Genetic advancement relies heavily on information. Researchers first must identify and isolate a gene for certain traits, before they can select for those traits.
"The most important area in genetics today is discovering individual genes that control economic traits of interest," says Max Rothschild, Iowa State University geneticist and U.S. pig genome project coordinator.
Rothschild says some of this technology is already being used to impact production, citing reduction of the porcine stress gene and increase in litter size as examples. The future will hold more of this. For example, Rothschild believes the industry will see a reduction in the negative form of the Napole (or Rn) gene within the next year or so.
These breakthroughs may be only the tip of the iceberg. "I predict that the rate at which genes are discovered will start increasing," says Rothschild. Here's an example of some projects in the works at Iowa State
- A study is underway involving the Berkshire and Yorkshire breed effects on meat quality. Researchers are looking at the regions in the genome that affect meat quality, specifically: pH, water-holding capacity, tenderness and more. Six genetic companies as well as the National Pork Producers Council and the Iowa Pork Producers Association are cooperating in the study.
- A $700,000 multi-state, multi-institution grant is targeted for gene sequencing. Researchers hope to find 20,000 to 30,000 pieces of genes and then prioritize these to map out some 2,000 new genes. Reproductive genes will be the focus. The two-year project will start this fall.
- An ongoing project is developing practical on-farm programs to optimize selection for genes.
- Researchers are looking for genes that deal with feed efficiency, particularly feed intake as it relates to appetite. Some gene mutations in humans and mice can cause severe obesity. The theory researchers are investigating is if you can genetically select sows for feed intake, for example, you can better control body condition.
Further down the line Rothschild sees genetic efforts to reduce manure. Early signs of this come from Canada where researchers have created a genetically engineered pig that produces manure with lower phosphorus levels than "normal" pigs. This was achieved by transferring one gene from bacteria and another from mice into pigs, allowing the pigs to extract more phosphorous from their rations.
For now, here is a snapshot of some current research that may impact production on your operation today or sometime in the future.
Ultrasound Part of Heat Detection's Future
Ultrasound technology has long been used to monitor human pregnancies, so if the technology applies there, why not with sows and gilts?
University of Missouri researchers have been using ultrasound to check for ovulation in sows and for ovary examination.
"It used to be difficult to understand what was happening in the ovaries of a pig because you couldn't palpate. If the sow didn't come in to heat, you didn't know why," says Matt Lucy, University of Missouri animal scientist. "Ultrasound gives producers an option to understand what's happening inside the sow."
Lucy and colleagues Tim Safranski, Bill Lamberson, and Cynthia Bracken say ultrasound has been very accurate and it conserves time. However, the equipment is expensive and the practice remains a few years away from being practical for most producers.
"Operations with 600 sows can pay for a machine by pregnancy checking," says Safranski. "But then everybody who uses ultrasound for pregnancy diagnosis say it makes them a better heat checker, and detecting that second heat is where the machine really pays for itself."
While the scientists say these new techniques have great potential as a diagnostic tool, they're not ready to use as a production tool just yet. You should not attempt the heat-checking procedure without proper training.
For heat checking, the readings are taken rectally. The probe is attached to a one-inch plastic PVC pipe that's 24 to 26 inches long. The pipe has a 40 to 45 degree angle located 3 to 4 inches from one end and a 20-inch long 1/2-inch wide groove for the probe head and cord cut from the angled end.
The probe is attached to the handle by standard 1-inch wide athletic tape. It is lubricated before inserting into the gilt.
The Missouri research team uses an Aloka 500V ultrasound machine and a 7.5 MHz linear probe.
Bracken recommends placing a scoop of feed at the front of the restraining crate and allowing the gilt to enter on her own.
Gently insert the probe into the gilt's rectum with the probe head facing down. This may or may not stimulate the animal to defecate. If not, the feces will need to be removed in order to get a good ultrasound image.
It is important to insert the probe slowly and gently to avoid tearing the rectal wall. If the rectal wall is perforated, peritonitis will develop and kill the gilt within two or three days.
