Speed of a lamb’s bleat linked to survival

By Emma Young 26 October 2010
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Lambs who bleat soon after birth are more likely to lead a long and healthy life, say scientists.

NEWBORN LAMBS WITH THE best genetic chance of survival have some pretty peculiar-sounding characteristics, according to Australian scientists – not least the ability for quickfire bleating.

Anecdotally, breeders had already observed a link between bleating and
survival, says Lynton Arney, who runs the Inverbrackie Border Leicester
Sheep Stud near Strathalbyn in South Australia. “The noise made by a
lamb helps remind the mother ewe that she has just given birth to a lamb
and improves the mothering instinct,” he says.

To test the idea Dr Forbes Brien of the South Australian Research and Development Institute (SARDI) and colleagues at the Sheep Cooperative Research Centre (CRC) collected records from 15,000 lambs, more than 6000 adult females and 284 sires from eight sites across Australia.

They asked the site managers to perform a number of measures within 18 hours of the lambs’ birth. And they found that certain genetically controlled characteristics meant a lamb was more likely to survive to weaning.  A hairier coat, a shorter distance between the head and the rump, and a warmer rectal temperature were all linked to better odds – as was a readiness to bleat. This was measured by putting the lamb on the ground and using a stopwatch to time how long it took for them to bleat. Anything under five seconds was good news.

“I think a quickness to bleat indicates that a lamb is more active at establishing a bond with its mother – it contributes to strengthening the bond, which isn’t solely due to the mother’s activities,” says Forbes.

Bleating obvious

A hairy coat could come in handy in cold, wet, windy conditions, he adds. “We speculate that the effect may not be so much because the coat insulates the lamb, but that it’s an indicator of its underlying vigour.”  A warmer rectal temperature might help the lamb withstand colder temperatures, and a shorter head-to-bottom length might make for a less difficult birth.

But the team found no evidence for suspected links between some other factors and survival. For example, some breeders like to monitor how closely a ewe remains to the shepherd while her lambs are being tagged, but the team found that this wasn’t reliable in revealing anything about the lambs’ genetic chances of survival.

Checking all newborn lambs for measures like bleat time would be very time-consuming and expensive commercially, though, comments Lynton. But the research shows that if a farmer targetted lambs with these characteristics for breeding, they could increase lamb survival by 5 per cent over 10 years, Forbes says. 

He presented the work at the National Sheep CRC Conference in Adelaide last week.