Dr. Chantal Farmer’s work investigates interventions to enhance sow mammary development
By Jackie Clark
A researcher with Agriculture and Agri-Food Canada (AAFC) is working to better understand how to promote mammary development in sows.
Through genetic selection, scientists have achieved increased litter size “and now we really need to work on the sow to make sure she has enough teats, she has enough milk, enough colostrum to sustain growth of all these piglets,” Dr. Chantal Farmer, research scientist at AAFC’s Sherbrooke Research and Development Centre, told Farms.com.
Pigs go through “three phases of rapid mammary development,” she explained. The first is from 90 days of age to puberty, the second is from the 90th day of gestation to farrowing, and the third is during lactation.
Farmer’s research focuses on the first two stages because “I want the gilt or the sow to have as many mammary cells that can produce milk as possible when lactation starts,” she said.
Hormonal or nutritional interventions can help stimulate and enhance mammary development, but only during those specific life stages. Hormonal changes increase mammary development and milk production by enhancing prolactin, a hormone associated with lactation, she explained.
Previous research has investigated plant sources of estrogens, called phytoestrogens. When phytoestrogens were added to diet of growing gilt at 90 days of age “it increased the number of mammary cells at puberty,” Farmer said.
However, because scientists have to slaughter the animals to assess mammary cells, they cannot assess whether enhanced mammary development at puberty carries over to benefits after breeding to lactation and milk yield, she explained. “I presume so, but I didn’t prove it.”
Similar changes can be observed at the end of gestation.
“At the end of gestation if you inhibit the hormone prolactin, you inhibit mammary development. If you increase the amount of prolactin that the animal synthesizes herself (with a pharmacological agent) she will produce more milk in the following lactation,” Farmer said.
Previous research had determined that body condition is related to milk production of sows. Sows that were obese, with more than 35 mm of backfat saw a negative impact on mammary development. However, sows that were too lean also had less mammary tissue, she explained.
“You often have gilts that are quite thin, so it’s very important to make sure that during gestation you feed them enough to achieve a backfat thickness that’s above 16 mm,” Farmer said.
Her most recent research is aiming to determine the relationship between lysine in the diet during late gestation and mammary development.
“We know lysine is very important for the gilt,” Farmer said. Specific amino acid requirements increase at the end of gestation, and previous research had indicated a relationship may exist between lysine and milk production.
In a recent experiment “I was feeding 20.6 grams per day of lysine compared to (a control) of 14.7 grams per day,” Farmer said. The control is similar to what would be typical on a commercial pig farm.
“I’ve slaughtered the animals at the end of gestation, took the mammary tissue, and right now we’re doing the dissection of the mammary tissue,” she explained.
Researchers will remove outer fat layer and separate the tissue that contains the cells that will synthesize milk. They will collect data on the weight and composition of that tissue. The amount of DNA will reveal how many cells are present and RNA will indicate metabolic activity.
Farmer hopes to have those results by the fall.
“I’ll be able to say if increasing lysine to those levels effects mammary development or not,” she said.
Future research may investigate combining hormonal and nutritional interventions or “trying to find nutritional ways to increase IGF1 (insulin-like growth factor 1) levels,” which can also have an impact on mammary development, she added.
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