Effects of method of barley grain processing and source of supplemental dietary fat on duodenal nutrient flows, milk fatty acid profiles, and microbial protein synthesis in dairy cows.

The objective of this study was to determine the interactive effects of barley grain processing and source of supplemental fat on ruminal nutrient digestion, duodenal nutrient flow, microbial protein synthesis, and milk fatty acid (FA) profiles in dairy cows. Four Holstein cows (656 ± 28 kg of BW; 80 ± 12 d in milk) fitted with permanent ruminal and duodenal cannulas were used in a 4×4 Latin square design with a 2×2 factorial arrangement of experimental treatments, in which barley was either dry-rolled (DRB) or pelleted (PB) and supplemented with full-fat canola seed (canola) or full-fat flaxseed (flaxseed). Cows fed DRB consumed 1.8 to 3.5 kg/d more dry matter compared with those fed PB. Mean ruminal pH was lower and the duration (min/d) and area (pH × min) of total ruminal acidosis (RA; ruminal pH <5.8), mild RA (5.8 >ruminal pH >5.5), and severe RA (5.5 >ruminal pH >5.2), and the duration of acute RA (ruminal pH <5.2) were greater in cows fed PB compared with those fed DRB. Milk yield was unaffected by diet. Milk fat content and yield were greater in cows fed DRB than in cows fed PB. Cows fed PB had greater duodenal flows of C18:1 trans, C18:1 cis, C18:2 trans-9,trans-12, C18:2 trans-9,cis-12, C18:2 trans-11,cis-15, and C18:2 trans-10,cis-12 compared with those fed DRB. Duodenal flows of C18:1 cis, C18:1 trans, total C18:1, C18:2n6, C18:2 cis-9,trans-11, C18:2 trans-10,cis-12, C18:2 trans-11,trans-13, total conjugated linoleic acid (CLA), and C18:3n3 were greater in cows fed flaxseed compared with those fed canola. Milk concentrations of C18:3n3 and total CLA tended to be greater in cows fed PB compared with those fed DRB. When compared with cows fed canola, milk concentrations of C18:2 trans-11,cis-15, C18:2 cis-9,trans-11, C18:2 trans-11,trans-13, total CLA, and C18:3n3 were greater in cows fed flaxseed. Ruminal digestion of neutral detergent fiber and acid detergent fiber was greater in cows fed DRB compared with those fed PB. Duodenal flow of ammonia-N tended to be greater in cows fed PB compared with those fed DRB. Duodenal flow of nonammonia nonmicrobial N was greater in cows fed flaxseed compared with those fed canola; however, barley grain processing did not affect duodenal nonammonia nonmicrobial N flow. Duodenal flow of microbial nonammonia N and microbial efficiency were not affected by diet. In summary, barley grain processing and source of fat altered ruminal FA biohydrogenation, and this was reflected in changes in duodenal FA flow and milk FA profiles; however, ruminal microbial protein synthesis was unaltered.

Effects of subacute ruminal acidosis challenges on fermentation and endotoxins in the rumen and hindgut of dairy cows.

