Feedlot performance and rumen morphometrics of Nellore cattle adapted to high-concentrate diets over periods of 6, 9, 14 and 21 days

Abstract

The energy content of finishing diets offered to feedlot cattle may vary across countries. We assumed that the lower is the energy content of the finishing diet, the shorter can be the adaptation period to high-concentrate diets without negatively impacting rumen health while still improving feedlot performance. This study was designed to determine the effects of adaptation periods of 6, 9, 14 and 21 days on feedlot performance, feeding behaviour, blood gas profile, carcass characteristics and rumen morphometrics of Nellore cattle. The experiment was designed as a completely randomised block, replicated 6 times, in which 96 20-month-old yearling Nellore bulls (391.1 ± 30.9 kg) were fed in 24 pens (4 animals/pen) according to the adaptation period adopted: 6, 9, 14 or 21 days. The adaptation diets contained 70%, 75% and 80.5% concentrate, and the finishing diet contained 86% concentrate. After adaptation, one animal per pen was slaughtered (n = 24) for rumen morphometric evaluations and the remaining 72 animals were harvested after 88 days on feed. Orthogonal contrasts were used to assess linear, quadratic and cubic relationships between days of adaptation and the dependent variable. Overall, as days of adaptation increased, final BW (P = 0.06), average daily gain (ADG) (P = 0.07), hot carcass weight (P = 0.04) and gain to feed ratio (G : F) (P = 0.07) were affected quadratically, in which yearling bulls adapted by 14 days presented greater final BW, ADG, hot carcass weight and improved G : F. No significant (P > 0.10) days of adaptation effect was observed for any of feeding behaviour variables. As days of adaptation increased, the absorptive surface area of the rumen was affected cubically, where yearling bulls adapted by 14 days presented greater absorptive surface area (P = 0.03). Thus, Nellore yearling bulls should be adapted by 14 days because it led to improved feedlot performance and greater development of rumen epithelium without increasing rumenitis scores.

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

“…During finishing, the cattle fed VM6 also had more meals per day and less DMI intake per meal in relation to the cattle fed VM14. Previous studies have reported that 6 days of adaptation resulted in no improvement in feedlot performance and negative effects on rumen epithelium development ( 1 , 4 ). As a result, despite the lack of VM effect on the HCW and ADG, the carcass fat deposition of the cattle fed VM6 was also negatively impacted by shortening the adaptation period.…”

“…It is well-reported in the literature that the Nellore cattle fed MON can be safely adapted to high-concentrate diets for periods not shorter than 14 days (3)(4)(5). Therefore, this section aims to discuss the potential of adapting Nellore cattle to highconcentrate diets in 14 days using VM as the sole feed additive.…”

“…Adaptation studies have been conducted previously in Brazil to determine the most appropriate adaptation length to highconcentrate diets for Nellore cattle (1)(2)(3)(4)(5). Based on the results of these studies, Nellore cattle should not be adapted in less than 14 days, regardless of the type of adaptation protocol adopted, corn processing method, and nutritional background.…”

Growth performance and rumen morphometrics of Nellore and ½ Angus/Nellore feedlot cattle adapted over 9 and 14 days to high‐concentrate diets

“…Estevam et al, (2020) evaluated increasing length of a step‐up protocol (6, 9, 14 and 21 days) utilizing cracked corn as the main energy source. It was reported that Nellore cattle adapted during 14 days presented greater final BW, average daily gain and hot carcass weight, as well as an improved gain:feed ratio compared to feedlot cattle adapted in the other lengths.…”

Changes in in vitro rumen fermentation parameters of crossbred cattle (Bos taurus) and buffalo (Bubalus bubalis) in response to diet at different time intervals

“…The time-lapse essential for the transition from high-forage to high-grain ration and vice-versa helps to establish a stable microbial community and results in significant metabolic changes in the rumen (Fernando et al 2010). This particular period adapts the animals in the form of structural changes in the rumen like ruminal papillae and functional changes in terms of the composition of ruminal microbiota (Estevam et al 2020). In the absence of a proper adaptation period, the animals may develop ruminal acidosis, ruminitis, and other health complications, which further hamper the animal production.…”