A Young Herd is the Most Productive18 February 2013
UK - A pig unit should aim for at least 45 per cent of sows to be in parities three to five, as these are the most productive animals. 20–25 per cent of production should be from gilts so it is important there are enough gilts available to serve.
To calculate the target annual replacement
rate, producers need to decide
what the target number of litters per
sow lifetime is, ie an average lifetime of
five parities. If the farrowing index is 2.33
litters per year, the whole herd turnover
is calculated as 5 / 2.33 = 2.15 years. So
target annual replacement rate will be
100 / 2.15 = 46.5 per cent.
Actual replacement rate is the number of served gilts introduced expressed as a per cent of the average herd size for the year.
Alternatively, multiply the average number of served gilts ( per cent of the herd) by the farrowing index, ie 20.5 per cent x 2.33 = 47.8 per cent. The higher the litters per sow per year and the lower target litters per lifetime, the higher the replacement rate will be. The cost implications also need to be monitored and evaluated.