Feeding high proportions of barley grain in a total mixed ration perturbs diurnal patterns of plasma metabolites in lactating dairy cows.

The aim of this study was to evaluate effects of feeding increasing proportions of barley grain in a total mixed ration (TMR) on diurnal plasma metabolite fluctuations in high-producing dairy cows. Eight early- to mid-lactation (60 to 140 d in milk) primiparous Holstein cows were assigned to a double 4 x 4 Latin square experimental design. Each experimental period lasted 21 d with the first 11 d used for diet adaptation. Cows were fed a TMR once daily at 0800 h containing no barley grain (control diet), or 15, 30, and 45% (dry matter basis) barley grain as well as barley silage. Blood samples were collected from the tail vein on the last day of each period shortly before (i.e., 0 h) and at 2, 4, 6, 8, 10, and 12 h after the morning feeding. Concentrations of glucose, nonesterified fatty acids (NEFA), beta-hydroxybutyric acid, cholesterol, and lactate in plasma were measured. Results of this study showed that feeding increasing proportions of barley grain affected concentrations of glucose and lactate in plasma with greater plasma glucose and lactate in cows fed the highest amount of grain; however, the amount of grain in the diet did not have an effect on diurnal patterns of plasma glucose. Additionally, the concentration of NEFA in plasma was greater in cows fed the higher grain diets and was greater in the hours following the morning meal than later in the day. The amount of grain in the diet was associated with lower plasma beta-hydroxybutyric acid, which increased particularly after the morning meal. Interestingly, cows fed the most barley grain had the lowest plasma cholesterol and this decreased during the day. In conclusion, the concomitant increase of glucose, lactate, and NEFA as well as the decrease of plasma cholesterol in cows fed high proportions of barley grain suggest that high inclusion of barley grain in the diet played a role in the diurnal patterns of plasma metabolites in lactating dairy cows. However, further research is warranted to understand involvement of these metabolic changes on the long-term health and productivity of dairy cows.

Plasma luteinizing hormone concentrations in cows given repeated treatments or three different doses of gonadotropin releasing hormone.

We hypothesized that: (i) repeated GnRH treatments would increase the magnitude and duration of the LH surge and would increase progesterone (P4) concentrations after ovulation; and (ii) the release of pituitary LH would be greater in response to larger doses of GnRH. In Experiment 1, ovary-intact cows were given an intravaginal P4 (1.9g) insert (CIDR) for 10 d and 500 microg cloprostenol (PGF) at CIDR removal to synchronize estrus. On Days 7 or 8 after estrus, cows received two PGF treatments (12h apart) and 100 microg GnRH at 36 (Control), 36 and 38 (GnRH38), or 36 and 40h (GnRH40) after the first PGF. Mean plasma LH concentration (ng/mL) was greater (P<0.05) in GnRH38 (8.8+/-1.1) than in Control (5.1+/-1.3), with that in GnRH40 (5.8+/-1.3) being intermediate. Although the duration (h) of the LH surge was longer in GnRH40 (8.0+/-0.4) than in either GnRH38 (P<0.05; 7.0+/-0.3) or Control (P<0.09; 7.1+/-0.4), mean postovulatory P4 (ng/mL) was greater (P<0.01) in Control (4.2+/-0.7) than in GnRH38 (2.9+/-0.6) or GnRH40 (3.0+/-0.7) cows. In Experiment 2, ovariectomized cows were given a CIDR for 10 d and 2mg of estradiol cypionate im at CIDR insertion. Thirty-six hours after CIDR removal, cows received, 50, 100, or 250 microg of GnRH. Cows given 250 microg GnRH released more LH (9.4+/-1.4ng/mL) than those given 50 or 100 microg (6.1+/-1.3 and 5.4+/-1.4ng/mL, respectively), and had an LH surge of longer duration than those given 50 microg (6.8+/-0.4 vs. 5.1+/-0.3h). In summary, ovary-intact cows in the GnRH38 group had greater mean and peak LH concentrations, but subsequent plasma P4 concentrations were lower than in Control cows. Ovariectomized cows given 250 microg GnRH had a greater pituitary release of LH.

Pregnancy rates to timed artificial insemination in Holstein heifers given prostaglandin F2alpha twenty-four hours before or concurrent with removal of an intravaginal progesterone-releasing insert.

