Extension Notebook: Reaching for genetic and reproductive efficiency in pigs

The modern pig in breeding herds around the world has been managed to reach some of the highest levels of reproductive performance among all livestock species. While variation occurs in key reproductive measures in response to changes in health, environment, genotype and many other factors, most farms still have expectations for reaching an 84% farrowing rate and producing a litter of 13 or more live pigs more than twice a year. In essence, the target is for farms to wean an average of 24 or more pigs for each sow each year.

Today, some farms — and countries for that matter — far exceed this target which helps to illustrate the pig’s fertility potential. Farms around the world are aware of this expectation and use this to gauge the likelihood of profitability and ability to compete.

This level of fertility results from the near exclusive use of artificial insemination for breeding swine with growing international interest in advanced AI technologies such as single (S) or fixed time (FT) artificial insemination (AI). The modern swine industry has been quite open to use of new technology to increase genetic progress, address challenges in labor and performance, and provide improved consistency in fertility throughout the year. The greatest economic driver for SFTAI is increasing the introduction of economically valuable genes. Since AI is the most efficient and biosecure method for widespread genetic improvement, increased use and distribution of high indexing sire genes is the goal.

Without going into great detail, the concept is to use a single instead of a double insemination to produce a litter of pigs. This would enable a boar to sire 24 litters a week and produce nearly 15,000 pigs a year each having his elite genes. With improvements in pig growth efficiency, carcass traits and live pig production, the economic value would be considerable. But from a practical perspective, a SFTAI system would require years to develop the hierarchy for the sire genetics to meet the needs of the commercial industry. In fact, to minimize the risk of low pig production resulting from one poor fertility sire, many of the pigs produced around the world actually originate from a pool of sires of the same breed and genetic index. Regardless, some farm systems require or use single sire matings with FTAI as an approach to reduce variation in fertility.

The source of fertility variation starts when sow breeding groups are established after pigs are weaned on a single day of the week. On small farms group size may include tens of sows while on larger farms can exceed hundreds of females a week. Breeding herd labor must work to identify all sows in estrus using boar exposure throughout the week. It is expected that 85% of sows will be detected in estrus and inseminated three to six days after weaning. This spread in days results in sows conceiving over a four-day period which does affect sow fertility, AI quality, labor and day of farrowing. Collectively, these factors impact live pig production.

Around the world, FTAI models utilize induced ovulation and single or multiple inseminations. What this is intended to accomplish is to improve precision breeding with limited variation in fertilization and farrowing days. In the last decade, research and commercial application of FTAI on farms has shown that it is possible to reach fertility targets when compared to conventional breeding methods.

But the technology has come with challenges and risks and requires a new paradigm for fertility assessment. With FTAI, most sows are assigned for induction and breeding independent of fertility. Farms with relatively high sow fertility and limited variation in weaning to estrus intervals easily reach their goals of breeding on a single day of the week with improvement or no change in the numbers of litters produced. Other farms experience greater variation in days to estrus and infertility and notice that FTAI results in more sows bred than produce a litter. But in reality, the numbers of litters produced are the same as with conventional breeding. In fact how infertile sows are maintained on farms is not very different among the breeding systems as most farms do not identify non-pregnant sows for rebreeding until three to four weeks.

So a paradigm shift arises from how fertility is calculated for farrowing rate based only on sows in estrus and inseminated while FTAI calculates sow utilization rate based on all available sows weaned and inseminated that farrow. In the end, the number of litters produced often favors FTAI, and the number of infertile sows and the number of days they are maintained on the farm are not changed.

So, in essence, the major problem for a FTAI program is inducing and breeding infertile females which is inefficient and does add costs. Some approaches to address this issue have included fertility induction at weaning, identifying pro-estrus females or estrus females for FTAI. But these are likely to only have limited effect and could in fact be detrimental. Perhaps the best approach is to use a test to identify infertile females and classify them as ineligible.

At the present time in the U.S., very few commercial farms are using FTAI, while use on smaller exhibition farms is evident. This discrepancy likely reflects differences in how animals are bred for show versus commercial production throughout the year.

Yet what has been of notice is the interest in application and development of the FTAI technology in major pork production countries such as Brazil, China and Thailand. On the plus side, interest could stem from recognized economic advantages in productivity, labor, and sow utilization, while on the minus side, could arise from over-sold or unrealistic expectations of technology.

It will be of interest to follow, as certain breeding technologies introduced in the U.S. were initially abandoned, only to appear in foreign countries a few years later with considerable success. And in the U.S., the second time around is a charm, as the “new” technology gains traction and then becomes a tool for driving industry advancement.

Robert V. Knox is a Swine Extension Specialist, University of Illinois Champaign-Urbana.