Application of a hand-held laser methane detector for measuring enteric methane emissions from cattle in intensive farming.

The hand-held laser methane detector (LMD) technique has been suggested as an alternative method for measuring methane (CH4) emissions from enteric fermentation of ruminants in the field. This study aimed to establish a standard procedure for using LMD to assess CH4 production in cattle and evaluate the efficacy of the protocol to detect differences in CH4 emissions from cattle fed with diets of different forage-to-concentrate (FC) ratios. Experiment 1 was conducted with four Hanwoo steers (584 ± 57.4 kg body weight [BW]) individually housed in metabolic cages. The LMD was installed on a tripod aimed at the animal's nostril, and the CH4 concentration in the exhaled gas was measured for 6 min every hour for 2 consecutive days. For the data processing, the CH4 concentration peaks were identified by the automatic multi-scale peak detection algorithm. The peaks were then separated into those from respiration and eructation by fitting combinations of two of the four distribution functions (normal, log-normal, gamma, and Weibull) using the mixdist R package. In addition, the most appropriate time and number of consecutive measurements to represent the daily average CH4 concentration were determined. In experiment 2, 30 Hanwoo growing steers (343 ± 24.6 kg BW), blocked by BW, were randomly divided into three groups. Three different diets were provided to each group: high FC ratio (35:65) with low-energy concentrate (HFC-LEC), high FC ratio with high-energy concentrate (HFC-HEC), and low FC ratio (25:75) with high-energy concentrate (LFC-HEC). After 10 d of feeding the diets, the CH4 concentrations for all steers were measured and analyzed in duplicate according to the protocol established in experiment 1. In experiment 1, the mean correlation coefficient between the CH4 concentration from respiration and eructation was highest when a combination of two normal distributions was assumed (r = 0.79). The most appropriate measurement times were as follows: 2 h and 1 h before, and 1 h and 2 h after morning feeding. Compared with LFC-HEC, HFC-LEC showed 49% and 57% higher CH4 concentrations in exhaled gas from respiration and eructation (P < 0.01). In conclusion, the LMD method can be applied to evaluate differences in CH4 emissions in cattle using the protocol established in this study.

The hand-held laser methane detector (LMD) technique has been suggested as a potential method for measuring methane (CH4) emissions from enteric fermentation of ruminants in the field. This study aimed to establish a standard procedure for using LMD to assess CH4 production in cattle and evaluate the efficacy of the protocol to detect differences in CH4 emissions from cattle fed with diets of different forage-to-concentrate (FC) ratios which is known to affect CH4 emissions. Experiment 1 was conducted to establish a protocol for measuring and analyzing the CH4 emissions from cattle using LMD. In experiment 2, 30 Hanwoo growing steers were divided into three groups and fed with a diet of high FC ratio (35:65) with low-energy concentrate (HFC-LEC), high FC ratio (35:65) with high-energy concentrate (HFC-HEC), or low FC ratio (25:75) with high-energy concentrate (LFC-HEC). The CH4 concentrations for all steers were measured in duplicate according to the protocol established in experiment 1. HFC-LEC showed 49% and 57% higher CH4 concentrations in exhaled gas from respiration and eructation, respectively (P < 0.01), than LFC-HEC. In conclusion, the LMD method can be applied to evaluate differences in CH4 emissions in cattle using the protocol established in this study.

Characterization and mechanisms of the supragastric belch in the cat.

A response in which a belch occurs without gastric involvement, i.e., the supragastric belch (SGB), has been characterized in humans. The aims of this study were to determine whether animals have an SGB and, if so, to determine its mechanisms. Studies were conducted in decerebrate cats (n = 30) with electromyographic electrodes on hyoid, pharyngeal, esophageal, and diaphragm muscles. The effects of distending different regions of the esophagus in different manners using a balloon were quantified to determine the most appropriate stimulus for activating the cat SGB. The effects of esophageal perfusion of lidocaine (n = 3), vagus nerve transection (n = 3), or esophageal acidification (n = 5) on activation of the SGB were determined. Rapid large distensions of the thoracic esophagus best activated responses similar to the human SGB, i.e., rapid inhalation followed by a belch. The rapid inhalation was associated with activation of hiatal fibers and the belch with activation of dome fibers of the diaphragm. The rapid inhalation response was independent of the belch response. Lidocaine perfusion of the esophagus blocked the belch response without blocking the rapid inhalation, HCl perfusion sensitized the esophagus to activation of both the rapid inhalation and the belch response, and vagotomy blocked both responses. We conclude that the cat has an SGB that is composed of two independent reflex responses, i.e., rapid inhalation and belch, that are mediated by the vagus nerves and tension/mucosal receptors of the esophagus and sensitized by esophageal acid exposure. We hypothesize that the SGB is a learned voluntarily activated reflex response.NEW & NOTEWORTHY Rapid strong distension of the thoracic esophagus activates rapid inhalation followed by a belch, which is the sequence of responses that compose the human supragastric belch (SGB). The rapid inhalation and belch phases of the cat SGB are activated by hiatal and dome fibers of the diaphragm, respectively, and are mediated by the vagus nerves and tension/mucosal receptors of the esophagus and sensitized by esophageal acid exposure. There are many similarities between the cat and human SGB.

