Prediction of digestible energy value of extruded dog food: comparison of methods

The proposal of National Research Council (NRC), based on the use of modified Atwater factors, is nowadays the widely used method to estimate digestible energy (DE) content of pet foods. Recently, alternative methods have been suggested for predicting energy content of commercial canine dry food. Factorial equations including food fibre content as estimator, in vitro digestions methods or near-infrared spectroscopy (NIRS) techniques have been considered as good approaches to predict the energy content of dog foods. The aim of this study was to compare the accuracy of some of those estimation methods. Seventeen samples of commercial extruded dog food were used to validate and compare some estimation methods of energy digestibility (Ed, %) and DE value [MJ/kg dry matter (DM)]. The apparent Ed and DE of each food were previously determined by in vivo trials. In vivo Ed and DE of foods ranged from 79.30% to 91.05% and from 16.25 to 21.82 MJ/kg DM, respectively, and their crude fibre (CF) content ranged from 0.72% to 3.28% (in DM base). The % Ed of each sample was estimated by the factorial equation (% Ed = 91.2 - 1.43 x CF %) and by the in vitro digestion method [% Ed(in vitro) = -2.45 + 0.98 organic matter (OM) disappearance(in vitro)%]. The set of samples also was analysed by NIRS, using a calibration equation developed from a set of 69 samples of commercial extruded dog food (0.76 and 0.89 cross-validation r(2) and 2.33 and 0.61 cross-validation SE for Ed and DE respectively). The in vitro method gave better estimations of Ed in vivo than NIRS and factorial methods, although all the methods assessed showed a very good and similar accuracy in the prediction of DE value. These three methods showed a slight better accuracy than that previously proposed by the NRC. To consider constant digestibility values of nutrient content of food can result in bias and error in the estimated energy values. The alternative prediction methods used in this study take into account differences of ingredient composition and availability of nutrients of different extruded dog foods thus could be better systems of valuating energy content in a wider range of different kind of foods than in use method.     

Prediction of in vivo apparent total tract energy digestibility of barley in grower pigs using an in vitro digestibility technique

The DE content within cereal grains can vary 25% mainly due to changes in apparent total tract digestibility (ATTD) of energy. In vitro digestibility techniques have been developed to predict the DE value among feedstuffs. However, these techniques have not been tested properly for their suitability to predict the variation in energy digestibility and DE content within a cereal grain. The objective of the present study was to establish and evaluate an in vitro digestibility technique to predict in vivo ATTD of energy of barley in grower pigs. Barley grain samples (hulled, n = 21) with a large range in quality were collected; the ADF and CP content ranged from 4.5 to 11.4% and 10.0 to 16.4% (DM basis), respectively. The ATTD of energy was determined using barrows (n = 63, 33 +/- 2.1 kg of initial BW) in 2 periods with 6 observations per sample and ranged from 51.9 to 78.5%, with relative errors between 0.4 and 5.0%. A preliminary study, comparing a 2- and a 3-step in vitro digestibility technique using 3 barley samples, indicated that R(2) between in vivo and in vitro energy digestibility was greater using the 3- than the 2-step technique (0.92 vs. 0.76). Therefore, the 3-step in vitro digestibility technique was used solely in subsequent analyses. Briefly, ground barley was subsequently incubated with pepsin for 6 h, pancreatin for 18 h, and cellulase for 24 h. The DM and GE content of samples and residues were measured to calculate digestibility. The in vitro energy digestibility of the 21 barley samples with duplicate measurements ranged from 63.7 to 82.2%, with relative errors between 0.1 and 2.6%. In vitro energy digestibility was strongly related (y = 1.25 x - 25.22; R(2) = 0.81) to in vivo energy digestibility. Finally, a subset of 7 barley samples was analyzed in quadruplicate using the 3-step in vitro technique. The relationship between in vitro and in vivo energy digestibility was very strong (y = 1.23 x - 25.33; R(2) = 0.97) with relative errors between 0.5 and 2.7%. In vitro DE and energy digestibility were perfectly related (R(2) = 1.00). In summary, the 3-step in vitro energy digestibility technique can accurately predict the ATTD of energy in barley in grower pigs. The 3-step in vitro digestibility technique, thus, might be useful as the reference laboratory procedure to calibrate analytical equipment to rapidly predict the ATTD of energy in barley.     

