The Joint Annual Scientific Meetings of the Endocrine Society of Australia and the Society for Reproductive Biology 2018

The Effects of Maternal Melatonin Supplementation in Mid to Late Gestating Singleton and Twin-bearing Merino Ewes on Growth Parameters at Birth (#346)

Tom Flinn 1 , Alyce M Swinbourne 1 2 , Niki McCarthy 1 , Jennifer Kelly 2 , Kathryn Gatford 3 , Karen Kind 1 , Hayley McGrice 1 , Simon Walker 2 , Dave O Kleemann 2 , William Van Wettere 1
  1. The University of Adelaide, Adelaide , SOUTH AUSTRALIA, Australia
  2. Livestock & Farming Systems, South Australian Research and Development Instiute , Rosedale, South Australia, Australia
  3. Adelaide Medical School, The University of Adelaide, Adelaide, South Australia, Australia

Supplementing the maternal environment with a neuroprotectant, melatonin, may improve neonatal survival through increased placenta efficiency, umbilical cord blood flow, and higher birth weight. While melatonin has mainly been investigated as a means of improving the development and survival in human babies, there is also potential that this neuroprotectant may help to reduce the high levels of neonatal mortality in Merino sheep, which can be as high as 40% for twins. From day 80 of gestation, ewes were supplemented with melatonin via a subcutaneous 18 mg Regulin® implant (MEL-IMP n = 13) or 2 mg gel capsule fed orally daily (MEL-FED n = 14). Thirteen ewes received no supplementation (CTL). Ewes were intensively monitored during parturition and weight of lambs was measured at 4, 24, 72 hours and 7 days following birth. Morphology was measured at 4 hours then again at 7 days following birth. Preliminary analysis showed twin lambs (n = 45) were consistently lighter compared to singleton lambs (n = 15) at all time points (4h P=0.001; 24h: P=0.001; 72h: P=0.001, 7 days: P=0.001), irrespective of melatonin treatment. Similarly, morphological measures; crown-rump length (P=0.013), crown width (P=0.001), forelimb length (P=0.003), thoracic (P=0.076) and abdominal circumference (P=0.019), tended to be greater in singleton lambs compared to twin lambs. When analysing the morphology of just twins lambs and lamb weight was accounted for within treatment, both MEL-IMP and MEL-FED lambs were larger, with longer crown-rump (P=0.001) and forelimb length (P=0.006) as well as larger crown width (P=0.001) compared to CTL twin lambs. While these early results are promising, further research is being conducted which will include analysing the effects of pre-natal melatonin on lamb behaviour, such as time to stand and suckle, as indicators of lamb survival during the first few days of life.