Methane emissions among individual dairy cows during milking quantified by eructation peaks or ratio with carbon dioxide.

The aims of this study were to compare methods for examining measurements of CH4 and CO2 emissions of dairy cows during milking and to assess repeatability and variation of CH4 emissions among individual dairy cows. Measurements of CH4 and CO2 emissions from 36 cows were collected in 3 consecutive feeding periods. In the first period, cows were fed a commercial partial mixed ration (PMR) containing 69% forage. In the second and third periods, the same 36 cows were fed a high-forage PMR ration containing 75% forage, with either a high grass silage or high maize silage content. Emissions of CH4 during each milking were examined using 2 methods. First, peaks in CH4 concentration due to eructations during milking were quantified. Second, ratios of CH4 and CO2 average concentrations during milking were calculated. A linear mixed model was used to assess differences between PMR. Variation in CH4 emissions was observed among cows after adjusting for effects of lactation number, week of lactation, diet, individual cow, and feeding period, with coefficients of variation estimated from variance components ranging from 11 to 14% across diets and methods of quantifying emissions. No significant difference was detected between the 3 PMR in CH4 emissions estimated by either method. Emissions of CH4 calculated from eructation peaks or as CH4 to CO2 ratio were positively associated with forage dry matter intake. Ranking of cows according to CH4 emissions on different diets was correlated for both methods, although rank correlations and repeatability were greater for CH4 concentration from eructation peaks than for CH4-to-CO2 ratio. We conclude that quantifying enteric CH4 emissions either using eructation peaks in concentration or as CH4-to-CO2 ratio can provide highly repeatable phenotypes for ranking cows on CH4 output.

Variation in enteric methane emissions among cows on commercial dairy farms.

Methane (CH4) emissions by dairy cows vary with feed intake and diet composition. Even when fed on the same diet at the same intake, however, variation between cows in CH4 emissions can be substantial. The extent of variation in CH4 emissions among dairy cows on commercial farms is unknown, but developments in methodology now permit quantification of CH4 emissions by individual cows under commercial conditions. The aim of this research was to assess variation among cows in emissions of eructed CH4 during milking on commercial dairy farms. Enteric CH4 emissions from 1964 individual cows across 21 farms were measured for at least 7 days/cow using CH4 analysers at robotic milking stations. Cows were predominantly of Holstein Friesian breed and remained on the same feeding systems during sampling. Effects of explanatory variables on average CH4 emissions per individual cow were assessed by fitting a linear mixed model. Significant effects were found for week of lactation, daily milk yield and farm. The effect of milk yield on CH4 emissions varied among farms. Considerable variation in CH4 emissions was observed among cows after adjusting for fixed and random effects, with the CV ranging from 22% to 67% within farms. This study confirms that enteric CH4 emissions vary among cows on commercial farms, suggesting that there is considerable scope for selecting individual cows and management systems with reduced emissions.

Calculation of the buffering capacity of bicarbonate in the rumen and in vitro.

