Efeitos da associação entre tamanho de partículas de silagem de milho e inclusão de um blend mineral-vitamínico na dieta de novilhas Nelore em terminação

Abstract

The objective was to evaluate the effect of particle size (Short -13 mm or Long - 24 mm) of whole corn plant silage, associated or not with the supplementation of a mineral-vitamin blend, containing hydroxy-minerals (Copper - Cu and Zinc - Zn) and B vitamins protected from ruminal degradation (thiamine, pantothenic acid, pyridoxine, biotin, folic acid and cobalamin) on feeding behavior, fecal parameters, histology of ruminal papillae and blood parameters of feedlot heifers (Nelore) at fattening stage. Ninety-six Nellore heifers with average initial weight of 258 kg were used in a randomized block design, with a factorial arrangement 2 × 2 (two particle sizes and with or without inclusion of the mineral-vitamin blend). The diets were formulated to provide gain of 1.4 kg/day, ad libitum, supply twice a day. The animals were housed in thirty-two collective pens with three animals per pen, and eight replicates per treatment. The treatments evaluated were: Short Control (CC), Short with blend (CB), Long Control (LC) and Long with blend (LB). The animals were weighed at the beginning and at the end of the experimental period, after solid fasting of 16 hours, an observation of the feeding behavior was performed for 24 hours. Two spot fecal samples were collected during confinement. Blood samples were collected at the end of the experiment. After slaughter, samples of 5 x 5 cm2 in the ventral sac of the rumen were taken for histological measurements. There was an effect (P < 0.05) on NDF consumption (kg/DM) being higher for treatment with long fiber, the other variables of feeding behavior did not show statistical difference. The treatments without the inclusion of the mineral-vitamin blend had a greater preference for the particles retained in the 19 and 8mm sieves. Fecal parameters had effect (P < 0.05) for fecal pH, being higher for treatment with long fiber. Values of width and area of ruminal papillae were higher for treatments with inclusion of long fiber, there was an interaction fiber x additive to the value of papilla length. The experimental groups that consumed the blend had higher concentrations of GGT (U/L) compared to the control treatments, the plasma glucose level was affected by fiber size, the inclusion of long fiber showed higher values. The inclusion of the mineral-vitamin blend reduce the preference of animals for longer particles (> 8 mm). The inclusion of the blend brings improvement in liver metabolism, avoiding the increase in concentrations of GGT, U/L when compared to the control treatment. The particle size (24 mm) of whole corn plant silage can be beneficial in the development of ruminal papillae, increasing the width. It was also shown to increase plasma glucose concentrations and fecal pH.