Biomedical subjects

K A Beauchemin

Publications and source records attributed to K A Beauchemin.

At least 37 records · Page 2Linked to original sources

PubMed2004

Effects of mechanical processing on the nutritive value of barley silage for lactating dairy cows.

Mechanical processing of whole crop barley before ensiling may be useful for improving nutrient use by dairy cattle. The objective of this study was to assess the effects of feeding mechanically processed barley silage as the main forage source on lactational performance. Twenty-four Holstein cows, 16 primiparous (187 +/- 52 days in milk) and 8 multiparous (87 +/- 69 days in milk) cows, were used in a completely randomized design with a 2-wk covariate period and a 6-wk treatment period. The 2 treatments were: 1) total mixed ration (TMR) containing regular barley silage (RBS-TMR), and 2) TMR containing mechanically processed barley silage (MPBS-TMR). Barley silage and alfalfa hay supplied 41 and 5% of the dietary dry matter (DM), respectively. Intake, body weight, and milk production were measured during the covariate and treatment periods. In addition, 2 multiparous cows were used for in situ measurements of the ruminal DM and fiber degradation kinetics of the barley silages and TMR. Data were analyzed with repeated measurements using a mixed model that included the covariate adjustment. Feeding MPBS-TMR had no significant effects on DM intake (DMI; 21.7 kg/d), milk yield (33.9 kg/d), or milk composition, with only 4% FCM (fat-corrected milk) yield (29.7 vs. 31.7 kg/d) and milk fat concentration (3.30 vs. 3.57%) showing a numerical improvement. Apparent digestibilities of DM and nutrients were not affected by feeding MPBS-TMR, with the exception of starch digestibility, which tended to increase. Dairy efficiencies calculated as milk yield/DMI or FCM/DMI were not different between treatments. Body weight and body condition score were not affected by treatments. Effective ruminal degradability of DM was similar for both barley silages, indicating that when the silages were ground to remove the effects of mechanical processing, the potential digestion was similar. Mechanical processing of barley silage harvested at a mid-dough stage of maturity resulted in small improvements in its nutritive value for lactating dairy cows and had minor impact on digestibility and milk production.

Animal Feed↗

PubMed2003

Effects of enzyme supplementation of a total mixed ration on microbial fermentation in continuous culture, maintained at high and low pH.

A dual-flow continuous culture system was used to investigate the effects of pH and addition of an enzyme mixture to a total mixed ration (TMR) on fermentation, nutrient digestion, and microbial protein synthesis. A 4 x 4 Latin square design with a factorial arrangement of treatments was used, with four 9-d periods consisting of 6 d for adaptation and 3 d for measurements. Treatments were as follows: 1) high pH with control TMR, 2) high pH with TMR treated with enzyme, 3) low pH with control TMR, and 4) low pH with TMR treated with enzyme. Ranges of pH were 6.0 to 6.6 and 5.4 to 6.0 for high and low, respectively. Fermenters were fed twice daily a TMR consisting of 30% alfalfa hay, 30% corn silage, and 40% rolled corn (DM basis). The silage was milled fresh and the TMR was fed to the fermenters in fresh form (64% DM). The enzyme mixture was a commercial product of almost exclusive protease activity; it was applied daily to the fresh TMR and stored at 4 degrees C for at least 12 h before feeding. Degradability of OM, NDF, ADF, and cellulose was decreased (P < 0.05) by low pH. Hemicellulose and protein degradation were not affected by pH. Enzyme addition increased (P < 0.01) NDF degradability (by 43% and 25% at high and low pH, respectively), largely as a result of an increase in hemicellulose degradation (by 79% and 51% at high and low pH, respectively). This improvement was supported by an increase (P < 0.05) in the xylanase and cellulase activities in the liquid phase of the fermenter contents. Total VFA were decreased (P < 0.05) by low pH, but were not affected by enzyme addition. Total bacterial numbers were increased (P < 0.03) at low pH and tended (P < 0.13) to increase with enzyme addition. Cellulolytic bacteria in effluent fluid were decreased (P < 0.02) at low pH but were unaffected by enzyme addition. Despite a large increase (P < 0.001) in protease activity, protein degradation was only numerically increased by enzyme addition. Microbial protein synthesis was higher (P < 0.10) at high pH but was not affected by enzyme addition. Methane production, expressed as a proportion of total gases, was decreased (P < 0.001) at low pH but was not affected by enzyme addition. It is concluded that it is possible to adapt the continuous culture system to use fresh feeds instead of dried feeds. Overall, the results indicate that the enzyme product used in this study has a potential to increase fiber degradability without increasing methane production.

