Results are presented of an investigation involving 328 pigs on 7 farms in East Anglia, on the effect of oxytetracycline (10 g./ton), oleandomycin (2·5 g./ton) and oxytetracycline (10 g./ton) plus oleandomycin (2·5 g./ton), on the live-weight gain, feed consumption and feed conversion efficiency of pigs from weaning to slaughter at approximately 260 lb. live-weight. Effects on number of days from weaning to slaughter and carcass characteristics are also given.
Both antibiotics gave significant improvements in daily live-weight gain (5·4% for OTC and 4·0% for OM) and feed conversion efficiency (3·9% for OTC and 2·3% for OM). There was a significant negative interaction between the antibiotics on live-weight gain from weaning to slaughter.
The average number of days from weaning to slaughter was significantly reduced by both antibiotics (5·8 days for OTC and 5·4 days for OM) and there was a significant interaction between antibiotics.
Feed conversion efficiency for all pigs was significantly better on those farms where antibiotics had not previously been used but the antibiotic treatment effects were the same in both categories of farm studied.