Silagem de capim-marandu em substituição à silagem de sorgo na terminação de novilhas 3/4 Zebu x Holandês

Abstract

This work was carried out in order to evaluate the consumption, the digestibility, the ingestive behavior, the performance, the carcass characteristics and the economic feasibility of the substitution of the sorghum silage by Marandu grass silage in the feeding of ¾ Zebu x Holstein heifers under feedlot for 84 days. The work was carried out on the farm of the Empresa de Pesquisa Agropecuária de Minas Gerais – EPAMIG, located in the municipal district of Felixlândia in the West Center of Minas Gerais State. For the evaluation of performance, carcass characteristics, meat quality and economic feasibility, an entirely randomized experimental design was used with 20 ¾ Zebu x Holstein heifers with initial average weight of 346,25 kg, divided into four treatments: Treatment 1 - roughage fraction of the diet composed of 100% of sorghum silage; Treatment 2 - roughage fraction of the diet composed of 70% of sorghum silage and 30% Marandu grass silage; Treatment 3 - roughage fraction of the diet composed of 30% of sorghum silage and 70% of Marandu grass silage; Treatment 4 - roughage fraction of the diet composed of 100% of Marandu grass silage. For each treatment were made five repetitions being each heifer as a repetition. At the same time for intake evaluation, apparent digestibility, feed conversion, blood parameters and ingestive behavior, a double and simultaneous 4 x 4 (treatment x animal) Latin square design was used, with the same treatments from the entirely randomized design, composed of 8 ¾ Zebu x Holstein heifers with initial average weight of 377.75 kg. The concentrate was added to roughage fraction of the diet, furnished to ingestion of 1.2% of live weight of the heifers, which consumed isoprotein diets, having as only variation source the different roughages and their proportions in each treatment. The increase of the levels of substitution of sorghum silage for Marandu one in the diets decreased linearly the total weight gain and the average daily gain of the heifers, it increased the feed conversion and the mineral matter consumption, it reduced the intake of nonfiber carbohydrates and of NDT, it interfered in a decreasing lineal way in the coefficients of dry matter digestibility and of nutrients and it increased the urea levels in the blood plasma. In relation to ingestive behavior, there was increase of feeding time and number of rumen bolus a day, decrease of the time and number of chews per bolus and decrease of chews number per minute. It also there was a increase of the time spent for intake of 1 kg of dry matter and for 1 kg of NDF, with decrease of the feed efficiency of both ones. Differences were not observed in relation to carcass characteristics. For the meat qualitative characteristics, it was verified increase of the mean shear force and water holding capacity, and quadratic behavior of the water loss by cooking. In the analysis of economic feasibility, the substitution of sorghum silage by Marandu grass silage resulted in lower profitability of this production system.