Digesta Passage Research Articles

Effects of dietary fibre on digesta passage, nutrient digestibility, and gastrointestinal tract morphology in the granivorous Mongolian gerbil (Meriones unguiculatus).

To investigate digestive tract performance in Mongolian gerbils (Meriones unguiculatus), food intake and digestibility, digesta passage rate, and gastrointestinal tract morphology were measured in captive animals fed low- or high-fibre diets. We used two markers (Co-ethylene diamine tetra-acetic acid for solutes and Cr-mordanted cell walls for particles) to measure differential passage rates of digesta fractions in order to test for the presence of a colonic separation mechanism (CSM). Although dry-matter intakes on the high-fibre diet did not differ from those on the low-fibre diet, digestibilities of dry matter, neutral-detergent fibre, acid-detergent fibre, crude protein, and crude fat were all significantly lower on the high-fibre diet. Gross energy intake on the high-fibre diet also did not differ from that on the low-fibre diet, but energy lost in faeces was much higher than on the low-fibre diet; thus, energy digestibility and digestible energy intake were significantly lower on the high-fibre diet. The lengths and dry-tissue masses of all segments of the gastrointestinal tract tended to enlarge in response to increased dietary fibre, but only the total tract contents, contents of the small intestine, and length and dry-tissue mass of the caecum increased significantly. The mean retention time (MRT) of the particle marker was significantly greater than that of the solute marker on the low-fibre but not the high-fibre diet; the solute/particle differential retention ratio was 0.62 on the low-fibre diet and 0.90 on the high-fibre diet. Thus, there was no evidence for selective retention of the solute marker on either diet. The MRT of the particle marker was significantly lower on the high-fibre diet and in the same direction as the MRT of the solute marker. These results suggest that the granivorous Mongolian gerbil has no CSM but can adjust its digestive tract capacity to accommodate greater quantities of low-quality food.

Selective digesta retention and coprophagy in Brandt's vole (Microtus brandti).

Digestive performance, gut morphology and rate of digesta passage were measured in Brandt's voles (Microtus brandti) offered pelleted diets of low (25% neutral-detergent fibre) and high (38%) fibre content. Digestion coefficients of dry matter, crude fat, crude protein, energy and fibre were all significantly lower on the higher fibre diet. Although not significantly higher, dry matter intakes were more than maintained when extra cellulose was included in the diet, so that intakes of digestible energy were only 22% lower on the higher fibre diet. Total length and total gut tissue weight increased significantly, and the length and tissue weight of the caecum, proximal colon, and distal colon were significantly greater on the higher fibre diet as well. Total tract mean retention time (MRT) of a solute marker (Co-EDTA) was significantly greater than that of a particle marker (Cr-cell walls) on the lower fibre diet, and in the same direction on the higher fibre diet. The ratio of solute to particle MRTs (the solute/particle differential retention ratio) was 1.45 on the lower fibre diet and 1.19 on the higher fibre diet. There were no significant differences in marker MRTs between diets. Examination of marker concentrations in the stomach, small intestine, caecum and colon of voles killed at 0.5-h intervals after a pulse dose of Co-EDTA indicated that the marker was recycled to the stomach by coprophagy. Thus, as in other microtine rodents, an increase in gut capacity, selective digesta retention and recycling of digesta via coprophagy enables Brandt's voles to utilise diets of higher fibre content than may be expected for such a small (45 g) mammalian herbivore.

Use of tannin-binding chemicals to assay for tannins and their negative postingestive effects in ruminants

