Reduced diet quality or the removal of antibiotics in starter diets has no overall effect on growth performance to market, but it may affect the ileal bacterial profile. Nursery pigs were fed either a high or low quality protein source, and with or without chlorotetracycline. Bacterial profiles were more affected by the week of nursery than by diet.  Pigs fed the low quality diet had an increase in Clostridium paraputrificum between nursery week 2 and 8, and Clostridium leptum decreased. The proportion of Sarcina genus bacteria declined in low quality diets, but increased in high quality diets. Overall, this suggests an increase in beneficial bacteria and decrease in potentially pathogenic bacteria in pigs fed low quality diets, which may help to explain the compensatory growth these pigs experience post-nursery.