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PubMed1992

Effects of source and level of dietary neutral detergent fiber on feed intake, ruminal fermentation, ruminal digestion in situ, and total tract digestion in beef cattle fed pelleted concentrates with or without supplemental roughage.

The effects of source and level of dietary NDF on intake, ruminal digestion in situ, ruminal fermentation, and total tract digestion were evaluated in Hereford steers using a replicated 5 x 5 Latin square design. Diets contained 62 to 64% TDN and included 1) 80% control concentrate (contained pelleted ground grains) and 20% timothy hay (traditional diet), 2) 80% control concentrate and 20% alfalfa cubes, 3) 90% control concentrate and 10% cubes, 4) a completely pelleted diet using corn cobs as the primary NDF source, and 5) 80% textured (rolled instead of ground grains) concentrate and 20% hay. Dry matter intake differed (P less than .05) between the traditional and cube diets due to limited acceptance of alfalfa cubes. Increased (P less than .05) ruminal osmolality, total VFA, and NH3 N and lower (P less than .01) ruminal pH in steers fed corn cob and cube diets relative to steers fed the traditional diet were due to preferential consumption of concentrate over supplemental roughage and the resultant rapid fermentation of concentrates. Potentially degradable DM in the traditional diet exceeded (P less than .06) all other diets, resulting in the increased (P less than .10) extent of DM disappearance despite a slower (P less than .05) rate of DM disappearance. Rate of NDF disappearance and all in situ starch disappearance parameters were similar between the traditional, corn cob, and cube diets. All ruminal digestion parameters involving NDF disappearance were similar between hay diets and between cube diets, whereas rate and extent of starch disappearance differed (P less than .05) between hay diets. Although formulation of diets with different sources of dietary NDF did not affect total tract digestion of nutrients, nutrient availability and ruminal fermentation were altered due to dietary differences in sources of dietary NDF and preferential selection of feedstuffs by steers.

Ammonia↗
PubMed1999

Effects of level of feeding and ruminally undegraded protein on ruminal bacterial protein synthesis, escape of dietary protein, intestinal amino acid profile, and performance of dairy cows.

Six cannulated lactating cows were used in two replicated, concurrently run 3 x 3 Latin square experiment to study the interaction between level of feeding and diets differing in ruminally undegraded protein (RUP) on bacterial protein synthesis, ruminal escape of dietary protein, and flow of total and individual amino acids (AA) to the small intestine. Treatments consisted of three diets formulated to contain 69 g (HL), 53 g (HH), and 48 g (LL) of RUP per kilogram of DM, respectively. Measurements were made in early lactation, at high feeding level (19.3 kg DM/d), and repeated at late lactation (9.8 kg DM/d, low feeding level) with the same animals and diets. Decreasing feed intake increased (P < .05) the apparent digestibility of OM, NDF, and ADF in the rumen and the total tract, decreased (P < .05) ruminal liquid and particulate passage rate and total ruminal VFA concentration, and increased ruminal pH and ammonia concentration. Decreased level of intake reduced the (P < .05) efficiency of bacterial N synthesis (28.1 vs 23.7 g bacterial N/kg OM truly digested in the rumen) and decreased (P < .05) ruminal protein degradation rate measured with an in situ method. Duodenal flow of nonammonia nitrogen (NAN), and total AA were highest (P < .05) for the HL diet and lowest (P < .05) for the LL diet at the high feeding level. However, at the low feeding level, diet composition did not affect the amount of NAN or total AA passing to the small intestine. Diet HL increased the proportion of Met, His (P < .05), and Arg (P < .07) in the duodenal digesta at both feeding levels. When purines were used to calculate bacterial N synthesis, no differences between diets were detected. However, when diaminopimelic acid was used, highest bacterial N synthesis was detected for diet HH at the high feeding level. Diet HL supported the highest (P < .05) milk protein production at the high feeding level, and the highest (P < .05) milk protein content at the low feeding level. In conclusion, level of feeding and amount of RUP altered the amount and composition of AA presented to the cows.

