Evaluation of collection days and times to estimate urinary excretion of purine derivatives and nitrogen compounds in grazing Nellore cattle

• Autor(a) principal: Silva Júnior, J. M.
• Data de Publicação: 2018
• Outros Autores: Rennó, L. N., Valadares Filho, S. C., Paulino, M. F., Detmann, E., Menezes, G. C. C., Martins, T. S., Paula, R. M., Rodrigues, J. P. P., Marcondes, M. I.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: https://doi.org/10.1016/j.livsci.2018.09.016; http://www.locus.ufv.br/handle/123456789/23848
• topic: Allantoin; Bovine; Collection times; Creatinine; Urine volume

The objectives of this study were to evaluate the effects of collection day and 4-hour collection times on the urinary excretion of creatinine, purine derivatives (PD), and nitrogen compounds in grazing Zebu cattle. Five Nellore heifers (300 ± 15.2 kg body weight [BW]) were used in a 5 × 5 Latin square design. Five treatments were tested: a mineral mixture supplied at 60 g/day (g/d) (control – CON); two treatments higher in salt and urea to achieve a reduced ad libitum intake of supplements: one with 39.7% crude protein (CP) on a dry matter (DM) basis (RI40) and another with 69.4% CP (RI70), both fed ad libitum; and two supplements with restricted feeding rates relative to BW: both with 20.3% of CP fed at 5 g/kg BW (BW5) or 10 g/kg BW (BW10). Each experimental period lasted 17 d (12 used for adaptation and 5 for sample collection). Six collection times at 4-hour intervals were established for each 24-hour collection day. For total urine collection, a Foley catheter was used and the collection bag attached to the animal was emptied every 4 h. Collection day, collection time, treatment or their interactions (P > 0.05) had no effect on urinary excretions of creatinine, allantoin, uric acid, and PD, nor on their ratio with creatinine. However, an interaction between collection times and treatment (P < 0.05) was observed for the excretions of urinary nitrogen and urea nitrogen, and for their ratio with creatinine. The results supported the use of a single day-collection estimate the excretion of purine derivatives and nitrogen compounds in beef cattle kept in pasture. A single urine collection for 4-hour obtained at any time during the day was adequate to estimate the purine derivatives excretion. However, using a single 4-hour urine collection to estimate the urinary excretion of nitrogen compounds in grazing Zebu cattle is not recommended.