This study compared standard finishing diets with or without tylosin phosphate at an industry standard roughage concentration, as well as titrated roughage concentrations in finishing diets ...containing no tylosin.
Beef steers (initial BW = 387 ± 14.2 kg; n = 3,340) were used in a randomized complete block design with 12 pens/treatment and 65 or 70 steers per pen. Dietary treatments were (1) 7.0% corn stalks with tylosin (7TYL), (2) 7.0% corn stalks without tylosin (7NT), (3) 13.0% corn stalks without tylosin (13NT), or (4) 19.0% corn stalks without tylosin (19NT). Corn stalks replaced steam-flaked corn on a DM basis.
Increased corn stalks linearly increased DMI. Increased corn stalks linearly reduced final BW and ADG, and resulted in poorer G:F. Hot carcass weight was similar between 7TYL and 7NT; however, hot carcass weight (HCW) linearly decreased as corn stalk inclusion increased. Tylosin inclusion resulted in a 32% reduction in liver abscess prevalence (from 19% to 13%). Liver abscess prevalence decreased linearly with increased corn stalks; tylosin use reduced adhered livers, whereas increased corn stalks did not.
Replacing steamflaked corn with 13% or 19% inclusion of corn stalks in diets without tylosin phosphate could reduce liver abscess prevalence, but increased roughage may not decrease the severity of the liver abscesses. Importantly, decreased dietary energy density led to increased DMI and reduced HCW in cattle fed to the same days on feed.
Dietary mix and host species have both been shown to have a significant impact on rumen microbial diversity, enteric methane emission and animal performance. The goal of this study was to see how the ...roughage concentrate ratio 70:30 (Low concentrate; LC) vs 40:60 (High concentrate; HC) and the host species crossbred cattle vs buffalo affected rumen microbial diversity, enteric methane emissions and nutrient utilization. Dry matter intake (kg/d) and dry matter percent digestibility were considerably (p < 0.05) higher in the HC ration and buffalo compared to LC ration and crossbred cattle, respectively. Both dietary mix and host species had a substantial (p < 0.05) impact on intake of various nutrients, including organic matter (OM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF), and acid detergent fiber (ADF). Increased concentrate proportion in the ration improved nitrogen balance, resulting in increased average daily gain and considerably reduced methane (g/d) output (p < 0.05). Furthermore, 16S rRNA genes were sequenced using Oxford Nanopore Technology (ONT) and subsequently annotated using the Centrifuge workflow to uncover ruminal bacterial diversity. Firmicutes was considerably (p < 0.01) greater in the LC diet, whereas, Bacteroidetes was higher in the HC ration. Genus Prevotella dominated all rumen samples, and buffalo fed LC ration had significantly (p < 0.01) higher Oscillospira abundance. At the species level, simple sugar-utilizing bacteria such as Prevotella spp. and Selenomonas ruminantium predominated in the crossbred cattle, but fibrolytic bacteria such as Oscillospira guilliermondii were statistically (p < 0.01) more abundant in the buffalo. Overall, dietary mix and host species have both been shown to have a significant impact on rumen microbial diversity, enteric methane emission and animal performance, however, host species remained a major driving force to change ruminal community composition as compared to roughage concentrate ratio under similar environmental conditions.
We evaluated the effects of dietary NDF concentration from alfalfa hay and bulk density of steam- flaked corn (SFC) on growth performance, carcass characteristics, and liver abscesses in finishing ...beef steers.
Crossbred beef steers (n = 214; 60 pens; initial BW = 417 ± 11.9 kg) were blocked by BW and assigned randomly to treatments and fed an average of 112 d. The treatments were arranged as a 2 × 3 factorial with 10 pens per treatment and consisted of 3 NDF concentrations from alfalfa hay (3%, 4.5%, or 6%) and 309 g/L (24 lb/bu) or 412 g/L (32 lb/bu) SFC (69% or 33% starch availability, respectively). Growth performance and carcass data were analyzed with PROC MIXED of SAS with pen as the experimental unit. Quality grades and liver scores were analyzed as binomial proportions using PROC GLIMMIX. Contrast statements were used to separate linear and quadratic effects of increasing roughage NDF.
Dry matter intake responded quadratically from d 0 to 35 as roughage NDF increased from 3% to 6%, and DMI increased linearly as roughage NDF increased on d 70 to 105 and d 0 to final. Otherwise, no differences in growth performance were noted. Marbling score responded quadratically to roughage level and was greater for steers fed 3% than for those fed 4.5% or 6% roughage NDF. Steers fed 309 g/L SFC tended to have a larger LM area than those fed 412 g/L SFC. The total percentage of abscessed livers at slaughter decreased linearly as roughage NDF was increased from 3% to 6% of DM as did the presence of A+ abscesses. In addition, total liver abscesses were 13.9 percentage points less in steers fed 412 versus 309 g/L SFC.
Results suggest that increasing roughage NDF and bulk density of SFC are dietary strategies that can decrease the presence of liver abscesses at slaughter without negatively affecting growth performance.
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