Research into the benefits of melatonin

Regulin (which contains melatonin) is presently registered for use in ewes 30 days pre-joining to help with conception rates.

But more recent studies have been looking into whether the hormone, which has strong antioxidant potential, helps to increase blood flow and acts as a neuroprotectant, has multiple benefits in ewe pregnancy management.

University of Adelaide grant-funded researcher Jamee Daly is a member of Will van Wettere's reproduction research team out of the Davies Livestock Research Centre at Roseworthy Campus.

She spoke about some of the studies under way during a recent SA Drought Hub forum tour to the Turretfield Research Centre - a SARDI research farm in SA's Barossa Valley that collaborates alongside the University of Adelaide to facilitate on-farm research.

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She said recent research previously looked into supplementing melatonin in ewes at day 90 to 100 of gestation and whether it could improve twin lamb survival.

"Survival is not normally a concern in first-born lambs, as they don't tend to have an issue with oxygen deprivation during birth. However, it is a huge problem for that second-born lamb," she said.

"So we wanted to see if a boost of melatonin in ewes late in gestation would help increase the number of twin lambs surviving to weaning."

In the intensive 'Animal House' at Turretfield, Ms Daly said they found an 11 per cent to 14pc increase in twin lamb survival after the supplement at day 90 of gestation.

Now through the Sheep Industry Fund, Producers and MDC funding, Ms Daly says she is involved in a commercial validation trial being conducted across 15 SA and Vic farms this year.

Nearly 5000 ewes, scanned in-lamb with twins, on these properties will be given a Regulin implant at about 90 days into pregnancy, monitored at lambing and their lambs followed through to weaning.

In addition, the SIF has supported further work on melatonin, and its potential to mitigate the effects of heat stress in both ewes (through joining and in gestation) and rams (prior to and during joining).

"In rams, we are looking to see if melatonin, potentially at joining or 30 days prior, improves their semen quality and libido during summer," Ms Daly said.

"Specifically whether it helps their ability to thermoregulate and better manage heat stress, therefore increasing fertility.

"In ewes, we are timing the implant or dose rate to peak at when it's going to be hot to help facilitate conception, through improving fertilisation and embryo implantation, which is hugely important.

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"Again, it is the antioxidant potential of melatonin we believe helps them cope in the heat as it should aid thermoregulation, and improve fertility outcomes."

Ms Daly said as the application of melatonin was so easy, "the potential for farmers to just implant all the sheep around joining, during periods of heat, at a set dose rate would be immensely valuable".

"It costs about $7 per implant, but if you get an 11 to 14pc increase in your twin lamb survival, then it's worthwhile," she said.

"Additionally, if shown be beneficial, its application to improve conception rates during periods of heat adds more value to this supplement."

Ms Daly said they had already seen an increase in conception rates in maidens, particularly when administered at joining.