Amino Acids↗
PubMed1989

The effects of ruminal escape protein or fat on ruminal characteristics of pregnant winter-grazing beef cows.

The effects of ruminal escape protein and added fat on ruminal characteristics were determined at 9, 4 and 1 wk prior to calving in 20 prepartum beef cows. Cows grazed native foothills range from mid-December to early March in two different years. Cows were randomly allotted to five groups (four cows per group) and fed (g/d) either no supplement (control); 570 soybean meal (SOY); 450 soybean meal and 230 blood meal (SOY+BM); 140 soybean meal, 16 urea and 450 corn gluten mean (SOY+CGM); or 570 soybean meal and 210 animal fat (SOY+FAT). Supplements were designed to supply similar quantities of ruminally degraded protein while varying in escape protein quantity and source (SOY+BM and SOY+CGM). Control animals had the lowest (P less than .03) ruminal ammonia concentration (4.5 to 8.9 mg/dl), but values were similar (8.1 to 12.3 mg/dl) for the other treatments. In both trials, NDF disappearance rate was lowest for the control, 1.85%/h (P less than .01), and tended to be lower (P less than .07) in SOY (2.25%/h) than for the mean of SOY+BM and SOY+CGM (2.62 and 2.84%/h). Ruminal fluid volume tended to be greater (P less than .14) and dilution rate lower (P less than .13) for the mean of SOY+BM and SOY+CGM than for SOY in both trials. Particulate dilution rate was lower (P less than .01) for the mean of SOY+BM and SOY+CGM (2.33 and 2.75%/h) than for SOY+FAT (3.17%/h) in Trial 2. These results indicate that supplemental escape protein from blood meal or corn gluten meal can influence ruminal characteristics, perhaps due to a continuous release of amino acids and(or) branched-chain organic acids.

Ammonia↗
PubMed2004

Effects of monensin on ruminal forage degradability and total tract diet digestibility in lactating dairy cows during grain-induced subacute ruminal acidosis.

The effects of monensin premix supplementation on ruminal pH characteristics and forage degradability, and total tract diet digestibility during grain-induced subacute ruminal acidosis (SARA) in lactating dairy cows receiving a total mixed ration were investigated. Six multiparous, rumen-fistulated Holstein cows were used in a 2-treatment, 2-period (5 wk per period) crossover design. During wk 5 (d 29 to 35) of each period, SARA was induced using a grain challenge model, and ruminal pH was measured continuously using indwelling pH probes. Ruminal degradation of corn silage and alfalfa haylage was determined using the in situ (nylon bag) technique, and total tract diet digestibility was determined by total fecal collection during wk 5. Monensin supplementation did not affect dry matter intake, milk yield, and composition, and ruminal pH characteristics under these experimentally induced SARA conditions. Rates of ruminal forage fiber degradability were similar between control and monensin-treated cows; however, monensin supplementation increased total tract fiber digestion. This study indicates that monensin altered total tract nutrient digestion by increasing fiber digestion at postruminal sites.

Acidosis↗
PubMed1993

Controlled ruminal infusion of sodium bicarbonate. 3. Influence of infusion dose on systemic acid-base status, minerals, and ruminal milieu.

