Reprod. Nutr. Dev. 46 (2006) 367-378
DOI: 10.1051/rnd:2006018

The effect of undernutrition on the establishment of pregnancy in the ewe

José-Alfonso Abecia^a, Cecilia Sosa^{a, b}, Fernando Forcada^a and Ana Meikle<sup>b

a</sup>  Animal Production and Food Science, Faculty of Veterinary Medicine, Miguel Servet, 177. 50013 Zaragoza, Spain
^b  Biochemistry, Faculty of Veterinary Medicine, Lasplaces 1550, Montevideo 11600, Uruguay

(Published online 7 July 2006)

Abstract - The relationship between nutrition and reproduction in sheep has been the subject of research in several international groups. This review will particularly focus on the effects of undernutrition on the potential causes of reproductive failure including abnormalities of the ovum or the embryo, luteal inadequacy and failure of the supply of progesterone to the uterus, or the mechanisms involved in maternal recognition of pregnancy. The level of nutrition and peripheral progesterone concentrations are inversely related, and increased rates of embryo loss, associated with higher progesterone concentrations in ewes with low levels of nutrition have been reported. Undernutrition may act through changes in the distribution of progesterone in the endometrium. Thus, lower endometrial levels on day 5 of the cycle in ewes fed half of their maintenance requirements have been observed, providing a link between the known role of progesterone in embryo survival by the modulation of uterine function and the higher embryo losses found in undernourished ewes. The evidence of an effect of maternal nutrition on IFN secretion from the conceptus and of PGF production from the uterus is presented. Moreover, undernutrition provokes a reduction in the sensitivity of the endometrium to progesterone that may affect embryo survival. Finally, a state of undernutrition induces changes in the endometrial sensitivity to steroid hormones at early stages of pregnancy that could adversely alter uterine environment to the detriment of embryo survival.

Key words: sheep / nutrition / reproduction / progesterone / embryo

Corresponding author: alf@unizar.es

© INRA, EDP Sciences 2006