BIOLOGICAL RESPONSE TO FOUR COCCIDIOSTATS IN BROILER CHICKENS

Abstract

New coccidiostats appear frequently in the market due to increased resistance to coccidia and these new drugs must be evaluated periodically under different conditions. For this reason an experiment was carried out with 1440 one-day old broiler chicks Arbor Acres in order to evaluate four coccidiostats: T1, Diclazuril (1 mg kg-1); T2, Salinomycin (60 mg kg-1); T3, Maduramicin (5 mg kg-1); T4, Monensin (100 mg kg-1); in comparison with T5, infected unmedicated chicks (INM) and T6, uninfected and unmedicated chicks (NINM). These drugs were included in the diets (which were isocaloric and isonitrogen) at the beginning of the experiment and were withdrawn five days before slaughter (56 days old). At 21 days of age, birds were infected with a mixed culture of three coccidia species: Eimeria acervulina (50 000 oocysts); E. necatrix (5 000 oocysts) and E. tenella (5 000 oocysts). The coccidial infection was induced by incorporating oocysts in the feed after a 12 h fasting period. Feed and water were offered ad libitum during the experimental period. Variables evaluated were: coocidiosis mortality (CM), lesion score (LS) evaluated in duodenum, jejunum and caecum seven days postinfection (dpi); oocyst count in feces (OC) at 6, 7 and 8 dpi. Body weight gain (BWG) and feed intake (FI) data were collected every week and used to calculate feed conversion (FC). At the end of the experiment the xanthophylls content (XA) was evaluated in skin, blood and liver. The statistical analysis indicated differences among treatments (p0.05) in BWG and FC among treatments. The XA in birds? skin of T1 was greater than in the birds that received the other coccidiostats, but similar to birds of T6. The xanthophylls content in blood was not different (p>0.01) among treatments, and the lowest value was found with birds INM. At 28 days of age Diclazuril and Maduramicin produced the best results and the worst were obtained with Monensin and with infected unmedicated chicks. Although at 56 days no differences were observed (p>0.05) in performance among birds fed the different coccidiostats, a high CM (6.7 %) was detected 7 dpi in the Monensin birds.