The primary-secondary rumen contraction and gas expulsion in sheep (Ovis aries)

1. Sheep rumens were insufflated with nitrogen to 5, 10, 15 and 20 cm HOH pressure and sustained at each pressure for 5 min. 2. Measurements included rumen motility, reticulorumen myoelectrical activity, eructation frequency and volume, and changes in tracheal pressure. 3. Associated with elevated intrarumen pressure was a previously unreported type of rumen contraction on which gas expulsion occurred, the primary-secondary contraction. 4. Gas expulsion volume was similar on primary-secondary and secondary contractions. 5. The maximum rumen contraction rate per min was 4-5 for secondaries and 1-2 for primary-secondaries. 6. Irrespective of the sustained initial pressure, resting intrarumen pressure was reached within 5 min.     

Pressure profile along the oesophagus during eructation in sheep.

The pressure profile along the oesophagus was recorded simultaneously with the flow rate of eructated gas in sheep to evaluate the oesophageal motor events leading to the relief of gas. All the eructation sequences started by a rise followed by a plateau of oesophageal pressure. The passage of gas at the tracheal level occurred during this plateau and not during the consecutive transient lowering of the oesophageal pressure. All eructation sequences ended by a peristaltic contraction of the oesophagus. The flow rate pattern of gas during eructation was affected by head position leading to different tensions of the oesophagus. We conclude that, despite the large volume of eructated gases, the eructation process is not significantly different in sheep compared to other animals. Therefore, by virtue of its unique physiological particularity, the sheep might be used as an experimental model for the evaluation of lower oesophageal sphincter (LOS) competence.     

The effect of elevation of intrarumen pressure by nitrogen insufflation on eructation in cattle (Bos taurus)

• 1.1. The in trarumen pressure (IRP) of eight calves was elevated for 10 min by nitrogen insufflation to pressures of 5, 10, 15 and 20 cm H₂O.
• 2.2. Rumen motility was evaluated by recording reticulorumen myoelectrical activity and changes in luminal pressure, while eructation was determined from anterior tracheal and face mask gas expulsion.
• 3.3. The elevation of IRP increased primary rumen contraction frequency slightly and secondary rumen contraction frequency as much as 3-fold.
• 4.4. Rumen gas was expelled only during rumen contractions and virtually always during secondary rumen contractions.
• 5.5. Cattle do not exhibit the primary-secondary contraction previously identified in sheep and their rumen motility appears to be less sensitive than sheep to increases in IRP.

     

Alternative temperate forages containing secondary compounds for improving sustainable productivity in grazing ruminants

The use of alternative temperate forages to improve the sustainable productivity of grazing ruminants, relative to grass-based pastures, is reviewed. Particular emphasis is placed upon forages containing secondary compounds for sustainable control of internal parasites, for increasing reproductive rate in sheep, reducing bloat risk in cattle and for reducing methane production as a means of lowering greenhouse gas emissions.

Of the forages reviewed, the herb chicory (Chicorium intybus) and the condensed tannin-containing legumes Lotus corniculatus L. and sulla (Hedysarum coronarium) offered the most advantages. Chicory and sulla promoted faster growth rates in young sheep and deer in the presence of internal parasites, and showed reduced methane production in other studies. L. corniculatus was not as effective as chicory and sulla in promoting growth of lambs in the presence of internal parasites. Grazing on L. corniculatus was associated with increases in reproductive rate in sheep, increases in milk production in both ewes and dairy cows and reduced methane production, effects that were mainly due to its content of condensed tannins (CT). Grazing ewes on L. corniculatus during mating and very early pregnancy may also reduce lamb mortality. However, there are no data on the effect of mating ewes, which are grazing chicory on their reproductive performance, an important omission. Risk of rumen frothy bloat in cattle grazing legumes is reduced when the forage contains 5 g CT/kg dry matter (DM) or greater. Gene transfer techniques aimed at achieving this for lucerne (Medicago sativa) have made progress, but CT concentration needs to be further increased from calculated values of 0.75–1.25 g CT/kg DM in the transformed plants. Bloat control may be achievable in genetically transformed legumes before increased amino acid absorption, as the concentration of CT required for bloat control is lower (5 versus 30–40 g/kg DM) than that required to cause increased amino acid absorption and is not affected by differences in CT structure.

