By Doug Newcom, National Swine Registry vice president of genetics and technology
Whether you’re a seedstock swine producer, a commercial pork producer with internal multiplication, or a farmer purchasing your own breeding stock, here are four steps to implement on your farm (or to expect from your supplier) to facilitate genetic improvement.
In theory, the principle of genetic improvement is quite simple: select the best individuals to retain as parents in your herd and disseminate their genes through the system as quickly as possible. In addition, you must remove those genetically inferior animals from the gene pool equally as fast. But, as the saying goes, “The devil is in the details.”
1. Identify Your Destination
Defining “the best” is generally the first step. Whether they be purebred breeders or breeding stock companies, defining “the best” is where a large percentage of time is spent. Determine your destination, or where your genetics need to be in the future. Understanding that genetic decisions you make today won’t end up on a consumer’s plate for three to five years is critical. I had a former classmate once say that if you want immediate changes to your production or performance, seek advice from a veterinarian, nutritionist or your chosen religious deity. Genetic change takes a while.
2. Lay Out Your Roadmap
Once you have your destination, laying out the roadmap to get there becomes a priority. The basis of most genetic programs is the idea of economic values, or the relative importance of any single trait to the profitability of a farm. To change traits in the desired direction, sufficient emphasis must be placed on those traits in your selection program. Selecting to improve only a single trait is generally never recommended, due to the ramifications in other economically important traits. Selection indexes were developed to facilitate genetic improvement in multiple traits at the same time. Index values are calculated utilizing our economic values for each trait and the level of genetic merit for each trait.
Estimates of genetic merit, or the Estimated Breeding Value (EBV), for each trait of interest are calculated utilizing all available relevant information for an individual: pedigree, performance data, ancestral data, and more recently, genotypic data (also called gene marker data or SNP data).
Traditional genetic improvement programs have been very effective in determining the true genetic merit of an individual for traits expressed in both genders early in life and highly controlled by genetics. However, to make genetic improvement in traits more greatly impacted by the environment or traits that were only measured in one gender or late in life, large population sizes and vast amounts of performance data were needed.
By looking at the gene-marker make-up of an individual, estimates of genetic merit for these traits could be more accurately determined early in life. Whole-herd reporting or whole-herd performance testing is still a necessity, and additional data sources like commercial performance testing only add to the accuracy of your estimates of genetic merit. By utilizing all available information in the estimates of genetic merit and properly weighing each of these EBV with real-world economic factors, the genetic merit of an individual can be narrowed down to a single value – their (selection) index.
3. Identify the Best and Worst
Once each animal has an index, the rubber really meets the road. There are multiple points in the production cycle where index values are utilized to make decisions about retaining genetically superior individuals and removing genetically inferior ones. Selection (deciding which gilts to put back in the herd or boars into stud), mating, birth, castration and weaning are different times where index values are utilized.
Before making genetic decisions at each of these points, make sure you have the most current index values, based on all the information available at the time. I will add the disclaimer that the following scenarios start with a phenotypic appraisal of individuals to ensure proper skeleton, feet, leg, and reproductive indicators (underline, vulva, testes) – only animals meeting these criteria are available to reproduce. Also, pay close attention to inbreeding, or the relatedness between individuals. Selecting animals of slightly lower genetic merit to maintain genetic diversity is not only acceptable, but necessary.
4. Keep the Best
At selection, animals with the highest genetic merit should be retained for breeding. The number retained depends on your herd size and how intensely you wish to select. When these animals enter the herd, lower merit boars and sows must be culled at a similar rate. Bringing in genetically superior animals, but still reproducing with genetically inferior ones, will slow your rate of genetic improvement. Once animals are in the herd, mate them in a way to maximize the rate of genetic improvement while maintaining an acceptable level of inbreeding. Most genetic providers have this technology available.
When litters are born, you may not be in a situation to performance test all the boars. If so, you may need to make castration decisions. Using the average index value of the parents will help determine which litters to retain boars for testing. It is highly recommended that all pigs in a litter are performance tested, even if a portion of them are barrows.
At weaning, sows need to be classified in one of three categories: breed for purebred replacements, breed to make F1 females (or commercial boars for terminal sows) or culled. At this point in the cycle, you are bringing in those genetically superior females again. The same goes for boars in your stud. They are first used to sire purebred replacements. Once they have sired “enough,” but not too many purebred litters, they can be relegated to making F1 females for maternal boars, or market hogs in the case of terminal boars.
Although this doesn’t begin to encompass everything that goes into genetic improvement, the principle of genetic improvement is quite easy. Just remember the devil is indeed in the details. Identify your destination. Lay out your roadmap. Identify the best and worst in the population. And, at every step in the production cycle, take the opportunity to keep the best and remove the worst.
Read More:
Unleash Genetic Potential Through Careful Management
How One Student is Using Image Analysis to Increase the Genetic Potential of Pigs
Heritability of Pelvic Organ Prolapse in Sows is Higher Than Previously Thought
The Wild Wild West of Carbon Markets: Where Do Swine Genetics Fit?
