Biomedical subjects

D L Harmon

Publications and source records attributed to D L Harmon.

At least 73 records · Page 4Linked to original sources

PubMed1994

Evaluation of nutrient utilization in the canine using the ileal cannulation technique.

Nine mature mongrel dogs were used to evaluate a surgical technique for the cannulation of the terminal ileum and used in two experiments to determine the effect of carbohydrate source on starch and dry matter digestion. Dogs (16.2 +/- 2.0 kg body weight; means +/- SD) were fitted with an ileal T-cannula constructed of polyvinyl chloride pipe. The cannula was inserted into the terminal ileum approximately 10 cm proximal to the ileocecal junction and the cannula was exteriorized through a small incision on the right flank. Dogs recovered quickly from surgery (5d). A preliminary study using Cr:EDTA in the food indicated that sampling for 12 h postprandially allowed near complete representation of digesta flow for a meal; peak flow occurred 4-to 8-h postfeeding. Two experiments were performed evaluating the effect of carbohydrate source on ileal starch and dry matter digestibility. Dogs were fed two meals daily with Cr2O3 used as a digesta marker. Diets contained 67% extruded grain (corn, rice, oats or barley) and 33% canned meat supplement on a dry matter basis. Starch digestion was complete (> 98%) within the small intestine and was unaffected by carbohydrate source. In experiment 1, prececal and total tract dry matter digestibilities were higher for rice than corn, and in experiment 2, barley was higher than oats. The ileal T-cannula allows for measurement of small intestinal nutrient disappearance without the confounding effects of colonic microflora. This method may be useful when applied to the study of other nutrients in dogs.

Animal Feed↗

PubMed1994

Effects of slaframine and 4-diphenylacetoxy-N-methylpiperidine methiodide (4DAMP) on pancreatic exocrine secretion in the bovine.

Three Holstein steers (345 +/- 22 kg) surgically fitted with a pancreatic cannula were used in two 3 x 3 Latin square design experiments to examine the effects of slaframine (SF), a muscarinic agonist, or 4-diphenylacetoxy-N-methylpiperidine methiodide (4DAMP), an M3 muscarinic glandular receptor antagonist, on pancreatic exocrine secretion. Pancreatic exocrine secretion was collected for 8 h postdosing at 30-min intervals beginning 1 h postfeeding. In experiment 1, steers were dosed with 0, 25, or 50 micrograms.kg-1 body weight (BW) of SF. Secretion of pancreatic juice and the pH of the secreted juice increased linearly (p < 0.05) with SF; however, secretion rate showed a time by treatment interaction (p < 0.05), as treatments converged 7 h postdosing. Trypsin secretion tended (p < 0.10) to show a quadratic response to SF administration, with the 25 micrograms SF.kg-1 BW dose having the lowest value. In experiment 2, steers received 50 micrograms.kg-1 BW of SF (positive control), 113 micrograms.kg-1 BW of 4DAMP (isosmolar with SF), or both. SF caused a greater pancreatic fluid secretion (p < 0.10) than 4DAMP, with SF plus 4DAMP intermediate. A time by treatment interaction (p < 0.04) was found, since treatments converged 8 h postdosing. Trypsin secretion was higher (p < 0.05) for SF than the other treatments. Chymotrypsin, alpha-amylase, and protein secretion were not affected. SF and 4DAMP alter pancreatic fluid secretion in the steer but have minimal effects on enzyme secretions.

Alkaloids↗

PubMed1994

Effects of mesenteric vein L-alanine infusion on liver metabolism of organic acids by beef heifers fed diets differing in forage: concentrate ratio.