Key plant characteristics for improved sustainable productivity are a high ratio of readily fermentable: structural carbohydrate and the presence of CT and certain other secondary compounds.

Taking into account both nutritional and agronomic considerations, chicory is considered one of the best emerging plants for grazing livestock, with L. corniculatus being more suitable for areas with dry summers and warm winters. Some of the agronomic limitations of L. corniculatus and sulla could be reduced by mechanical harvesting and their inclusion as a component in total mixed rations (TMR), instead of grazing.     

Differences between cattle and sheep in their digestion and relative intake of a mature tropical grass hay

The dry-matter digestibility (DMD) of a low quality tropical grass hay was much higher in cattle (49.6%) than in sheep (34.6%). This difference was not due to a difference in relative intake per kg liveweight (W^0.9) nor to a difference in the diet selected. However, neutral-detergent fibre (NDF) was digested better by cattle than by sheep. For each kg of dry matter consumed, cattle digested 415 g NDF and sheep 279 g NDF. This was because 60% more of the hemicellulose and 35% more of the cellulose were digested by cattle than by sheep.Differences between cattle and sheep in the concentrations of urea and sulphate in blood, and the relatively lower excretion of N, P and Ca by the cattle suggested that the rumen micro-organisms of the cattle were utilizing these nutrients better than those of the sheep. This could have increased microbial activity in the rumen and, hence, digestion of fibre.     

Elevated intra-rumen pressure and secondary rumen contractions in sheep (Ovis aries)

1. Sheep rumens were insufflated with nitrogen to 5, 10, 15, and 20 cm water pressure and sustained at each pressure for 10 min. 2. Measurements included rumen motility, reticulorumen myoelectric activity, eructation frequency and volume, changes in tracheal pressure and rumen contraction amplitude. 3. As intra-rumen pressure increased, contractions designated as special secondary contractions appeared. 4. At a pressure of approximately 15 cm water, most of the special secondary contractions became regular secondaries; therefore, the special secondaries were called pro-secondary contractions. 5. Increased intra-rumen pressure was associated with respiratory distress. The recovery phase following, rumen insufflation was accompanied by hyperpnea.     

Ecology of uncultivated Oscillospira species in the rumen of cattle, sheep, and reindeer as assessed by microscopy and molecular approaches

The ecology of the uncultured, but large and morphologically conspicuous, rumen bacterium Oscillospira spp. was studied. Oscillospira-specific 16S rRNA gene sequences were detected in North American domestic cattle, sheep from Australia and Japan, and Norwegian reindeer. Phylogenetic analysis of the sequences obtained allowed definition of three operational taxonomic units within the Oscillospira clade. Consistent with this genetic diversity, we observed atypical smaller morphotypes by using an Oscillospira-specific fluorescence in situ hybridization probe. Despite the visual disappearance of typical large Oscillospira morphotypes, the presence of Oscillospira spp. was still detected by Oscillospira-specific PCR in the rumen of cattle and sheep. These observations suggest the broad presence of Oscillospira species in various rumen ecosystems with the level, and most likely the morphological form, dependent on diet. An ecological analysis based on enumeration of the morphologically conspicuous, large-septate form confirms that the highest counts are associated with the feeding of fresh forage diets to cattle and sheep and in two different subspecies of reindeer investigated.     

Bacterial Content in Samples from Different Sites in the Rumen of Sheep and Cows as Determined in Two Culture Media

Samples of material from the rumen of cattle and of sheep were cultured in both Gall Broth (GB) and Reinforced Clostridium Medium (RCM). Samples were taken, at monthly intervals, from five sites in cattle and two sites in sheep in two series and, at weekly intervals, from two sites in cattle and in sheep in two series. Comparisons were made of the growth of organisms in the media, using the number of fertile tubes per set of six dilutions as a measure of the viable count. RCM gave a greater number of fertile tubes than GB with samples from cattle, but the reverse was the case with samples from sheep. Real differences in the number of fertile tubes from different sites in cattle were found at different times, but there was no consistent pattern. Simultaneous sampling from different sites in the rumen is, therefore, essential to provide an estimate of sampling error within animals. Although no site to site differences were detectable with rumen material from sheep, it is advisable to take more than one sample at a given time to assess sampling error.     