Synthetic polymers such as water-soluble polyvinyl pyrrolidone (PVP), water-insoluble polyvinyl polypyrrolidone (PVPP), and water-soluble polyethylene glycol (PEG) contain sufficient oxygen molecules in a chain to form strong hydrogen bonds with the phenolic and hydroxyl groups in tannins. This review deals with the practical uses of tannin-binding agents, particularly PEG, in tannins assays and for determining the negative effects of tannins on feed intake and digestion in ruminants. A gravimetric method to assay tannins by precipitation with PVPP is specific for tannins and does not require standards. The extractability of tannins from plant tissues can be reduced by drying samples at temperatures above 50°C and is dependent on many other factors, such as content and types of plant proteins. Therefore, it is not feasible to recommend a single, optimal protocol for all plant samples. A method to assay tannins which is based on measuring the amount of binding of PEG to plant samples was shown to be simple and accurate. It can also overcome some of these extractability problems. The following biological effects of tannins were investigated in studies where tannin anti-nutritional effects were partially or completely neutralised by varying levels of PEG supplementation. (1) Effects on appetite: the negative effects of tannins on appetite can occur in the short-term (within 20–60 min) and the long-term (days and weeks). Astringency and adverse postingestive influences of tannins on the epithelium of the oral cavity and the foregut cause short-term effects on food intake. Long-term effects can be related to reduction in the concentration of ammonia and volatile fatty acids (VFA) in rumen fluids, which can in turn serve as metabolic cues for deficiency of nitrogen (ammonia), energy (VFA), or both. (2) Effects on digestion: increasing content of tannins in foliage can be associated with an increase in bound protein and with reduced degradation rate of the degradable matter in the rumen, but there is no corresponding increase of the non-degradable fraction. Consequently, organic matter, protein, and cell wall digestibility are inversely related to tannin concentrations. (3) Inducing digestive responses: if a significant amount of tannins reach the duodenum, they may markedly reduce the intestinal activity of pancreatic enzymes (trypsin and amylase) and amino acids absorption from the intestine. Condensed tannins can also reduce the content of fluid and particulate matter in the rumen, accelerate the passage of liquid from the abomasum, and delay the passage of digesta in the intestine. The overall effect is a delay in the passage of fluid and particulate matter throughout the entire gastrointestinal tract. It is hypothesised that these responses are largely the consequence of the interaction of tannins with digestive enzymes and the epithelium lining the digestive tract.

Effect of polyethylene glycol on rumen volume and retention time of liquid and particulate matter along the digestive tract in goats fed tannin-rich carob leaves ( Ceratonia siliqua)

The present work studied the effects of tannins in carob leaves (CL) on rumen volume and kinetics, and on the retention time of fluid and particulate components of the digesta along the gastrointestinal tract (GIT) in goats. The experimental design was a two factor crossover experiment, i.e. in phase 1, two goats were fed CL and 2 CL and polyethylene glycol (PEG) and in phase 2, the treatments were switched. The main effects of tannins were depression of the rumen fluid and particulate content of the rumen, acceleration of the passage of liquid from the abomasum, and delay of the passage of digesta in the intestine. The overall effect was a delay in the passage of fluid and particulate matter throughout the entire GIT. It is hypothesised that these responses are largely the consequence of the interaction of tannins with digestive enzymes and the epithelium lining of the digestive tract.

Effect of Intake of Italian Ryegrass Hay on Chewing Behavior, Rumen Volume and Fecal Particle Size in Heifers

This experiment was designed to elucidate the relationships among intake, chewing behavior, digestibility, and the digesta passage through the rumen. Four Holstein heifers (average body weight, 455kg), each with a large ruminal cannula, were given Italian ryegrass hay at one of four intakes (2.44, 4.88, 7.33 and 9.49kg DM/day) in 4×4 Latin square design (12 days per period). Measurements were made for diet digestibility, chewing behavior, rumen volume, outflow rate of rumen fluid and fecal particle size distribution. The apparent digestibilities of the chemical components except crude fat and crude protein decreased with increasing intake. The apparent retention time of dry matter in the rumen was longest (P<0.05) at the intake of 2.44kg/day. However, the values had no significant differences among the higher intakes since rumen volume increased proportionally to the increase of intake. The percentage of fecal particles retained on sieves of 1 and 2mm opening size was significantly (P<0.05) higher in lower intakes (2.44 and 4.88kg/day). While eating time (min/kg DM intake) increased as intake increased, rumination time decreased slightly with the increase in intake. Thus, the total chewing time per unit of intake did not differ significantly among the intakes. The chewing rate during rumination and the total number of chews were higher for higher intake levels. From these results, it was considered that the depression of the digestibility at the higher intakes was influenced not only by the passage rate through the rumen but also partly by lower digestion rate in the post-ruminal digestive tracts. Moreover, under the maintenance level of intakes, the particle size that escapes from the rumen might be longer on account of the lower total chews for unitary intake and the longer particle size of feces.

