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Pigs that better digest their nutrients could reduce 
pork industry’s carbon footprint

Pigs will eat what’s put in front of them — but digesting it is another question.

In particular, according to one research scientist from the South China Agricultural University, nitrogen and phosphorus can pass through the pig undigested, causing downstream environmental challenges.

Lead author of the study Xianwei Zhang, published recently in the online journal eLife, says it comes down to a lack of a way for the pig to process those products.

“They lack the microbial enzymes that break down phytate — the main source of nitrogen and phosphorus — and types of fibre called non-starch polysaccharides,” Zhang said.

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“We suggest that making up for the pigs’ deficiency in these enzymes will benefit the pork industry by increasing the animals’ feed use and reducing their nutrient emissions.”

To test this idea, Zhang and his team delivered the three enzymes into the genome of pigs. These enzymes, which are secreted by microbial communities, were optimized to adapt to the pigs’ digestive tract environment.

They were expressed specifically in the pigs’ salivary gland, allowing the digestion of phytate and non-starch polysaccharides to begin in the mouth.

Co-author Zhenfang Wu said the work builds on past research.

“Previous studies have shown that genetically modified pigs that release the microbial enzyme phytase from their salivary glands have significantly reduced levels of phosphorus in their manure,” Wu said.

The results of the feeding trials confirmed the pigs were able to digest these and other key nutrients, lowering their emissions and growing faster.

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