Undernutrition and exogenous melatonin can affect the developmental competence of ovine oocytes

M. I. VAZQUEZ; F. FORCADA; A. CASAO; J.A. ABECIA; C. SOSA; I. PALACIN

REPRODUCTION IN DOMESTIC ANIMALS (1990)

WILEY-BLACKWELL PUBLISHING, INC

Año: 2010 vol. 45 p. 677 - 684

0936-6768

This study evaluated the effects of exogenous melatonin andlevel of nutrition on oocyte competence, in vitro fertilization(IVF), and early embryonic development in sheep duringseasonal anoestrus (SA) and the reproductive season (RS).Adult Rasa Aragonesa ewes were assigned randomly to one offour treatment groups in two experiments based on a 2 · 2 · 2factorial design. Individuals were treated (+MEL) or nottreated ()MEL) with a subcutaneous implant of melatonin for42 days and then were fed 1.5 (Control, C) or 0.5 (Low, L)times the daily maintenance requirements for 20 days. Eweswere synchronized and mated at oestrus (Day = 0). On Day5, ovaries were collected and oocytes were used for IVF.Season had a significant (p < 0.01) effect on the number ofoocytes recovered (RS: 19.6 ± 1.0; SA: 14.5 ± 1.0) and thenumber of healthy oocytes (RS: 13.9 ± 0.7; SA: 9.0 ± 0.7).In the RS, neither nutrition nor melatonin had a significanteffect on the evaluated oocytes quality parameters althoughmelatonin implants appeared to reduce the number ofunhealthy oocytes in the undernourished group (p < 0.05).During SA, in undernourished ewes exogenous melatonintended to increase the number of healthy (L+MEL:9.4 ± 1.0, L)MEL: 7.6 ± 1.4; p < 0.1), and significantlyimproved both cleaved oocytes (L+MEL: 7.0 ± 0.7,L)MEL: 4.1 ± 0.9; p < 0.05) and blastocyst rate(L+MEL: 37.2, L)MEL: 21.9%; p < 0.05). In conclusion,oocyte competence in ewes was affected by season, andmelatonin implants appeared to improve developmental competencein the seasonal anoestrous period, particularly inexperimentally undernourished ewes.