The costs of achieving 30 pigs/sow/year (p/s/y) may be too high to justify, agree North American reproductive physiologists.

To accomplish the 30 p/s/y goal, we must gain a better understanding of reproductive biology and the “largely untapped reproductive capacity of contemporary dam-line sows,” said George Foxcroft, leader of the swine research and technology center at the University of Alberta, in his opening comments at a day-long reproduction workshop held at the Leman Swine Conference in St. Paul last fall.

Joined by other reproductive specialists, the day was spent challenging what Foxcroft describes as “the comfortable assumption that a lack of reproductive performance in today's industry is due to inherent fertility problems within existing dam-line populations.”

Parity 1 Sow Condition

At the outset, Foxcroft doesn't buy the argument that super-thin sows cannot maintain their condition and perform well. This is a complex issue, reflected in changing wean-to-estrus intervals (WEI), ovulation rates and embryonic survival.

He turned to an ongoing study, in which groups of Parity 1 sows were either fed to appetite (controls) or severely restricted (fed 50% less) during the last week of their 21-day lactation periods. The restricted feeding represented typical sows with low appetite and/or subjected to poor management, he explained.

The control sows generally lost about 22 lb. during lactation, while restricted sows lost nearly twice as much weight.

After weaning, nearly 200 control sows and restricted sows were fed the same diet from weaning to 30 days into gestation during a 2-½-year stretch. Results showed all sows cycled and 92-100% became pregnant, but restricted sows were actually heavier at the 30-day gestation mark. “This represents classic compensatory growth of weaned sows,” he pointed out. Embryo survival was essentially the same in both groups.

Foxcroft's take-home message from the study was twofold:

• At weaning, Parity 1 sows still have massive requirements for lean growth potential. “If you get them the ingredients to recapture that lean growth potential, they will respond. These are amazing animals in terms of the ability to grow,” he said.

• From the experimental model, examining the negative effects of catabolism (metabolic breakdown of tissues and excessive weight loss) and the Parity 1 sows' breeding performance (measured by embryo survival), Foxcroft said the experiments reinforced his belief: “This totally removes any excuse at all that there's something wrong with these sows.

“One of the great failures of the pork production industry has been the inability to capture the true production potential of the excellent dam lines already available,” he continued. “To correct these deficiencies, appropriate and achievable key performance indicators (KPIs) should relate closely to known characteristics of commercial dam-line sows and be both measurable and economically meaningful.”

Thus, the stage was set to identify these key drivers, including the physiological challenges and limitations that may prevent producers from achieving the 30 weaned pigs/sow/year benchmark.

“Our producers are trying to make money, and should not be encouraged to see a simplistic measure of productivity, like maximal numbers of pigs produced, at any cost, as a worthwhile goal,” Foxcroft stated.

“A consistent flow of good quality weaned pigs should be the principal goal, and is not necessarily best served by developing breeding herd strategies that assume the hyper-prolific sow will necessarily meet this need,” he continued. “Indeed, increased prolificacy may well be associated with increased variability in weaned and finished pig quality.”

Biological Changes

“The need to develop management techniques that reflect the changing biology of contemporary dam-line females seems to be an urgent issue,” Foxcroft continued. Much of this effort should be aimed at improving the performance of second-parity sows.

“But, producers must also study the growing evidence that prenatal programming affects post-natal performance. In the end, the most profitable production systems may need to consider segregated parity and litter management as a more profitable strategy.

“Once you get to an acceptable gilt litter size — from 10 up to 15 pigs — we are definitely having an impact on the birth weight of the pigs. This leads to a whole list of questions about whether offspring (of gilts) are appropriate to place alongside the offspring of mature sows.

“I think there is more and more acceptance that the growth potential of these pigs (from P1 sows) is limited. Also, it is likely that their survivability and health status are also compromised, because we are pushing these gilts very hard, and there is some sort of a programming effect that we need to consider,” Foxcroft said.

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