In situ rumen degradation and in vitro gas production of some selected grains from Turkey

An investigation of the dry matter degradability (DMD) and effective dry matter degradability (EDDM) was performed for barley, wheat, rye, corn, triticale and oat samples, using the Nylon-bag technique. Gas production (GP), metabolizable energy (ME) and in vitro organic matter digestibility (IVOMD) were also studied by using Hohenheim gas test. The DM from barley, wheat, rye and triticale was digested rapidly in the rumen, and, at the 48 h of incubation, degradability was found to be approximately about 80%. The higher degradability observed for these grains than for oats and corn was attributable to the structure of these grains. In contrast, DM of corn and oats was degraded very slowly and reached 66.7 and 66.5 at 48 h, respectively. Effective degradability values of barley, wheat, rye, corn, triticale and oats were determined to be 61.4, 69.0, 64.0, 41.7, 66.7 and 58.6% in 5% rumen outflow rate, respectively. At the end of the 48 h incubation, total gas productions in barley, wheat, rye, corn, triticale and oats were estimated to be 83.6, 87.2, 87.5, 83.5, 85.8 and 63.9 ml/200 mg DM, respectively. The mean ME values of these grains calculated from cumulative gas amount at 24 h incubation were 11.8, 12.1, 12.3, 10.9, 12.4 and 10.2 MJ/kg DM, respectively. In vitro digestible organic matter of barley, wheat, rye, corn, triticale and oats were estimated to be 85.0, 87.3, 88.2, 79.5, 89.0 and 72.6%. Percentage overall EDDM (k=5%) of barley, wheat, rye, triticale and oats was positively correlated with in vitro GP at 6 h, cumulative GP at 24 h and total GP at 48 h (p<0.05). As a result, in situ dry matter degradation of grains showed great differences depending on the chemical compositions. In situ EDDM of grains may be predicted from in vitro gas production parameters.     

体外发酵产气技术在饲料营养价值评定中的应用

体外产气技术是反刍动物饲料营养价值评定中常用的方法之一。文章比较了体内法、瘤胃尼龙袋法和体外法在反刍动物营养价值评定中的特点,并着重从体外产气技术的技术细节、测定装置和应用范围进行了全面的论述,为该技术的标准化和自动化提供参考。     

In vitro gas production profiles to estimate extent and effective first-order rate of neutral detergent fiber digestion in the rumen

An automatic in vitro gas production technique was evaluated for predicting in vivo fiber (NDF) digestibility and effective first-order digestion rate of potentially digestible NDF (pdNDF) of 15 grass silages. Observed in vivo NDF digestibility of the silages harvested at different stages of maturity during 3 yr was determined by the total fecal collection in sheep fed at the maintenance level of intake. Isolated grass silage NDF was incubated for 72 h in the presence of rumen fluid and buffer to determine the pdNDF digestion kinetics based on cumulative gas production profiles. The digestion kinetic parameters were estimated by a 2-pool Gompertz function. The estimated parameter values were then used in a 2-compartment mechanistic rumen model to predict the in vivo digestibility of pdNDF. A total compartmental mean residence time of 50 h was used in the model, and a further assumption of the distribution of the residence time between the rumen nonescapable and escapable pools in a ratio of 0.4:0.6 was made. To make a distinction between potentially digestible and indigestible NDF, the potential extent of NDF digestion was determined by a 12-d ruminal in situ incubation. The model-predicted in vivo NDF digestibility accurately and precisely (root mean square error = 0.013 units, R(2) = 0.99). Effective first-order digestion rate was estimated from the predicted pdNDF digestibility, and the values were compared with those calculated from the in vivo pdNDF digestibility using the same passage kinetic parameters. The predicted effective first-order digestion rate was strongly correlated with digestion rate estimates derived from in vivo data (root mean square error = 0.006/h, R(2) = 0.86). It can be concluded that a simple first-order digestion rate can be estimated from a complicated gas production kinetic model including 6 parameters. This rate constant can be used in continuous steady-state dynamic mechanistic rumen models predicting the nutrient supply to the host animal.     

