The effect of supplemental methionine and inorganic sulphate on the ruminal digestion of grass silage in sheep

The effects of an intra-ruminal infusion of a mixture of methionine (7.0 g day^?1) and sodium sulphate (6.7 g day^?1) on the digestion of grass silage were examined in four sheep fitted with cannulas in the rumen and proximal duodenum. There were no significant (P>0.05) effects of the infusion on the ruminal digestion of OM, cellulose or N, or on the concentrations of total or individual VFA in the rumen fluid though the numbers of protozoa in the rumen were reduced (P<0.05). The amounts of total methionine or of bacterial nitrogen reaching the duodenum were not significantly (P>0.05) altered by the infusion and rates of bacterial synthesis were 21 and 23 g N kg^?1 OM (s.e.d. 3.7, P>0.05) apparently digested in the rumen for the control and infusion treatments respectively. The infusion resulted in a significant (P<0.01) increase of 21% in the amount of total long-chain fatty acids at the duodenum. This reflected an increased flow of all fatty acids of chain-length 14:0 and above though more than 80% the response was accounted for by the increased flow of 18:0 and 16:0 acids. It is concluded that the infused supplement stimulated the synthesis of microbial lipid in the rumen.     

The effect of dietary starch on the digestion by sheep of cell wall monosaccharide residues in maize silage

The digestibility of individual cell wall monosaccharide residues from maize silage (MS) and from maize silage + concentrate (MS+con) diets, was examined in sheep equipped with rumen and duodenal cannulas. Dry matter digestibility was 73.8 and 86.6% in the MS and MS+con treatments, respectively. The overall digestibility of cell walls (CW) and CW monosaccharide residues was not depressed in the MS+con treatment. The values for total CW, CW glucose, CW uronic acid and for total xylose were 68.3, 77.0, 71.6 and 65.2 for MS and 69.4, 80.3, 75.3 and 63.7 for MS+con, respectively. However, the digestion of CW and CW monosaccharide residues in the rumen of the MS+con sheep was reduced and the contribution of the lower tract to the digestion of the potentially digestible CW-sugar residues was in the range of 15 to 20%. Digestibility of the soluble uronic acid was adversely affected by the concentrate, its digestibility being reduced from 88.6% in the MS to 68.7% in the MS+con treatment. Based on compositional considerations, it is envisaged that the CW structural unit of the ensiled maize plant is made of cellulose fibres enveloped by a thin, poorly lignified and penetrable matrix. The degree of branching of the matrix polysaccharides is low compared with other forage plants. It is suggested that the above mentioned properties significantly contribute to the high quality of the ensiled maize plant.     

Effect of the size of hay particles on digestion in the sheep

Four sheep fitted with permanent rumen cannulae were used to study the digestion of a hay diet prepared, by grinding, in four forms differing in particle size. Each form of the diet was given at two levels of feeding, 1.1 and 2.4 times the energy requirement for maintenance of bodyweight. At each level, the digestibility of organic matter and of other constituents in the diet and the mean retention time of food residues in the alimentary tract decreased from the coarsest to the most finely ground form of hay. The digestibility of organic matter (D) was related to the mean particle size (in nm) in the diet (p) such that D = 57.5 + 16.97 p² (P < 0.001) at the low level of feeding and D = 51.5 + 23.75 p² (P < 0.001) at the high level. There were corresponding relationships for the mean retention time of food residues (R) such that R = 69.1 + 64.0p² (P < 0.01) and R = 49.6 + 50.2p² (P < 0.01). There were no marked variations with the form of the hay in the rate of digestion of hay in nylon bags, or cotton threads, suspended in the rumen or in the pH or concentrations of ammonia or total or individual short-chain fatty acids in the rumen fluid. It is suggested that changes in digestion associated with the provisions of forages in ground forms can be related to the size of particles in the ground food and the level at which it is fed.     

