Effects of exogenous melatonin on in vivo embryo viability and oocyte competence of undernourished ewes after weaning during the seasonal anestrus

M. I. VAZQUEZ; J.A. ABECIA; F. FORCADA; A. CASAO

THERIOGENOLOGY

ELSEVIER SCIENCE INC

Año: 2010 vol. 74 p. 618 - 626

0093-691X

This study investigated the effects of exogenous melatonin on embryo viability and oocyte competence in post-partumundernourished ewes during the seasonal anestrus. At parturition (mid-Feb), 36 adult Rasa Aragonesa ewes were assigned to oneof two groups: treated (MEL) or not treated (MEL) with a subcutaneous implant of melatonin (Melovine®, CEVA) on theday of lambing. After 45 d of suckling, lambs were weaned, ewes were synchronized using intravaginal pessaries, and fed toprovide 1.5 (Control, C) or 0.5 (Low, L) times daily maintenance requirements. Thus, ewes were divided into four groups:CMEL, CMEL, LMEL, and LMEL. At estrus (Day0), ewes were mated. At Day 5 after estrus, embryos were recoveredby mid-ventral laparotomy and classified based on their developmental stage and morphology. After embryo collection, ovarieswere recovered and oocytes were classified and selected for use in in vitro fertilization (IVF). Neither diet nor melatonin treatmenthad a significant effect on ovulation rate and on the number of ova recovered per ewe. Melatonin treatment significantly improvedthe number of fertilized embryos/corpus luteum (CL) (MEL: 0.35 0.1, MEL: 0.62 0.1; P 0.08), number of viableembryos/CL (MEL: 0.23 0.1, MEL: 0.62 0.1; P 0.01), viability rate (MEL: 46.6%, MEL: 83.9%; P 0.05), andpregnancy rate (MEL: 26.3%, MEL: 76.5%; P 0.05). In particular, exogenous melatonin improved embryo viability inundernourished ewes (LMEL: 40%, LMEL: 100%, P 0.01). Neither nutrition nor exogenous melatonin treatmentssignificantly influenced the competence of oocytes during IVF. Treatment groups did not differ significantly in the number ofhealthy oocytes used for IVF, number of cleaved embryos, or number of blastocysts and, consequently, the groups had similarcleavage and blastocyst rates. In conclusion, melatonin treatments improved ovine embryo viability during anestrus, particularlyin undernourished post-partum ewes, although the effects of melatonin did not appear to be mediated at the oocyte competencelevel.