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Three experiments were conducted to examine the effects of an Aspergillus oryzae extract containing [alpha]-amylase activity on performance and carcass characteristics of finishing beef cattle. In Exp. 1, 120 crossbred steers were used in a randomized complete block design to evaluate the effects of roughage source (alfalfa hay vs. cottonseed hulls) and supplemental [alpha]-amylase at 950 dextrinizing units (DU)/kg of DM. Significant roughage source x [alpha]-amylase interactions (P < 0.05) were observed for performance. In steers fed cottonseed hulls, supplemental [alpha]-amylase increased ADG through d 28 and 112 and tended (P < 0.15) to increase ADG in all other periods. The increases in ADG were related to increased DMI and efficiency of gain during the initial 28-d period but were primarily related to increased DMI as the feeding period progressed. Supplemental [alpha]-amylase increased (P = 0.02) the LM area across both roughage sources. In Exp. 2, 96 crossbred heifers were used in a randomized complete block design with a 2 x 3 factorial arrangement of treatments to evaluate the effects of corn processing (dry cracked vs. high moisture) and supplemental [alpha]-amylase concentration (0, 580, or 1,160 DU/kg of DM). Alpha-amylase supplementation increased DMI (P = 0.05) and ADG (P = 0.03) during the initial 28 d on feed and carcass-adjusted ADG (P = 0.04) across corn processing methods. Longissimus muscle area was greatest (quadratic effect, P = 0.04), and yield grade was least (quadratic effect, P = 0.02) in heifers fed 580 DU of [alpha]-amylase/kg of DM across corn processing methods. In Exp. 3, 56 crossbred steers were used in a randomized complete block design to evaluate the effects of supplemental [alpha]-amylase (930 DU/kg of DM) on performance when DMI was restricted to yield a programmed ADG. Alphaamylase supplementation did not affect performance when DMI was restricted. We conclude that dietary [alpha]-amylase supplementation of finishing beef diets may result in increased ADG through increased DMI under certain dietary conditions and that further research is warranted to explain its mode of action and interactions with dietary ingredients. Key words: [alpha]-amylase, Aspergillus oryzae, beef cattle, feedlot

The objective of this meta-analysis was to quantify the potential of CH 4 -mitigating strategies in dairy cattle when accounting for the effects of treatment dose, dietary nutrient composition, and supplementation period. Data from 218 studies with dairy cattle published between 1963 to 2022 were reviewed. Individual CH 4 mitigation strategies selected for the analysis were algae (Asparagopsis spp.), 3-nitrooxypropanol, nitrate, lipids, plant secondary compounds, and direct-fed microbials (DFM). Response variables evaluated were daily CH 4 emission (g/d), CH 4 yield (g CH 4 /kg DMI), and CH 4 intensity (g CH 4 /kg milk yield [MY] and ECM). Relative mean difference between treatment and control means reported in the studies were calculated and used in the statistical analysis. Robust variance estimation method was used to analyze the effects of CH 4 mitigation strategies. Dose, forage-to-concentrate ratio (F:C), dietary concentrations of CP, ether extract (EE), NDF, ADF, and starch, and supplementation period were used as continuous explanatory variables. Data for algae supplementation were limited and responses to studied species were contrasting but, overall, Asparagopsis spp. effectively decreased daily CH 4 emission, CH 4 yield, and CH 4 intensities by 29.8 ± 4.6%, 23.0 ± 5.3%, 34.0 ± 4.3%, and 22.6 ± 7.3%, respectively. Supplementation of 3-nitrooxypropanol decreased daily CH 4 emission, yield, and intensity (per kg MY and ECM) by 28.2 ± 3.6%, 28.7 ± 2.8%, 29.2 ± 3.1%, and 31.8 ± 2.8%, respectively, compared with control. Decreasing dietary fiber (i.e., F:C, NDF, and ADF), whereas increasing dietary starch concentration increased the efficacy of 3-nitrooxypropanol at mitigating enteric CH 4 emission. Nitrate supplementation decreased CH 4 emission, yield, and intensity (per kg ECM) by 18.5% ± 1.9%, 17.6 ± 1.6%, and 13.0 ± 0.2%, respectively, compared with control. Efficacy of nitrate at mitigating enteric CH 4 yield and CH 4 intensity was positively associated with dose, and efficacy of nitrate at mitigating CH 4 yield was positively associated with dietary starch concentration. Lipid supplementation decreased CH 4 emission, yield, and intensities by up to 14.8 ± 2.3%, respectively, compared with control. Efficacy of lipids supplementation was positively associated with dietary EE, starch, and supplementation period, but negatively associated with dietary ADF concentration. Free oil supplementation tended to increase lipid efficacy by 31% at decreasing CH 4 emission, compared with control. Condensed tannins and plant-derived bioactive compounds decreased CH 4 yield by 11.3 ± 2.9% and 5.7 ± 2.5%, respectively, but oregano did not affect enteric CH 4 emission metrics in the current meta-analysis. Direct-fed microbials were not effective in mitigating enteric CH 4 emission variables. Data were limited to determine the effects of dietary nutrients and duration of supplementation on efficacy of Asparagopsis spp., plant secondary compounds and DFM. Overall, supplementation of the diet with Asparagopsis spp., 3-nitrooxypropanol, nitrate, and lipids were the most effective strategies for decreasing enteric CH 4 emission in dairy cattle. Variability in the efficacy of most CH 4 mitigation strategies can be partially explained by differences in treatment dose, dietary nutrient composition, and supplementation period. The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. [ABSTRACT FROM AUTHOR]