Feeding behavior, rumination, reticulo-ruminal fermentation and plasma volatile fatty acids, compared in goats and sheep; influence of the diet

Two-year old Alpine she-goats (n = 3) and Texel ewes (n = 3) were compared as to eating behaviour, rumination and volatile fatty acids (VFA) in rumen and blood. The animals were fed once daily with two different proportions (20 and 80%) of barley and hay. Dry matter intake was fixed at 48 g D.M/kg P0.75 per day. In similar feeding and environmental conditions, eating behaviour and rumination of goats and sheep did not differ much: the goats tended to eat faster and there were more rumination periods in the sheep. Latency time, mean duration of rumination periods, daily rumination time and circadian pattern of rumination did not differ significantly between the two species (fig. 1). With both diets we observed a higher VFA concentration and a lower acetate/propionate ratio in the rumen of the ewes; however, rumen pH was lower only in those eating the 80% barley ration (fig. 2). Blood VFA in the jugular vein did not differ between sheep and goats (fig. 3). The proportion of cereals and hay in the diets affected rumen fermentation and rumination pattern in both species. With a higher concentrate/roughage ratio, rumen and plasma VFA increased, while the pH and acetate/propionate ratio in the lumen juice, the number of rumination periods and daily rumination time decreased. When the animals were fed the 80% barley ration, there was practically no rumination in the first 9 h after the single meal. During this time, rumen pH was minimal and VFA levels in the rumen and blood were maximal.     

The relative abundance of a salivary protein, bSP30, is correlated with susceptibility to bloat in cattle herds selected for high or low bloat susceptibility

Pasture bloat is a serious economic and animal welfare problem in cattle grazed on legumes in New Zealand. Analysis of salivary proteins from dairy cattle in herds bred for either low or high susceptibility to bloat has resulted in the identification of a 30 kilodalton protein, which we term bSP30, whose relative abundance is negatively correlated with bloat score (r = -0.40 ± 0.12). From 74 animals sampled, relative abundance of bSP30 was 66 ± 15% higher in the low-susceptibility herd than in the high-susceptibility herd. Relative abundance of bSP30 also varied significantly within individuals, according to feeding or time of day, and from day to day, A sequence homology search of 38 amino acids derived from three tryptic fragments of the protein suggests that the amino acid sequence of bSP30 has not been described previously. Amino acid analysis indicates that bSP30 is not a member of the proline-rich family of salivary proteins. The function of bSP30 is unknown but it is conceivable that it plays a role in the aetiology of bloat.     

Use of 1,3-butanediol for lactation and growth in cattle.

These studies have been designed to test whether 1,3-butanediol (BD) alleviates milk fat depression in lactating cows, to observe physiological changes in blood and rumen constituents when BD is fed to cows or growing cattle, and to test the effects of BD on growth rates and feed efficiency in growing cattle. In trials with lactating cows, milk fat percentage and total fat production were higher for cows fed BD than for controls. Feeding BD to either cows or growing cattle had no consistent effect on rumen pH or relative concentrations of rumen volatile fatty acids. 1,3-Butanediol feeding had little effect on blood glucose concentrations. Feeding more than 4% BD in diets sometimes caused increased concentrations of blood ketones. In trials where growing cattle were fed 4% BD, rates of gain and feed efficiency were at least as good as and often better than those of cattle fed the same diets without BD. Body composition was not significantly affected. 1,3-Butanediol can be utilized effectively as an energy source for cattle and causes no obvious problems with 4% in diets.     

