Performance and serum chemistry profile of lambs fed on rations with increasing levels of urea

Abstract

Feed intake and efficiency, animal performance, and protein and energy metabolism were studied in lambs that were fed on increasing levels of urea (0.0, 0.5, 1.0, and 1.5% of dry matter [DM]). A completely randomized design was used, with four treatments (urea levels) and six replicates. The lambs were fed ad libitum for 56 days until they reached an average body weight of 35 kg. The rations were composed of 34% Tifton 85 hay (Cynodon spp.) and 66% concentrate. Crude protein (CP) constituted 17% of the diet on a dry matter basis, and total digestible nutrients (TDN) accounted for 65%, on average. The dry matter intake (DMI) and crude protein intake (CPI) were not influenced by the urea levels in the diet, presenting average values of 1.175 and 0.206 kg animal -1 day -1 , respectively. The average daily gain (ADG), feed conversion ratio (FCR) and gross feed efficiency (GFE) were also not influenced by urea levels (0.225 kg day -1 , 5.33 kg DM kg gain -1 and 0.195 kg gain kg DM -1 , respectively). Except for urea and glucose concentrations, blood parameters did not change with increasing urea in the diets. The mean values for total protein, albumin, globulin and creatinine in the serum were 7.11 g dL -1 , 3.36 g dL -1 , 3.75 g dL -1 and 0.91 mg dL -1 , respectively. Serum urea decreased linearly and serum glucose increased linearly with urea levels in the diet. The addition of 1.5% of urea to the diets did not change feed intake and efficiency or animal performance, and did not cause metabolic disorders in feedlot lambs in the finishing phase. Key words: Blood. Finishing. Glucose. Nitrogen. Sheep. ResumoAvaliou-se o consumo de alimento, o desempenho animal, a eficiência alimentar, e o metabolismo proteico e energético de cordeiros alimentados com rações contendo níveis crescentes de ureia (0,0; 0,5; 1,0; 1,5% da matéria seca -MS). O delineamento foi inteiramente casualizado com quatro tratamentos (níveis de inclusão de ureia) e seis repetições por tratamento. Os cordeiros foram alimentados à vontade por 56 dias até atingirem peso corporal (PC) médio de 35 kg. As rações foram compostas por 34% de feno de Tifton 85 (Cynodon spp.) e 66% de concentrado, com 17% de proteína bruta (PB) e 65% de nutrientes digestíveis totais (NDT), em média, com base na matéria seca (MS). O consumo de matéria seca (CMS) e de proteína bruta (CPB) não foram influenciados pelos níveis de inclusão de ureia na ração, apresentando valores médios de 1,175 e 0,206 kg animal -1 dia -1 . O ganho médio diário (GMD), a e 0,91 mg dL -1 . A ureia sérica apresentou resposta linear decrescente, enquanto a glicose sérica de apresentou resposta linear crescente ao aumento da inclusão de ureia. A inclusão de até 1,5% de ureia na MS em rações isoproteicas não afeta o consumo de alimento, o desempenho e a eficiência alimentar, e não causa prejuízos metabólicos em cordeiros confinados na fase de terminação. Palavras-chave: Glicose. Nitrogênio. Ovinos. Sangue. Terminação.

The economic viability of the inclusion of urea in the ration for feedlot lambs

“…As reported by Vivian et al (2017) and Rozanski et al (2017), DMI, ADG, SW, CCW and CCY (Table 2) were not affected by the inclusion of urea in the ration, which demonstrated that levels of urea ranging from 0.0 to 1.5% DM provide the same productive response in crossbred Dorper lambs finished in a feedlot. Regarding the CR, the minimum and maximum costs were verified in the rations with 1.0% DM of urea and without urea, respectively (0.23 and 0.30US$/kg DM, respectively; Table 3).…”

“…In the present study, the best economic result was also followed by the best biological responses (lower DMI and higher ADG and CCY; Table 2), providing even more support for the ration with 1.5% DM of urea. Also, Vivian et al (2017) found that CP intake was not affected by the addition of urea to the rations tested in the present study, which indicates another advantage for the ration with 1.5% DM of urea. Khattab et al (2013) reported that the DM digestibility increased, the nitrogen (N) excretion in feces is reduced and the N excretion in urine is not affected when the urea content increases from 0.0 to 1.5% DM of ration.…”

“…The previously described performance and carcass traits were the production indexes considered in the economic analysis; they are summarized in Table 2. Vivian et al (2017) The economic analysis was performed based on the DMI and ADG to verify the feasibility of the use of rations without considering the other fixed and operational costs, since these were the same for the four treatments. The cost of feedstuffs (Table 1) and the marketing value of cold carcasses were obtained during the two first weeks of November, 2014 in the western region of Paraná state.…”

Carcass and meat traits, and non-carcass components of lambs fed ration containing increasing levels of urea

“…Additional results of this study obtained by Vivian et al (2017) indicated there was no significant effect (P> 0.05) of urea levels on DM intake (DMI). The average DMI during the trial was 1.174 kg animal -1 d -1 , and met the requirements for fast and moderate growth according to the NRC (1985) (DMI = 1.0 to 1.3 kg DM animal -1 d -1 ).…”

Carcass and meat traits, and non-carcass components of lambs fed ration containing increasing levels of urea

“…The high NDF on these diets is associated with the greater inclusion of soybean hulls in their compositions with inclusion of 25 and 49% DM, respectively. In assessing the nutrient intake by lambs of this study, Vivian et al (2017) observed a quadratic effect of urea levels on NDF intake, which reached a maximum value (0.665 kg DM d -1 ) in the ration with 1.0% DM of urea. However, the regression equation indicates that the maximum NDF intake (0.604 kg DM d -1 ) may be achieved with the inclusion of 0.85% DM of urea in the ration.…”