Prediction of digestible protein content of dry extruded dog foods: comparison of methods

The aim of this study was to check the accuracy of laboratory methods to predict the apparent protein digestibility (CPd, %) and digestible protein content (DP, g/kgDM) of dog foods, avoiding the use of experimental animals in digestion trials. Twenty‐eight commercial dry extruded dog foods were tested by three different methodologies: an adaptation of the in vitro incubation method described by Hervera et al. (J Anim Physiol Anim Nutr 2007, 91 : 205) for estimation of digestible energy of commercial dog foods, a modification of the pH drop methodology proposed by Hsu et al. (J Food Sci 1977, 42 : 1269) for protein evaluation of human foods and the Near Infra Red Spectroscopy (NIRS) technology. All the methods assessed revealed very good, similar accuracy in the prediction of DP content either using the in vitro method (r = 0.99; RSD = 6.76; CV = 2.31%), the pH drop method (r = 0.99; RSD = 6.94; CV = 3.02%) or the NIRS (R2 = 0.96; SECV = 10.50) method, although the in vitro digestion method showed the highest accuracy approach of in vivo crude protein apparent digestibility: CPd in vitro (r = 0.81; RSD = 2.01; CV = 2.41%); CPd pH‐drop (r = 0.78; RSD = 2.48; CV = 2.98%) and NIRS (r²cv = 0.53; SECV = 2.37).     

我国奶牛饲料产奶净能值测算方法的研究

本文将国内有关的奶牛消化代谢试验和单一饲料消化率试验材料进行整理和统计分析,制定出适合我国实际情况的根据饲料可消化能推算饲料产奶净能的回归公式,完善了我国的奶牛饲养标准。     

The effect of crude fibre on apparent digestibility and digestible energy content of extruded dog foods

The apparent digestibility of nutrients and energy of 38 commercial dry extruded dog foods was measured using six adult (2 to 3 year-old) female Beagles. Diets contained [in g/kg dry matter (DM)]: 164–360 crude protein (CP); 79–261 ether extracts (EE); 8–33 crude fibre (CF) and 318–585 nitrogen free extracts (NFE). Apparent energy digestibility ranged from 77.3 to 91.6%, and was closely related to CF content ( r =–0.85), yielding the resultant equation: GED (%)=94.00 – 4.04 × CF (% DM). The estimation of digestible energy content of foods from digestibility coefficients predicted from the above equation and gross energy measured or estimated from the Weende fractions, provides a more accurate prediction of experimental values than the Atwater approach followed by the National Research Council and the Association of American Feed Control Officials.     

麦麸猪消化能与能量消化率预测方程的建立

本试验旨在测定麦麸的猪消化能(DE)及麦麸各化学成分对DE与能量消化率(DCE)的影响,分析用麦麸化学成分建立其DE与DCE的预测方程。试验选用12头三元杂交(杜×大×长)去势公猪[初始体重为(36.6±2.9)kg],采用2个6×6拉丁方试验设计(6期,11种饲粮),应用全收粪法测定10种不同产地和批次麦麸的DE,通过分析麦麸原料中的粗蛋白质(CP)、粗纤维(CF)、酸性洗涤纤维、中性洗涤纤维、淀粉(St)、粗脂肪、粗灰分、总能与DE及DCE之间的相关关系,筛选出最佳的预测因子并建立预测方程。结果表明:10种麦麸的平均DE为11.72 MJ/kg(干物质基础),平均DCE为61.31%,St为DE和DCE的最佳预测因子。推荐DE预测方程:DE=0.31×St+3.71(R2=0.76,RSD=0.42,P<0.01)、DE=-0.91×CF-0.71×CP+33.80(R2=0.76,RSD=0.35,P<0.01)。推荐DCE预测方程:DCE=1.70×St+22.28(R2=0.76,RSD=2.89,P<0.01),DCE=-5.02×CF-3.65×CP+182.81(R2=0.80,RSD=1.79,P<0.01)。由此可知,本试验利用麦麸原料营养成分建立的DE及DCE的预测方程相关指数较高,且由本试验结果预测的DE值比较准确。     

