Ruminal buffers: temporal effects on buffering capacity and pH of ruminal fluid from cows fed a high concentrate diet

Effect of a blend of magnesium oxide on Equine Squamous Gastric Disease in young trotter horses under training

BACKGROUND

Equine squamous gastric disease (ESGD), as part of the equine gastric ulcer syndrome (EGUS), are common in racing horses. The use of buffering feed supplements to treat and/or prevent gastric ulcers is an option to control this condition.

OBJECTIVE

The purpose of this study was to evaluate the effect of a 30-day supplementation with a blend of magnesium oxide (MgO) on ESGD scores in trotters under training.

METHODS

Forty-two young trotters were submitted to a gastroscopic evaluation to assess their ESGD score and were randomly assigned in a group supplemented with MgO or in a control group. After 30 days, a second evaluation by gastroscopy was performed. The effect of the MgO supplementation was assessed by comparing the evolution of the ESGD score in supplemented and control groups between day 0 and day 30.

RESULTS

The results confirm the high prevalence of EGUS in young Trotters. The supplementation significantly decreased the ESGD scoring in the supplemented group whereas the control group remain unchanged.

CONCLUSION

The oral MgO supplementation was efficient to control ESGD in the population studied.

Increasing buffering capacity enhances rumen fermentation characteristics and alters rumen microbiota composition of high-concentrate fed Hanwoo steers

The buffering capacity of buffer agents and their effects on in vitro and in vivo rumen fermentation characteristics, and bacterial composition of a high-concentrate fed Hanwoo steers were investigated in this study. Treatments were comprised of CON (no buffer added), BC_0.3% (low buffering capacity, 0.3% buffer), BC_0.5% (medium buffering capacity, 0.5% buffer), and BC_0.9% (high buffering capacity, 0.9% buffer). Four Hanwoo steers in a 4 × 4 Latin square design were used for the in vivo trial to assess the effect of treatments. Results on in vitro experiment showed that buffering capacity, pH, and ammonia-nitrogen concentration (NH₃-N) were significantly higher in BC_0.9% and BC_0.5% than the other treatments after 24 h incubation. Individual and total volatile fatty acids (VFA) concentration of CON were lowest compared to treatment groups. Meanwhile, in vivo experiment revealed that Bacteroidetes were dominant for all treatments followed by Firmicutes and Proteobacteria. The abundances of Barnesiella intestinihominis, Treponema porcinum, and Vibrio marisflavi were relatively highest under BC_0.9%, Ruminoccocus bromii and Succiniclasticum ruminis under BC_0.5%, and Bacteroides massiliensis under BC_0.3%. The normalized data of relative abundance of observed OTUs' representative families have grouped the CON with BC_0.3% in the same cluster, whereas BC_0.5% and BC_0.9% were clustered separately which indicates the effect of varying buffering capacity of buffer agents. Principal coordinate analysis (PCoA) on unweighted UniFrac distances revealed close similarity of bacterial community structures within and between treatments and control, in which BC_0.9% and BC_0.3% groups showed dispersed community distribution. Overall, increasing the buffering capacity by supplementation of BC_0.5% and and BC_0.9% buffer agents enhanced rumen fermentation characteristics and altered the rumen bacterial community, which could help prevent ruminal acidosis during a high-concentrate diet.

Effect of dietary supplementation or cessation of magnesium-based alkalizers on milk fat output in dairy cows under milk fat depression conditions

