The digestion of yeast cell wall polysaccharides in veal calves

1. The digestibility of the cell wall polysaccharides of an alkane-grown yeast in different parts of the digestive tract of two veal calves fitted with re-entrant cannulas at the end of the ileum was studied by replacing part of the skim-milk powder of their ‘normal’, milk-substitute (all-milk-protein) diet by yeast (yeast diet). 2. The lactose and glucose of both the all-milk-protein diet and the yeast diet were almost completely digested before the end of the ileum. During this digestion a small amount of oligosaccharides composed of galactose and glucose was synthesized. These oligosaccharides were digested again in the large intestine. 3. The constituent sugars of the water-soluble fraction of the yeast cell wall carbohydrates were glucose and mannose. The 0.5 m-sulphuric acid-hydrolysate of the water-insoluble fraction contained glucose and mannose and the 12 m-H2SO4-hydrolysate only glucose. 4. Digestibilities of these fractions over the whole gastrointestinal tract ranged from 0.77 to 0.90. Digestibilities measured at the end of the ileum varied considerably between the two animals and averaged only about 0.40. 5. These findings suggest that the cell wall polysaccharides of yeast are digested very little by the normal digestive enzymes of the calf's small intestine, but are used as a substrate by the bacterial flora which are mainly concentrated in the large intestine

Observations on the fermentation of carbohydrates along the gastro-intestinal tract of a fistulated cow.

One cow was provided with cannulae in the proximal duodenum and terminal ileum. Three experimental rations were offered: 1, hay 7 kg/day and concentrate 6; 2, hay 3 kg/day, paper pulp 3 and concentrate 3.7; 3, fresh grass 11 kg DM/day. Rations 2 and 2 were given twice daily and 3 was offered more frequently. Experimental periods were 5 days in experiment 1 and 7 days in 2 and 3. Samples were taken from each cannula every 2 h for 5 days. Faeces were collected in each period. Flow rate of the intestinal contents was measured with polyethylene glycol and chromium sesquioxide as markers. Carbohydrates in the feed, digesta and faeces were fractionated according to solubility into ethanol-soluble sugars, alpha -glucose polymers, fructosan, water-soluble polysaccharides other than alpha -glucose polymers and fructosan, neutral-detergent-soluble polysaccharides and neutral-detergent residue. Sugars, sialic and uronic acids were measured in the hydrolysates and the sugars were separated chromatographically.Most of the ethanol-soluble sugars and all the fructosan was digested in the rumen, reticulum, omasum and abomasum, considered collectively as the stomach. Digestion of alpha -glucose polymer occurred mainly in the stomach and only 5 to 10% was digested in the small intestine and caecum with colon. The hay and concentrate ration contained more starch than the others and a higher proportion of this was digested in the small intestine and caecum with colon (20.3 and 6.8% of the digestible starch). The water-soluble fraction was digested mostly in the stomach; on rations 1 and 3 more component carbohydrates disappeared from the small intestine than the caecum with colon. Bacterial polysaccharides were thought to be digested in the small intestine and some bacterial growth was indicated, particularly on ration 2 which contained large amounts of cellulose. Fermentation and addition of bacterial polysaccharides and mucus confused the picture of digestion of the neutral-detergent-soluble fraction, but on all 3 rations it was higher in the small intestine than in the caecum with colon. The neutral-detergent residue was mainly fermented in the stomach and the caecum with colon. (Abstract retrieved from CAB Abstracts by CABI’s permission

Degradação ruminal e estimativa de consumo de genótipos de capim-elefante anão Ruminal degradation and intake prediction of the dwarf elephant grass genotypes

Os objetivos neste estudo foram avaliar a degradação ruminal in situ da matéria seca (MS) e da fibra em detergente neutro (FDN) e estimar o consumo de matéria seca de genótipos de capim-elefante anão em diferentes intervalos de corte. Os tempos de incubação no ambiente ruminal foram 0, 3, 6, 12, 24, 36, 48, 72, 96 e 144 horas. O delineamento experimental utilizado foi o de blocos casualizados com três repetições (animais), dois genótipos de capim-elefante anão (CNPGL 94-34-3, CNPGL 92-198-7) e a cultivar Mott, avaliados em intervalos de corte de 14, 28, 42, 56, 70 e 84 dias, em esquema em parcelas subdivididas. Os parâmetros de degradação da MS e FDN e suas degradabilidades potencial e efetiva não apresentaram grande variação entre a cultivar Mott e os genótipos CNPGL 94-34-3 e CNPGL 92-198-7, mas reduziram substancialmente com o aumento da maturidade da planta em todos os genótipos. As estimativas de consumo geradas por duas equações são adequadas a esses alimentos.<br>The objectives of this study were to assess the in situ rumen degradation of dry matter (DM) and neutral detergent fiber (NDF) and the estimated DM intake of dwarf elephant grass genotypes in different cutting intervals. The incubation periods in the rumen environment were 0, 3, 6, 12, 24, 36, 48, 72, 96 and 144 hours. A randomized block design was used with three replications (animals), two dwarf elephant grass genotypes (CNPGL 94-34-3 and CNPGL 92-198-7) and the cv. Mott, with cutting intervals of 14, 28, 42, 56, 70 and 84 days, in a split plot design. The parameters of DM and NDF degradation, and its potential and effective degradabilities did not vary greatly for cv. Mott and the CNPGL 94-34-3 and CNPGL 92-198-7 genotypes, but they decreased substantially with increased plant maturity for all the genotypes. Intake estimates generated by two equations are considered valid for these feeds