陕北白绒山羊羯羊能量和蛋白质需要量

本试验旨在研究陕北白绒山羊羯羊能量和蛋白质的需要量,为制定其饲养标准提供数据。选取36只体重相近、健康状况良好的陕北白绒山羊周岁羯羊,按3×3(能量×蛋白质)完全随机设计分为9组,每组4个重复,每个重复1只。各组饲粮消化能和粗蛋白质水平分别参照NRC(1981)推荐量的100%、110%、120%和90%、110%、130%设定。预试期7 d,正试期46 d。结果表明:1)饲粮能量水平对周岁羯羊的干物质采食量和平均日增重都有极显著影响(P0.01),蛋白质水平对干物质采食量影响显著(P0.05);饲粮能量和蛋白质水平对干物质采食量有显著的互作效应(P0.05)。2)低能量水平组的可消化氮显著低于中能量水平组与高能量水平组(P0.05);低蛋白质水平组的进食氮、可消化氮、沉积氮、氮表观消化率均极显著低于中蛋白质水平组和高蛋白质水平组(P0.01)。3)总能消化率和总能代谢率均随着能量水平的提高而极显著地升高(P0.01);高蛋白质水平组的总能代谢率和消化能代谢率显著低于低蛋白质水平组(P0.05);能量和蛋白质水平对总能消化率、总能代谢率和消化能代谢率均产生显著或极显著的互作效应(P0.05或P0.01)。本试验得到了陕北白绒山羊周岁羯羊能量和蛋白质需要量的回归方程,饲粮的消化能和代谢能分别以8.80~10.61 MJ/kg和7.34~8.76 M J/kg较为适宜,粗蛋白质和可消化粗蛋白质分别以10.00%和7.34%为宜。     

Apparent digestibility of nitrogen and nitrogen retention of forages fed to steers in metabolism stalls

Holstein steers in metabolism stalls were utilized to determine apparent digestibility of N (DN), N retention (NR) expressed as a percentage of total N consumed, and Mcal/kg digestible energy (DE) when diets of seven different classes of forages were fed. The best predictive equation for digestibility of N in the 153 forages studied was DN(%) = -98.1065 + 11.4724 (%CP) + 41.4475 (DE) - .1498 (%CP)2 - 1.2541 (DE)2 - 1.9309 (CP) (DE), with R2 = .74 and Sy.x = 8.63, where %CP is the percent crude protein of the forage. The best predictive equation for DN of sorghum silages, corn silages, legume hays and temperate grass hays contained both %CP and DE as predictor variables. The best predictive equations for DN of sorghum-sudan and bermudagrass hays contained only %CP and (%CP)2 as predictor variables. The predictive equation for DN of 14 alfalfa hays involved only the linear relationship to %CP. The best scheme for predicting NR as a percentage of N consumed in 116 forages was a combination of three equations as follows: 1) NR(%) = -47.0797 + 6.4733 (%CP) - .1542 (%CP)2 for forages, where DE = less than 2.42 Mcal/kg; 2) NR(%) = -67.6306 + 10.1354 (%CP) - .2726 (%CP)2, where DE = 2.42 - 2.87 Mcal/kg; and 3) NR(%) = 28.3458 + 4.4722 (%CP) - .1263 (%CP)2, where DE = greater than 2.87 Mcal/kg; R2 = .42 and Sy.x = 14.86.(ABSTRACT TRUNCATED AT 250 WORDS)     

