The effects of continuous administration of penicillin to successive generations of chicks.

For some years antibiotics have been included in the feed of young pigs and poultry to produce faster growth. With this widespread use, it is important to know whether there are any cumulative effects either on the mature treated animals or on successive generations of their progeny. The experiment here described was designed primarily to investigate whether the inclusion of penicillin in the diet of birds throughout life affected the early growth rate and the response to penicillin of their progeny. In addition, records of egg production, hatchability and mortality were kept and are presented, although these observations must be interpreted with caution in view of the small numbers involved. The mean annual response to penicillin of chicks from a commercial source is given for the last 5 years.