This experiment investigated the effects of zilpaterol hydrochloride (ZH) and the steroidal implant Revalor-S (RS; 120 mg of trenbolone acetate and 24 mg of estradiol-17β) on finishing steer performance and the mRNA concentration of β-adrenergic receptors (β-AR) types I and II, and types I, IIA, and IIX myosin heavy chain (MHC) isoforms. A total of 2,279 feedlot steers weighing 426 ± 6.4 kg were administered no implant or RS on d 0, and fed 0 or 8.3 mg of ZH/kg of diet DM during the last 30 d with a 3-d withdrawal. Treatments were randomly assigned to 24 pens (n = 6 pens/treatment). At slaughter, semimembranosus muscle tissue was excised for RNA isolation from 4 carcasses per pen. No interactions were detected for any of the variables measured in the experiment. Administration of ZH during the last 30 d of the feeding period increased (P < 0.01) ADG, G:F, HCW, and LM area; decreased (P < 0.01) 12th-rib fat depth and marbling; and improved (P < 0.01) yield grade. Treatment had no effect on β1-AR mRNA levels, but there was an increase (P = 0.01) in β₂-AR mRNA levels due to ZH inclusion. Myosin heavy chain-I (MHC-I) mRNA levels were unaffected by treatment. For MHC-IIA mRNA concentrations, administration of RS tended (P = 0.08) to increase mRNA levels, whereas ZH feeding the last 30 d tended (P = 0.08) to decrease mRNA levels for this isoform of myosin. Feeding ZH the last 30 d before slaughter increased (P < 0.01) mRNA concentrations of MHC-IIX in semimembranosus muscle of steers. These data indicate the combined use of ZH and RS additively contributes to BW and carcass gain in finishing feedlot steers and decreases marbling scores and USDA quality grades. The LM area increased and fat thickness decreased. In addition, ZH feeding changes the mRNA levels of MHC isoforms to a faster, more glycolytic fiber type in bovine skeletal muscle. These changes in mRNA concentrations of MHC isoforms, due to ZH feeding, could be affecting skeletal muscle hypertrophy. Copyright © 2010. American Society of Animal Science .

Crossbred steers (n = 180; 230 ± 6 kg) were fed during a 56-d receiving period to determine if supplementing chromium (Cr; KemTRACE Chromium Propionate 0.04%, Kemin Industries) would improve feedlot performance and health of newly-received cattle. A completely randomized block design (36 pens; 9 pens/treatment; 5 steers/pen) was used. Chromium premixes were supplemented to add 0 (Con), 0.1, 0.2, or 0.3 mg/kg of Cr to the total diet on a DM basis. No differences were detected on d 0 or after the first 14 d on feed. From d 0 to d 28, DMI (P = 0.07) and ADG increased linearly (P = 0.04) as Cr concentrations increased. From d 0 to d 56, BW (P = 0.08) displayed a tendency to increase linearly, and consequently ADG and G:F increased linearly (P ≤ 0.05) as Cr concentrations increased. The number of steers treated at least once for respiratory symptoms tended (P = 0.07) to linearly decrease as Cr concentrations increased. Twenty additional steers (235 ± 4 kg) were fed 56 d to determine if supplementing Cr (Con or 0.2 mg/kg Cr) would alter the metabolic response of newly-received cattle to a lipopolysaccharide (LPS) challenge. Cattle were fitted with jugular catheters on d 52. On d 55, blood samples were collected at 0.5-h intervals from −2 to 8 h, and again at 24 h relative to a LPS challenge (0.5 μg/kg BW) at 0 h. Serum glucose, insulin, and NEFA concentrations were determined from blood samples. Steer BW was also measured at cannulation, and 24 h and 8 d post-LPS. Steer BW did not differ at cannulation (P = 0.37), but 24 h post-LPS, Cr-supplemented steers had lost less BW (P = 0.03). Pre-LPS glucose concentration did not differ (P = 0.97). Post-LPS, there was a time × treatment interaction (P < 0.01) such that glucose concentration peaked earlier (0.5 h) and at a greater concentrations in Cr-supplemented steers (P < 0.01). Insulin concentration did not differ between treatments pre- or post-LPS (P > 0.13). Concentration of NEFA did not differ pre-LPS (P = 0.54); but 0.5 h post-LPS Cr-treated steers produced a greater peak NEFA concentration (P < 0.04). Results of this study indicate that supplementation of Cr to the basal diet can have beneficial effects on the performance and health of newly-received steers. These data also suggest that supplementation of Cr attenuated BW loss and allowed for a quicker recovery after a LPS challenge. Copyright © 2012. American Society of Animal Science .

