Effect of maize starch concentration in the diet on starch and cell wall digestion in the dairy cow

An in vivo experiment was performed to determine the effect of level of maize starch in the diet on digestion and site of digestion of organic matter, starch and neutral detergent fibre (NDF). In a repeated change‐over design experiment, three cows fitted with a rumen cannula and T‐piece cannulae in duodenum and ileum received a low‐starch (12% of ration dry matter) and a high‐starch (33% of ration dry matter) diet. Starch level was increased by exchanging dried sugar beet pulp by ground maize. After a 2‐week adaptation period, feed intake, rumen fermentation parameters (in vivo and in situ), intestinal flows, faecal excretion of organic matter, starch and NDF were estimated. When the high‐starch diet was fed, dry matter intake was higher (19.0 kg/day vs. 17.8 kg/day), and total tract digestibility of organic matter, starch and NDF was lower when the low‐starch diet was fed. Maize starch concentration had no significant effect on rumen pH and volatile fatty acid concentration nor on the site of digestion of organic matter and starch and rate of passage of ytterbium‐labelled forage. On the high‐starch diet, an extra 1.3 kg of maize starch was supplied at the duodenum in relation to the low‐starch diet, but only an extra 0.3 kg of starch was digested in the small intestine. Digestion of NDF was only apparent in the rumen and was lower on the high‐starch diet than on the low‐starch diet, mainly attributed to the reduction in sugar beet pulp in the high‐starch diet. It was concluded that without the correction for the reduction in NDF digestion in the rumen, the extra supply of glucogenic (glucose and propionic acid) and ketogenic nutrients (acetic and butyric acid) by supplemented starch will be overestimated. The mechanisms responsible for these effects need to be addressed in feed evaluation.     

Site and extent of starch degradation in the dairy cow - a comparison between in vivo, in situ and in vitro measurements

Prediction of the supply of glycogenic precursors to dairy cows and the site of degradation of wheat, maize and potato starch (PS) were determined in an in vivo experiment and the results were compared with data obtained from experiments involving in situ nylon bag and in vitro gas production techniques. In a Latin square design experiment four lactating dairy cows fitted with a rumen cannula and T-piece cannulae in the duodenum and terminal ileum, received either a low-starch control diet or diets in which sugar beet pulp in the concentrate mixture had been replaced by wheat, maize or PS. Starch from the different sources was almost completely degraded in the total gastrointestinal tract. For all starches, the rumen was the main site of degradation in vivo. No digestion of PS in the small intestine was observed. In situ results suggested that 14% of wheat starch (WS), 47% of maize starch and 34% of PS escaped rumen fermentation. According to the gas production technique WS ferments quickest and potato slowest. PS had a low degradability during the first 8 (gas production) to 11 (in situ) h. However, according to both in vitro and in vivo measurements rumen degradability of PS was high. The results suggest that in situ and in vitro techniques should be performed in animals that have adapted to starch source to provide a more accurate simulation of the in vivo situation.     

Partially replacing cornstarch in a high-concentrate diet with sucrose inhibited the ruminal trans-10 biohydrogenation pathway in vitro by changing populations of specific bacteria

Background: The positive influence of replacing dietary starch with sugar on milk fat production has been proposed to be partially attributed to the inhibition of the rumen trans-10 biohydrogenation pathway. However,whether and how sucrose inhibits the rumen trans-10 biohydrogenation pathway remains elusive.Results: A batch in vitro incubation system was used to evaluate effects of replacing cornstarch in a high-concentrate diet(forage to concentrate ratio = 40:60) with 0(control), 3, 6 and 9 % of sucrose on rumen fermentation pattern, fatty acid(FA) biohydrogenation pathways and bacterial populations relating to trans-11 to trans-10 biohydrogenation pathways. Replacing dietary cornstarch with sucrose did not alter rumen p H or concentrations of total volatile fatty acids(VFA) in comparison with the control but significantly influenced the profiles of individual VFA. The molar proportions of butyrate and valerate were linearly increased, while that of acetate was quadratically decreased and those of propionate, isobutyrate and isovalerate were linearly decreased with increasing concentrations of sucrose in the diet. Furthermore, replacing cornstarch with sucrose led to a linear decrease in C18:1 trans-10, linear increases in the proportions of C18:1 trans-11, C18:2n-6 and the ratio of trans-11 to trans-10, and linear decreases in biohydrogenation of C18:2n-6 and C18:3n-3. The abundance of Butyrivibrio fibrisolvens, a butyrate and CLA cis-9,trans-11 producer, was increased with the increasing inclusion of sucrose in the diet, while the population of Megasphaera elsdenii, a CLA trans-10, cis-12 producer, was significantly decreased by all levels of sucrose replacements.Conclusions: These results indicate that replacing starch in a high-concentrate diet with sucrose increased butyrate production and inhibited the rumen trans-10 biohydrogenation pathway, which was at least partially due to increased abundance of Butyrivibrio fibrisolvens and decreased abundance of Megasphaera elsdenii.     

