Forty-eight bulls (335 +/- 8.6 kg of initial BW) were randomly assigned to 4 glycerin levels (0, 4, 8, and 12% of concentrate DM) with the objective of evaluating the effects of glycerin supplementation on performance, ruminal fermentation, metabolism, and carcass and meat quality in Holstein bulls fed high-concentrate diets. Concentrates were formulated to be isonitrogenous and isocaloric (assuming a glycerin ME content of 3.47 Mcal/kg of DM). Concentrate and straw were fed for ad libitum intake. Bull BW and feed consumption were recorded monthly. Additionally, rumen and blood samples were collected every month. Bulls were slaughtered after 91 d of study (460 +/- 11 kg of final BW). Hot carcass weight, carcass backfat, and conformation were recorded. The area, Warner-Bratzler shear force, and intramuscular fat content of LM were determined. Glycerin level did not affect daily concentrate intake (6.89 +/- 0.34 kg/d of DM), straw intake (1.38 +/- 0.069 kg/d of DM), total DMI (8.27 +/- 0.32 kg/d of DM), ADG (1.36 +/- 0.087 kg/d), or G:F (0.17 +/- 0.009). Similarly, rumen molar proportions of propionic, acetic, and butyric acids, and rumen liquid osmolality were unaffected by treatment. However, a decreased rumen pH (P < 0.05), and greater rumen total VFA concentration (P = 0.09), serum insulin concentration (P < 0.05), and insulin to glucose ratio (P < 0.05) were observed in bulls fed 8% glycerin in concentrate compared with those receiving 0, 4, or 12%. No changes were observed in carcass and meat quality. The ME content of glycerin (86% glycerol) can be assumed to be 3.47 Mcal/kg of DM in Holstein bulls fed high-concentrate diets. In addition, feeding concentrate containing up to 12.1% of glycerin does not lead to detrimental effects on performance, ruminal fermentation, metabolism, and carcass and meat quality variables.

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Eight dual-flow continuous culture fermenters (1400 ml) were used in two consecutive periods to study the effects of pH and pH fluctuations on microbial fermentation and nutrient flow. Fermenters were maintained at 39 degrees C, with solid and liquid dilution rates of 5 and 10%/h, respectively, and fed continuously a 60% alfalfa hay and 40% concentrate diet (18.9% crude protein, 36.6% neutral detergent fiber, 17.6% acid detergent fiber). Treatments were high pH (constant at 6.4); low pH (constant at 5.7); cycles of 4 h at pH 6.4 and 4 h at pH 5.7; and pH constant at 6.4, except for two 30-min drops per day to pH 5.7, followed by a 3-h slow recovery to pH 6.4. The low pH (constant at 5.7) produced lower apparent dry matter, neutral detergent fiber and acid detergent fiber digestion, lower total and branch-chained volatile fatty acid concentrations, and lower acetate and higher propionate proportions than high pH (constant at 6.4). There were no differences in these estimates between constant high pH and the two treatments that alternated high pH and low pH. The constant low pH reduced protein degradation and increased nonammonia N and dietary N flow compared with constant high pH. The pH treatments had no effect on bacterial N flow or efficiency of microbial protein synthesis. Flow of essential amino acids was highest for constant low pH and lowest for constant high pH. Results indicate that constant low pH reduced fiber and protein digestion and increased the flow of total and some individual amino acids. However, the effects of transitory decreases of pH were either small or insignificant with the conditions tested in this study.