The effect of the physical form of the diet and the level of feeding on the digestion of dried grass by sheep

Intact and rumen cannulated sheep were used to study the digestion of an artificially dried grass offered either in a chopped or a ground and pelleted form at energy intakes ranging from 1–3.2 × the energy requirement for meantenance. In each form of the grass the digestibility of all dietary constituents was depressed at high levels of feeding and, excepting ether extract, was lower in the ground and pelleted grass than in the chopped grass. The digestibility of organic matter (DOM) varied with treatment from 70.7–82.7% and for each form of grass was related to the level of feeding (LF) such that DOMC = 83.1–1.01 LF (P < 0.05) and DOMG = 84.6–4.12 LF (P < 0.001). Corresponding relation-ships were observed between the mean retention time of food residues in the alimentary tract (MRT) and the level of feeding (LF) such that MRTC = 111.7–95.1 log LF (P < 0.001) and MRTG = 77.2–60.8 log LF (P < 0.001). Where animals were fed on ground and pelleted grass there were changes in rumen fermentation characterised by a lowered rumen pH and cellulolytic activity and by reduced concentrations of ammonia-N and total short-chain fatty acids in the rumen fluid. The percentage of acetic acid in the fermentation products was decreased and there were associated increases in the percentages of butyric acid and valeric acid. The results indicate that grinding and pelleting the grass was associated with a reduction in the digestibility of organic matter resulting partly from an increased rate of flow of digesta through the alimentary tract and partly from a reduction in cellulolytic activity in the rumen.     

Rumen ciliate protozoa: effects on digestion in the stomach of sheep

Six wethers, each fitted with a rumen cannula and duodenal reentrant cannula, were used to study effects of ciliate protozoa on rumen digestion and metabolism. A corn: corn silage (1:1) diet was fed for two periods. During the first period, defaunation was attempted with nonyl phenol ethylene oxide. Defaunation was complete in three sheep and partial in the other three sheep in which a reduced population of a small Entodinium sp. was observed. During the second period the sheep were inoculated with ciliate protozoa, which established a large population in all animals. Apparent digestion in the stomach of organic matter and starch was higher when a large protozoal population was present. Amino acid flow through the duodenum was greater in defaunated animals. A large population of ciliates was associated with increases in both rumen ammonia and plasma urea but had a stabilizing effect on ruminal pH. Volatile fatty acids were higher in the defaunation period, but there were only small differences of molar proportions of the acids between the two periods. Effects of ciliate protozoa are related to animal performance.     

The digestion of the lipids of processed red clover herbage by sheep

Three mature wether sheep, equipped with re-entrant cannulae at the proximal duodenum and terminal ileum were fed either frozen, or dried and chopped or dried and ground red clover herbage, and samples of duodenal and ileal digesta and faeces were collected. Analysis of the feed and digesta samples for their individual long chain fatty acid content enabled the quantitative digestion of herbage lipids to be investigated. The flow of total fatty acids into the small intestine was greater than the amount daily consumed when the dried diets were fed, whilst on the frozen diet there was a net loss between mouth and duodenum (P<0.01). There was a marked increase in the proportion of saturated fatty acids in the fatty acid fraction collected at the duodenum relative to the feed on all diets, but some dietary differences were noted. The extent of hydrogenation was reduced on the ground diet and, to a lesser degree, on the chopped diet. Consequently these diets had significantly higher proportions of C18:1 in the duodenal fatty acid fraction than the frozen diet (ground, 22.5%; chopped 17.0, frozen 13.5;P<0.01). These changes influenced the quantity and composition of the fatty acid fraction absorbed from the small intestine; the ratio of unsaturated to saturated fatty acids absorbed (ground, 0.47; chopped, 0.32; frozen, 0.24) being significantly greater on the ground diet (P<0.01).     

