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Appetite Hormone Puts Pigs on Faster Growth Track

By Ben Hardin
September 16, 1999

Of every 10 pigs born alive, at least one dies within days and others may grow more slowly than their littermates. Those that thrive, however, generally gain more weight per pound of feed after weaning and have less carcass fat when they go to market.

Mindful that getting more pigs off to a good start could improve production efficiency, ARS scientists are researching hormones to find ways to enhance pigs’ appetites, manage stress and reduce sickness and deaths. Just shortening by one day the average time from birth to market could lower housing and feeding costs enough to boost annual net income for the nation’s swine producers by tens of millions of dollars.

In one experiment, researchers at Columbia, Mo., found that a single injection of the hormone orexin-B into 3-week-old pigs increased feed intake 18 percent, though only for a short time. More research is underway to find whether two or more well-timed injections can improve growth rates enough to be worthwhile.

Someday farmers may inject pigs, not with orexin-B, but with less expensive synthetic versions of it. Or a gene therapy may be developed to make pigs produce more of their own orexin.

Besides affecting appetite, hormones--in complex ways--exert major impacts on swine during stress in production environments. During birth, for example, stress may help pigs prepare for life beyond the womb. Research showed blood and tissue samples of pigs that came into the world by caesarean section had strikingly different hormone levels than pigs born naturally. Two weeks later more similarities and differences appeared, giving insights on lasting effects of birth experiences.

ARS is USDA’s chief scientific research agency.

An article about the research appears in the September issue of Agricultural Research magazine and online at: