The 11 zebras that died in Bangabandhu Sheikh Mujib Safari Park in Gazipur in recent times suffered nitrate poisoning.
Dr Md Abu Hadi Noor Ali Khan, a professor of Pathology Department under Faculty of Veterinary Science at Bangladesh Agricultural University (BAU), also a member of the medical board formed to find the cause of the deaths of the animals, said.
Traces of excess nitrate were found in the samples from the deceased animals which were tested at the Pathology, Pharmacology and Toxicology Departments of BAU, the professor said.
The authority of the safari park had asked the animal food supply contractor to provide tender grasses instead of mature ones since December 18 last year, said the member of the medical board.
The presence of nitrate was higher than the normal limit in the tender grasses, making the zebras suffer from nitrate poisoning, said the BAU professor.
Later the animals were also infected with secondary bacteria, which accelerated the poisoning in their body causing pneumonia, resulting in the rapid deaths of the zebras, he said.
Explaining why the tender grass might have excess amount of nitrate, the professor said that many grass growers use high doses of urea for rapid growth. Urea contains nitrate which has a withdrawal period from the grass. That’s why tender grasses may contain high level of nitrate and if they are used before complete withdrawal, it might be very harmful for animals, Dr Khan added.
“We have suggested that mature grass be supplied to the animals after drying them for a day. There has been no report of any problem so far since January 29”, said the scientist.
The professor also said that the sample from the lioness who also died recently at the safari park, was tested at BAU laboratory and they found that the animal died of avian TB (tuberculosis).
The lioness got infected from birds served as food. The animal was sick for some six months but it is difficult to detect the TB in such an animal within short period, he added.
On the other hand, the sample from the recently deceased tiger was tested at Central Disease Investigation Laboratory in Dhaka and the report said it died of snthrax, said Dr Khan.