甜菜粕颗粒对泌乳奶牛泌乳性能、血液生化指标的影响

本试验旨在研究甜菜粕颗粒对泌乳奶牛生产性能、血液生化指标的影响。采用完全随机试验设计,选择体重、泌乳天数(135.96±25.98)d、胎次(1~2次)、产乳量(29.78±5.42)kg和生理状态相近的48头中国荷斯坦奶牛,随机分为4组,每组12头。对照组饲喂基础日粮,试验组分别以3.5%、5.5%、7.5%甜菜粕颗粒(干物质基础)替换基础日粮中部分玉米和燕麦草等。试验预试期1周,正试期6周。结果表明:对照组的干物质采食量、产奶量以及乳成分与试验组无显著性差异;与对照组相比,3.5%、5.5%、7.5%甜菜粕组血清中总蛋白含量分别提高了13.75%、13.34%、8.17%(P<0.05);3.5%和5.5%试验组的球蛋白含量分别提高了18.02%、18.35%(P<0.05);5.5%试验组葡萄糖含量降低了17.76%(P<0.05);7.5%试验组每天可盈利1.28元/头。在本试验条件下,添加7.5%甜菜粕颗粒不会对机体的糖分吸收以及代谢造成影响且经济效益最佳。     

Analytical approach and effects of condensed tannins in carob pods (Ceratonia siliqua) on feed intake,digestive and metabolic responses of kids

There are contradicting data in the literature regarding condensed tannins content in carobs. In this study, urea (0.5 g/ml) under reflux conditions increased dramatically the yield of condensed tannins to 17% of dry matter, as compared to 3.5% in acidic methanol extraction. This shows that carob pods are rich source of nonextractable condensed tannins. The effect of PEG in diet rich in carob pods on voluntary feed intake, digestibility and growth in weaning kids was studied during 15 days of balance trials in 24 kids distributed into three dietary treatments. The corn grain and wheat bran components in the control diet (diet 1) were replaced by carob in treatments 2 and 3; treatment 3 was supplemented by 3.3% of PEG of molecular weight-4000. Food intake, diet utilization and growth rate of weaning kids fed a diet containing 52% carob pods were decreased considerably in comparison to kids fed the control commercial diet. Supplementing the kids fed the carob-based diet with PEG increased feed intake, crude protein digestibility and growth to the rate obtained with the control diet. The nutritional experiment highlights the following aspects relevant to all mammals consuming carob pods rich diets: (i) tannins increased the variability in feed intake between days, (ii) hypocholesterolemic effect of carob pods is related to lipid binding capacity of nonextractable condensed tannins in the digestive tract, (iii) supplementing high level of carob pods to animals with normal blood cholesterol level may induce hypocholesterolemia.     

Insoluble fibres,satiety and food intake in cats fed kibble diets

Fibre is generally considered to dilute food energy, alter intestinal transit time and promote satiety; however, in cats, conflicting results have been found. In this study, two insoluble fibres were evaluated in four feline diets: control (no added fibre); diet with 10% sugar cane fibre; diet with 20% sugar cane fibre; and diet with 10% cellulose. The experiment was conducted with 32 cats, eight animals per diet, over 42 days: 1–7 for diet adaptation; 8–14 for total collection of faeces for digestibility; 15–17 for fresh faeces collection for fermentation products measurements; 18–20 for gastrointestinal transit time determination; 21 and 37 to evaluate the pattern of food intake; and 22 and 42 to assess satiety. Means were compared by analysis of variance and orthogonal contrasts, and the pattern of food intake was compared by repeated‐measures analysis of variance (p < 0.05). The cats exhibited increased food intake after fibre addition to the diets (p < 0.05), achieving similar energy consumption. Cellulose and the two levels of sugar cane fibre reduced nutrient availability and energy digestibility, but only sugar cane fibre reduced fat digestibility (p < 0.05). Faecal output and the number of defecations per day increased with fibre inclusion (p < 0.05). Gastrointestinal transit time did not change with sugar cane fibre inclusion, but it was reduced with cellulose addition (p = 0.032). The pattern of food intake did not change, but cats fed fibre‐supplemented diets exhibited greater consumption of a challenge meal, increasing energy intake (p < 0.01) when exposed to a palatable, energy‐dense food.     

