Óleo essencial de orégano (Origanum vulgare L.) como aditivo zootécnico na ração de frangos de corte

Abstract

The objective of this study was to evaluate the efficacy of the oregano essential oil (Origanum vulgare L.) as an alternative to antimicrobials (antibiotics and chemotherapy) in broiler diets. We used 300 Cobb broiler chicks, males, distributed in a randomized block design with five treatments and six replicates of 10 birds. The experimental treatments consisted of diets with different levels of oregano essential oil (300, 600 and 900 mg / kg diet), a negative control without antimicrobial additive and a positive control with 10 mg of colistin sulfate antibiotic per kg of feed. Diets were fed to the birds in two phases, initial (1-21 days) and growth (22 to 39 days). In the period from 1 to 21 days there were no differences (P>0.05) regarding the performance of the birds in the treatments. In the period from 22 to 39 days the birds of the negative control showed the lowest feed intake (P<0.05) compared to other treatments. For weight gain were no significant differences. The birds of the positive control showed the worst feed conversion (P<0.05). For the whole period from 1 to 39 days the birds of the negative control had lower feed intake (P<0.05) to birds that received 300 mg of oregano essential oil per kg feed, did not differing from other treatments. For weight gain there were not observed significant differences between treatments. The worst feed conversion was observed in birds of the positive control (P<0.05), with no difference between the other treatments. The levels of oregano essential oil positively influenced (P<0.05) body weight after fasting, the weights of carcass, breast, thigh and back and carcass yield. The treatments not influence the absolute and relative weights of organs (P>0.05). No differences (P>0.05) in apparent metabolizable coefficients of dry matter, metabolizable energy and apparent metabolizable energy corrected by nitrogen balance (P>0.05). The chickens of the positive control showed a lower percentage (P<0.05) ether extract in meat chicken breast in relation to the negative control and treatments with 600 mg oregano essential oil per kg of feed. The chickens of the treatments with 300 and 900 mg oregano essential oil per kg of feed had a lower percentage (P<0.05) of ash in breast meat compared to other treatments. In relation to weight loss by cooking the breast meat did not differing from treatments (P>0.05). The oregano essential oil positively influenced (P<0.05) in the blood and leukocytes counting. The chickens of antibiotic treatment showed elevated levels of liver enzymes and uric acid metabolism and chickens that received 900 mg of oregano essential oil having high concentration of uric acid, creatinine and urea blood. There was a significant reduction (P<0.05) of the total count of coliforms in chickens with antibiotics or oregano essential oil. The oregano essential oil can be used as an alternative to antibiotic without prejudice to the performance of broilers.