Effects of 2-hydroxy-4-(methylthio)-butanoic acid on performance and carcass characteristics of finishing beef cattle and on fermentation in continuous culture1

Abstract

Three experiments were conducted to evaluate the effects of feeding 2-hydroxy-4- (methylthio)-butanoic acid (HMTBA) on performance and carcass characteristics of feedlot cattle and on microbial fermentation in a continuous-culture system. In Exp. 1, 160 crossbred steers (initial BW = 385 +/- 10.3 kg) were assigned to 4 treatments consisting of control (0% HMTBA) or 3 diets containing HMTBA (0.069, 0.137, and 0.204%; DM basis) in a randomized complete block design. As the percent of HMTBA increased in the diet, final BW (P = 0.069), final BW adjusted to a constant dressing percent (P = 0.063), and overall ADG (P = 0.099) tended to decrease linearly. Overall DMI decreased linearly (P < or = 0.006) with increasing HMTBA dose. No differences (P > or = 0.10) were noted for carcass characteristics, except for a tendency (P = 0.078) for a linear increase in the percentage of cattle grading USDA Choice with increasing HMTBA dose. In Exp. 2, 80 crossbred steers (initial BW = 450 +/- 17 kg) in a randomized complete block design were assigned to a control (0% HMTBA) diet or to a diet in which the concentrations of HMTBA were gradually increased from 0.036 to 0.212% of DM over a 50-d period. The HMTBA-containing diet tended to decrease DMI (P = 0.132), but G:F (P = 0.319) for the overall feeding period, carcass measurements, and USDA quality grade (P > or = 0.149) did not differ between treatments. In Exp. 3, continuous culture fermenters (n = 5/treatment) were used to determine the effects of HMTBA (control vs. 0.24% HMTBA) on microbial fermentation. No differences (P > or = 0.31) were detected between treatments in ruminal OM digestibility, microbial N synthesis, pH, ammonia, molar proportions of VFA, or effluent concentration of selected long-chain fatty acids. These results suggest that HMTBA decreased DMI by feedlot steers fed a steam-flaked corn-based diet in a dose-dependent manner; however, gradually increasing the dose over time seemed to moderate effects on DMI. No major changes in microbial fermentation in continuous culture were observed with HMTBA at 0.24% of dietary DM, suggesting effects of HMTBA on DMI were not likely associated with changes in ruminal digestion or fermentation.

2-Hydroxy-4-(Methylthio) Butanoic Acid Isopropyl Ester Supplementation Altered Ruminal and Cecal Bacterial Composition and Improved Growth Performance of Finishing Beef Cattle

“…The impact of HMBi or HMB supplementation on VFA production in the rumen was variable in vitro or in vivo , in which several studies have shown positive effects ( 7 , 31 ). Whereas, most studies did not observe any effect of Met analog supplementation on VFA concentrations or profiles, which was consistent with the current study ( 32 , 33 ). The discrepancy of the effect of HMBi on the ruminal microbes may be explained by the increased bacterial N derived from NH 3 -N, peptides N, and AA but decreased the production of acetate, propionate, and total VFA because a fraction of carbon was being used for AA synthesis ( 8 ).…”

Effects of addition of Aspergillus oryzae culture and 2‐hydroxyl‐4‐(methylthio) butanoic acid on milk performance and rumen fermentation of dairy cows

“…It was observed that responses of HMB (40‐50% protection of rumen degradation) on rumen fermentation were variable. The rumen volatile fatty acid (VFA) proportion was not influenced by added HMB in some studies (Vázquez‐Añón et al ; Wilson et al ), while the change in rumen VFA profile was observed in other studies (Noftsger et al ; Chung et al ).…”

Effects of Aspergillus Oryzae Culture and 2-Hydroxy-4-(Methylthio)-Butanoic Acid on In vitro Rumen Fermentation and Microbial Populations between Different Roughage Sources

“…However, the impact of HMB on rumen fermentation seems highly variable and remains unclear. Although addition of HMB improved microbial protein synthesis (Vázquez-Añón et al, 2001), some researchers found no changes in volatile fatty acid (VFA) proportions by HMB (Vázquez-Añón et al, 2001; Wilson et al, 2008), whereas others reported changes in VFA profile (Noftsger et al, 2003; Chung et al, 2006). In addition, the mechanisms by which HMB could impact microbial digestion in the rumen are not yet clear.…”