February 5, 2014

No 9. Sheep Performance Recording in New Zealand. History - Lambing behaviour

By Dr Clive Dalton

Importance of the birth site

Dr Ron Kilgour at Ruakura did some extremely useful research to help Sheeplan breeders improve the accuracy of lambing information.

Along with Dr Bob Welch and an Australian colleague, he was the first to publish work on the importance of the birth site in lambing behaviour and lamb survival, which he did at Waihora near Taupo. I had close contact with the work when working on the cattle-breeding project there at the same time. 

Ron and his mates all stayed in the shearers’ quarters at Waihora where I took a Northumbrian farmer’s son on his OE to help with recording – and his mother had never let the poor lad make his bed before, wash his undies or fry an egg.  He became of age as the wind whistled off Ruapehu on his lambing beat.

Everybody knew that ewes selected their spot in the paddock to lamb, but we didn’t fully realise that it was the smell of their burst waters that tied them to it. Then it’s here in a normal birth that her lambs are dropped.  To mark this spot, Ron used to knock in a peg into the ground where her waters burst, and mark her tag number on the peg so it could be read from a distance. 

What was fascinating was when the lambs from these twinning ewes were born, and started to get on their feet to seek a teat, if they wandered away from the birth site and started bleating, the stressed ewe always preferred to going back to her water’s burst to check it out – because of the smell.

So if any lambs wandered some distance from the birth site, by following another ewe or even the moving shepherd or the dog, or in particular if the ewe was moved by the shepherd, she’d give go back to find the smell of her waters in preference to rounding up a stray lamb.  She would so often just stand on the birth site and bleat to call the lamb back to her, or only go a little distance to attract them back.

On our Whatawhata hills, if a newborn lamb slipped down the slope off the sheep track where its dam had lambed, the chances increased tenfold of the lamb being ignored by the ewe in her preference to stay on her birth site, which was well reinforced if she’d produced a second lamb.

So from all this we learned to leave ewes where they had lambed for as long as possible, as some Kilgour observed at Waihora didn’t lead their lambs from the birth site for up to 3 days. 

Kilgour’s work also showed the need to fence off really popular birth sites in lambing paddocks, because of all the mixed smells which must have accumulated over time, and the build up of mud in wet weather which risked lambs’ navel infections.

Catching multiple lambs

It was always a bit of fun for shepherds having to record a ewe with twins (or triplets which were not common in the early days) and having to sit or kneel on the ground to get all the recording gear organised, while hanging on the other wet slippery lambs while each was tagged.

The shepherd has raddled the tails of these quads  to avoid any mismothering. Two had to be removed from the ewe.

A Coopworth farmer near Cambridge, Edward Dinger, whose flock had many twins and triplets to catch and record, came up with the brilliant idea of using a fish landing net to catch the lambs, and hold them together till they were tagged. The lambs were not stressed, and the ewe could see and smell them through the net. All was at peace till the job was done.  It maybe looked a bit daft going around a lambing paddock with a fish landing net –but it certainly was a brilliant idea.

Identifying multiple lambs
A study done at Ruakura by Welch and Kilgour scared us about the accuracy of lambing data.  They and their technicians sat up all night to watch ewes lambing and then record what actually happened.   Then they compared that with what the shepherd saw and recorded when he did his normal lambing beat at 7am. 
It was a shock to find that the very honest and experienced shepherd made at least 40% errors in pairing lambs with ewes, as all sorts of mix-ups had happened with twins wandering away from the birth site, lambs being pinched by other ewes - and much more.  Even one lamb couldn’t be accounted for by the shepherd.

In the study, ewe 611 was the best behaved producing her own two lambs which were recorded correctly.  Ewe 169 was the demon - producing two lambs, then licking four others with five lambs recorded to her by the shepherd - if he'd believed her!

So as a result of this work, we encouraged Sheeplan breeders, especially if they had a lot of twins in their flocks, and especially if there were popular birthing spots in lambing paddocks, to go around at daylight and code mark multiples with a raddle, and keep away till mid morning before tagging them.  This gave the ewes and lambs a bit more undisturbed bonding time, so any mothering mixups that happened after daylight could be sorted out to reduce the error rate in pedigreeing. 

Code marks we worked out for multiple lambs to reduce the risks of errors
We encouraged breeders to be brutally honest and have a code that noted certainty about the parentage, and a code for when there was doubt. This was:

1 = birth observed, parentage correct.
2 = birth not observed, parentage assumed correct.
3 = birth not observed, doubtful parentage.

Thieving ewes
We all knew that the error rate could never be zero, as some old ewe would always fool us. The biggest culprit was a ewe near lambing that went around stealing lambs from newly-lambed ewes, and we didn’t know that she hadn’t lambed herself until after hours of frustration, she was given an internal inspection and often assisted to lamb if she was close to stop her criminal disruptions.

It was scary to think of the long term effects of getting a pedigree wrong at birth, especially in a male lamb that could go on to be a stud sire, and all his BVs and Index would be wrong.  He could be sold for big money on the basis of his pedigree – which could be lies from a mismothering error way back in the lambing paddock on a wet morning!

Umbilical cords
Bram Uljee came up with a smart idea of checking how many lambs a ewe had actually given birth to, by using the afterbirth on the birth site. There should always be one umbilical cord for each lamb born, so if this didn’t tally, you knew that a lamb was missing.

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