Our objectives were to evaluate the dose/payout pattern of trenbolone acetate (TBA) and estradiol-17β (E₂) implants and feeding of zilpaterol hydrochloride (ZH) on performance and carcass characteristics of finishing beef steers. A randomized complete block design was used with a 3 × 2 factorial arrangement of treatments. British × Continental steers (n = 168; initial BW = 362 kg) were blocked by BW and allotted randomly to 42 pens (7 pens/treatment; 6 pens/block; 4 steers/pen). The main effects of treatment were implant [no implant (NI); Revalor-S (REV-S; 120 mg of TBA + 24 mg of E₂); and Revalor-XS (REV-X; 200 mg of TBA + 40 mg of E₂)] and ZH (0 or 8.3 mg/kg of DM for 20 d with a 3-d withdrawal before slaughter). Blocks were split into 2 groups, and block groups were fed for either 153 or 174 d. No implant × ZH interactions were noted for cumulative performance data. Overall, shrunk final BW (567, 606, and 624 kg for NI, REV-S, and REV-X, respectively), ADG (1.25, 1.51, and 1.60 kg), and G:F (0.14, 0.16, and 0.17) increased (P < 0.05) as TBA and E₂ dose increased. Implanting increased (P < 0.05) DMI, but DMI did not differ (P > 0.10) between REV-S and REV-X (8.8 for NI vs. 9.4 kg/d for the 2 implants). From d 1 to 112 of the feeding period, implanting increased (P < 0.05) ADG and G:F, but REV-S and REV-X did not differ (P > 0.10). From d 112 to end, ADG increased by 19% (P < 0.05) and G:F was 18% greater (P < 0.05) for REV-X vs. REV-S. Carcass-adjusted final BW (29-kg difference), ADG (0.2-kg/d difference), and G:F (0.02 difference) were increased (P < 0.05) by ZH, but daily DMI was not affected by feeding ZH. Hot carcass weight was increased (P < 0.05) by ZH (19-kg difference) and implant, with REV-X resulting in the greatest response (HCW of 376 for NI vs. 404 and 419 kg for REV-S and REV-X, respectively; P < 0.05). An implant × ZH interaction (P = 0.05) occurred for dressing percent (DP). Without ZH, implanting increased DP, but DP did not differ (P > 0.10) between REV-X and REV-S. With ZH, REV-X increased (1.7%; P < 0.05) DP vs. NI and REV-S. Marbling score, 12th-rib fat, and KPH were not affected (P > 0.10) by implant or ZH. Overall, treatment increased steer performance and HCW in an additive fashion, suggesting different mechanisms of action for ZH and steroidal implants. In addition, a greater dose of TBA + E₂ and extended payout improved steer performance and HCW. Copyright © 2011. American Society of Animal Science .