Adaptation of the rumen microbial population to native potato starch degradation determined with the gas production technique and the nylon bag technique

Experiments were conducted to investigate the influence of the adaptation of rumen micro-organisms on the degradation of native potato starch (PS) in the rumen. Cows were fed with rations used for gas production (GP) analysis (dry cows, 1.6% starch) and for the nylon bag (NB) technique (lactating cows, 23% starch, mainly maize starch) and a ration containing 19% native PS (lactating cows). Fermentation characteristics of 13 samples were investigated with the GP technique using rumen fluid from cows fed each of the three rations. The same samples were investigated with the NB technique in the cows obtaining the NB ration and the PS ration. The results showed that the rate of GP was influenced by the source of the rumen fluid. The fermentation rate of PS was considerably enhanced by using rumen fluid adapted to the fermentation of native PS instead of using the other rumen fluids. Incubating in cows fed the PS ration, the rate of PS degradation determined with the NB technique, was higher compared with cows fed other rations. Using the PS ration the observed lag period for PS was shorter. The results show a clear influence of ration on the degradation characteristics of starch, determined with both the GP technique and the NB technique. However, these changes in behaviour did not explain observed differences in amounts of rumen escape PS measured in vivo in animal experiments and in situ, using the NB technique.     

体外产气法评价不同方式加工玉米对牦牛瘤胃发酵参数的影响

研究旨在利用常规分析法和体外产气技术评定不同物理加工方式下玉米(蒸汽压片玉米、熟化玉米和普通玉米颗粒)的营养价值。研究结果显示:①与普通玉米(RC组)相比,蒸汽压片玉米(SFC组)和熟化玉米(CC组)的钙(Ca)、酸性洗涤纤维(ADF)的含量没有显著差异(P0.05)。两个处理组的粗灰分(Ash)、粗蛋白(CP)、磷(P)含量和粗脂肪(EE)均比对照组低,总能量(GE)比对照组高;②48 h的SFC组、CC组的发酵速度均高于RC组,但总产气量差异不显著(P0.05)。24、48 h SFC组、CC组的NH3-N浓度、乙丙酸比例(A/P)、丁酸(BUTY)和异戊酸(ISOB)的摩尔比例均显著低于RC组(P0.05),干物质消化率(DMD)显著高于RC组(P0.05),pH值与RC组处理间差异不显著(P=0.255、P=0.406)。综上所述,蒸汽压片玉米和熟化玉米能提高动物对营养物质的消化和吸收。对pH值、48 h总产气量没有影响,会显著降低(P0.05)瘤胃液的NH3-N浓度、乙丙酸比例,显著提高干物质降解率(DMD)和丙酸(PRO)摩尔比例(P0.05)。     

利用体外产气法研究戊酸对山羊瘤胃发酵的影响

应用体外产气法模拟瘤胃发酵,通过测定24 h体外累计产气量、细菌氮含量和中性洗涤纤维(NDF)的降解率,评价戊酸的不同添加水平对山羊瘤胃发酵的影响.试验采用单因子设计,戊酸的添加水平分别为0%、0.3%、0.6%、0.9%、1.2%,每个水平4个重复.结果表明与对照组相比,添加0.6%的戊酸组能显著提高24 h累计产气量(P＜0.05)和极显著提高细菌氮含量(P＜0.01);在添加戊酸水平为0%～0.3%时,NDF降解率有提高的趋势,但是差异不显著(P＞0.05),在0.3%～1.2%时,其NDF降解率显著下降(P＜0.05).建议日粮中戊酸的适宜添加水平为0.6%.     