Four ruminally cannulated, lactating Holstein cows were assigned to a 4 x 4 Latin square to monitor effects of intraruminal NaHCO3 infusion on temporal changes in ruminal and systemic acid-base status and mineral metabolism. Twice daily from 2 to 4 h postfeeding, cows were infused with 0, 110, 220, or 330 g of NaHCO3 dissolved in 3.8 L of water. All cows had access to their TMR of sorghum silage and concentrate (35: 65, DM basis) for 2 h twice daily. Ruminal fluid, blood, and urine were collected at feeding and every 30 min postfeeding for 12 h on the last day of each 14-d period. Total urine volume also was measured during this interval. Infusion of buffer increased ruminal fluid buffering capacity transiently at 4.5 h postfeeding but otherwise did not markedly affect ruminal fluid acid-base status. Systemic acid-base status was unaffected by the buffer primarily because renal excretion of base successfully reduced systemic base load. Urine volume increased in response to NaHCO3 infusion. Buffer infusion increased urinary excretion of Na, Mg, and K but decreased Ca excretion for 12 h postfeeding; Cl excretion was not affected. Buffer infusion tended to increase total VFA in ruminal fluid. Our data indicate that homeostatic mechanisms can eliminate exogenous base via the kidneys; hence, acid-base status was not perturbed by infusion of NaHCO3. The increased excretion of Mg and K with buffer infusion indicates that the dietary requirements for these minerals may be increased by NaHCO3. Although loss of Ca through the urine was reduced by buffer infusion, this reduction may indicate reduced availability of Ca to the cow. The diuresis accompanying large doses of NaHCO3 may increase dietary requirements for some minerals.

Acid-Base Equilibrium↗
PubMed1991

Ostertagia ostertagi in neonatal calves: establishment of infection in ruminating and non-ruminating calves.

An experiment was carried out to study the role of the ruminal function in the establishment of Ostertagia ostertagi in neonatal calves. Three groups of calves were fed either milk only (groups A and C), or hay and concentrate in addition to milk (group B) from birth. At the time of infection, ruminal function was negligible in groups A and C, whereas it was well developed in group B. Calves of groups A and B were each given 25,000 normal ensheathed infective larvae of O ostertagi and those of group C were given 25,000 infective larvae exsheathed in vitro. Daily faecal egg output and post mortem worm counts 28 days after infection were higher in calves with well developed ruminal function than those having only negligible ruminal function. In the latter group, exsheathed larvae established at a lower rate than did ensheathed larvae. The results suggest that the degree of development of the ruminal function influences the establishment of O ostertagi.

Abomasum↗
PubMed1992

Expression of R-3-hydroxybutyrate dehydrogenase, a ketone body converting enzyme in heart and liver mitochondria of ruminant and non-ruminant mammals.

1. The properties of rat liver and bovine heart R-3-hydroxybutyrate dehydrogenase (BDH) have been extensively studied in the past 20 years, but little is known concerning the biogenesis and the regulation of this dehydrogenase over different species. 2. In addition, controversial results were often reported concerning the activity, the level and the subcellular location of this enzyme in ruminants. 3. BDH activity found in liver and kidney mitochondria from ruminants (cow and sheep) is low, while it is much higher in rat. 4. However, the enzyme activity is detected in microsomes and in cytosol of liver and of kidney cells from ruminants. These activities are not correlated to ketonaemia level. 5. Although low BDH activity is detected in liver mitochondria from ruminants; the bovine liver BDH gene seems to be translated since BDH can be immunodetected by using an antiserum raised against bovine heart BDH. 6. Beside this, the good cross-reactivity between heart BDH and liver BDH suggests their high level of homology in ruminants.

Animals↗
PubMed1999

Why ruminators are poor problem solvers: clues from the phenomenology of dysphoric rumination.

The phenomenology of dysphoric rumination and its consequences for problem solving were explored in 3 studies. In Study 1, self-focused rumination, compared with distraction, led dysphoric participants to rate their own biggest problems as severe and unsolvable and to report a reduced likelihood of actually implementing their solutions. Clues into the mechanisms behind these findings were explored in Study 2. The results showed that dysphoric ruminative thought is characterized by a focus on personal problems combined with a negative tone, self-criticism, and self-blame for problems as well as reduced self-confidence, optimism, and perceived control. Finally, Study 3 revealed a direct relationship between the negatively biased content of ruminative thoughts and reduced willingness to solve one's problems. Implications of these findings for the consequences of self-focused rumination are discussed.