Effects of diet forage:concentrate ratio and mesenteric vein L-alanine infusion on net VFA metabolism by portal-drained viscera (PDV) and liver were determined in four multicatheterized Hereford x Angus heifers (443 kg BW) fed in equal meals every 2 h pelleted, isonitrogenous diets containing 75% alfalfa or 75% corn:soybean meal (SBM) in a balanced single reversal of diets with 6 wk for adaptation. In addition, effects of L-alanine infusion on net metabolism of individual amino acids (AA) by PDV and liver was determined when heifers were fed 75% corn:SBM. Four measurements of blood flow (p-aminohippurate dilution) and net flux of VFA and AA (venous-arterial difference times blood flow) were obtained at 30-min intervals immediately before beginning and ending a 24-h mesenteric vein infusion of L-alanine at 75 mmol/h. Net PDV absorption of acetate (P < .02), propionate (P < .02), and total VFA (P < .02) was lower when 75% corn:SBM was fed, reflecting increased carbohydrate digestion postruminally and only partially balanced by increases in net PDV glucose absorption reported previously. In addition, net PDV absorption of n-butyrate was lower when 75% alfalfa was fed. Excluding acetate, net liver removal of VFA was 83 to 108% of their net PDV release. L-Alanine infusion did not affect net PDV or liver flux of VFA but decreased net total splanchnic (PDV plus liver) release of propionate (P < .07) and n-butyrate (P < .03) and decreased (P < .10) net PDV release and liver removal of glycine. In spite of the increase in liver L-alanine removal, the ratio of glucose release to precursor removal remained remarkably constant across the liver when L-alanine was infused, emphasizing the tight control of liver glucose release and the dynamic interplay of precursor supply and removal in the maintenance of liver carbon balance.

Alanine↗

PubMed1994

Absorption and delivery of nutrients for milk protein synthesis by portal-drained viscera.

The predictability of diet effects on milk composition is limited by the lack of understanding of the metabolic transformations that absorbed nutrients undergo within the portal-drained viscera and liver of high yielding dairy cows. The mass of splanchnic tissues increases dramatically in early lactation, but little is known about the regulation of gut growth and adaptation in early lactation, and further research may provide strategies for optimizing gut adaptation. Glucose is critical for milk synthesis, but portal-drained visceral tissues normally use rather than absorb glucose on a net basis. Dietary starch of low ruminal digestibility increases postruminal starch digestion and decreases net use of glucose by portal-drained viscera slightly, but increases in glucose absorption by portal-drained viscera never account fully for increases in starch disappearance from the small intestine and occur at the expense of VFA absorption. For cows in positive energy balance, greater glucose availability increases tissue energy balance and glucose oxidation, but has little effect on milk or milk protein yield. Similarly, chronic increases in propionate absorption have little effect on milk or milk protein yield. In contrast, casein infusion into the small intestine consistently increases milk and milk protein yield, but the mechanisms responsible remain unclear. There are few data describing the absorption and metabolism of AA by splanchnic tissues of lactating dairy cows, but, as for glucose and VFA, utilization of many AA by portal-drained viscera is substantial. In addition, the contribution of peptides to AA absorption and transport is uncertain and must be clarified. Therefore, measurements of nutrient disappearance from the lumen of the gut cannot be equated with nutrient appearance in the portal vein. Data describing metabolism of nutrients by portal-drained viscera and liver of high yielding dairy cows are needed to improve feeding standards.

Absorption↗

PubMed1993

Two new mutations in a late infantile Tay-Sachs patient are both in exon 1 of the beta-hexosaminidase alpha subunit gene.

We have identified two new point mutations in the beta-hexosaminidase alpha subunit (HEX A) gene in a non-Jewish Tay-Sachs disease patient with an unusual late infantile onset disease phenotype. The patient was a compound heterozygote with each allele of the HEX A gene containing a different mutation in exon 1. One of these is a T to C transition in the initiation codon, expected to produce no alpha subunit and therefore a classical infantile phenotype. The unusual clinical aspects and later onset in the patient must therefore be a result of residual hexosaminidase A activity associated with a mutant alpha subunit containing the second mutation, substitution of serine for proline at amino acid 25 owing to a C to T change at nucleotide 73. Western blotting and DE-52 ion exchange chromatography have been used to examine the behaviour of this mutant alpha subunit.

Amino Acid Sequence↗

PubMed1993

Supplemental fat and ionophores in finishing diets: feedlot performance and ruminal digesta kinetics in steers.

