January 21, 2021

Interpretive Summary: Supplementing Merino ewes with melatonin during the last half of pregnancy improves tolerance of prolonged parturition and survival of second-born twin lambs

Interpretive Summary: Supplementing Merino ewes with melatonin during the last half of pregnancy improves tolerance of prolonged parturition and survival of second-born twin lambs

By Anne Zinn

High preweaning mortality rates continue to limit sheep production globally and continues to be a major economic concern. There is greater loss in twin lambs compared with singletons, which is often attributed to lower birth weight and increased risk of intrapartum hypoxia, leading to impairment of thermoregulation, neuromotor activity, and maternal bonding behavior. Previous research has 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. Therefore, a study recently published in the Journal of Animal Science investigated whether supplementing ewes with melatonin throughout late pregnancy would improve lamb survival, birth weight, and behavior under intensive conditions. The Australian research team hypothesized that melatonin would improve lamb birth weight, suckling behavior, thermogenesis, tolerance of prolonged parturition, and survival to weaning.

The results of this study provide the first evidence that melatonin supplementation during the second half of pregnancy improves twin lamb survival, especially in second-born twins and those exposed to prolonged parturition. Both delivery methods, orally and implanted, resulted in positive lamb outcomes, with slightly greater improvement in orally treated ewes.These results suggest that melatonin implants have the potential to be a simple and cost effective strategy to reduce neonatal losses of twin lambs on farms; results also highlight the potential for further studies into the neuroprotective effects of melatonin on lambs exposed to prolonged parturition and pregnancies in which fetal growth is impacted by restricted maternal nutrition. These observed outcomes in twin Merino lambs provide a solid basis for further testing in other breeds and extensive production systems.

The full study can be found on the Journal of Animal Science website.