Effectiveness of various barbiturates in chickens of different ages

: Phenobarbital, allobarbital, and pentobarbital in the doses of 40 and 80 mg per 1 kg body mass were applied intramuscularly to groups of the cockerels of the WL breed at the age of two days, one, two, and six weeks (each group had ten birds) and to eight-week-old WL cockerels in groups of five birds. The methods of clinical observation and repeated determination of the response of the animals to sonic stimuli and contact stimuli, and the evaluation of the quality of some reflexes (particularly the spontaneous position of the body and the correction of the lateral position) were used for the study of suppression evoked by the applied barbiturates. Sleep occurred first after the application of pentobarbital (sooner in younger age groups). The latest beginning of sleep was observed after phenobarbital; in the latter case, sleep was hard to evaluate because it was not very deep. The time of sleep had the longest duration after allobarbital (only in the eight-week-old sleep was longer after pentobarbital), and the shortest after phenobarbital; there were also differences in the duration of sleep between the age groups of birds. The pentobarbital dose of 80 mg kg-1 of body mass killed birds in the three youngest age groups )in the two-day-old it killed nine of ten birds, in the one-week-old eight of ten birds, and in the two-week-old two of ten birds). The differences in the effectiveness of the applied barbiturates in two doses per unit of body mass were related to the age of the animals, even in the cases of the shortest age intervals between individual groups. Very high interspecies differences ensue from a comparison with the doses of these barbiturates usually applied to man.