Technical note: a modified three-step in vitro procedure to determine intestinal digestion of proteins

An in vitro, batch incubator (Daisy(II)) was used to simplify the 3-step, in vitro procedure (TSP) to reduce the cost and labor involved in the determination of intestinal digestion of proteins. Four tests were conducted to study the effects of the type of pepsin (P-7012 and P-7000; Sigma, St. Louis, MO), the type of bags used for the incubation of samples (R510 and F57; Ankom Technology, Fairport, NY), the amount of sample per bag (0.5, 1, 2, or 5 g), and the number of bags per incubation bottle (5, 15, 20, or 30 bags) on the estimated intestinal digestion of proteins. A soybean meal sample heated at 170 degrees C for 0, 0.5, 1, 2, 4, 6, or 8 h was used in all preliminary tests to determine the optimum conditions of the technique. The intestinal digestion of 12 protein supplements was determined using the Daisy(II) as well as the proposed TSP techniques. Results using the 2 types of pepsin were highly correlated: P-7012 = (0.99 +/- 0.04 x P-7000) -0.29 +/- 2.33 (r2 = 0.99, P < 0.001, n = 14). Intestinal digestion of soybean meal samples obtained from the TSP assay were highly correlated with those obtained using the Daisy(II) incubator with Ankom R510 bags: Daisy(R510) = (1.37 +/- 0.06 x TSP) -15.45 +/- 3.85 (r2 = 0.98, P < 0.001, n = 14); and Ankom F57 bags: Daisy(F57) = (1.33 +/- 0.06 x TSP) -15.76 +/- 3.87 (r2 = 0.98, P < 0.001, n = 14). Although there was a bias in these equations, when the whole protocol was applied to the determination of intestinal digestion of the 12 protein supplements using the TSP or the Daisy(II) technique with the Ankom R510 bags, the data were highly correlated: (0.93 +/- 0.12 x TSP) + 6.78 +/- 9.09 (r2 = 0.84, P < 0.001, n = 12). The amount of sample per bag and the number of bags per incubation bottle did not affect the estimates of intestinal digestion of proteins. These results indicate that the use of up to 30 nylon bags (Ankom R510) with 5 g of sample in each Daisy(II) incubation bottle could be used to estimate intestinal digestion of proteins in ruminants.     

In vitro gas production in rumen fluid of buffalo as affected by urea‐calcium mixture in high‐quality feed block

This study aimed to determine the effect of urea‐calcium sulphate mixture (U‐cas) levels in high‐quality feed block (HQFB) on ruminal digestibility, fermentation and gas kinetics in rumen fluid of swamp buffalo by using in vitro techniques. The treatments were seven levels of U‐cas incorporated in HQFB at 0, 3, 6, 9, 12, 15 and 18% and the experimental design was a completely randomized design. Gas production rate constants for the insoluble fraction, potential extent of gas and cumulative gas were linearly increased with increasing levels of U‐cas in HQFB. The in vitro dry matter digestibility, in vitro organic matter digestibility, true digestibility and microbial mass were altered by treatments and were greatest at 18% U‐cas supplementation. Concentrations of propionate were linearly increased with increasing levels of U‐cas and was highest with U‐cas supplementation at 18%. The NH₃–N concentration was highest when urea was added in the HQFB while NH₃–N concentration tended to be reduced with increasing level of U‐cas. The findings suggest supplementation of 18% U‐cas in HQFB improves kinetics of gas production, rumen fermentation, digestibility and microbial mass as well as controlling the rate of N degradation in the rumen of swamp buffalo.     

In situ starch and crude protein degradation in the rumen and in vitro gas production kinetics of wheat genotypes