The effects of a grain-based subacute ruminal acidosis (SARA) challenge (GBSC) and an alfalfa-pellet SARA challenge (APSC) on fermentation and endotoxins in the rumen and in the cecum, as well as on endotoxins in peripheral blood, were determined. Six nonlactating Holstein cows with cannulas in the rumen and cecum were used in the study. A 3×3 Latin square arrangement of treatments with 4-wk experimental periods was adopted. During the first 3 wk of each experimental period, all cows received a diet containing 70% forages [dry matter (DM) basis]. In wk 4 of each period, cows received 1 of the following 3 diets: the 70% forage diet fed during wk 1 to 3 (control), a diet in which 34% of the dietary DM was replaced with grain pellets made of 50% ground wheat and 50% ground barely (GBSC), or a diet in which 37% of dietary DM was replaced with pellets of ground alfalfa (APSC). Rumen pH was monitored continuously using indwelling pH probes, and rumen fluid, blood, cecal digesta, and fecal grab samples were collected immediately before feed delivery at 0900 h and at 6 h after feed delivery on d 3 and 5 of wk 4. The time for which rumen pH was below 5.6 was 56.4, 225.2, and 298.8 min/d for the control, APSC, and GBSC treatments, respectively. Compared with the control, SARA challenges resulted in similar reductions in cecal digesta pH, which were 7.07, 6.86, and 6.79 for the control, APSC, and GBSC treatments, respectively. Compared with the control, only GBSC increased starch content in cecal digesta, which averaged 2.8, 2.6, and 7.4% of DM for the control, APSC, and GBSC, respectively. Free lipopolysaccharide endotoxin (LPS) concentration in rumen fluid increased from 10,405 endotoxin units (EU)/mL in the control treatment to 30,715 and 168,391 EU/mL in APSC and GBSC, respectively. Additionally, GBSC increased the LPS concentration from 16,508 to 118,522 EU/g in wet cecal digesta, and from 12,832 to 93,154 EU/g in wet feces. The APSC treatment did not affect LPS concentrations in cecal digesta and feces. All concentrations of LPS in blood plasma were below the detection limit of >0.05 EU/mL of the technique used. Despite the absence of LPS in blood, only GBSC increased the concentration of LPS-binding protein in blood plasma, which averaged, 8.9, 9.5, and 12.1mg/L for the control, APSC, and GBSC treatments, respectively. This suggests that GBSC caused translocation of LPS from the digestive tract but that LPS was detoxified before entering the peripheral blood circulation. The higher LPS concentration in cecal digesta in the GBSC compared with the APSC suggests a higher risk of LPS translocation in the large intestine in GBSC than in APSC.

Effects of type of canola protein supplement on ruminal fermentation and nutrient flow to the duodenum in beef heifers.

Ruminal fermentation, nutrient digestion, and flows to the duodenum in growing cattle fed differently produced canola protein supplements were studied in a 4 x 4 Latin square design using Speckle Park heifers (initial BW = 451 +/- 26 kg). Canola protein supplement treatments consisted of the following: 1) 8.78% regular canola meal (RCM); 2) 9.25% RCM plus 1.80% canola oil (RCMO); 3) 11.1% canola presscake from biodiesel oil extraction (CPC); and 4) 8.14% high ruminally undegradable protein (RUP) canola meal (RUCM) plus 1.32% canola oil (RUCMO). Experimental diets also contained 39.9, 40.2, 39.9, and 39.9% barley grain; 31.7, 31.4, 31.2, and 31.4% barley silage; and 17.5, 15.2, 15.6, and 16.5% oat hulls for the RCM, RCMO, CPC, and RUCMO diets, respectively. Feeding the CPC, RCMO, and RUCMO diets decreased (P < or = 0.05) ruminal NH(3)-N concentration compared with feeding the RCM diet. Compared with the RCM diet, adding canola oil in the RCMO diet or residual oil in the CPC diet resulted in greater ruminal concentrations of propionate (P < or = 0.09). Additionally, feeding the RCMO diet also resulted in greater ruminal concentrations of acetate (P = 0.07), valerate (P = 0.06), and total VFA (P = 0.07) compared with the RCM diet. Also, compared with the RCM diet, heifers on the RUCMO diet had decreased acetate (P = 0.02) concentrations. The changes in ruminal concentrations of acetate and propionate resulted in reduced acetate:propionate ratios in the RCMO (P = 0.08), CPC (P = 0.02), and RUCMO (P < 0.01) diets. Ruminal digestion and flows of nutrients to the duodenum were not affected by dietary treatment. However, adding canola oil to the RCMO and RUCMO dietary treatments decreased the digestibility of ADF (P < or = 0.08) and NDF (P < or = 0.08) in the total tract compared with the RCM diet. Total tract digestibility of OM was also decreased (P = 0.02) in heifers fed the RUCMO compared with the RCM diet. Notwithstanding the different processing methods employed in making RCM, CPC, or RUCM, there were no differences among the diets for ruminally degraded protein, ruminal microbial protein synthesis, and the flow of N fractions to the duodenum.

Effects of peripartum propylene glycol supplementation on nitrogen metabolism, body composition, and gene expression for the major protein degradation pathways in skeletal muscle in dairy cows.