We describe a model to calculate the buffering capacity of bicarbonate in the rumen. The addition of NaHCO3 results in the release of CO2 from solution and eventually from the rumen via eructation. This process directly neutralizes ruminal acidity. The degree to which the process continues depends on the partial pressure of CO2 in the gas phase, the pH, and a constant (7.74), according to the Henderson-Hasselbalch equation: pH = 7.74 + log([HCO3-]/pressure of CO2 in atmospheres). The addition of NaHCO3 to buffer solutions and ruminal fluid under high pressure of CO2 increased pH as predicted. The buffering capacity of ruminal fluid under CO2 was greater at low pH than was previously determined by titration in air. In contrast, in vitro systems in which CO2 is not permitted to escape may result in reduced buffering capacity. In vitro systems in which excess CO2 may escape (under N2 gas pressure) may result in uncontrolled pH elevation. Dilution of ruminal fluid under constant pressure of CO2 decreased ruminal pH as predicted by the model. The pH under different pressures at equilibrium and the buffering capacity are easily calculated for in vitro and in vivo systems.

Ventilatory effects of the single-breath CO2 test, compared with eructation, in cattle.

OBJECTIVE: To assess the peripheral chemoreceptor-induced ventilatory response to single tidal-breath CO2 (SB CO2) tests, compared with eructations, in 2 breeds of calves. ANIMALS: 13 conscious unsedated Holstein-Friesian and 8 Belgian White and Blue hypermuscled calves. PROCEDURE: An SB of +/- 50% CO2 in equal parts of O2 and N2 was inhaled. Ventilatory response was determined from the increase in ventilation (delta Ve) during the first 20 seconds after the test breath or eructation and from the difference in end-tidal PCO2 between the stimulus and preceding control breaths. RESULTS: Because no difference was found between the 2 breeds of calves, all data were pooled. The increase in Ve peaked during the fifth breath after the SB CO2 test on average, corresponding to a delay of 12.4 seconds. The SB CO2 responses ranged from 0.037 to 0.151 L/min.mm of Hg.m2, with a mean +/- SD of 0.082 +/- 0.032 L/min.mm of Hg.m2 for all calves. The SB CO2 tests, similar to eructations, modified the breathing pattern significantly and in the same direction, by principally shortening expiratory time and increasing mean inspiratory flow. After eructations, Ve peak increase was more important for lower difference in end-tidal PCO2 between the stimulus and preceding control breaths and took place more rapidly than after SB CO2 tests. Accordingly, eructation responses were more marked than SB CO2 responses and averaged 0.925 +/- 0.276 L/min.mm of Hg.m2. CONCLUSIONS AND CLINICAL RELEVANCE: In cattle, the pattern of breathing and ventilation under basal conditions is characterized by a cyclic variability coupled to eructation.

Methane emissions from cattle.

Increasing atmospheric concentrations of methane have led scientists to examine its sources of origin. Ruminant livestock can produce 250 to 500 L of methane per day. This level of production results in estimates of the contribution by cattle to global warming that may occur in the next 50 to 100 yr to be a little less than 2%. Many factors influence methane emissions from cattle and include the following: level of feed intake, type of carbohydrate in the diet, feed processing, addition of lipids or ionophores to the diet, and alterations in the ruminal microflora. Manipulation of these factors can reduce methane emissions from cattle. Many techniques exist to quantify methane emissions from individual or groups of animals. Enclosure techniques are precise but require trained animals and may limit animal movement. Isotopic and nonisotopic tracer techniques may also be used effectively. Prediction equations based on fermentation balance or feed characteristics have been used to estimate methane production. These equations are useful, but the assumptions and conditions that must be met for each equation limit their ability to accurately predict methane production. Methane production from groups of animals can be measured by mass balance, micrometeorological, or tracer methods. These techniques can measure methane emissions from animals in either indoor or outdoor enclosures. Use of these techniques and knowledge of the factors that impact methane production can result in the development of mitigation strategies to reduce methane losses by cattle. Implementation of these strategies should result in enhanced animal productivity and decreased contributions by cattle to the atmospheric methane budget.

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.

[Stomach ulcers in the horse--clinical and gastroscopic findings in 12 horses (1989-1990)]. / Magenulzera beim Pferd--klinische und gastroskopische Befunde bei 12 Pferden (1989-1990).

Twelve horses with clinical symptoms of a gastric disorder were studied by gastroscopy. Symptoms of gastric disorders were periprandial colic, bruxism, ructus and reflux. Preliminary to gastroscopy the horses were fasted for 24 h. Access to water was not restricted. The gastroscopy could be conducted easily using a fiberscope 2.5 m in length and 11 mm in outer diameter. While ulcers were present in the squamous fundus of all horses only one horse showed ulceration of the glandular fundus. Solitary ulcers near the margo plicatus were found in horses with mild clinical symptoms. In contrast, diffuse gastroesophageal ulceration was accompanied by severe clinical symptoms. Four horses were affected by an acute gastroesophageal ulceration with gastric reflux and subsequent aspiration pneumonia. Two of those horses suffered from acute gastric ulceration 3-4 days following laparatomy. All horses were treated with cimetidine (5 mg/kg bwt/q.i.d.) until clinical symptoms ceased.