We aimed to evaluate the effects of dietary supplementation with magnesium oxide and calcium-magnesium dolomite on milk fat synthesis and milk fatty acid profile or persistency in milk fat synthesis after their cessation in dairy cows under milk fat depression conditions. Twenty-four multiparous dairy cows in early lactation (mean ± standard deviation; 112 ± 14 d in milk) were used in a randomized complete block design. Milk fat depression was induced in all cows for 10 d by feeding a diet containing 35.2% starch, 28.7% neutral detergent fiber, and 4.8% total fatty acid (dry matter). The experiment was conducted in 2 periods. During the Mg-supplementation period (d 1-20), cows were randomly assigned to (1) the milk fat depression diet used during the induction phase (control; n = 8), (2) the control diet plus 0.4% magnesium oxide (MG; n = 8), or (3) the control diet plus 0.8% calcium-magnesium dolomite (CMC; n = 8). Compared with the control group, feeding the magnesium-supplemented diets increased milk fat concentration and yield by 12% within 4 d. During the 20-d Mg-supplementation period, both the MG and CMC diets increased milk fat concentration and yield, as well as 3.5% fat-corrected milk and energy-corrected milk yield, without affecting dry matter intake, milk yield, and milk protein and lactose concentrations. In the Mg-cessation period (d 21-30), all cows received the control diet, which resulted in a greater milk fat concentration and yield in the cows that had already received the MG and CMC diets in the Mg-supplementation period. Whereas, milk fat concentration and yield remained high after discontinuation of the magnesium-containing alkalizer until d 27. The difference in milk fat synthesis was associated with lower trans-10 C18:1 (-22%) and higher trans-11 C18:1 (+12.5%) concentrations in milk during the Mg-supplementation period. Furthermore, it was evident that within 2 d of supplementation, the trans-10:trans-11 ratio was lower in MG and CMC cows compared with cows receiving the control. This suggested that the effect of magnesium-based alkalizers on milk fat synthesis was mediated via a shift in ruminal biohydrogenation of cis-9,cis-12 C18:2 in the rumen. In conclusion, abrupt addition of magnesium oxide and calcium-magnesium dolomite increased milk fat synthesis, which persisted for 7 d after cessation of magnesium-based alkalizers. A similar ability to recover milk fat synthesis and normal fatty acid biohydrogenation pathways was observed for magnesium oxide and calcium-magnesium dolomite.

Supplementing a blend of magnesium oxide to feedlot cattle: effects on ruminal, physiological, and productive responses

This experiment evaluated ruminal, physiological, and productive responses of feedlot cattle consuming a corn-based finishing diet that included different levels of a magnesium oxide (MG) blend. Yearling cattle (58 heifers and 62 steers) were ranked by sex and initial body weight (BW; 407 ± 3.1 kg), and allocated to 4 groups of 30 animals each. Groups were housed in one of four drylot pens (30 × 12 m) equipped with GrowSafe automated feeding systems (Model 6000E, 4 bunks/pen) during the experiment (days -14 to 117). On day 0, groups were randomly assigned to receive a total-mixed ration without (CON; n = 30) or with the inclusion (as-fed basis) of MG at 0.25% (MG25; n = 30), 0.50% (MG50; n = 30), or 0.75% (MG75; n = 30) until slaughter on day 118. Individual feed intake was recorded daily, and BW was recorded every 14 d and prior to slaughter (day 117). Blood samples were collected on days 0, 28, 56, 84, and 112, and hair samples were collected on days 0, 56, and 112 from the tail-switch. On day 42, eight rumen-cannulated steers (BW = 492 ± 8.0 kg) were housed with yearling cattle (1 pair/pen). Pairs rotated among groups every 14 d, resulting in a replicated 4 × 4 Latin square design (n = 8/treatment; days 42 to 98). Rumen pH was measured on days 7 and 14 of each period (0800, 1200, 1600, and 2000 h). Orthogonal contrasts were used to determine if inclusion of MG (0%, 0.25%, 0.50%, or 0.75% of the diet) yielded linear or quadratic effects, and to explore overall effect of MG supplementation (CON vs. MG25 + MG50 + MG75). No treatment differences were noted (P ≥ 0.31) for BW gain, feed intake, or feed efficiency. Cattle supplemented with MG tended to have less carcass marbling (P = 0.07) compared with CON. Inclusion of MG linearly increased (P < 0.01) mean plasma concentrations of magnesium and tended to linearly decrease (P = 0.09) mean plasma concentrations of haptoglobin. Cattle supplemented with MG had greater (P < 0.01) mean plasma concentrations of cortisol compared with CON. Hair cortisol concentration did not differ between treatments on day 56 (P ≥ 0.25) and linearly decreased (P < 0.01) with MG inclusion on day 112 (treatment × day; P = 0.02). Inclusion of MG linearly increased (P = 0.03) mean rumen pH, but these outcomes were mostly noted during the last two sampling of the day (treatment × hour; P = 0.02). Collectively, supplemental MG was effective in controlling rumen pH in cattle receiving a corn-based finishing diet, but without improvements in feedlot performance and carcass merit.

