Free Access
Reprod. Nutr. Dev.
Volume 46, Number 4, July-August 2006
Symposium: Influence of nutrition and socio-sexual context on reproduction and survival of the young in goats and sheep
Page(s) 355 - 365
Published online 07 July 2006
Reprod. Nutr. Dev. 46 (2006) 355-365
DOI: 10.1051/rnd:2006017

The effect of nutrition on the seasonality of reproduction in ewes

Fernando Forcada and José-Alfonso Abecia

Departamento de Producción Animal y Ciencia de los Alimentos, Universidad de Zaragoza, Miguel Servet 177, 50013 Zaragoza, Spain

(Published online 7 July 2006)

Abstract - The beneficial effects of nutrition on reproduction in sheep have been described, particularly on ovulation rate. However, the relationships between nutrition and reproductive seasonality are not well known. This review will deal with the effects of body fat or food intake on sexual and hypothalamic/pituitary activity in sheep, mainly focused on Mediterranean genotypes. Although only severe malnutrition can significantly extend the length of the seasonal anestrous period, the level of fat reserves can play a significant role on reproductive seasonality delaying the onset of seasonal anoestrus, particularly on the Mediterranean environment. The effect of overfeeding on LH secretion has also been reported, specially at short term. Several experimental approaches have elucidated that both high body fat and food intake are able to modify the sensitivity of the hypothalamus to oestradiol negative feedback during seasonal anoestrus, with those effects being associated to a reduced amount of NPY mRNA and to an increase of plasma insulin, glucose and leptin concentrations, particularly in the late scenario. However, the highest receptivity to nutritional stimulation in terms of increasing LH occurs when ewes are subjected to a photoperiodic state of early anoestrus or late breeding season rather than under a photoperiod characteristic of the end of anoestrus or the beginning of the breeding season.

Key words: sheep / nutrition / reproductive seasonality / gonadotropins

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© INRA, EDP Sciences 2006