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Milking it: Boosting Returns with a Replacement Gilt Diet

Maximizing milk yield can minimize costs for producers

Milking it: Boosting Returns with a Replacement Gilt Diet

In a sector where things aren’t always cut and dried, there is at least one certainty: Piglets need milk, and an adequate supply is crucial for their development.

Unfortunately, sows don’t produce sufficient milk to optimize piglet growth. As well, the introduction of hyperprolific sow lines (ones that often give birth to more piglets than their functional teats) has made the problem greater by increasing litter size. As a result, there is less milk available per piglet, leading to lower weaning weights.

With sufficient milk in their system, piglets will be heavier at weaning, have greater vigor and be more resistant to disease challenges. They will also require fewer days to reach market weight, something producers currently address with creep feeding (providing a solid diet to piglets while they are suckling the sow, preparing their digestive system for weaning). Though creep feeding can be effective, it is also expensive, so science went in search of a more viable option.

Got Milk?

Taking up the challenge was Dr. Chantal Farmer, research scientist with Agriculture and Agri-Food Canada in Sherbrooke, Quebec. To address the milk shortage, Dr. Farmer sought to increase milk yield through enhanced mammary development, taking a multi-pronged approach:

Feeding fiber

With gilts growing faster these days, they often encounter leg issues, prompting some producers to slow that growth by restricting feed intake. This can be problematic, as Dr. Farmer had previously shown that a feed reduction of 20% between day 90 and puberty inhibits mammary development. With that in mind, she teamed up with Dr. Lee-Anne Huber at the University of Guelph.

They found that either using that same 20% decrease in feed intake or feeding an ad libitum diet (as much as the pig wants) with 25% more fiber could have a similar effect. Both approaches will reduce the growth rate of current gilt lines (that consume more feed compared with older lines) without lowering milk yield.

Need lysine? Try soybean

In the last third of gestation, mammary development is very rapid; however, there seems to be an underestimate of the recommendation for the dietary amino acid lysine during that crucial time.

By putting more soybean meal in feed, researchers managed to boost lysine levels by 40%, which increased the amount of milk synthesizing tissue in the mammary gland by 40% as well. Like farmers, scientists can’t stand still, so they will look to further benefit producers down the road by testing the lysine effect on multi-parity sows as well.

Prolactin is pro-milk

Prolactin is a hormone that plays a critical role in enabling mammals to produce milk. In the past, the hormone has been injected to raise prolactin levels in sows and increase milk yield. Through this study, researchers examined the potential for a drug called domperidone. This drug helps the body increase its own production of prolactin, and is even used by women who can’t supply enough breast milk after giving birth. With a veterinary prescription for use with sows, domperidone can be added to feed to stimulate prolactin, replacing the need for hormone injections. Given the current scrutiny around added hormones for animals, this could mean a better image for the industry as a whole.

As well, when the project team tested the drug that aids pigs in synthesizing more prolactin, they saw an average increase of 5.6% in body weight for piglets at day 22.

As with much in life, timing is critical for increasing prolactin. Prior to puberty, the gilt’s physiology is not equipped to reap the benefits from the drug; for best results, it needs to be incorporated in the diet during lactation.

Though all aspects of the study hold promise, the raising of recommended lysine levels in the gestation diet may be most critical. At present, some in the industry still assume that replacement gilts can be fed like market pigs, and that is simply not the case.

Hungry for More

Ultimately, this study was the product of cooperation. While Dr. Farmer provided expertise in swine lactation biology, Dr. Huber brought her extensive knowledge of swine nutrition. Work was done at both the University of Guelph and Universite De Sherbrooke, providing opportunities for new graduate students at these institutions.

Building on this study, researchers want to answer a key question related to the beneficial effect of an increase in soybean meal on mammary development of gilts in late gestation: Is that benefit really due to the increase in lysine, or to other components of the soybean meal?

With the high cost of production these days, anything that stimulates the mammary system should be a stimulating topic for years to come.

Publication links

  • FARMER C, Palin M-F, Hovey RC, Falt TD, Huber LA. 2022. Dietary supplementation with lysine stimulates mammary development in late-pregnant gilts. J. Anim. Sci. 100: 1-11.

  • Gregory NL, FARMER C, Friendship RM, Huber LA. 2023. The effect of moderate energy and protein restriction during gilt development on changes in body weight and backfat depth and subsequent lactation performance. J. Anim. Sci. 101: 1-11.


Project Title: New feeding and management strategies for replacement gilts that will maximize future milk yield.

Lead(s)/Co-Lead(s): Dr. Chantal Farmer (AAFC- RDC Sherbrooke)

Budget: $475,920

Priority Area(s): Nutrition

Research Methods

Eighty-eight gilts were recruited to determine the effects of moderate energy and protein restriction during the development period.

Gilts were randomly assigned to one of four feeding programs: 1) standard commercial diet fed ad libitum; 2) standard commercial diet fed 10% or 3) 20% below ad libitum, or 4) a high–fiber diet fed ad libitum.

The gilts were housed individually and received the feeding programs between 90 and 190 days of age, and standard gestation and lactation diets thereafter.

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