Can advance of first lambing induced by melatonin implants influence the next lambing time in Sarda breed sheep?

Abstract

Carcangiu, V., Mura, M. C., Bini, P. P., Vacca, G. M., Daga, C. and Luridiana, S. 2012. Can advance of first lambing induced by melatonin implants influence the next lambing time in Sarda breed sheep? Can. J. Anim. Sci. 92: 67–71. In adult sheep, exogenously administered melatonin from continuous slow-release implants has been shown to advance the onset of the breeding season by mimicking the stimulatory effect of short days. The aim of this study was to verify if treatment with one or two melatonin implants was effective in advancing the first conception in Sarda ewe lambs, and if this advance would also be seen in the second lambing too. In the first year, 600 ewe lambs were randomly assigned to groups M, M+M and C, each with 200 animals. On Jun. 30, group M received a single implant while group M+M received two implants. Group C was untreated. On Aug. 04, 25 rams were introduced in the groups and removed after 70 d. From these 600 animals the 420 head that lambed prior to Mar. 12 were chosen for the second year. These ewes were subdivided into two groups T1 (ewes who lambed between 2007 Jan. 01 and Feb. 10) and T2 (ewes which lambed between 2007 Feb. 11 and Mar. 12). Both in T1 and T2 the distribution of the animals in M, M+M and C group was maintained. In the first year, the treated animals lambed earlier (P<0.05) and showed higher numbers of lambed ewes at Feb. 10 (P<0.01) and at March 12 (P<0.05) compared with untreated control animals. The animals that showed an advance in the period of their first conception, also showed, in the second breeding year, an advance in the lambing time (P<0.001). This study provides evidence that the advance of first conception, obtained with melatonin treatment also influenced the reproductive activity in the following breeding season.