Table 2 Distribution of performed and positive bioassays according to specific antibody level in pigs

25

50

100

200

400

800

1600

3200

6400

12800

9

11

1

6

7

4

3

2

0

2

45

-

3

1

4

6

3

3

1

-

1

22

-

1

1

2

5^a

3

2^b

1^c

-

1^c

16