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PubMed1988

Performance and ruminal changes of early-weaned calves fed lasalocid.

Twenty-two neonatal calves were assigned to a control or lasalocid-fed group and weaned at 3 wk of age. They were fed a prestarter diet from 3 d of age until they consumed 227 g/d and then a mixture of 227 g prestarter daily and starter diet in ad libitum amounts. The lasalocid-fed group received lasalocid in milk at 1 mg/kg body weight daily from 4 to 7 d and at .5 mg/kg body weight daily in milk and medicated prestarter diet (88 mg lasalocid/kg) during the 2nd wk. After 2 wk, lasalocid-fed calves were given medicated prestarter and starter (44 mg lasalocid/kg) diets. Four calves in each group were ruminally cannulated at 3 to 5 d of age, and ruminal contents were obtained at weekly intervals to monitor microbial activity. Rectal fecal samples were collected from all calves and examined for coccidial oocysts. Lasalocid-fed calves had a greater weekly feed intake and weight gain than control calves after 6 wk of age. Total ruminal volatile fatty acid concentrations were higher, but the acetate:propionate ratio was lower in lasalocid-fed calves than in control calves. Total viable anaerobic and amylolytic bacterial counts were higher in lasalocid-fed calves than in control calves. No significant treatment effect was found for ruminal NH3-N concentration or ruminal lasalocid-resistant, lactobacilli, lactate-utilizing, cellulolytic or methanogenic bacterial numbers. No evidence of coccidiosis was detected in either group. In general, lasalocid-fed calves had greater feed intake, weight gain and ruminal microbial activity than the calves fed no lasalocid in the diet.

Animals↗
PubMed1989

Intake of direct cut or wilted grass silage as related to chewing behavior, ruminal characteristics and site and extent of digestion by heifers.

Six nonpregnant Friesian heifers (516 kg avg BW) with ruminal and duodenal cannulas were used to examine intake of direct cut (DC) or wilted (W) grass silage in relation to chewing behavior, ruminal characteristics and site and extent of digestion. Dry matter content of the silages was 20.3% and 40.3%, and feed intake averaged 1.88% and 2.17% of BW (P less than .01), respectively. Mean ruminal osmolality was 291 mosm/liter for the DC and 318 mosm/liter for the W silage (P less than .05), with extreme values exceeding 350 mosm/liter for the W silage at 1 h to 2 h postfeeding. There was a shift from eating to ruminating on W silage associated with a longer duration of the average rumination bolus cycle (P less than .01). Duration of chewing time per kilogram of DM intake was 103.5 min and 91.7 min (P less than .05) for the DC and W silages, respectively. Fecal mean particle length was 2.2 times greater (P less than .01), accompanied by higher spread coefficients (P less than .001), for the W silage. No differences occurred between silages in ruminal digestibility of OM and NDF. In the total digestive tract, apparent digestibilities of OM and NDF were depressed after wilting grass prior to ensiling (P less than .01), but the proportion of digestible OM apparently digested in the rumen was .74 for both silages.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1989

Effects of a salivary stimulant, slaframine, on ruminal fermentation, bacterial protein synthesis and digestion in frequently fed steers.

Slaframine (SF), a parasympathomimetic salivary stimulant, was administered i.m. (10, 15 or 20 micrograms SF/kg BW) to ruminally and abomasally fistulated steers at 12-h intervals for 18-d periods in a latin square-designed experiment. Steers were fed semicontinuously (12 times daily) a 40:60 roughage:concentrate diet at twice their net energy requirement for maintenance. Ruminal digestion coefficients for DM, ADF and starch were 10 to 16% lower and linearly related in an inverse manner to the level of SF administered (P less than .05). Postruminal digestion of DM, ADF and starch increased as much as 46.7, 9.5 and 44.0%, respectively, in a fashion linearly related (P less than .05) to the level of SF administered. Total tract digestion of DM and ADF were not affected by SF; however, total tract starch digestion was increased as much as 5% and was related linearly (P less than .05) to SF treatment. With SF administration, as much as 13% more bacterial protein exited the rumen, resulting in a 16.5% linear improvement (P less than .1) in the efficiency of ruminal bacterial protein production per 100 g of OM fermented. Ruminal concentrations of VFA, ammonia and pH were not affected by SF. These results demonstrate a positive relationship between salivation and ruminal bacterial protein synthesis and suggest that feed utilization by ruminants may be improved by pharmacological stimulation of salivary secretions.