The objective of this study was to determine the variation of in situ ruminal degradation characteristics of dry matter (DM), crude protein (CP) and starch (ST), and to determine the effective degradation (ED) of wheat genotypes. Further, multivariate associations of these in situ values with their corresponding in vitro gas production (GP) kinetics and laboratory measurements were evaluated using correlation and multiple linear regression analyses. Grains of 20 genotypes of wheat were characterized by proximate constituents, amino acid (AA) composition and physical characteristics. Ruminal degradation kinetics were determined by in situ degradation of DM, CP and ST, and subsequent evaluation of in vitro GP relative to time courses. In situ and GP measurements were fitted to an exponential equation, and ED was calculated using passage rates in the rumen of 5%/h (ED5) and 8%/h (ED8). To predict ED8 of CP (EDCP8) and ST (EDST8), correlations were evaluated and stepwise multiple linear regression analyses were applied. Estimated degradation parameters varied considerably between wheat genotypes irrespective of the nutrient tested. Variance in a, b and c was not reflected in the variation of the ED, due to high degradation rates (c). The assumed passage rate also impacted estimation of the ED minimally. Estimated GP parameters varied only slightly among wheat genotypes. Nevertheless, regression models explained up to 80 and 99% of the variance in EDCP8 and EDST8, respectively, and associations between EDST8 and EDCP8 and chemical and physical characteristics of grains were detected. As ST is the primary nutrient in wheat grains and can comprise substantial portions of dairy rations, the total amount of ST as well as its ED in the rumen should be taken into account when wheat is incorporated into dairy rations. Conversely, variance in wheat grain CP degradation was very low and can largely be neglected in practical ration formulation for ruminants.     

Quantitative studies of the in vitro production of pipecolic acid by rumen protozoa and its degradation by rumen bacteria

An in vitro study was conducted to quantitatively investigate the metabolism of pipecolic acid (Pip), a neuromodulator, by mixed rumen bacteria (B), mixed rumen protozoa (P), a combination of B and P (BP), species‐enriched rumen protozoal suspension (Polyplastron sp., Diploplastron sp., entodinia and Entodinium caudatum) and pure cultures of several isolates of rumen bacteria (Prevetolla bryantii, Prevetolla albensis, Streptococcus bovis, Veillonella parvula, Megasphaera elsdenii and Ruminococcus albus). Only P produced Pip from L‐lysine (1.0 mmol/L L‐Lys) at a rate of 83.5 ± 1.6 µmol/L/h and even in BP, Pip was produced from L‐Lys by P and increased at a rate of 31.2 ± 3.8 µmol/L/h. Pip production by P was highest when the substrate (L‐Lys) concentration was 6 mmol/L and then the rate was 580 ± 36 µmol/L/h. Pipecolic acid production by P suspension enriched with different species of protozoa showed that Polyplastron sp. had the highest Pip production rate of 0.907 ± 0.092 µmol/L/mg protozoal protein per h, and Diploplastron sp. had the lowest rate of 0.55 ± 0.13 µmol/L/mg protozoal protein per h. The addition of D‐Lys (1.0 mmol/L) as a substrate to the P suspension revealed that P were also able to produce Pip from D‐Lys, though at a lower rate (1/3) compared with L‐Lys (1.0 mmol/L), suggesting the presence of epimerases in P. It was confirmed that B were unable to produce Pip from L‐ or D‐Lys. Only B degraded Pip (1.0 mmol/L) after a lag phase at a rate of 56.0 ± 1.5 µmol/L/h. The B suspension was able to degrade D‐Lys, though the products were not identified. Pip degradation by pure culture of some species of rumen bacteria showed that P. bryantii and R. albus had the highest rate followed by P. albensis, S. bovis and M. elsdenii with a low rate of Pip degradation. Veillonella parvula showed no ability to degrade Pip. The results suggest that a fairly large proportion of rumen‐produced Pip is likely to be absorbed by the host animal before degradation by rumen bacteria.     

