Table 1 Modifications of the herd structure according to the BR (batch-rearing) systems

BR systems (number of batches)

4

5

7

10

20

Total number of productive sows

192

245

203

430

620

Proportion of herds according to the BR system

0.12

0.21

0.48

0.10

0.09

Duration of a sow reproductive cycle (days)

140

140

147^a

140

140

Number of sows per batch

48

49

29

43

31

Number of piglets per batch

576

588

348

516

372

Interval between two successive batches of sows and pigs (days)

35

28

21

14

7

Number of batches in service room

1

2

2

3

5

Number of batches in gestating room

3

3

4

6

12

Number of farrowing rooms

1

1

2

2

4

Number of nursery rooms

2

2

2

4

7

Number of finishing rooms

3

4

6

9

18