After you've inserted the probe, slide it over the pelvic bone and locate the bladder, which will appear as a large black circular structure on the ultrasound screen. To locate the ovaries turn the handle so the probe sweeps across the area on either side of the bladder. The ovaries are most easily detected when healthy follicular development is present. Follicles will appear as a cluster of small black circles on the ovary's surface.
If the gilt is cystic, the ovary will be covered with large follicles that may cover the whole ultrasound screen with a black honeycomb appearance.
It is not usually necessary to examine both ovaries as development is generally the same. Looking at just one ovary, you can check about 25 animals in an hour, or about one every 2 minutes if they are in crates, according to Bracken. Again, this is not a procedure you should try without training.
So far, there are only a few machines that can use a probe to measure backfat as well as convert to pregnancy and ovulation checking. These machines tend to be even more expensive than those with a single use. In the future, the machines may become cheaper or more versatile, and therefore a more practical production tool.
UNCOVERING TELL-TALE SIGNS
|Type of ovary||Ultrasound appearance|
|Type I Anestrus||Numerous small follicles|
|Type II Anestrus||Numerous small follicles 2 to 5 mm diameter. Flaccid cervix.|
|Estrus||Turgid cervix, follicles 7 to 8 mm diameter, few small follicles.|
|Near ovulation||Less turid cervix. Triangular follicles, 7 to 8 mm diameter, few small folicles.|
|Recently ovulated||Less turgid cervix. Ovary without follicles, may see developing Corpora lutea.|
|Ovulated >3 days ago||Corpora lutea with some small follicles (2 to 3 mm). Flaccid cervix.|
|Cystic||15 to 30 mm follicles. May also have Corpora lutea. Flaccid cervix.|
Source: Matt Lucy, University of Missouri
ESR Gene Effects Expand
It's well known that the estrogen receptor gene can have a positive effect on litter size. Now, the same is holding true for reproductive traits.
"Early trends show that with the ESR gene, more fetuses survive to become pigs, a sow's uterus is longer and heavier, and the ovulation rate increases," says Keith Irvin, Ohio State University animal scientist. "These are all important components in determining a sow's reproductive ability."
Irvin says results look promising, but he needs to collect more data to form definite conclusions. One drawback is that the data collection process is slow and tedious. Here's the
routine. Once a sow's DNA is genetically identified and she is bred, she is slaughtered 75 days into gestation. Then Irvin removes and evaluates the sow's reproductive tract.
In his study, Irvin used 107 sows with two, one or no ESR genes in their DNA. He collected data on ovulation rate, uterine-horn length, number of fetuses, fetal mass, uterine mass, number of mummies, fetal sex, fetal placement, fetal survival and fetal space.
Results show that the beneficial form of the ESR gene had a positive impact on fetal survival, uterine length, total fetal weight, number of mummies, fetuses per horn, horn length and fetal space. Again, Irvin stresses that more studies are needed before the results can have statistical significance.
If more tests show that the ESR gene is economically beneficial, Irvin says you may be able to use it as a selection tool.
Currently, testing a sow's DNA involves collecting a blood sample and having it analyzed at a genetics lab. Some easier methods are being studied, such as collecting a DNA sample from clipped tails or ear notches.
Iowa State geneticist Max Rothschild originally discovered the ESR in 1991. His studies, based on nearly 10,000 litter records, show that by selecting for the ESR gene, you can improve your litter size by 0.5 to 1 pig per litter.
In addition, Rothschild's work on the ESR gene was chosen for a national R&D 100 award. Criteria for the award, given by R&D magazine, is based on the idea, its invention and its uses.
Sperm Sexing Speeds Up
It's not available yet, but technology that will let you choose the sex of pig litters is advancing rapidly. That means producing all-gilt market hog groups that produce lean, meaty carcasses is closer to becoming a reality.
Lawrence Johnson, head of the Germplasm and Gamete Physiology Laboratory at USDA's Agricultural Research Service in Beltsville, Md., has improved the sexed sperm sorting technology he invented about 10 years ago.
"We have been able to increase our sorting speed by 15 to 20 times," Johnson says. "Now we can sort about 12 million X (male) and Y (female) sperm in an hour." Of course, that's still short of what's needed in a single artificial insemination semen dose.