Animal Feed↗

PubMed2003

Screening of exogenous enzymes for ruminant diets: relationship between biochemical characteristics and in vitro ruminal degradation.

With the objective of developing a rational approach for the selection of feed enzymes for ruminants, 22 commercial enzyme products were examined in terms of protein concentration, enzymic activities on model substrates, and hydrolytic capacity, the latter determined from the release of reducing sugars from alfalfa hay and corn silage. An in vitro ruminal degradation assessment was carried out using the same substrates, untreated or treated with the 22 enzyme products at 1.5 microL/g forage DM. Stepwise regressions were then performed to establish relationships between these factors. Protein concentration and enzymic activities explained at least 84% (P < 0.01) of the variation in the release of reducing sugars from alfalfa and corn silage. Alfalfa DM degradation after incubation with ruminal fluid for 18 h was positively related to xylanase activity (R2 = 0.29, P < 0.01), but the same activity was negatively related to DM degradation of corn silage (R2 = 0.19, P < 0.05). Protease activity explained a further 10% of the alfalfa DM degradation (P < 0.10). Following sequential steps involving the determination of rate and extent of DM and fiber degradation, the best candidates for alfalfa and corn silage were selected. Enzyme products effective with alfalfa hay seemed to exert part of their effect during the pretreatment period, whereas enzymes effective with corn silage worked exclusively after ruminal fluid was added. This finding suggests that different modes of action of exogenous enzymes are attacking different substrates and may partly explain enzyme-feed specificity. In alfalfa, it seems that effective enzymes work by removing structural barriers that retard the microbial colonization of digestible fractions, increasing the rate of degradation. In corn silage, effective enzymes seem to interact with ruminal enzymes to degrade the forage more rapidly, which is consistent with previous findings of synergism between exogenous and ruminal enzymes.

Animal Feed↗

PubMed2003

Influence of fibrolytic enzymes on the hydrolysis and fermentation of pure cellulose and xylan by mixed ruminal microorganisms in vitro.

A series of in vitro studies was conducted to determine the effects of adding a commercial enzyme product on the hydrolysis and fermentation of cellulose, xylan, and a mixture (1:1 wt/wt) of both. The enzyme product (Liquicell 2500, Specialty Enzymes and Biochemicals, Fresno, CA) was derived from Trichoderma reesei and contained mainly xylanase and cellulase activities. Addition of enzyme (0.5, 2.55 and 5.1 microL/g of DM) in the absence of ruminal fluid increased (P < 0.001) the release of reducing sugars from xylan and the mixture after 20 h of incubation at 20 degrees C. Incubations with ruminal fluid showed that enzyme (0.5 and 2.55 microL/g of DM) increased (P < 0.05) the initial (up to 6 h) xylanase, endoglucanase, and beta-D-glucosidase activities in the liquid fraction by an average of 85%. Xylanase and endoglucanase activities in the solid fraction also were increased (P < 0.05) by enzyme addition, indicating an increase in fibrolytic activity due to ruminal microbes. Gas production over 96 h of incubation was determined using a gas pressure measurement technique. Incremental levels of enzyme increased (P < 0.05) the rate of gas production of all substrates, suggesting that fermentation of cellulose and xylan was enzyme-limited. However, adding the enzyme at levels higher than 2.55 microL/g of DM failed to further increase the rate of gas production, indicating that the maximal level of stimulation was already achieved at lower enzyme concentrations. It was concluded that enzymes enhanced the fermentation of cellulose and xylan by a combination of pre- and postincubation effects (i.e., an increase in the release of reducing sugars during the pretreatment phase and an increase in the hydrolytic activity of the liquid and solid fractions of the ruminal fluid), which was reflected in a higher rate of fermentation.

Animal Feed↗

PubMed2003

Effect of grain processing and silage on microbial protein synthesis and nutrient digestibility in beef cattle fed barley-based diets.

