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Effect on plasma metabolites of Nellore bulls fed Ractopamine hydrochloride and protein level
The aim of this study was to evaluate was to evaluate the effects of ractopamine hydrochloride (RH) and dietary crude protein (CP) on blood metabolites of Nellore young bulls. Forty eight Nellore bulls were grouped by BW, and randomly assigned to treatments in a 2x2 factorial arrangement of treatments. The factors were two levels of dietary CP (100 and 120% of MP requirement), and two levels of RH (0 and 300 mg/animal/d). Treated animal received RH for the final 35d before slaughter. Blood was collected at the beginning and at the end of RH supplementation by venipuncture and/or puncture of the coccygeal artery, prior to the morning feeding. Blood samples were collected into 10-mL BD Vacutainers®, without anticoagulant, for the measurement of serum glucose, total protein, albumin, plasma urea nitrogen (PUN), aspartate aminotransferase (AST), γ-glutamyl transferase (GGT) and alkaline phosphatase (ALP). Blood parameters were analyzed using commercial kits (Laborlab®, São Paulo, Brazil and CELM, São Paulo, Brazil) by endpoint or kinetic colorimetric methods in an ABS-200 Automatic Biochemistry Analyzer (CELM®). The statistical analyses were conducted using SAS, version 9.1.2 for Windows (SAS Institute Inc., Cary, NC, USA). Data were analyzed as a randomized block design with a 2x2 factorial arrangement of treatments using the MIXED procedure of SAS. There was no effect of treatments, or of interaction, on plasma creatinine, AST or GGT (P > 0.05). Dietary CP level tended to increase blood urea (31.2 vs. 40.8 mg/dL, P = 0.07). RH supplementation altered glucose, ALP and total protein; however, the effect was dependent on the dietary CP level. RH supplementation decreased plasma glucose concentration at CP100 (P = 0.05), and had no effect at CP120 (P = 0.87). For ALP activity, RH supplementation increased its activity at CP120 (P = 0.05) and had no effect at CP100 (P = 0.42). RH supplementation increased plasma total protein at CP 120 (P = 0.03) and had no effect at CP100 (P = 0.17) In conclusion, RH supplementation and CP levels leads to slight changes on plasma metabolites.
Keywords: Crude protein, Beta-agonist, Plasma metabolites