2 April 1999

Too much fat to lactating sows trims litter size

By Sue Rider

TOO much fat fed to lactating sows can reduce litter size by one piglet, according to researchers at SAC Aberdeen who compared starch and fat as energy sources in lactating sow diets.

At farrowing 24 sows were fed diets containing similar energy levels, but with either soyabean oil or maize starch as the main energy source.

Litter size was standardised to 10 piglets, which were not offered creep. Sows and piglets were weighed individually every week from farrowing to weaning at 28 days. Sows were also ultrasonically measured for backfat thickness.

SACs Gwendolyn Jones said that over the 28 days of lactation, the energy source in the diet had no effect on sow weight and backfat losses.

But average litter growth rates tended to be higher in the starch than fat-fed sows. Starch-fed sows had greater litter weights at weaning. Litter size was smaller for fat-fed sows due to increased piglet losses during lactation.

"Sows had the same litter sizes, but fat-fed sows had fewer piglets from week three onwards, and about one piglet less at the end of lactation," said Miss Jones.

"In this study sows were fed diets containing the same levels of energy, but towards the end of lactation the piglets were not doing so well on sows fed the high fat diet because these sows could not produce enough milk," she said.

Fat is more energy dense than starch and could be used to maximise energy intakes, especially in sows with low appetite, she said.

But while fat is thought to improve piglet survivability when fed in late pregnancy/early lactation because it increases milk fat content and so energy intake of the piglets, it cant be used as a main dietary energy source. Starch is needed to produce sufficient glucose, the main factor driving milk production.

"In later lactation, when milk yield is limiting to piglets, fat-fed sows are not providing enough milk because they are deficient in dietary glucose," said Miss Jones. "You can increase milk fat but unless milk yield is increasing the nutrient output is not there."

SOW LACTATION

&#8226 Restrict fat fed.

&#8226 Sows need starch.