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The objective of this study was to evaluate the effects of feeding essential oils from garlic (GAR) and juniper berry (JUN), or monensin (MO) on feed intake, ruminal fermentation, the site and extent of digestion, microbial protein synthesis, milk production, and immune status in dairy cows. Four midlactating Holstein cows fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square design with 21-d periods and 4 treatments: control (no additive), MO (330 mg/cow per d), GAR (5 g/cow per d), and JUN (2 g/cow per d). Cows were fed ad libitum a TMR consisting of 40% forage and 60% barley-based concentrate. Dry matter intake averaged 20.4 kg/d and was not affected by dietary additives. Total tract digestibilities of dry matter, organic matter, fiber, and starch were not affected by experimental treatments. However, ruminal digestibilities of dry matter and organic matter were higher (+13%) for GAR and JUN than for the control diet, mainly because of increased crude protein digestion in the rumen. Feeding GAR and JUN increased ruminal digestion of dietary protein by 11% as compared with the control. In contrast, ruminal digestion of dietary protein was reduced by 11% with MO as compared with the control. Milk fat content was lower for MO (2.68%) than for the GAR (3.46%), JUN (3.40%), and control (3.14%) diets. No effects of GAR, JUN, or MO were observed on milk production, ruminal microbial protein synthesis, ruminal pH, and ruminal concentrations of volatile fatty acids and ammonia N. The total and differential numbers of white blood cells as well as serum amyloid A and haptoglobin were not affected by the treatments, suggesting that additives had no effect on the immune status of cows. Results of this study indicate that supplementing dairy cows with GAR (5 g/d) and JUN (2 g/d) essential oils improved feed digestibility in the rumen, but possibly at the expense of a reduction in the flow of bypass protein to the small intestine. Feeding monensin could be beneficial in terms of increasing bypass protein from the rumen but did not improve feed digestion or milk production under the current experimental conditions [ABSTRACT FROM AUTHOR]

Intake of physically effective neutral detergent fiber (peNDF) of dairy cows was altered by adjusting the proportion of forage in the diet and forage particle length, and effects on nutrient intake, site and extent of digestion, microbial N synthesis, and milk production were measured. The experiment was designed as a triplicated 4 x 4 Latin square using 12 lactating dairy cows, with 4 that were ruminally and duodenally cannulated, 4 that were ruminally cannulated, and 4 that were intact. Thus, the site and extent of digestion, and microbial N synthesis were measured in a single 4 x 4 Latin square. Treatments were arranged in a 2 x 2 factorial design; 2 forage particle lengths (FPL) of alfalfa silage (short and long) were combined with low (35:65) and high (60:40) forage:concentrate (F:C) ratios (dry matter basis). Dietary peNDF content was determined from the sum of the proportion (dry matter basis) of dietary dry matter retained either on the 2 screens (8- and 19- mm) or on the 3 screens (1.18-, 8-, and 19-mm) of the Penn State Particle Separator multiplied by the neutral detergent fiber content of the diet. An increased F:C ratio reduced intakes of dry matter and starch by 9 and 46%, respectively, but increased intake of fiber from forage sources by 53%. Digestibility of dry matter in the total tract was not affected, whereas total digestion of fiber and N was improved by increasing the F:C ratio. Improved total fiber digestion resulted from higher ruminal digestion, which was partially due to a shift in starch digestion from the rumen to the intestine with the increased F:C ratio. Actual milk yield was decreased but production of 4% fat-corrected milk was similar between the low and high F:C diets because of increased milk fat content. Increased FPL increased intake of peNDF, especially when the high F:C diet was fed. However, nutrient intakes, N metabolism in the digestive tract, and milk production were not affected. Digestibility of neutral detergent fiber in the total tract was increased because of improved fiber digestion in the rumen with increased FPL. These results indicate that feeding dairy cows a low F:C diet is beneficial in terms of increasing feed intake, microbial N synthesis, and milk production. However, low F:C diets do not maximize feed digestion and production efficiency because of the effects of subacute ruminal acidosis. Increased FPL improves fiber utilization with minimal effects on the digestion of other nutrients and milk production. Increasing dietary peNDF, through an increased proportion of forage or increased FPL, improves fiber digestion because of improved rumen function. [ABSTRACT FROM AUTHOR]

