1. A method for estimating the proportions of bacterial- and protozoal-N in the total non-ammonia-N reaching the lower gut of the ruminant under steady-state conditions was evaluated. Three trials using two different diets were conducted with a Holstein steer equipped with a rumen cannula and duodenal re-entrant cannulas. 2. An intraruminal primed infusion of (15NH4)2SO4 was administered for 68 h during each trial. Bacteria and protozoa samples were isolated from rumen fluid at approximately 6 h intervals during each infusion period. Total non-ammonia-N was isolated from duodenal digesta samples taken at approximately the same times. All of these samples were analysed for 15N enrichment. A computer program was used to fit equations to the 15N-enrichment curves of bacterial- and protozoal-N. Models of both bacterial- and protozoal-N kinetics consisted of a small pool which equilibrated rapidly with rumen NH3 and a large pool with a fractional turnover rate of 0.045-0.070/h for bacterial-N and 0.056-0.069/h for protozoal-N. 3. Abomasal fluid turnover was estimated by a single injection of polyethylene glycol (molecular weight 4000) into the rumen followed by sampling of rumen fluid and duodenal digesta. 4. Estimates of abomasal fluid turnover, bacterial-N turnover, and protozoal-N turnover were entered into an equation which was adjusted by computer iteration to fit the 15N-enrichment curve of duodenal digesta non-NH3-N generated from each (15NH4)2SO4 infusion period. The computer fit of this equation to the observed results gave estimates of 0:39-0.45 and 0.22-0.41 for the proportion of duodenal non-NH3-N derived from bacterial-N and protozoal-N respectively. 5. This method is potentially useful in estimating microbial protein passage to the lower gut in ruminants. Sampling digesta from the omasum rather than the duodenum would simplify the method and possibly increase the reliability of the estimates.

/pdf/estimation-of-the-proportion-of-non-ammonia-nitrogen-3u1z54qhip.pdf

Estimation of the proportion of non-ammonia-nitrogen reaching the lower gut of the ruminant derived from bacterial and protozoal nitrogen

Cannulas were surgically implanted in the portal and mesenteric veins and femoral artery of eight crossbred steers averaging 270 kg. They were given primed, continuous 3-hour infusions of U-[14C]-L-lactate and 2-[3H]- or 6-[3H]-glucose into the jugular vein and para-aminohippuric acid (portal blood flow indicator) into the mesenteric vein before and after being changed from a pelleted alfalfa hay to a pelleted 85% concentrate diet. Blood samples were collected at 20-minute intervals during infusions. Reliable blood flow data were obtained on four of the eight steers during the first infusion; the other four were not infused the second time. Dry matter intake, portal blood flow, net portal D-lactate absorption (P less than 0.10), net portal glucose absorption and L-lactate turnover rate (P less than 0.10) increased as a result of increased concentrate (energy) intake. Glucose turnover rate (P less than 0.10), L-lactate absorbed as a percentage of turnover rate, L-lactate converted to glucose and glucose derived from L-lactate concomitantly decreased. Net portal L-lactate absorption was not affected. The direction of the response for portal blood flow, net portal D-lactate absorption, net portal glucose absorption, L-lactate turnover and L-lactate absorbed as a percentage of turnover was the same as that previously observed in lambs under similar experimental protocol. Differences in responses between lambs and steers for glucose turnover and L-lactate converted to glucose may be attributable to differences in dry matter or energy intake or both.

Glucose and Lactate Absorption and Metabolic Interrelationships in Lambs Switched from Low to High Concentrate Diets

Effects of amount of feed intake on in vivo remen propionate production and the reproducibility of measurements of propionate production rates were investigated in five dairy steers weighing 142 to 228 kg. Each steer received 275 g of an 80%-grain diet every 2 hours, and three of the five steers later received 500 g/2 hours. Rumen propionate pool sizes and production rates were determined at both intakes by administering a single dose of [1-14C] propionate via rumen fistula and observing decreasing specific activity of rumen propionate for 4 hours. A linear regression equation was calculated from the natural logs of decreasing specific activity. Propionate pool sizes averaged 30.6 and 47.4 g, and production rates averaged 579 and 1032 g/day at feed intakes of 275 and 500 g/2 hours. Thus, propionate production changed in almost direct proportion to feed intake. Acetate to propionate ratios were about 3:1 in rumen fluid. Considerable variability in estimates of propionate pool sizes and production rates was found both within and among steers. The results indicate propionate production is nearly equivalent to blood glucose turnover determined previously; all propionate produced in the rumen, however, is not used for glucose synthesis.

Gluconeogenesis in Ruminants: Propionic Acid Production from a High-Grain Diet Fed to Cattle

Net absorption of glucose, L-lactate, volatile fatty acids, and nitrogenous compounds by bovine given abomasal infusions of starch or glucose.

Characterization of metabolic changes during a protocol for inducing lactation ketosis in dairy cows.

Quantitation of α-linked Glucose Polymers Passing to the Small Intestine in Cattle

Physiological effects of 1,3-butanediol fed to cattle.

Background Increased awareness of the relationship between certain components in food beyond basic nutrition and health has generated interest in the production and consumption. Functional foods owe much of their health benefits to the presence of bioactive components. Despite their importance, their poor stability, solubility, and bioavailability may require the use of different strategies including nano-delivery systems (NDS) to sustain delivery and protection during handling, storage, and ingestion. Moreover, increasing consumer trend for non-animal sourced ingredients and interest in sustainable production invigorate the need to evaluate the utility of plant-based NDS. Method In the present study, 129 articles were selected after screening from Google Scholar searches using key terms from current literature. Scope This review provides an overview of current trends in the use of bioactive compounds as health-promoting ingredients in functional foods and the main methods used to stabilize these components. The use of plant proteins as carriers in NDS for bioactive compounds and the merits and challenges of this approach are also explored. Finally, the review discusses the application of protein-based NDS in food product development and highlights challenges and opportunities for future research. Key Findings Plant-based NDS is gaining recognition in food research and industry for their role in improving the shelf life and bioavailability of bioactives. However, concerns about safety and possible toxicity limit their widespread application. Future research efforts that focus on mitigating or enhancing their safety for food applications is warranted.

Current trends in nano-delivery systems for functional foods: a systematic review

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Quantitation of α-linked Glucose Polymers Passing to the Small Intestine in Cattle

Physiological effects of 1,3-butanediol fed to cattle.

Current trends in nano-delivery systems for functional foods: a systematic review