Determination of Various Parameters during Thermal and Biological Pretreatment of Waste Materials

Pretreatment of waste materials could help in more efficient waste management. Various pretreatment methods exist, each one having its own advantages and disadvantages. Moreover, a certain pretreatment technique might be efficient and economical for one feedstock while not for another. Thus, it is important to analyze how parameters change during pretreatment. In this study, two different pretreatment techniques were applied: thermal at lower and higher temperatures (38.6 °C and 80 °C) and biological, using cattle rumen fluid at ruminal temperature (≈38.6 °C). Two different feedstock materials were chosen: sewage sludge and riverbank grass (Typha latifolia), and their combinations (in a ratio of 1:1) were also analyzed. Various parameters were analyzed in the liquid phase before and after pretreatment, and in the gas phase after pretreatment. In the liquid phase, some of the parameters that are relevant to water quality were measured, while in the gas phase composition of biogas was measured. The results showed that most of the parameters significantly changed during pretreatments and that lower temperature thermal and/or biological treatment of grass and sludge is suggested for further applications.

Effects of calcium carbonate, magnesium oxide and encapsulated sodium bicarbonate on measures of post-ruminal fermentation

Evidence suggests that lipopolysaccharide (LPS) absorbed from the large intestine may contribute to the inflammatory response to high starch feeding in dairy cows. This work evaluated the impact of buffers or alkalinizing agents with expected large intestinal activity on faecal indicators of intestinal fermentation and LPS. Ten late-lactation cows were used in a replicated 5 × 5 Latin square design with 7-day periods. Cows were fed a diet containing 265 g/kg dry matter of starch and were abomasally infused with 1 g/kg body weight cornstarch daily. Treatments were control (CON), ration supplementation with 200 g/day sodium bicarbonate (FSB), 200 g/day calcium carbonate (FCC) or 125 g/day calcium carbonate plus 75 g/day of magnesium oxide (FCCM), or abomasal infusion of a lipid encapsulate providing 200 g/day sodium bicarbonate (ISB). The FCC, FCCM and ISB treatments were hypothesized to have large intestinal buffering effects, and FSB was included as a secondary control. Milk, feed, rumen and faecal samples were collected on day 7 of each period. Treatment did not affect intake, milk yield or milk composition. There were no effects of treatment on ruminal measures except that ISB tended to reduce and the post-ruminal treatments as a whole (FCC, FCCM and ISB) reduced rumen butyrate compared with CON. Faecal pH was greater for FCCM compared with all other treatments. Total faecal VFA tended to increase with FCC and FCCM compared with CON and was increased by the post-ruminal treatments as a whole compared with CON. Treatment did not affect faecal dry matter, lactate or LPS or apparent total tract nutrient digestibility. Although some treatments altered fermentation as evidenced by the change in faecal VFA, this was not accompanied by a decrease in faecal LPS. The strategies employed in this study had limited effects on large intestinal fermentation.

Exclusion of dietary sodium bicarbonate from a wheat-based diet: effects on milk production and ruminal fermentation

Milk production, rumen fermentation, and whole-tract apparent nutrient digestibility in response to feeding 20% steam-rolled wheat with or without sodium bicarbonate were evaluated in 12 Holstein cows averaging 165±16 DIM. Cows were fed 1 of 2 isoenergetic and isonitrogenous diets containing either 0 or 0.75% sodium bicarbonate on a DM basis for 21 d in a crossover design. Rumen fluid samples were obtained 18 times during the last 2 d of each period, and fecal samples were collected on 12 occasions from d 18 to 21 of each period. Removal of sodium bicarbonate from the diet did not affect DMI (21.0 kg/d), yields of milk (30.8 kg/d), or milk components (1.16, 1.01, and 1.40 kg/d for fat, protein, and lactose, respectively). Whole-tract apparent digestibility of DM, CP, ADF, and NDF did not differ between the 2 treatments (75.3, 76.6, 67.2, and 63.6%, respectively). The mean rumen pH was 6.24 and was not affected by excluding sodium bicarbonate from the diet. Rumen NH3-N (12.31 mg/dL) and lactic acid (3.63 mM) concentrations were not different, whereas total volatile fatty acids concentration tended to increase when sodium bicarbonate was present in the diet (110 vs. 116 mM). However, average concentrations of the individual volatile fatty acids, as a proportion of total volatile fatty acids, were not affected by treatment. In conclusion, dairy cow diets can include up to 20% steam-rolled wheat without the need for added sodium bicarbonate as long as the diets are formulated to meet the fiber requirements of the cow.

