Getting Your Genetics’ Worth

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With today’s highly efficient swine genetics, raising healthy, fast-growing pigs should be an easy outcome, right? Well, one researcher says the pork industry is still not getting the full genetic benefit for many reasons.

Among the priorities, there’s a need to review breeding-herd management strategies and practices, according to George Foxcroft, professor of swine reproductive physiology, University of Alberta. What has worked in the past may no longer be successful.

“We need to understand how quickly these animals are changing due to the genetic selection that is occurring,” Foxcroft says. “We are under-managing the genetics we have, and we are not yet up to speed on what they are capable of.”

An integrated, cost-benefit approach to breeding-herd management will be required to remain competitive and survive the next industry downturn, he says.

With pork production becoming a highly specialized technology, the priority will be to focus on key issues that impact efficiency. For example, gilt management techniques and artificial insemination strategies are two production areas that influence our ability to capture the potential inherent in the best animals.

Managing Gilts

Implementing an effective gilt development strategy is an important starting point. “Do not forget that good gilt development is your herd’s future,” Foxcroft says.

Replacement gilts should have adequate body condition, but not excessive, at breeding. “Our benchmark is that gilts have to be gaining at a rate of 1.12 pounds per day to stimulation to ensure that low growth performance is not limiting onset of first estrus; however, beyond this minimal growth requirement, there is no relationship between how quickly they grow and when they show first heat,” Foxcroft says.

Measuring or estimating weight before breeding and having records of standing heat are key issues of gilt management that we have to determine and neither occurs at a particular age, Foxcroft says. “An age requirement alone is not part of our management strategy.”

Breeding at second estrus usually produces measurable economic benefits. “It is important that we manage gilts to achieve heat within 21 days of first boar exposure and allow 21 days to get to second estrus,” he says. This is the “magic 42 days” promoted by colleagues in Chile. Foxcroft estimates that breeding at second estrus yields an increase of 0.7 pigs per litter. “No further significant advantage is obtained by delaying breeding past the second estrus, unless bodyweight is still too low,” Foxcroft says.

Gilts should weigh 300 to 350 pounds at breeding and 400 to 450 pounds at farrowing. “Gilts that weigh more than 350 pounds at breeding have an increased likelihood of developing foot and lameness problems, and that can lead to excessive culling,” Foxcroft notes. Worse yet, such issues can lead to reluctance to do necessary culling because there’s such pressure to keep barns full. This will be costly and less efficient in the long run.

Quality, Not Quantity

Genetic selection for increased litter size, and indirectly for high ovulation rates, has been common in recent years but it’s also why sow management requires more and different attention today. “High ovulation rates, particularly in higher parity sows, can actually create a problem,” Foxcroft says. “A crowded uterus early-on can affect the development of the litter and can cause low birthweight.” Lower-birthweight pigs cost more in feed to bring to market, and they are more vulnerable to setbacks.

Many genetics companies these days are already selecting on number of pigs born alive and not on total born, as well as on number of pigs weaned or number of pigs surviving to day 5 or day 12. “I would also like to see mean birthweight in mature sows taken into account,” Foxcroft notes. “Litter size for many mature sows already exceeds what is manageable.” He wants to see more emphasis placed on quality of litters rather than quantity — or litter size.          

One key to managing litters with lower birthweight is proper management of pig flows due to varying nutrition requirements. If the production system is big enough, you can flow the offspring into different nursery and grow/finish areas, feed different diets and have different finishing expectations. “The key to profitability may hinge on more effectively dealing with the variation in birthweights,” according to Foxcroft.

Managing sows with low litter-birthweight phenotypes can help with the economics involved. One strategy to lessen the high-ovulation and low-birthweight tendencies of present-day dam lines is to select boar lines with a high piglet survivability index. Another strategy would be to segregate sows based on expected litter birthweight, so that you can manage the sow and litter more specific to their needs. Feeding omega fatty acids to only those sows that are expected to produce low-birthweight litters could be another strategy that can produce better results.

Because of the epigenetic origins of low litter birthweight in mature sows, Foxcroft says it will take approximately 10 years to develop markers for these epigenetic traits and avoid the interactions of high ovulation rates and associated intra-uterine crowding in early gestation.“Ideally, we want to maintain litter size but remove sows from the genetic selection pool that have high ovulation rates and low litter-birthweight phenotypes.”

Is Your A.I. Program Helping?

Efficiency in your artificial insemination program is another topic worth close attention. Further advances in genetic gain will result from reducing A.I. semen doses. “We are being incredibly extravagant in the amount of semen we are using in A.I. programs,” Foxcroft says.

It has been estimated that there are approximately 35,000 boars at stud servicing the U.S. pork industry, Foxcroft notes. He believes that’s overkill, citing the fact that the dairy industry relies on far fewer sires for artificial insemination. “In the future, only the very best boars should produce the pork we put on the table,” he adds.

Further advances in pig production and genetic gain will come from improvements in A.I. and breeding by reducing the average number of semen doses per sow. With an average of 2.5 to 2.6 inseminations per breeding and a “gold standard” of 3 billion sperm per dose, Foxcroft estimates producers are using around 10 billion sperm per litter produced.

“To improve boar evaluation and to improve swine production, we first have to get that number down to around 1.5 billion to 2 billion sperm per dose,” he says. This step will make it easier to recognize and identify subfertile boars that should then be eliminated from the mix. By eliminating low-performing boars, Foxcroft estimates sow productivity could be improved by 2.4 pigs per sow per year.

Pooling boar semen may cause significant drawbacks as well, and it holds back the potential of genetic advancement. According to Foxcroft, up to half of the sperm in pooled semen often does not produce any pigs and serves only to dilute the productive sperm.

“We need to eliminate boars with limited reproductive capacity, reduce both number of inseminations per breeding and the number of sperm per dose and then select the higher-indexed boars and use them in lower numbers,” Foxcroft says. “By using individual boars, rather than pooling, and advanced A.I. technologies such as post-cervical A.I. and single, fixed-time insemination, we can probably go down to 1 billion to 1.5 billion sperm per litter born.”

“As an industry, we are not capturing maximum value available from our best animals,” Foxcroft says. “We have some exceptional animals and we need to use those genetics to their maximum.”

Remaining competitive in the pork industry may hinge on your ability to maximize the genetic potential that the best animals offer. Today, it’s crucial that your management programs are evolving along with your herd’s genetics.


The Modern Sow Challenge

Today’s performance potential of superior dam lines and elite sires is not being fully captured, says George Foxcroft, professor of swine reproductive physiology, University of Alberta. As a result, some  production systems are leaving money on the table.

Low-average-birthweight litters are a consequence of high ovulation rates and present unique management challenges. Many operations may benefit by reevaluating management techniques in order to tap  the full potential from today’s high-production sows.

Foxcroft suggests the following strategies to wean more pigs.

Production strategies at the sow/litter level:

  • Segregate sows into farrowing rooms based on anticipated birthweight phenotype.
  • Segregate different birthweight litters into different nursery/grow/finish flows.
  • Adjust nutrient requirements to reflect expected lean-growth potential.
  • Market progeny of different birthweight litters at different market weights or different ages.

Production strategies at the sow level:

  • Target nutritional interventions at sows that have a predicted low litter-birthweight phenotype.
  • Use artificial insemination strategies, including semen from boars with lower litter size, to limit intra-uterine crowding in early gestation. Focus on litter quality, not just quantity.
  • Use A.I. strategies, such as boars with high litter survivability, to mitigate the “sow” effects on the low-birthweight-litter phenotype.


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