Effect of melatonin treatment of pregnant Sarda ewes on lactation and lamb development.

Context Melatonin administration during pregnancy can influence fetal development and lactation. Aims This study aimed to verify whether melatonin treatment of pregnant Sarda ewes in spring improved lamb weight at birth, 7 and 21days of age, time to first colostrum intake, birth behavior and survival. Additionally, we examined melatonin's effect on milk yield and composition. Methods On 18 April, 200 ewes were assigned to two groups of 100 each, based on lambing date, body condition score, parity, age and milk yield. One group received melatonin implants on 20 April, 4 July and 17 September; the other served as control. Rams (12 per group) were introduced on 25 May and removed after 40days. Lamb weight was recorded at birth, 7 and 21days, while milk yield and composition were assessed bi-weekly from day 30 of lactation. Key results Lambs born to melatonin-treated ewes were heavier at birth (3.54 vs 2.89kg), and at 7(5.21 vs 4.40kg) and 21days of age (11.3 vs 10.1kg) and reached colostrum intake sooner than lambs from untreated ewes (55.5±5.3 vs 69.4±5.6min). Milk yield was higher in melatonin-treated ewes, with somatic cell counts decreasing in treated animals and increasing in controls over the five samplings. Milk fat was higher in treated ewes than controls during early lactation, although protein and lactose levels remained similar between groups. Conclusion Melatonin treatment throughout pregnancy improved lamb growth and milk production and quality, suggesting a potential management advantage for sheep.