Abomasum↗
PubMed2001

Ruminal degradability, intestinal disappearance, and plasma methionine response of rumen-protected methionine in dairy cows.

Bioavailability of Met from a rumen-protected Met product was evaluated in two experiments using three ruminally and duodenally cannulated lactating (experiment 1) and nonlactating (experiment 2) dairy cows. In the first experiment, the ruminal in situ and mobile bag technique was used to assess ruminal degradability and intestinal disappearance of Met from the protected Met product. Effective ruminal degradability of Met at a ruminal outflow rate of 0.11/h was 21.7%. Combining effective ruminal degradability with intestinal digestibility yielded an estimate of Met availability of 25%. In the second experiment, designed as a 3 x 3 Latin square, Met availability was assessed by determining the response of plasma Met to supplementation of the protected Met product relative to that of duodenally administered Met. The periods were 1 wk with cows fed a meal containing 0, 20, or 63 g of protected Met on d 1 and infused intraduodenally with 10.7 g of Met on d 4. Blood was collected at various times relative to the time of oral dosing and the commencement of the duodenal infusion. Plasma Met response measured as area under the curve increased linearly with increasing protected Met. The response of plasma Met increased by 33 and 65.5% of the control values for 20 and 63 g of protected Met, respectively. Intestinal bioavailability of Met in the protected Met product ranged from 22 to 34%.

Animals↗
PubMed2001

Intestinal disappearance and mesenteric and portal appearance of amino acids in dairy cows fed ruminally protected methionine.

An experiment was conducted to compare the rates of disappearance of amino acids (AA) from the small intestine and their net appearance in the blood draining only the small intestine (mesenteric-drained viscera) and the whole gastrointestinal tract (portal-drained viscera) of cows fed a silage-based diet supplemented or not with ruminally protected Met. Five lactating dairy cows (118+/-4 DIM) equipped with duodenal and ileal cannulae (n = 2) or a duodenal cannula only (n = 3), two of which were multicatheterized, were fed a TMR top dressed with 0 or 72 g of ruminally protected Met per day. The addition of ruminally protected Met to the diet increased the duodenal flux of Met leading to a higher apparent digestibility of Met in the small intestine. Sixty-six percent of Met from ruminally protected Met bypassed the rumen and 82% of that Met disappeared from the small intestine. Arterial plasma Met concentrations numerically increased with ruminally protected Met (45 vs. 18 microM), while total AA concentration decreased. Feeding ruminally protected Met resulted in higher concentrations of urea-N and glucose in arterial plasma. Milk production and milk composition were unaffected. The disappearance of essential AA across the small intestine was equivalent (101%) to their flux through the mesenteric-drained viscera while the portal:mesenteric-drained viscera flux ratio for each essential AA varied from 38% for Thr to 76% for Phe. The portal:mesenteric-drained viscera flux ratio for Met was 66%. These results confirm observations made with pigs and sheep.

Amino Acids↗
PubMed2002

Effect of concentrate level and feeding management on chewing activities, saliva production, and ruminal pH of lactating dairy cows.

Eight ruminally cannulated lactating Holstein cows were used in a double 4 x 4 Latin square to determine the effects of 1) proportion of barley silage [40, 50, and 60% of dry matter (DM)] in the diet, and 2) feeding a total mixed ration (TMR) compared with separate ingredients (SI) on chewing activities, saliva production, and ruminal pH. Although cows fed SI were offered a diet containing 50% silage, they actually consumed a diet containing 43% silage (DM basis). Dry matter intake and milk yield were similar for all diets (18.2 kg of DM/d and 27.2 kg/d, respectively). Cows fed the 40% silage TMR spent more time eating than cows fed SI (243 vs. 198 min/d), but rumination time was similar (546 min/d). Eating time was similar among the TMR diets, but rumination time increased from 498 to 516 and 584 min/d as silage in the TMR increased from 40 to 50, and then to 60%, respectively. The secretion of saliva per gram of feed was 4.43, 3.18, and 1.19 ml/g of DM with consumption of silage, TMR, and concentrate, respectively. Resting salivation rate was similar for all diets (101 ml/min). Regardless of the diet, cows secreted 239 +/- 17 L/d of saliva, and ruminal pH was below 5.8 for 10 h/d. Results indicated increased chewing time did not increase total daily saliva secretion because increased eating and ruminating saliva was associated with decreased resting saliva. Feeding SI increased the risk of acidosis, because cows ate a higher proportion of concentrate than intended.