To study the effects of an extract of plant flavonoids [Bioflavex (FL)] in cattle fed highconcentrate diets, 2 experiments were designed. In the first experiment, the effects of Bioflavex on the development of rumen acidosis was evaluated in 8 Holstein-Friesian crossbreed heifers (451 kg; SEM 14.3 kg of BW) using a crossover design. Each experimental period lasted 22 d; from d 1 to 20, the animals were fed rye grass, on d 21 the animals were fasted, and on d 22, rumen acidosis was induced by applying 5 kg of wheat without [Control: (CTR) heifers who did not receive Bioflavex] or with flavonoids [heifers who received FL; 300 mg/kg DM] through a rumen cannula. Rumen pH was recorded continuously (from d 19 to d 22). On d 22, average rumen pH was significantly (P < 0.01) higher in the FL animals (6.29; SEM = 0.031) than it was in the CTR heifers (5.98; SEM = 0.029). After the wheat application, the rumen VFA concentration increased (P < 0.01), the proportion of acetic acid decreased (P < 0.01), and lactate concentration (mmol/L) increased, but the increase was not as great (P = 0.09) in the FL as it was in the CTR heifers (0.41 to 1.35 mmol/L; SEM = 0.24). On d 22, Streptococcus bovis and Selenomonas ruminantium titers increased after the wheat application, but Megasphaera elsdenii titers increased (P < 0.05) only in the FL heifers. In the second experiment, the effect of Bioflavex on the performance and rumen fermentation in finishing heifers was evaluated. Forty-eight Fleckvieh heifers (initial BW = 317 kg; SEM = 5.34) were used in a completely randomized design. Heifers were assigned to 1 of 4 blocks based on their BW and, within each block, assigned to 1 of 2 pens (6 heifers/pen). In addition, 16 heifers (2/pen) were rumen cannulated. Individual BW and group consumption of concentrate and straw were recorded weekly until the animals reached the target slaughter weight. Supplementation with FL did not affect ADG, feed consumption, or feed conversion ratio. Rumen pH and molar proportions of propionate were greater (P < 0.01) and acetate proportion was less in the FL (P < 0.01) than they were in the CTR heifers. Flavonoid supplementation might be effective in improving rumen fermentation and reducing the incidence of rumen acidosis. This effect of flavonoids may be partially explained by increasing the numbers of lactateconsuming microorganisms (e.g., M. elsdenii) in the rumen.

A longitudinal study involving 73 primiparous (PP) and 47 multiparous (MP) Holstein cows was conducted over an 8-month period to assess the associations between locomotion score (LCS) and milk production, dry matter intake (DMI), feeding behaviour, and number of visits to an automatic milking system (AMS). Twice weekly, all cows were locomotion scored (scale 1-5) by the same observer. Individual eating behaviour and individual feed consumption at each cow visit to the feed troughs, individual milk production, the time of milking, and the number of milkings for each cow were recorded for the day of locomotion scoring and the day before and after. Dependent variables, such as milk yield, DMI, etc. were modelled using a mixed-effects model with parity, LCS, days in milk (DIM), the exponential of -0.05 DIM, and the interaction between parity and LCS, as fixed effects and random intercepts and random slopes for the linear and the exponential of -0.05DIM effects within cow. LCS did not affect time of attendance at feed troughs, but affected the location that cows occupied in the feed troughs. The time devoted to eating and DMI decreased with increasing LCS. Milk production decreased with LCS>3. The number of daily visits to the AMS also decreased with increasing LCS. The cows with high LCS were fetched more often than the cows with low LCS. Overall, PP cows were more sensitive to the effects of increasing LCS than were MP cows. The decrease in milk production observed with increasing LCS seemed to be affected similarly by the decrease in DMI and by the decrease in number of daily visits to the AMS. A further economic loss generated by lame cows with AMS will be associated with the additional labour needed to fetch them.

The objective was to evaluate whether the amount of concentrate offered in an automatic milking systems (AMS) would modify milking frequency, feeding behavior, and milk production. One hundred fifteen lactating cows were used in a cross-over design with 2 periods of 90 d each and 2 treatments: low concentrate (LC; up to 3 kg/d of concentrate at the AMS) or high concentrate (HC; up to 8 kg/d of concentrate at the AMS). Cows were evenly distributed in 2 symmetrical pens, each containing 1 AMS and about 50 cows at any given time. All cows received the same total ration (28% corn silage, 1.67 Mcal of net energy for lactation/kg, 16.5% crude protein, DM basis), but a different amount of concentrate from this ration was offered at the AMS depending on treatment. The concentrate at the AMS had the same composition in both treatments. Cows were fetched when time elapsed, because last milking was greater than 12 h. The amount of concentrate offered at the AMS was proportional to the time elapsed since last visit (125 and 333 g/h for LC and HC, respectively). Milk production, total number of daily milkings, number of cows fetched, or number of voluntary milkings were not affected by treatments. The consumption of basal ration was greater in LC than in HC, but this difference was compensated by a greater consumption of concentrate at the AMS in HC than LC cows. Total dry matter intake tended to be lower, therefore, in HC than in LC cows. Eating rate of the basal ration was greater in LC than in HC, but the total amount of time that cows devoted to eat was similar between treatments. Offering high amounts of concentrate to the AMS feeding a basal ration rich in corn silage did not diminish the need for fetching cows and did not increase the number of daily milkings nor milk production.