Effect dietary corn starch intake on pancreatic amylase and intestinal maltase and pH in cattle

The pH optimum of pancreatic alpha-amylase from grain-fed steers was determined to be 6.9, while that of intestinal maltase was established at 5.8. Both assays were found to be linear up to 1 hr of incubation. The V max of pancreatic amylase was determined to be pancreatic amylase was determined to be 1.15 mg of maltose monohydrate produced/hr. Activities of pancreatic and intestinal maltase were not reduced (P greater than .05) during the interval from sample collection from the animal until analysis 4 hr later when tissues were kept on ice. Twenty-four yearling Holstein steers fed either alfalfa hay at a maintenance level of metabolizable energy (ME) intake or corn at one, two or three times the maintenance ME intake level were slaughtered after being fed 106 days. The pancreas was removed alone with sections of the intestine. Specific activity of pancreatic amylase for steers fed the high level of corn was 129% of that for steers fed the alfalfa diet (P greater than .05). Intestinal maltase activity was highest in the jejunum and decreased toward the ileum. Increasing dietary starch intake resulted in no response (P greater than .05) in maltase activity at 10, 30, 50, 70, or 90% of the small intestine length. The effect of dietary starch level on dieesta pH was dependent on sampling location within the small intestine. There were no dietary effects (P greater than .05) on digesta pH for the first 10% segment of intestine distal to the pylorus. However, in all subsequent sections, digesta pH was higher steers fed the alfalfa diet than for those fed the two higher levels of grain. A calculation for estimating th amount of pancreatic amylase needed to hydrolyze starch presented to small intestine is discussed.     

γ-氨基丁酸对猪生产性能及激素水平影响

为探讨日粮中添加γ-氨基丁酸对猪的促生长效果及其与生长、摄食及代谢相关激素之间的联系。试验选用(34.07±0.01)kg的杜长大三元杂交猪60头,随机分到3个处理中,每个处理4个重复,每个重复5头猪。试验采用单因子设计,按日粮添加水平设基础日粮组(0 mg/kgγ-氨基丁酸)、基础日粮 50 mg/kgγ-氨基丁酸和基础日粮 100 mg/kgγ-氨基丁酸3个处理,试验期28 d。结果表明,γ-氨基丁酸对猪的促生长作用明显,但随生长阶段和作用剂量不同存在一定差异,主要体现在试验3~4周,以100 mg/kg的效果较为突出。100 mg/kg组试验猪第3周(P<0.1)、第4周(P<0.05)及0~4周(P<0.1)的ADG和第4周(P<0.01)、3~4周(P<0.1)的ADFI以及0~4周(P<0.05)的F/G都明显超过对照组。日粮中添加γ-氨基丁酸显著促进了试验猪体内生长激素(P<0.05)和褪黑素(P<0.05)的分泌,明显提高了小猪体内促甲状腺激素水平(P<0.1),这也与良好的生产性能吻合,但作用程度随试验阶段和激素种类不同而存在一定差别。总的看来,日粮中添加γ-氨基丁酸能够有效改善小猪生产性能,促进生长,但为获得理想结果必须考虑添加剂量与使用时间。     

Influence of sodium bicarbonate and magnesium oxide on digestion and metabolism in yearling beef steers abruptly changed from high forage to high energy diets

Eight rumen-cannulated steers (initial wt 330kg) were adapted to a mixed alfalfa-grass hay diet for 30 d and abruptly changed to complete mixed diets of corn silage, snapped ear corn and a corn-based supplement to determine the effects of buffers on diet adaptation, digestion and ruminal metabolism. The diets contained: 1) no buffer, 2) .5% magnesium oxide (MgO), 3) 1.0% sodium bicarbonate (NaHCO3) and 4) .5% MgO and 1.0% NaHCO3, as a percentage of diet dry matter (DM). Digestion, metabolism and ruminal characteristics were measured in each of 2 wk immediately after the diet change. The animals were then adapted to the mixed alfalfa-grass hay diet, re-randomized and assigned to the four diets, thus four steers consumed each diet. Intakes and digestibilities of DM were generally greater for the diets containing buffers. The most notable differences were a greater DM intake with added NaHCO3 and an improved DM digestibility with added MgO. The higher DM digestibility with MgO was apparently related to improved neutral detergent fiber (NDF) and starch digestion. Fecal pH was significantly increased with MgO addition. Because of the greater intake and digestibilities, the amount of DM, NDF, and starch digested tended to be greater for the buffered diets. There were no diet X week interactions for intake and digestibilities, thus the responses observed existed during both wk 1 and 2 after the change in diets. In general, intake and digestibilities were greater in wk 2 than in wk 1 for all diets.(ABSTRACT TRUNCATED AT 250 WORDS)     

