Incidence Of Bloat Research Articles

40. Predictive equations to detect incidence of feedlot bloat in finishing cattle in individual cattle management systems

40. Predictive equations to detect incidence of feedlot bloat in finishing cattle in individual cattle management systems

Meta-analysis of the effects of monensin on growth and bloat of cattle on pasture.

Monensin has been part of the beef production landscape for over 45 years. Although first approved for use in finishing cattle, it has since been approved for cattle in extensive production systems and has been an economical way to increase performance of forage-fed animals. This meta-analysis investigated the impacts of monensin on performance of stocker cattle on high-forage diets. The stocker performance analysis resulted from 38 experiments with 73 mean comparisons; bloat analysis was conducted with 12 experiments with 23 mean comparisons. The metaphor package (version 2.4-0) for R (version 4.0.3; www.r-project.org) was used to determine the overall effect size of monensin compared to a negative control. Each study’s n, means, and SEM or P-value was used to calculate the mean difference and estimate of within-study variance for responses of interest. Moderators of monensin response considered in the analysis were delivery method, dose, study duration, initial calf BW, diet ME and CP, and forage category. Initial BW and basal ADG averaged 236 ± 45.9 kg and 0.72 ± 0.28 kg, respectively. In the ADG analysis, the only significant moderator of those considered was length of the study (P < 0.01); as duration of the study increased, the ADG response to monensin decreased by 0.0007 kg/day. For the average 112-day length of study, the average monensin response was estimated to be 0.0784 kg/day increase in ADG, approximately 10% above controls. Sufficient information was presented in 18 citations representing 40 mean comparisons for determining the effect of monensin on BW at the end of the experiment. The response model (P < 0.01) for ending BW, kg = 22.3–0.05 (initial calf BW, kg). Thus, for the average initial BW of 235 kg the average monensin response was estimated to be 10.6 kg increase in average ending BW. The incidence (−20%) and severity (−0.7 bloat score) of bloat was found to be reduced in bloat-prone pastures. There is ample evidence that monensin increases performance of growing calves on high forage diets along with reducing the incidence and severity of bloat.

The Use of Temperate Tannin Containing Forage Legumes to Improve Sustainability in Forage–Livestock Production

Greenhouse gas emissions from ruminant livestock production systems contribute significantly to the environmental footprint of agriculture. Emissions are lower for feedlot systems than for grass-based systems primarily because of the extra time required for grass-finished cattle to reach slaughter weight. In contrast, legume forages are of greater quality than grasses, which enhances intake and food conversion efficiencies, leading to improvements in production and reductions in environmental impacts compared with forage grasses. In addition, the presence of certain bioactives in legumes such as condensed tannins (CT) enhance the efficiency of energy and protein use in ruminants relative to grasses and other feeds and forages. Grazing tannin-containing legumes also reduce the incidence of bloat and improve meat quality. Synergies among nutrients and bioactives when animals graze diverse legume pastures have the potential to enhance these benefits. Thus, a diversity of legumes in feeding systems may lead to more economically, environmentally, and socially sustainable beef production than grass monocultures or feedlot rations.

PSXIV-4 Meta-analysis of the effects of monensin on growth and bloat of growing beef calves on pasture

Abstract This meta-analysis investigated the impacts of monensin on performance of stocker cattle on high-forage diets. The stocker performance analysis resulted from 38 experiments with 73 mean comparisons; bloat analysis was conducted with 12 experiments with 23 mean comparisons. The metaphor package (version 2.4-0) for R (version 4.0.3; www.r-project.org) was used to determine the overall effect size of monensin compared to a negative control. Each study’s n, means, and SEM or P-value was used to calculate the mean difference and estimate of within study variance for responses of interest. Moderators of monensin response considered in the analysis were delivery method, dose, study duration, initial calf BW, diet ME and CP, and forage category. Initial BW and basal ADG averaged 236 ± 45.9 kg and 0.72 ± 0.28 kg/day, respectively. In the ADG analysis the only significant moderator of those considered was length of the study (P &amp;lt; 0.01), as duration of the study increased the ADG response to monensin decreased by 0.0007 kg/day. For the average 112-day length of study, the average monensin response is estimated to be 0.0784 kg/day increase in average daily gain. Sufficient information was presented in only 18 citations representing 40 mean comparisons for determining the effect of monensin on BW at the end of the experiment, estimated by (P &amp;lt; 0.01) monensin response (increased ending BW, kg) = 22.3 – 0.05 (initial calf BW, kg). Thus, for the average initial BW of 235 kg the average monensin response is estimated to be 10.6 kg increase in average ending BW. The incidence (-20%) and severity (-0.7 bloat scores) of bloat was found to be reduced in bloat prone pastures. There is ample evidence that monensin increases performance of growing calves on high forage diets along with reducing the incidence and severity of bloat.

