Digestive Tract Of Dairy Cows Research Articles

P51 Comparison of external and internal markers for flow measurements in the digestive tract of dairy cows

P51 Comparison of external and internal markers for flow measurements in the digestive tract of dairy cows

A Grain-Based SARA Challenge Affects the Composition of Epimural and Mucosa-Associated Bacterial Communities throughout the Digestive Tract of Dairy Cows.

Simple SummaryHigh-yielding dairy cows must receive high-grain diets in order to meet their high energy requirements. However, these diets depress the pH in the rumen, leading to a condition referred to as subacute ruminal acidosis (SARA), and in the large intestine, and may negatively affect the taxonomic composition and the functionality of the populations of microorganisms in the digestive tract. As cows depend on these microorganisms for nutrient utilization and health, disruptions of their composition and functionality can greatly affect the production, health, and welfare of dairy cows. In our study, SARA was induced experimentally by excessive grain feeding. The taxonomic composition of bacterial populations attached to the epithelia of the digestive tract were determined throughout this tract. Our results show that SARA affected the populations of several taxa of bacteria, which suggests that the beneficial effects of these bacteria may be reduced, and that the digestive tract may be at increased risk of invasion by pathogenic microorganisms. The greatest effects of SARA on the taxonomic composition of bacteria on epithelia were in the rumen and large intestine. Their composition on epithelia in the small intestine was also affected, but the affected groups of bacteria differed from those in the rumen and large intestine.The effects of a subacute ruminal acidosis (SARA) challenge on the composition of epimural and mucosa-associated bacterial communities throughout the digestive tract were determined in eight non-lactating Holstein cows. Treatments included feeding a control diet containing 19.6% dry matter (DM) starch and a SARA-challenge diet containing 33.3% DM starch for two days after a 4-day grain step-up. Subsequently, epithelial samples from the rumen and mucosa samples from the duodenum, proximal, middle and distal jejunum, ileum, cecum and colon were collected. Extracted DNA from these samples were analyzed using MiSeq Illumina sequencing of the V4 region of the 16S rRNA gene. Distinct clustering patterns for each diet existed for all sites. The SARA challenge decreased microbial diversity at all sites, with the exception of the middle jejunum. The SARA challenge also affected the relative abundances of several major phyla and genera at all sites but the magnitude of these effects differed among sites. In the rumen and colon, the largest effects were an increase in the relative abundance of Firmicutes and a reduction of Bacteroidetes. In the small intestine, the largest effect was an increase in the relative abundance of Actinobacteria. The grain-based SARA challenge conducted in this study did not only affect the composition and cause dysbiosis of epimural microbiota in the rumen, it also affected the mucosa-associated microbiota in the intestines. To assess the extent of this dysbiosis, its effects on the functionality of these microbiota must be determined in future.

Polyethylene glycol as an indigestible marker to estimate fecal output in dairy cows

The objective of this study was to evaluate the accuracy of fecal output measurements using polyethylene glycol (PEG) as an external marker determined by near-infrared reflectance spectroscopy. In addition, the accuracy of dry matter intake predictions based on fecal output and digestibility estimated using an internal marker [indigestible neutral detergent fiber (iNDF)] was assessed. The experiment was conducted using 6 lactating dairy cows fed 2 different diets. Polyethylene glycol was administered twice daily into the rumen and the diurnal pattern of fecal concentrations and recovery in feces were determined. To evaluate the effects of alternative marker administration and sampling schemes on fecal output estimates, the passage kinetics of PEG in the digestive tract of dairy cows was determined and used for simulation models. The results indicate that PEG was completely recovered in feces and, thus, fecal output was accurately estimated using PEG. Good agreement between measured and predicted dry matter intake (standard error of prediction = 0.86 kg/d, R2 = 0.81) indicates good potential to determine feed intake using PEG in combination with iNDF. The precision of cow-specific digestibility estimates based on iNDF was unsatisfactory, but for a group of cows iNDF provided an accurate estimate of dry matter digestibility. The current study indicated that, to overcome inherent day-to-day variation in feed intake and fecal output, the minimum of 4 fecal spot samples should be collected over 4 d. Preferably, these samples should be distributed evenly over the 12-h marker administration interval to compensate for the circadian variation in fecal PEG concentrations.