Effects of the extent of grain processing and the percentage of silage in barley-based feedlot diets on microbial protein synthesis and nutrient digestibility were evaluated using four steers (initial BW of 442 +/- 15 kg) with ruminal and duodenal cannulas. The experiment was a 4 x 4 Latin square with four periods of 21 d each. Dietary treatments were arranged as a 2 x 2 factorial with two levels of barley silage (20 and 5% DM basis) and two degrees of barley grain processing (coarsely and flatly steamrolled to a processing index [PI] of 86 and 61%, respectively). The PI was quantified as the volume weight of the barley grain after processing, expressed as a percentage of the volume weight prior to processing. Digest a flow (Yb) and microbial (15N) markers were continuously infused into the rumen for a period of 13 d. Ruminal, duodenal, and fecal samples were collected at various times over the last 6 d of marker infusion. Diurnal ruminal pH was measured for 48 h. Intake of DM averaged 1.8% of BW, and was not different among the dietary treatments (P > 0.10). Ruminal starch digestibility was higher (P < 0.05) for the more extensively processed grain and tended (P < 0.10) to be highest when the more extensively processed grain was combined with 5% barley silage. In contrast, ruminal fiber digestibility for the 5% silage diets was reduced (P < 0.05) when the grain was more extensively processed. There was, however, no effect of grain processing on ruminal OM digestibility (P > 0.10), and hence, no inhibitory effect on microbial N flow to the intestine (P > 0.10). There was also no effect of the level of silage on microbial N flow (P > 0.10), but there was a tendency for improved efficiency of microbial protein synthesis for the 20% silage diets (P = 0.072). Ruminal escape of nonmicrobial N (P = 0.003) was greater, and thus, protein flow to the intestine was greater for the 5% silage diets. Diurnal ruminal pH was lower (P < 0.05) for 11 of the 24 hourly time points in steers fed the 5% silage diets than those fed the 20% silage diets. In conclusion, barley grain rolled to a PI of 86 to 61% and combined with 20 and 5% barley silage had little effect on microbial protein supply. Microbial protein supply was not inhibited when the barley grain was extensively processed (PI of 61%) and the silage was limited to only 5% of the diet DM, but feed intake of steers in this study was lower than would be expected in the feedlot.

Animal Feed↗

PubMed2003

Effects of bacterial direct-fed microbials and yeast on site and extent of digestion, blood chemistry, and subclinical ruminal acidosis in feedlot cattle.

Two studies were conducted to determine whether a bacterial direct-fed microbial (DFM) alone or with yeast could minimize the risk of acidosis and improve feed utilization in feedlot cattle receiving high-concentrate diets. Eight ruminally cannulated steers, previously adapted to a high-concentrate diet, were used in crossover designs to study the effects of DFM on feed intake, ruminal pH, ruminal fermentation, blood characteristics, site and extent of digestion, and microbial protein synthesis. Steers were provided ad libitum access to a diet containing steam-rolled barley, barley silage, and a protein-mineral supplement (87, 8, and 5% on a DM basis, respectively). In Exp. 1, treatments were control vs. the lactic-acid producing bacterium Enterococcus faecium EF212 (EF; 6 x 10(9) cfu/d). In Exp. 2, treatments were control vs EF (6 x 10(9) cfu/d) and yeast (Saccharomyces cerevisiae; 6 x 10(9) cfu/d). Supplementing feedlot cattle diets with EF in Exp. 1 increased (P < 0.05) propionate and (P < 0.05) decreased butyrate concentrations, decreased the nadir of ruminal pH (P < 0.05), enhanced the flow of feed N (P < 0.10) to the duodenum but reduced that of microbial N (P < 0.10), reduced (P < 0.10) intestinal digestion of NDF, and increased (P < 0.10) fecal coliform numbers. Other than the increase in propionate concentrations that signify an increase in energy precursors for growth, the other metabolic changes were generally considered to be undesirable. In Exp. 2, providing EF together with yeast abolished most of these undesirable effects. Combining EF with yeast increased the DM digestion of corn grain incubated in sacco, but there were no effects on altering the site or extent of nutrient digestion. The diets used in this study were highly fermentable, and the incidence of subclinical ruminal acidosis, defined as steers with ruminal pH below 5.5 for prolonged periods of time, was high. Supplementing the diet with EF, with or without yeast, had limited effects on reducing ruminal acidosis. It seems that cattle adapted to high-grain diets are able to maintain relatively high feed intake and high fiber digestion despite low ruminal pH. The Enterococcus faecium bacterium and yeast used in this study were of limited value for feedlot cattle already adapted to high-grain diets.

