Effect of energy supplementation time and sources to optimize F1 Angus-Nellore growing

Abstract

In intensively managed and nitrogen (N) fertilized pastures that have high proportions of soluble N compounds, energy supplementation with highly fermentable carbohydrates may be a strategy to maximize forage N utilization and rumen microbial protein synthesis.However, different responses to energy supplementation may occur due to the type of energy substrate and the time of supplement supply to the animals, in order to coincide with the end of the main grazing events, aiming to increase N uptake by microorganisms. The experiment will be conducted at Forage and Pastures Sector of FCAV/UNESP during the growing phase of animals kept in palisade cv. Marandu pastures. We will use 48 Aberdeen Angus x Nellore bulls as testers animals, With initial Body Weight (IBW) of 280 kg. The experiment will be conducted in a completely randomized design with 4 treatments and 3 replications. The treatments will consist of: 1 - energy supplementation 0.3% of BW with maize supplied at 9 am; 2 - energy supplementation 0.3% of BW with citrus pulp supplied at 9 am; 3 - energy supplementation 0.3% of BW with maize supplied at 5 pm; 4 - energy supplementation 0.3% of BW with citrus pulp supplied at 5 pm. For evaluation of ruminal and blood parameters, Efficiency of N Use (ENU), intake and digestibility, 8 ruminal cannulated ½ Angus x Nellore bulls will be used, with 280 kg of IBW, distributed in a 4x4 double latin square design. The study aims to investigate the isolated and/or associated effects of two feeding times (9 am and 5 pm) with two sources of energy supplementation (maize or citrus pulp) in the growing of F1 Angus x Nellore bulls in palisade grass pastures, and its implications on the structural characteristics and chemical composition of herbage, intake, nutrient digestibility, ENU and microbial protein productions, animal performance, area gain and stocking rate. (AU)