Incidence of rumenitis and rumen morphometrics of feedlot Nellore cattle submitted to different nutritional managements prior to the adaptation period

Abstract

The objective of this study is to evaluate the effect of either nutritional restriction or intake of concentrate ingredients prior to the adaptation period on incidence of rumenites and morphometric variables of rumen epithelium. It will be used 96 Nellore yearling bulls, with approximately 370 kg of body weight. Cattle will be blocked by weight, and randomly distributed in 24 pens, which will be considered the experimental unit. The study will last 112 days, divided into 28 days of pre-adaptation, where treatments of this study will be applied, and 84 days of feeding with high-energy diet. In both studies, the treatments will be disposed as follows: Maintenance (forage ad libitum + mineral supplement); Restriction (forage restricted at 1,4% of body weight + mineral supplement), and Concentrate (forage ad libitum + 0,5% of body weight of a mix of concentrate feedstuffs and mineral supplement). At the end of the first 28 days of study, one animal per pen (n = 24) will be slaughtered to evaluate the rumen epithelium. The remaining animals (n = 72) will be slaughtered after 112 days of feeding. The adaptation protocol for these animals is made in steps (step-up), in which two diets containing 72% (adaptation 1) and 79% (adaptation 2) concentrate will be fed. The finishing diet will consist of 86% of concentrated ingredients. After slaughter, the rumens of all animals will be emptied and washed, and the incidence of rumenites on a scale of 0 (no injuries) to 10 (ulcerative lesions covering all the rumen) will be evaluated. Subsequently, a 1 cm2 fragment from the cranial sac, and other from ventral sac of the rumen of each animal will be collected for morphometric evaluations, such as average number of papillae, absorptive surface area, papillae height and area, thickness of the keratin layer and mitotic index of the basal layer. (AU)