One feedlot trial (116 d; 192 steers) with a factorial arrangement of treatments was conducted to determine effects of supplemental fat and ionophores in corn-based finishing diets. Factors were level of fat (0 or 4% tallow) and ionophore type (none [N], lasalocid [L], monensin plus tylosin [MT], or daily rotation of L and MT [LMT]); L, M, and T were fed at 31, 25, and 10 ppm (DM basis), respectively. Fat and ionophore interacted for DMI (P < .10), ADG (P < .01), and gain:feed G/F, P < .05). Compared with 0%-fat diets, 4% fat decreased (P < .005) DMI by steers fed MT by 8.9%. In 0%-fat diets, MT increased (P < .05) ADG and G/F compared with N or L; however, this increase was negated or reversed in 4%-fat diets. Fat and ionophore interacted (P < .16) on dietary NE concentration. In the 0%-tallow diet, MT increased NEm and NE(g) by 5.1 and 7.0%, respectively, but MT had not effect on NE concentration of the 4%-tallow diet. Alternate feeding of L and MT did not increase animal performance above that of separate, continuous feeding. Six ruminally fistulated steers were used in a metabolism study to evaluate potential mechanisms underlying the interactions observed in the feedlot trial. Treatments were the same as the feedlot trial, except that LMT was not included. Ruminal digesta kinetics were not altered (P > .30) by the addition of fat or ionophores to the diet. Fat and ionophore interacted (P < .05) for molar proportions of ruminal acetate and propionate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1993

Influence of addition of monensin to an alfalfa hay diet on net portal and hepatic nutrient flux in steers.

Six Holstein steers (381 +/- 11 kg BW; mean +/- SE) surgically fitted with hepatic portal (n = 6), hepatic venous (n = 4), mesenteric venous, and arterial catheters were used in a replicated crossover design experiment to evaluate the influence of monensin addition to an alfalfa hay diet on net portal and hepatic nutrient flux. Steers were fed 6.5 kg of DM/d in 12 portions using automatic feeders. Diets included chopped alfalfa hay (20.4% CP) plus 418 g of DM/d of finely ground corn (8.5% CP) with monensin added (240 mg/d) for treated steers. Experimental periods lasted 21 d, with blood samples taken on the final 2 d of each period. Five sets of arterial, portal, and hepatic blood samples were collected hourly from 0900 to 1300 each day. Ruminal fluid samples were collected by stomach tube at the end of each sampling day for VFA analysis. Blood flow was determined by a primed-continuous infusion of p-aminohippurate into the mesenteric venous catheter. Addition of monensin increased (P = .04) the molar percentage of ruminal propionate and decreased ruminal isobutyrate (P = .02) and isovalerate (P = .03). Percentages of the other ruminal VFA, total ruminal VFA concentration, and pH were not affected by feeding monensin. The arterial concentrations of L-lactate (P = .02) and beta-hydroxybutyrate (P = .01) were greater with monensin; however, none of the arterial concentrations of the other metabolites was changed. Feeding of monensin also did not affect (P > .10) portal, hepatic, or hepatic arterial blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1993

Influence of source and amount of dietary protein on performance, blood metabolites, and reproductive function of primiparous beef cows.

Forty Angus x Hereford 2-yr-old primiparous cows (358 kg) were used to determine the effects of source and amount of CP on performance, reproductive function, and metabolic status of suckled primiparous cows. A 2 x 2 factorial treatment arrangement was used; cows received either 100 or 150% of NRC recommendations for CP in diets that contained either soybean meal (low escape = L) or corn gluten meal/blood meal (high escape = H) as the principal supplemental protein source. Resulting treatments were 100-L, 100-H, 150-L, and 150-H. Cows were individually fed diets for 100 d or until they were observed to be in standing estrus. Diets were isoenergetic and limit-fed to meet NRC recommendations for NE, Ca, and P for 364-kg, 2-yr-old primiparous cows producing 4.5 kg of milk daily and gaining .23 kg/d. Increased CP tended (P = .09) to increase ADG in cows, but body condition score was unaffected. Increased CP and use of a CP source with higher potential for ruminal escape increased ADG in calves from d 0 to 97 (P = .002 and .04, respectively), which corresponded with numerical changes in milk production. Feeding high escape CP sources decreased plasma glucose and urea N (P = .04 and .0001, respectively). Increased CP tended (P = .12) to increase plasma glucose and increased (P = .0001) plasma urea N. Treatment had no effect on profiles of LH or progesterone. Although numerical differences in conception rate seemed large for 100-L compared with the remaining treatments, statistical significance was not detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1993