Effect of dietary molasses on the site and extent of digestion of nutrients in sheep fed broiler litter

The aim of this experiment was to determine the site and extent of digestion of nutrients in sheep fed broiler litter alone (100% litter treatment), broiler litter plus 7.5% sugarcane molasses (92.5% litter treatment) and broiler litter plus 15% molasses (85% litter treatment). Voluntary intake was increased by molasses, apparently due to an increased rate of passage of digesta through the digestive tract. This resulted in a shift in the site of disappearance of organic matter (OM) from the rumen towards the lower digestive tract. For the 100 and 92.5% litter treatments, 0.37 and 0.46 of dietary OM disappeared in the rumen respectively, compared to 0.21 for the 85% litter treatment, while 0.16, 0.08 and 0.35 of dietary OM disappeared in the small intestine for the 100, 92.5 and 85% litter diets respectively. In the case of the 85% litter treatment, 0.26 of dietary nitrogen (N) disappeared in the rumen and 0.45 in the small intestine, compared to 0.55 and 0.62 in the rumen and 0.18 and 0.11 in the small intestine for the 100 and 92.5% litter diets respectively. There were no differences between treatments for total tract apparent digestibility of N (0.73) and OM (0.65-0.73), rumen degradability of N (71-87%) or concentration of ammonia-N in rumen fluid (53 mg/100 ml). It was concluded that the addition of molasses might be advantageous when the intake of litter is restricted or when voluntary intake of litter is unacceptably low. (South African Journal of Animal Science, 2001, 31(1): 33-40)

Síntese microbiana, pH e concentração de amônia ruminal e balanço de compostos nitrogenados, em novilhos F1 Limousin x Nelore

Os objetivos do experimento foram determinar os efeitos de cinco níveis de concentrados na dieta sobre a eficiência de síntese microbiana, as concentrações de amônia e os valores de pH ruminal, o balanço de compostos nitrogenados e a taxa de passagem da digesta pelo rúmen de novilhos F1 Limousin x Nelore. Utilizaram-se cinco animais fistulados no rúmen, abomaso e íleo, com peso médio de 279 kg, distribuídos em quadrado latino 5 x 5, alimentados à vontade com feno de capim-coastcross e porcentagens de 25,0; 37,5; 50,0; 62,5; e 75,0% de concentrado. Amostras de líquido de rúmen para determinação de amônia e pH foram obtidas antes e 2, 4, 6 e 8 horas após o arraçoamento dos animais. As bases purinas foram o indicador microbiano utilizado e as bactérias do rúmen foram isoladas por centrifugação diferencial. A taxa de passagem foi obtida com infusão de dose única de 20 g de óxido crômico e os tempos avaliados foram imediatamente antes da infusão do indicador e 3, 6, 9, 12, 24, 36 e 48 horas após. O fluxo de nitrogênio bacteriano (Nbact) no abomaso e a eficiência microbiana em relação aos carboidratos degradados no rúmen (CHODR) não foram influenciados pelos níveis de concentrado, observando-se valores médios de 85,69 g Nbact/dia, 41,09 g Nbact/kgCHODR e 472,44 g MSbact/kgCHODR. As concentrações máximas de amônia de 17,56 mg/100mL de fluido ruminal ocorreram 2,77 horas após a alimentação. O pH do rúmen diminuiu linearmente com os níveis de concentrados e foi influenciado de forma quadrática pelo tempo de coleta. Foram observadas taxas de passagem da digesta ruminal de 0,059; 0,053; 0,073; 0,068; e 0,041.h-1, para os respectivos níveis de 25,0; 37,5; 50,0; 62,5; e 75,0% de concentrado. O aumento do concentrado na dieta não alterou o crescimento microbiano no rúmen.