Supplementing Yucca schidigera extract to mitigate frothy bloat in beef cattle receiving a high-concentrate diet.

This experiment compared incidence of frothy bloat, as well as ruminal, physiological, and performance responses of beef heifers receiving a bloat-provoking diet and supplemented with Yucca schidigera extract. Sixteen ruminally cannulated Angus-influenced heifers were ranked by body weight (BW) and assigned to 4 groups of 4 heifers each. Groups were enrolled in a replicated 4 × 4 Latin square design containing 4 periods of 28 d, and a 21-d washout interval between periods. Groups were assigned to receive no Y. schidigera extract (CON), or Y. schidigera extract at (as-fed basis) 1 g/heifer daily (YS1), 2 g/heifer daily (YS2), or 4 g/heifer daily (YS4). During each period, heifers (n = 16/treatment) were housed in individual pens, and fed a sorghum (Sorghum bicolor L.)-based bloat-provocative diet at 2% of their BW. Diet and treatments were individually fed to heifers, twice daily in equal proportions (0700 and 1600 hours). Heifers were assessed for bloat score (0 to 5 scale, increasing according to bloat severity) 3 hr after the morning feeding. Blood samples were collected on days 0, 7, 14, 21, and 28 prior to (0 hr) and at 3, 6, and 9 hr relative to the morning feeding. Rumen fluid samples were collected at the same time points on days 0 and 28. Orthogonal contrasts were tested to determine whether inclusion of Y. schidigera extract (0, 1, 2, or 4 g/heifer daily) yielded linear or quadratic effects, and explore an overall effect of Y. schidigera extract supplementation (CON vs. YS1 + YS2 + YS4). Rumen fluid viscosity was impacted quadratically by Y. schidigera extract inclusion (P = 0.02), being greatest in YS1, followed by YS2, and equivalent between CON and YS4 heifers. Heifers receiving Y. schidigera extract had greater (P ≤ 0.05) rumen propionate, iso-valerate, and valerate concentrations, as well as less (P < 0.01) acetate : propionate ratio compared with CON heifers. Inclusion of Y. schidigera extract linearly increased (P ≤ 0.04) average daily gain and feed efficiency. No other treatment effects were noted (P ≥ 0.19) including bloat score (1.07 ± 0.03 across treatments), ruminal protozoa count, plasma concentrations of cortisol, haptoglobin, urea N, total protein, and rumen concentration of total volatile fatty acids. Supplementing Y. schidigera extract up to 4 g/d favored rumen propionate concentrations and linearly increased growth and feed efficiency but failed to mitigate incidence of frothy bloat in beef heifers consuming a grain-based bloat-provocative diet.

Safety of robotic assisted laparoscopic recurrent paraesophageal hernia repair: insights from a large single institution experience.

Laparoscopic repair of recurrent as opposed to primary paraesophageal hernias (PEHs) are historically associated with increased peri-operative complication rates, worsened outcomes, and increased conversion rates. The robotic platform may aid surgeons in these complex revision procedures. The aim of this study was to compare the outcomes of patients undergoing robotic assisted laparoscopic (RAL) repair of recurrent as opposed to primary PEHs. Patients undergoing RAL primary and recurrent PEH repairs from 2009 to 2017 at a single institution were reviewed. Demographics, use of mesh, estimated blood loss, intra-operative complications, conversion rates, operative time, rates of esophageal/gastric injury, hospital length of stay, re-admission/re-operation rates, recurrence, dysphagia, gas bloat, and pre- and post-operative proton pump inhibitor (PPI) use were analyzed. Analysis was accomplished using Chi-square test/Fischer's exact test for categorical variables and the Mann-Whitney U test for continuous variables. There were 298 patients who underwent RAL PEH repairs (247 primary, 51 recurrent). They were followed for a median (interquartile range) of 120 (44, 470) days. There were no significant differences in baseline demographics between groups. Patients in the recurrent PEH group had longer operative times, increased use of mesh, and increased length of hospital stay. They were also less likely to undergo fundoplication. There were no significant differences in estimated blood loss, incidence of intra-operative complications, re-admission rates, incidence of post-operative dysphagia and gas bloat, and incidence of post-operative PPI use. There were no conversions to open operative intervention or gastric/esophageal injury/leaks. Although repair of recurrent PEHs are historically associated with worse outcomes, in this series, RAL recurrent PEH repairs have similar peri-operative and post-operative outcomes as compared to primary PEH repairs. Whether this is secondary to the potential advantages afforded by the robotic platform deserves further study.