Animal Feed↗
PubMed2002

Technical note--a comparison of methods used to measure eating and ruminating activity in confined dairy cattle.

Detailed knowledge of chewing and rumination activities is critical to fully understand the dietary factors affecting normal rumen function. An automatic system for the digital recording of the jaw movements in free-ranging grazing cattle has been described, but its ability to measure chewing activity of cattle housed in confinement and fed total mixed rations has not yet been evaluated. The eating and ruminating behaviors of eight lactating dairy cows were recorded simultaneously by a wireless automatic system and by 5-min interval observation over 24-h periods. Results indicated that both methods agreed on identification of eating and ruminating bouts. Mean differences between methods for total time eating (8.7 min +/- 12.8) and ruminating (42.9 min +/- 12.0) were significantly different. The time recorded by observation in both eating and rumination was 3.6 and 10.3% higher compared with the automatic system. Differences indicate inaccuracies in the observational method itself. The automatic system may prove useful in further studies examining eating and rumination activities in cattle.

Animals↗
PubMed2002

Corn silage management III: effects of hybrid, maturity, and processing on nitrogen metabolism and ruminal fermentation.

Two experiments were conducted to evaluate the effects of maturity and mechanical processing of two hybrids of whole plant corn silage on DM and OM digestibility, nitrogen metabolism, ruminal fermentation, and milk production and composition in lactating Holstein cows. In the first experiment, Pioneer hybrid 3845 whole plant corn was harvested at hard dough, one-third milkline, and two-thirds milkline with a theoretical length-of-cut of 6.4 mm. At each stage of maturity, corn was harvested with (1-mm roll clearance) and without (15.9-mm roll clearance) mechanical processing using a John Deere 5830 harvester with an on-board kernel processor. In the second experiment, Pioneer hybrids 3845 and Quanta were harvested at one-third milkline, two-thirds milkline, and blackline stages of maturity with and without mechanical processing. The theoretical length-of-cut was 12.7 mm. Total tract DM and OM digestibilities were lower for cows fed diets containing processed corn silage in experiment 1, and tended to be lower for cows fed diets containing unprocessed corn silage in experiment 2. Ruminal acetate concentrations were greater and ruminal propionate concentrations were lower 2 and 6 h after feeding for cows fed diets containing corn silage harvested at physiological maturity in experiment 2. This was due to decreased digestion of starch at advanced maturities in experiment 2. Ruminal pH tended to decline rapidly after feeding for cows fed hybrid Quanta (2 h) compared to hybrid 3845 (5 h) corn silage based diets. Ruminal acetate concentrations decreased and ruminal propionate concentrations increased 2 and 6 h after feeding for cows fed diets containing hybrid Quanta corn silage compared to hybrid 3845 corn silage. This was related to a greater starch concentration in the corn silage, greater starch intake, and increased rate of starch digestion for cows fed hybrid Quanta corn silage-based diets. Microbial nitrogen flow was lower and feed nitrogen flow was greater for cows fed diets containing hybrid Quanta corn silage. The lower microbial nitrogen flow was due to lower microbial nitrogen concentration and nonammonia nitrogen flow to the duodenum. Milk fat and protein concentrations had a strong quadratic relationship with forage NDF intake as a percentage of body weight. When forage NDF intake as a percentage of body weight dropped below 0.70%, there was a rapid decline in milk fat and protein concentrations.

Animals↗
PubMed2002

Relationship between corn vitreousness and ruminal in situ starch degradability.

