Effect of monensin on performance in growing ruminants reared under different environmental temperatures |
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Authors: | Má rcia Saladini Vieira Salles,Marcus Antonio Zanetti,Evaldo Antonio Lencioni Titto,Renata Maria Consentino Conti |
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Affiliation: | 1. Agência Paulista de Tecnologia dos Agronegócios, Avenida Bandeirantes 2419, CEP: 14030-670 Ribeirão Preto, SP, Brazil;2. Faculdade de Zootecnia e Engenharia de Alimentos-USP, Brazil;3. Anhanguera Educacional, Brazil |
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Abstract: | To evaluate the effect of monensin on the performance of growing cattle under different environmental temperatures, 24 male calves (81.9 ± 7.7 kg mean weight and 100 days old) were distributed in a 2 × 2 factorial arrangement, contrasting 0 or 85 mg monensin/animal per day at 24.3 or 33.2 °C (environmental temperatures). Monensin supplementation increased weight gain (P=0.036), improved feed efficiency (P=0.040), increased ruminal concentrations of volatile fatty acids (VFA; P=0.003) and decreased the molar proportion of butyrate (P=0.034); all effects irrespective of environmental temperatures. A temperature-dependent monensin effect was detected on nitrogen retention (P=0.018) and N retained:N absorbed ratio (P=0.012). Animals fed monensin retained higher N amounts than those of the non-supplemented ones when the environmental temperature was 33.2 °C. Environmental temperature and monensin supplementation showed an interaction effect on urine N concentration (P=0.003). Temperature did not affect N excretion in monensin-fed animals, but increased N excretion in the non-supplemented ones. Monensin increased the crude protein (CP) digestibility (P=0.094) for animals at both temperatures. In conclusion, monensin changes the metabolism of the heat-stressed animals by increasing rumen VFA concentration, digestibility and protein retention, thus improving food use and weight gain. |
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Keywords: | CP, crude protein VFA, volatile fatty acids NH3-N, ammoniacal nitrogen DM, dry matter EE, ether extract NDF, neutral detergent fiber GE, gross energy DMD, dry matter digestibility CPD, CP digestibility ADFD, ADF digestibility EED, EE digestibility CED, crude energy digestibility DEI, digestible energy intake T3, triiodothyronine |
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