Rumen fermentation and degradability in buffalo and cattle using the in vitro gas production technique

An in vitro trial was conducted to investigate the effect of different inoculum sources (buffalo vs. cattle) on rumen fermentation and degradability. Incubations were carried out using rumen fluid obtained from buffalo or cattle fed the same diet [60% grass hay and 40% concentrate; 18 kg dry matter (DM)/day]. The fermentation kinetics of eight feeds commonly used in ruminant nutrition (alfalfa hay, barley meal, beet pulp, corn meal and silage, ryegrass hay and silage and soya bean meal s.e.) were studied with the in vitro gas production technique and rumen fermentation parameters (substrate disappearance, pH and volatile fatty acids production) were determined after 120 h of incubation. The linear relationship indicates that the microbial metabolic pathways of the two inocula for all the substrates were qualitatively similar, albeit often quantitatively different. In this in vitro study, a significant influence of rumen inoculum (buffalo vs. cow) on fermentation and degradability of the examined substrates was found. The differences in buffalo and cattle rumen fermentation can be explained with a different microbial activity of the two ruminant species, because of different amount of microbial population or microbial population constituted by different species of bacteria and protozoa.     

体外产气法与尼龙袋法评定粗饲料干物质降解率的相关性分析

为寻求可在实验室条件下简单地评定饲料降解性能的方法,试验以玉米秸秆及不同尿素、石灰比例复合处理的玉米秸秆为发酵底物,对饲料体外产气量和尼龙袋瘤胃干物质降解率作了相关性分析。统计分析表明,体外产气量与体内干物质降解率呈高度正相关,相关系数分别为:对照组0.967、料A0.964、料B0.999和料C0.994。结果证明,在对饲料降解性能及潜在可降解能力作快速、定性判断时,体外产气法可以代替尼龙袋法。     

Technical note: A model to estimate individual feed intake of swine in group feeding

In most animal growth experiments, groups of animals are housed within a pen. Occasionally, an individual animal shows a very different growth rate than its pen mates or dies during the experiment. When this happens, if pen feed intake (PFI) cannot be reestimated for the calculation of ADFI and feed efficiency, an observation will be lost from the data set. Therefore, we propose a model to estimate individual feed intake (IFI) of pigs in group feeding, with subsequent validation of the model using group feeding simulation studies. In the proposed model, the feed intake (FI) of each affected pen is partitioned into FI for maintenance (FI(m)) and FI for growth (FI(g)) for each animal within that pen. First, individual pig FI(m) for the period is calculated using the 1998 National Research Council estimation of ME for maintenance. Then, FI(m) for all pigs in the pen is summed. The difference between the summed FI(m) and the total PFI is that which supported growth in the pen. Next, FI(g) is calculated by apportioning the remaining feed equally to each unit of gain within the pen. Finally, the estimated IFI for the pig being removed from the pen is the sum of FI(m) and FI(g) for that pig; this FI estimate is subtracted from the original PFI to leave the new PFI for the remaining pigs. The validity of the estimated IFI is dependent on the accuracy of the maintenance energy equation and the energy analysis of the feedstuffs. In simulation studies, we compared the accuracy of the proposed method with 2 other methods. In simulation study 1, the proposed model showed better accuracy than at least one of the other methods during all tested periods (P < 0.001). In simulation study 2, the greater accuracy of the proposed method compared with 2 other methods was demonstrated again. Because calculation of IFI is relatively cumbersome, we developed a feed intake correction spreadsheet (FICS), an Excel spreadsheet containing macros for FI correction. All of the calculation procedures in the proposed model are included within the feed intake correction spreadsheet. The Excel file and instructions are being made available via a Web site.     

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。     

大豆油不同添加水平对瘤胃体外发酵和产气的影响

本试验通过体外培养,研究在精粗比为30:70(偏粗型)日粮类型条件下,不同大豆油添加水平对产气量、甲烷产量、pH值和纤维降解率的影响.结果表明:随着大豆油添加水平的提高,产气量和甲烷产量逐渐降低,且各添加组显著低于对照组;pH值随着培养时间的延长,各添加水平在不同培养时间点与对照组相比均上升,其中添加量为4%和6%与对照组相比差异显著(P<0.05),添加量为8%时,与对照组相比差异极显著(P<0.01);培养24 h后.纤维降解率的抑制潜力8%水平最大,与对照组相比差异极显著(P<0.01),其次是6%的添加水平.与对照组相比差异显著(P<0.05).而2%和4%添加水平对纤维降解率的抑制程度与对照组相比差异不显著(P>0.05).通过产气量、pH值和纤维降解率综合考察大豆油对瘤胃体外发酵和产气的影响,本试验得出大豆油的最适添加量为4%.     