Comparison of Digestive Function Among Rabbits, Guinea-Pigs, Rats and Hamsters. I. Performance, Digestibility and Rate of Digesta Passage

Comparison of Digestive Function Among Rabbits, Guinea-Pigs, Rats and Hamsters. I. Performance, Digestibility and Rate of Digesta Passage

Feeding ground and pelleted hay rather than chopped hay to ponies: 1. Consequences for in vivo digestibility and rate of passage of digesta

This study was designed to evaluate the effect of the physical form of a hay diet on total tract digestibility in ponies, with particular emphasis in fibre digestion and digesta passage rate. Ten gelded ponies (four of them fitted with cannulae in the cecum and the right-ventral colon) were kept on wood shavings and fed twice daily a maintenance diet of equal parts Lucerne and Cocksfoot hay. The hay was either chopped (CH) or ground (1.5 mm screen) and pelleted (GPH). The apparent total tract digestibility of dry matter (DM), organic matter (OM), and fibre fractions was measured in the six non-fistulated ponies using a crossover design. Two trials were conducted to measure mean retention time (MRT) of digesta in the whole digestive tract in four non-fistulated and four fistulated animals using rare earth labelled hay and Cr-EDTA as markers of the particles and solutes, respectively. In a third trial, MRTs in the hind gut and the colon, as well as in the entire tract, were determined in the fistulated ponies using various markers given by mouth and through the cannulae. OM and fibre digestibility were not significantly different ( P>0.05) between diets. However, particle ( P<0.05) and solute ( P<0.001) MRT were significantly longer on GPH compared to CH as a consequence of an increased retention in the colon. The longer MRTs with GPH did not significantly affect fibre digestibility. This implies a reduction in the rate of fibre degradation in the hindgut in the GPH fed animals.

Composition of bacteria harvested from the liquid and solid fractions of the rumen of sheep as influenced by feed intake

A study was conducted to determine the effect of the feed intake on the chemical composition of bacteria associated with the solid (solid-associated bacteria; SAB) and liquid (liquid-associated bacteria; LAB) fractions of rumen digesta, the digestive passage kinetics and their relationships. Whole rumen contents were sampled after a period of continuous infusion of 15NH3 from four ruminally-cannulated wethers provided successively with a hay-concentrate diet (2 : 1 w/w on a DM basis) at two rates of feed intake: 40 and 80 g DM/kg body weight 0.75. SAB had a higher content of organic matter and total lipids (P < 0.001) and a similar N content as compared with LAB. The concentration of purines and 15N was lower (P = 0.011 and P < 0.001 respectively) in SAB than LAB, whereas the opposite was observed for the concentration of amino acids (mg/g DM; P = 0.031). An increase in feed intake produced an increase in the N (P = 0.034) and purine (P = 0.066) concentrations in bacteria and a decrease (P = 0.033) in their amino acid concentrations. Significant increases of rumen outflow rates of liquid and particles were also observed with increased feed intake. Rates of rumen outflow showed positive and negative linear relationships (P < 0.001) with the purine : N ratio and the proportion of amino acid on total N of bacteria respectively. SAB contained significantly higher proportions of leucine, isoleucine, lysine and phenylalanine and lower proportions of alanine, methionine and valine than LAB. The increase in feed intake also induced significant changes in the amino acid profile of bacteria, increasing arginine and methionine and decreasing alanine and glycine proportions. Results show that the outflow rate of rumen contents is a major factor in determining the proportion of nucleic acids and protein in rumen bacteria and explains some of the differences observed between LAB and SAB.