The objective was to compare pregnancy rates in nulliparous Holstein heifers given PGF(2alpha) 24 h before, or concurrent with, removal of an intravaginal progesterone-releasing (CIDR) insert in 3 timed artificial insemination (TAI) protocols. Heifers (from 2 herds) were assigned randomly, over 11 mo, to 1 of 3 modified Ovsynch protocols. On d 0 (without reference to the stage of the estrous cycle), all heifers were given 100 microg of GnRH i.m. and a CIDR insert (containing 1.9 g of progesterone). In the PG-7/P4-8 protocol (n = 99), PGF(2alpha) was given on d 7, and CIDR inserts were removed on d 8. In the PG-7/P4-7 (n = 98) and PG-8/P4-8 (n = 102) protocols, PGF(2alpha) administration and CIDR removal occurred concurrently, on d 7 or 8, respectively. In all 3 protocols, a second GnRH treatment (100 microg) was given 48 h after PGF(2alpha) with TAI 16 to 20 h later. Blood samples were collected (subset of 124 heifers) on d 0, 7, 10 or 11 (i.e., at TAI), and 17. Pregnancy rates (32 d after TAI) for protocols PG-7/P4-8, PG-7/P4-7, and PG-8/P4-8 were 61.8, 55.6, and 54.1%, respectively. Pregnancy rate was higher when synchronization was initiated during diestrus than when initiated at other stages (57.0 versus 34.8%). Although pregnancy rates were not affected by season, there was an interaction between protocol and season; pregnancy rates were significantly lower in summer in heifers subjected to PG-7/P4-7 and PG-8/P4-8, but season did not affect pregnancy rates in heifers subjected to PG-7/P4-8. In summary, giving PGF(2alpha) 24 h before CIDR removal, followed by TAI (PG-7/P4-8 protocol), resulted in consistent pregnancy rates, regardless of season, relative to protocols involving PGF(2alpha) treatment concurrent with CIDR removal.

Feeding high proportions of barley grain stimulates an inflammatory response in dairy cows.

The objective of this study was to evaluate effects of feeding increasing proportions of barley grain on acute phase response in lactating dairy cows. Eight cannulated primiparous (60 to 140 d in milk) Holstein dairy cows were assigned to 4 diets in a 4 x 4 Latin square experimental design. The experimental period lasted for 21 d, with 11 d of adaptation and 10 d of measurements. Cows were fed the following diets: 1) no barley grain in the diet, 2) 15% barley grain, 3) 30% barley grain, and 4) 45% barley grain, as well as barley and alfalfa silage and alfalfa hay at 85, 70, 55, and 40% [dry matter (DM) basis]. All cows were supplemented with a 15% concentrate mix. Blood and rumen fluid samples were collected on d 1, 3, 5, 7, and 10 of the measurement period, and pH and endotoxin content were measured in rumen samples. Concentrations of serum amyloid A, lipopolysaccharide-binding protein, haptoglobin, and C-reactive protein in plasma were measured by ELISA. Feeding high proportions of barley grain at 0, 15, 30, and 45% of DM was associated with lower feed intake (32.6, 32.9, 27.34, and 25.18 kg/d +/- 1.30, respectively), lower ruminal pH (6.8, 6.7, 6.7, and 6.5 +/- 0.03, respectively), and higher DM intake (13.33, 15.28, 14.68, and 16.04 +/- 0.63 kg/d, respectively) and milk production (27.2, 28.2, 29.0, and 31.0 +/- 1.2 kg/d, respectively). Ruminal endotoxin increased in cows receiving 30 and 45% barley grain (5,021, and 8,870 +/- 393 ng/mL, respectively) compared with those fed no grain or 15% barley grain (654 and 790 +/- 393 ng/mL, respectively). Plasma concentrations of serum amyloid A, lipopolysaccharide-binding protein, and C-reactive protein increased in cows given higher (30 and 45%) proportions of grain. Plasma haptoglobin was not affected by treatments. In conclusion, feeding dairy cows high proportions (30 and 45% DM basis) of barley grain was associated with lower feed intake and rumen pH, increased endotoxin in the rumen fluid, and stimulation of an inflammatory response.

Acidosis and lipopolysaccharide from Escherichia coli B:055 cause hyperpermeability of rumen and colon tissues.

The objective of the present investigation was to evaluate the effects of acidic pH of the perfusate and presence of lipopolysaccharide (LPS) on permeability of rumen and colon mucosal tissues to mannitol and LPS using the Ussing chamber system. Rumen and colon tissues (n = 8), obtained from slaughtered feedlot steers, were tested for changes in permeability to (3)H-mannitol under pH of 4.5, 5.5, and 6.5 for rumen and at 5.5, 6.5, and 7.4 for colon, with or without LPS from Escherichia coli B:055 at 500 microg/mL. The (3)H-Mannitol was added at 10 microL (525.4 GBq/mmol) on the mucosal side of the Ussing chamber to detect changes in permeability, and 4 samples were taken at 20, 25, 30, and 35 min from the serosal side. Permeability of rumen and colon mucosa to (3)H-mannitol increased 6- and 5-fold, respectively, at acidic pH values of 4.5 and 5.5 and in the presence of 500 micro/mL of LPS. In contrast, LPS did not affect rumen and colon permeability at pH that ranged from 5.5 and 7.4. Translocation of LPS across the rumen and colon mucosa of cattle was not pH dependent. The LPS translocated through these tissues if present at the mucosal side. In conclusion, the permeability of rumen and colon tissues to (3)H-mannitol increased in presence of LPS and under acidic pH, whereas LPS permeated through mucosal tissues independently of the pH of the perfusate. Further research is warranted to understand the mechanism(s) by which acidic pH of the rumen digesta and presence of LPS make rumen and colon tissues "leaky".

