Editor’s note: Information in this article was presented as part of an “Optimizing Reproductive Efficiency” seminar at this year’s AASV meeting in Toronto.

Can 30 weaned pigs per mated female per year  (wp/mf/y) be achieved consistently?

“There is no doubt that basic principles need to be applied when achieving 30 weaned pigs per mated female per year,” says swine reproductive expert Donald G.  Levis, PhD, with the University of Nebraska.


It takes planning and hard work, but 30 weaned pigs per mated female per year is achievable.

“It is essential that a high level of excellence be utilized when planning, implementing and managing genetics, nutrition, health, housing, reproduction, and environment,” says Levis. “Also, interactions occur among these factors.”

Levis says that much new technology has been developed that can help you help clients to produce 30 wp/mf/y. “However, one needs to proceed cautiously when adopting ‘state‑of‑the‑art, cutting‑edge’ technology.”

You need to be certain that the technologies being adopted by your clients have been scientifically tested with an excellent experimental design, according to Levis. “There is little room for error when producing a high number of wp/mf/y,” Levis says. Further, he emphasizes, the application of one new technology, per se, likely will not be enough.

Stock people training
All the technology in the world will not help unless “workers are knowledgeable, motivated and dedicated to making the new technology work,” according to Levis.

And, improving stockmanship in a given pig production systems depends on the specific situation, Levis says. For example, some workers in one production system may need to learn more about animal requirements, while in another system, the workers may need to be trained in specific skills.

In another system, motivation and/or job dissatisfaction may be deficiencies that need correcting.

Technology application

Levis discusses the following technologies that are currently being touted as methods to improve reproductive efficiency.

  • Long‑term semen extenders. The basic role of semen extenders has not changed since their inception, he explains. “Extenders are still used to increase the total volume of diluted sperm cells, provide an adequate supply of nutrients for sperm cell metabolism, provide an environment to protect the sperm cells against rapid cooling, provide buffers to protect sperm cells against extreme shifts in pH, provide electrolytes for proper osmotic pressure and provide antibiotics to inhibit bacterial growth.

    “Storage of sperm cells in seminal plasma by itself does not permit a long preservation of spermatozoa. Therefore, a suitable medium has to be added to the sperm in order to prolong their survival and to maintain their ability to fertilize ova.”

    Take care when conducting an experiment to evaluate the true effect of a specific boar semen extender on farrowing rate and litter size, says Levis. At the same time, “there is no guarantee that the results of the experiment will be the same across time,” he says, pointing to a 2001 study that found the advantages of one extender over another for farrowing rate and litter size changed over time.


    New AI technology, such as auto insemination devices, requires workers with high skills and AI knowledge, plus close supervision.

    Levis’ take home messages regarding the use of long-term semen extenders:

  • “If you and your clients are satisfied with the performance of your current extender, is there any valid reason why you would want to change extenders? If it is not broke, why fix it?”
  • Research has shown that “although sperm cells can have a high motility score at four to seven days after collection, the ability of the sperm cells to attach to the ova is diminished, compared with sperm cells 0 to 3 days of age. The use of long‑term boar semen extenders will not enhance farrowing rate or litter size compared to using fresh extended semen within three days of collection.”
  • Intrauterine body catheter. Some of the claimed advantages for the intrauterine insemination procedure, says Levis, include: Less back‑flow during and after insemination; fewer sperm cells per dose; a smaller volume of semen; less time to infuse semen after placing the catheter into the uterine body; paternal genetic cost will be lower per dose because fewer sperm cells are inseminated; and, as a result of fewer sperm cells per dose, fewer boars will be needed to produce superior semen.

    Levis points to research in 2004 that evaluated the effect of type of catheter (intrauterine versus cervical) on reproductive performance of sows when using 4 billion sperm cells per dose (see accompanying table).

    “The use of an intrauterine catheter did not significantly increase farrowing rate, average total piglets born per litter or average total live piglets born per litter. Although the fecundity index (farrowing rate x average piglets born live per litter) was numerically higher for the sows inseminated with the intrauterine catheter, there was no economic advantage for using the intrauterine catheter (see table).

    Even though several new catheters have been introduced to the market, Levis says scientific studies on these have been limited to date.


    Automated feeding systems for sows can help produce more pigs because they free workers to spend more time with newborn piglets.

    His take home message: “Without excellent management, the use of intrauterine catheters, per se, will not help a pork producer obtain 30 wp/mf/y. The intrauterine catheter did not perform significantly better than a cervical catheter.”

  • Deep intrauterine horn catheter. Scientists in Spain have evaluated a specifically designed flexible catheter (70 inches long) that is inserted through a traditional spirette catheter and passed through the cervix and moved forward along one uterine horn until its total length has been inserted to about the middle of the uterine horn.

    "In this study, crossbred sows were treated with 1,250 IU equine chorionic gonadotrophin (eCG) 24 hours after weaning and with 750 IU of human chorionic gonadotrophin (hCG) 72 hours after eCG. Deep intrauterine horn insemination (DIUHI) was performed once at 36 hours after hCG treatment with 150 million, 50 million, 25 million or 10 million sperm cells in 10 mL.