Excretion of Eimeria spp. oocysts in young lambs following iron supplementation

BackgroundIron is an essential nutrient, and iron supplementation has been shown to reduce the incidence of abomasal bloat in lambs. Additionally, iron deficiency is linked to pica, which may increase uptake of Eimeria oocysts. Coccidiosis in sheep, caused by Eimeria spp., is an important infection, leading to reduced welfare and economic losses. The aims of our study were to investigate: (1) the use of iron supplementation in Norwegian sheep flocks using a questionnaire survey, and (2) whether iron supplementation reduced excretion of Eimeria oocysts and increased the growth rates of young lambs.ResultsA questionnaire regarding the use of iron supplementation, sent to all members of the Norwegian Sheep Recording System (n = 4993), showed that 152/1823 farmers iron-supplemented lambs, either orally (56.7%) or by injection (43.3%). The main purpose of supplementation was to prevent abomasal bloat (38.4%), coccidiosis (9.3%), or both (27.8%). In the field study, 102 twin lambs from five flocks were included: one twin (treated) received 600 mg of gleptoferron subcutaneously within 3 days of birth, whereas the control was given saline. McMaster analysis of individual faecal samples obtained at weekly intervals (n = 4 per lamb, starting at turnout) showed no significant difference in oocyst excretion between treatment groups at any sampling, except for one flock 14 days after turnout. Mean growth rates, measured at iron injection, 21 days after turnout, and in the autumn, differed significantly between treated and untreated lambs from iron injection to 21 days after turnout, however, no difference in growth rates was observed in the overall period from iron injection to autumn. Blood analysis suggested that the controls were at risk of developing iron deficiency anaemia during the housed period, but signs of anaemia were not observed.ConclusionIron supplementation of lambs was used by 8.3% of the farmers responding to the questionnaire, mainly with the intention to prevent abomasal bloat, coccidiosis, or both. The field trial results indicate that iron supplementation of young lambs do not reduce oocyst excretion and only induced a transitory increase in weight gain. However further studies, including more flocks and possibly repeated iron injections, would provide more definitive information.

Review: Peran pakan pada kejadian kembung rumen

&lt;p&gt;Bloat is a form of indigestion characterized by excessive gas accumulation in the rumen. Bloat occurs when the eructation mechanism is disturbed and the rate of gas production exceeds the animal's ability to expelled it. Bloat can occur very quickly due to excessive volume of gas produced in the rumen. Bloat can be classified into a primary bloat (frothy / wet bloat) mixed with rumen and secondary bloat / free bloat (free gas / dry bloat) contents in a separate free gas. There is no single method of preventing bloat events that can be applied in every different situation, however, there are methods of management in prevention and treatment that can help minimize risks. In Indonesia, although the incidence of bloat is quite high, but no data is well documented. This paper aims to review the bloat and problems in terms of understanding the clinical symptoms and the results of laboratory examination, prevention and treatment so that it is expected to be implemented by peers and field officers to reduce the risk of loss of farmers due to possible livestock death.&lt;/p&gt;

Modification of abomasum contractility by flavonoids present in ruminants diet: in vitro study

