The growth of pigs kept to one level of feeding, in two environments, and fed diets with and without an antibiotic

Abstract

1. Pigs housed in both a good and a bad piggery were kept to a medium plane of feeding on diets with and without a procaine penicillin supplement. Antibiotic improved neither efficiency nor rate of growth in either piggery during the period from weaning to 100 lb. live weight, nor from then to slaughter at 200 lb. live weight. The average temperatures during the first half of the experiment were 43 and 51° F. in the bad piggery and in the sleeping pens of the good piggery respectively. During the second half of the experiment these averages were 54 and 58° F. respectively.2. Between weaning and 100 lb. live weight, pigs housed in the bad piggery grew 6% more slowly and 5% less efficiently than in the good piggery, but although the growth rates fitted in well with previous observations, neither difference was statistically significant in this experiment.3. Between 100 and 200 lb. live weight pigs housed in the good piggery grew 3% less efficiently than in the bad piggery, but there was no difference in rate of growth. The difference in efficiency was statistically significant.4. Carcasses from pigs housed in the good piggery were fatter than from pigs housed in the bad piggery. These fatter pigs also had higher killing-out percentages.5. Although dietary antibiotic supplement had no effect upon growth rates or carcass measurements, it resulted in higher killing-out percentages.