US research looks at adjusting poultry sex ratios

Researchers from the University of Georgia are working on ways to distort the chicken's gender ratio in favour of males for broiler production and of females for the egg and breeding sectors.

 

Chickens, like most animals, typically produce equal numbers of males and females. However, this natural sex ratio does not always work in the poultry industry's economic favour. A University of Georgia (UGA) researcher is working on ways to skew the chicken's sex ratio to help the industry streamline production and make more money.

 

Chickens are big business in Georgia, worth US$4.9 billion in 2008, or 41 percent of the state's total agricultural value. The industry is split into two areas: meat production and egg production.

 

Chickens grown for meat are called broilers. For this part of the industry, the females of this breed are less profitable. On average, male broilers weigh half a pound more than females at market age, and they eat five per cent less feed.

 

For the egg-laying breed, females are prized over males, obviously, because males cannot grow up to produce eggs.

 

Dr Kristen Navara, a poultry scientist with the UGA College of Agricultural and Environmental Sciences, is trying to determine how to control avian sex ratios.

 

Navara said that in nature, it is a necessary strategy to adjust offspring sex in relation to the environment. Humans, rodents, birds all skew sex ratios and it is clear females need the ability to adjust offspring for the environment where they will be born or hatched into, she added. 

 

Navara has recently studied skewed sex ratios in hamsters and humans in relation to day length. She is now looking for the mechanism that can control the ratios in poultry and finches and is using the hormone corticosterone to find that mechanism.

 

Injecting female birds with a burst of corticosterone just before ovulation produced a sex ratio skewed toward males, or 81 per cent.

 

She believes she can flip the ratio to favour males or females using hormones or aggravates, which stop the secretion of corticosterone.

 

Sara Beth Pinson, a graduate student in the same lab, is coordinating studies to determine the optimal dose of corticosterone to produce the desired result. Together with Navara, they are also testing different durations of the hormone treatment to determine how long-term treatments affect offspring sex. Research results could be available in six months.

 

Focused on species survival, Navara is also looking at sex ratios in zebra finches wherein she said "where it started, in an ecological context." The head researcher said she is interested in how a species survives and to figure out how to adjust the sex ratio of avian offspring which can help in conservation efforts.

 

This research "is something the industry has been looking for for years", said Mike Lacy, head of the CAES poultry science department. The US poultry and egg industry for this Navara's research is something the industry is very interested in, he said. 

 

It is important to note that no chickens used for food are given hormones. Navara's research is only using hormones to discover the mechanism. Broilers are not treated with hormones and the industry will never use hormones for treatment, said Lacy.

 

So far, the hormone injections seem to work, but Navara said they want to find the mechanism the hormone is working through and then produce a non-hormonal treatment for the birds.