利用体外培养法建立饲料营养成分与瘤胃丙酸产量的回归模型

根据美国康乃尔净碳水化合物和蛋白质体系 (CNCPS) ,分析测定了 4类 2 4种饲料的营养成分 ,利用体外批次培养技术测定了它们在体外培养一定时间后的丙酸产量 ,并由此建立了饲料中产丙酸的营养成分和瘤胃丙酸产量的回归方程     

Technical note: A novel technique to assess internal body fat of cattle by using real-time ultrasound

The objectives of this study were to describe a system to assess KPH fat by using real-time ultrasound (RTU) and to develop equations to predict total physical separable internal fat (IFAT) based on ultrasound measurements. Data for this study were obtained from 24 Angus steers fed either hay- or corn-based diets during the backgrounding phase. Steers were serially slaughtered in 3 groups: at weaning (baseline), then at 4 and 8 mo after weaning. A fourth group was composed of 4 steers from the hay-fed group that were slaughtered at approximately 10 mo after weaning. The RTU measurements were collected every 2 mo, with a preslaughter scan approximately 7 d before the slaughter time. The RTU measurements consisted of 12th- to 13th-rib backfat thickness, 12th to 13th ribeye area, percentage of intramuscular fat, and kidney fat depth, which was measured in a cross-sectional image collected between the first lumbar vertebra and the 13th rib. For kidney fat, the ultrasound probe was placed on the flank region approximately 15 cm from the midline of the animal. Images were stored in the ultrasound console, and measurements were taken between the ventral part of the iliocostalis muscle and the end of the KPH fat at the chute side. The relationship between carcass and ultrasound measurements in the depths of kidney fat (cKFd and uKFd, respectively) had an r(2) of 0.93, with a root mean square error (RMSE) of 1.14 cm. An allometric regression between carcass KPH weight (cKPHwt) and cKFd was identified, and the untransformed regression had an r(2) of 0.96. The linear regression between total IFAT and cKPHwt had an r(2) of 0.97, with an RMSE of 2.67 kg. Therefore, a system was developed to predict IFAT from uKFd measurements by combining these equations. Additionally, a single linear regression between IFAT and uKFd measurements was developed (r(2) = 0.89, RMSE = 5.32 kg). Even though the system of equations had a lower RMSE of prediction and greater r(2) compared with the single linear regression (4.80 vs. 5.10 kg and 0.91 vs. 0.89, respectively), there was no difference between these methods in predicting IFAT (P = 0.4936) by using a pairwise mean square error of prediction analysis. Our results indicated that uKFd measurements can accurately and precisely predict the cKFd of steers consuming either high concentrate or forage rations. The results also showed that cKFd is highly correlated with cKPHwt, which can be used to estimate total IFAT. More research is needed to further evaluate this technique with different feeding strategies, breeds, and sexes.     

Comparison of mathematical models to describe disappearance curves obtained using the polyester bag technique for incubating feeds in the rumen.