Acidosis↗

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

Effects of particle size of alfalfa-based dairy cow diets on chewing activity, ruminal fermentation, and milk production.

Effects offorage particle size measured as physically effective NDF and ratio of alfalfa silage to alfalfa hay of diets on feed intake, chewing activity, particle size reduction, salivary secretion, ruminal fermentation, and milk production of dairy cows were evaluated using a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. The diets consisted of 60% barley-based concentrate and 40% forage, comprised either of 50:50 or 25:75 of alfalfa silage:alfalfa hay, and alfalfa hay was either chopped or ground. Various methods were used to determine physically effective NDF content of the diets. Cows surgically fitted with ruminal and duodenal cannulas were offered ad libitum access to these total mixed diets. The physically effective NDF content of the diets was significantly lower when measured using the Penn State Particle Separator than when measured based on particles retained on 1.18-mm screen. Intake of DM was increased by increasing the ratio of silage to hay but was not affected by physically effective NDF content of diets. Eating time (hours per day) was not affected by the physically effective NDF content of diets, although cows spent more time eating per unit of DM or NDF when consuming high versus low alfalfa hay diets. Ruminating time (hours per day) was increased with increased physically effective NDF content of the diets. Rumen pH was affected more by changing dietary particle size than altering the ratio of silage to hay. Feeding chopped hay instead of ground hay improved ruminal pH status: time during which ruminal pH was above 6.2 increased and time during which ruminal pH was below 5.8 decreased. Milk production was increased by feeding higher concentrations of alfalfa silage due to increased DM intake, but was not affected by dietary particle size. Feed particle size, expressed as mean particle length or physically effective NDF was moderately correlated with ruminating time but not with eating time. Although physically effective NDF and chewing time were not correlated to mean rumen pH, they were negatively correlated to the area between the curve and pH 5.8, indicating a positive effect on reducing the risk of acidosis. Milk fat content was correlated to rumen pH but not to physically effective NDF or chewing activity. These results indicate that increasing physically effective NDF content of the diets increased chewing activity and improved rumen pH status but had limited effect on milk production and milk fat content.

Animal Nutritional Physiological Phenomena↗

PubMed2003

Effects of increasing levels of refined cornstarch in the diet of lactating dairy cows on performance and ruminal pH.

Our study investigated the effect of a linear increase in level of ruminally fermentable carbohydrate, at a constant level of dietary starch and fiber, on performance, microbial N yield, chewing activity, and ruminal pH of midlactation dairy cows. Eight cows (53 DIM) were assigned to four treatments in a double 4 x 4 Latin square. Diets consisted of increasing levels of refined cornstarch (0, 5.9, 11.9, and 17.9% of diet dry matter) replacing dry cracked, shelled corn so that increasing amounts of dietary starch originated from refined cornstarch. Corn gluten feed was used to balance diets for similar NDF content. The four diets averaged 17.9% CP, 27.2% NDF, 18.7% ADF, and 31.1% starch (dry matter basis). Diets were fed for ad libitum intake and had a forage to concentrate ratio of 40:60. Forage was coarsely chopped (13.7 mm mean particle size) alfalfa silage. Daily dry matter intake averaged 26.0 kg and tended (P = 0.08) to increase quadratically with increasing level of refined cornstarch. Milk production averaged 38.9 kg/d and milk fat percentage tended (P = 0.08) to decrease linearly, whereas percentage of protein increased quadratically, with increasing level of refined cornstarch. Yield of components and energy corrected milk was similar across diets. Total tract digestibility of starch increased linearly from 85.1% to 92.4% with increasing level of refined cornstarch. Microbial yield was unaffected by diet and averaged 371.1 g N/d. Time spent eating decreased linearly from 329 to 308 min/d when level of refined cornstarch was increased, but rumination time was unaffected. Ruminal concentration and proportion of acetate decreased linearly while concentration and proportion of propionate increased linearly with increasing level of refined cornstarch. Mean ruminal pH, time spent below pH 5.8 (h), and area below pH 5.8 (h x pH units/d) were unaffected by level of refined cornstarch and averaged 5.97, 8.4, and 2.9, respectively. Increasing the level of carbohydrates fermented in the rumen by replacing dry cracked corn with refined cornstarch (up to 57% of dietary starch) did not compromise rumen fermentation or affect performance of midlactation dairy cows.

