The objectives of this study were: 1) to determine the effect of providing additional prepartum concentrate on the occurrence and severity of ruminal acidosis (RA) and lactational performance during the periparturient period in primiparous cows; and 2) to characterize the occurrence and severity of RA during the periparturient period. We hypothesized that providing additional concentrate prepartum would reduce postpartum RA. Fourteen ruminally cannulated Holstein heifers were paired by expected calving date and body condition score. The heifers were assigned to 1 of 2 prepartum feeding regimens: 1) a control treatment consisting of a far-off diet (forage:concentrate, F:C = 80:20) fed from d -60 to d -25 and a close-up diet (F:C = 54:46) fed from d -24 until parturition; or 2) a high-concentrate (HC) feeding program consisting of 4 prepartum diets, HC-1 (F:C = 68:32) fed from d -60 to d -43, HC-2 (F:C = 60:40) fed from d -42 to d -25, HC-3 (F:C = 52:48) fed from d -24 to d -13, and HC-4 (F:C = 46:54) fed from d -12 until parturition. All cows received the same lactation diet postpartum. Ruminal pH was measured continuously from d -5 to d +5, and for 3 consecutive days starting on d +17 +/- 1.2, d +37 +/- 1.4, and d +58 +/- 1.5 relative to parturition using an indwelling ruminal pH system. Ruminal acidosis was considered to occur when ruminal pH was <5.8 (total RA). Ruminal acidosis was further partitioned into: 1) mild RA (5.8 > ruminal pH > 5.5), 2) moderate RA (5.5 > ruminal pH > 5.2), and 3) acute RA (ruminal pH < 5.2). Feeding additional concentrate prepartum did not reduce postpartum RA. In fact, cows fed the HC treatment had more daily episodes of acute RA than cows fed the control treatment. Day relative to parturition affected the occurrence and severity of RA; RA increased following parturition and was sustained thereafter. The DM intake during the last 5 d of gestation was lower for cows fed the HC treatment compared with cows fed the control treatment, but lactational performance was not affected. We conclude that, under the conditions imposed, feeding additional concentrate prepartum does not reduce postpartum RA. Furthermore, the incidence and severity of RA increases immediately postpartum, emphasizing the need to develop and implement feeding strategies that reduce this risk.
The objectives of this study were 1) to develop and evaluate the accuracy and precision of a new stand-alone submersible continuous ruminal pH measurement system called the Lethbridge Research Centre ruminal pH measurement system (LRCpH; Experiment 1); 2) to establish the accuracy and precision of a well-documented, previously used continuous indwelling ruminal pH system (CIpH) to ensure that the new system (LRCpH) was as accurate and precise as the previous system (CIpH; Experiment 2); and 3) to determine the required frequency for pH electrode standardization by comparing baseline millivolt readings of pH electrodes in pH buffers 4 and 7 after 0, 24, 48, and 72 h of ruminal incubation (Experiment 3). In Experiment 1, 6 pregnant Holstein heifers, 3 lactating, primiparous Holstein cows, and 2 Black Angus heifers were used. All experimental animals were fitted with permanent ruminal cannulas. In Experiment 2, the 3 cannulated, lactating, primiparous Holstein cows were used. In both experiments, ruminal pH was determined continuously using indwelling pH electrodes. Subsequently, mean pH values were then compared with ruminal pH values obtained using spot samples of ruminal fluid (MANpH) obtained at the same time. A correlation coefficient accounting for repeated measures was calculated and results were used to calculate the concordance correlation to examine the relationships between the LRCpH-derived values and MANpH, and the CIpH-derived values and MANpH. In Experiment 3, the 6 pregnant Holstein heifers were used along with 6 new submersible pH electrodes. In Experiments 1 and 2, the comparison of the LRCpH output (1- and 5-min averages) to MANpH had higher correlation coefficients after accounting for repeated measures (0.98 and 0.97 for 1- and 5-min averages, respectively) and concordance correlation coefficients (0.96 and 0.97 for 1- and 5-min averages, respectively) than the comparison of CIpH to MANpH (0.88 and 0.87, correlation coefficient and concordance correlation coefficient, respectively). The concordance correlation analysis indicated that the ruminal pH data for LRCpH (1- and 5-min averages) vs. MANpH had location shifts that were smaller than those of the CIpH vs. MANpH. However, the scale shift was similar between the LRCpH and the CIpH. The plotted data from both systems closely resembled the line y = x, indicating that both systems were accurate and precise. In Experiment 3, changes in baseline millivolt readings for pH readings after 24, 48, or 72 h of ruminal incubation were not significantly different than zero, indicating that daily standardization of new electrodes was not essential. Results from this study indicate that the LRCpH system can accurately and precisely measure ruminal pH; thus, it provides increased opportunity for researchers to measure ruminal pH and the occurrence of ruminal acidosis in unrestrained cattle.