Energy evaluation of extruded compound foods for dogs by near-infrared spectroscopy

Near-infrared reflectance spectroscopy (NIRS) was used to predict the chemical composition, apparent digestibility and digestible nutrients and energy content of commercial extruded compound foods for dogs. Fifty-six foods of known chemical composition and in vivo apparent digestibility were analysed overall and 51 foods were used to predict gross energy digestibility and digestible energy content. Modified partial least square calibration models were developed for organic matter (OM), crude protein (CP), ether extract (EE), crude fibre (CF), nitrogen free extracts (NFE) and gross energy (GE) content, the apparent digestibility (OMD, CPD, EED, NFED and GED) and the digestible nutrient and energy content (DOM, DCP, DEE, DNFE and DE) of foods. The calibration equations obtained were evaluated by the standard error and the determination coefficient of cross-validation. The cross-validation coefficients of determination (R) were 0.61, 0.99, 0.91, 0.96, 0.94 and 0.92 for OM, CP, EE, CF, NFE and GE, the corresponding standard error of cross-validation (SECV) being 5.80, 3.51, 13.35, 3.64 and 16.95 g/kg dry matter (DM) and 0.29 MJ/kg DM respectively. The prediction of apparent digestibility was slightly less accurate, but NIRS prediction of digestible nutrient (g/kg DM) and DE (MJ/kg DM) gave satisfactory results, with high R (0.93, 0.97, 0.93, 0.83 and 0.93 for DOM, DCP, DEE, DNFE and DE respectively) and relatively low SECV (11.55, 6.85, 12.14 and 22.98 g/kg DM and 0.47 MJ/kg DM). It is concluded that the precision of NIRS in predicting the energy value of compound extruded foods for dogs is similar or better than by proximate analysis, as well as being faster and more accurate.     

不同品种小麦生长猪消化能与代谢能预测模型的建立

本试验旨在研究不同品种小麦的理化特性及对生长猪的消化能和代谢能值,并探讨通过理化特性建立消化能与代谢能预测模型的可行性。试验选取12头初始体重相近(50.1±2.8)kg的杜×长×大三元杂交去势公猪,随机分成2组,每组6头猪,采用2个6×6拉丁方设计,试验共6期。采用直接法评定12个小麦样品的能量价值,每个小麦样品配制1种日粮,共12种日粮,小麦在日粮中所占比例为97.0%。结果表明:12个不同品种小麦的能值差异极显著(P<0.05),其中北麦4的消化能含量最低(16.40 MJ/kg DM),而龙麦30的消化能含量最高(17.01 MJ/kg DM)。北麦4的代谢能含量亦最低(15.72 MJ/kg DM),辽春10最高(16.48 MJ/kg DM)。通过回归分析,建立了以总能和理化特性为基础的小麦消化能和代谢能预测模型,推荐预测模型:DE=-829-58.4×ADF+1.1×GE(R2=0.79,RSD=24.5),DE=-1384+1.1×GE+0.65×BW(R2=0.79,RSD=24.8),ME=-2990+1.7×GE-50.2×Xylans-87.6×Ash(R2=0.88,RSD=21.1)。     

