Milho e ureia em substituição ao farelo de soja para vacas em lactação a pasto

Abstract

An experiment was conducted with the aim of examine the total replacement of soybean bran with maize and urea in the diet of milky cows and how this affects consumption and digestibility of nutrients, production and composition of milk, the protein metabolic profile, the nitrogen balance and feeding behavior in mixed-race, lactation cows on Mombaça grass (Panicum maximum cv. Mombaça) intermittent pastures. Twelve cows milking were distributed in a triple 4 x 4 latin design. Experimental treatments consisted of four soybean meal replacement levels by corn more urea (0; 33; 66 and 100 %). The grass was handled under an intermittent lotation regimen with a 15-day interval between defoliation and a 2-day period of occupation of each paddock, seventeen is total. Irrigation and fertilization were carried out with 400 kg/ha of the 20.10.20 (NPK) mixture after release of animals from each paddock. Measurements were made on grazing before entering and after leaving the animals in each paddock - height, light interception, leaf area index and herbage mass. Titanium dioxide external marker was used to estimate the intake of fodder. The feeding behavior was conducted on the first day of each collection period, by visual observation by instant scanning method, in ten-minute intervals. The Mombaça grass has an average content of CP and NDF of 19% and 59%, respectively. The canopy height at the time of input of animals in the paddocks was 97 cm, and the exit height was 71 cm. The replacement did not alter consumption and digestibility of nutrients. A linear decrease was verified on the production of milk, but no changes were observed in the production of milk corrected with 4.0 % fat. The main components of milk (fat, protein, casein, lactose and total solids, in g/kg) were not affected. The protein metabolic profile was altered with the replacement of soybean bran with maize and urea. The nitrogen balance was positive and did not change with such replacement. The Mombaça grass has productive potential for mixed-race cows raised under an intermittent lotation regimen, but its potential could be enhanced by optimizing the lotation rates. The replacement in the diet did not affect consumption and digestibility of nutrients for milky cows kept in pastures, and the production of corrected milk and its components and the feeding behavior of animals were not affected either. Under the conditions of this study, the replacement in the diets does not change the production performance and the physical-chemical characteristics and composition of the milk, and are appropriate for crossbred cows in mid lactation third, producing an average of 12,5 kg/ day-1, kept in pastures.