A study was conducted to investigate the effects of physically effective neutral detergent fiber (peNDF) content of dairy cow diets containing corn silage as the sole forage on intake, chewing, ruminal pH, microbial protein synthesis, digestibility, and milk production. A second objective was to compare current methods of measuring peNDF to determine the most suitable approach for use in ration formulation. The experiment was designed as a replicated 3 x 3 Latin square using 6 lactating dairy cows with ruminal cannulas. Diets varied in peNDF content (high, medium, and low) by altering the particle length of corn silage. The physical effectiveness factors (pef) and peNDF contents of the corn silage and diets were determined based on the original (19- and 8-mm sieves) and new Penn State Particle Separator (PSPS; 19-, 8-, and 1.18-mm sieves). A dry-sieving technique that measures the proportion of particles retained on a 1.18-mm sieve was also used. The new PSPS and the 1.18-mm sieve produced similar estimates of pef and peNDF of diets but gave higher values than the original PSPS. There was a much smaller range in pef of corn silage when 3 sieves, rather than 2, were used with the PSPS (range of 0.93 to 0.96 vs. 0.41 to 0.72, respectively). Consequently, increased forage particle length in the diets increased dietary peNDF content and its intake when using the original PSPS; however, the new PSPS and the 1.18-ram sieve failed to detect changes in dietary peNDF and peNDF intake. The peNDF values estimated based on fractional NDF rather than the total NDF content were higher, but the ranking of diets was not changed. Increased intake of peNDF linearly increased digestibility of CP and tended to linearly increase digestibility of fiber in the total tract. As a result, milk yield tended to linearly increase with no effect on milk composition. Ruminal microbial protein synthesis and microbial efficiency were higher with the medium peNDF than with the high or low peNDF diets. Total chewing time and ruminating time were linearly increased with increasing dietary peNDF, whereas influence of dietary peNDF on ruminal pH and fermentation was minimal. This study showed that increasing peNDF content of diets improved fiber digestion. Of the systems used to measure peNDF, the original PSPS provided a good description of dietary particle length and its effects on chewing time and rumen pH, whereas the new PSPS provided a more consistent chewing index, the ratio of total chewing activity to peNDF, across diets varying in chop length of corn silage. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effects of physically effective neutral detergent fiber (peNDF) content of dairy cow diets containing barley silage as the sole forage source on feed intake, chewing activity, and ruminal pH. The experiment was designed as a replicated 3 x 3 Latin square using 6 lactating dairy cows with ruminal cannulas. Cows were offered 1 of 3 diets (high, medium, and low peNDF) obtained using barley silage that varied in particle length: long (theoretical cut length of 9.5 mm), medium (equal proportions of long and fine silages), and fine (theoretical cut length of 4.8 mm). The peNDF contents were determined using the Penn State Particle Separator and were 13.8, 11.8, and 10.5%, for the high, medium, and low diets, respectively. The physical effectiveness factors (defined as proportion retained on 19- and 8-mm screens) for the long and fine silages were 0.84 and 0.68, respectively. Increased forage particle size increased intake of peNDF but did not affect intake of DM and NDF. Ruminating and total chewing time were linearly increased with increasing dietary peNDF. Mean ruminal pH, area between the curve and a horizontal line drawn at pH 5.8 or 5.5, and time that pH was below 5.8 or 5.5 were not affected by peNDF content. Intake of peNDF was not correlated to any chewing activity but proportion of long particles on the 19-mm sieve tended to be correlated to ruminating chews (r = 0.36) and ruminating time (r = 0.36). These results indicate that increasing the peNDF content of diets increases chewing time. However, increased chewing time does not always improve ruminal pH status. Increasing chewing time and thus increasing salivary secretion may not fully overcome the effects of feed digestion and the production of fermentation acids that lower rumen pH. The results suggest that dietary peNDF and fermentable OM intake are critical in regulating rumen pH. Dietary particle size, expressed as peNDF, was a reliable indication of chewing activity. [ABSTRACT FROM AUTHOR]

