Performance, digestibility and carcass characteristics of feedlot dairy steers fed diets with different urea levels

Abstract

The effects of urea levels on feed intake, digestibility and carcass traits of 27 confined cross bred steers weighing 303.25 ± 60.8kg, were evaluated. After weighing, castrating, vaccinating and a period of seven days, three steers were slaughtered at the beginning of the experiment and the remaining 24 were allotted in a completely randomized design to four isonitogenous experimental diets (12% of crude protein) and increasing level of urea on the dry matter-basis (0.0; 0.65; 1.30 and 1.65%) to replace soybean meal, so that the final content of the experimental diets were approximately 22, 37, 50 and 63% of crude protein in the form of NPN. Corn and elephant grass silages were supplied at a 70:30 ratio and the total diet had a 65:35, forage: concentrate ratio on a DM-basis. The urea level did not affect nutrient intake, except for rumen degradable protein (RDP) and total digestible nutrients (TDN) linearly increased in function of diet urea level. The nutrient digestibilities linearly increased except for ether extract and non fiber carbohydrate (NFC). A quadratic effect of diet urea level on daily weight gain and no effect of urea level on carcass traits were observed. Urea can totally replace soybean meal in diets for confined crossed dairy steers allowing gains of 1kg/day. Urea can enhance nutrient digestibility of diets.

Productive and reproductive performance of heifers fed different levels of urea in the diet

“…The fact that Magalhães et al (2006) and Rennó et al (2005) used urea levels up to 1.95% of the diet and did not observe reduction in DM intake, as verified in the present experiment with levels between 0.7 and 1.32% urea in the diet, was explained by the quantity of concentrate in the diets (35% and 50% x 23%), that were greater and may have made more energy available.…”

“…Productive and Reproductive Performance of Heifers Fed Different Levels of Urea in the Diet Rennó et al (2005) and Magalhães et al (2006) supplied diets with 50:50 and 65:35 roughage:concentrate ratios, respectively, but with the same increasing urea levels (0.0, 0.65, 1.30 and 1.95% total DM in the diet) for feedlot crossbred steer and observed no effect of the urea on DM intake, with means of 8.97 kg day -1 and 6.71 kg day -1 respectively. The fact that Magalhães et al (2006) and Rennó et al (2005) used urea levels up to 1.95% of the diet and did not observe reduction in DM intake, as verified in the present experiment with levels between 0.7 and 1.32% urea in the diet, was explained by the quantity of concentrate in the diets (35% and 50% x 23%), that were greater and may have made more energy available.…”

“…This fact must have been a consequence of the protein content of the silage used in the formulation with 8.1% CP, while the silage supplied in the present study contained only 5.8% CP, reducing the protein level of the diets from 14% to 9.71; 10.40; 10.50 and 10.70% CP, respectively, for the levels of 0.0, 0.44, 0.88 and 1.32% urea in the total DM. Rennó et al (2005) and Magalhães et al (2006) worked with the same increasing urea levels (0.0; 0.65; 1.30 and 1.95% total DM) in isoprotein diets (12% CP) for feedlot crossbred steer and did not observe a significant effect of including urea in the diet on the CP intake, with means of 0.85 kg day -1 and 1.1 kg day and %LW, presented quadratic response to the increase in the urea level in the diet (p < 0.05). Maximum intakes were estimated from the regression equations of 0.17 kg day -1 , 2.25 g kg -1 LW 0.75 and 0.053%LW, for the 0.7% level of urea included in the diet (TAB.…”

“…Substituting true protein sources, such as soybean meal, with urea in feedlot steer diet has shown good results, giving food intake and weight gain similar to those obtained with true protein and in other cases it has generated efficient food conversion because it reduced food intake without affecting weight gain (MAGALHÃES et al, 2006;RENNÓ et al, 2005).…”

Aspectos produtivos e econômicos de novilhos mestiços alimentados com suplementos proteico-energéticos contendo ureia

“…Segundo Magalhães et al (2006) e Paixão et al (2006, as recomendações acerca da utilização de ureia para bovinos, principalmente aqueles com grau de sangue da raça holandesa, não tem se mostrado adequadas.…”