Functional characterization of oligopeptide transporter 1 of dairy cows

BackgroundIt is well known that peptides play a vital role in the nutrition and health of dairy cows. Bovine oligopeptide transporter 1 (bPepT1) is involved in the peptide transport process in the gastrointestinal tracts of dairy cows. However, little information is known in the characteristics of bPepT1. Therefore, the purpose of this study was to characterize bPepT1 functionally using a mammalian cell expression system. The uptake of radiolabeled dipeptide glycyl-sarcosine ([3H]-Gly-Sar) into the bPepT1-transfected Chinese hamster ovary cells was measured at various pH and substrate concentrations and with or without 15 other small peptides that contained Met or Lys.ResultsWestern blot results showed that the abundance of bPepT1 protein in the jejunum and ileum are the highest in the gastrointestinal tract of dairy cows. The uptake of [3H]-Gly-Sar by bPepT1-Chinese hamster ovary cells was dependent on time, pH, and substrate concentration, with a low Km value of 0.94 ± 0.06 mmol/L and a maximum velocity of 20.80 ± 1.74 nmol/(mg protein • 5 min). Most of the di- and tripeptides were the substrates of bPepT1, based on substrate-competitive studies. However, bPepT1 has a higher affinity to the peptides with shorter chains, greater hydrophobicity, and negative or neutral charges.ConclusionsThese results demonstrated for the first time the functional characteristics of bPepT1, and they provide a new insight and better understanding into its vital role in absorbing a wide range of peptides from the digestive tract of dairy cows.

δ13C as a marker to study digesta passage kinetics in ruminants: a combined in vivo and in vitro study

The aim of the current study was to explore the use of the tracer 13C as an internal marker to assess feed fraction-specific digesta passage kinetics through the digestive tract of dairy cows. Knowledge on feed-specific fractional passage rates is essential to improve estimations on the extent of rumen degradation and microbial protein efficiency; however, this information is largely lacking. An in vivo and in vitro experiment was conducted with grass silages (Lolium perenne L.) that were enriched with 13C by growing the grass under elevated 13CO2 conditions. In a crossover design, two dairy cows received pulse doses of two 13C-enriched grass silages and chromium-mordanted neutral detergent fibre (Cr-NDF) into the rumen. The two 13C-enriched grass silages used differed in digestibility and were grown under identical field conditions as the bulk silages fed to the animals. Faecal excretion patterns of 13C-enriched dry matter (13C-DM), neutral detergent fibre (13C-NDF) and Cr-NDF were established, and a nonlinear multicompartmental model was used to determine their rumen passage kinetics. In addition, the 13C-enriched silages were incubated in rumen liquid in an in vitro batch culture system at different time intervals to determine the effect of fermentation on 13C-enrichment in the residue. The in vitro study showed that the 13C : 12C ratios in DM and NDF residues remained stable from 24 h of incubation onwards. In addition, in vitro fractional degradation rates for 12C in the DM and NDF did not differ from those of 13C, indicating that fermentative degradation does not affect the 13C : 12C ratio in the DM nor in the NDF fraction of the residue. Model fits to the faecal excretion curves showed a significant difference in fractional rumen passage rates between Cr-NDF, 13C-DM and 13C-NDF (P ⩽ 0.025). Silage type had no clear effect on rumen passage kinetics (P ⩾ 0.081). Moreover, it showed that peak enrichments for 13C-DM and 13C-NDF in faeces were reached at 30.7 and 41.7 h post dosing, respectively. This is well after the time (24 h) when the 13C : 12C ratios of the in vitro unfermented residues have reached stable enrichment level. Fractional rate constants for particle passage from the rumen are estimated from the descending slope of faecal excretion curves. The present study shows that the decline in 13C : 12C ratio after peak enrichment is not affected by fermentative degradation and therefore can be used to assess feed component-specific fractional passage rates.

Passage kinetics of concentrates in dairy cows measured with carbon stable isotopes