Differential passage of fluids and different-sized particles in fistulated oxen (Bos primigenius f. taurus), muskoxen (Ovibos moschatus), reindeer (Rangifer tarandus) and moose (Alces alces): Rumen particle size discrimination is independent from contents stratification

Ruminant species differ in the degree that their rumen contents are stratified but are similar insofar that only very fine particles are passed from the forestomach to the lower digestive tract. We investigated the passage kinetics of fluid and particle markers (2, 10 and 20 mm) in fistulated cattle (Bos primigenius f. taurus), muskoxen (Ovibos moschatus), reindeer (Rangifer tarandus) and moose (Alces alces) on different diets. The distribution of dry matter in the rumen and the viscosity of rumen fluids suggested that the rumen contents were more stratified in muskoxen than moose. Correspondingly, as in previous studies, the species differed in the ratio of mean retention times of small particles to fluids in the reticulorumen, which was highest in cattle (2.03) and muskoxen (1.97–1.98), intermediate in reindeer (1.70) and lowest in moose (0.98–1.29). However, the ratio of large to small particle retention did not differ between the species, indicating similarity in the efficiency of the particle sorting mechanism. Passage kinetics of the two largest particle classes did not differ, indicating that particle retention is not a continuous function of particle size but rather threshold-dependent. Overall, the results suggest that fluid flow through the forestomach differs between ruminant species. A lower relative fluid passage, such as in moose, might limit species to a browse-based dietary niche, whereas a higher relative fluid passage broadens the dietary niche options and facilitates the inclusion of, or specialization on, grass. The function of fluid flow in the ruminant forestomach should be further investigated.     

Nitrogen levels in low-roughage diets for efficient rumen microbial protein production

The influence of dietary nitrogen (N) available in the rumen on the efficiency of microbial protein production was examined for 43 predominantly low-roughage diets given to cattle or sheep with rumen and duodenal (re-entrant) cannulae. The minimum amount of available N required for efficient microbial protein production was 2.0 g/100 g of organic matter actually digested in the rumen. When the diet supplied 2.7 g of available N/100 g of organic matter actually digested in the rumen, there was no net utilisation of recycled N.From this information, concentrations of N in organic matter required in low-roughage diets differing in organic matter digestibility and availability of dietary N have been calculated. Also a method of calculating the quantities of amino acid N and of particular amino acids absorbed from the small intestine from a knowledge of the diet composition is presented.     

Ovulation and ovulation rate in ewes under grazing conditions: factors affecting the response to short-term supplementation

The relationships between ovulation rate and nutrition remain confused, probably because of uncontrolled variation in experimental conditions. To help resolve the problem, we analyzed data from 20 experiments conducted between 2002 and 2016, in Uruguay with grazing ewes. All experiments were carried out by a single laboratory under comparable conditions of experimental design and measured variables. The studies used a total of 3 720 ewes, of purebred Corriedale, Polwarth, or East Friesian x Polwarth genotypes. In all experiments, a control group grazed native pastures and extra nutrition was provided to the treatment groups using either improved pastures or supplements. Ovulation rate was measured by counting corpora lutea using laparoscopy or rectal ultrasound or by counting foetuses at ultrasound on day 45 of gestation. For statistical analysis, data were grouped according to nutritional treatment (control or supplemented) and, within these groups, type of supplement to provide energy or protein (protected or not from rumen degradation). Across all experiments, 92–99% of the ewes ovulated and the effects of diet, length of supplementation, and initial live weight and genotype are reported. Within diets, ovulation was most affected by overall energy intake during supplementation (P < 0.01). Ewes that grazed native pastures supplemented with protein supplements had higher ovulation rates (P < 0.05) than control ewes grazing only native pastures. The addition of tannins to the protein supplement, to protect it from degradation in the rumen, did not further increase the ovulation rate. In unsupplemented ewes that had access to legume pastures, ovulation rates did not increase when the legume pasture was rich in tannins although only ewes that grazed tanniniferous legumes had marginally higher ovulation rates than the control ewes (P < 0.05). When ewes grazing native pastures were supplemented with energy, their ovulation rate did not increase above those of nonsupplemented ewes. Live weight at the start of supplementation also affected ovulation rate. We conclude that ovulation was most affected by overall energy intake, whereas the factors that affected ovulation rate during short-tern nutritional supplementation were intake of protein from highly digested supplements or dietary protein protected from ruminal degradation.     