The effects upon digestion in sheep of the dietary inclusion of additional salivary salts

Four mature Suffolk × half bred wether sheep, fitted with rumen fistula and re-entrant cannulae at the proximal duodenum and terminal ileum were given in sequence, a control diet (diet 1) and that diet supplemented with either 20 or 40 g saliva salt kg^?1 (diets 2 and 3 respectively). The addition of 20 g salt kg^?1 failed to alter significantly the rumen fermentation pattern and dilution rate. In contrast, the feeding of diet 3 resulted in a significant increase in the molar proportions of ruminal acetate, a non-significant decrease in propionate and a significantly higher rumen dilution rate (D), which was positively correlated with the molar proportions of acetate. Ruminal NH₃-N concentration tended to increase with salt supplementation, with the greatest concentration being observed at the highest level of salt inclusion. The presence of the salts significantly reduced the degradability of the feed protein within the reticulorumen. The dietary inclusion of the salts resulted in a non-significant increase in total amino acid N (TAA-N) and a significant increase in the organic matter entering the small intestine.     

The effect of starch on forage fiber digestion kinetics in vitro

Purified corn and wheat starch were added to alfalfa, Coastal bermudagrass, fescue, and orchardgrass hays at 0, 40, 60, and 80% of the total as-fed substrate, and fiber digestion kinetics were determined in vitro. Kinetics were estimated by the model R = Doe-k(t-L) + U where R is residue remaining at time t, Do is digestible fraction, k is digestion rate constant, L is discrete lag time, and U is indigestible fraction. Parameters of the model were estimated by logarithmic transformation and a direct nonlinear least squares procedure. Corn and wheat starch did not differ in their effect upon lag time of fiber digestion, digestion rate, or potential extent of digestion. Alfalfa had a shorter lag time of fiber digestion (.86 h) than Coastal bermudagrass (3.05 h), but not than orchardgrass or fescue (1.66 and 2.42 h). Orchardgrass differed in fiber digestion rate (.0542h-1) from Coastal bermudagrass (.0698h-1) but not from alfalfa or fescue (.0670 and .0658h-1). The potential extent of fiber digestion was similar for fescue (75.8%) and orchardgrass (76.0%). The potential extent of fibre digestion for alfalfa (50.9%) differed from Coastal bermudagrass (64.3%), and both of these forages differed from fescue or orchardgrass. Addition of starch resulted in a linear increase in lag time of fiber digestion, but digestion rate was not affected. Potential extent of digestion was decreased when starch was added.     

不同热处理条件下羊血浆蛋白体外模拟消化研究

目的 研究不同热处理条件下羊血浆蛋白的体外模拟消化特性及其蛋白质二级结构的变化规律。方法 采用胃蛋白酶对热处理后的羊血浆蛋白进行体外模拟消化,利用茚三酮法、十二烷基硫酸钠聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate polyacrylamide gel electrophoresis,SDS-PAGE）、表面电位（Zeta potential）及粒径、傅立叶变换红外光谱（Fourier Transform infrared spectroscopy,FTIR）等表征羊血浆蛋白的水解程度及消化产物的结构特性。结果 热处理可使羊血浆蛋白消化产物水解度增加,90℃热处理时水解度达到最大值,热处理可产生更多的低分子量组分,消化降解更为完全。90℃热处理时羊血浆蛋白消化产物的粒径分布单一,聚集程度最高。70~90℃热处理组的红外光谱显示酰胺Ⅰ带向低波数方向有不同程度红移,随着热处理程度的增加,羊血浆蛋白消化产物中α-螺旋结构含量先增加后减少,β-折叠结构含量总体降低。结论 热处理对羊血浆蛋白体外模拟消化均有一定的促进作用,从蛋白质变性的角度考虑,羊血浆蛋白的热处理强度不宜超过90℃ 20 min。     

乙基纤维素对油脂中维生素A体外消化释放速率的影响

以乙基纤维素EC100作为油脂质构剂添加到起酥油样品中,研究其控制性释放脂溶性维生素A的特性。体外模拟消化试验表明EC100具有显著的缓释作用,随着EC100质量分数的增加(0%~6%),起酥油样品消化2 h时VA的累积释放率由20.52%降低至3.62%。Ritger-Peppas方程式拟合得到维生素A溶出参数n为0.45~0.89,显示VA的释放速率受化合物自身扩散和骨架溶蚀双重控制。扩散系数的测定结果验证了VA的浓度梯度是扩散的驱动力,且随着油脂中EC100质量分数的增加(0%~6%),VA在有机凝胶剂中的扩散系数呈降低趋势;侵蚀试验结果表明,当贮藏时间越长、贮藏温度越低及EC100添加量越大时,有机凝胶剂样品的侵蚀常数降低,并且添加乳化剂分子蒸馏单甘酯(DMG)的有机凝胶样品受侵蚀的程度较小。     