Fractional passage rates form a fundamental element within modern feed evaluation systems for ruminants, but knowledge on feed-specific fractional passage is largely lacking. Commonly applied tracer techniques based on externally applied markers, such as chromium-mordanted neutral detergent fibre (Cr-NDF), have been criticised for behaving differently to feed particles. This study describes the use of the carbon stable isotope ratio (13C : 12C) as an internal digesta marker to quantify the fractional passage rate of concentrates through the digestive tract of dairy cows. In a crossover study, five dairy cows were fed low (24.6%) and high (52.6%) levels of concentrates (dry matter (DM) basis) and received a pulse-dosed Cr-NDF and 13C isotopes. The latter was administered orally by exchanging part of the dietary concentrates of low 13C natural abundance with a pulse dose of maize bran-based concentrates of high 13C natural abundance. Fractional passage rates from the rumen (K1) and from the large intestine (K2) were determined from faecal marker concentrations of Cr-NDF and of 13C in the DM (13C-DM), NDF (13C-NDF) and neutral detergent soluble (13C-NDS). No differences in K1 estimates were found for the two concentrate levels fed but significant differences between markers (P<0.001) were observed. Faecal Cr-NDF excretions gave lower K1 estimates (0.037–0.039/h) than 13C-DM (0.054–0.056/h) and 13C-NDF (0.061–0.063/h). The 13C-NDS was calculated by the difference of 13C in the DM and NDF, and K1 values (0.039–0.043/h) were comparable to Cr-NDF. Total mean retention time was considerably higher for Cr-NDF (40.9–42.0 h) as compared to 13C-DM and 13C-NDF (32.0–33.5 h; P<0.001). The accuracy of the curve fits for Cr-NDF and 13C-DM and 13C-NDF was overall good (mean prediction error of 9.9–13.9%). Fractional passage rate of Cr-NDF was comparable to studies where this marker was assumed to represent the fractional passage of roughages. However, K1 estimates based on the 13C : 12C ratio varied considerably from studies based on external markers. Our results suggest that the use of 13C isotopes as digesta passage markers can provide feed component-specific K1 estimates for concentrates and provides new insight into passage kinetics of NDF from technologically treated compound feed.

Opinion of the Panel on additives and products or substances used in animal feed (FEEDAP) on the safety and efficacy of the product Sel‐Plex 2000 as a feed additive according to Regulation (EC) No 1831/2003

Opinion of the Panel on additives and products or substances used in animal feed (FEEDAP) on the safety and efficacy of the product Sel‐Plex 2000 as a feed additive according to Regulation (EC) No 1831/2003

A comparison of parameters of the passage of nylon capsules and digesta calculated from faecal excretion data obtained in lactating cows

The aim of the study was to compare parameters of passage of nylon capsules and digesta represented by Cr-labelled maize silage through the digestive tract of dairy cows. The capsules were made of nylon cloth (42&amp;nbsp;&amp;micro;m pore size, 10 mm outside diameter) and applied orally. The evaluation was carried out in dairy cows with milk yield of 19.0 kg/day. The diet (17.6 kg DM/day) consisted of maize silage, lucerne hay and concentrate. Total mean retention time (TMRT), delay time (&amp;tau;), summarised compartmental mean retention time (CMRTS), and mean individual compartmental retention times (CMRT1 and CMRT2) were calculated. TMRT, &amp;tau;, CMRTS, CMRT1 and CMRT2 values of nylon capsules and Cr-labelled silage were 36.2 and 45.4 h (P &amp;lt; 0.01), 16.2 and 8.3 h (P &amp;lt; 0.01), 20.1 and 37.2 h (P &amp;lt; 0.01), 7.8 and 8.5 h, 12.2 and 28.7 h (P &amp;lt; 0.05), respectively. The calculated mean retention time of nylon capsules in the reticulo-rumen (CMRTS) was shorter and in the intestines (&amp;tau;) was longer than that of digesta. For this reason the estimation of digestibility using the nylon capsule method can be questionable. &amp;nbsp;

Effect of heat processing of protein sources on the disappearance of their selenium from mobile bags in the digestive tract of dairy cows

