SA flocks put melatonin to test for lifting twin lamb survival

SA based researchers have found supplementing ewes carrying twins with a melatonin implant could help lift lamb survival to weaning by more than 10 per cent. Trials are occurring on 12 SA and Vic properties this season.

TALKING LAMBS: University of Adelaide's Forbes Brien, Mackillop Farm Management Group executive officer Meg Bell, scanner Josh Cousins and SARDI senior research officer Alice Weaver at last week's MFMG workshop on Scanning and Survival in Sheep.

SA based researchers have found supplementing ewes carrying twins with a melatonin implant could help lift lamb survival to weaning by more than 10 per cent.

And this lambing season they are hoping to see these exciting results replicated in the paddock with 11 flocks across SA as well as one Vic flock involved.

Nearly 5000 ewes, scanned in-lamb with twins, on these properties will be given a Regulin implant behind their ear at about 90 days into pregnancy, with many ewes already administered.

These ewes will be monitored at lambing and their lambs followed through to weaning, recording a number of traits.

Regulin (a melatonin implant) is presently only registered for use in ewes pre-joining to enhance conception rates.

Speaking at last week's Mackillop Farm Management Group workshop at Lucindale, SARDI senior research officer Alice Weaver said lamb deaths were estimated to cost the sheep industry at least $540 million a year.

Birthing difficulties, starvation and mismothering account for the majority of these losses in the critical first 72 hours of life.

Dr Weaver says all lambs experience some form of hypoxia (oxygen deprivation) during the birthing process but the risk increases significantly in the second-born lambs.

"The first one (lamb) is generally expelled quite quickly, it is the second one that is quite at risk and can spend much longer - up to two hours - in the birth canal," she said.

In the past 3.5 years, the University of Adelaide-run project has looked at novel strategies to lift the weaning rate of the national flock.

This includes supplementing ewes with caffeine, rumen protected amino acids, beteine and melatonin to increase the ability of the lambs to cope with hypoxia.

In intensively housed animals, the Meat & Livestock Australia-funded project has found no difference in the survival of lambs born as singles but a 13-14 per cent greater survival in twin born lambs whose mothers had been given the hormone.

"It (melatonin) freely crosses the placenta, allowing delivery to the fetus via maternal supplementation and is involved in many metabolic processes," Dr Weaver said.

Similar results were observed in the paddock at Minnipa Research Centre on the Eyre Peninsula.

In 2021, two White Suffolk studs - Ashmore at Wasleys and Illoura at Moorlands - along with a Merino flock at Black Springs were involved in a small commercial trial with their twin-bearing ewes.

"At Ashmore there was about a 5pc lift in lamb survival in the melatonin mob but at Iloura there was a 98pc survival in the control group, which is pretty phenomenal, so the melatonin treated lambs were just the same," Dr Weaver said.

"We did see a slight increase in weaning weight in the melatonin group."

Dr Weaver says this year should give a better understanding of the benefits of melatonin with a range of breeds and production systems involved in the trial.

If it stacks up Ceva, the manufacturer of Regulin, could apply for a label change of its product to include use in pregnant ewes.

"It won't be a silver bullet for all producers but it appears to be cost effective if we can get a 10pc or more lift in weaning rate," Dr Weaver said.

"The implants are not cheap at $7 a dose but if producers can get an extra 26 or 28 lambs weaned (per 100 twin bearing ewes) it will definitely be worth it."

Illoura stud principal Allan Piggott says he was keen to be part of the project last year as improving twin lamb survival is important from both an economic and animal welfare perspective.

"We just need to do some more research and see where we can get the most benefit and return on investment," he said.

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