波尔山羊×隆林杂交羔羊育肥期能量和蛋白质营养需要的研究

试验旨在研究育肥期波本杂肉羊能量和蛋白质营养需要量参数,筛选出一个最佳能量和蛋白质搭配的饲料配方,为科学饲养提供理论依据和生产指导。试验选择16只3月龄断奶波隆杂交F1代公羔,采用4×4拉丁方设计,以NRC（1981）营养需要推荐量为参考设计了低能低氮、高能低氮、低能高氮和高能高氮（NRC）4种能氮比日粮,分别为日粮1、2、3和日粮4。试验结果表明,舍饲波隆杂交羔羊育肥期对象草 玉米型日粮干物质采食量与代谢体重和日增重的关系为：DMI（g/d）=181.3W0.75－0.61ΔW－886.2（r=0.9287）;舍饲波隆杂羔羊育肥期粗蛋白质（CP）、总能（GE）、消化能（DE）需要量的估测模型分别为：CP（g/d）=19.56 W0.75＋0.25ΔW－128.6（r=0.7836）,GE（MJ/d）=2.98 W0.75＋0.023ΔW－18.69（r=0.8257）,DE（MJ/d）=1.26 W0.75－.006ΔW－3.56（r=0.6236）;3~6月龄舍饲育肥期波隆杂羔羊,日粮总能代谢率平均为0.49%,粗蛋白质的消化率平均为0.63%,每增重1 g体沉积蛋白质需要量为0.32 g。     

Effect of cutting and vacuum cleaning on the digestibility of oats by horses

Three mature Quarter Horse geldings were used in 2 Latin square experiments to measure the effect of cutting and vacuum cleaning of oats on digestibility. The horses were fed at the maintenance level of digestible energy (DE) as recommended by the NRC.¹²The data were analyzed by Latin square analysis of variance, and Tukey's t test was used to determine any differences between specific means.No significant differences among treatments were observed during either experiment, indicating that the digestibility of nutrients from oats was not affected by cutting and vacuum cleaning. Differences in the digestibility of the ether extract (EE) fraction between periods of experiment 1 were noted.     

Urinary energy losses in dogs fed commercial extruded foods

Energy and nitrogen losses in the urine were recorded in 134 individual balances with adult (1- to 2-year-old) female Beagles that were fed 23 dry extruded dog foods ranging in crude protein (CP) content from 242 to 360 g/kg dry matter. The energy equivalent of urinary nitrogen was estimated as 33.9 kJ/g N. Both energy losses in the urine corrected for the nitrogen balance, and the metabolizable energy (MEn): digestible energy (DE) ratio were found to be closely related to diet CP content (r : 0.851 and 0.820). The MEn content of extruded dog foods can be accurately calculated from the DE content, either by subtracting 4.59 MJ/kg CP or estimating the MEn/DE ratio from the food CP content by the following equation: MEn/DE=0.98 – 3.44 ± 0.517 × CP (kg/MJ DE).     

酶水解法评定鹿饲料蛋白质、有机物降解率的研究

本试验采用纤维素酶——胃蛋白酶复合处理法和胃蛋白酶——纤维素酶复合处理法,分别测定了鹿的12种常用饲料的蛋白质降解率和9种常用饲料的有机物消化率:并与尼龙袋法进行了比较,肯定了酶水解法估测尼龙袋法评定鹿饲料营养价值的可行性。试验结果表明,纤维素酶——胃蛋白酶法测定的饲料蛋白质降解率也符合数学模型p=a+b(1-e~(-ct)),但与尼龙袋法相比,a值偏高,二者在2小时短时间点相关不显著,但在24小时点相关显著(P<0.05):尼龙袋法(x)与酶水解法(y)的回归方程为y=23.08+0.7774x(n=9,r=0.9055,RSD=2.43)。在k=0.02～0.12范围内,酶水解法与尼龙袋法相关显著(P<0.05),其中酶水解法(y)在k=0.08时,与尼龙袋法(x)在k=0.02时相关极显著,其回归方程为y=24.59+0.77x(n=12,r=0.7306,RSD=6.78)。胃蛋白酶——纤维素酶法测得的有机物消化率(x)与尼龙袋法(y)相关显著(P<0.05),其回归方程为y=12.25+0.7088x(n=9,r=0.9350,RSD=0.97)。     

Protein, energy and dry matter consumption by racing thoroughbreds: A field survey