Periparturient changes in intake, ruminal capacity, and digestive characteristics in beef cows consuming alfalfa hay.

Four multiparous, ruminally fistulated Angus x Hereford cows (average BW = 568 kg) were bred to the same bull and used to monitor periparturient changes in DMI, ruminal capacity, and digestion and fermentation characteristics. Cows were individually fed alfalfa hay (16.0% CP, 51.3% NDF) at 130% of the average DMI of the previous 5-d period. Ruminal capacity and DM fill were measured once every 2 wk by removing the ruminal contents from each cow and filling the empty rumen with water. Dry matter intake was measured daily. Ruminal VFA, pH, NH3, and total tract DM digestibility (DMD) were measured during three 7-d periods (average of 58 d before calving, 16 d before calving, and 25 d after calving). Ruminal capacity and DM fill varied in a quadratic manner (P < .01); both were least 6 d before calving. Forage DMI (quadratic effect; P = .02) increased moderately during the prepartum period but increased dramatically after parturition. Although postpartum (d 22) ruminal capacity was only 5% greater than at 61 d before calving, postpartum DMI was 69% greater than DMI measured 61 d before calving. Indigestible ADF (IADF) passage rate changed quadratically with period (P = .01); the greatest IADF passage rate was observed 6 d before calving. Ruminal VFA (mM) also tended to change quadratically (P = .08); the highest concentrations occurred 25 d after calving. The acetate:propionate ratio declined linearly with period (P = .01). Ruminal fluid dilution rate, pH, NH3, and DMD did not change significantly over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1993

Nutritional regulation of postruminal digestive enzymes in ruminants.

Nutritional regulation of digestive enzymes has received limited study in ruminants. Comparable studies with nonruminants report adaptations occurring in pancreatic and mucosal enzyme concentrations and synthesis in response to increased consumption of carbohydrate, lipid, or protein. Adaptations in carbohydrases apparently are mediated through changes in blood glucose and insulin, and changes in lipase are mediated through changes in circulating beta-hydroxybutyrate. Increased synthesis and secretion of pancreatic proteases apparently are mediated directly through luminal effects of protein, possibly through a messenger peptide. Available information for ruminants suggests that pancreatic alpha-amylase concentration increases with increased energy intake, but not with increased carbohydrate intake, independent of energy. This result may indicate an adaptation mechanism similar to that of nonruminants, one that is mediated through increased glucose turnover, not intestinal carbohydrate supply alone. Increased intake of energy or increased intestinal supply of carbohydrates results in little or no increase in mucosal carbohydrases in the ruminant. Comparable data for effects of changing intestinal supply of protein are limited to the developing ruminant. Experiments involving lipid feeding are not available, but duodenal lipid infusion decreases pancreatic lipase secretion. Ruminant data are inadequate to predict accurately an adaptive response to feeding any diet.

Animal Nutritional Physiological Phenomena↗

PubMed1992

Dietary influences on carbohydrases and small intestinal starch hydrolysis capacity in ruminants.

