Tracking the fate of digesta 13C and 15N compositions along the ruminant gastrointestinal tract: Does digestion influence the relationship between diet and faeces?

Faecal stable isotope compositions reflect wildlife diets, if digestive processes along the gastrointestinal tract (GIT) do not alter diet-faeces isotopic relationships in an unpredictable way. We investigated 13C and 15N compositions of digesta along the ruminant GIT, using Saanen dairy goats kept on pure grass hay or browse for >20days. Isotopic changes occurred in the ventral rumen, and in the small intestine, where digesta had significantly higher δ13C and δ15N (associated with lower C or higher N content, respectively) values relative to other GIT sites. However, effects on isotope fractionation were small (∼1.0‰ for δ13C and ∼ 2.0‰ for δ15N), and were reversed in the hindgut such that faecal isotope compositions did not differ from the foregut. No other substantial isotopic changes occurred across GIT sites, despite the morphophysiological complexity of the ruminant GIT. We found similarly small differences across GIT components of rheem gazelles (Gazella leptoceros) fed a mixture of C3 lucerne and C4 grass, although in this case faeces were 15N-depleted relative to other GIT components. Along with differences in δ15N between goats fed browse or grass, this result implies a systematic difference in diet-faeces δ15N relationships, contingent on the botanical composition of ruminant diets. Thus, while our results support faecal δ13C as a reliable proxy for wildlife diets, further work on factors influencing faecal 15N abundance is needed. Finally, we note high levels of isotopic variability between individuals fed the same diets, even accounting for the relatively short duration of the experiments, suggesting an important influence of stochasticity on isotope fractionatio

Factors influencing the flow of fluid, saliva and some cations through the reticulo-omasal orifice of the cow

vokKirjasto Aj-kTekijöitä, jotka vaikuttavat nesteen, syljen ja eräiden kationien kulkuun lehmän verkkomaha-satakerta-aukost

The composition of ingesta-digesta through the gastrointestinal tract of ruminant cattle

This study was conducted to determine the effect of dietary protein concentration on changes in composition of digesta, especially protein, in the gastrointestinal tract of ruminant cattle. Twenty eight steers were divided into seven groups of four steers each. Each group received one of seven experimental diets. Diets contained 20% cotton seed hulls, .1% chromic oxide, and varied stepwise in crude protein from 9 to 26% of dry matter (otherwise, diets were the same). Steerswere placed on their respective diet 12 to 18 days, then slaughtered approximately 12 hours after their last ad libitum feeding. The digestive tracts of the slaughtered steers were tied into eight segments: rumen, omasum, abomasum, three sections of the small intestine, cecum and large intestine. Subsamples from these segments were analyzed for pH, dry matter, crude protein, ash, acid detergent fiber, crude fiber, acid detergent fiber-nitrogen, soluble nitrogen and ammonia nitrogen. The ash, acid detergent fiber, pH, and dry matter composition of digesta were not affected protein concentration of the diet. However,there were significant changes in the concentration of these components as digesta passed through the tract. Crude protein, ammonia nitrogen, and acid detergent fiber-bound nitrogen tended to increase in the forestomachs and abomasum with increases in dietary protein. Changes in concentration of these components in the small intestines and hindgut were not consistent. Chromic oxide ratios indicated an average six fold dilution of dry matter from the omasum to the first-third of the small intestine. Crude protein increased dramatically in this segment while dry matter declined sharply. These changes were the result of endogenous secretions from the pancreas and intestinal glands. Results of our analyses indicate that endogenous protein secreted into the duodenum of cattle, greatly exceeds the protein content of entering digesta. In light of this finding, protein absorption in the small intestine must be greater than previously thought. A trend for endogenous nitrogen concentration to increase with dietary crude protein concentration was not statistically significant

A mechanistic model of small intestinal starch digestion and glucose uptake in the cow

The high contribution of postruminal starch digestion (up to 50%) to total-tract starch digestion on energy-dense, starch-rich diets demands that limitations to small intestinal starch digestion be identified. A mechanistic model of the small intestine was described and evaluated with regard to its ability to simulate observations from abomasal carbohydrate infusions in the dairy cow. The 7 state variables represent starch, oligosaccharide, glucose, and pancreatic amylase in the intestinal lumen, oligosaccharide and glucose in the unstirred water layer at the intestinal wall, and intracellular glucose of the enterocyte. Enzymatic hydrolysis of starch was modeled as a 2-stage process involving the activity of pancreatic amylase in the lumen and of oligosaccharidase at the brush border of the enterocyte confined within the unstirred water layer. The Na+-dependent glucose transport into the enterocyte was represented along with a facilitative glucose transporter 2 transport system on the basolateral membrane. The small intestine is subdivided into 3 main sections, representing the duodenum, jejunum, and ileum for parameterization. Further subsections are defined between which continual digesta flow is represented. The model predicted nonstructural carbohydrate disappearance in the small intestine for cattle unadapted to duodenal infusion with a coefficient of determination of 0.92 and a root mean square prediction error of 25.4%. Simulation of glucose disappearance for mature Holstein heifers adapted to various levels of duodenal glucose infusion yielded a coefficient of determination of 0.81 and a root mean square prediction error of 38.6%. Analysis of model behavior identified limitations to the efficiency of small intestinal starch digestion with high levels of duodenal starch flow. Limitations to individual processes, particularly starch digestion in the proximal section of the intestine, can create asynchrony between starch hydrolysis and glucose uptake capacity

Evaluation of agro-industrial by-products as protein sources for duck production in the Mekong Delta of Vietnam

