Identifying the true value of effective replacement gilt

It has long been our view that improvements in gilt development programs can lead to major improvements in breeding herd efficiency. Whether gilts are reared in ‘in-house’ gilt multiplication systems, or supplied by a breeding company, available data suggest that the proper selection and management of replacement gilts has an impact on lifetime non-productive days (NPD). As discussed later, we have been accumulating data to support this view. However, the “true value” of improved management of replacement gilts goes well beyond a simple consideration of NPD. In a recent presentation at the Red Deer Swine Technical workshop, the audience was reminded that PigChamp 2002 data shows that on Canadian farms with an average herd female inventory is 1,046 (range 240-2,740), the an average replacement rate was 58.7% (range 33.4-74.4%). It is not unusual to see replacement rates of over 60% on larger production systems. An excessively large pool of replacement gilts is needed to meet these replacement requirements. Apart from the extra costs of maintaining a large gilt pool, the bias of production towards lower parity females places major constraints on breeding herd performance. The usual observation would be that the individual productivity of the gilts introduced into the breeding herd declines as the size of the gilt pool relative to gilt breeding targets increases. As a result, there is continual over-breeding to meet production targets of weaned pigs shipped to the nurseries, in turn leading to chronic over-crowding of pens in the gilt development area.