Data describing the influence of diet composition and intake on amylolytic and disaccharidase activities in the ruminant small intestine are reviewed. Changing dietary components from forage to grain increased pancreatic alpha-amylase activities in most studies; however, when metabolizable energy intake was equalized, concentrations of alpha-amylase in the pancreas and the total quantities in the small intestinal lumen were greater in forage-fed than in grain-fed animals. Concentration of pancreatic alpha-amylase increased with dietary energy intake. Changing diet composition or metabolizable energy intake exerted a small effect on intestinal disaccharidase activities, with hydrolytic capacity altered principally through changes in intestinal length. Other studies suggest a small contribution of intestinal disappearance of carbohydrates to net portal appearance of glucose. The fate of large portions of intestinal carbohydrate disappearance have not been adequately defined. For the importance of intestinal carbohydrate supply to be understood, the quantity of carbohydrate undergoing both enzymatic hydrolysis and absorption must be determined.

Amylases↗

PubMed1992

Effects of exogenous emulsifiers and fat sources on nutrient digestibility, serum lipids, and growth performance in weanling pigs.

Three experiments were conducted to determine whether emulsifiers improve utilization of fat from diets for early-weaned pigs. In Exp. 1, 96 weanling pigs (17 d old) were used in metabolism cages, with main effects of fat source (soybean oil, tallow, lard, and coconut oil) and emulsifier treatment (no emulsifier, lecithin, and lysolecithin as 10% of the added fat). Soybean oil and coconut oil were more digestible than tallow and lard (P < .001). Tallow was more digestible when lecithin and lysolecithin were added (P < .007), and pigs fed lecithin had lower serum triglycerides and cholesterol than pigs fed lysolecithin (P < .03). In Exp. 2, 270 weanling pigs (21 d old) were used in a growth assay. Treatments were 1) control diet; 2) Diet 1 with soybean oil; 3) Diet 1 with tallow; 4, 5, and 6) Diet 3 with lecithin replacing 5, 10, and 30% of the tallow, respectively; and 7, 8, and 9) Diet 3 with lysolecithin replacing 5, 10, and 30% of the tallow, respectively. At d 14 of the experiment, digestibility of tallow was improved more by lecithin than lysolecithin (P < .008). For the total experiment (d 0 to 35), the control pigs had poorer gain:feed ratio than did the pigs fed the fat sources (P < .002). In Exp. 3, 420 weanling pigs (21 d old) were used. Treatments were 1) control diet with soybean oil; 2) Diet 1 with tallow; and 3, 4, and 5) Diet 2 with 10% of the added fat as soybean oil, lecithin, or monoglyceride, respectively. Adding soybean oil, lecithin, and monoglyceride to tallow increased digestibility of total fat (P < .07). From d 0 to 14, pigs fed soybean oil gained weight faster than pigs fed the other treatments (P < .06), and pigs fed tallow without emulsifiers had the lowest ADG. Considering all experiments, addition of emulsifiers increased digestibility of nutrients but had minimal effect on growth performance.

Animal Feed↗

PubMed1992

Effect of increasing ruminal butyrate on portal and hepatic nutrient flux in steers.

Six Holstein steers (mean +/- SE BW = 344 +/- 10 kg) fitted with hepatic, portal, and mesenteric vein and mesenteric artery catheters and a ruminal cannula were used in a 6 x 6 Latin square design to evaluate the effects of increasing ruminal butyrate on net portal-drained visceral and hepatic nutrient flux. Steers were fed a 40% brome hay, 60% concentrate diet in 12 portions daily at 1.25 x NEm. Water (control) or butyrate at 50, 100, 150, 200, or 250 mmol/h was supplied continuously via the ruminal cannula. Simultaneous arterial, portal, and hepatic blood samples were taken at hourly intervals from 15 to 20 h of ruminal infusion. Portal and hepatic blood flow was determined by continuous infusion of P-aminohippurate, and net nutrient flux was calculated as the difference between venous and arterial concentrations times blood flow. Ruminal and arterial concentrations and total splanchnic flux of butyrate increased (P less than .01) with increased butyrate infusion. Arterial concentrations of acetate (P less than .10), alpha-amino-N (P less than .05), and glucose (P less than .01) decreased with increased butyrate, whereas arterial beta-hydroxybutyrate (P less than .01) and acetoacetate (P less than .05) increased. Increased butyrate produced an increased portal-drained visceral flux of acetoacetate and an increased net hepatic flux of beta-hydroxybutyrate. Urea N and glucose net portal and hepatic fluxes were not affected by ruminal butyrate. Alpha-amino-N uptake by the liver decreased with increased butyrate (P less than .10). Simple linear regression (r2 = .985) indicated that 25.8% of ruminally infused butyrate appeared in portal blood as butyrate. Only 14% could be accounted for as net portal-drained visceral flux of acetoacetate plus beta-hydroxybutyrate.