Adult↗
PubMed1975

[Studies of the influence of nutritional factors on the ruminal mucosa. 1. Structure and functional state of the ruminal mucosa after feeding of extreme rations and abrupt change in nutrition].

Different rations were used in successive experimental periods (Dried green feeds (I), fresh green feed from sugar beet tops (II), concentrates (III, IV), and maize silage (V), to test the effect they have on the structure and oxidative functions of the ruminal mucosa in cattle. Rations I, II, IV, and V were both energy and protein equivalent. Biopsy specimens from ruminal papillae were taken on the day when rations were suddenly changed and on the 21st and 22nd day of the feeding period; they were then investigated histologically and manometrically. It was found that some characteristics, (viz. the type and thickness of the stratum corneum, the thickness of epithelia, the size of cell nuclei in the stratum basale of the epitheliumas well as the state of the lamina propria and the oxygen uptake were subject to alterations depending on nutrition. Nutrition with energy-equivalent, but otherwise extremely different diets representing particular types of rations led to the development of different and quite specific functional states of the ruminal mucosa. All these functional states of the mucosa were found to be within the limits of normality but seemed to have a definitely more favourable functional effect in the case of rations I and IV than in the case of rations II and V. The feeding of concentrates (III, V) increased the energy intake to an amount of 6.6 kEFr, i.e. double that of the other rations, and brought about changes in quantitative parameters. These, in turn, indicated that proliferative and oxidative processes had been stimulated. Changes of this kind were accompanied by increases in the concentration of volatile fatty acids in the ruminal fluid which rose from a maximum of 9 mMol per 100 ml (ration IV) to 12.5 mMol per 100 ml (ration III). Immediately after any change in nutrition brought about by a change of rations, processes of adaptation occurred in the ruminal mucosa. A balanced state of the mucosa was again achieved after a period of not more than 3 weeks.

Animal Feed↗
PubMed1991

Comparison of growth characteristics of anaerobic fungi isolated from ruminant and non-ruminant herbivores during cultivation in a defined medium.

Anaerobic fungi were isolated from rumen fluid of a domestic sheep (Ovis aries; a ruminant) and from faeces of five non-ruminants: African elephant (Loxodonta africana), black rhinoceros (Diceros bicornis), Indian rhinoceros (Rhinoceros unicornis), Indian elephant (Elephas maximus) and mara (Dolichotis patagonum). The anaerobic fungus isolated from the sheep was a Neocallimastix species and the isolates from non-ruminants were all species similar to Piromyces spp. A defined medium is described which supported growth of all the isolates, and was used to examine growth characteristics of the different strains. For each fungus the lipid phosphate content was determined after growth on cellobiose and the resulting values were used to estimate fungal biomass after growth on solid substrates. The ability of isolates from ruminants and non-ruminants to digest both wheat straw and cellulose was comparable. More than 90% and 60%, respectively, of filter paper cellulose and wheat straw were digested by most strains within 60-78 h. Growth of two fungi, isolated from rumen fluid of a sheep (Neocallimastix strain N1) and from faeces of an Indian rhinoceros (Piromyces strain R1), on cellobiose was studied in detail. Fungal growth yields on cellobiose were 64.1 g (mol substrate)-1 for N1 and 34.2 g mol-1 for R1. The major fermentation products of both strains were formate, lactate, acetate, ethanol and hydrogen.

Anaerobiosis↗
PubMed1993

Influence of ruminal protozoa on site and extent of starch digestion and ruminal fermentation.

