Introduction

The genetic selection of pigs is a very specialised and sophisticated business. Improvements in breeding backed up by other aspects of management have resulted in pigs which have a higher output of piglets per sow, and which are faster growing and produce leaner carcases. Attention is also focussed on genetic selection for meat quality.

In New Zealand the majority of pigs produced are sourced from one or both of the white breeds Large White and Landrace. These white lines are bred and undergo intensive selection to provide nucleus herds that are of high health status.

Only a few of the very top animals are selected and retained in the nucleus herd to produce the next generation. The remaining above average animals and culled sows are sold to the multipler herds (herds used for commercial reproduction). The multiplier herds then cross mate these pure lines to produce hybrid gilts for the commercial producers.

Commercial producers want hybrid or first cross sows because they have improved reproductive performance when compared to pure bred lines. This improved reproductive performance is measured by larger litters born and reared, better milking ability and better conception rates.