Nutritional Evaluation of Soybean Meals Varying in Oligosaccharide Content

Three conventional soybean meals (CSBM) and five low-oligosaccharide soybean meals (LOSBM) were evaluated. Meals were prepared by solvent-extracting flakes from generic soybean lines and soybean lines genetically modified to contain varying oligosaccharide content. The mean raffinose, stachyose, and galactinol levels in the CSBM were 0.58, 3.23, and 0%, respectively. The mean (range) raffinose, stachyose, and galactinol levels in the LOSBM were 0.08 (0.03 to 0.17%), 0.42 (0.04 to 1.08%), and 0.104 (0 to 0.24%), respectively. The crude fiber, fat, and ash contents of all SBM were similar, whereas the CP and sucrose contents of the LOSBM were slightly higher than the CSBM. The effect of SBM type on digesta passage rate, dry matter digestibility, and TMEN was assessed in conventional and cecectomized roosters using a precision-fed rooster assay (8 x 2 factorial design). Quantitative collection of excreta for 4, 8, 12, 16, 20, 24, and 48 h postfeeding indicated little or no effect of SBM type on digesta passage rate. The dry matter digestibility and TMEN values for the SBM were lower for cecectomized roosters compared with conventional roosters (P < 0.05), and there was no significant SBM x bird type interaction. The mean TMEN values (kcal/kg DM) for the CSBM and LOSBM were 2,739 and 2,931, respectively, which was a difference of 7% (P < 0.05). The two LOSBM with the lowest total raffinose, stachyose, and galactinol levels (0.07% and 0.25%) had average TMEN values that were 9.8% (P < 0.05) higher than their respective genetic controls. Digestibilities of raffinose and stachyose were much higher (P < 0.05) in conventional roosters than in cecectomized roosters. The results of this study indicated that the TMEN of LOSBM was higher than that of CSBM.

Coarse Brown Rice Increases Fecal and Large Bowel Short-Chain Fatty Acids and Starch but Lowers Calcium in the Large Bowel of Pigs

Young male pigs were fed a diet formulated from human foods including either boiled white rice plus rice bran or heat-stabilized brown rice at equivalent levels of fiber for 3 wk. Stool and starch excretion were low in pigs fed white rice during the first 2 wk of the experiment. In pigs fed brown rice, their excretion was high during wk 1 but declined in wk 2 while short-chain fatty acid (SCFA) excretion was higher at both times. Large bowel digesta mass, measured during wk 3, was higher in pigs fed brown rice but only in the proximal colon. Large bowel and fecal starch concentrations were higher in pigs fed brown rice but the difference was insufficient to explain the increase in large bowel digesta mass. In pigs with a cecal cannula, digesta starch concentrations were equally higher when white or brown rice was fed compared with the corresponding rice which had been finely milled, indicating that particle size was a determinant of ileal digestibility. Concentrations and pools of total and individual SCFA were higher in all regions of the colon but not the cecum of pigs fed brown rice. Large bowel Ca(2+) concentrations were lower in pigs fed brown rice, suggesting greater absorption. The data confirm earlier findings that brown rice raises large bowel digesta mass and SCFA through greater fermentation of starch but show that starch itself makes a relatively small contribution to digesta and stool mass. Apparently, the rate of passage of digesta is a determinant of the concentrations and pools of SCFA in the distal colon and in feces.

Simulação da dinâmica de nutrientes no trato gastrintestinal: aplicação e validação de um modelo matemático para bovinos a pasto

O objetivo do presente trabalho foi a validação das predições da dinâmica ruminal e pós-ruminal dos nutrientes e do crescimento microbiano no rúmen, usando as equações do sistema Cornell. O experimento foi realizado durante as estações chuvosa e seca do ano de 1996, em uma área de pastagem natural localizada no município de Viçosa (MG). Foram utilizados novilhos canulados no esôfago, rúmen e abomaso, durante dois períodos experimentais em cada estação, e usados indicadores externos (Cr2O3 e Eu) para estimativa do consumo e da taxa de passagem da digesta no rúmen. Foram determinados os fluxos de nitrogênio total e de nitrogênio bacteriano no abomaso, os carboidratos totais e estruturais digeridos no rúmen e os teores em nutrientes digeríveis totais. Estas variáveis também foram preditas a partir do modelo descrito no sistema Cornell, para validação de suas estimativas. Verificou-se que o modelo foi sensível às estimativas das taxas de passagem, superestimou (12,38%) o fluxo de nitrogênio bacteriano no abomaso e subestimou (70,64%) a disponibilidade ruminal dos carboidratos estruturais. O emprego da taxa de passagem de 0,02 h-1 no cálculo das estimativas resultou no aumento da superestimação do fluxo de N de origem bacteriana (28,66%), em virtude da maior degradação dos carboidratos estruturais, cuja estimativa permaneceu subestimada em 21,55%. A redução do consumo de matéria seca foi mais bem correlacionada aos teores de FDN indigerível que aos teores de FDN, devendo-se ressaltar que a capacidade diária de consumo desta fração foi de 0,6% do peso vivo e não diferiu entre estações.

