What is the best method for culling and replacing breeding pigs?
Breeding pigs are the foundation of herd multiplication and the core of the entire pig production operation. Since breeding pigs have a limited service life - in natural mating, boars generally do not exceed 2 years and sows do not exceed 8 litters, while boars used for semen collection serve 3~4 years and sows do not exceed 8 litters - and because production performance varies greatly between individual breeding pigs, only by implementing a scientific and reasonable system for culling and replacing breeding pigs can the production level of the breeding herd be maintained or improved, thereby increasing the economic returns of the pig farm. So how should breeding pigs be culled and replaced?
Calculate the relevant data for culling and replacing breeding pigs
Taking 100 foundation sows as an example, with a farrowing index of 2.3, the calculation is as follows:
Boars: under natural mating conditions, the boar-to-sow ratio generally should not exceed 1:20, so 100 foundation sows require 100÷20=5 boars. The annual replacement number is 5÷2=2.5 boars (that is, 2~3 boars replaced per year).
Sows: based on 8 litters per productive lifetime and 2.3 litters per sow per year, the average service life of a sow is 8÷2.3=3.48≈3.5 years. The annual culling rate is 1÷3.5×100%=28.6%≈30%.
For a pig farm with 100 foundation sows, the annual number to be culled and replaced is 100×30%=30 head, and the monthly number to be culled and replaced is 30÷12=2.5 head (for large-scale pig farms, the weekly number to be culled and replaced should also be calculated).
Replace according to the general principles for culling breeding pigs
The above figures are theoretical calculated values; in actual practice, breeding pigs should be culled and replaced according to the following principles.
Principles for culling sows:
1. Cull replacement gilts that have reached the breeding standard in age and weight but have not come into estrus after being kept for another 2~3 estrous cycles.
2. Cull sows confirmed not to be in estrus 60 days after weaning.
3. Cull sows that have returned to estrus 3~4 times in a row.
4. Cull sows that have fewer than 6 piglets born alive in 2 consecutive litters, or that have many stillborn and weak piglets, or that produce uneven litters.
5. Cull sows with fewer than 6 pairs of teats, abnormally developed teats, inverted teats, blind teats or supernumerary teats, or poor milk production.
6. Cull sows with poor mothering ability, vicious habits, or a low nursing rate.
7. Cull sows that eat slowly, are overweight or overheavy in body, move sluggishly, have dull skin, or have lackluster eyes.
8. Cull sows that produce deformed offspring.
9. Cull sows that are diseased or disabled, are relatively old, or have declining production performance.
Principles for culling boars: generally culling is based on the service life limit, but boars that are clumsy in body, have poor semen quality, unsatisfactory mating results, or a vicious temperament should also be culled promptly.
Vacancies left after culling should be filled at any time with ideal replacement breeding pigs.