Animals↗

PubMed2003

Measuring the feeding behavior of lactating dairy cows in early to peak lactation.

The objectives of this study were to: 1) objectively define meal criteria (minimum interval between meals) of free-stall housed cows fed via a feed alley, 2) determine which measures of feeding behavior were most repeatable, and 3) describe changes in the feeding behavior from early to peak lactation. An electronic monitoring system was used to record individual cow presence (hits; 6-s resolution) at the feed alley for 21 lactating cows for three 8-d periods: period 1, 35 +/- 16 (mean +/- SD), period 2, 57 +/- 16, and period 3, 94 +/- 16 DIM. A mixture distribution model was used to calculate the meal criterion (27.74 min) by fitting the log10 frequency distribution of the intervals between hits. The within-cow repeatability was highest for feeding activity (hits d(-1)) and intensity (hits per meal min), moderate for total daily mealtime (min d(-1)) and meal duration (min meal(-1)), and lowest for meal frequency (meals d(-1)). From periods 1 to 2, all cows showed increases in total daily mealtime, meal frequency, and meal duration; however, cows with lower meal frequencies and feeding intensity in period 1 showed the greatest increases. Cows with high feeding activity and intensity during period 2 showed proportionally greater increases during period 3. These results illustrate that some measures of feeding behavior are highly repeatable within cows, but variable between cows and across stages of lactation. Thus, tests of treatment effects on feeding behavior should be within cow and control for days in milk.

Animals↗

PubMed2003

Technical note: Validation of a system for monitoring feeding behavior of dairy cows.

An electronic system has been designed that allows for passive monitoring of feeding behavior of individual cows housed in a free-stall barn. The objective of this study was to validate the data generated by this GrowSafe feed alley monitoring system. Twelve lactating cows were each monitored for 24 h using both the GrowSafe system and time-lapse video. The GrowSafe estimation of number of meals consumed by each cow showed perfect agreement with meal frequency identified using the video recordings. The duration of these meals, as estimated by GrowSafe, was highly correlated with the meal duration derived from the video (R2 = 0.98). Despite the excellent agreement for these meal-based measures, for each cow we found some instances in which the video showed that a cow was present at the feed alley but GrowSafe failed to detect cow presence (12.6% of observations) and a few instances in which the reverse was true (3.5% of observations). However, all the missed or extraneous data from the GrowSafe system were closely associated in time with known periods of feeding. These results indicate that this feed alley monitoring system can provide very good measures of meal frequency and meal duration and reasonable estimates of instantaneous feed alley attendance for loose-housed dairy cattle.

Animals↗

PubMed2003

Short communication: Diurnal feeding pattern of lactating dairy cows.

The objectives of this research were to: 1) describe the diurnal variation in feed alley attendance patterns of lactating dairy cows, 2) describe the sources of variation in these patterns, and 3) determine the effects of altering the feed push-up schedule on these patterns. An electronic monitoring system was used to record individual cow presence (6-s resolution) at the feed alley for 24 cows housed in a free-stall barn. Cows were subjected to 2 feeding schedules: 1) baseline schedule, where cows were fed at 0600 and 1515 h and feed was pushed closer to the cows at 1100 and 2130 h; and 2) experimental schedule, where 2 additional feed push-ups at 0030 and 0330 h were added to the baseline schedule. With the data collected from the monitoring system, description of the feed alley attendance patterns on a per minute basis of the group of cows was undertaken. Feed alley attendance was consistently higher during the day and early evening compared with the late night and early morning hours. The greatest percentage of cows attending the feed alley was seen after the delivery of fresh feed and the return from milking. The addition of extra feed push-ups in the early morning hours did little to increase feeding activity. It can be concluded that milking and delivery of fresh feed had a much greater affect on the diurnal pattern of feed alley attendance than did the feed push-ups.