The objectives of this study were to evaluate effects of dietary factors that alter ruminal fermentability on rumen N degradation, microbial protein synthesis, duodenal flows, and digestibility of amino acids (AA) in the intestines and the total tract. The experiment was a double 4 x 4 quasi-Latin square with a 2³ factorial arrangement of treatments. The dietary factors were extent of barley grain processing, coarse (processing index; PI = 75.5%) or flat (PI = 60.2%); forage-to-concentrate (F:C) ratio, low (35:65) or high (55:45) on a DM basis; and forage particle length (FPL), long (7.59 mm) or short (6.08 mm). Eight lactating cows with ruminal and duodenal cannulas were offered ad libitum access to a total mixed diet. There were no significant interactions between dietary treatments for ruminal N degradation or its duodenal flow and digestibility in the intestines. Passage of microbial protein to the duodenum was improved with increased F:C ratio of the diet but was not affected by grain processing or FPL. Ruminal digestibility of N was increased with increased F:C ratio (49 vs. 60%) and with reduced FPL (59 vs. 50%). Increased grain processing improved N digestibility both in the intestine (15%) and in the total tract (8%). Reduction in the FPL of the diets reduced intestinal N digestion by 14% without affecting the N digestion in the total tract. Increased extent of grain processing tended to enhance duodenal flows of AA. In contrast, reducing FPL lowered flows of dietary AA to the duodenum because of lowered flows of feed plus endogenous N. Increased F:C ratio of the diet did not change the flow of total AA, but there was a reduced flow of dietary AA and increased flow of microbial AA. Flows of several individual AA were increased by feeding flatly rolled barley with limited effects of F:C ratio or FPL. An interaction between grain processing and FPL was detected for flows of some AA. Diets formulated with flatly rolled barley plus long FPL ... [ABSTRACT FROM AUTHOR]

This study was carried out to evaluate the effects of processing method (grinding vs steam-flaking) on DM intake (DMI), ruminal pH and fermentation characteristics, total digestibility of DM, and milk production of dairy cows fed blended barley and corn-based diets. Eight multiparous mid-lactation Holstein cows (88 ± 12 DIM and 44.0 ± 1.5 kg milk/d) were used in a replicated 4 × 4 Latin square design with 21-d long of each period. Cows were fed ad libitum total mixed diet consisting of 25% corn silage, 15% alfalfa hay, and 60% concentrate with equal portion of barley and corn (DM basis). Treatments were: 1) ground barley and corn (GBGC), 2) steam-flaked barley and corn (SBSC), 3) ground barley and steam-flaked corn (GBSC), and 4) steam-flaked barley and ground corn (SBGC). Data were analysed using the MIXED procedure of SAS with model including treatment as fixed effect and the random effects of square, period within square and cow within square. The PDIFF option adjusted by the Tukey method was included in the LSMEANS statement to account for multiple comparisons among treatments. Intake of DM (kg/d) tended (P < 0.06) to be less with SBSC (23.1) than other treatments (averaged 24.2). Digestibility of DM (% of intake) in the total digestive tract was greater (P < 0.04) with SBSC (73.9) and GBSC (73.4) than GBGC (70.3) and tended (P < 0.10) to be greater than SBGC (71.5). However, yield of actual milk (averaged 44.7 kg/d) and 3.5% fat corrected milk (FCM; 39.9 kg/d) as well as milk composition did not differ among treatments. Milk efficiency (milk yield/DMI) tended (P < 0.09) to be improved with SBSC (1.93) vs GBGC (1.85) or SBGC (1.84). Ruminal pH (averaged 6.45), total VFA (averaged 125 mM), and molar proportions of individual VFA were not affected except that molar proportion of acetate tended (P < 0.06) to be greater with SBGC (58.8%) than other treatments (averaged 56.0%). Cows fed GBGC diet had sorting index below 100 for the particles retained on 19- and 8-mm sieves, indicated that cows sorted for these particles. In contrast, cows fed SBSC diet had sorting index superior to 100 for the particles retained on 19 and 8-mm sieves, thus, cows sorted against these particles. These results suggest that feeding cows with blend of steam-flaked barley and corn is beneficial to improve DM digestibility and milk efficiency. [ABSTRACT FROM AUTHOR]