Feeding live cultures of Enterococcus faecium and Saccharomyces cerevisiae induces an inflammatory response in feedlot steers.

Two experiments were conducted to investigate the effects of oral supplementation of the lactic-acid-producing bacterium Enterococcus faecium EF212 alone or in combination with Saccharomyces cerevisiae (yeast) on mediators of the acute phase response in feedlot steers. Eight fistulated steers were used to study the effects of E. faecium alone or with yeast in a crossover design with 2 Latin squares, 4 steers within each square, and 2 periods. The length of each period was 3 wk, with a 10-d adaptation and an 11-d measurement period. The experimental diet contained 87% steam-rolled barley, 8% whole-crop barley silage, and 5% supplement (DM basis). In Exp. 1, treatments were control vs. the lactic-acid-producing bacterium E. faecium (6 x 10(10) cfu/d). In Exp. 2, treatments were control vs. E. faecium (6 x 10(10) cfu/d) and S. cerevisiae (6 x 10(10) cfu/d). The bacteria and yeast supplements were blended with calcium carbonate to supply 6 x 10(10) cfu/d when top-dressed into the diet once daily at the time of feeding (10 g/d). Steers fed the control diet received only carrier (10 g/d). Blood samples were collected from the jugular vein on d 17 and 21 of each period, and serum amyloid A (SAA), lipopolysaccharide binding protein (LBP), haptoglobin, and alpha1-acid glycoprotein (alpha1-AGP) were measured. Supplementation of feed with E. faecium had no effect on concentrations of SAA, LBP, haptoglobin, or alpha1-AGP in plasma compared with those of controls. However, feeding E. faecium and yeast increased (P = 0.02) plasma concentrations of SAA, LBP, and haptoglobin but had no effect on plasma alpha1-AGP. In conclusion, oral supplementation of E. faecium alone had no effect on the mediators of the acute phase response that were measured, whereas feeding of E. faecium and yeast induced an inflammatory response in feedlot steers fed high-grain diets. Further research is warranted to determine the mechanism(s) by which E. faecium and yeast stimulated production of acute phase proteins in feedlot steers.

Parenteral administration of glutamine modulates acute phase response in postparturient dairy cows.

The objective of this study was to investigate whether administration of L-Gln would affect mediators of acute phase response in postparturient dairy cows. Twenty-four multiparous Holstein cows were blocked by the expected day of calving and randomly assigned to 1 of the 3 treatment groups (n = 8/group): 1) i.v. infusion of 10 L of 0.85% NaCl (control), 2) i.v. infusion of 106, or 3) 212 g/d of L-Gln mixed with 10 L of 0.85% NaCl solution; each treatment was given 8 h/d for each of 7 consecutive days starting on d 1 after calving. Blood samples were collected 1 wk before the expected day of parturition as well as on d 0, 7, 14, and 21 after parturition; plasma concentrations of serum amyloid A (SAA), haptoglobin, and lipopolysaccharide-binding protein were measured by ELISA, and alpha(1)-acid glycoprotein was assessed by radial immunodiffusion. Concentrations of SAA, haptoglobin, and alpha(1)-acid glycoprotein increased in control cows after parturition, reaching peak values on d 0 or 7 postpartum (60, 1,093, and 963 microg/mL, respectively). Cows infused with 106 g/d of L-Gln had greater concentrations of SAA in plasma on d 14 and 21 compared with controls (62.8 vs. 30.2 and 71.1 vs. 34.5 microg/mL, respectively). Cows infused with 212 g/d of L-Gln had greater concentrations of SAA on d 7 (82.5 vs. 53.9 microg/mL) and lower concentrations of haptoglobin on d 14 and 21 postpartum compared with controls (264 vs. 621 and 175 vs. 587 microg/mL, respectively). Cows treated with 106 and 212 g/d of L-Gln had greater plasma lipopolysaccharide-binding protein concentrations on d 7 compared with control group (50.0 and 35.6 vs. 10.8 microg/mL, respectively). There were no treatment differences with respect to milk yield and DM intake during the experimental period. In conclusion, our data indicate that i.v. administration of L-Gln modulated acute phase mediators in dairy cows after parturition and warrants further research into the mechanisms behind these effects.