Subacute rumen acidosis is thought to be a common condition in early lactating dairy cattle; however, diagnosis is difficult. There are currently only two techniques available for measuring rumen pH under field conditions: rumenocentesis and oral stomach tube. Sixteen rumen-fistulated cows were sampled in four sites of the rumen (cranial-ventral, caudal-ventral, central, and cranial-dorsal) with a rumen cannula. Rumen pH results were compared to those obtained at the same time with rumenocentesis and with an oro-ruminal (Geishauser) probe. Rumen fluid was obtained between 6 and 12 wk of lactation. Samples were analyzed for pH, lactate, bicarbonate, sodium, potassium, and chloride. Rumen pH results were also compared to those obtained from 24-h continuous rumen pH measurement using indwelling rumen pH probes. Oro-ruminal probe samples had the highest pH values and the highest bicarbonate concentrations. Rumenocentesis samples had the lowest pH values and the lowest bicarbonate concentrations. Small differences in electrolyte concentrations were noted among rumen fluid collection techniques in the different rumen sites. The highest correlations of rumen pH were obtained between rumenocentesis and rumen cannulation (cranial-ventral), and between rumen cannulation (cranial-ventral) and the 24-h indwelling pH meter. Compared with samples obtained from the cranial-ventral rumen, rumenocentesis was more sensitive than the oro-ruminal probe in the measurement of low rumen pH; both techniques were moderately specific. The most accurate field technique was rumenocentesis. Improved field techniques are required for better on-farm diagnosis of subacute rumen acidosis.

The objective of this study was to determine the longterm effects of feeding monensin on methane (CH 4 ) production in lactating dairy cows. Twenty-four lactating Holstein dairy cows (1.46 ± 0.17 parity; 620 ± 5.9 kg of live weight; 92.5 ± 2.62 d in milk) housed in a tie-stall facility were used in the study. The study was conducted as paired comparisons in a completely randomized design with repeated measurements in a color-coded, double-blind experiment. The cows were paired by parity and days in milk and allocated to 1 of 2 treatments: 1) the regular milking cow total mixed ration (TMR) with a forage-to-concentrate ratio of 60:40 (control TMR; placebo premix) vs. a medicated TMR (monensin TMR; regular TMR + 24 mg of Rumensin Premix/kg of dry matter) fed ad libitum. The animals were fed and milked twice daily (feeding at 0830 and 1300 h; milking at 0500 and 1500 h) and CH 4 production was measured prior to introducing the treatments and monthly thereafter for 6 mo using an open-circuit indirect calorimetry system. Monensin reduced CH 4 production by 7% (expressed as grams per day) and by 9% (expressed as grams per kilogram of body weight), which were sustained for 6 mo (mean, 458.7 vs. 428.7 ± 7.75 g/d and 0.738 vs. 0.675 ± 0.0141, control vs. monensin, respectively). Monensin reduced milk fat percentage by 9% (3.90 vs. 3.53 ± 0.098%, control vs. monensin, respectively) and reduced milk protein by 4% (3.37 vs. 3.23 ± 0.031%, control vs. monensin, respectively). Monensin did not affect the dry matter intake or milk yield of the cows. These results suggest that medicating a 60:40 forage-to-concentrate TMR with 24 mg of Rumensin Premix/kg of dry matter is a viable strategy for reducing CH 4 production in lactating Holstein dairy cows.

One hundred twenty-eight 64-kg crossbred barrows and gilts were administered either 0 or 20 ppm of Ractopamine (RAC) in a pelleted corn-soybean meal diet that contained either 17.5 or 19.6% CP. Carcass quality was evaluated after slaughter at 100 kg. Dietary protein levels produced few significant effects; therefore, data were pooled for analysis. Pigs fed RAC exhibited improvement in feed efficiency (P < .01), ADG (P < .01), and number of days to slaughter (P < .01). Pigs fed RAC had 1.8 mm less fat (P < .05) and 3.4 mm more lean (P < .01) at the grading probe site. Gilts had 4.9 mm less fat than barrows at the probe site (P < .01) and also yielded an estimated 4.1% more lean (P < .01). Trimmed loins and bellies of animals fed 20 ppm of RAC were 230 g heavier (P < .05) than those of animals fed the control diet. Trimmed loins from gilts were 260 g heavier (P < .05), whereas barrows produced bellies that were 490 g heavier (P < .05) than those of gilts. The yield of processed ham was greater from both pigs fed RAC (P < .01) and barrows (P < .05). Loins of pigs fed RAC had lower cooking loss (P < .05), greater Warner-Bratzler shear value (P < .05), and higher fragmentation index value (P < .01). Although effects of sex were similar to or greater than the effects of 20 ppm of RAC, these effects were additive.

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 purpose of this study was to identify factors at the quarter and cow level that determine whether a quarter remains infected after an intramammary challenge with Staphylococcus aureus Newbould 305. A total of 135 cows were studied. Information on animal characteristics, cow-conformation, cow somatic cell count (SCC), and bacteriology, blood vitamin E levels, serology for retro-viral infections, bovine leukocyte adhesion deficiency-carrier status, and the presence of bovine lymphocyte antigens class I alleles was collected on each animal. All quarters of all cows were then challenged with Staphylococcus aureus Newbould 305. The challenge with S. aureus Newbould 305 resulted in 28 cows (20.7%) that did not establish infection in any of the quarters, 21 (15.6%) cows had 1 quarter infected, 35 (25.9%) had 2 quarters infected, 24 (17.8%) had 3 quarters infected, and 27 (20.0%) had all quarters infected. A higher prechallenge SCC decreased the risk of infection. An infection with Corynebacterium bovis prior to challenge decreased the risk of S.aureus infection. Of the bovine lymphocyte antigen alleles, the presence of the W20A allele proved to be significantly associated with a decreased risk of infection. No other factors proved to be significant.