The objective of Exp. 1 was to compare the effects of virginiamycin (VM; 0, 175, or 250 mg x animal(-1) x d(-1)) and monensin/tylosin (MT; 250/ 90 mg x animal(-1) x d(-1)) on ruminal fermentation products and microbial populations in cattle during adaptation to an all-concentrate diet. Four ruminally cannulated, Holstein steers were used in a 4x4 Williams square design with 21-d periods. Steers were stepped up to an all-concentrate diet fed at 2.5% of BW once daily. Ruminal pH, protozoal counts, and NH3-N and VFA concentrations generally were unaffected by VM or MT. Mean counts of Lactobacillus and Streptococcus bovis were lower (P<.05) for VM-treated compared with control or MT-treated steers. Both VM and MT prevented the increase in Fusobacterium necrophorum counts associated with increasing intake of the high-concentrate diet observed in the control. The objective of Exp. 2 was to compare the effects of VM and MT on ruminal pH, L(+) lactate and VFA concentrations, and F. necrophorum numbers during carbohydrate overload. Six ruminally cannulated Holstein steers were assigned randomly to either the control, VM (175 mg/d), or MT (250 + 90 mg/d) treatments. Acidosis was induced with intraruminal administration of a slurry of ground corn and corn starch. The VM and MT premixes were added directly to the slurry before administration. Carbohydrate challenge induced acute ruminal acidosis (pH was 4.36 and L (+) lactate was 19.4 mM) in controls by 36 h. Compared with the controls, steers receiving VM or MT had higher (P<.05) ruminal pH, and the VM group had a lower (P<.05) L (+) lactate concentration. Fusobacterium necrophorum numbers initially increased in VM- and MT-administered steers. In the control steers, F. necrophorum was undetectable by 36 h. Virginiamycin seemed to control the growth of ruminal lactic acid-producing bacteria and, therefore, has the potential to moderate ruminal fermentation in situations that could lead to rapid production of lactic acid.
Twelve dual-flow continuous culture fermenters (1.95 L) were used to evaluate the effect of a phytogenic feed additive (Actifor Pro, Delacon, Engerwitzdorf, Austria; ACT) on ruminal fermentation and methane production when fed high fiber diets, comprised of bermudagrass hay (BGH) with or without corn gluten feed (CGF). Fermenters were utilized in a generalized randomized block design with a 2 × 2 factorial arrangement of treatments (n = 6): 1) diet (with or without CGF at 22% of diet DM) and 2) additive (with or without ACT at 1.0 g/L ACT). Two 10-d periods were conducted. Overall, comparing to no CGF, supplementation with CGF resulted in lower dry matter, organic matter, crude protein digestibility, microbial efficiency of nitrogen utilization, and methane production (mL of CH4/mol of total VFA), but increased neutral detergent fiber digestibility (all P ≤ 0.05). Diet × additive interactions were observed for molar proportion of acetate and propionate, and acetate-to-propionate ratio (A:P, all interactions P < 0.05), where inclusion of ACT increased acetate molar proportion and A:P (both P < 0.05), and decreased propionate molar proportion in diets with CGF (P = 0.05). A diet × additive interaction was also observed for methane production (ml of CH4/mol of total VFA; P = 0.08), where ACT decreased CH4 production per mol of VFA by 42% (P = 0.04), when only BGH was fed to the fermenters. In conclusion, CGF supplementation in BGH diets reduced methane production and improved fiber digestibility. The decrease in methane production per mol of VFA observed with ACT in the BGH without CGF diet warrants further investigation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.