PMID- 33205209 OWN - NLM STAT- MEDLINE DCOM- 20210215 LR - 20211118 IS - 1525-3163 (Electronic) IS - 0021-8812 (Print) IS - 0021-8812 (Linking) VI - 98 IP - 12 DP - 2020 Dec 1 TI - Supplementing Merino ewes with melatonin during the last half of pregnancy improves tolerance of prolonged parturition and survival of second-born twin lambs. LID - 10.1093/jas/skaa372 [doi] LID - skaa372 AB - High preweaning mortality rates continue to limit sheep production globally, constituting a major economic and welfare concern. Greater losses in twin lambs (>/=30%) compared with singletons (>/=10%) are attributed primarily to lower birth weight and increased risk of intrapartum hypoxia, leading to impairment of thermoregulation, neuromotor activity, and maternal bonding behavior. Previous intensive studies demonstrated that supplementing pregnant ewes with melatonin reduced the adverse effects of fetal growth restriction and perinatal hypoxia on the neonatal brain via increased umbilical blood flow, placental efficiency, and antioxidant actions. The current study examined the effects of supplementing pregnant ewes with melatonin on lamb survival, birth weight, and behavior under intensive conditions. From gestational day (gD) 80 until parturition, pregnant singleton and twin-bearing ewes were supplemented with melatonin via a 2-mg capsule fed daily (Mel-FED, n = 61) or 18 mg subcutaneous implant (Regulin), with one implant administered at gD80 and another at gD125 (Mel-IMP, n = 60). Control ewes received no supplementation (CTL, n = 60). Ewes and lambs were monitored via video throughout parturition. Postpartum measures were taken from lambs at 4 and 24 h (live weight [LW], rectal temperature, serum immunoglobulin G, and latency to stand and suck after birth) and LW at 72 h, 7 d, marking (49.7 +/- 0.2 d), and weaning (124.2 +/- 0.8 d). Chi-square analysis was used to compare lamb survival between treatment groups. There were no treatment effects on singleton lamb survival. Melatonin supplementation tended to increase the proportion of twin lambs surviving from birth to weaning (Mel-FED = 85.5%; Mel-IMP = 85.9%; CTL = 72.9%; each P < 0.1). Survival of first-born twins did not differ between treatment (each ~90%, P = 0.745) but within second-born twins, survival of Mel-FED was greater than CTL (81.6 vs. 57.1%, P = 0.023), and Mel-IMP (78.1%) tended to be greater than CTL (P = 0.068). Similarly, in second-born twins exposed to prolonged parturition (>/= 90 min), survival of lambs from Mel-FED ewes was greater than CTL (86.7% vs. 42.9%, P = 0.032), while Mel-IMP was intermediate (66.7%). These data suggest that the neuroprotective actions of melatonin may improve twin lamb survival by increasing tolerance of prolonged parturition and provide a sound basis for continued testing in extensively managed sheep flocks. CI - (c) The Author(s) 2020. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. FAU - Flinn, Tom AU - Flinn T AD - Davies Livestock Research Centre, School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, SA, Australia. FAU - McCarthy, Niki L AU - McCarthy NL AD - Davies Livestock Research Centre, School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, SA, Australia. FAU - Swinbourne, Alyce M AU - Swinbourne AM AD - Davies Livestock Research Centre, School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, SA, Australia. FAU - Gatford, Kathryn L AU - Gatford KL AD - Robinson Research Institute, The University of Adelaide, Adelaide, SA, Australia. AD - Adelaide Medical School, The University of Adelaide, Adelaide, SA, Australia. FAU - Weaver, Alice C AU - Weaver AC AD - Turretfield Research Centre, South Australian Research and Development Institute, Rosedale, SA, Australia. FAU - McGrice, Hayley A AU - McGrice HA AD - Davies Livestock Research Centre, School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, SA, Australia. FAU - Kelly, Jennifer M AU - Kelly JM AD - Turretfield Research Centre, South Australian Research and Development Institute, Rosedale, SA, Australia. FAU - Walker, Simon K AU - Walker SK AD - Turretfield Research Centre, South Australian Research and Development Institute, Rosedale, SA, Australia. FAU - Kind, Karen L AU - Kind KL AD - Davies Livestock Research Centre, School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, SA, Australia. AD - Robinson Research Institute, The University of Adelaide, Adelaide, SA, Australia. FAU - Kleemann, David O AU - Kleemann DO AD - Turretfield Research Centre, South Australian Research and Development Institute, Rosedale, SA, Australia. FAU - van Wettere, William H E J AU - van Wettere WHEJ AD - Davies Livestock Research Centre, School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, SA, Australia. LA - eng PT - Journal Article PL - United States TA - J Anim Sci JT - Journal of animal science JID - 8003002 RN - JL5DK93RCL (Melatonin) SB - IM MH - Animals MH - Birth Weight MH - Dietary Supplements MH - Female MH - *Melatonin/pharmacology MH - Parturition MH - Pregnancy MH - Sheep MH - Sheep, Domestic PMC - PMC7769222 OTO - NOTNLM OT - hypoxia OT - lamb survival OT - melatonin OT - reproduction OT - sheep EDAT- 2020/11/19 06:00 MHDA- 2021/02/16 06:00 PMCR- 2021/11/17 CRDT- 2020/11/18 06:02 PHST- 2020/09/17 00:00 [received] PHST- 2020/11/10 00:00 [accepted] PHST- 2020/11/19 06:00 [pubmed] PHST- 2021/02/16 06:00 [medline] PHST- 2020/11/18 06:02 [entrez] PHST- 2021/11/17 00:00 [pmc-release] AID - 5986736 [pii] AID - skaa372 [pii] AID - 10.1093/jas/skaa372 [doi] PST - ppublish SO - J Anim Sci. 2020 Dec 1;98(12):skaa372. doi: 10.1093/jas/skaa372.