This thesis is based on four studies to determine the nutritive value and ileal and total tract amino acid digestibility of agro-industrial by-products, and the effects of inclusion of these by-products in diets on the biological performance of growing crossbred Muscovy and common ducks in the Mekong Delta, Vietnam. The results show that brewery waste (BW) was characterised by high protein content,good balance of essential amino acids, but high crude fibre content. The best growth performance was observed when 50% of the concentrate was replaced by BW for both Muscovy and common ducks. The crossbred Muscovies had better performance and gave higher economic benefit than the local Muscovies, and common ducks gave the lowest profit. BW could be offered either in mixed or separate feeding systems without any effects on performance and carcass yield (Paper I and II). Soya waste (SW) and ensiled shrimp waste (ESW) are good protein sources, but low in dry matter (DM) and methionine content (SW) and high in chitin content (ESW). The best performance in terms of growth rate and carcass quality was found with replacement of up to 60% of soybean meal by SW, and only 20% of fish meal by ESW, which gave the lowest feed costs (Paper III). The inclusion of ESW in diets for adult crossbred common ducks resulted in a linear decrease of the apparent total tract digestibility of dry matter, organic matter, ether extract, N free extract and N retention with increasing levels of ESW. The digestibility of individual amino acids followed a similar pattern to the nutrient digestibility. The apparent total tract digestibility of most individual amino acids was higher than the apparent ileal value (Paper IV). It can be concluded that from nutritive and economic apects the three agro-industrial byproducts evaluated have proven to be acceptable feed ingredients in duck diets. Replacement up to levels of 20% (ESW), 50% (BW) and 60% (SW) of fish meal, concentrate and soybean meal, respectively, in diets for growing crossbred ducks can be recommended under the conditions of the Mekong Delta

The effect of diet on energy partitioning in moose

Thesis (Ph.D.) University of Alaska Fairbanks, 1987Moose (Alces alces) have dynamic seasonal patterns of food intake and body weight changes. Body weight may vary by 35% from winter lows to summer highs. Food intake levels during summer may exceed winter levels by up to a factor of 5. Forage quality and availability are thought to drive the seasonal patterns of food intake and weight loss. Changes in digestive strategy of moose in winter and spring were analyzed in this thesis. During December, the total mean retention time (TMRT) of food in the alimentary tract increased as dry matter intake decreased, while alimentary fill remained constant. In contrast, during April TMRT did not increase with increased intake; rather, alimentary fill increased. There appeared to be a seasonal digestive strategy for optimizing nutrient intake. True basal metabolic rate (TBM) was estimated using regression analysis of heat production on metabolizable energy intake. TBM was estimated at 68.8, close to the interspecies mean of 70 (kcal/kg BW\sp{0.75}/d). However, differences in TBM noted during December, February, and April were not significant. Paper birch (Betula papyrifera) twigs were collected during winter and cut from the tip to 8 specific diameters (2-9 mm), and analyzed for neutral detergent fiber, acid detergent fiber, crude protein, acid detergent lignin, ash, and in vitro dry matter disappearance. Results indicated that dietary quality decreased with increasing diameter. Moose subjected to 4 different stocking rates (23, 31, 41, and 66% utilization of paper birch) showed no difference in the diameter of paper birch (mean = 2.66 mm) harvested. A simulation model was presented in which food intake by moose was controlled by both physiological demands and alimentary capacity. Seasonal estimates of food intake changed with energy demands. The model proved useful in estimating seasonal energy requirements of moose

Effect of roughage quality and period of day on rumen fill after meal termination, digestion, passage rates, and diurnal feeding behaviour in cattle fed on tropical roughage.

Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.In tropical and subtropical regions, ruminant production is prominently dependent on tropical veld grass characterized by low nutritional quality. Feed intake is an essential constituent determining animal performance and the degree at which ruminants utilize feeds of poor quality is reigned by the passage from and degradability rates of digesta in the rumen. Feed intake by ruminants is regulated by rumen fill, which is further influenced by processes occurring in the rumen i.e. degradation, digestion, and passage rates. Furthermore, intake is a result of time spent eating and meal pattern hence, feeding behaviour regulates intake. Therefore, rumen fill, degradation, digestion, passage rates, and feeding behaviour are vital in understanding intake by ruminants. The objectives of the study were to: (i) determine the effect of roughage quality and period of day on diurnal rhythm of feeding behaviour patterns in cattle, (ii) determine the effect of roughage quality and period of day on rumen fill after meal termination, and (iii) confirm the effect of roughage quality on degradation, digestibility, and passage rates. Four ruminally cannulated Jersey heifers were assigned to four dietary treatments comprising improved roughage quality (IRQ), semi-improved roughage quality (SIRQ), moderately improved roughage quality (MIRQ), and poor roughage quality (PRQ). Consequently, heifers were randomly assigned to one of the four roughage diets in a 4 × Latin square design. Data on time spent on each of 11 different behavioural activities (drinking water, eating, idling standing and lying, ruminating whilst standing and lying, hedonic feeding, grooming, licking objects, tongue rolling, and other activities i.e. feed searching) was recorded. Roughage quality had no significant effect on the time spent on each behavioural activity except grooming and tongue rolling. The period-of-day affected time spent on each activity except for idling whilst lying and tongue rolling. Consequently, heifers spent more time eating during the day and ruminating at night. Roughage quality had no effect on fractional passage rates, rumen retention time, and mean retention time. Conversely, the mean retention time of solids in the hindgut was affected by roughage quality. Roughage quality had no effect on total rumen load, rumen DM, and rumen liquor. Total rumen load and rumen liquor were affected by period of day except for rumen DM. Total rumen digesta and rumen liquor were greater at evening than in the morning, afternoon, and late afternoon