Animals↗

PubMed2002

Effect of a fibrolytic enzyme preparation from Trichoderma longibrachiatum on the rumen microbial population of dairy cows.

The effects of supplementing a dairy cow diet with incremental levels of a fibrolytic enzyme preparation (preparation B) from Trichoderma longibrachiatum on the rumen microbial population were investigated. Two cows fitted with rumen cannulae were each fed a diet containing barley-based concentrate (52%), maize silage (29%), and chopped alfalfa hay (19%), supplemented with 0, 1, 2, 5, or 10 L of preparation B per tonne of dry matter (DM). Preparation B stimulated numbers of total viable bacteria in a quadratic manner (P < 0.05), to approximately 230, 330, 390, and 250% at 1, 2, 5, and 10 L x t(-1) DM, respectively. Preparation B increased the numbers of cellobiose-utilizing (P < 0.01), xylanolytic (P < 0.05), and amylolytic bacteria (P < 0.05), but had no effect (P > 0.05) on numbers of cellulolytic bacteria. However, when bacterial numbers enumerated on each substrate were expressed as a proportion of total viable bacterial numbers, only cellobiose utilizers were stimulated, and this stimulation was limited to the 1 L x t(-1) DM level of preparation B (P < 0.05). The results of this study demonstrate that the inclusion of an exogenous fibrolytic enzyme preparation in dairy cow diets increased the numbers of rumen bacteria that utilize hemicelluloses and secondary products of cellulose digestion.

Animal Feed↗

PubMed2002

Evidence of quorum sensing in the rumen ecosystem: detection of N-acyl homoserine lactone autoinducers in ruminal contents.

Acyl-homoserine lactone (AHL) based quorum-sensing systems are widespread among gram-negative bacteria, particularly in association with plants and animals. As yet, there have been no reports of AHL signaling in the anaerobic rumen environment, an ecosystem of great complexity in which cell-cell signaling is likely to occur. We detected multiple AHL autoinducers in the rumen contents of 6 out of 8 cattle fed a representative selection of diets. The signals were not associated with feed. Surprisingly, no pure cultures produced AHLs in vitro when grown under the laboratory conditions we tested. Our observations suggest that either (a) a factor specific to the rumen ecosystem is required for the rumen isolates we tested to produce AHLs or (b) a strain (or strains) that we were not able to culture but which grows to a high cell density in the rumen produces the AHLs we detected.

4-Butyrolactone↗

PubMed2002

Effects of bacterial direct-fed microbials on ruminal fermentation, blood variables, and the microbial populations of feedlot cattle.

A study was conducted to determine whether bacterial direct-fed microbials (DFM) could be used to minimize the risk of acidosis in feedlot cattle receiving high concentrate diets. Six ruminally cannulated steers, previously adapted to a high concentrate diet, were used in a double 3 x 3 Latin square to study the effects of DFM on feed intake, ruminal pH, and ruminal and blood characteristics. Steers were provided ad libitum access to a diet containing steam-rolled barley, barley silage, and a protein-mineral supplement at 87, 9, and 4% (DM basis), respectively. Treatments were as follows: control, Propionibacterium P15 (P15), and Propionibacterium P15 and Enterococcus faecium EF212 (PE). The bacterial treatments (10(9) cfu/g) plus whey powder carrier, or whey powder alone for control, were top-dressed once daily at the time of feeding (10 g/[steer/d]). Periods consisted of 2 wk of adaptation and 1 wk of measurements. Ruminal pH was continuously measured for 6 d using indwelling electrodes. Dry matter intake and ruminal pH (mean, minimum, hours, and area pH < 5.8 or < 5.5) were not affected by treatment (P > 0.05). However, supplementation with P15 increased protozoal numbers (P < 0.05) with a concomitant increase in ruminal NH3 concentration (P < 0.01) and a decrease in the number of amylolytic bacteria (P < 0.05) compared with the control. Streptococcus bovis, enumerated using a selective medium, was numerically reduced with supplementation of PE. Although blood pH and blood glucose were not affected by DFM supplementation, steers fed PE had numerically lower concentrations of blood CO2 than control steers, which is consistent with a reduced risk of metabolic acidosis. Although the bacterial DFM used in this study did not induce changes in DMI or ruminal and blood pH, some rumen and blood variables indicated that the bacterial DFM used in this study may decrease the risk of acidosis in feedlot cattle.