Ammonia↗

PubMed1992

Impact of nutrition on pancreatic exocrine and endocrine secretion in ruminants: a review.

Because of the unique features of the ruminant digestive system, variations in diet composition and intake produce dramatic changes in ruminal fermentation. Optimizing nutritional management requires an understanding of how these variations and changes influence digestion and metabolism. Although the pancreas plays a central role in digestion and subsequent nutrient metabolism, relatively little is known about pancreatic adaptation to nutritional changes in the ruminant. Increasing starch intake has been suggested to increase pancreatic alpha-amylase; however, recent work suggests that dietary energy per se may drive these changes, and interactions with other nutrients, such as protein, may exist. Studies describing the influence of altered protein and lipid intakes on pancreatic adaptation in ruminants are lacking. Pancreatic secretion of both insulin and glucagon respond to the intravenous infusion of VFA in a dramatic fashion; however, feeding studies suggest that the influence of VFA on insulin and glucagon may be more subtle. Interactions exist between stimulatory signals and physiological state, such as lactation. Assessment of pancreatic endocrine secretion is further complicated by a variable removal of insulin and glucagon by hepatic tissues. These studies point out that pancreatic hormone secretion is controlled by integrated and complex mechanisms. Studies of these controlling mechanisms should consider the entire array to more fully understand hormone secretion.

Animal Nutritional Physiological Phenomena↗

PubMed1992

Collection of pancreatic exocrine secretions by formation of a duodenal pouch in cattle.

Collection of exocrine pancreatic secretions from cattle by use of a single-unit cannula was performed. The major advantage of the cannula was simple technical management. A small pouch of the duodenum into which the major pancreatic duct drains was formed. Continuity of the duodenum was reestablished by end-to-end anastomosis. A side arm of the cannula was inserted into the pouch to collect exocrine secretions, and the main portion of the cannula was placed cranial to the anastomosis to return pancreatic secretions to the small intestine between collection periods. The accessory pancreatic duct was ligated in 2 of 4 cattle to evaluate possible secretory contribution from this source. All cattle remained healthy after cannulation, and cattle gained approximately 100 kg of body weight in the 5 months after surgery. The mean secretory rate for exocrine pancreatic secretion in cattle was 106 +/- 6.8 ml/h. There was no effect of feeding on the pattern of secretion nor were there significant differences between cattle. A fistula formed between the pouch and duodenum approximately 120 days after surgery in the first 2 cattle used. Development of fistulas was prevented for 300 days in subsequently prepared cattle by use of surgical mesh around the cannulas, leading to functional cannulation sites. Preparation of a duodenal pouch appeared useful for long-term studies of pancreatic exocrine secretion in cattle.

Animals↗

PubMed1991

Effects of calcium soaps of fatty acids on postpartum reproductive function in beef cows.

Twelve multiparous Simmental cows (584 kg) were used to determine the influence of calcium soaps of fatty acids (CSFA) incorporated in a range supplement on postpartum reproductive characteristics. Cows were assigned randomly to receive a control [C; containing grain sorghum (GS) and soybean meal (SBM)] or CSFA-based (containing Megalac [a source of CSFA], GS, and SBM) supplement. Supplements plus prairie hay were individually fed. Diets were isonitrogenous and met the NEm requirement for heavy-milking beef cows in early lactation. Supplement feeding and daily blood collection began at parturition. Calves were removed permanently from cows at 25 +/- 2 d postpartum. Duration of first postpartum estrous cycles was determined by both visual observations and changes in concentrations of progesterone in serum. Concentrations of LH in serum (15-min intervals for 6 h) were determined 12 h before and 48 and 96 h after calf removal. Concentrations of progesterone and estradiol-17 beta in serum were determined daily. Cows receiving CSFA had higher (P = .06) mean concentrations of LH than those receiving C (1.47 vs 1.12 +/- .13 ng/ml). Concentrations of estradiol-17 beta were lower (P less than .02) and serum progesterone were higher (P less than .02) between d 6 and 8 of the induced cycle in CSFA-fed cows. Plasma cholesterol was greater (P less than .01) in cows fed CSFA although plasma triglyceride concentrations were similar between treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Anestrus↗