Eructation of gas through the gastroesophageal sphincter before and after limiting distension of the gastric cardia or infusion of a beta-adrenergic amine in dogs.

Gas eructation function of the gastroesophageal sphincter (GES) was investigated in 6 conscious dogs before and after a sleeve was placed around the GES and gastric cardia and during IV infusion of a beta-adrenergic amine (epinephrine). To induce eructation, nitrogen gas was insufflated (351.4 +/- 2 ml/min; mean +/- SEM) into the stomach through 1 channel of a 4-lumen catheter. After baseline studies and epinephrine infusion studies were completed in each dog, surgery was done to limit partially gastric distension by intraluminal contents by placing a silicone rubber sleeve around the GES and the first few centimeters of the cardia. Gastroesophageal sphincter pressure was 31.8 +/- 2.2 mm of Hg in baseline studies, 17.3 +/- 1.3 mm of Hg during epinephrine infusion (P. less than 0.003), and 30.3 +/- 2.2 mm of Hg after the sleeve was placed around the GES and cardia. During insufflation, gastric pressures before eructation increased to 5.74 +/- 0.41 mm of Hg before and to 15.15 +/- 1.63 mm of Hg after cardia sleeve placement (P less than 0.001). Eructation occurred at intervals of 1.83 +/- 0.41 minutes before cardia sleeve placement, and eructations were not observed with the sleeve in place. Before the sleeve was placed, administration of epinephrine resulted in an eructation interval of 0.84 +/- 0.09 minutes, which was significantly different from that in the same dogs given no drugs (P less than 0.004).(ABSTRACT TRUNCATED AT 250 WORDS)

Eructation of gas through the gastroesophageal sphincter before and after gastric fundectomy in dogs.

The gas eructation function of the gastroesophageal sphincter (GES) was investigated in 6 conscious, fed dogs before and after gastric fundectomy. Using a perfused 4-lumen catheter with a Dent sleeve, gastric and GES pressures were measured. To induce eructation, nitrogen gas was insufflated (440 ml/min) into the stomach through one channel of the catheter. After base-line studies were completed on each dog, fundectomy, to remove 30% of the stomach, was performed. Mean (+/- SEM) GES pressure was 45.3 +/- 3.3 mm of Hg before fundectomy and 41.4 +/- 1.9 mm of Hg after fundectomy (P greater than 0.05). Before fundectomy, treatment with metoclopramide or cisapride increased GES pressure to 62.2 +/- 4.1 mm of Hg (P less than 0.001) and 61.1 +/- 5.0 mm of Hg (P less than 0.05), respectively. Gastric contraction rates were the same, 4.92 +/- 0.24/min and 4.80 +/- 0.16/min before and after fundectomy, respectively. During insufflation, gastric pressures before eructation increased to 12.2 +/- 1.3 mm of Hg before fundectomy and to 13.6 +/- 0.9 mm of Hg after fundectomy (P greater than 0.05). Eructation occurred at intervals of 1.44 +/- 0.20 minutes before fundectomy and 1.56 +/- 0.13 minutes after fundectomy (P greater than 0.05). Before fundectomy, administration of metoclopramide or cisapride resulted in eructation intervals of 1.72 +/- 0.21 minutes and 1.39 +/- 0.02 minutes, respectively; these intervals were not significantly different from those measured in dogs not given drugs. After fundectomy, the GES pressure in 5 dogs decreased and remained low during insufflation. After a series of normal eructation intervals, multiple eructations were observed in 4 of these dogs. Fundectomy did not impair ability to eructate gas from the stomach.

Eructation of gas through the gastroesophageal sphincter before and after truncal vagotomy in dogs.