芒果不同生育时期果实糖分积累特征及相关代谢酶活性分析

以台农1号为试验材料,在生长过程中测定果实可溶性糖、淀粉含量和蔗糖相关代谢酶及淀粉酶活性,并分析糖组分与果实形态和糖组分与酶活性间的相关性。结果显示：（1）台农1号果实生长呈单“S”型曲线,完熟时纵横经和单果重净增长量分别为5.46 cm、11.45 cm和212.95 g,果实发育前期以积累淀粉为主,葡萄糖和果糖次之,果实完熟后淀粉迅速分解,蔗糖积累量增加,果实形态与可溶性糖含量均呈显著或极显著高度正相关关系。（2）果实中性转化酶和蔗糖合成酶活性较低且变化趋势平缓,酸性转化酶在整个生育时期较活跃,活性呈先增加后降低趋势,采收时活性最强,蔗糖磷酸合成酶在生育前期活性较低,采收时活性迅速增加后略有降低,淀粉酶先迅速升高后逐渐降低。（3）可溶性糖含量与酸性转化酶和蔗糖磷酸合成酶及蔗糖合成酶活性相关性较强,但淀粉与以上酶相关性弱,与淀粉酶活性呈显著正相关。综上,芒果生育前期以积累淀粉为主,成熟时淀粉逐渐分解,可溶性糖含量增加,酸性转化酶和蔗糖磷酸合成酶是糖积累的关键酶。     

Effects of different supplemental sugars and starch fed in combination with degradable intake protein on low-quality forage use by beef steers.

Twenty ruminally fistulated steers (Exp. 1, 448 kg and Exp. 2, 450 kg) were used in two consecutive randomized complete block experiments with five treatments in each experiment. The purpose was to evaluate the impact of feeding different supplemental sugars or starch in combination with supplemental degradable intake protein (DIP) on the utilization of low-quality tallgrass-prairie hay. In Exp. 1, steers were given ad libitum access to forage and, except for the negative control (NC), received a limited supply (insufficient to maximize forage use) of supplemental DIP (.031% BW/d, DM basis). In addition to the NC, this experiment included four supplementation treatments in which one of four carbohydrate (CHO) sources (starch, glucose, fructose, or sucrose) was fed at .30% BW of DM/d. In Exp. 2, the treatment structure was identical except that the supplemental DIP level (.122% BW, DM basis) was near the level needed to maximize forage use. Forage OM intake (FOMI) was not affected (P> or =.26) by supplementation in Exp. 1 but was increased (P = .05) in Exp. 2. However, no difference (P> or =.46) in FOMI occurred among CHO sources in either experiment. Total OM and digestible OM intakes were increased (P<.01) by supplementation in both experiments. In Exp. 1, no difference (P>.26) in OM digestion (OMD) occurred among treatments. In Exp. 2, supplementation increased (P<.01) OMD. Additionally, sugars yielded a higher (P = .04) OMD than starch, and the monosaccharides yielded a higher (P = .02) OMD than sucrose. In Exp. 1, NDF digestion (NDFD) was decreased (P = .02) by supplementation, but no differences (P> or =.21) occurred among CHO sources. In Exp. 2, NDFD was increased (P = .03) by supplementation. Additionally, sugars led to higher (P = .05) NDFD than starch, and the monosaccharides led to higher (P = .03) NDFD than sucrose. In both experiments, discernible patterns were observable with regard to the effects of supplementation and type of supplemental CHO on ruminal fermentation characteristics. In conclusion, even though some consistency in fermentation profiles for different carbohydrate sources was evident in both experiments, forage intake and digestion responses were not consistent across experiments. This raises the possibility that carbohydrate source may interact with the amount of supplemental DIP fed and, as such, deserves additional investigation.     