To sort the male sperm from the female sperm, Johnson uses a fluorescent dye that sticks to the sperm's DNA. The dye binds to the sperm based on how much DNA the X and Y chromosomes are carrying. For example, male sperm carry about 3.6 percent more DNA in the X chromosome than in the Y.
Johnson can sort sperm faster now because he and his colleagues developed a new nozzle that attaches to the cell sorter that helps orient and sort the sperm. He also is using a higher-speed cell sorter. His accuracy runs between 90 percent to 100 percent.
In a recent experiment, eight litters of pigs were born using sorted female-chromosome sperm. Pigs in the eight litters were 98 percent female.
Still, the increased sorting speed isn't enough for commercial artificial insemination use in swine. A single AI semen dose contains 2 billion to 3 billion sperm, and most of you use more than one dose per sow. For now, most pigs born from sexed sperm come from sows implanted with in-vitro fertilized embryos.
Research is underway to bring the technology closer to everyday use. Johnson says researchers in his laboratory and elsewhere are working to determine how few sperm can be used to produce a pregnancy. If fewer can be used, artificial insemination using sorted semen might be more viable. Other researchers are looking at devices and methods to improve insemination by delivering the semen to the best location inside the sow.
Johnson's colleagues at ARS also are working on improving technology to freeze embryos. That could aid the entire embryo collection and transfer process and, again, would promote the use of sexed sperm – in this case, sexed embryos.
Johnson is optimistic that both of these technologies soon can advance to the point of commercial use. "If work progresses, we might be there in two to three years," he says.
Keeping Nature in Artificial Insemination
Although sperm still play the key role in impregnating sows, they need some help to do their job. Researchers are discovering that what enters the sow along with sperm also is important.
Kevin Rozeboom, North Carolina State University animal scientist, is studying the uterine inflammation that occurs in sows immediately after being bred and how that affects breeding success. He's found that having enough seminal plasma – everything in semen except the sperm – can minimize harmful inflammation and give the sperm some time to hit its mark.
"Post-breeding uterine inflammation appears to be an important method of clearing out the uterus and getting it ready to implant fertilized eggs – if it's properly regulated by seminal plasma," Rozeboom says.
The idea is that you can't take all of nature out of breeding – natural mating involves seminal plasma and uterine inflammation. The potential problem involves today's artificial insemination practices: when semen is extended into individual doses, seminal plasma can actually become diluted to a point where it can't do its job.
"When semen is extensively diluted, it appears to make the uterine inflammatory response bigger," Rozeboom says. That can negatively affect subsequent inseminations and embryo survivability.
In one experiment, for example, one set of females received extended boar semen containing no seminal plasma while another group was inseminated with sperm suspended in seminal plasma. Both sets had inflamed uteruses prior to the experimental insemination. Farrowing rates were about 30 percent higher in the group receiving the seminal plasma.
AI doses timed late in the cycle also can cause reproductive problems because of the inflammation process. Late inseminations caused a 20 percent drop in farrowing rate in first- and second-parity females. It also dropped the average litter size by 1.1 pigs per litter in females that actually farrowed.
"We've found that the sow can't clean out the uterus in time, and you're affecting embryo preparation," Rozeboom says. "But when sufficient plasma is in the semen dose, it actually speeds up the uterus clearance, and gives producers a little cushion."
Rozeboom's first advice is to work on heat detection – try to understand your herd's estrual behavior. Secondly, consider more than just sperm numbers when you're extending semen into doses. Take into account the percent of seminal plasma that will be present in each dose once it's extended. Rozeboom's research indicates each dose should contain about 12 percent seminal plasma.
Let's say you have 50 billion sperm in 100 milliliters of the ejaculate with which you're working. Normally, you could extend that into 20 AI doses to get a typical sperm count of 2.5 billion sperm per dose. But don't forget to consider the plasma: each of those doses would then only contain about 5 percent of the seminal plasma. Keeping it as close to 12 percent as possible will help fertility.
"Especially watch if your boars produce a lot of sperm with little volume, because the dilution could make the plasma percentage farther off," he says.