Early-lactating dairy cows mobilize body protein to provide amino acids that are directed toward gluconeogenesis and milk protein synthesis. Propylene glycol (PG) is a precursor of ruminal propionate, and feeding PG has been reported to improve energy supply by increasing blood glucose. Our hypothesis was that feeding PG could spare body protein by providing an alternative source of carbon for gluconeogenesis. The major objectives of this study were 1) to delineate the effects of pre- and postpartum PG supplementation in transition dairy cows on whole-body nitrogen balance, urinary 3-methylhistidine (3-MH) excretion, body composition, and gene expression profiles for the major protein degradation pathways in skeletal muscle; and 2) to characterize the changes in body protein metabolism during the periparturient period. Sixteen pregnant cows (7 primiparous and 9 multiparous) were paired based on expected calving dates and then randomly assigned within each pair to either a basal diet (control) or basal diet plus 600 mL/d of PG. Diets were fed twice daily for ad libitum intake, and PG was fed in equal amounts as a top dress from d -7 to d 45. All measurements were conducted at 3 time intervals starting at d -14 +/- 5, d 15, and d 38 relative to calving. Propylene glycol had no effect on whole-body N balance, urinary 3-MH excretion, or body composition. However, N balance was lower at d 15 and 38, compared with d -14. Urinary excretion of 3-MH was lower at d -14 than at d 15 and 38. Supplemental PG had no effect on body weight (BW) and all components of empty BW. On average, cows fed both diets mobilized 19 kg of body fat and 14 kg of body protein between d -14 and d 38. Supplemental PG had no effect on mRNA abundance in skeletal muscle for m-calpain, and the 14-kDa ubiquitin-carrier protein E2 (14-kDa E2) and proteasome 26S subunit-ATPase components of the ubiquitin-mediated proteolytic pathway; however, PG supplementation downregulated mRNA expression for mu-calpain at d 15, and tended to downregulate mRNA expression for ubiquitin at d 15 and 38. Relative to calving, mRNA abundance for m- and mu-calpain, ubiquitin, and 14-kDa E2 were greater at d 15 compared with d -14 and d 38. In summary, these results indicate that transitional effects on whole-body metabolism and gene expression for the Ca(2+)-dependent and ubiquitin-mediated proteolytic pathways in skeletal muscle were more pronounced than those elicited by PG supplementation.

Influence of carbohydrate source on ruminal fermentation characteristics, performance, and microbial protein synthesis in dairy cows.

Eight multiparous Holstein cows (676 +/- 57 kg of body weight; 121 +/- 17 d-in-milk) were used in a replicated 4 x 4 Latin square design to determine the effects of 4 sources of carbohydrate on milk yield and composition, ruminal fermentation, and microbial N flow to the duodenum. Four cows in one of the Latin squares were fitted with permanent ruminal cannulae. Diets contained (DM basis) 50% forage in combinations of alfalfa hay and barley silage, and 50% concentrate. The concentrate portion of the diets contained barley, corn, wheat, or oats grain as the primary source of carbohydrate. Intake of DM ranged from 24.0 to 26.2 kg/d, and it tended to be lower in cows fed the wheat-based diet compared with those fed the barley-based diet; consequently, milk yield tended to be lower in cows fed the wheat-based diet compared with those fed the barley-based diet. Cows fed the barley- or wheat-based diets had a lower milk fat content compared with those fed the corn-based diet. Ruminal fermentation characteristics were largely unaffected by the source of dietary carbohydrate, with similar ruminal pH and volatile fatty acid and ammonia concentrations for the first 6 h after the morning feeding. Dietary treatment did not affect total tract apparent digestibility of DM, organic matter, and neutral detergent fiber; however, total tract apparent digestibility of starch in cows fed the oats-based diet was higher compared with those fed the corn-and wheat-based diets. Nitrogen that was used for productive purposes (i.e., N secreted in milk + N apparently retained by the cow) tended to be lower in cows fed the wheat-based diet compared with cows fed the barley-, corn-, or oats-based diets. Urinary purine derivative (PD) excretion was similar in cows fed the barley-, corn-, and wheat-based diets; however, purine derivative excretion was higher in cows fed the barley-based diet compared with those fed the oats-based diet. Consequently, estimated microbial N flow to the duodenum was 49 g/d higher in cows fed the barley-based diet compared with those fed the oats-based diet. Improved production performance with corn and barley diets appeared to be due to greater nutrient absorption than in cows fed oats and wheat diets, rather than improved nutrient utilization efficiency.

