Increasing Dietary Lysine (Protein) Intake in Late Gestation Improves Milk Production by Gilts

Significant mammary development occurs during late gestation in sows, which is necessary to support milk production in the ensuing lactation period. Gilts (first-parity sows) have not achieved mature body weight and are developing mammary tissue for the first time. Thus, gilts may benefit from additional amino acid supply during late gestation to support both fetal growth and mammary development, as well as their own growth.

Earlier work found that feeding gilts 40% more standardized ileal digestible lysine (SID Lys), via soybean meal, beyond the recommended 18.6 g/day, improved mammary development by 44%, though subsequent milk production was not assessed.

Vanessa Kloostra and Dr. Lee-Anne Huber from the University of Guelph and Dr. Chantal Farmer from Agriculture and Agri-Food Canada aimed to determine the level of additional standardized ileal digestible lysine (SID Lys), provided through soybean meal in late gestation, to maximize piglet birth weight and subsequent milk production by first-parity sows.  

In the current study, 152 first-parity sows were enrolled beginning on day 90 of gestation and followed through weaning. Seven treatment diets were formulated to provide: 70%, 85%, 100%, 115%, 130%, 145% and 160% of the NRC- (2012) estimated SID Lys requirements via the addition of soybean meal. Sows were fed 2.65 kg/day of their assigned gestation diet from day 90 of gestations until farrowing. After farrowing, all sows received a standard lactation diet.  

Body weight was recorded on days 90 and 110 of gestation, within 24 hours of farrowing, and at weaning (day 20 of lactation). Sow receiving higher levels of SID Lys (protein) gained more weight during gestation. However, these same sows also tended to lose more weight during the ensuing lactation period.

In late gestation, as expected, nitrogen absorption, retention and excretion increased with greater dietary SID Lys (protein) intake. However, nitrogen (protein) retention was maximized at approximately 22 g SID Lys/day, which corresponded with the 115% diet.

Piglet weights were recorded within 24 hours of birth, at days 7 and 14, and at weaning to assess growth performance. There was no difference in litter size at birth (average 14.8), but piglet birthweight increased as dietary SID Lys increased up to 22.0 g/day, corresponding with the 115% diet. Average piglet birthweight reached 1.45 kg at this level.

Piglets were not offered creep feed, meaning their weight gain reflected sow milk production alone. Average estimated milk yield increased to 11.27 kg/day in sows that received 22.7 g SID Lys/day during late gestation (approximately 119% of NRC recommendations). Higher SID Lys (protein) levels in late gestation were also associated with increased litter average daily gain during weeks 2 and 3 and improved overall growth throughout the lactation period.

Providing additional dietary lysine (protein) during late gestation is essential for first-parity sows, as they must support their own continued growth while also meeting the demands of fetal development and mammary tissue expansion.   

This study demonstrated that supplementing SID lysine via soybean meal can improve milk production and enhance piglet growth outcomes in the subsequent lactation period. Based on these findings, the researchers recommend increasing dietary lysine intake to approximately 15% above NRC recommendations, or around 22 g SID Lys / day, to maximize piglet birth weight and subsequent milk production.

 

Acknowledgment: Special thanks to Vanessa Kloostra, Dr. Chantal Farmer and Dr. Lee-Anne Huber for providing updates to their research and Dr. Lee-Anne Huber for supplying the photo.