Comparison of methods to describe the kinetics of digestion and passage of fibre in sheep

A mathematical model is described which was developed with the objective of analysing and interpreting data from rumen-emptying studies to estimate rates of digestion (k_d) and passage (k_p) in sheep offered hay once daily. It assumed that first-order kinetics applied to digestion in and passage from the rumen within a 24 h feeding cycle. The model predictions of k_d and k_p were compared with rates of digestion estimated by incubation of the hays in dacron bags and rates of passage determined using chromium-mordanted hay, in the same experiments. The predictions for rates of passage determined over the period 5–15 h postfeeding were lower than those determined from the chromium-mordant data and the simulations indicated that the fractional rate of passage during feeding was higher than that recorded in the postfeeding period. This suggests either that more than one fractional rate constant applies within a 24 h period, or that first-order kinetics do not apply. The estimates for k_d were considerably higher than those determined in dacron bags. Evaluation of the ability of the combined dacron bag and mordant techniques to estimate extent of digestion by comparison with in-vivo digestibility values indicated that the extent of digestion was underestimated. The predictions obtained from the rumen-emptying data were much closer to the in-vivo values.     

The effect of electrical stunning and slaughter on the electroencephalogram of sheep and calves

To study the application of electroencephalography (EEG) for the assessment of insensibility during stunning and slaughter, recordings were made on sheep that were slaughtered by throat cutting, electrically stunned head-only and allowed to recover, electrically stunned head-only followed by throat cutting or electrically stunned head-to-back. The same experiments were repeated on calves (1–6 weeks old) except some calves were stunned and allowed to recover before final stunning and throat cutting.

After the throat cut, sheep became insensible (i.e. EEG < 10 μV) at 8–22 s but the calf EEG did not fall below 10 μV until 79 s after the cut. With head-only stunning/recovery, high-amplitude EEG waves (electroplectic fit) continued for 47 s (sheep) and 33 s (calves) post stun. A quiescent period followed, which then developed into a period of moderate-amplitude EEG signals, so that, at 50 s post stun, the EEG usually exceeded 50 μV and often had bursts of 150 μV activity. After head-only stunning/throat cutting, the electroplectic fit was shortened (39 s in sheep, 23 s in calves) and the EEG took at least 50 s to fall below 10 μV. With sheep stunned head-to-back, which stops the heart, and thus should cause immediate, permanent insensibility, the EEG took longer to fall below 10 μV (52 s) than after throat cutting. These results suggest that electrical stunning of sheep and calves causes a prolonged increase in the post-stun EEG amplitude. Therefore, during slaughter, stunned animals have larger amplitude EEG signals than unstunned animals, and EEG criteria developed for judging the sensibility of unstunned animals cannot be used for those that are electrically stunned.     

The effect of alginates on in vitro gastric digestion of particulated whey protein

The aim of the study was to investigate how microparticulated and nanoparticulated whey proteins mixed with alginate respond to simulated in vitro gastric digestion conditions at pH 3.0. Initially, particle size distributions and zeta potential were measured in all mixtures at pH 3.0. Particle size distributions as well as SDS‐PAGE were used to investigate the rate of protein degradation by pepsin during simulated in vitro gastric digestion. The complexation of nanoparticulated and microparticulated whey protein with alginates causes formation of insoluble and soluble complexes, which can resist pepsin degradation to a different degree. These results highlight the potential of developing new food products, which can enhance satiety.     

