<b>Nitrogen balance and endogenous loss estimate in lactating cows fed with diets of forage cactus and increasing levels of urea and cassava</b> - DOI: 10.4025/actascianimsci.v28i1.848

Abstract

The effects of the soybean when replaced by a mixture of urea and cassava, in rations composed of forage cactus, sorghum silage and concentrate, were assessed on: (i) urea concentration; (ii) nitrogen (N) balance; and (iii) total endogenous loss estimate. Eight lactating Holstein/Zebu cows were distributed in two 4x4 simultaneous latin squares. Urea and N-urea concentration in plasma and milk (mg dL-1), and milk N-urea (g day-1) were not affected by the increase of urea levels in the ration; their means were 31.37, 14.62, 37.43, 17.44, and 5.37, respectively. Also, urea and N-urea urinary excretion were not affected by the increase of urea levels in the ration, and the mean values of those parameters were 249.45 and 116.24 mg kg-1 LW, respectively. The treatments did not influence N levels, with average values of 87.75, 87.63, 62.91, and 60.97 g day-1 to 0, 1.06, 2.12 e 3.20 % of urea addition in the ration, respectively. The endogenous loss estimate varied according to the nutritional demand system used.