Eight ruminally, duodenally, and ileally fistulated sheep were used to study the effects of protozoa on ruminal fermentation and starch digestion in the rumen and intestines. The experimental diet (75% grain DM basis) was based on a mixture of 67% high-moisture corn (HMC) and 33% dry-rolled grain sorghum (DRGS). Protozoa were reduced from 51,286 to 13,987 organisms/mL of ruminal fluid by feeding a diet (13 d) containing 9% tallow and monensin at 27 mg/kg (DM basis). Three sheep were defaunated by intraruminal infusions of lactic acid (20 to 30 g/d) and one sheep by washing the rumen and heating ruminal contents (60 degrees C for 20 min). No differences were observed in DM or starch intake, ruminal fluid pH, lactate concentration, or total tract starch digestibility. Molar proportion of acetate was reduced (48.6 vs 58.3%; P < .01) and propionate was increased (32.2 vs 23.4%; P < .03) by defaunation. Total VFA tended (P = .20) to be lower in faunated sheep (118.5 vs 139.2 mM). In situ rate of starch digestion of HMC (22.3 vs 14.7 %/h; P < .02) and DRGS (5.1 vs 3.3 %/h; P < .009) was increased by defaunation. Starch digestibility (percentage of intake) in the rumen was increased (P < .001) by defaunation (84.2 vs 93.7%) and was reduced (P < .002) in the small intestine (5.2 vs 13.6%). Defaunation increased (P < .03) amylolytic activity (.40 vs .17 units/mg of protein; P < .03) and osmotic pressure (321 vs 245 mOsm/kg; P < .006).(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗
PubMed1997

Ardacin for steers grazing endophyte-free fescue pasture: effects on live weight gain, forage intake, nitrogen and fiber digestion, ruminal fluid kinetics, ruminal fermentation, and serum hormones and metabolites.

Growth and digestion studies were conducted to evaluate the use of ardacin as a feedgrade antibiotic for enhancing digestive function and growth in grazing steers. In Exp. 1, 90 yearling steers (average initial BW of 248 kg) used in a randomized complete block design (block = weight group) grazed fescue pasture without supplementation (CON) or with daily supplements (DM basis) of .4% of BW supplemental ground corn (CRN) or .4% of BW supplemental corn supplying 120 mg of ardacin (ARD). In Exp. 2, 12 ruminally and duodenally cannulated steers and three ruminally cannulated steers (Hereford x Angus; average BW of 347 kg) were used to evaluate the effects of the same supplements used in Exp. 1 on ruminal fermentation and digestion. In Exp. 1, ARD-supplemented steers weighed more (P < .01) at the conclusion of the study than CRN steers, which together weighed more (P < .01) than CON steers. Average daily gain was greater (P < .10) in supplemented than in CON steers; ARD steers had greater (P < .01) ADG than CRN steers. In Exp. 2, forage intake and harvesting efficiency did not vary (P > .10) with supplementation or type of supplement, but total intake reflected (P = .03) the addition of corn to the forage diet. Addition of ardacin increased (P = .02) ruminal pH compared with CRN steers. Ardacin decreased ruminal molar proportions of acetate and increased (P = .01) propionate proportions when compared with CRN steers. Total tract N digestibility was affected (P < .10) by supplementation and by addition of ardacin to the diet. Addition of ardacin to the ground corn supplement increased ADG, in part by enhancing acetate:propionate ratios and increasing N digestion.

Aminoglycosides↗
PubMed1987

Simultaneous measures of rates of ruminal digestion and passage of feeds for prediction of ruminal nitrogen and dry matter digestion in lactating dairy cows.