Effect of vasoactive intestinal polypeptide and environmental temperature on forestomach electromyographic activity and gastrointestinal contraction in sheep

Four crossover design experiments were conducted with sheep to test the hypothesis that vasoactive intestinal polypeptide (VIP) affects gastrointestinal motility with implications for digesta flow. Sheep were shorn and surgically prepared with electrodes implanted on the forestomach, cannulae in the rumen, duodenum or/and ilieum, and a left gastric artery catheter. VIP (1 or 1.5 nmol min−1) or saline (control) was infused for 10 min at half-hour or hour intervals for 4 or 7 d during treatment periods. VIP transiently inhibited electromyographic (EMG) activity of the reticulum, reticulo-omasal orifice (ROO) and omasum for 3 to 8 min during the 10-min infusion periods. VIP infusion extended the duration of ROO opening (P &lt; 0.01). The gastrointestinal lumen pressure pattern was also transiently influenced by VIP, with an increase of quiescent time. Cold exposure of sheep stimulated a relatively higher motility in the ROO and omasum. The results indicate that the inhibitory effect of VIP on the reticulum, ROO and omasum electrical activity is transient; however, its action to extend the duration of opening of the ROO may facilitate digesta passage. Key words: Sheep, vasoactive intestinal polypeptide, electromyographic activity, reticulo-omasal orifice

Níveis de concentrado em dietas de novilhos mestiços F1 Simental x Nelore: 2. Balanço nitrogenado, eficiência microbiana e parâmetros ruminais

Foram avaliados os efeitos dos níveis de concentrado nas rações sobre a eficiência de síntese microbiana, o balanço de compostos nitrogenados, a concentração de amônia e o pH do fluido ruminal, a taxa de passagem da digesta ruminal e as perdas endógenas de compostos nitrogenados (N). Foram utilizados cinco novilhos F1 Simental x Nelore, não-castrados, fistulados no rúmen, abomaso e íleo, alimentados à vontade com dietas que continham 25,0; 37,5; 50,0; 62,5; e 75,0% de concentrado e distribuídos em delineamento quadrado latino 5x5. As concentrações de amônia e o pH ruminal foram determinados em amostras de fluido ruminal coletadas imediatamente antes do fornecimento das rações e 2; 4; 6; e 8 horas após. A taxa de passagem foi determinada pelo modelo unicompartimental, utilizando-se o óxido crômico como indicador. A eficiência de síntese microbiana, expressa em relação à matéria orgânica degradada no rúmen (MODR), aos carboidratos totais degradados no rúmen (CHODR) e ao NDT, foi influenciada quadraticamente pelos níveis de concentrado na dieta, estimando-se valores máximos de 41,22 gNmic/kg MODR, 39,89 gNmic/kg CHODR e 17,33g PBmic/100 g NDT, estimados para 52,16; 60,44; e 56,63% de concentrado na dieta, respectivamente. Quando expressa em MSmic/kg CHODR, a eficiência aumentou linearmente com o nível de concentrado. Foram estimados valores de 5,15 g N/kg MS ingerida para o nitrogênio metabólico fecal e 422 mg N/kg0,75 para as perdas endógenas totais. As concentrações máximas de amônia para todos os tratamentos ocorreram a 3,6 horas após o fornecimento da ração. As taxas de passagem de 0,052; 0,052; 0,055; 0,055; e 0,042.h-1 foram verificadas para os tratamentos com 25,0; 37,5; 50,0; 62,5; e 75,0% de concentrado, respectivamente. A máxima eficiência microbiana foi obtida entre 52 e 60% de concentrado.