Flavonoid supplementation is likely to be beneficial in improving rumen fermentation and in reducing the incidence of rumen acidosis and bloat. Flavonoids are also said to increase the metabolic performance during the peripartum period. Ruminants are constantly exposed to flavonoids present in feed. However, it is not clear if these phytochemicals can affect the activity of the gut smooth muscle. Therefore, the aim of the study was to verify the effect of three flavonoids on bovine isolated abomasum smooth muscle. The study was carried out on bovine isolated circular and longitudinal abomasal smooth muscle specimens. All experiments were conducted under isometric conditions. The effect of apigenin, luteolin and quercetin (0.001 to 100 µM) was evaluated on acetylcholine-precontracted preparations. The effect of multiple, but not cumulative, treatment and single treatment with each flavonoid on abomasum strips was compared. Apigenin (0.1 to 100 µM) dose-dependently showed myorelaxation effects. Luteolin and quercetin applied in low doses increased the force of the ACh-evoked reaction. However, if used in high doses in experiments testing a wide range of concentrations, their contractile effect either declined (luteolin) or was replaced by an antispasmodic effect (quercetin). Surprisingly, the reaction induced by flavonoids after repeated exposure to the same phytochemical was not reproducible in experiments testing only single exposure of abomasum strips to the same flavonoid used in a high concentration. Taking into account the physicochemical properties of flavonoids, this data suggests the ability of flavonoids to interfere with cell membranes and, subsequently, to modify their responsiveness. Assuming ruminant supplementation with luteolin or quercetin or their presence in daily pasture, a reduction of the likelihood of abomasum dysmotility should be expected.

Feeding subtherapeutic antimicrobials to low-risk cattle does not confer consistent performance benefits

Stanford, K., Gibb, D. J., Schwartzkopf-Genswein, K. S., Van Herk, F. and McAllister, T. A. 2015. Feeding subtherapeutic antimicrobials to low-risk cattle does not confer consistent performance benefits. Can. J. Anim. Sci. 95: 589–597. Two-hundred and forty steers were obtained from the same ranch in each of 2 yr. Growth performance, health status and carcass characteristics from steers fed subtherapeutic antimicrobials were compared with those of control steers without antimicrobial metaphylaxis. Experimental groups included Control, not fed antimicrobials; CTCS-700, fed 350 mg head−1 d−1 chlortetracycline (CTC) and 350 mg head−1 d−1 sulfamethazine; CTC-11, fed 11 mg kg−1 CTC; TYL, fed 11 mg kg−1 tylosin phosphate; and CTC-350, fed 350 mg head−1 d−1 CTC. Steers were housed in pens of 10 steers and fed antimicrobials during both backgrounding and finishing periods. The incidence of bovine respiratory disease, pinkeye and bloat did not differ among experimental groups, although the incidence of foot rot was lower in Control steers (P&lt;0.05) than in steers receiving TYL. In both years of the study, overall performance (backgrounding+finishing) was not improved by subtherapeutic antimicrobials. Similarly, carcass characteristics and the incidence and severity of liver abscesses were not improved compared with Control steers by feeding subtherapeutic antimicrobials. The results of the present study demonstrate that low-risk steers may be managed in small pens with equivalent growth performance, carcass characteristics and health status to steers fed subtherapeutic antimicrobials.

Application of Ionophores in Cattle Diets

Beef cattle producers should consider using ionophores to increase calf gain and gain efficiency in a cost-effective manner. Ionophores are feed additives used in cattle diets to increase feed efficiency and body weight gain. They are compounds that alter rumen fermentation patterns. Ionophores can be fed to any class of cattle and can be used in any segment of the beef cattle industry. Similar to many other feed additives, ionophores are fed in very small amounts and supplied via another feedstuff as carrier for intake. Ionophores decrease incidence of coccidiosis, bloat, and acidosis in cattle. This 4-page fact sheet was written by Matt Hersom and Todd Thrift, and published by the UF Department of Animal Sciences, December 2012. AN285/AN285: Application of Ionophores in Cattle Diets (ufl.edu)

Frothy bloat in ruminants: Cause, occurrence, and mitigation strategies

A number of pasture and feedlot management practices and feed additives have reduced, but not eliminated the occurrence of frothy bloat in cattle. Bloat occurs as a result of complex interactions among the feed, rumen microbial populations and the host. Factors such as soluble protein levels in the feed, rates of feed digestion, bacterial slime production and digesta passage rates, all play a role in the likelihood of bloat. Practices that lower soluble protein levels and retard the rate of feed digestion can reduce the risk of bloat as can grazing alfalfa at advanced stages of maturity. Similarly, processing grain to an optimal particle size, inclusion of ionophores in the diet and allowing a period of adaptation during the transition from forage to grain diets lowers the incidence of feedlot bloat. Pluronic detergents which disperse the stable froth in the rumen can be effective in the treatment and prevention of both pasture and feedlot bloat. The sporadic and unpredictable nature of frothy bloat often makes it unrealistic for preventative measures to be applied to all animals at risk. Genetic engineering of condensed tannin containing, bloat-safe varieties of alfalfa and clover may eliminate the occurrence of bloat in cattle grazing these forages. Understanding the factors that regulate intake and contribute to bacterial slime production could provide additional insight into feedlot bloat. Comparing of the rumen microbial metagenomes and metatrascriptomes of bloated and non-bloated animals should provide a fresh perspective on the role of rumen microbial populations in bloat. The key to the successful prevention of frothy bloat lies in a thorough understanding of the feed, microbial and host factors involved in the condition.