Dry period (DP) length affects energy metabolism around calving in dairy cows as well as milk production in the subsequent lactation. The aim of the study was to investigate milk production, body condition, metabolic adaptation, and hepatic gene expression of gluconeogenic enzymes in Holstein cows (>10,000 kg milk/305 d) with 28- (n = 18), 56- (n = 18), and 90-d DP (n = 22) length (treatment groups) in a commercial farm. Cows were fed total mixed rations ad libitum adjusted for far-off (not for 28-d DP) and close-up DP and lactation. Milk yield was recorded daily and body condition score (BCS), back fat thickness (BFT), and body weight (BW) were determined at dry off, 1 wk before expected and after calving, and on wk 2, 4, and 8 postpartum (pp). Blood samples were taken on d -56, -28, -7, 1, 7, 14, 28, and 56 relative to calving to measure plasma concentrations of metabolites and hormones. Liver biopsies (n = 11 per treatment) were taken on d -10 and 10 relative to calving to determine glycogen and total liver fat concentration (LFC) and to quantify mRNA levels of pyruvate carboxylase (PC), cytosolic phosphoenolpyruvate carboxykinase, and glucose-6-phosphatase. Time course of milk yield during first 8 wk in lactation differed among treatment. Milk protein content was higher in 28-d than in 90-d DP cows. Milk fat to protein ratio was highest and milk urea was lowest in 90-d DP cows. Differences in BW, BFT, and BCS were predominantly seen before calving with greatest BW, BFT, and BCS in 90-d DP cows. Plasma concentrations of NEFA and BHBA were elevated during the transition period in all cows, and the greatest increase pp was seen in 90-d DP cows. Plasma glucose concentration decreased around calving and was greater in 28-d than in 90-d DP cows. Dry period length also affected plasma concentrations of urea, cholesterol, aspartate transaminase, and glutamate dehydrogenase. Plasma insulin concentration decreased around calving in all cows, but insulin concentration pp was greater in 28-d than in 56-d DP cows. Hepatic glycogen concentration decreased and LFC increased after calving in all cows, and LFC was greater pp in 90-d DP than in 28-d DP cows. Hepatic PC mRNA abundance pp tended to increase most in 90-d DP cows. Changes on glucose metabolism were more balanced in cows with a reduced DP, whereas cows with extended DP and elevated body condition indicated greatest metabolic changes according to lipid and glucose metabolism during the transition period. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate the effects of dietary factors that alter ruminal fermentability on intake, duodenal flows and intestinal digestibility of individual amino acids (AA) in lactating dairy cows. The experiment was designed as a 4 x 4 Latin square using 4 ruminally and duodenally cannulated lactating dairy cows. Treatments were arranged in a 2 x 2 factorial design; 2 forage particle lengths (FPL) of alfalfa silage (short and long) were combined with low (35:65) and high (60:40) forage-to-concentrate ratio (F:C; dry matter basis). Four diets were formulated using 2 cuts of alfalfa silage [short (7.9 mm) and long (19.1 mm)], combined with 2 ratios of forage to barley grain concentrate (35:65 and 60:40). Overall, the interactions between dietary F:C and FPL on intake, duodenal flows, and intestinal digestibility of AA were marginal. Intakes of total AA and nonessential AA were not different between low- and high-F:C diets, whereas that of essential AA tended to be less with high-F:C diet as a result of lower intakes of Met, Phe, Arg, and His. The flows of total AA and microbial AA were reduced by 22 and 19%, respectively, with increasing F:C ratio in the diets due to consistently reduced flows of individual AA, whereas AA profiles (% of AA-N) of the duodenal protein were not different. Altering F:C from 35:65 to 60:40 decreased the intestinal digestibility of Ile, Leu, Thr, Val, Ala, Cys, and Ser, and consequently, tended to decrease the digestibility of total AA, essential AA, and nonessential AA. Intakes of total AA, essential AA, and nonessential AA were overall not affected by dietary FPL so FPL did not affect the flows or intestinal digestibility of AA. These results indicate that increasing dietary