As commercial fed cattle consume large amounts of concentrate feedstuffs, hindgut health can be challenged. The objective of this study was to evaluate the effects of a commercially available Bacillus feed additive on cattle health outcomes and cecal microbiota of fed cattle at the time of harvest. Commercial cattle from a single feedlot were identified for characterization of cecal microbial communities using 16S ribosomal ribonucleic acid gene sequencing. All cattle were fed a common corn-based finishing diet. Control cattle (CON) were administered no treatment while treated cattle (TRT) were supplemented daily with 0.050 g of MicroSaf 4C 40 (2 billion colony forming units of Bacillus spp.; Phileo by Lesaffre, Milwaukee, WI). Immediately after harvest and evisceration, the cecal contents of cattle were sampled. After DNA extraction, amplification, and sequencing, reads from CON samples (N = 12) and TRT samples (N = 12) were assigned taxonomy using the SILVA 138 database. Total morbidity, first treatment of atypical interstitial pneumonia, and early shipments for harvest were decreased among TRT cattle compared to CON cattle (P ≤ 0.021). On average, cecal microbiota from TRT cattle had greater alpha diversity than microbiota from CON cattle as measured by Shannon diversity, Pielou’s evenness, and feature richness (P < 0.010). Additionally, TRT microbial communities were different (P = 0.001) and less variable (P < 0.001) than CON microbial communities when evaluated by unweighted UniFrac distances. By relative abundance across all samples, the most prevalent phyla were Firmicutes (55.40%, SD = 15.97) and Bacteroidetes (28.17%, SD = 17.74) followed by Proteobacteria (6.75%, SD = 10.98), Spirochaetes (4.54%, SD = 4.85), and Euryarchaeota (1.77%, SD = 3.00). Spirochaetes relative abundance in TRT communities was greater than that in CON communities and was differentially abundant between treatments by ANCOM testing (W = 11); Monoglobaceae was the only family-level taxon identified as differentially abundant (W = 59; greater mean relative abundance in TRT group by 2.12 percentage points). Half (N = 6) of the CON samples clustered away from all other samples based on principal coordinates and represented cecal dysbiosis among CON cattle. The results of this study indicated that administering a four-species blend of Bacillus positively supported the cecal microbial communities of finishing cattle. Further research is needed to explore potential mechanisms of action of Bacillus DFM products in feedlot cattle. Microbes in the rumen break down fiber and complex nutrients into energy that cattle can absorb. Rumen microbes are becoming well studied, but the microbes of the hindgut—specifically of the cecum and large intestine—are less well-studied. As feedlot cattle eat large amounts of grain, maintaining health and balance of microbes in the hindgut is important. Overconsumption of a meal causes a greater proportion of digestion to occur in the hindgut, causing greater acid production that damages the gastrointestinal lining. If dietary microbial supplements support a more diverse microbial population, the challenges caused by greater hindgut digestion could be mitigated. To test this, cecal microbes were characterized after feedlot cattle were fed a conventional diet, with or without a supplement of Bacillus bacteria. Cecal samples from cattle that were fed Bacillus had greater microbial diversity. Approximately half of the cecal samples from cattle that were not fed Bacillus had disrupted microbial balance. Based on taxonomic assignment, bacteria observed in these disrupted samples indicated greater energy density of digesta and increased methane production. Supplementing feedlot cattle with Bacillus could improve hindgut microbial diversity.

Copyright © 2013. . © 2013 Johnson Ribeiro and Beckett

Crossbred steers (n = 20; 235 ± 4 kg) were fed for 53 d during a receiving period to determine if supplementing chromium (Cr; KemTRACE Chromium Propionate 0.04%, Kemin Industries, Des Moines, IA) would alter glucose or lipid metabolism of newly received cattle. Chromium premixes were supplemented to add 0 (Con) or 0.2 mg/kg of Cr to the total diet on a DM basis. Cattle were fitted with jugular catheters on d 52. A glucose tolerance test (GTT) and an insulin sensitivity test (IST) were conducted on d 53. Blood samples were collected from –60 to 150 min relative to each infusion. Serum was isolated to determine glucose, insulin, and NEFA concentrations. Throughout GTT, no differences were detected in glucose concentrations, glucose clearance rates (k), or preinfusion insulin concentrations (P > 0.50), but insulin concentrations postinfusion tended (P = 0.06) to be greater for the Cr-supplemented steers. This caused an increase in the insulin to glucose ratio (I:G) from 0 to 150 min postinfusion for the Cr-supplemented steers (P = 0.03). In addition, NEFA concentrations during GTT were lower (P ≤ 0.01) for Cr-supplemented steers both preinfusion and postinfusion. During IST, there was no treatment effect on glucose concentrations preinfusion (P = 0.38), but postinfusion glucose concentrations were greater (P< 0.01) in the Cr-supplemented steers. The k of Cr-supplemented steers tended (P = 0.06) to be faster than Con steers from 30 to 45 min postinfusion. During the same test, there was no treatment effect detected for insulin concentrations (P > 0.33). The I:G were not affected by treatment (P > 0.40).Concentrations of NEFA were reduced (P < 0.01) both preinfusion and postinfusion during IST for Cr-supplemented steers. Results of this study indicate that supplementation of Cr can significantly alter lipid metabolism. This suggests that these steers had less dependence on lipid metabolism for energy or sensitivity of adipose tissue to antilipolytic signals was reduced. Results of glucose and insulin metabolism were inconsistently modified after a GTT and an IST. Copyright © 2013. American Society of Animal Science .