The objective of this study was to investigate the effect of monensin (MN) and dietary soybean oil (SBO) on milk fat percentage and milk fatty acid (FA) profile. The study was conducted as a randomized complete block design with a 2 x 3 factorial treatment arrangement using 72 lactating multiparous Holstein dairy cows (138 +/- 24 d in milk). Treatments were [dry matter (DM) basis] as follows: 1) control total mixed ration (TMR, no MN) with no supplemental SBO; 2) MN-treated TMR (22 g of MN/kg of DM) with no supplemental SBO; 3) control TMR including 1.7% SBO; 4) MN-treated TMR including 1.7% SBO; 5) control TMR including 3.4% SBO; and 6) MN-treated TMR including 3.4% SBO. The TMR (% of DM; corn silage, 31.6%; haylage, 21.2%; hay, 4.2%; high-moisture corn, 18.8%; soy hulls, 3.3%; and protein supplement, 20.9%) was offered ad libitum. The experiment consisted of a 2-wk baseline, a 3-wk adaptation, and a 2-wk collection period. Monensin, SBO, and their interaction linearly reduced milk fat percentage. Cows receiving SBO with no added MN (treatments 3 and 5) had 4.5 and 14.2% decreases in milk fat percentage, respectively. Cows receiving SBO with added MN (treatments 4 and 6) had 16.5 and 35.1% decreases in milk fat percentage, respectively. However, the interaction effect of MN and SBO on fat yield was not significant. Monensin reduced milk fat yield by 6.6%. Soybean oil linearly reduced milk fat yield and protein percentage and linearly increased milk yield and milk protein yield. Monensin and SBO reduced 4% fat-corrected milk and had no effect on DM intake. Monensin interacted with SBO to linearly increase milk fat concentration (g/100 g of FA) of total trans-18:1 in milk fat including trans-6 to 8, trans-9, trans-10, trans-11, trans-12 18:1 and the concentration of total conjugated linoleic acid isomers including cis-9, trans-11 18:2; trans-9, cis-11 18:2; and trans-10, cis-12 18:2. Also, the interaction increased milk concentration of polyunsaturated fatty acids. Monensin and SBO linearly reduced, with no significant interaction, milk concentration (g/100 g of FA) of short- and medium-chain fatty acids (
The effects of a barley beef diet without (control) and with a yeast culture (YC) on rumen fermentation, in vivo diet digestibility, nitrogen retention, live-weight gain and food intake were evaluated using 13 Limousin × British Friesian bulls per treatment. The YC was composed of the yeast species Saccharomyces cerevisiae and its growth medium dried in such a manner that it maintained its fermentative capacity. The addition of YC significantly increased the concentration of acetate (P < 0·05) while propionate concentration tended to be higher for bulls given YC (P > 0·05). The acetate: propionate ratio remained unchanged. Concentration of total volatile fatty acid (VFA) was significantly higher in YC bulls compared with control bulls (P < 0·05). The in vitro studies using the Menke gas test confirmed these findings. Mean in vitro gas production in bulls receiving YC was lower than that in the controls (P < 0·05) and methane production was significantly reduced by the addition of YC after 12h (P < 0·01). Ruminal ammonia concentrations were not affected by treatment but ruminal pH was significantly depressed by the addition of YC (P < 0·05).Apparent digestibility of dry matter, organic matter, crude protein and neutral-detergent fibre were unaffected by treatment but tended to be higher with the control diet. Nitrogen retention was not affected by the addition of YC and mean values for allantoin excretion and plasma urea were similar.In a 28-week feeding trial, dry-matter intake was significantly greater for bulls given YC (5·55 kg/day) than for control bulls (5·32 kg/day, P < 0·05) but average daily gain, 1·55 and 1·58 kg/day for control and YC respectively, and food conversion efficiency were not improved significantly by YC (P > 0·05).
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.
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