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Effect of antibiotic supplementation on growth performances in chickens in Zaire comparison with effects in temperate areas. The influence of different antibiotics, bacitracine (50 mg per kg), virginiamycine (20 mg per kg) and avoparcine (15 mg per kg) was tested on growth and feed conversion of chickens from a double purpose line under warm wet tropical conditions. In general, the beneficial effect of additives was much more pronounced in this experiment compared to data with identical doses of bacitracine and viriginiamycine in temperate areas. However this was hardly the case for avoparcine, indicating an interaction between the environment and the nature of antibiotic agent.

After storage at 12 degrees C and 90 to 95 p. 100 humidity, for periods of 1, 5, 8, 11 and 14 days, Rhode Island Red eggs were incubated at 37.5 degrees C and 60 p. 100 humidity. Whatever the total duration of incubation within the experimental conditions, maximal serum levels of triiodothyronine (T3) and thyroxine (T4) were obtained the day of pipping. Embryos having perforated the air-space membrane the day before pipping showed elevated serum T3, but not T4, levels as compared to embryos without a perforation. The lower serum T3 levels, obtained at pipping, after longer periods of preincubation storage are discussed in relation to other experiments on perinatal changes in serum iodo-hormones.