F:C ratio decreased overall AA supply because flow to the duodenum and intestinal digestibility of AA were decreased. However, increasing FPL had no effect on AA supply. The measured duodenal flows of AA were consistent with the predictions of the Cornell Net Carbohydrate and Protein System model for the low-forage diet, and were consistent with the National Research Council model for the high-forage diet. Furthermore, the digestibility of individual AA in the intestine varied considerably, regardless of dietary treatment. The results revealed the necessity to consider the both flows and digestibility of individual AA when optimizing ration formulation to meet AA requirements of dairy cows. [ABSTRACT FROM AUTHOR]

The objectives of the present in vivo and in situ trials were to evaluate whether feeding barley grain steeped in lactic acid (LA) would affect rumen fermentation patterns, in situ dry matter (DM) degradation kinetics, and milk production and composition in lactating dairy cows. The in vivo trial involved 8 rumen-fistulated Holstein cows fed once daily a total mixed ration containing rolled barley grain (27% in DM) steeped for 48 h in an equal quantity of tap water (CTR) or in 0.5% LA (TRT) in a 2 × 2 crossover design. The in situ trials consisted of incubation of untreated rolled barley grain in cows fed CTR or TRT diets and of incubation of 3 different substrates including CTR or barley grain steeped in 0.5% or 1.0% LA (TRT1 and TRT2, respectively) up to 72 h in the rumen. Results of the in vivo trial indicated that cows fed the TRT diet had greater rumen pH during most intensive fermentation phases at 10 and 12 h post-feeding. The latter effect was associated with a shorter duration in which rumen pH was below 5.8 for cows fed the TRT diet (2.4 h) compared with CTR diet (3.9 h). Furthermore, cows fed the TRT diet had lower concentrations of volatile fatty acids at 2 and 4 h post-feeding. In addition, concentrations of preprandial volatile fatty acids were lower in the rumen fluid of cows fed the TRT diet. Results also showed that molar proportion of acetate was lower, whereas propionate tended to increase by feeding cows the TRT diet. Cows fed the TRT diet demonstrated greater rumen in situ lag time of substrate DM degradation and a tendency to lower the fractional degradation rate. Other in situ results indicated a quadratic effect of LA on the effective rumen degradability of substrates whereby the latter variable was decreased from CTR to TRT1 but increased for TRT2 substrate. Although the diet did not affect actual milk yield, fat-corrected milk, percentages The objectives of the present in vivo and in situ trials were to evaluate whether feeding barley grain steeped in lactic acid (LA) would affect rumen fermentation patterns, in situ dry matter (DM) degradation kinetics, and milk production and composition in lactating dairy cows. The in vivo trial involved 8 rumen-fistulated Holstein cows fed once daily a total mixed ration containing rolled barley grain (27% in DM) steeped for 48 h in an equal quantity of tap water (CTR) or in 0.5% LA (TRT) in a 2 × 2 crossover design. The in situ trials consisted of incubation of untreated rolled barley grain in cows fed CTR or TRT diets and of incubation of 3 different substrates including CTR or barley grain steeped in 0.5% or 1.0% LA (TRT1 and TRT2, respectively) up to 72 h in the rumen. Results of the in vivo trial indicated that cows fed the TRT diet had greater rumen pH during most intensive fermentation phases at 10 and 12 h post-feeding. The latter effect was associated with a shorter duration in which rumen pH was below 5.8 for cows fed the TRT diet (2.4 h) compared with CTR diet (3.9 h). Furthermore, cows fed the TRT diet had lower concentrations of volatile fatty acids at 2 and 4 h post-feeding. In addition, concentrations of preprandial volatile fatty acids were lower in the rumen fluid of cows fed the TRT diet. Results also showed that molar proportion of acetate was lower, whereas propionate tended to increase by feeding cows the TRT diet. Cows fed the TRT diet demonstrated greater rumen in situ lag time of substrate DM degradation and a tendency to lower the fractional degradation rate. Other in situ results indicated a quadratic effect of LA on the effective rumen degradability of substrates whereby the latter variable was decreased from CTR to TRT1 but increased for TRT2 substrate. Although the diet did not affect actual milk yield, fat-corrected milk, percentages [ABSTRACT FROM AUTHOR]