Effects of different types of dietary non-digestible carbohydrates on the physico-chemical properties and microbiota of proximal colon digesta of growing pigs

The effect of different types of fibre on the intestinal digesta and microbial diversity was evaluated in growing pigs. The animals were fed during forty-two days with one of four experimental diets including a control group, a diet enriched with resistant starch type I, by coarse ground corn, and other two diets containing sugar beet pulp (8%) and wheat bran (10%) (as sources of soluble and insoluble non-starch polysaccharides respectively). Body weight (BW) and average daily feed intake (ADFI) were assessed at day 7, 21 and 42. Luminal samples of digesta from proximal colon were collected to analyse water retention capacity (WRC), concentration of short-chain fatty acids (SCFA) and the microbial diversity. Overall, animals fed with higher amounts of non-digestible carbohydrates had lower ADFI and BW. Sugar beet pulp provoked an increase of WRC, a higher concentration of SCFA, and a more stable microbial diversity throughout the experimental period. On the other hand, animals fed with wheat bran presented a lower bacterial diversity.     

Semi‐synthetic diet versus diet using natural ingredients—Comparative study in female Golden Syrian hamsters

Semi‐synthetic diets (SSD) are recommended and are widely used to carry out experiments in rodents. However, in our experiments planned to carry out generation studies in female Golden Syrian hamsters using semi‐synthetic diets, it was observed that the hamsters did not conceive as a result of decreased food intake. In this paper, we present the effects of both semi‐synthetic diets and natural source diets (NSD) on food intake, body weight and reproductive performance of this species. Four‐week‐old female hamsters were equally divided into 3 groups and initially acclimatized for 2 weeks on natural chow diet (NCD). Thereafter, they were fed either control diet, high fat diet (HFD) or low protein diet (LPD) based on semi‐synthetic/natural source ingredients until 12 weeks. Daily food intake and weekly body weights were monitored. Hamsters were kept for mating for about 2 weeks from 10th week onwards, during which the pregnancy confirmation test was done using standard vaginal smear examination. In all the groups fed SSD, the food intake was very poor, hamsters lost body weight and did not conceive, thus preventing us from carrying out further experiments. Hamsters fed NCD/NSD ingested more than twice as much as hamsters fed SSD (7–8 g/day/hamster against 3 g/day/hamster on average respectively). Based on the results of the current research, we conclude that the routinely used semi‐synthetic diet is not suitable for carrying out studies in female hamsters. We suggest that scientists must also consider the unusual biological characteristics of a given species besides other biological factors. It is therefore critical to select appropriate biological models and diets that provide optimal sensitivity and specificity to accomplish the research objectives.     

Replacement of soybean meal with levels of inclusion of soya waste in the diet of growing goats

An experiment was conducted to investigate the effect of replacing soybean meal with soya waste at different levels on intake, digestibility and growth in goats. Eighteen male goat kids with initial body weight (BW) of 13.0 kg were distributed equally to three dietary groups. They were fed Napier grass (Pennisetum purpureum) and concentrate mixture, and each goat was assigned to an individual pen. Soybean meal in the concentrate mixture was replaced with soya waste at 0% (T1), 50% (T2) and 100% (T3) levels in respective dietary groups. These diets were isocaloric and isonitrogenous. Results showed that animals fed T3 diet exhibited higher Napier grass intake than those fed T1 or T2 diet. There was no influence on total intakes of dry matter (DM), organic matter (OM), crude protein (CP), metabolic BW, per cent BW and metabolisable energy by the dietary groups. However, there was an increasing trend on intake and digestibility of neutral detergent fibre (NDF) with increasing levels of soya waste in the diets. Animals fed T3 diet showed higher intake and digestibility of NDF than those fed T1 diet. There was no influence of the dietary groups on digestibilities of DM, OM and CP. Similarly, there was no effect of them on the final BW, total BW gain, daily BW gain, feed conversion ratio and feed cost. Soya waste can replace 100% soybean meal in diets for growing goats, because no change was observed in nutrient intake, digestibility and growth performance; inclusion of soya waste enhanced the intake and digestibility of NDF.

     

Ileal starch digestibility in growing broiler chickens fed on a wheat-based diet is improved by mash feeding, dilution with cellulose or whole wheat inclusion.