Acidosis↗

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

Chewing activity, saliva production, and ruminal pH of primiparous and multiparous lactating dairy cows.

Four multiparous (MP) and four primiparous (PP) ruminally cannulated lactating Holstein cows were used in a double 4 x 4 Latin square design to study the chewing behavior, saliva production, and ruminal pH of cows in the first or subsequent lactation. Cows were fed one of four diets; three total mixed rations containing 40, 50, or 60% silage (DM basis), and a separate ingredient diet containing 50% concentrate. Dry matter intake was higher for MP cows than for PP cows (19.2 vs. 17.1 kg/d) but not as a percentage of body weight (2.97 +/- 0.06%). Multiparous cows spent more time eating than PP cows (260 vs. 213 min/d, respectively), even after adjustment for dry matter intake (13.8 vs. 12.4 min/kg DM). Multiparous cows also spent more time ruminating per day than PP cows (560 vs. 508 min/d, respectively). Eating salivation rate was not affected by parity, but resting salivation rate was higher for MP cows than for PP. Although MP cows spent more time chewing than PP cows, total daily saliva production was only numerically higher for MP cows because the increase in saliva produced during chewing was accompanied by a decrease in saliva produced during resting. Furthermore, pH profiles tended to be lower for MP cows than for PP cows. Multiparous cows may have a greater risk of incurring acidosis than PP cows because increased salivary secretion associated with increased chewing may not sufficiently compensate the increment of fermentation acids produced in the rumen due to high feed intake.

Animals↗

PubMed2002

Effects of forage particle size and grain fermentability in midlactation cows. I. Milk production and diet digestibility.

Our study investigated the effects of, and interactions between, level of dietary ruminally fermentable carbohydrate (RFC) and forage particle size on milk production, nutrient digestibility, and microbial protein yield for dairy cows fed one level of dietary NDF. Eight cows (61 days in milk) were assigned to four treatments in a double 4 x 4 Latin square. Treatments were arranged in a 2 x 2 factorial design; finely chopped alfalfa silage (FS) and coarse alfalfa silage (CS) were combined with concentrates based on either dry cracked shelled corn (DC; low RFC) or ground high-moisture corn (HMC; high RFC). Diets were fed ad libitum as a total mixed rations with a concentrate to forage ratio of 61:39. Diets based on DC had a predicted NEL content of 1.73 Mcallkg dry matter (DM), while HMC diets contained 1.80 Mcal/kg DM. Diets averaged 18.7% CP, 24.0% NDF, 18.3% ADF, and 27.4% starch on a DM basis. Mean particle size of the four diets was 6.3, 2.8, 6.0, and 3.0 mm for DCCS, DCFS, HMCCS, and HMCFS, respectively. Increasing level of RFC decreased dry matter intake (DMI) from 25.0 to 23.8 kg/ d and organic matter intake from 22.3 to 21.1 kg/d, but intake was not affected by particle size. Milk production averaged 44.0 and 26.8 kg/d solids corrected milk (SCM) and was not affected by diet, but increasing level of RFC tended to increase milk yield. Efficiency of milk production, expressed as SCM/DMI, increased from 1.06 to 1.14 when level of RFC was increased. Milk composition or yield of milk components was not affected by diet, and averaged 3.53% fat, 3.11% protein, 1.55 kg/d fat, and 1.36 kg/d protein. Total tract digestibility of DM and OM increased from 71.4 to 73.0% and 72.4 to 76.1% for DM and OM, respectively, when level of RFC was increased. Total tract digestibility of fiber was unaffected by diet, but total tract starch digestibility increased from 93.1 to 97.4% when HMC replaced DC. Total urinary excretion of the purine derivatives uric acid and allantoin increased from 415 to 472 mmol/d when level of RFC was increased, and calculated microbial N supply increased from 315 to 365 g/d. When expressed as per kilogram of digestible OMI, increasing level of RFC tended to increase microbial N supply (20.4 vs. 22.2 g/kg). Cow productivity was not affected by forage particle size and ruminally fermentable carbohydrates in this study.

Allantoin↗