Feed intake and milk production in dairy cows fed different grass and legume species: a meta-analysis

The aim of this meta-analysis was to compare feed intake, milk production, milk composition and organic matter (OM) digestibility in dairy cows fed different grass and legume species. Data from the literature was collected and different data sets were made to compare families (grasses v. legumes, Data set 1), different legume species and grass family (Data set 2), and different grass and legume species (Data set 3+4). The first three data sets included diets where single species or family were fed as the sole forage, whereas the approach in the last data set differed by taking the proportion of single species in the forage part into account allowing diets consisting of both grasses and legumes to be included. The grass species included were perennial ryegrass, annual ryegrass, orchardgrass, timothy, meadow fescue, tall fescue and festulolium, and the legume species included were white clover, red clover, lucerne and birdsfoot trefoil. Overall, dry matter intake (DMI) and milk production were 1.3 and 1.6 kg/day higher, respectively, whereas milk protein and milk fat concentration were 0.5 and 1.4 g/kg lower, respectively, for legume-based diets compared with grass-based diets. When comparing individual legume species with grasses, only red clover resulted in a lower milk protein concentration than grasses. Cows fed white clover and birdsfoot trefoil yielded more milk than cows fed red clover and lucerne, probably caused by a higher OM digestibility of white clover and activity of condensed tannins in birdsfoot trefoil. None of the included grass species differed in DMI, milk production, milk composition or OM digestibility, indicating that different grass species have the same value for milk production, if OM digestibility is comparable. However, the comparison of different grass species relied on few observations, indicating that knowledge regarding feed intake and milk production potential of different grass species is scarce in the literature. In conclusion, different species within family similar in OM digestibility resulted in comparable DMI and milk production, but legumes increased both DMI and milk yield compared with grasses.     

Recovery of intravenously infused chromium EDTA and lithium sulphate in the urine of cattle and their use as markers to measure urine volume

A series of metabolism experiments investigated the recovery of continuous-, intravenously infused chromium complexed with ethylenediamine tetra-acetic acid (CrEDTA) and lithium sulphate in the urine of cattle with a view to using the markers to estimate urine and metabolite output in grazing cattle. The recovery of Cr in urine from these infusions was similar (90%) in metabolism trials when cattle consumed three very contrasting diets: high-grain formulated pellet, lucerne hay (Medicago sativa) or low-quality native grass hay (predominantly Heteropogon contortus). By contrast, Li recovery in urine averaged 46.3 ± 0.40% and 72.6 ± 0.43% for native pasture and lucerne hays, respectively, but was not constant across days. There was negligible transfer of Cr from CrEDTA in blood serum to the rumen or faeces, whereas appreciable quantities of infused Li were found in both. The ratio of urine volume estimated by spot samples and marker dilution of Cr, to urine volume measured gravimetrically, was 1.05. In grazing studies using rumen-fistulated (RF) steers grazing seven different tropical and temperate grass and legume pastures, the ratio of concentrations of purine derivatives (PD) to Cr in spot samples of urine was shown to vary diurnally in the range of 49% to 157% of the average 24 h value. This finding indicated the need for regular sampling of urine to achieve an accurate average value for the PD : Cr ratio in urine for use in estimating urinary PD excretion and hence microbial protein production in the rumen. It was concluded that continuous, intravenous infusion of CrEDTA resulted in a constant recovery of Cr in the urine of cattle across diets and, provided an intensive sampling regime was followed to account for diurnal variation, it would be suitable as a marker to estimate urine volume and urinary output of PD in grazing cattle.     

Comparative studies on the distribution of rhodanese and beta-mercaptopyruvate sulfurtransferase in different organs of sheep (Ovis aries) and cattle (Bos taurus)

1. The activities of rhodanese and beta-mercaptopyruvate sulfurtransferase (MST) in different organs of sheep and cattle were measured. 2. Liver, kidney, omasum, and rumen were the richest sources of both enzymes. The activities of both enzymes in other organs of the sheep and the cattle decreased in the order of lung, brain, heart, abomasum, lymph node, urinary bladder, spleen, and the skeletal muscle. 3. The activities of both enzymes in most organs of the sheep were higher than the cattle. 4. Both enzymes showed higher activities in the epithelial layers than the muscular layers of rumen, omasum and reticulum. 5. In most of the tissues of both species the level of rhodanese activity was greater than MST.     