A field survey involving 109 horses in 9 stables at a Detroit racetrack was conducted to determine feeding practices and to estimate crude protein (CP), digestible energy (DE), and dry matter (DM) consumption by racing Thoroughbreds, and to compare those intakes with 1989 recommendations of the National Research Council (NRC), "Nutrient Requirements of Horses." Trainers were interviewed regarding: 1) the age and sex of the homes; 2) their feeding practices; and 3) the horse's training and racing schedule. Only adult homes who were actively racing and continuously stabled at the track were included. Body weights (BW) were estimated using a chest girth measurement. The horses had an overall mean body condition score of 5 which indicated average body condition for a racing. Thoroughbred at this track. Feed samples of hay and concentrate from each stable were weighed and analyzed at a commercial laboratory to determine CP, DM, acid detergent fiber (ADF), and estimated energy density. A computer program calculated CP, DE, and DM values for each horse's ration based onamounts fed. The software program included with the 1989 NRC publication was used to compare estimated nutrient intakes with current NRC recommendations for a horse of a given BW. Trainers fed a variety of hays. Eight trainers fed oats and only one fed corn. All trainers fed commercial sweet feeds. The mean total amount of feed for all homes on an "as fed" basis was 13.7 kg. The mean estimated DM intake for all horses was 12.3 kg vs. NRC recommended 11.6 kg. The mean for percentage of roughage in the ration for all stables was 53% vs. a NRC recommendation of 35%. The mean CP% ona DM basis for all stables' rations was 13.8% vs. a NRC recommendation of 11.4%. The means for actual CP and DE intakes for all horses were 1678 g and 33.3 Meal compared with current NRC recommendations of 1324 g CP and 33.1 Meal DE. Protein amounts were above those recommended due to the common practice of feeding relatively higher CP% in the rations than necessary for racehorse performance. These data appear to be more consistent with the recommendations of NRC in 1989 than previous recommendations in 1978.     

Effects of coextrusion of flaxseed and field pea on the digestibility of energy, ether extract, fatty acids, protein, and amino acids in grower-finisher pigs

The objectives of this study were to determine the ileal and total tract digestibility of individual fatty acids, ether extract, energy, protein, and AA in a mix of flax and field pea (FP) and to determine whether extrusion improves the nutritive value of this mix. Five barrows (23-kg initial BW) fitted with a T-cannula at the distal ileum were fed 5 diets at 3 times the maintenance energy requirement according to a 5 x 5 Latin square design: a wheat and soybean meal control diet and 4 diets containing 30% raw or coextruded FP plus 70% control diet and chromic oxide as an indigestible marker. The 4 extrusion treatments included the following: 1) FP0, ground, nonextruded; 2) FP1, single-screw extruded; 3) FP2, twin-screw extruded with low intensity (screw speed 120 rpm; die temperature 110 degrees C; water input 5 kg/h); and 4) FP3, twin-screw extruded with high intensity (300 rpm; 125 degrees C; 11 kg/h). The ether extract concentration was 17.8, 19.6, 17.7, and 17.3% (as fed) in FP0, FP1, FP2, and FP4, respectively. The ADF concentration was 13.2, 11.1, 11.4, and 13.7% (as fed) in FP0, FP1, FP2, and FP4, respectively. After a 7-d acclimation, feces were collected for 2 d, and then ileal digesta was collected for 2 d. Energy digestibility in the test ingredients was calculated using the difference method. Extrusion of FP did not affect the apparent total tract digestibility (ATTD) and apparent ileal digestibility (AID) of DM, OM, and CP for grower-finisher pigs. Extrusion increased (P < 0.05) the ATTD of GE and ether extract and the DE content of FP, and the AID of the Arg, Ile, Leu, Lys, Phe, Thr, and Val, and total fatty acids. Extrusion tended to increase (P < 0.10) the AID of linolenic acid. Single-screw extrusion resulted in a greater (P < 0.05) ATTD of GE, OM, ether extract, and DE content of FP and AID of SFA than twin-screw extrusion. Single-screw extrusion resulted in a trend for greater (P < 0.10) AID of linolenic acid and total fatty acids than twin-screw extrusion. Twin-screw extrusion at high intensity resulted in less (P < 0.05) AID of SFA than twin-screw extrusion at low intensity, indicating that equipment and conditions should be carefully controlled for the extrusion of FP. In conclusion, coextrusion of FP increased digestibility of ether extract, fatty acids, energy, and AA.     

