Modern pork genetics has delivered remarkable gains in productivity, with larger litters now common across many farms. But that success has also created a challenge producers are increasingly aware of: ensuring the sow produces enough milk to support all her piglets.
Research by Dr. Chantel Farmer, a scientist at the Sherbrooke Research and Development Centre with Agriculture and Agri-Food Canada, suggests the solution may begin earlier than many producers think – well before lactation even starts.
Speaking at the Manitoba Swine Seminar in Winnipeg in February, Farmer, who has studied sow lactation since the mid-1980s, says the modern sow is already an extraordinary milk producer.
“I think everybody who works with pigs will agree with me,” she said. “The lactating sow is amazing. If you look at the amount of milk she produces on a per-kilogram basis during lactation, she produces more than a dairy cow.”
Even so, the sow’s remarkable output is often not enough to keep up with the demands of today’s large litters.
Genetic improvements have steadily increased litter size over the years, meaning more piglets are competing for the same milk supply. The result is that piglets often have the capacity to grow faster than the milk they receive from the sow.
“If you give piglets extra milk in a bottle on top of what they receive from the sow, they grow more,” Farmer explained. “That tells us their growth potential is greater than the milk they’re receiving.”
The challenge for researchers has been finding ways to increase the sow’s milk production capacity.
A key factor lies in the development of the mammary gland. Milk production depends largely on the number of secretory cells in the mammary tissue when lactation begins. The more milk-producing cells present, the greater the sow’s potential to produce milk.
Mammary development occurs during three main periods of a pig’s life: before puberty, during the last third of gestation, and during lactation itself. Farmer’s research focuses on the late-gestation stage because it offers an opportunity to influence mammary development before piglets are born.
Inside the mammary gland are two major types of tissue. Parenchymal tissue contains the cells responsible for synthesizing milk, while extra-parenchymal tissue consists mostly of fat and does not contribute to milk production. The goal, Farmer says, is to increase the amount of the productive parenchymal tissue.
Researchers have examined a number of feeding strategies to stimulate that development. Increasing energy intake during late gestation was one possibility, but studies found that feeding excess energy did not improve mammary development and could even increase fat deposition rather than milk-producing tissue.
Protein nutrition, however, showed more promise, particularly the amino acid lysine.
In research trials, increasing lysine intake in pregnant gilts by about 40 percent during late gestation produced a dramatic effect. Gilts receiving the higher lysine levels developed roughly 44 percent more parenchymal tissue in the mammary gland.
“That increase means more milk-synthesizing cells,” Farmer said. “And the more cells you have, the greater the milk production potential.”
Interestingly, the same response was not observed in multiparous sows. Mature animals already had higher levels of mammary tissue and did not respond significantly to increased lysine levels. The results suggest that gilts, which are still growing and developing, may benefit the most from targeted nutrition during late gestation.
Further studies examining actual milk production found that feeding about 22 grams of lysine per day during late gestation maximized piglet birth weight and milk yield during the following lactation. That level is roughly 15 to 20 percent higher than the current recommended requirements.
Another important period is the transition stage, which spans the final week before farrowing and the first few days afterwards. During this time, the sow begins producing colostrum and milk while still supporting fetal growth, increasing her nutritional demands.
Body condition also plays a role in mammary development. Research suggests that sows that are too lean at the end of gestation tend to have reduced mammary tissue development. Animals with less than about 16 millimetres of backfat showed lower levels of the productive parenchymal tissue.
Maintaining proper body condition throughout pregnancy, therefore, remains an important management factor.
For producers, the research highlights the growing importance of gestation nutrition as litter sizes continue to increase. Feeding strategies that support mammary development, particularly in gilts, may help ensure sows have the capacity to produce enough milk for modern litters.
As Farmer notes, preparing the sow for lactation begins long before the first piglet is born.
“With today’s genetics, we have piglets capable of tremendous growth,” she said. “The challenge now is making sure the sow can keep up.” •
— By Harry Siemens