The objective of this experiment was to determine the relationship between corn kernel vitreousness and ruminal in situ starch degradation. Fourteen U.S. and five Brazilian corn hybrids cultivated in their respective countries were evaluated. The U.S. dent hybrids were harvested at one-half milk line, black layer, and 21 d after black layer stages of maturity. Brazilian flint hybrids were harvested only at the latest stage of maturity. Vitreousness was determined by manual dissection of the kernels. Ruminal in situ degradation of starch was determined in three lactating Holstein cows fitted with ruminal cannulae. Vitreousness of the five mature Brazilian hybrids averaged 73.1% (range of 64.2% to 80.0%), while vitreousness of the 14 mature U.S. hybrids averaged 48.2% (range of 34.9% to 62.3%). Within the 14 U.S. hybrids, average vitreousness increased from 42.8% to 48.2% as stage of maturity progressed from one-half milk line to 21 d after black layer. The correlation between kernel density and vitreousness was 0.87. The correlations between kernel vitreousness or density and ruminal starch availability were -0.93 and -0.87, respectively. With advancing maturity, kernel vitreousness and density increased while ruminal starch availability decreased. Kernel vitreousness and density may be useful parameters for which to select corn hybrids for high ruminal starch availability. Density may be a more practical measurement than vitreousness for screening large corn data sets.

Animal Feed↗
PubMed2002

Effects of a monensin controlled-release capsule or premix on attenuation of subacute ruminal acidosis in dairy cows.

The effects of monensin, administered either as a controlled release capsule (CRC) or a premix, on attenuating grain-induced subacute ruminal acidosis (SARA) and on ruminal fermentation characteristics in Holstein cows receiving a total mixed ration were investigated in two experiments. In both experiments, six multiparous, rumen-fistulated Holstein cows were used in a two-treatment, two-period crossover design with 6-wk periods. In Experiment 1, treatments were either a monensin CRC or a placebo CRC. In Experiment 2, treatments were either a monensin premix or a placebo premix. In both experiments, at the beginning of wk 4 SARA was induced in experimental cows for a 10-d period with a grain challenge model, and ruminal pH was measured continuously using indwelling pH probes. The administration of monensin either as a CRC or a premix had no effect on ruminal pH characteristics. Neither monensin CRC nor premix had an effect on ruminal volatile fatty acid concentrations, but reduced the acetate:propionate ratio. Monensin premix-treated cows were observed to have increased milk yield, largely as a result of a higher dry matter intake in monensin-treated cows compared to control cows. Milk fat content and yield were lower in monensin-treated cows compared to placebo-treated cows during SARA. In conclusion, there is no evidence that monensin was efficacious in raising ruminal pH during SARA under the conditions employed in this study.

Acidosis↗
PubMed2003

Effects of corn grain conservation method on ruminal digestion kinetics for lactating dairy cows at two dietary starch concentrations.

Effects of conservation method of corn grain and dietary starch concentration on ruminal digestion kinetics were evaluated. Eight ruminally and duodenally cannulated Holstein cows (55 +/- 15.9 days in milk; mean +/- SD) were used in a duplicated 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. Experimental diets contained either ground high moisture corn (HM) or dry ground corn (DG) at two dietary starch concentrations (32 vs. 21%). Mean particle size and dry-matter concentration of corn grain were 1,863 microm and 63.2%, and 885 microm and 89.7%, for HM and DG, respectively. Starch digestibility in the rumen was greater for HM treatments compared with DG treatments, but starch digestibility in the total tract was not affected by conservation method of corn grain because of compensatory digestion in the intestines. The difference in ruminal starch digestibility between HM and DG treatment was greater for high-starch diets (71.1 vs. 46.9%) compared with low-starch diets (58.5 vs. 45.9%). This interaction is attributed to a greater difference in first-order digestion rate of starch between HM and DG treatment in high-starch diets (28.2 vs. 14.6%/h) compared with low-starch diets (16.8 vs. 12.2%/h). This suggests that ruminal starch digestion is a second-order reaction limited by enzyme activities as well as substrate availability; ruminal contents of cows fed low-starch diets may have insufficient amylolytic activity for maximal starch digestion when readily fermentable starch is available. Rate of neutral detergent fiber digestion in the rumen was slower for high-starch diets and HM treatments compared with low-starch diets and DG treatments, respectively. Effects of corn grain conservation method on ruminal digestion kinetics are greatly altered by starch concentration of diets.

Amylases↗
PubMed2003

Fibrolytic enzymes and parity effects on feeding behavior, salivation, and ruminal pH of lactating dairy cows.