The function of the gastroesophageal sphincter (GES) to eructate gas before and after vagotomy was investigated in conscious, fed dogs. Gastric and GES pressures were measured in 5 dogs, using a perfused 4-lumen catheter with a Dent sleeve. To induce eructation, nitrogen gas was insufflated (440 ml/min) into the stomach through 1 channel of the catheter. After base-line studies were completed on each dog, bilateral truncal vagotomy was performed 5 cm cranial to the diaphragm. Mean (+/- SE) GES pressure was 51.5 +/- 1 mm of Hg before vagotomy and 28 +/- 1.7 mm of Hg after vagotomy (P less than 0.001). Mean gastric contraction rates were the same, 4.91 +/- 0.11/min and 4.78 +/- 0.06/min in dogs before and after vagotomy, respectively. During insufflation, gastric pressures increased to 11.8 +/- 0.7 mm of Hg before eructation in dogs before vagotomy and to 18.4 +/- 0.8 mm of Hg in dogs after vagotomy (P less than 0.001). Eructation occurred at intervals of 1.79 +/- 0.09 minutes before vagotomy and 5.71 +/- 0.41 minutes after vagotomy (P less than 0.001). Atropine resulted in an interval of 1.98 +/- 0.18 minutes before vagotomy. Eructation was not seen in 2 dogs after vagotomy and was sometimes not seen in the 3 others. Gastroesophageal sphincter pressure in dogs before vagotomy began to decrease 4.5 +/- 0.2 s before the GES-pressure gradient disappeared, and GES pressure remained there for 5.3 +/- 0.3 s before the gradient began to return.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleviation of excessive gas accumulation in the ruminant stomach by ritanserin.

The relationships between forestomach motility and eructation rate were studied in sheep and cattle. Three ewes and 2 heifers were implanted with strain gauges on the reticulo-rumen and fitted with a cannula in the dorsal sac of the rumen. Studies were performed in sheep after induction of hypocalcemia by Na2EDTA infusion and cattle were studied after ruminal distension. Experiments were performed by measuring the rate and volume of eructated ruminal gases, using a technique by which the trachea is transected. The frequency of reticulo-ruminal contractions decreased 40% within 30 minutes of Na2EDTA infusion to the sheep. The volume of eructated gas (for 30-minute periods) decreased from 10.7 L to 5.5 L at the end of the 60-minute infusion period. Pretreatment with ritanserin (0.1 mg/kg, subcutaneously) not only prevented bloating during the ruminal stasis induced by hypocalcemia, but also significantly increased the eructated volume of gas. In cattle, ritanserin given at the same dose level (0.1 mg/kg, subcutaneously) significantly increased the volume of eructated gas after ruminal distension. This study supports the hypothesis that the caudal esophageal sphincter has a role in the rate of ruminal gas eructation and indicates that its relaxation may be due to a 5-hydroxytryptamine antagonist.

Effects of dopamine and serotonin on eructation rate and ruminal motility in sheep.

The relationships between forestomach motility and eructation rate were studied during dopamine infusion (2 sheep) and serotonin infusion (2 sheep). The sheep were chronically fitted with strain gauges on the reticulorumen and with a cannula in the dorsal sac of the rumen. A tracheotomy was performed to intercept the eructated gases and to permit measurement of their volume. To maintain a regular rate of eructation during the control periods, experiments were performed with a moderately increased intraruminal pressure obtained by continuous ruminal insufflation of nitrogen. Dopamine and serotonin were infused (IV for 10 minutes) at rates of 25, 50, and 100 micrograms/kg/min and 4, 8, and 16 micrograms/kg/min, respectively. Dopamine and serotonin both decreased the frequency of primary contractions. Dopamine reduced the amplitude of secondary contractions, whereas serotonin increased the forestomach tone and suppressed secondary contractions which were replaced by unpropagated eructative contractions. These motility changes were associated with a decrease in eructation rate during dopamine infusion and an increase in the eructation rate during serotonin infusion. After dopamine infusion was stopped, rebounds of eructation rate and rumen motility were observed which disappeared when a constant intraruminal pressure was maintained, indicating that the rumen reacts to its own distention. Sulpiride, but not phentolamine or propranolol, blocked the effects of dopamine. The effects of serotonin were abolished by methysergide, but were unaffected by imipramine. Therefore, seemingly dopamine acts through specific dopaminergic receptors and serotonin impringes on smooth muscle serotoninergic receptors. Finally, the use of dopamine and serotonin revealed that close relationships exist between the eructation rate and the pattern of ruminoreticular motility which may be preponderant against the cardia tone in the elimination of ruminal gases.