Subacute ruminal acidosis in dairy cows: the physiological causes, incidence and consequences.

During subacute ruminal acidosis (SARA) rumen pH is depressed for several hours per day due to accumulation of volatile fatty acids and insufficient rumen buffering. Surveys suggested an incidence of SARA of between 19% and 26% in early and mid-lactation dairy cows. Causes of SARA include feeding excessive amounts of non-structural carbohydrates and highly fermentable forages, and insufficient dietary coarse fiber. Consequences of SARA include feed intake depression, reduced fiber digestion, milk fat depression, diarrhea, laminitis, liver abscesses, increased production of bacterial endotoxin and inflammation characterized by increases in acute phase proteins. The increase in endotoxin is similar among methods for SARA induction, but depends on the diet fed before induction. Increases in acute phase proteins vary among methods of SARA induction, even when the methods result in similar rumen pH depressions. This suggests that the inflammatory response might not be solely due to bacterial endotoxin in the rumen.

Interactions between barley grain processing and source of supplemental dietary fat on nitrogen metabolism and urea-nitrogen recycling in dairy cows.

The objective of this study was to determine the effects of methods of barley grain processing and source of supplemental fat on urea-N transfer to the gastrointestinal tract (GIT) and the utilization of this recycled urea-N in lactating dairy cows. Four ruminally cannulated Holstein cows (656.3 +/- 27.7 kg of BW; 79.8 +/- 12.3 d in milk) were used in a 4 x 4 Latin square design with 28-d periods and a 2 x 2 factorial arrangement of dietary treatments. Experimental diets contained dry-rolled barley or pelleted barley in combination with whole canola or whole flaxseed as supplemental fat sources. Nitrogen balance was measured from d 15 to 19, with concurrent measurements of urea-N kinetics using continuous intrajugular infusions of [15N 15N]-urea. Dry matter intake and N intake were higher in cows fed dry-rolled barley compared with those fed pelleted barley. Nitrogen retention was not affected by diet, but fecal N excretion was higher in cows fed dry-rolled barley than in those fed pelleted barley. Actual and energy-corrected milk yield were not affected by diet. Milk fat content and milk fat yield were higher in cows fed dry-rolled barley compared with those fed pelleted barley. Source of supplemental fat did not affect urea-N kinetics. Urea-N production was higher (442.2 vs. 334.3 g of N/d), and urea-N entering the GIT tended to be higher (272.9 vs. 202.0 g of N/d), in cows fed dry-rolled barley compared with those fed pelleted barley. The amount of urea-N entry into the GIT that was returned to the ornithine cycle was higher (204.1 vs. 159.5 g of N/d) in cows fed dry-rolled barley than in pelleted barley-fed cows. The amount of urea-N recycled to the GIT and used for anabolic purposes, and the amounts lost in the urine or feces were not affected by dietary treatment. Microbial nonammonia N supply, estimated using total urinary excretion of purine derivatives, was not affected by diet. These results show that even though barley grain processing altered urea-N entry into the GIT, the utilization of this recycled urea-N for microbial production was unaffected as the additional urea-N, which entered the GIT was returned to ureagenesis.

Ruminal lipopolysaccharide concentration and inflammatory response during grain-induced subacute ruminal acidosis in dairy cows.