Four multiparous and four primiparous lactating dairy cows fitted with ruminal cannulas were used in a duplicated 4 x 4 Latin square design to study the effects of parity and inclusion of a fibrolytic enzyme product (Agribrands International, St. Louis, MO) on feeding and chewing behavior, salivation, and ruminal pH. Diets consisting of rolled barley, barley silage, and alfalfa haylage (55% forage, DM basis) differed in enzyme application: 1) control, 2) enzyme applied to concentrate (45% of TMR), 3) enzyme applied to supplement (4% of TMR), and enzyme applied to a premix (0.2% of TMR). Enzyme supplementation did not alter daily time spent eating or ruminating, but when enzymes were added to the ration daily, saliva production increased, with no difference among enzyme application treatments. Multiparous cows consumed a greater amount of feed, but spent a similar amount of time eating, compared to primiparous cows. Primiparous cows had shorter ruminating episodes, resulting in lower daily ruminating time compared with multiparous cows. Primiparous cows had lower daily saliva output compared with multiparous cows. These results indicate that application of this fibrolytic enzyme product did not alter the physical structure of the feed, as measured by feeding and chewing variables. The increase in total saliva production observed in cows fed enzyme-supplemented diets may be attributed to a physiological response to compensate for the increase in fermentation products during digestion. The increased intake for multiparous cows is attributed to increased eating rate and not to increased time spent eating. The higher DMI of multiparous cows resulted in increased rumination time needed to process the additional feed and increased salivation to buffer the greater production of VFA.

Animals↗
PubMed2003

Pelleted beet pulp substituted for high-moisture corn: 2. Effects on digestion and ruminal digestion kinetics in lactating dairy cows.

The effects of increasing concentrations of dried, pelleted beet pulp substituted for high-moisture corn on digestion and ruminal digestion kinetics were evaluated using eight ruminally and duodenally cannulated multiparous Holstein cows in a duplicated 4 x 4 Latin square design with 21-d periods. Cows were 79 +/- 17 (mean +/- SD) d in milk at the beginning of the experiment. Experimental diets with 40% forage (corn silage and alfalfa silage) and 60% concentrate contained 0, 6.1, 12.1, or 24.3% beet pulp substituted for high-moisture corn on a dry matter basis. Diet concentrations of neutral detergent fiber (NDF) and starch were 24.3 and 34.6% (0% beet pulp), 26.2 and 30.5% (6% beet pulp), 28.0 and 26.5% (12% beet pulp), and 31.6 and 18.4% (24% beet pulp), respectively. Ruminal dry matter pool decreased and NDF turnover rate increased as dietary beet pulp content increased. Potentially digestible NDF was digested more extensively and at a faster rate in the rumen with increasing beet pulp, resulting in increased total tract NDF digestibility. Passage rates of potentially digestible NDF and of indigestible NDF were not affected by treatment. True ruminal digestibility of starch decreased with increasing beet pulp substitution. This was caused by a linear increase in starch passage rate, possibly because of increasing ruminal fill, and a linear decrease in digestion rate of starch in the rumen, possibly because of reduced amylolytic enzyme activity for lower-starch diets. Although true ruminal starch digestibility decreased when more beet pulp was fed, whole tract starch digestibility was not affected because of compensatory digestion of starch in the intestines. Due to more thorough digestion of fiber in diets containing more beet pulp, whole-tract digestibility of organic matter increased linearly, and intake of digestible organic matter was not affected. Partially replacing high-moisture corn with beet pulp in low-forage diets increased fiber digestibility without reducing whole-tract starch digestibility.

Animal Feed↗
PubMed2003

Ruminal fermentation and bacterial protein synthesis of whole cottonseed coated with combinations of gelatinized corn starch and urea.