It was proposed that the organic selenium (Se) in ruminant feedstuffs, a large proportion of which is present in the protein molecule, should become available for digestion to the same extent as the protein in a feedstuff when passing through the digestive tract of the ruminant. Factors such as heat processing of feedstuffs that decrease protein degradability in the rumen should also reduce the proportion of its Se metabolised during microbial fermentation in the rumen. This should increase the proportion of unchanged dietary Se reaching the lower digestive tract. Six plant protein sources were roasted in a laboratory scale electric drum roaster at different temperatures and time intervals, and four fish meal and four blood meal samples were obtained from different processing plants. The mobile bag technique was used to measure the disappearance of crude protein (CP) and Se from the feedstuffs when incubated in the rumen and passing through the lower digestive tract of dairy cows. For the plant protein sources, the disappearances of Se and CP in the rumen and lower digestive tract were correlated, with coefficients of determination ( r 2) of 0.718 and 0.717, respectively. However, for the animal protein sources these correlations were low. The ruminal disappearance of Se from all unprocessed plant proteins was higher ( P<0.05) than those from their corresponding heat-processed samples. Ruminal disappearances of CP in the same samples showed the same trend as Se, viz. that heat processing reduced ( P<0.05) the ruminal disappearance of CP from these feedstuffs. Only small proportions of Se in the unprocessed plant proteins disappeared from the bags in the lower digestive tract, but after heat treatment these proportions were significantly higher. Protein disappearances followed a similar pattern. It is evident from this study that the fate of Se in the organic form in feeds is affected by the extent of exposure of the feed to ruminal fermentation. Factors affecting ruminal protein degradation such as heat processing will determine also whether Se will be subjected to microbial reduction or incorporation into microbial proteins, or would escape rumen microbial fermentation. Evidence suggested that the overprocessing of some of the test feeds reduced the availability of their Se in the digestive tract. It is concluded that heat processing of feedstuffs can contribute to the factors affecting the bio-availability of Se in feeds.

Influence of prolonged adaptation periods on starch degradation in the digestive tract of dairy cows

Three German Holstein cows with ruminal and duodenal cannulas (Trial 1) and four non-lactating Slovakian White and Black cows with an additional ileal re-entrant cannula (Trial 2) were used to determine the effects of prolonged adaptation periods on rumen fermentation and starch digestibility in the digestive tract. In Trial 1, the cows received a starch rich diet and in Trial 2, either 1.0 or 2.0 kg corn or wheat starch per cow and per day were continuously infused into the duodenum. In Trial 1 feces, rumen fluid and duodenal digesta were sampled after 14, 16 or 21 days and after 35, 37 or 42 days of adaptation, respectively. In Trial 2, the duodenal and ileal nutrient flow as well as fecal excretion were measured without starch infusion in a preperiod, as well as 9 or 23 days after starting starch infusion. In Trial 1, the rumen pH was increased (5.4 versus 5.9; P≤0.05) and the total volatile fatty acid (VFA) concentration was decreased (144.1 mmol/l versus 134.3 mmol/l; P≤0.01) with prolonged adaptation period. The ruminal digestibility of nearly all nutrients increased numerically, but only that of OM for the diet containing corn increased significantly (45.8% versus 48.3%; P≤0.05) after longer adaptation time. In Trial 2, starch digestion in the small intestine decreased with increasing amounts of starch in the intestine (corn starch: from 71.4 to 50.3%; P≤0.001; wheat starch: from 73.8 to 53.1%; P≤0.001) and was increased by 1.5–2.8 percentage units ( P≤0.05) after prolonged adaptation period. The decreased starch digestibility in the small intestine with increased amounts of starch in the duodenum was not totally compensated for in the large intestine. The high amounts were still 16.4 percentage units (corn starch) and 18.1 percentage units (wheat starch) less digested than the small amounts. The longer adaptation period had small but significant ( P<0.05) effects on the starch digestibility in the total intestine.

Barley Processing, Forage:Concentrate, and Forage Length Effects on Chewing and Digesta Passage in Lactating Cows

Dietary factors that alter fermentability, NDF content, or particle size of the diet were evaluated for their effects on chewing behavior and distribution and passage of feed particles in the digestive tract of dairy cows. A double 4 × 4 quasi-Latin square design with a 23 factorial arrangement of treatments was used. The dietary factors were: extent of barley grain processing, coarse (1.60mm) or flat (1.36mm); forage-to-concentrate ratio (F:C), low (35:65) or high (55:45) (dry matter basis); and forage particle length, long (7.59mm) or short (6.08mm). Eight lactating cows with ruminal and duodenal cannulas were offered ad libitum access to total mixed diets. Chewing time, expressed as minutes per day or per kilogram of dry matter or neutral detergent fiber (NDF), was increased with high F:C diets due to increased eating and ruminating times but was decreased when expressed per kilogram of NDF intake from forage. The influence of forage particle length or grain processing on chewing activity was less pronounced than F:C ratio. Chewing activity was positively correlated to proportion of long forage particles in the diet but not to particle length of the diets. Influence of feed particle size on particle size distribution in different sites of the digestive tract was minimal. Particle size distributions of duodenal digesta and feces differed; the proportion of particles retained on the 3.35- or 1.18-mm screens was higher, but proportion of particles that passed through the 1.18-mm screen was lower in duodenal digesta than in feces. Relationships between chewing activities and ruminal pH or fractional passage rate of rumen contents were not significant. These results indicate that particle size of barley-based diets was not a reliable indicator of chewing activity. Forage particle size and NDF content of the diets were more reliable indicators of chewing activity than was the NDF content of forage. Fecal particle size was not an appropriate means of estimating the size of particles exiting the reticulorumen, at least for barley-based diets. Breakdown of coarse particles was necessary, but not a rate-limiting step for particles exiting the rumen. Passage rate of the rumen contents was affected by numerous factors including chewing activity.

