蓿草>苜蓿草块>一年生黑麦草>光叶紫花苕>大麦秸>非洲狗尾草。     

奶牛主要饲料原料蛋白质瘤胃降解率的研究

以3头安装永久性瘤胃瘘管的荷斯坦产奶牛为试验动物。用尼龙袋法研究测定了奶牛常用饲料蛋白质在瘤胃内的动态降解规律及其有效降解率。结果表明：常用蛋白质饲料中葵花粕与豆粕粗蛋白（CP）的有效降解率较高。酒糟CP降解率最低。籽实与糠麸类饲料中麸皮CP有效降解率最高，稻壳最低。常用粗饲料中苜蓿草与苜蓿草块的CP有效降解率均高于其他粗饲料，玉米秸秆的CP有效降解率最低。不同饲料蛋白质瘤胃有效降解率与蛋白质慢速降解组分呈极显著中度正相关（r=0．5013，P〈0．01），与蛋白质快速降解组分呈弱的正相关（相关性趋于显著r=0．3675。P=0．06），与非降解组分呈极显著高度负相关（r=-0．7153，P〈0．01）。     

Effects of canola seed supplementation on intake, digestion, duodenal protein supply, and microbial efficiency in steers fed forage-based diets

Fourteen Holstein steers (446 +/- 4.4 kg of initial BW) with ruminal, duodenal, and ileal cannulas were used in a completely randomized design to evaluate effects of whole or ground canola seed (23.3% CP and 39.6% ether extract; DM basis) on intake, digestion, duodenal protein supply, and microbial efficiency in steers fed low-quality hay. Our hypothesis was that processing would be necessary to optimize canola use in diets based on low-quality forage. The basal diet consisted of ad libitum access to switchgrass hay (5.8% CP; DM basis) offered at 0700 daily. Treatments consisted of hay only (control), hay plus whole canola (8% of dietary DM), or hay plus ground canola (8% of dietary DM). Supplemental canola was provided based on the hay intake of the previous day. Steers were adapted to diets for 14 d followed by a 7-d collection period. Total DMI, OM intake, and OM digestibility were not affected (P > or = 0.31) by treatment. Similarly, no differences (P > or = 0.62) were observed for NDF or ADF total tract digestion. Bacterial OM at the duodenum increased (P = 0.01) with canola-containing diets compared with the control diet and increased (P = 0.08) in steers consuming ground canola compared with whole canola. Apparent and true ruminal CP digestibilities were increased (P = 0.01) with canola supplementation compared with the control diet. Canola supplementation decreased ruminal pH (P = 0.03) compared with the control diet. The molar proportion of acetate in the rumen tended (P = 0.10) to decrease with canola supplementation. The molar proportion of acetate in ruminal fluid decreased (P = 0.01), and the proportion of propionate increased (P = 0.01), with ground canola compared with whole canola. In situ disappearance rate of hay DM, NDF, and ADF were not altered by treatment (P > or = 0.32). In situ disappearance rate of canola DM, NDF, and ADF increased (P = 0.01) for ground canola compared with whole canola. Similarly, ground canola had greater (P = 0.01) soluble CP fraction and CP disappearance rate compared with whole canola. No treatment effects were observed for ruminal fill, fluid dilution rate, or microbial efficiency (P > or = 0.60). The results suggest that canola processing enhanced in situ degradation but had minimal effects on ruminal or total tract digestibility in low-quality, forage-based diets.     

Effects of heat treatment on protein feeds evaluated in vitro by the method of estimating utilisable crude protein at the duodenum

The effect of heat treatment on the protein value of field beans, lupins and peas was studied using an in vitro method. Protein feeds were subjected to heat treatment for 30, 60 and 90 min in forced air oven at 120, 140 and 160 °C and in autoclave at 105, 120 and 135 °C. The heat‐treated protein feeds were incubated in buffered rumen fluid together with grass silage and barley in complete isonitrogenous diets. The gas production (GP) was recorded continuously, and ammonia‐N (NH₃‐N) concentrations were determined during the in vitro incubation at 8, 24 and 48 h and used to determine the utilisable crude protein (uCP) at the duodenum at 16 h of incubation (uCP₁₆). Heat treatments decreased the concentration of soluble crude protein and increased neutral detergent insoluble CP (NDICP) in all protein feeds compared to untreated. Inclusion of protein feeds to basal diet showed no increase in the uCP₁₆ in untreated field bean diet and only a small numerical increase in the uCP₁₆ concentrations from 160 g/kg dry matter (DM) to 166 and 172 g/kg DM in untreated lupine and pea diets, respectively, indicating high degradability of untreated feeds. Increasing the time and temperature of the heat treatment linearly increased the uCP₁₆ concentrations in field bean and pea diets, but not in lupin diets. Autoclave treatment was more effective in decreasing uCP₁₆ than oven treatment despite the lower temperatures used. However, the combination of highest temperatures and treatment time in autoclave increased acid detergent insoluble CP (ADICP) concentrations in protein feeds, indicating protein damage and decreased intestinal digestibility. Determining in vitro uCP and ADICP shows to be a promising method for evaluating protein value in heat‐treated animal feeds.     

Protein and amino acid metabolism in the intestinal tract of growing young bulls. 7. Protein estimation and evaluation of protein supply in growing ruminants by the apparently digestible total protein in the duodenum based on rations

The following values were derived from experimental studies of the crude protein (CP) and amino acid (AA) metabolism of growing fattening bulls, the detailed results of which were described in installments 1-6, for the ascertainment of the content of apparently digestible total protein at the duodenum (ADTPD): a) partial method: Degradation quotaCP = NPN + 0.69 X g pure protein/CP; g AD feed PD = g CP (1 -decomposition quotaCP) X 0.72 or g AD feed PD = 0.31 X g pure protein X 0.72; g ADBPDE = 0.149 X g AD org. matter X 0.80 X 0.72 (ADBPDE = apparently digestible pure bacteria protein at the duodenum, dependent on energy release in the reticulo-rumen; g ADBPDN = g CP X (degradation quotaCP) X 0.80 X 0.72 (ADBPDN = apparently digestible pure bacteria protein at the duodenum, dependent on CP supply of rumen microbes); g AD total PD = g AD feed PD + ADBPDE g AD total PD = g AD feed PD + ADBPDN; b) summarizing method: AD total PD = 0.429 + 10.9 X 0.80/CP in % AD org. matter X (CP intake) X 0.72; AD total PD = 0.196 + 16.6 X 0.80/pure protein % AD org. m. X pure pr. intake X 0.72. The requirement of AD total PD was calculated under consideration of the endogenous urine N, skin N and hair N losses as well as protein retention per kg live weight assuming a utilization of 0.70 for this partial performance. The practical application of this balance method is demonstrated in comparison to the digestible CP-system.