Effect of grazing mixtures of alfalfa and orchardgrass grown in strips on the incidence of bloat in cattle

Steers were grazed on pastures with alfalfa and orchardgrass grown in monoculture strips with alfalfa covering 100, 75 or 50% of the ground area. The forages were maintained at an early stage of growth during the trial. The incidence of frothy bloat in cattle was reduced by 70 to 90% when grass was a component of the pasture. Given unconstrained free choice, the legume was preferred over the grass by steers. Key words: Steers, frothy bloat, Medicago sativa L., Dactylis glomerata L., mixed pastures, grazing

Occurrence of Condensed Tannins in Wheat and Feasibility for Reducing Pasture Bloat

Bloat can be a serious problem for ruminant livestock grazing pastures of winter wheat (Triticum aestivum L.) in the southern Great Plains. Tannins in forage can reduce the incidence and severity of bloat. We measured the content and variability of total phenolics and condensed tannins (CT) in forage extracts from wheat varieties and experimental lines (ExpLines) to assess the feasibility of developing improved varieties using conventional breeding methods to give producers a choice to reduce the incidence of bloat. Forage of 16 winter wheat varieties were collected in late fall at the start of grazing. Also, late fall forage samples and regrowth from late fall clipped forage and unclipped growth before jointing were collected for 221 diverse ExpLines and four Check varieties. Among the 16 adapted winter wheat varieties significant differences for the acid‐butanol but not the vanillin CT assay were observed. Among the ExpLines, significant differences in extractable total phenolics were detected (range for all samples collected, 8.9–31.5 mg tannic acid g−1 dry wt.) and for one of the three forage collections using each CT assay. While we observed differences in CT reactive substances among the ExpLines, even the greatest equivalent amounts detected (12 mg quebracho g−1 dry wt. and 0.67 mg epicatechin g−1 dry wt.) are unlikely sufficient to render the forage bloat‐safe. Perhaps those experimental lines with the most abundant CT levels could be used in a selection program to increase the level of CT in wheat forage.

ROBOTIC TRANSABDOMINAL BELSEY FUNDOPLASTY FOR GASTROESOPHAGEAL REFLUX DISEASE

PURPOSE: Transthoracic Belsey fundoplasty is associated with lower incidence of gas bloat and dysphagia compared to the Nissen wrap. However Belsey Mark IV fundoplasty has rarely been considered in patients with gastroesophageal reflux disease due to the fact that it is performed via thoracotomy. Minimally invasive techniques for performing the complex procedure through via chest or abdomen have not been successful. The 3-D visualization, greater dexterity, more accurate dissection of the da Vinci surgical robot may facilitate a laparoscopic approach to the Belsey Mark IV procedure.

Rumen distension and contraction influence feed preference by sheep1,2

Distension of the rumen limits feed intake by livestock. Ruminal dysfunctions due to bloat, which causes distension by accumulation of excessive gas within the rumen, also reduce feeding. We hypothesized that excessive levels of rumen distension cause feed aversions and that preference increases for feeds eaten in association with recovery from bloat. To test these hypotheses, we determined whether 12 commercial crossbred lambs (average initial BW of 43 +/- 2 kg) could associate ingestion of specific feeds with the consequences of increased intraruminal pressure and its subsidence. Six of the lambs were fitted with rumen cannulas and offered ground alfalfa for 30 min after a rubber balloon was inserted into the rumen of each animal and distended with air to volumes of 1.8, 2.5, or 4.5 L. Subsequently, balloons were deflated and alfalfa was offered again for a second period of 30 min. Feed intake was not affected when the balloon was not distended (P = 0.45 to 0.93), but distension reduced feed intake (P < 0.001) in direct proportion to the magnitude of distension at all 3 volumes (R(2) = 0.70). Relief from distension promoted a compensatory increase in feed intake (P = 0.006). During conditioning to determine if lambs acquired a preference for a feed associated with recovery from distension, fistulated lambs were offered novel feeds: wheat bran (group 1; n = 3) and beet pulp (group 2; n = 3), and the balloon was distended for 30 min. Feeds were then switched and the balloons were deflated (recovery). Control lambs (n = 6) received the same feeding protocol without the balloons. Lambs formed strong aversions to feeds associated with distension and preferred feeds associated with recovery (P = 0.001 to P = 0.10). No preferences or avoidances were observed in control lambs conditioned without rumen distension (P = 0.17 to P = 0.87). Thus, rumen distension and recovery from distension induced feed aversions and preferences, respectively, which may be critical in learning avoidance of bloat-inducing plants and preferences for plants and supplements that relieve the incidence of bloat.

