Reduction of adaptation to high-energy diets using virginiamycin: protozoa and rumen degradability

Abstract

The objective of this study was to evaluate the reduction of adaptation time to high-energy diets for cannulated Nellore cattle using Virginiamycin (VM) as a feed additive, in which ciliated protozoa and rumen nutrient degradability were assessed. The experimental design was a 5x5 Latin square, where each period lasted 21 days, with 7-day washout between periods. Five 17 mo-old Nellore yearling bulls were used (415 +/- 22 kg of body weight), and the animals were divided into five treatments: (1) MON (30 mg/kg) and adaptation for 14 days; (2) MON (30 mg/kg) + VM (25 mg/kg) and adaptation for 14 days; (3) VM (25 mg/kg) and adaptation for 14 days; (4) VM (25 mg/kg) and adaptation for 9 days; and (5) VM (25 mg/kg) and adaptation for 6 days. As the adaptation length decreased for animals consuming only VM, the rumen degradability of DM (P<0.01), NDF (P<0.01) and starch (P<0.01) decreased; however, protozoa counts of Entodinium and Total protozoa increased. It is not recommended to adapt Nellore cattle in less than 14 days.