The objective of the current study was to evaluate the effect of unrepresentative sampling of digesta particulate matter entering the omasal canal on the accuracy of fiber flow measurements. The experimental design comprised one period, one diet, and three cows as experimental units. Within each cow, the physical and chemical composition of digesta particulate matter was assessed at seven sites within the digestive tract. Three Finnish Ayshire dairy cows, equipped with ruminal and simple-T duodenal cannulas, in extended lactation were offered grass silage twice daily on an ad libitum basis. Digesta samples were collected from the rumen (dorsal and ventral sac), reticulum, omasal canal, omasum, duodenum, and rectum to determine particle size distribution in digesta, chemical composition of various particle size fractions, and distribution of two flow markers (Cr-labeled straw and indigestible NDF [INDF]) among particle size fractions. Digesta samples were wet-sieved using sieves of 2.50, 1.25, 0.630, 0.315, 0.160, and 0.080 mm. Particulate matter was analyzed for OM, NDF, and Cr concentrations, and INDF concentration was determined based on 12-d ruminal incubation. The particle size of digesta entering the omasal canal was larger compared with the omasum or the duodenum, suggesting that omasal canal samples were not representative of particle size distribution truly escaping the rumen. The concentration of potentially digestible NDF (PDNDF) decreased with decreasing particle size. The PDNDF concentration of particulate matter retained on all sieves was greatest in the rumen and gradually decreased along the digestive tract. From the reticulorumen to the omasum, the decrease was associated with decreased particle size, reflecting selective passage of particulate matter. In contrast, from the omasum to the duodenum and rectum, the PDNDF concentration decreased within each particle size fraction without effect on particle size, indicating a nonselective passage of particulate matter between these sites. Variation between particle size fractions was slightly greater for Cr concentration than for INDF concentration, indicating that unrepresentative sampling of particulate matter had a greater effect on Cr concentration compared with that of INDF. Owing to unrepresentative sampling, NDF entering the omasal canal was overestimated by 5% using INDF and underestimated by 7% using Cr as a particle phase marker. Of total NDF digestibility, proportionally 0.90, 0.07, and 0.03 occurred in the reticulorumen, omasum, and intestines, respectively. The current results indicate that, despite unrepresentative sampling of digesta particulate matter entering the omasal canal, the errors in determined NDF flow were small. The omasum may have a greater role in postruminal NDF digestion than the intestines.
Eight different roughages (clover grass silage, 2 samples of fresh clover grass, fresh ryegrass, winter wheat whole crop silage, pea whole crop silage, dried grass and goats rue) were examined for effective degradability in the rumen and total tract digestibility of individual amino acids (AA), total AA and crude protein using in situ method. Effective degradabilities calculated at a rumen fractional outflow rate of 5%/h, were higher for crude protein than for total AA (the differences ranging from 1.9 to 4.1 percentage points). Arginine was the least degradable amino acid, particularly in silage and in short rumen incubations, although cysteine and phenylalanine also tended to be less degraded than total AA. The most degradable amino acids were alanine and proline in silages, and cysteine, aspartic acid and glutamic acid in the other roughages.Disappearance of total AA from mobile bags containing samples of feeds after 16 h preincubation in the rumen varied from 79.8% in dried grass to 95.9% in fresh clover grass, and was generally similar to the disappearance of crude protein, 79.7-96.3%, respectively. In most of the examined roughages, cystine and glycine disappeared the least, and glutamic acid, aspartic acid and alanine the most from mobile bags, as compared with total AA.
The experiments were carried out on 8 one-year-old rams of about 45 kg body weight, 4 with a surgically isolated caecum pouch (250 ml) and 4 with an approximately 1 m long isolated colon loop. The animals were fed a basal diet containing 11 % CP or supplemented with urea to 14 or 17% CP. To study the influence of hypo-and hypertonic solutions on nitrogen compound secretion, the isolated caecum pouch was washed with antibiotics and filled with 0.45, 0.9, 1.8 or 2.7 % NaCl solutions. Samples were taken after 4h to determine secreted nitrogen compounds. Increasing the NaCl concentration from 0.45 to 1.8% had no effect, but at 2.7% it significantly raised the amount of total-N secreted into the caecum from 5.4 to 14.3; protein-N rose from 3.8 to 11.9 and urea-N from 1.5 to 2.8 mg/h for 0.45 and 2.7% NaCl, respectively. The influence of the CP level in the diet was studied at 0.9% NaCl solution in the caecum and colon. Increasing the level of CP in the diet from 11 to 17% caused an insignificant rise of total-N secretion into the caecum pouch from 5.6 to 6
Three male sheep of about 25 kg body weight fitted with a cannula into the rumen and reentrant cannula in the proximal duodenum and in the distal ileum were used for this study. Sheep No. 1 was infused intraruminally with 15 N urea (lg /d, 95 atom% 15 N) for labelling with 15 N, Nos. 2 and 3 with unlabelled urea. All animals were fed 800 g DM /d of a hay and concentrate diet (40 : 60) containing 15.4 % crude protein and 15.3 % crude fibre, divided into 6 feeding portions per day. After reaching a quasi-steady state in the 15 N level of animal No. 1, passage of total N and l5 N throughout the duodenum and the ileum, N excretion in faeces and urine were estimated. On day 7 and 8 of the experiment the duodenal and ileal digesta were exchanged between the labelled animal (No. 1) and the unlabelled ones (No. 2, 3) according to the respective scheme. Digesta flow was measured directly during 48 h and 3% aliquots were sampled for analysis of N and 15 N content. The contents of N and
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