Gastrointestinal transit times in young and old cats

Ageing results in a decrease in apparent nutrient digestibility in the gastrointestinal (GI) tract. The aim of this study was to investigate whether the rate of gastric emptying or total GI transit times differed between young (3.0±0.9 years) and senior (11.6±1.4 years) cats. Gastric emptying rates were measured using [1- 13C]octanoic acid and total transit times with chromium oxide. No significant differences ( P>0.05) were observed in either the rate of gastric emptying or total transit time between young and senior cats although senior cats exhibited a larger variability in total transit time compared to the younger cats (35.71±14.06 and 26.46±5.80 h, respectively). The results of this study indicate that the observed reduction in nutrient digestibility in ageing cats is not due to alterations in the rate of passage of digesta through the GI tract.

Effect of silage dry matter content and rapeseed meal supplementation on dairy cows: 2. Rumen fermentation and digesta passage rate

The effects of direct-cut and wilted silage with or without rapeseed meal (RSM) supplementation on rumen fermentation and digesta passage rates were studied in a 4×4 balanced Latin square experiment with four multiparous cows. The dry matter (DM) and crude protein (CP) degradabilities of silages were determined in sacco. RSM supplementation replaced 16% of the oat–barley concentrate mixture. The daily concentrate amount was 10 kg. Silages were given ad libitum. The effective degradabilities of dry matter and protein (EPD) were higher ( p<0.001) in direct-cut silage but wilted silage had higher ( p<0.001) content of rapidly degradable protein. Rumen ammonia concentration was higher with direct-cut silage (10.16 versus 8.47 mmol/l, p<0.01), reflecting higher CP content and EPD. Rumen pH and total volatile fatty acid (VFA) concentration in rumen were not affected by silage type, and the differences in molar proportions of rumen VFA’s were small. The proportion of propionate tended to be higher ( p<0.10) with wilted silage, whereas the proportion of butyrate was higher (133 versus 128 mmol/mol, p<0.01) with direct-cut silage. The retention time of the digesta particle phase in alimentary tract was shorter ( p<0.05 or better) with wilted silage. Pool mean retention time (PMRT), which illustrates the retention time of particles in rumen, was shorter (34.0 versus 28.3 h, p<0.05) with wilted silage. Similarly, retention time of particles in the rumen pool of particles small enough to leave the rumen tended to be shorter ( p<0.10) with wilted silage. RSM supplementation tended to increase ( p<0.10) rumen ammonia concentration and decreased the molar proportion of rumen butyrate (132 versus 127 mmol/l, p<0.05). The retention time of particles in pool, which illustrates the rate of particle break down in the rumen, was shorter ( p<0.10) with RSM. In conclusion, the ruminal retention time of particles was shorter with wilted silage. This may affect silage digestibility negatively.

Protein digestion in juvenile turbot ( Scophthalmus maximus) and effects of dietary administration of Vibrio proteolyticus

The trial was made to study the protein digestion in juvenile turbot during passage of digesta from stomach to rectum. Moreover, diet supplementation with the potential probiotic bacteria, Vibrio proteolyticus, was evaluated with regard to protein digestion. For a 3-week period, fish (25–30 g) were fed by oral intubation and received either a liquid mixture consisting of 40% nonpurified control diet and 60% water or this mixture supplemented with 10 10 viable V. proteolyticus ml −1. Daily dry matter intake was 1.5% body weight. As digesta progressed from the stomach to the foregut, hindgut and rectum, the increase in apparent nitrogen digestibility was accompanied by higher ammonia contents, suggesting substantial involvement of the microbiota in protein degradation in the distal segments of the gastrointestinal tract. Water-soluble nitrogen contents were significantly higher in the foregut, presumably corresponding with considerable protein digestion by secreted endogenous enzymes in this digestive segment. Over 65% of the soluble protein in all four parts of the tract had a MW<10,000. The amount of soluble protein and peptides with MW<1000 decreased significantly during transit. This was also found for the proportion of the 10,000–20,000 MW proteins, whereas the highest MW category (>200,000) increased. Ingestion of V. proteolyticus tended to stimulate apparent nitrogen digestibility ( P<0.1). This effect corresponded with increased protein degradation in the proximal intestine as was shown by the significantly elevated fraction of soluble proteins with MW<1000.