Four ruminally and duodenally cannulated Jersey cows were used in a 4 x 5 incomplete Latin square study to determine the effects of including urea in the gelatinized corn starch coating applied to whole cottonseed (WCS) on ruminal fermentation, fiber digestion, and bacterial protein synthesis. Treatments included uncoated WCS (control) and four coated WCS treatments. The coatings provided two concentrations each of gelatinized corn starch (2.5 [2S] or 5% [5S]) and feed grade urea (0.25 [2U] or 0.5% [5U]). Treated WCS comprised 15% of the ration dry matter that was fed as a total mixed ration once daily. Ruminal pH and molar proportions of isobutyrate was higher and NH3-N concentrations lower for control compared with coated WCS. Molar proportions of propionate tended to be higher and valerate was lower with 2S compared with 5S. Molar proportions of acetate tended to be lower, whereas butyrate was higher for 5U than 2U. Nutrient intake was lower for WCS coated with 5S5U compared with 2S5U. Ruminal NDF digestibility of NDF tended to be higher with 5U compared with 2U, but no differences were observed in ruminal or total tract apparent digestibility of nutrients. No differences were observed in the flow of total N or bacterial N to the duodenum, but the flow of nonbacterial N tended to be higher for WCS coated with 5U. Coating WCS appears to slightly alter ruminal metabolism while providing similar amounts of N flowing to the duodenum without altering fiber digestion.

Animal Feed↗
PubMed2003

The effect of steam-flaked or dry ground corn and supplemental phytic acid on phosphorus partitioning and ruminal phytase activity in lactating cows.

The effect of starch source and phytic acid (PA) supplementation on phosphorus (P) partitioning and ruminal phytase activity was evaluated in eight midlactation cows (four ruminally cannulated). Cows were randomly assigned to treatments in replicated 4 x 4 Latin squares with four 18-d periods. Diets included dry ground corn (DG) or steam-flaked corn (SF), with no supplemental P (L; 0.33% P) or supplemental purified PA (0.44% P) to provide additional P from a nonmineral source. Total collection of milk, urine, and feces was conducted on d 16 to 18 of each period. Ruminal fluid was sampled and ruminal pH measured every 8 h on d 17 and 18. Milk yield was unaffected by starch source, despite lower DMI by cows fed SF. Cows fed SF had increased DM digestibility compared with those fed DG, and tended to have higher efficiency of milk yield (1.40 vs. 1.35 kg of milk/kg of DMI). Intake and fecal excretion of P was lower in cows fed SF than in cows fed DG. In cows fed SF, milk P as a percentage of P intake increased compared with cows fed DG. Ruminal pH was unaffected by diet, but milk fat content was lower for cows fed SF. Milk yield, DMI, and feed to milk ratio were not affected by supplementation with PA. Although cows fed PA had increased P intake compared with cows fed low P diet, increased P excretion resulted in no differences in apparent P digestibility. Phosphorus balance tended to be higher in cows fed PA, but milk P as a percentage of intake was reduced. The interaction of starch source and PA affected ruminal phytase activity. Altering starch source to improve efficiency of milk yield in lactating dairy cows may help reduce P losses from dairy farms.

6-Phytase↗
PubMed2006

Augmentation of vaccenate production and suppression of vaccenate biohydrogenation in cultures of mixed ruminal microbes.

To increase ruminal outflow of trans-vaccenic acid (t-VA), a new strain of Butyrivibrio fibrisolvens (MDT-10) was isolated that has a great ability to hydrogenate linoleic acid (LA) to t-VA. When strain MDT-10 was added to the batch cultures of mixed ruminal microbes (1% of the total number of viable ruminal bacteria), LA conversion to t-VA increased greatly; after 3 h, t-VA levels were > 4-fold higher than the control. By 10 h, all of the t-VA was hydrogenated to stearic acid. However, when a new strain of Bifidobacterium adolescentis (HF-11), which has a high capacity for incorporation of t-VA, was added in conjunction with MDT-10 (1% of the total number of ruminal bacteria), t-VA levels after 10 h were 6 times higher than with MDT-10 alone. These results suggest that t-VA produced by MDT-10 was incorporated into HF-11 cells, resulting in protection of t-VA from t-VA-hydrogenating microbes. Similar results were obtained in a continuous culture of mixed ruminal microbes in which addition of HF-11 simultaneously with MDT-10 increased the amount of t-VA in the effluent 2.5-fold. Both MDT-10 and HF-11 appeared to grow readily in the presence of mixed ruminal microbes. Sixty-two percent of t-VA incorporated by HF-11 was present in the free form, whereas 19, 15, and 3%, respectively, were incorporated into monoacylglycerol, glycerophospholipid, and diacylglycerol fractions. Because these lipids can be digested in the small intestine, it is likely that most t-VA in HF-11 cells is absorbed. Thus, introduction of MDT-10 and HF-11 simultaneously to the rumen might increase the amount of t-VA absorbed and might consequently increase the conversion of t-VA to conjugated linoleic acid in tissue.

