Ten cases of bovine spongiform encephalopathy were confirmed in the national herd during September, according to the Department of Agriculture and Food.
This is one more than in the same month last year and brings the total since the beginning of the year to 57. In the same period last year (January-September), 49 cases were recorded.
The latest cases were found in Cavan (3), Cork (2), Meath (2) and one each in Cos Monaghan, Sligo and Clare.
Four of the animals were seven years old, two were six, three were five and one was four.
Veterinary experts believe the number of cases should fall sharply in the next two years when cattle which have not been exposed to meat and bonemeal feed mature.
Despite strict controls introduced in 1989, and in the following years, contamination of cattle feed continued until three years ago during milling operations.
When this was discovered, regulations were put in place banning the production of cattle feed in pig and poultry feed production mills.
A Department spokesman said the increase in the number of cases in September was in line with the experience in recent years, when the number tended to rise in the months of September, October and November.
The number of cases confirmed in the Republic since the disease was first identified here in 1989 now stands at 409.