ASAS Centennial Paper: Contributions in the Journal of Animal Science to understanding cattle metabolic and digestive disorders1

Acute and subacute ruminal acidosis, bloat, liver abscesses, and polioencephalomalacia (PEM) were reviewed with respect to contributions published in the Journal of Animal Science (JAS) regarding these metabolic and digestive disorders in beef cattle. Increased grain feeding and expansion of the feedlot industry in the 1960s led to considerable research on acidosis, and early publications defined ruminal changes with acute acidosis. The concept of subacute acidosis was developed in the 1970s. Significant research was published during the 1980s and 1990s on adaptation to high-grain diets, effects of ionophores, and the development of model systems to study ruminal and metabolic changes in acidosis. Since 2000, JAS publications on acidosis have largely focused on individual animal variability in response to acid loads and the role of management strategies in controlling acidosis. Increased grain feeding also was associated with an increase in the incidence of liver abscesses, which were quickly linked to insults to the ruminal epithelium associated with acidosis. The role of antibiotics, particularly tylosin, in decreasing the incidence and severity of liver abscesses was a significant contribution of JAS publications during the 1970s and 1980s. Papers on bloat were among the earliest published in JAS related to metabolic and digestive disorders in cattle. Noteworthy accomplishments in bloat research chronicled in JAS include the nature of ruminal contents in legume and feedlot bloat, the role of plant fractions and microbial populations in the development of bloat, and the efficacy of poloxalene, ionophores, and, more recently, condensed tannins in decreasing the incidence and severity of bloat. Although less research has been published on PEM in JAS, early publications highlighting the association between PEM and ruminal acidity and the role of thiaminase in certain forms of the disorder, as well as more recent publications related to the role of sulfur in the development of PEM, are noteworthy contributions. Since the 1940s, outstanding and often-cited review articles have made JAS a highly visible source of information on these disorders. Thus, JAS has played a significant role as a repository for information pertaining to metabolic and digestive disorders in cattle and other ruminants, and it will no doubt continue to be a premier resource for information on these conditions during the second century of the American Society of Animal Science.

The effect of feeding hay before fresh alfalfa on the occurrence of frothy bloat in cattle

Alfalfa or orchardgrass hay was fed to cattle before feeding fresh alfalfa herbage at the vegetative to early bud stage of growth to observe the subsequent impact on bloat. Alfalfa hay supplements reduced the incidence of bloat by a third in one trial, but no effect was seen in a second trial. In contrast, supplements of orchardgrass hay reduced the occurrence of bloat by &gt; 90% in 2 yr of trials. Supplemental orchardgrass hay can be effective in the control of pasture bloat. Key words: Steers, frothy bloat, Medicago sativa L., Dactylis glomerata L., hay supplements

Comparison of alfalfa and mixed alfalfa-sainfoin pastures for grazing cattle: Effects on incidence of bloat, ruminal fermentation, and feed intake

