No abstract

This study examined how different methods of applying a fibrolytic enzyme or ammonia affect the nutritive value of Bermudagrass hay and the performance of beef cattle. Fifty Angus x Brangus crossbred steers (mean initial BW 244 +/- 26 kg) were individually fed for ad libitum intake of a 5-wk regrowth of a mixture of Florakirk and Tifton 44 Bermudagrass [Cynodon dactylon (L.) Pers] hay for 84 d with a concentrate supplement (77% soybean hull pellets, 23% cottonseed meal (DM basis) fed at 1% of BW daily. The Bermudagrass was conserved as hay without treatment (control), with NH(3) (30 g/kg of DM), or with a fibrolytic enzyme (16.5 g/t, air-dry basis) that was applied immediately after cutting (Ec), at baling (Eb), or at feeding. Chromic oxide was dosed to steers for 10 consecutive days, and fecal Cr concentrations from the last 5 d were used to estimate apparent total tract digestibility. In situ ruminal DM degradability was measured by incubating ground (4-mm) hay samples in duplicate in each of 2 ruminally cannulated cows having ad libitum access to Bermudagrass hay and 500 g/d of soybean meal. Unlike the enzyme treatment, ammoniation increased (P < 0.001) the CP concentration and reduced (P < 0.001) NDF, hemicellulose, and lignin concentrations of hay. Total DMI was greater (P < 0.05) for steers fed hays treated with Ec or NH(3) than for those fed control hays. All additive treatments increased (P < 0.05) DM digestibility, and NH(3), Ec, and Eb treatments also increased (P < 0.01) NDF digestibility. The initial and final BW, ADG, BCS, G:F, and hip height of the steers were not affected (P > 0.05) by treatment. The wash loss fractions in hays treated with Ec and Eb were lower than that in the control hay, but the potentially degradable fraction, total degradable fraction, and the effective degradability were increased (P < 0.01) by NH(3) treatment. Application at cutting was the most promising method of enzyme treatment, and this treatment was almost as effective as ammonia for enhancing forage quality.

No abstract

The objectives of this study were to examine the relationship between residual feed intake (RFI) and DM and nutrient digestibility, in vitro methane production, and volatile fatty acid (VFA) concentrations in growing beef cattle. Residual feed intake was measured in growing Santa Gertrudis steers (Study 1; n = 57; initial BW = 291.1 ± 33.8 kg) and Brangus heifers (Study 2; n = 468; initial BW = 271.4 ± 26.1 kg) fed a high-roughage-based diet (ME = 2.1 Mcal/kg DM) for 70 d in a Calan-gate feeding barn. Animals were ranked by RFI based on performance and feed intake measured from day 0 to 70 (Study 1) or day 56 (Study 2) of the trial, and 20 animals with the lowest and highest RFI were identified for subsequent collections of fecal and feed refusal samples for DM and nutrient digestibility analysis. In Study 2, rumen fluid and feces were collected for in vitro methane-producing activity (MPA) and VFA analysis in trials 2, 3, and 4. Residual feed intake classification did not affect BW or BW gain (P &gt; 0.05), but low-RFI steers and heifers both consumed 19% less (P &lt; 0.01) DMI compared with high-RFI animals. Steers with low RFI tended (P &lt; 0.1) to have higher DM digestibility (DMD) compared with high-RFI steers (70.3 vs. 66.5 ± 1.6% DM). Heifers with low RFI had 4% higher DMD (76.3 vs. 73.3 ± 1.0% DM) and 4 to 5% higher (P &lt; 0.01) CP, NDF, and ADF digestibility compared with heifers with high RFI. Low-RFI heifers emitted 14% less (P &lt; 0.01) methane (% GE intake; GEI) calculated according to Blaxter and Clapperton (1965) as modified by Wilkerson et al. (1995), and tended (P = 0.09) to have a higher rumen acetate:propionate ratio than heifers with high RFI (GEI = 5.58 vs. 6.51 ± 0.08%; A:P ratio = 5.02 vs. 4.82 ± 0.14%). Stepwise regression analysis revealed that apparent nutrient digestibilities (DMD and NDF digestibility) for Study 1 and Study 2 accounted for an additional 8 and 6%, respectively, of the variation in intake unaccounted for by ADG and mid-test BW0.75. When DMD, NDF digestibility, and total ruminal VFA were added to the base model for Study 2, trials 2, 3, and 4, the R2 increased from 0.33 to 0.47, explaining an additional 15% of the variation in DMI unrelated to growth and body size. On the basis of the results of these studies, differences in observed phenotypic RFI in growing beef animals may be a result of inter-animal variation in apparent nutrient digestibility and ruminal VFA concentrations.

Campylobacter are important human foodborne pathogens known to colonize the gastrointestinal tract of cattle. The incidence of Campylobacter in cattle may be seasonal and may vary among age groups and type (beef versus dairy). Less is known about other factors that could influence the prevalence, colonization site, and shedding of Campylobacter in cattle. The objectives of this study were to evaluate the prevalence and enumerate Campylobacter at two sites along the digestive tract of beef and dairy type cattle consuming either grass or feedlot diets. In an initial study, Campylobacter was not recovered from rumen samples of any of 10 ruminally cannulated (six dairy and four beef type) pasture-reared cattle and there was no difference (p > 0.05) between cattle types on fecal Campylobacter recovery, with 50% of each type yielding culture-positive feces (overall mean +/- SE, 0.75 +/- 0.001 SEM log(10) colony-forming units [CFU]/g feces). When calculated from Campylobacter culture-positive animals only, mean fecal concentrations were 1.50 +/- 0.001 SEM log(10) CFU/g. In a follow-up study with feedlot and pasture-reared cattle (n = 18 head each), 78% of rumen and 94% of fecal samples from pastured cattle were positive for Campylobacter while 50% of the rumen and 72% of the fecal samples were positive in concentrate-fed animals. Overall mean concentration of Campylobacter was greater in feces than ruminal fluid (p < 0.05). When only Campylobacter-positive animals were analyzed, concentrations recovered from feces were higher (p < 0.05) in concentrate-fed than in pasture-fed cattle (4.29 vs. 3.34 log(10) CFU/g, respectively; SEM = 0.29). Our results suggest that the rumen environment and its microbial population are less favorable for the growth of Campylobacter and that concentrate diets may provide a more hospitable lower gastrointestinal tract for Campylobacter.