Effects of silage fermentation on milk protein and fat content and yield

The extent and type of in-silo fermentation has a profound influence on the composition of nutrients absorbed from the digestive tract of dairy cows (Choung &amp; Chamberlain, 1993; van Vuuren et al. 1995). The amount of amino acids absorbed from the small intestine decreases when the extent of in-silo fermentation is increased due to reduced efficiency of microbial protein synthesis. The ratio of lipogenic to glucogenic VFA increases when in-silo fermentation is restricted, since silage lactic acid generally increases propionate in rumen VFA, whereas WSC in silage increases acetate, butyrate or both. The purpose of this study was to estimate quantitative relationships between silage fermentation characteristics and milk production using data based on mean treatment values of production parameters and silage fermentation characteristics.

Retention of Cr-labelled grass hay and silage in different segments of the gastrointestinal tract of dairy cows

Two experiments were conducted to study solids retention in different segments of the digestive tract of dairy cows. In Exp. 1 three lactating cows with rumen and duodenal cannulae were fed grass silage and lib, and 0, 3 or 6 kg of concentrates per day in a Latin square design. Retention in the total tract (MRT tot), stomachs (MRT st) and, by difference, intestines (MRT int), was measured from the changes in Cr concentration in duodenal and faecal samples after a single dose of Cr-mordanted fibre in the rumen. A 3-pool kinetics model with lag was fitted to the data. In Exp. 2, 3 lactating and 2 dry rumen cannulated cows were used. The lactating cows were fed hay, fresh grass and concentrates at 16–17 kg DM/d and the dry cows were fed 8.0 kg hay alone. Hay and faeces were Cr-mordanted and given as a pulse dose in the rumen or through the reticulo-omasal canal, respectively. Retention in total tract, post-rumen (MRT pt ) and by difference, rumen-reticulum (MRT L ), was calculated as in Exp. 1. The silage based diets in Exp. 1 tended to give higher MRT tot than the hay and grass diets in Exp. 2 but the decrease in retention time with intake was also more marked. A very small effect of intake on MRT int and MRT pr, was seen in both experiments. Lag as a proportion of MRT for individual parts of the gastrointestinal tract was used as an indicator of incomplete mixing. The proportion decreased in the order of intestines > post-rumen > stomachs > rumen. The proportion of MRT st (Exp. 1) and MRT r (Exp. 2) in MRT tot was 0.88 and 0.67, respectively. Retention in the rumen was characterized by both a lag phase and multiple pools.

Effects on milk yield and composition of infusions of different levels and natures of energy into the digestive tract of dairy cows

Effects on milk yield and composition of infusions of different levels and natures of energy into the digestive tract of dairy cows

Effects on milk yield and composition of infusions of volatile fatty acids and caseinate into the digestive tract of dairy cows

Effects on milk yield and composition of infusions of volatile fatty acids and caseinate into the digestive tract of dairy cows

Passage rate of liquid and particles in the digestive tract of dairy cows fed fresh forage

Passage rate of liquid and particles in the digestive tract of dairy cows fed fresh forage

Effects on milk yield and composition of infusions of volatile fatty acids and caseinate into the digestive tract of dairy cows

Effects on milk yield and composition of infusions of volatile fatty acids and caseinate into the digestive tract of dairy cows

Passage rate of liquid and particles in the digestive tract of dairy cows fed fresh forage

Passage rate of liquid and particles in the digestive tract of dairy cows fed fresh forage

Effects on milk yield and composition of infusions of different levels and natures of energy into the digestive tract of dairy cows

Effects on milk yield and composition of infusions of different levels and natures of energy into the digestive tract of dairy cows

Fluid dynamics and particle transit in the digestive tract of dairy cows fed maize silage

Fluid dynamics and particle transit in the digestive tract of dairy cows fed maize silage