Acyl-Homoserine-Lactone Autoinducer in the Gastrointesinal Tract of Feedlot Cattle and Correlation to Season, <Emphasis Type="Italic">E. Coli</Emphasis> O157:H7 Prevalence,and Diet

Acyl-homoserine-lactone autoinducer (AHL) produced by nonenterohemorrhagic Escherichia coli species in cattle appears to be required for enterohemorrhagic E. coli (EHEC) colonization of the gastrointestinal tract (GIT). The current research aimed to examine the effect of season, diet, EHEC shedding, and location within the GIT on AHL prevalence in the ruminant. Luminal content samples were collected from the rumen and rectum of feedlot cattle at slaughter in the spring, summer, fall, and winter for culture of E. coli O157:H7 and AHL determination. During the spring collection, samples were additionally collected from the cecum and small intestine, but these samples all were AHL negative and therefore not examined again. To assess the influence of diet on AHL prevalence, 14 lambs were fed either 100% forage or 80% concentrate diets and experimentally inoculated with EHEC. At 8 days after infection, all the lambs were killed, and necropsies were taken, with luminal contents collected from the GIT. The collections from the feedlot cattle had AHL in 100% of the rumen content samples from the spring, summer, and fall, but not in any of the winter samples. No other GIT samples from feedlot cattle were AHL positive, and all the samples from the sheep study were AHL negative. The cattle seemed to show a weak correlation between ruminal AHL and EHEC prevalence. This research found AHL only in the rumen and not in the lower GIT of feedlot cattle. However, it is unclear whether this is because the pH of the lower gut destroys the AHL or because a lack of certain bacteria in the lower gut producing AHL. Mention of trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the USDA and does not imply its approval to the exclusion of other products that may be suitable.     

A causal analysis of diet composition in free ranging cattle in reed-dominated vegetation

Summary Theoretical and observed diets of free-ranging yearling cattle in an area of reed-dominated vegetation were related to constraints inherent to ruminants (rumination time as reflected in the zone of acceptable crude fibre content of the ration; rumen fill) and in more general terms, to requirements for minerals (Na, Ca, Mg, P), for protein and for metabolisable energy in order to balance the growth rate achieved by experimental animals. Theoretical diets in spring were mainly limited by feeding time; theoretical diets in summer and autumn were mainly limited by rumen capacity. The high proteinto-energy ratio in the forage species caused protein intake to exceed the animals' demands. Mineral intake was in excess of requirements except for sodium. Yearling cattle in our study area maximized their energy intake, with feeding time, rumen capacity and crude fibre content of the forage as important constraints.     

Ruminal fermentation characteristics and microbial nitrogen assimilation in sheep fed differently composed grass silages

The investigation aimed at examining if the composition of grassland silage affects the microbial nitrogen assimilation in the rumen of sheep. The silages were made of vegetative summer re-growths consisting of 48% grasses, 28% legumes and 24% other forbs (GCF) or of pure grass (G). Silage GCF contained more intermediately degradable non-structural and less slowly degradable carbohydrates, more crude protein (CP), a narrower ratio between slow and very slow degradable nitrogen (N), and exhibited higher in situ degradability of organic matter and CP than Silage G. Four adult wethers equipped with rumen fistulae were used in a two factorial trial. Feed was offered either as silage alone or as a mixture of silage and barley (60:40). Microbial N was estimated using continuous intraruminal 15N infusion and measurement of 15N-enrichment in microbes isolated from rumen liquor samples. With the exception of trends for ruminal butyrate concentrations, no interactions were detected between silage and barley feeding. Sheep receiving Silage GCF exhibited larger diurnal fluctuations of ammonia, and produced more microbial N (p < 0.05) than sheep on Silage G. Feeding the silages with barley decreased ruminal pH and elevated the concentrations of butyrate (p < 0.05). The 15N incorporation into microbial N was reduced by barley feeding (p < 0.05) along with a trend to accelerated rumen fluid turnover, resulting in similar microbial N yields as found in sheep receiving silage without barley. It is concluded that the larger and better balanced amounts of intermediately degradable carbohydrate- and N-containing fractions favoured the ruminal microbial protein synthesis in sheep consuming Silage GCF instead of Silage G.