PubMed1991

Influence of dietary forage and energy intake on metabolism and acyl-CoA synthetase activity in bovine ruminal epithelial tissue.

Twenty calves (7 mo old) were blocked by breed, sex, and weight into five groups of four calves and randomly assigned to either a 90% forage (alfalfa) or a 90% grain (50% sorghum and 50% wheat) diet fed at one (1M) or two (2M) times NEm for 140 d. Samples of ruminal epithelial tissue were collected from the anterior ventral sac, and papillae were cut free by hand and used for in vitro incubations and acyl-CoA synthetase assays. Substrates were acetate (90 mM), propionate (60 mM), butyrate (30 mM), and glucose (20 mM). Net productions of beta-hydroxybutyrate and acetoacetate from acetate were greater (P less than .01) with the 2M feeding; however, 14CO2 production from acetate was greater (P less than .05) with the grain diet. Net production of lactate (P = .09) and pyruvate (P less than .01) from propionate increased with the 2M feeding, whereas net lactate production from glucose decreased (P less than .01). Uptakes of VFA were similar with 1M and 2M feeding and were about 10-fold greater than uptakes of glucose. Production of 14CO2 from propionate was two- to fivefold greater than from acetate, butyrate, or glucose. Oxygen consumption was greater (P less than .01) with 2M feeding and unaffected by substrate. Activities of butyryl-CoA synthetase (nmol.mg of tissue-1.h-1) were greater (P less than .05) for animals consuming the forage diets. Addition of butyrate inhibited acetyl- and propionyl-CoA synthetase activity by 63 and 92%, respectively for all dietary treatments. Overall, metabolism of ruminal epithelial tissue tended to increase with the 2M feeding. Influence of dietary forage content on metabolism and activity of acyl-CoA synthetases was minimal, but the high-forage diet caused slight increases.

Animal Feed↗

PubMed1991

Technical note: effectiveness of different methods of continuous marker administration for estimating fecal output.

Six ruminally fistulated crossbred steers (BW = 369 kg) were used in a randomized complete block experiment to test the efficacy of continuous-infusion pumps and controlled-release boluses for administering external markers to predict fecal output. Steers, limit-fed chopped alfalfa hay at 2% of BW daily, were fitted with continuous-infusion pumps that administered Co-EDTA and YbCl3 solutions intraruminally. In addition, a controlled-release bolus containing Cr2O3 was inserted into the rumen of each steer. Fecal grab samples were taken every 6 h for 7 d during initial marker equilibration; after this period, fecal grab samples were taken every 3 h for 48 h to evaluate diurnal variation patterns. Steers were subsequently fitted with fecal bags for 7 d to allow total fecal collection. Grab samples also were taken during the total fecal collection period at 0600 (AM) and 1400 (PM). The marker X time effect was nonsignificant. Similarly, time of grab sampling (AM or PM) did not affect estimates of fecal output (P greater than .10), but the Cr2O3 bolus overestimated fecal output (P less than .05). Fecal marker concentrations during the 48-h profile showed little diurnal variation regardless of marker used. All markers equilibrated in the feces at approximately 100 to 120 h after initiating infusions. The continuous-infusion pumps evaluated were efficacious for administering markers for estimating total fecal output in limit-fed steers; however, the Cr2O3 boluses evaluated overestimated fecal output when the manufacturer's suggested release rate was used for fecal output calculations.

Animals↗