The effects of grain-induced subacute ruminal acidosis (SARA) in lactating dairy cows on free ruminal lipopolysaccharide (LPS) and indicators of inflammation were determined. Four mid lactation dairy cows were divided into 2 groups of 2 cows and used in a repeated switchover design. During each period, SARA was induced in 2 animals for 5 subsequent days by replacing 25% of their total mixed ration (dry matter basis) with a concentrate made of 50% wheat and 50% barley. The other 2 cows acted as controls and were fed a total mixed ration diet in which 44% of dry matter was concentrate. On average, inducing SARA did not affect milk composition, increased the duration of rumen pH below 5.6 from 187 to 309 min/d, and increased free ruminal LPS concentration from 24,547 endotoxin units (EU)/mL to 128,825 EU/mL. Averaged across treatments, milk fat yield and milk protein yield were 0.66 and 1.00 kg/d, respectively. Rumen pH and milk fat data suggest that control cows also experienced ruminal acidosis, albeit a milder form of this disease than SARA cows. Serum LPS concentration in both control and SARA cows was less than the detection limit of <0.01 EU/mL for the assay. Induction of SARA elevated serum amyloid A concentration from 286.8 to 498.8 mug/mL, but did not affect other markers of inflammation including haptoglobin, fibrinogen, serum copper, or white blood cells. These results suggest that grain-induced SARA in mid lactation dairy cows increases the lysis of gram-negative bacteria and activates an inflammatory response.

Rumen lipopolysaccharide and inflammation during grain adaptation and subacute ruminal acidosis in steers.

Three rumen-fistulated Jersey steers were gradually adapted to a wheat-barley concentrate over a 4-wk period. Adaptation steps consisted of four 1-wk periods during which steers were fed diets with forage-to-concentrate (F:C) ratios of 100:0, 79:21, 59:41, and 39:61. The forage consisted of chopped hay (CH), and the concentrate consisted of pelleted concentrate containing 50% ground wheat and 50% ground barley. Steers were fed the all-forage diet ad libitum during wk 1. Feed offered in wk 2 to 4 was kept constant at the ad libitum intake during wk 1. On 2 d that were set 3 d apart during wk 5, subacute ruminal acidosis (SARA) was induced in the steers by feeding a diet with an F:C ratio of 24:76 by offering them 0.9 kg of CH at 0900 h followed by 2 meals of 3.0 kg each of wheat-barley pellets (WBP) at 1100 h and 1300 h and 0.9 kg of CH at 1700 h, to depress rumen pH for at least 3 h/d below 5.6. The average concentrate inclusion for the SARA induction diet was 76 +/- 10% DM. During stepwise adaptation, time with pH below 5.6 increased to an average of 121 min/d when the steers were consuming a diet containing 61% DM as WBP. Dietary inclusion of WBP at the rate of 76% DM induced SARA because the steers spent an average of 219 min/d with pH below 5.6. The free ruminal lipopolysaccharide (LPS) concentration increased from 6,310 endotoxin units (EU)/mL with the all-forage diet to 18,197 EU/mL with the 61% concentrate diet. The ruminal LPS concentration increased to 26,915 EU/mL when SARA was induced. Serum haptoglobin increased from 0.53 mg/mL when steers were on the all-forage diet to 1.90 mg/mL with the 61% concentrate diet and were not increased further by inducing SARA. The serum amyloid-A concentration was not affected by increasing dietary concentrate during stepwise adaptation to the concentrate, but increased from 71 to 163 microg/mL when SARA was induced. A gradual increase in dietary concentrate so that the F:C ratio decreased to 39:61 resulted in increased ruminal LPS concentrations. Subsequent induction of SARA further increased ruminal LPS and activated an inflammatory response.

Subacute ruminal acidosis induces ruminal lipopolysaccharide endotoxin release and triggers an inflammatory response.

Subacute ruminal acidosis (SARA) was induced in 3 rumen fistulated Jersey steers by offering them different combinations of wheat-barley pellets and chopped alfalfa hay. Steers were offered 4, 5, and 6 kg/d of pelleted concentrate and 6, 5, and 4 kg/d of chopped alfalfa hay for diets 1, 2, and 3, respectively, during 5-d treatment periods and were fed chopped alfalfa hay between treatment periods. Inducing SARA increased blood concentrations of haptoglobin and serum amyloid-A. Dry matter intake of concentrate and hay decreased from d 1 to 5 in each period. Subacute ruminal acidosis was induced in all steers during d 4 and 5 when concentrate was fed, with ruminal pH remaining below 5.6 for an average of 187 and 174 min/d on these days. Lipopolysaccharide concentration increased significantly during periods of grain feeding compared with times when only hay was fed. Inducing SARA by feeding wheat-barley pellets activated a systemic inflammatory response in the steers.