Animals↗
PubMed2006

Effects of rumen acid load from feed and forage particle size on ruminal pH and dry matter intake in the lactating dairy cow.

The objective of this study was to evaluate the effects of level of concentrate acidogenic value (AV) and forage particle size on ruminal pH and feed intake in lactating dairy cows. Two isoenergetic (net energy for lactation = 1.5 +/- 0.01 Mcal/kg) and isonitrogenous (crude protein = 17.4 +/- 0.1% dry matter) concentrates with either a low AV or high AV were formulated and fed in a total mixed ration with either coarsely or finely chopped corn silage and alfalfa haylage ad libitum. Four rumen-fistulated cows (114 +/- 14 d in milk) were randomly assigned to 1 of the 4 treatments in a 4 x 4 Latin square with a 2 x 2 factorial treatment arrangement. Each period consisted of 3-wk (14-d treatment adaptation and 7-d data collection). Increasing the concentrate AV decreased the mean pH (from 6.07 to 5.97) and minimum pH (from 5.49 to 5.34). Cows fed high-AV diets spent a longer time below pH 5.6 (135.1 vs. 236.7 min/d; low-AV diet vs. high-AV diet, respectively) and pH 5.8 (290.0 vs. 480.6 min/d; low-AV diet vs. high-AV diet, respectively) than cows fed low-AV diets. Increasing forage particle size had no effect on the mean and minimum ruminal pH. There was an interaction between concentrate AV and forage particle size on maximum ruminal pH. Increasing forage particle size increased the maximum pH for cows fed the high-AV concentrate (6.69 vs. 6.72; low-AV diet vs. high-AV diet, respectively) and had no effect on the maximum pH for cows fed the low-AV concentrate (6.98 vs. 6.76; low-AV diet vs. high-AV diet, respectively). Increasing the concentrate AV did not affect dry matter intake but reduced neutral detergent fiber intake from 9.7 to 8.8 kg/d. Milk fat content was negatively correlated with time and area below pH 5.6 (time below, r = -0.51; area below, r = -0.56) and pH 5.8 (time below, r = -0.42; area below, r = -0.54). These results suggest that coarse forage particle size can attenuate drops in ruminal pH. However, the ameliorating effects of forage particle size on drops in ruminal pH were more apparent for high-AV diets than for low-AV diets. The AV approach combined with physically effective neutral detergent fiber would therefore improve the formulation of diets and help to mitigate subacute ruminal acidosis in dairy cows.

Animal Feed↗
PubMed1988

Efficacy of simulated, slow release sodium bicarbonate in stabilizing ruminal milieu and acid-base status in lactating dairy cattle.

Four primiparous, ruminally fistulated, lactating Holstein cows were assigned to a 4 X 4 Latin square to study the effects of NaHCO3 infusion time on ruminal milieu and systemic acid-base balance. Sodium bicarbonate, approximating .8% of diet DM, was mixed with water and infused into the rumen for 1, 2, 4, or 6 h postfeeding to simulate different timed-release rates of NaHCO3. All cows received a corn silage and concentrate diet mixed at a 40:60 ratio on a DM basis and fed in amounts that were consumed within 1 h. Ruminal fluid, blood, and urine samples were collected at 0, 1, 2, 3, 4, 5, 6, 8, and 10 h postfeeding. Length of infusion time did not alter ruminal, blood, or urine pH, but all three variables were affected by sampling time, with the 5, 1, and 3-h sampling intervals yielding the lowest values for the three measurements, respectively. Ruminal VFA molar percentages of acetate, propionate, butyrate, isovalerate, and valerate were not influenced by infusion interval but were all different due to time of sampling. Blood pCO2 and HCO3 were affected by sampling time but not by infusion interval. With the exception of blood HCO3, all treatment X sampling time interactions were nonsignificant. It appears that timed release of NaHCO3 does not alter ruminal function or acid-base balance.

Acid-Base Equilibrium↗