Evaluation of a dynamic in vitro model to simulate the porcine ileal digestion of diets differing in carbohydrate composition

The aim of the study was to assess the ability of a dynamic in vitro model to determine the digestibility of OM, CP, and starch compared with a validated, static, in vitro method and in vivo ileal digestibility obtained from growing pigs fitted with a T-cannula. Five experimental diets with different carbohydrate types and level were assessed: a standard corn-based diet (ST) or the same diet with coarse ground corn (CC), 8% sugar beet pulp (BP), 10% wheat bran (WB), or 8% sugar beet pulp and 10% wheat bran (HF). In the in vivo experiment, diets CC and HF reduced (P = 0.015) ileal digestibility of OM compared with the ST diet. The inclusion of sugar beet pulp reduced (P = 0.049) ileal CP digestibility of the BP diet. This reduction was not statistically significant when sugar beet pulp was combined with the wheat bran in the HF diet. No differences were shown for in vivo starch digestibility among diets. With the static in vitro method, the OM disappearance was greater than that observed in the in vivo experiment. In this static method, the BP and HF diets reduced (P = 0.004 and < 0.001, respectively) the disappearance of the OM compared with the ST diet. The coarse grinding of corn did not alter OM digestibility but decreased (P = 0.005) the starch digestibility. The R(2) between the in vivo results and the static in vitro methods for OM and starch digestibility was 0.99 when the CC diet was not considered. The dynamic in vitro model yielded OM and CP digestibility coefficients comparable with those obtained in vivo for the ST and CC diets. However, the values were considerably affected by the incorporation of the fibrous ingredients. Diets BP, WB, and HF had decreased (P = 0.009, 0.058, and 0.004, respectively) OM digestibility compared with the ST diet. Protein digestibility was also decreased (P < 0.001, P = 0.019, and P = 0.003, respectively) with the BP, WB, and HF diets compared with the ST diet. However, digestibility was decreased to a greater extent in the BP diet than in the WB and HF diets, both of which contained wheat bran. The R(2) between the dynamic in vitro model and the in vivo results for CP digestibility was 0.99 when the CC diet was not considered. No differences were detected for starch digestibility among the diets with the dynamic in vitro model. This dynamic in vitro model yielded ileal digestibility results comparable with those obtained in vivo for CP and OM with a corn-soybean diet, or with a diet including coarse corn, but it underestimated digestibility when fibrous ingredients were included in the diet.     

Nutrient digestibility of extruded canola meal in ileal-cannulated growing pigs and effects of its feeding on diet nutrient digestibility and growth performance in weaned pigs

