The Potential of Shortening the Adaptation of Nellore Cattle to High-Concentrate Diets Using Only Virginiamycin as Sole Feed Additive

Abstract

Feedlot cattle are usually adapted to high-concentrate diets containing sodium monensin (MON) in more than 14 days. However, for finishing diets with lower energy content, the use of MON during adaptation may hold dry matter intake (DMI), and virginiamycin (VM) may be an alternative. This study was designed to determine the potential of shortening the adaptation of Nellore cattle to high-concentrate diets using only VM as a sole feed additive relative to feedlot performance, feeding behavior, and ruminal and cecum morphometrics. The experiment was designed as a completely randomized block replicated six times (four animals/pen) in which 120 Nellore bulls (390.4 ± 19.0 kg) were fed in 30 pens for 111 days according to the following treatments: (1) MON and adaptation for 14 days (MON14), (2) MON + VM and adaptation for 14 days (MONVM14), (3) VM and adaptation for 14 days (VM14), (4) VM and adaptation for 9 days (VM9), and (5) VM and adaptation for 6 days (VM6). At the end of the adaptation, 30 animals (n = 1 per pen) were randomly slaughtered for rumen and cecum evaluations. The remaining 90 bulls were harvested at the end of the study. No effects of treatments were observed (P < 0.10) for final body weight, average daily gain (ADG), and hot carcass weight (HCW). Cattle fed VM14 presented a greater (P ≤ 0.03) DMI, expressed as percent of body weight (BW), than animals fed either MON14 or MONVM14; however, cattle fed either MON14 or MONVM14 improved (P ≤ 0.02) the gain-to-feed ratio (G/F) by 10.4 or 8.1%, respectively, when compared to bulls fed VM14. Bulls fed VM14 had smaller (P < 0.05) papillae area (0.34 vs. 0.42 cm2) and rumen absorptive surface area (28.9 vs. 33.8 cm2) than those fed MON14. The shortening of the adaptation period linearly decreased the 12th rib fat (P = 0.02) and biceps femoris fat daily gain (P = 0.02) of Nellore bulls fed only VM, which linearly decreased the final biceps femoris fat thickness (P < 0.01). Feedlot cattle fed VM as a sole feed additive should not be adapted to high-concentrate diets in less than 14 days. Regardless of either adaptation length or feed additive, feedlot cattle need at least 14 days to adapt to finishing diets.

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

“…In the present study, there were no effects of treatments on DMI, expressed both in kg and as a percentage of BW, in the first 28 days on feed. Based on results described by Rigueiro et al ( 8 ), where Nellore bulls fed VM as the sole feed additive during adaptation reached a DMI of 2% of the initial BW in 4.3 days on average, whereas those fed MON needed 20.7 days to reach a similar intake, another study of this research group was developed by Rigueiro et al ( 9 ) where it was hypothesized that the adaptation period could be shortened to 9 days or even 6 days when VM (25 mg/kg DM) is used in finishing diets of Nellore cattle as the sole feed additive. The authors reported that, during the first 28 days on feed, the DMI decreased linearly as the adaptation was shortened for the cattle fed VM as a sole feed additive, where cattle fed VM for 14 days presented a greater DMI, expressed as % of BW, than animals fed either MON or MON+VM for 14 days.…”

“…It was recommended by the authors that Nellore yearling bulls should be fed with diets containing MON and VM only during the adaptation period, and VM during the finishing period to improve overall feedlot performance. In a subsequent study, Rigueiro et al ( 9 ) reported again that the use of MON and VM associated for the entire feeding period did not promote any positive effect on feedlot performance when compared to cattle fed only MON or VM. Furthermore, Rigueiro et al ( 8 , 9 ) observed that cattle fed only VM did not decrease DMI in the last 28 days on feed.…”

“…In a subsequent study, Rigueiro et al ( 9 ) reported again that the use of MON and VM associated for the entire feeding period did not promote any positive effect on feedlot performance when compared to cattle fed only MON or VM. Furthermore, Rigueiro et al ( 8 , 9 ) observed that cattle fed only VM did not decrease DMI in the last 28 days on feed.…”

Comparing Blend of Essential Oils Plus 25-Hydroxy-Vit-D3 Versus Monensin Plus Virginiamycin Combination in Finishing Feedlot Cattle: Growth Performance, Dietary Energetics, and Carcass Traits

“…When supplemented alone, MON decreases DM intake by an average of 3.1% [36], whereas VM supplementation alone does not reduce DMI [37]. There are few reports evaluating the effects of MON + VM combination on cattle growth performance.…”

“…Except for Rigueiro et al [37], the majority of studies reported enhancements in daily gain and gain efficiency for the combination of MON + VM than when supplemented separately [3]. The positive effects of MON and VM on energetic efficiency in ruminants have been extensively studied.…”