Withdrawal of sodium monensin when associated with virginiamycin during adaptation and finishing periods on feedlot performance, feeding behavior, carcass, rumen, and cecum morphometrics characteristics of Nellore cattle

Abstract

Feed additives such as monensin (MON) and virginiamycin (VM) are widely used in feedlots diets to maximize rumen fermentation. However, the knowledge about the effects of MON and VM combinations in specifics feedlot periods and the benefits of this association are still unclear. This study aimed to evaluate the effects of withdrawal of MON when associated with VM during the adaptation and finishing periods on feedlot performance of Nellore cattle. The experiment was designed as a completely randomized block replicated six times (four animals/pen) in which 120 Nellore bulls (378.4 ± 24.4 kg) were allocated in 30 pens and fed for 112 days according to the following treatments: (T1) MON during the entire feeding period; (T2) VM during the entire feeding period; (T3) MON+VM during the adaptation period and only VM during the finishing period 1 and 2; (T4) MON+VM during the entire feeding period; (T5) MON+VM during the adaptation and finishing period 1 and only VM during the finishing period 2. After 112 days on feed, no treatment effect was observed for DMI (P ≥ 0.12). However, bulls fed T5 had greater (P = 0.05) final BW and ADG when compared to T1, T2, and T4. Cattle from T3 and T5 groups presented heavier HCW (P = 0.05) than that fed T1, T2, and T4. Nellore bulls fed T1 and T5 had lower (P < 0.01) DMI variation than those receiving T2. The withdrawal of MON when associated with VM during the final third of the feedlot period improved overall final BW, ADG, and HCW when compared to bulls fed either MON or VM, but did not positively impact feedlot performance when compared to cattle that had MON withdrawn at the end of the adaptation period.

Strategies of virginiamycin supplementation in the postweaning phase on growth performance and carcass quality of beef cattle

“…Possibly, the presence of VM facilitated the growth of Gram-negative bacteria, which represent to the main trophic group of non-ber carbohydrate degraders (Maciel et al, 2015). This microbial group is predominant in diets with high starch contents (see TMR with approximately 50% corn grain), and therefore, the residual effect of postweaning supplementation with VM is related to a more e cient adaptation of the ruminal microbiota to the feedlot diet (Rigueiro et al, 2023).…”

“…Several studies have evaluated the effects of VM addition in feedlot cattle feed on animal performance, pointing to positive impacts on growth performance and preventing liver abscesses (Tedeschi and Gorocica-Buen l, 2018). Additionally, the association between VM and MO can be strategically used in cattle nishing, improving energy use e ciency, weight gain, and carcass traits in relation to diets with only MO (Benatti et al, 2017;Rigueiro et al, 2020Rigueiro et al, , 2023. In grazing systems with tropical forages, the bene ts of additives are mainly related to energy loss reduction due to enteric methane release depletion (Fonseca et al, 2019).…”

Impact of combined management strategies of monensin and virginiamycin in high energy diets on ruminal fermentation and nutrients utilization

“…Despite these studies evaluating the combination of MON and VM in feedlot diets, none of them specifically addressed the combination of two feed additives in specifics periods. In this context, the present study forms part of a larger research effort by this research group, evaluating the effects of different combinations of MON and VM at specific feedlot periods ( 10 , 11 , 23 , 24 ). Rigueiro et al ( 10 ) and Squizatti et al ( 24 ) investigated various combinations of MON and VM throughout the adaptation and finishing stages of feedlot Nellore cattle.…”

“…Based on these findings, we hypothesized that the withdrawal of MON, when combined with VM and a higher-energy diet during the final third of the feedlot period, would enhance DMI and improve ruminal fermentation and nutrient digestibility. Subsequently, Rigueiro et al ( 23 ) conducted a performance trail and found that withdrawing MON in conjunction with VM, alongside a higher energy diet, during the last 40 days of the feedlot period led to enhanced final body weight (BW), average daily gain (ADG) and hot carcass weight (HCW) in Nellore cattle compared to those fed either MON or VM alone.…”

“…Consequently, it was hypothesized that the withdrawal of MON, when associated with VM, combined with a higher energy diet during the final third of the feedlot period would enhance ruminal fermentation and nutrient digestibility in Nellore cattle. Therefore, the present study encompasses the metabolism assay linked with the performance trial conducted by Rigueiro et al ( 23 ). Thus, this study was designed to evaluate the effects of withdrawal of MON when associated with VM during the adaptation and finishing periods on ruminal metabolism, feeding behavior, and nutrient digestibility in Nellore cattle.…”