Canola meal (CM) contains less crude protein (CP) and more fiber and anti-nutritional factors such as glucosinolates than soybean meal (SBM) and consequently has a lower nutrient digestibility. Therefore, processing strategies that may increase the feeding value of CM warrant study. In two experiments, the effects of extrusion of Brassica napus CM on apparent (AID) and standardized ileal digestibility (SID) of amino acids (AA), apparent total tract digestibility (ATTD) of gross energy (GE) in growing pigs, and growth performance and diet digestibility in weaned pigs were assessed. Solvent-extracted CM was extruded using a single-screw extruder at three screw speeds: 250 (CM-250), 350 (CM-350), or 450 (CM-450) rpm. In exp. 1, in a double 4 × 4 Latin square, eight ileal-cannulated barrows (initial body weight [BW], 68.1 kg) were fed corn starch-based diets containing 50% CM or extruded CM. The CM sample contained 43.2% CP, 33.2% total dietary fiber (TDF), and 8.9 µmol of total glucosinolates/g on a dry matter (DM) basis. Extrusion increased (P < 0.05) the AID of CP, reduced (P < 0.05) apparent hindgut fermentation of CP, and decreased (P < 0.05) predicted net energy (NE) value of diets. Extrusion increased diet AID and CM SID of most indispensable AA by 3.1 to 5.3%-units. In exp. 2, 200 weaned pigs (initial BW, 8.3 kg) were fed diets containing 20% SBM, CM, or extruded CM starting 2 wk postweaning for 3 wk. The CM sample contained 42.7% CP, 28.3% TDF, and 5.3 µmol total glucosinolates/g DM. Wheat-based diets provided 2.3 Mcal NE/kg and 5.1 g SID Lys/Mcal NE. Dietary inclusion of extruded CM replacing SBM decreased (P < 0.05) diet ATTD of DM, GE and CP, and DE value. Average daily feed intake, average daily gain (ADG), and gain:feed (G:F) of pigs did not differ between extruded CM and SBM diets and were not affected by extrusion, but increasing extruder screw speed linearly increased (P < 0.05) ADG for day 1 to 7 and G:F for the entire trial. In conclusion, extrusion increased diet AID and CM SID of AA but not DE and predicted NE values of CM. However, increasing extruder speed did not further increase the SID of most of the AA of CM in growing pigs. Dietary inclusion of 20% CM or extruded CM did not affect the growth performance in weaned pigs.     

Effect of linseed cake supplementation on digestibility and faecal and haematological parameters in dogs

The experiment was conducted with a 6 x 4 cyclic changeover design. Six adult Alaskan huskies were assigned to diets containing 0%, 2%, 4%, 6% and 8% linseed cake. A linear decrease in the apparent digestibilities of organic matter (OM) (p < 0.020), ether extract (EE) (p < 0.003), neutral detergent fibre (p < 0.015), nitrogen-free extract (NFE) (p < 0.001) and crude carbohydrates (p < 0.001) was noted. Digestibilities of dry matter (DM) and crude protein (CP) were unaffected by the treatment. Wet weight of faeces increased (p < 0.001) and DM of faeces decreased (p < 0.001) linearly as the percentage of dietary linseed cake increased. Serum cholesterol concentration tended to decrease (p = 0.094) as the proportion of linseed cake increased. Apparent OM, EE, CP and NFE digestibility coefficients for linseed cake were 52%, 77%, 54% and 37%, respectively, and the digestible energy (DE) value was 13.22 MJ/kg DM. Our results showed that working and racing dogs fed the extruded and kibbled diet can utilize up to 4.2% linseed cake of diet DM as a fibre source without severe reductions in nutrient digestibility or feed consumption. Even higher levels of linseed cake, up to 8.5% of diet DM, can be used for normal or obese dogs, but more faeces will be excreted.     

Rotational and continuous grazing of sheep in the Inner Mongolian steppe of China

The aim of this study was to compare the effects of rotational and continuous grazing on herbage mass (HM), organic matter digestibility (dOM) and intake (OMI) and live weight gain (LWG) of sheep grazing on the inner Mongolian steppe, China at a stocking rate of 4.5 sheep/ha during the growing season. In the years 2005 and 2006, four 2-ha plots were used of which two were divided into four 0.5 ha paddocks each for rotational grazing, where sheep were moved each 10 days to the next paddock. The dOM was estimated from faecal crude protein concentration and OMI by oral administration of titanium dioxide. Herbage mass was similar in both grazing systems and dOM and OMI were higher (p < 0.05) at continuous grazing than at rotational grazing, but LWG did not differ probably because of extra energy expenditure for grazing and walking in a larger area. The dOM and OMI decreased (p < 0.05) with progress of the growing season and differed between years. Since precipitation during the growing season in both years was lower than the 30 years average which was probably the reason that positive effects of non-grazing periods on herbage regrowth and quality at rotational grazing could not occur, further studies are required in years with average precipitations before a final evaluation of these grazing systems can be made. Moreover, it seems necessary to quantify energy expenditure for physical activity of animals in grazing studies.