Grazing experiments were conducted over two years to evaluate the effects of incorporating sainfoin (Onobrychis viciifolia) into alfalfa (Medicago sativa) pasture on bloat, ruminal fermentation, and feed intake. Pastures of alfalfa (Alf) and alfalfa-sainfoin (AS) were established by cross-seeding (in 1998) or parallel-seeding in (1999) sainfoin into strip-seeded alfalfa. The pastures were used in grazing studies in 1999 and 2000. For periods of 4 or 5 d, 12 ruminally cannulated Jersey steers were turned out into pastures from 0830 to 1430 daily (without access to water) then were moved to a fenced area (with free access to water but no feed) until the next morning. Feed intake during grazing was estimated using alkane markers, development of bloat was assessed, and ruminal fluid (RF) fermentation properties were determined. Incidence of bloat on first-growth pastures grazed at early bloom in 1999 was unaffected by sainfoin (at 8.3%, DM basis) but was reduced by 80% (P &lt; 0.001) in AS pasture compared with Alf, when grazed at full-bud in 2000 (12.1% sainfoin). With re-growth forage, bloat incidence was decreased by 77% (P &lt; 0.05) on pasture containing 35% sainfoin, but treatment effect was not observed on pastures containing &lt; 23% sainfoin. Incidence of bloat was reduced as the proportion of sainfoin in herbage mass increased. In 2000, ruminal ammonia concentrations were reduced (P &lt; 0.05) with mixed forage containing ≥ 12.1% sainfoin, compared with Alf. Protozoal numbers, RF viscosity, and total volatile fatty acids (VFA) were unaffected by sainfoin in the forage, but acetate:propionate ratios were consistently reduced (P ≤ 0.036). Extracellular polysaccharide-degrading enzyme activities in RF were increased (carboxymethylcellulase and β-glucanase, P ≤ 0.034; xylanase, P = 0.008 and 0.08) by sainfoin at ≥ 12.1%, and proteolytic activities (intracellular and extracellular) were reduced (P ≤ 0.01). Enzyme activities were unaffected by sainfoin at ≤ 9.1%. Sainfoin did not affect (P ≥ 0.202) organic matter intake from any of the pastures surveyed. Sainfoin was more effective for reducing bloat when cattle were grazing first growth pastures than when grazing re-growth. Including 35% sainfoin in mixed alfalfa-sainfoin pastures reduced, but did not eliminate, bloat in beef cattle and enhanced protein utilization by decreasing proteolytic activity. Feed efficiency may be improved through associative effects of the two forages. Key words: Alfalfa, beef cattle, feed intake, grazing, pasture bloat, sainfoin

Effect of feed additives on in vitro and in vivo rumen characteristics and frothy bloat dynamics in steers grazing wheat pasture

Research was conducted to determine the potential efficacy of feed additives (FA) to mitigate frothy bloat in yearling cattle grazing wheat pasture. Two experiments were conducted to: (1) quantify in vitro effect of FA on total rumen and methane gas production and foam potential and (2) quantify the influence of FA on rumen protein characteristics, bloat potential and weight gain of steers grazing wheat pasture. In Exp 1, duplicated analyses of in vitro gas production were measured as sequential plunger displacement (cc) at 0, 1, 2, 3, 4, 5, and 6 h incubation periods. In vitro rumen foam production and strength was measured at 0, 2, and 6 h incubation of minced wheat forage. In Exp 2, eight ruminally cannulated steers (386 ± 35.8 kg/steer) were randomly allocated to one of four FA treatments that included control, monensin, poloxalene, and condensed tannins (CT). Treatments were administered daily through rumen cannulla as pre-mixes with a mixed ration (300 mg/steer/day; as-fed basis). Steers grazed on wheat during a 2-week adaptation period prior to data collection from 05 March to 12 April, 2004. Rumen contents were collected 2 h post-FA infusion (1030 to 1130 h) on day −5, 0, 5, 15, and 22. Cattle were weighed at 28-days intervals. Bloat was visually scored weekly. In Exp 1, in vitro ruminal gas and methane gas production per gram of forage were similar between control and poloxalene, but were lower for monensin ( P<0.01) and CT ( P<0.05) treatments. The lowest ( P<0.01) in vitro foam strength occurred with the addition of poloxalene and the highest occurred in control and monensin treatments. CT was intermediate in rumen foam strength. Mean bloat score was lower in poloxalene and CT than that in monensin and control treatments. Among six-rumen protein components assayed, steers receiving CT after 10, 15, and 22 day had greater protein concentrations in whole rumen content, particulate matter, cheese-cloth filtrate, and protozoa and plant particle fractions than steers fed other treatments. Bacterial and cell-free supernatant protein fractions were comparable among treatments. Ruminal dry matter (DM) content, cell-free supernatant, protozoal and bacterial fractions were similar between the bloated and non-bloated steers. In bloated animals, ruminal pH was lower, and whole rumen content and cheese-cloth filtrate protein fractions tended to be greater ( P=0.08) than in non-bloated animals. Animal average daily gain (ADG) was not affected by FA during experimental period. The results of this trial suggest that wheat pasture bloat was associated with dietary protein and low ruminal pH. Feeding FA can be used to decrease either ruminal gas or foam production or both, and it may protect against the incidence of frothy bloat.