Effect of vasoactive intestinal polypeptide infusion on feed intake, digesta flow and nutrient digestion in sheep with access to feed for limited time

Two experiments were conducted to test the hypothesis that vasoactive intestinal polypeptide (VIP) infusion into the gastric artery increases feed intake, duodenal flow and amino acid supply to the small intestine of sheep. Four sheep in exp. 1 and five sheep in exp. 2 were fistulated with rumen and duodenal cannulae. Sheep in exp. 2 also had an ileal cannula. In both experiments animals were fed a diet of alfalfa pellets ad libitum for 8 h per day in a thermoneutral environment (20 ± 2 °C) and had free access to water and mineralized salt blocks. In exp. 1, VIP was infused at 1 nmol min−1 through a gastric-artery catheter for 10 min duration each hour for 3 h each day for 4 consecutive days. In exp. 2, VIP was infused at 1.5 nmol min−1 for 10 min duration each half-hour for 3 h each day for 7 consecutive days. Control sheep were infused with saline. Vasoactive intestinal polypeptide infusion increased (P &lt; 0.05) feed intake by 14.3 and 26.1% in exp. 1 and exp. 2, respectively. In exp. 2, there was a positive regression (P &lt; 0.01) between intake and duodenal passage of dry matter (DM) (n = 5, r2 = 0.67), organic matter (OM) (n = 5, r2 = 0.68), and amino acids (AA) (n = 5, r2 = 0.85). The present results suggest that VIP may play a role as a physiological regulator of feed intake in sheep and also has potential to increase the supply of nutrients to the animal. Key words: Digesta passage, intake, sheep, vasoactive intestinal polypeptide

Effect of forage to concentrate ratio in the diet on ruminal fermentation and digesta flow kinetics in sheep offered food at a fixed and restricted level of intake

AbstractThe effects of four diets differing in their for age: concentrate ratio (80:20, 60:40, 40: 60 and 20:80; g/100 g fresh matter) on rumen characteristics, digestibility and digesta flow kinetics were investigated. Alfalfa hay was used as forage and concentrate was composed of barley, soya-bean meal and maize. Diets were prepared by mixing all ingredients and offered to the animals as complete diets. Eight mature Merino sheep, each fitted with a rumen cannula, were offered 1·055 kg dry matter per day of the corresponding diet over two experimental periods. The daily evolution of ruminai pH, volatile fatty acids (VFA) and ammonia nitrogen (N) concentrations were measured. Digestibility was determined by total faecal collection and Cr and Co were used as markers to estimate digesta passage rates. Microbial nitrogen flow at the duodenum (MNDF) was estimated from the urinary excretion of purine derivatives (PD). The apparent digestibility of organic matter increased (P&lt; 0·001) whereas that of all fibrous fractions decreased linearly (P&lt; 0·05) as the proportion of concentrate in the diet increased. Rumen pH decreased linearly (P&lt; 0·001) with increasing proportions of concentrate but total VFA concentrations were unaffected by changes in the diet (P&gt; 0·05). Both liquid and solid digesta outflow rates from the rumen decreased quadratically (P&lt; 0·01) as the proportion of concentrate in the diet increased. The urinary excretion of total N, urea-N and ammonia-N was unaffected (P&gt; 0·05) by changes in the diet. In contrast, the daily urinary excretion of both allantoin and total PD increased quadratically (P&lt; 0·05) with increasing proportions of concentrate. Consequently, the estimated MNDF increased linearly (P&lt; 0·001) from 9·9 g/day on the high forage diet to 14·5 g/day on the high concentrate diet.