The effect of harvesting strategy of grass silage on digestion and nutrient supply in dairy cows

This study examined the effects of primary growth (PG) and regrowth (RG) timothy-meadow fescue silages harvested at 2 stages of growth on feed intake, cell wall digestion and ruminal passage kinetics in lactating dairy cows. Four dairy cows equipped with rumen cannulas were used in a study designed as a 4 × 4 Latin square with 21-d periods. The experimental silages were offered ad libitum with 8 kg/d of concentrate. Ruminal digestion and passage kinetics were assessed by the rumen evacuation technique. Silages of PG were on average more digestible than RG silages. The concentration of neutral detergent fiber (NDF) and indigestible NDF (iNDF) increased and the concentration of digestible organic matter in dry matter (DM) of silages decreased with advancing maturity in PG and RG. Cows consumed more feed DM, energy, and protein and produced more milk when fed PG diets rather than RG diets. Delaying the harvest decreased DM intake and milk production in PG and RG. There were no differences between PG and RG in rumen pH, ammonia N, or total volatile fatty acid concentrations. The intake of N, omasal canal flow of total nonammonia N and microbial N, excretion of N in feces, and ruminal true digestibility of N were higher for PG than for RG diets. The efficiency of microbial N synthesis was not different between PG and RG. Intake and omasal canal flow of organic matter, NDF, and potentially digestible NDF (pdNDF) were higher in PG than in RG. Whole-diet digestibility of organic matter, NDF, or pdNDF in the rumen or in the total tract was not different between PG and RG despite the higher digestibility of PG silages measured in sheep. Rumen pool sizes of crude protein and iNDF were lower for PG diets, whereas the pool size of pdNDF was higher for PG diets than for RG diets. The rate of passage of iNDF was higher for PG diets than for RG diets, with no difference between them in rate of digestion or passage of pdNDF. The lower milk production in cows fed regrowth grass silages compared with primary growth silages could be attributed to the lower silage DM intake potential. Chemical composition of the silages, rumen fill, digestion and passage kinetics of NDF, or the ratio of protein to energy in absorbed nutrients could not explain the differences in DM intake between silages made from primary and regrowth grass.     

The effect of stage of maturity on the digestion of hemicelluloses of sorghum (Sorghum bicolor)

Sugar composition of hemicelluloses before and after in-vitro digestion of sorghum at different stages of maturity have been determined. Xylose was the main mono-saccharide residue and its content increased with maturity. It was also the least digestible sugar residue. Galactose and arabinose residue were highly digestible at all stages of maturity.     

The effect of saccharose on the growth and structure of bone tissue

The content of organic mineral components in bones was studied after substitution of 25 and 50% of carbohydrate energy value in rations for saccharose. It was established that saccharose stimulated the growth of experimental animals, this was attended by increased phosphomonoesterase-1 activity, epiphyseal cartilage thickening, hyperfunction of the growth zone and changes in the phosphorus-calcium metabolism.     

苦荞芽粉馒头体外消化后抗氧化能力研究

为研究苦荞芽粉馒头在人体消化、吸收过程中抗氧化能力的变化规律,模拟体外口腔、胃肠道消化吸收,通过比较不同梯度样品馒头总酚和总黄酮含量、DPPH·和ABTS+·的清除能力和抑制β-胡萝卜素褪色能力来比较苦荞芽粉馒头、苦荞馒头和小麦馒头体外消化吸收3个阶段的抗氧化性差异。各样品组的馒头在经过口腔消化之后,多酚和黄酮类物质逐渐释放,并在胃肠道消化之后达到最大值,但吸收率较低;苦荞芽粉馒头的胃肠道消化液和吸收液抗氧化性均显著高于相同比例添加量的苦荞和小麦馒头。馒头消化液的总酚和总黄酮含量与DPPH·、ABTS+·清除能力和抑制β-胡萝卜漂白能力呈正相关性,其中总酚与消化液抗氧化性极显著相关。苦荞芽粉馒头的胃肠道消化液和吸收液具有较强抗氧化活性,并优于相同梯度的苦荞原粉馒头和小麦馒头。研究为新型苦荞营养保健食品的开发提供依据。