Different nonlinear models were evaluated as candidates to describe ruminal degradation kinetics of forages from data obtained by the incubation of the feeds in the rumen using polyester bags. Nine models were used: segmented model with three straight lines (Mod0); simple Mitscherlich or exponential (Mod1); inverse polynomial (Mod2); compartmental model with two exponential terms (Mod3); generalized Mitscherlich (Mod4); generalized Michaelis-Menten (Mod5); logistic (Mod6); Gompertz (Mod7); and generalized Von Bertalanffy (Mod8). All these models can be represented in the general form D = W + S0 x phi(t), where D is in situ disappearance at incubation time t, W and S0 are positive scalars, and phi is a positive monotonically increasing function unique to each of the models studied. Based on first principles, a general formula for calculating the extent of degradation of feeds in the rumen has been derived that is applicable to all the models. The disappearance curves of different feed components (DM, N, and NDF) of 87 Mediterranean forages (i.e., a total of 261 curves) were fitted to all the models. A comparative study was carried out based on the mathematical, statistical, and biological characteristics of the models. Flexible models that can accommodate both diminishing returns and sigmoidal behavior were more appropriate in describing the curves. A discrete-lag parameter was introduced into Mod0, Mod1, and Mod2 to describe the initial stage of the disappearance curve, and this parameter considerably improved the fit of experimental data. Based on statistical criteria, models Mod1, Mod4, Mod5, and Mod8 were better than the others for most statistical tests and disappearance curves, but differences among these four models were not consistent. The estimates of degradation parameters to quantify the rate (half-life, fractional degradation rate), and extent (undegradable fraction, effective degradability) of ruminal degradation of feeds were also used as a means to discriminate between models, although in most cases all of the models gave similar values of the degradation parameters. In particular, when the extent of degradation was calculated for each forage and feed component, differences between the estimates obtained with the different models were of little nutritional significance for the animal.     

Influence of S. babylonica extract on feed intake, growth performance and diet in vitro gas production profile in young lambs

An experiment was completed to determine the effect of Salix babylonica (SB) extract supplementation to the diet of growing lambs. Eighteen Katahdin × Pelibuey male lambs (14?±?2 kg live body weight) were divided randomly in individual cages into three groups and fed three diets varying in SB: a control group was fed on total mixed ration (TMR) without SB (SB0), an SB25 group was fed on TMR plus SB extract at 25 mL/lamb/day, and an SB50 group was fed on TMR plus SB extract at 50 mL/lamb/day on dry matter intake (DMI), average daily gain (ADG), feed efficiency, and in vitro gas production (GP) in lambs fed on TMR. In vitro GP of the TMR fed to lambs was recorded at 2, 4, 6, 8, 10, 12, 24, 48, and 72 h of incubation with 0, 0.6, 1.2, and 1.8 mL extract per gram of DM. Addition of SB extract at low and high doses improved the DMI of lambs by 59.9 and 33.2 %, respectively. Relative to the control, low and high extract doses achieved greater lamb ADG during the experimental period. The asymptotic GP increased (P?<?0.05) with increasing dose of SB extract without affecting the rate of GP or the initial delay before GP begins. Linear increases for in vitro GP with advancing time with different SB extract doses were observed. It is suggested that the use of S. babylonica extract with the rate of 25 mL/lamb/day is beneficial to young lamb’s performance growth and thus can be safely used as a feed additive in diets without any negative effects on animal health.     

Improvement and validation of the method to determine neutral detergent fiber in feed

To improve the performance of the analytical method for neutral detergent fiber in feed with heat‐stable α‐amylase treatment (aNDFom), the process of adding heat‐stable α‐amylase, as well as other analytical conditions, were examined. In this new process, the starch in the samples was removed by adding amylase to neutral detergent (ND) solution twice, just after the start of heating and immediately after refluxing. We also examined the effects of the use of sodium sulfite, and drying and ashing conditions for aNDFom analysis by this modified amylase addition method. A collaborative study to validate this new method was carried out with 15 laboratories. These laboratories analyzed two samples, alfalfa pellet and dairy mixed feed, with blind duplicates. Ten laboratories used a conventional apparatus and five used a Fibertec^® type apparatus. There were no significant differences in aNDFom values between these two refluxing apparatuses. The aNDFom values in alfalfa pellet and dairy mixed feed were 388 g/kg and 145 g/kg, the coefficients of variation for the repeatability and reproducibility (CV_r and CV_R) were 1.3% and 2.9%, and the HorRat values were 0.8 and 1.1, respectively. This new method was validated with 5.8% uncertainty (k = 2) from the collaborative study.