    Control sows were cervical inseminated twice with 3 billion sperm cells in 100 mL. Farrowing rate after DIUHI with 150 million or 50 million sperm cells did not differ from the control group.

    However, farrowing rate was less (P < .001) after DIUHI with 25 million or 10 million sperm cells compared with control sows. Although litter size born was not significantly different between treatments, litter size was numerically smaller for sows inseminated with 10 million, 25 million, 50 million or 150 million sperm cells compared with sows inseminated with a cervical catheter and 3 billion sperm cells.

    The take home message: “At this point in time, the technology of placing semen deep into the uterine horn of non‑sedated sows is not commercially available.”

  • Stimulating reproductive tract. Levis says that a European company has developed a vibrator for pigs that, it is suggested, can stimulate the sow’s reproductive tract to transport sperm cells to the oviduct.

    Levis’ take home message: “There is no reliable data to suggest that the stimulation of the sow’s reproductive tract will enhance reproductive performance. A scientifically controlled study with a large number of sows per treatment needs to be conducted to determine the true effect of technology such as this on reproductive performance.”

  • Auto insemination. Use of such devices claim to be all-in-one concepts that enable auto-insemination by reducing AI to a single act. Levis says that some research seems to indicate that this technology might improve farrowing rate and litter size on farms that have low productive performance to begin with.

    His take home message: This technology, per se, will not enhance the ability to achieve 30 wp/mf/y. Using this technology requires workers with a high level of AI knowledge and skill, plus close supervision.

  • Hands‑free AI devices. Although a limited number of scientific studies have been published on the effect of  “hands‑free” insemination devices on farrowing rate and litter size, several hands‑free devices are marketed.

    Levis’ take home message: Hands‑free insemination devices can be used successfully under close supervision, but these devices by themselves will not enhance the ability to achieve 30 wp/mf/y.

  • Omega‑3 fatty acids. A literature review in 2003 suggests that omega‑3 fatty acids may, or may not, influence reproductive performance of sows. “Most of the few studies published on the effect of omega‑3 fatty acids on boar fertility are from one company with patent rights to a product, thus it is unclear which components of the diet are enhancing boar fertility,” says Levis.

    “Given the body of information available about omega‑3 fatty acids in human and pets, it is becoming evident that the decision to add fat or oil to sow and boar diets should be based on more than just an energy source consideration.

    “However, until results from studies that involve hundreds of sows and/or boars fed corn and soybean meal‑based diets supplemented with omega‑3 fatty acids are published, it is difficult to establish the economic value of omega‑3 fatty acid supplements.

    Levis’ take home message:  Additional research is needed to clarify: 1) the optimum amount of omega‑3 fatty acids to add to sow and boar diets, 2) which aspects of the sow reproductive cycle should omega‑3 fatty acids be provided to enhance reproductive performance and piglet survival, and 3) the preferred sources of omega‑3 fatty acids.

  • Automated feeding. Several sow farms have adopted the use of an automated feeding system in the farrowing facility. These systems can be very successful when properly managed, says Levis. The advantages include  “fresh” feed is frequently provided during a 24‑hour period, reduced labor for feeding and more time available for working with the litters, especially during the piglet’s first 24 hours of life.

    Levis’ take home message: Because workers can spend more time working with newborn piglets, there is a potential to increase the number of piglets weaned per litter.

  • Sexed boar semen. Although research has shown that X and Y boar spermatozoa can be successfully separated on DNA content, Levis believes that the commercial application of sexed semen on a large number of sows still is several years away.

    “At this point in time, farrowing rate and litter size is unacceptable,” he says. “As with any new reproductive technology, the use of sexed semen will depend on efficiency, economics, effectiveness, and ease of use.”

    Levis adds that for commercial introduction of flow‑sorted sexed semen, new instrumentation and procedures must provide a greater sort rate, adequate viability of spermatozoa during transportation, long‑term storage that is equal to the current storage time of liquid extended semen, a method to inseminate females with a smaller volume and lesser number of sperm cells, and a product that produces an adequate farrowing rate and litter size.

    “Undoubtedly, the cost of sexed semen will be greater as compared with non-sorted semen, thus, only high‑value sexed sperm cells should be marketed.”

    Levis’ take home message: The use of sexed semen will not help pork producers obtain 30 wp/mf/y.


All the technology in the world will not help produce a lot of pigs without knowledgeable, dedicated and motivated workers.

12 Factors For Getting 30 Weaned Pigs Per Mated Female Per Year

Nebraska swine reproductive expert Don Levis emphasizes that your clients need to pay close attention to the following 12 areas in order for their pigs to consistently achieve an average of 30 weaned pigs per mated female per year:

1. Use of high quality semen for insemination.

2. Sows and gilts that ovulate a high number of ova.

3. A high percentage of the ova are fertilized.

4. A high number of embryos implanted into the uterus.

5. A high survival rate of the implanted embryos.

6. A high number of piglets born alive.

7. Sows and gilts should have an adequate number of functional nipples.

8. An adequate supply of milk should be provided to all nursing piglets.

9. Pre-weaning survival of piglets should be high.

10. An adequate lactation length should be utilized.

11. The weaning‑to‑estrus interval needs to be low.

12. Farrowing rate is high.


Levis concludes that in addition, a key role is “the ability and skills of people.”