Three ruminal-cannulated Holstein cows in early lactation were fed three diets, each containing different energy and protein supplements in two consecutive 3 X 3 Latin squares. Each supplement contained a combination of three different feedstuffs (ground corn, soybean meal and wheat mids; corn gluten feed, rolled oats and distiller's dried grains; ground barley, brewer's grains and cottonseed meal). Diets consisted of 30% corn silage, 10% alfalfa hay, 10% alfalfa haylage, 17.7% ground corn plus minerals and vitamins, with the remainder as supplemental feedstuffs individually marked for measurement of ruminal turnover and in situ digestion rates. An extra period at the end of each Latin square was used to measure ruminal turnover and in situ digestion of individual forages. Diet had no effect on dry matter intake or milk yield. Mean fractional turnover (per hour) rate, measured by labeling feedstuffs with cerium, samarium or lanthanum was .044, .048, .049, .043, .047, .046, .050, .047, .049, .037, .046 and .045 for corn, soybean meal, wheat mids, corn gluten feed, oats, distiller's dried grains with solubles, barley, brewer's dried grains, cottonseed meal, alfalfa hay, corn silage and alfalfa haylage (P greater than .1), respectively. In situ-predicted ruminal degradation of N weighted for rate of passage was 61.4, 67.0, 81.5, 74.8, 86.3, 71.0, 75.7, 52.1, 54.2, 60.8, 71.7 and 70.9% for respective feedstuffs (P less than .05). In comparison with mean literature values for in vivo-measured N degradability, mean literature value = 1.172 (in situ predicted) -9.73 (P less than .05, R2 = .51). Results are interpreted to indicate a tendency for overestimating ruminal N degradability by in situ methods in feedstuffs of low degradability, while underestimating degradability in more highly degraded feedstuffs. Estimates were 11 to 17 percentage units lower than literature values for alfalfa hay and haylage and 17 units lower than literature values for distiller's dried grains.

Animal Feed↗
PubMed1984

Effect of sodium bicarbonate and disodium phosphate on animal performance, ruminal metabolism, digestion, and rate of passage in ruminating calves.

With a five-point radial response design, a control group, and several single factor points, effects of dietary sodium bicarbonate (0 to 4.5%) and disodium phosphate (0 to 2.0%) on calf growth, ruminal fermentation, ration digestibility, and rate of passage of liquid and particulate digesta were studied. Growth and intake data were collected age 7 to 14 wk. Rumen and blood were sampled three times. Digestion and rate of passage trials were during age 16 wk. Gains were not affected significantly but were maximized between 1 and 2% sodium bicarbonate and 0% disodium phosphate. Dry matter intake, feed efficiency, dry matter digestibility, volatile fatty acid ratio, ruminal pH, and buffering capacity were not altered by buffers. Ruminal osmolality and concentration of volatile fatty acids were increased by buffers. Digestibility of acid detergent fiber and neutral detergent fiber tended to be higher for rations containing buffers. Dilution rate of ruminal liquid increased by 40% with 2.0% sodium bicarbonate and .75% disodium phosphate, and ruminal volume was decreased. Passage rate of particulate digesta was increased by a similar amount.

Animals↗
PubMed1995

Effects of ruminal versus duodenal dosing of fish meal on ruminal fermentation and milk composition.

Three midlactation Holstein cows with ruminal and duodenal cannulas were used in a 3 x 3 Latin square design to determine whether ruminal or postruminal alterations in metabolism were responsible for the changes in milk composition that frequently are associated with dietary fish meal. Cows were offered a diet of 60:40 forage to concentrate (aliquots at 6-h intervals) that was supplemented with isonitrogenous amounts of soybean meal (1.3 kg of DM/d) dosed into the rumen or fish meal (1.0 kg DM/d) dosed either into the rumen or into the duodenum. The DMI, ruminal NDF digestion, and flows of total N and microbial N to the duodenum decreased for cows receiving fish meal. Dietary N flow increased when fish meal was dosed into the rumen. Total concentration of ruminal VFA was greater for cows receiving the soybean meal treatment; however, treatment had no effect on the ratio of ruminal acetate plus butyrate to propionate. Milk and FCM yields were unaffected by treatment, but milk fat content decreased, and milk protein content increased when cows were supplemented with fish meal. The difference in mammary arteriovenous glucose difference decreased when cows were dosed with fish meal. Changes in plasma NEFA and triglycerides were small and inconsistent. Results from this experiment suggest that effects of fish meal on milk composition are due to postruminal alterations in metabolism.

Acetates↗
PubMed2005

Distinct modes of ruminative self-focus: impact of abstract versus concrete rumination on problem solving in depression.

