Maternal melatonin implants improve twin Merino lamb survival

Area of Science:

• Animal Science
• Reproductive Biology
• Veterinary Medicine

Background:

• High preweaning lamb mortality significantly impacts the Australian sheep industry, with twin lambs experiencing higher losses.
• Previous research indicated melatonin supplementation in pregnant ewes can mitigate negative effects of fetal growth restriction and perinatal hypoxia.

Purpose of the Study:

• To investigate the efficacy of melatonin supplementation in improving the survival rates of twin Merino lambs under extensive grazing conditions.

Main Methods:

• Pregnant Merino ewes were administered one (M1) or two (M2) slow-release melatonin implants, or no supplement (CTL).
• Lamb survival, weight, and rectal temperature were monitored from birth to weaning (70.7 days).
• Serum immunoglobulin G (IgG) levels were analyzed to assess passive immunity.

Main Results:

• Melatonin treatment significantly increased lamb survival to 3 days postpartum (M1: 98.0%, M2: 95.3%) compared to controls (83.3%).
• This survival benefit was sustained to weaning (M1: 94.0%, M2: 92.5% vs. CTL: 79.6%).
• Parturition-related deaths were lower in melatonin-treated groups, suggesting a neuroprotective effect.

Conclusions:

• Melatonin supplementation in pregnant twin-bearing Merino ewes is a viable strategy to reduce neonatal mortality and improve weaning rates in extensive systems.
• The improved survival appears linked to melatonin-induced neuroprotection, though further mechanistic studies are needed.
• The study, while promising, had limitations including small sample size, necessitating further replication.