Nellore bulls in Brazilian feedlots can be safely adapted to high-concentrate diets using 14-day restriction and step-up protocols

Abstract

In the present study, the effects of restricted intake of the final finishing diet as a means of dietary adaptation compared with diets increasing in concentrate content (step-up) over periods of 14 and 21 days on growth performance, carcass characteristics, feeding behaviour and rumen morphometrics of Nellore cattle were evaluated. One hundred and twenty 20 months old Nellore bulls (initial BW = 372.2 kg, s.d. = 21.5 kg) were randomly allocated in 24 pens (n = 5 per pen) and fed for 84 days. The study had a completely randomised design with a 2 × 2 factorial arrangement: adaptation using both 14-day and 21-day step-up and restriction protocols. Each treatment was replicated 6 times. One bull per pen was slaughtered (n = 24) at the end of adaptation period to evaluate rumen morphometrics. The remaining bulls (n = 96) were slaughtered at the end of experimental period. Interactions were observed (P < 0.05) for growth performance, feeding behaviour and rumen morphometrics variables. Overall, no protocol or adaptation length main effect (P > 0.05) was observed for any of the growth rate and carcass traits evaluated, except for hot carcass weight (P = 0.03) and dressing percentage (P = 0.04), where bulls adapted for 14 days had heavier carcasses and increased dressing percentage when compared with cattle adapted for 21 days. Cattle adapted for 21 days had a larger (P = 0.005) rumen wall absorptive surface area at the end of adaptation period than those adapted for 14 days; however, no differences were detected at the end of finishing period. Thus, Nellore yearling bulls could be adapted for 14 days regardless of the protocol.

The Effect of Transitioning between Feeding Methods on the Gut Microbiota Dynamics of Yaks on the Qinghai–Tibet Plateau

“…Machado et al [5] reported an adaptation period of two weeks for the bacterial community to stabilize under a new diet. In another trial, the adaptation of Nellore at 14 days and 21 days was compared, and it was found that although the rumen wall absorptive surface area was larger at 21 days than at 14 days, Nellore yearling bulls could become adapted by 14 days [26]. These findings support the two-week adaptive period required when transitioning between feeding methods.…”

Ruminal Fermentation Pattern, Bacterial Community Composition, and Nutrient Digestibility of Nellore Cattle Submitted to Either Nutritional Restriction or Intake of Concentrate Feedstuffs Prior to Adaptation Period

“…In general, the average adaptation period in Brazilian feedlots is reported to be 16.2 days ( Pinto and Millen, 2018 ). Further work evaluating different adaptation periods ( Perdigão et al, 2017 ; Barducci et al, 2019 ; Parra et al, 2019 ) suggested that Nellore cattle should spend a minimum of 14 days adapting to a high-concentrate diet in a step-up manner, where increasing amounts of concentrate are successively added to the adaptation diet. However, the application of these guidelines is confounded by the dietary history of the incoming calves, which can differ significantly by sourcing location.…”

The 2019 Brazilian survey on nutritional practices provided by feedlot cattle consulting nutritionists

“…Since the level of roughage inclusion in finishing diets has been decreasing over the years, cattle may take a little longer to reach the expected dry matter intake to receive the finishing diet (NASEM, 2016). However, this little increase in adaptation length when multiple step-up diets method was used, still falls into the recommendation that feedlot cattle, either in Brazil or US, should not be adapted in less than 14 days to high-energy diets (Brown et al, 2006;Parra et al, 2019), especially newly received cattle coming from either nutritional restriction or previously exposed to supplementation of concentrate feedstuffs (Pereira et al, 2020).…”