PITTSBURGH — The Pittsburgh Zoo & PPG Aquarium says a baby elephant born prematurely in May has “taken a turn for the worse” and was having a feeding tube implanted.

Zoo chief executive officer Barbara Baker said Wednesday that a feeding tube was being implanted because the calf hasn’t been eating.

The zoo said earlier that the next 24 to 48 hours will be crucial for the survival of the still-unnamed baby elephant.

Officials say the baby’s mother, Seeni — one of three elephants the zoo rescued from Botswana in 2011 — hasn’t produced milk for her, forcing the zoo to feed her with a bottle.

The zoo said earlier that the baby elephant’s teething led to a diminished appetite, and the erratic eating pattern has caused her to stop gaining weight.