Effects of calcium magnesium carbonate and roughage level on feedlot performance, ruminal metabolism, and site and extent of digestion in steers fed high-grain diets

A feedlot growth performance experiment and 2 metabolism experiments were conducted to evaluate dietary roughage concentration and calcium magnesium carbonate in steers fed a high-grain diet. In Exp. 1, one hundred ninety-two crossbred yearling steers (320 +/- 10 kg of initial BW) were fed diets based on steam-flaked corn with 0, 0.75, or 1.5% CaMg(CO(3))(2). There were no effects (P > or = 0.13) on ADG, DMI, G:F, or total water intake due to CaMg(CO(3))(2). In Exp. 2, five ruminally and duodenally fistulated steers (263 +/- 9 kg of initial BW) were used in a 5 x 5 Latin square design, with 5 dietary treatments arranged in a 2 x 2 + 1 factorial: 1) 3.8% dietary roughage and no CaMg(CO(3))(2); 2) 7.6% dietary roughage and no CaMg(CO(3))(2); 3) 11.4% dietary roughage and no CaMg(CO(3))(2); 4) 3.8% dietary roughage and 1.5% CaMg(CO(3))(2); and 5) 7.6% dietary roughage and 1.5% CaMg(CO(3))(2). Water consumption was less (quadratic, P = 0.003) when 7.6% dietary roughage was fed compared with 3.8 or 11.4% dietary roughage. Intake of DM was not affected (P > or = 0.16) by dietary roughage or by CaMg(CO(3))(2). Poststomach and total tract starch digestion decreased (linear, P < 0.01) as dietary roughage increased. Ruminal pH tended (P = 0.08) to increase as dietary roughage increased but was not affected (P = 0.60) by CaMg(CO(3))(2). In Exp. 3, DMI and ruminal pH were continuously monitored in a 6 x 6 Latin square design using 6 ruminally and duodenally fistulated Holstein steers (229 +/- 10 kg of initial BW). A 3 x 2 factorial treatment structure was utilized, with factors consisting of dietary roughage concentration (4.5, 9.0, or 13.5%) and CaMg(CO(3))(2) inclusion (0 or 1.0%) to replace MgO and partially replace lime-stone. A dietary roughage x CaMg(CO(3))(2) interaction (P = 0.01) occurred as steers consuming 13.5% roughage, 1.0% CaMg(CO(3))(2) had greater DMI per meal than those consuming 4.5% dietary roughage, no CaMg(CO(3))(2) and 9.0% dietary roughage, 1.0% CaMg(CO(3))(2). Steers consuming 13.5% dietary roughage, 1.0% CaMg(CO(3))(2) and 9.0% dietary roughage, no CaMg(CO(3))(2) had greater meal length (min/meal; P = 0.01) than steers consuming 4.5% dietary roughage, no CaMg(CO(3))(2). Total tract OM digestibility decreased linearly (P = 0.01), and ruminal pH increased linearly (P = 0.01) with increasing dietary roughage concentration. Inclusion of CaMg(CO(3))(2) can replace limestone and MgO but did not produce ruminal pH responses similar to those observed by increasing dietary roughage in high-concentrate diets.

Modeling ruminal pH fluctuations: interactions between meal frequency and digestion rate

A steady periodic analysis of ruminal carbohydrate digestion was developed to predict the effects of diet and frequency of eating on ruminal pH fluctuation. Tests of the model against previous data showed that pH fluctuations were too large when previously published rates of carbohydrate digestion were used but were improved using rates from an in vitro gas production system, which were lower. With the original digestion rates, the minimum meal frequency to maintain steady-state conditions in the rumen increased from 4 to 12 meals/d as dietary effective neutral detergent fiber (NDF) decreased from 34 to 6% of dry matter (DM); with the revised rates, the minimum frequency was 3 to 6 meals/d, respectively. The minimum effective NDF to maintain a pH value above 6.0 increased from 14 to 23% of DM as meal frequency decreased from steady state to 2 meals/d using the original rates; with the revised rates, the minimum effective NDF was slightly smaller, increasing from 13 to 21% of DM, respectively. Effects of DM intake and body weight on pH fluctuation were minor, and dietary buffers, when used at rates less than 1%, did not reduce fluctuation. Different methods of calculating mean ruminal pH yielded different results for the effect of meal frequency on mean pH.

