ABSTRACT

The objective of this study was to evaluate the effects of total replacement of corn by soybean meal and urea on intake and apparent digestibility of dry matter, protein metabolic profile, and nitrogen balance of lactating crossbred cows grazing with intermittent stocking Mombasa grass (Panicum maximum). Twelve milking cows were distributed in a triple 4 x 4 latin design, with a mean initial body weight of 473,0+45,0kg, average lactation period of 95,0+42,2 days and milk production of initial mean of 14,1+1,9kg/day. Cows were primiparous and multiparous. The treatments consisted of four levels of substitution of soybean meal for corn and urea (0; 33; 66; 100% in dry matter - DM). The Mombasa grass showed an average content of crude protein and neutral detergent fiber of 19 and 59% in DM, respectively. The concentrations of urea and plasma urea nitrogen were altered by replacing soybean meal with corn and urea. Protein metabolic profile was changed with the replacement of soybean meal by corn and urea. The nitrogen balance was positive and has not changed with the replacements. For mixed-race cows producing an average of 12.5kg/day and kept in good-quality pastures, one can replace soybean meal totally with corn and urea.

Keywords:
digestibility; intake; plasma urea nitrogen; protein; supplementation