One account for the negative effects of rumination on social problem solving (SPS) is the symptom-focus hypothesis, which proposes that focus on symptoms amplifies the vicious cycle between depressed mood and negative cognition. The authors tested a contrasting account, the reduced concreteness hypothesis, which postulates that the abstract thinking typical of rumination impairs SPS. In 40 depressed patients and 40 never-depressed controls, SPS was assessed before and after versions of symptom-focused rumination known to differentially induce abstract versus concrete self-focus (E. Watkins & J. D. Teasdale, 2001). As predicted by reduced concreteness theory, relative to abstract self-focus, concrete self-focus improved SPS in depressed patients, suggesting that the particular mode of symptom-focus, rather than symptom-focus per se, determines the effects of rumination on problem solving.

Adult↗
PubMed2005

Influence of supplemental endoglucanase or xylanase on volatile fatty acid production from ruminant feed by ruminal in vitro cultures.

This study employed two commercial enzyme preparations to examine the effects of endoglucanase, xylanase or their combination on in vitro volatile fatty acid (VFA) production by ruminal microbial populations. Batch ruminal cultures were established with one of various feedstuffs or with a fescue hay-based diet and ruminal fluid from a heifer fed a 40% forage:60% concentrate diet. Addition of xylanase at 135 xylanase units (XU) per ml increased total VFA production from the fescue hay-based diet (44.3 vs. 57.2 mM, p < 0.05) without changing the acetate to propionate (A:P) ratio. Addition of endoglucanase at 2, 3, 4, and 5 carboxymethyl cellulase units (CMCU) per ml increased total VFA production from the fescue hay-based diet on average by 36% (p < 0.05). Addition of 3, 4 and 5 CMCU/ml also decreased (p < 0.05) the A:P ratio. The combined addition of xylanase (135 XU/ml) and endoglucanase (5 CMCU/ml) increased total VFA production from the fescue hay-based diet (40.9 vs. 61.5 mM, p < 0.05) and reduced the A:P ratio (3.4 vs. 1.5, p < 0.05). The effects of endoglucanase and xylanase supplementation on in vitro VFA production varied across the various substrates used. However, endoglucanase supplementation consistently reduced the A:P ratio with all substrates tested. The effects of the enzyme combination were generally greater than either enzyme alone. We conclude that endoglucanase and xylanase activities differ in their ability to affect ruminal VFA production, and endoglucanase but not xylanase, may improve fermentation efficiency by reducing the A:P ratio.

Animal Feed↗
PubMed1988

Dopamine-sensitive receptors that evoke rumination and modify reticulo-ruminal activity in sheep.

Dopamine (20 micrograms/kg) evoked rumination in sheep when injected as a bolus into the coeliac artery or into the left gastric artery but not when injected into the carotid artery. A mixed alpha-adrenoreceptor antagonist (phentolamine) and an alpha 2-adrenoreceptor antagonist (yohimbine) prevented dopamine from evoking rumination, but a dopaminergic antagonist (metoclopramide) did not. These findings suggest that dopamine stimulated rumination by acting upon alpha 2-adrenoreceptors situated in the area supplied by the left gastric artery, whereas dopamine injected intracerebrally may have evoked rumination by an alpha 2-adrenoreceptor effect in the central nervous system (Bueno et al., 1983) and the actions of intrajugular dopamine were exclusively upon peripheral adrenoreceptors located specifically in the gastric area. Dopamine (1 microgram/kg/min) infused into the carotid artery reduced the frequency of reticular contractions by acting upon a centrally located dopaminergic receptor mechanism sensitive to metoclopramide but not to phentolamine. When dopamine was infused into the coeliac artery or into the left gastric artery, the amplitude of reticular contractions was reduced by a peripheral mechanism sensitive both to metoclopramide and to phentolamine. Dopamine also reduced the amplitude of reticular contractions when infused into the carotid artery but to a lesser degree than when given into the coeliac or left gastric artery.

Animals↗