Date: 2008-04-30
Number of pigs born per litter is directly affected by the physical condition of the sow when she was mated
Parity effects can distort the ability of feeding to restore the weight lost by a sow in lactation, but a poor rating on the condition-score scale needs to be corrected to avoid reducing the size of the next litter.
Last month, we told you about remarks to an international meeting in Denmark on the subject of managing the parity distribution of the breeding herd. Speakers had highlighted that rates of piglet mortality increase with the sow's parity. They also observed how the rising weight of the mature sow adds to her maintenance cost so a failure to replace animals soon enough may simply be wasting expensive feed.
The Danish symposium arranged by DanBred heard from Michael Groes Christiansen of national development agency Dansk Svineproduktion (DSP) that there are volumes of data to demonstrate that non-productive feed consumption in the breeding herd rises with increasing parities. This is due almost entirely to the sow's extra maintenance requirement linked to her greater weight, he commented, presenting Table 1 and Figure 1 to illustrate the point.
Figure 1: Sow feed per litter
Remarks about sow feeding programmes in Denmark were added at the meeting by Gunner Sorensen, also of DSP. In lactation feeding, he emphasised, the Danish recommendation is to set a maximum daily amount for the feed given to sows that are beyond Parity 3. Herd operators also are urged to aim for levels of feeding after weaning that will restore the weight lost by the sow during lactation and achieve an average of 15 kilograms gained by the time of the next farrowing.
On backfat thickness, the stated aim is for the measurement in a gilt to be between 12-18mm at first mating. A sow at the time of her transfer to the farrowing house should have 15-20mm of backfat, probably dropping to 14-18mm by the time she is weaned.
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Sows' increasing weight and maintenance requirement at higher parties make a substantial difference to the herd's annual feed usage.
Sows should be fed individually on the basis of their body condition, Mr Sorensen continued. Assess their condition at farrowing, at weaning and 3 times in gestation — after 1, 2 and 3 months of pregnancy. A point to remember with group housing systems is that gilts and low-ranking sows will need their own feed curve giving them an extra amount daily on arrival, to compensate for a less regulated climate in their surroundings.
Figure 2: Sow body condition affects total pigs born per litter
Managing the body condition of the sow from weaning into gestation can prevent problems at farrowing time, he told the symposium. Her condition when she is mated will be an important influence on the total number of pigs in the next litter (Figure 2). There is an equally important parity effect on the restoration of weight lost in lactation, however. Compared with the young sow, older sows in the herd need 25% more feed per kilogram of gain. PIGI