1. An experiment was conducted to study causes of low ileal starch digestibilities when broiler chickens were fed on wheat-based diets. Each of 5 cold-pelleted diets containing 771 g/kg DM wheat and one cold-pelleted diet containing 694 g/kg DM wheat were fed to 24 male broiler chickens in 8 cages from 10 to 21 d of age. 2. Feed intake and weight gain were significantly reduced when the wheat diet was crushed and fed in a mash form. 3. Ileal starch digestibility increased significantly from 0.79 to 0.95, 0.93 and 0.91, respectively, when the diet was crushed and fed in a mash form, was diluted with cellulose prior to pelleting, or when parts of the wheat were fed as whole grains. Correspondingly, random variation between individual birds was reduced. 4. These results indicate that an overload of wheat starch in the digestive tract may be the cause of poor digestibility for some broilers in a flock. Grinding of the wheat may also influence starch digestibility.     

苜蓿青贮对低质粗饲料条件下奶牛产奶性能的影响

选择1～3胎次泌乳中期的荷斯坦牛10头,配对分为2组:对照组和试验组,两组的混合精料组成相同,对照组粗饲料为豆秸、玉米秸、花生秧和玉米淀粉渣,试验组以10kg苜蓿青贮替代等量粗饲料,进行60d的饲养试验,以研究苜蓿青贮对低质粗饲料条件下奶牛产奶性能的影响。结果表明:(1)添加苜蓿青贮提高了供试奶牛体重(P0.01);(2)试验组各期采食量均高于对照组,且试验60d时差异达到了极显著水平(P0.01);(3)添加苜蓿青贮,提高了供试奶牛的产奶量和乳脂肪含量(P0.01,P0.05)。     

Effects of dietary essential oil components on growth performance,digestive enzymes and lipid metabolism in female broiler chickens

1. The present experiment was conducted to describe the effects of thymol, cinnamaldehyde and a commercial preparation of essential oil components (CRINA Poultry), in female broilers. Feed and water were provided for ad libitum consumption. 2. Feed intake, weight gain and feed:gain ratio were not different among the treatments. Water intake was significantly lowered by cinnamaldehyde. Relative liver weight (g/100 g of body weight) was highest in birds given thymol, but this was seen only at the age of 21 d and not at 40 d. Patterns of digestive enzymes in pancreatic tissue were similar for the 4 treatments. 3. Amylase activity in intestinal digesta was highest in chickens given CRINA Poultry for 21 d, but the effect had disappeared after 40 d. Ileal digestibility coefficients for starch and protein were high and identical for all treatments. 4. Fatty acid composition of diet was reflected in that of adipose tissue. Plasma lipid concentrations were not changed by any dietary treatment. 5. Thus, the present results show no effect of essential oil constituents on growth performance in female broiler chickens, but it cannot be excluded that positive effects would have been observed under less hygienic environmental conditions or when using a less digestible diet.     

Influence of rumen escape starch on pancreatic exocrine secretion of goats

The objective of the experiment was to evaluate the effect of rumen escape starch (RES), accomplished by altering dietary starch concentrations on pancreatic exocrine secretion of goats. Four goats (36.8 ± 3.2 kg) with common bile duct re‐entrant and duodenal catheters were used in a 4 × 4 Latin square. Goats were fed diets containing 20%, 30%, 40% and 50% starch. Periods consisted of 10 day adaptation followed by 3 day of sample collection. Juice was collected in 1‐h fractions continuously for 72 h. Total juice secreted was recorded, and 3% sub samples were retained to form a composite sample. The remaining fluid was returned to the duodenum. Juice composite samples were analyzed for activities of α‐amylase, trypsin, chymotrypsin and lipase. Secretion of pancreatic α‐amylase was lower (p < 0.05) when comparing lambs fed 20% starch diet with 30%, 40% and 50% starch diets. Lipase secretion was greater (p < 0.05) in lambs fed 40% starch diet compared with the other diets. Total secretion of juice, trypsin and chymotrypin was not affected (p > 0.05) by dietary starch concentration. Rumen escape starch increased with increasing dietary starch concentration (p < 0.05). Regression analysis showed that increasing RES results in a quadratic increase (p < 0.05) in pancreatic α‐amylase and lipase secretion, and the secretion of α‐amylase and lipase is maximum when RES is 113 and 83 g/day respectively. These results suggest that optimal RES for pancreatic secretion of α‐amylase and lipase is 80–110 g/day in adult goats.     

饲喂添加酶制剂的玉米青贮、稻草日粮对奶牛生产性能和经济效益的影响

将20头荷期坦牛随机分为2组，每组10头，试验组在精料中添加2kg／t复合酶和200g／t木聚糖酶，对照组不添加，两组粗料均为玉米青贮和稻草。结果显示，试验组对提高奶牛采食量和产奶量有一定效果，每千克奶饲料费比对照组减少0.3元。