Natural sodium sesquicarbonate fed for an entire lactation: influence on performance and acid-base status of dairy cows

Forty-eight multiparous Holstein cows were blocked according to month of parturition, age, and previous milk yield and arranged in a randomized complete block design to evaluate the effect of a naturally occurring sodium sesquicarbonate on DMI, milk yield, milk composition, milk value, and systemic acid-base status. Cows were assigned at parturition to diets containing sorghum silage, alfalfa hay, concentrate, and 0 or 1% naturally occurring sodium sesquicarbonate (DM basis); cows were fed these diets for 308 d postpartum. Blood was collected every 4 wk via jugular venipuncture for analysis of pH, HCO3, partial pressure of O2, and partial pressure of CO2. Sesquicarbonate exhibited alkalogenic properties by increasing blood HCO3, partial pressure of CO2, and total CO2 for the 308-d lactation. Buffer tended to increase DMI and increased milk protein throughout lactation. During 0 to 56 d postpartum, sodium sesquicarbonate did not affect milk yield or composition. In midlactation (56 to 252 d postpartum), buffer increased milk protein content only. During 252 to 308 d postpartum, milk fat and protein contents increased with buffer supplementation. Hence, the value of milk yielded daily was similar for all cows. Effects of dietary buffer on all variables were more pronounced during late lactation.

Another theory for the action of ruminal buffer salts: decreased starch fermentation and propionate production

Sodium carbonates have been fed to ruminants for more than 20 yr and, in many cases, have alleviated milk fat depression. These effects usually have been ascribed to increased ruminal buffering capacity, but this mode of action has several problems. For the buffering capacity to increase, the concentrations of ruminal bicarbonate, dissolved CO2, and Na have to increase. Ruminal fluid already is saturated with CO2, and the cation concentration of ruminal fluid is regulated closely to prevent hemoconcentration or hemodilution. Based on these latter observations, a significant increase in ruminal buffering capacity is unlikely. The action of bicarbonates is explained more easily by increased water intake, increased ruminal fluid dilution rate, increased flow of undegraded starch from the rumen, and decreased ruminal propionate production.

Sodium bicarbonate or multielement buffer via diet or rumen: effects on performance and acid-base status of lactating cows

Our objective was to compare the influence of dietary NaHCO3 and a multielement buffer on ruminal acid-base status and lactation performance of dairy cows. Five ruminally fistulated, primiparous and multiparous lactating Holstein cows averaging 123 +/- 21 d postpartum were assigned randomly to treatments in a 5 x 5 Latin square with 3-wk experimental periods. Treatments were a basal diet without supplemental buffers, with 1.5% NaHCO3 or 1.5% multielement buffer, or with NaHCO3 or multielement buffer solutions poured into the rumen via cannula at 2 h postfeeding. Addition of either buffer to the diet reduced ruminal fluid hydrogen ion concentration from 0 to 6 h postfeeding; only NaHCO3 reduced ruminal fluid acidity when dosed via the cannula. Addition of buffers via ruminal cannula appeared to retard the reduction in ruminal fluid acidity that normally occurs from 6 to 12 h postfeeding; this may have been related to a feedback mechanism inhibiting salivary buffer secretion. Buffering capacity of ruminal fluid tended to increase with buffer addition; the increase was greatest during infusion of NaHCO3. The ruminal fluid buffer value index increased by 4 units for control cows from early (0 to 6 h) to late (6 to 12) postfeeding; smaller increases were noted for addition of multielement buffer. This index was not different for NaHCO3 during these two intervals. Milk yield and DMI were not affected by buffer addition. Although milk fat content tended to be higher with the multielement buffer than with NaHCO3, it was not accompanied by the expected alterations in ruminal acid-base status. Therefore, this increase may be related to systemic effects of specific minerals in the multielement buffer rather than to a more stable ruminal environment. Based on the ruminal fluid buffer value index, NaHCO3 tended to maintain the most stable ruminal acid-base status.