Impact of food deprivation on ova transport 53 food at days 10-11 of pregnancy (Tsuma et al. 1996a) and direct after ovulation (Mburu et al. 1998). One reason for this may be that the effect of fasting on the plasma P4 level occurs later than 36 h after the onset of food deprivation, meaning that such a change could not have been detected in the present study. It may be that in our study the period of food deprivation was not long enough to substantiate any differences between the groups with re- spect to blood serum levels of glucose and tri- glycerides. Since stress induced glucocorticoid secretion stimulates glycogenesis and lipolysis, the food deprived animals would initially com- pensate for the lack of energy intake (Varley et al. 1994). This is conﬁrmed by the signiﬁcantly higher level of free fatty acids seen in the fasted sows while the low energy intake resulted in a signiﬁcantly lower level of insulin during the fasting period. These endocrine changes indi- cate that the fasted sows were in a catabolic state, which is in agreement with the ﬁndings of Mburu et al. (1998) and Mwanza et al. (2000a). Insulin is thought to be one of the mediators of energy metabolism status and the reproductive development in prepubertal gilts (Booth et al. 1996). Further investigation is required in order to establish the importance of insulin as a medi- ator of nutritional effects and reproductive per- formance in sows. The decrease in the transport rate of the ova could also be due to a change in the composi- tion of oviductal ﬂuid. The oviductal ﬂuid is formed by selective transudation from the blood and active secretion from the endosalpinx (Hunter 1988). Accumulation of ﬂuid in the ov- iductal lumen is programmed by the concentra- tion of oestrogens and P4 and there is evidence, to suggest that porcine oviductal tissue synthe- sizes speciﬁc oestrous-associated proteins at the time of fertilisation (Buhi et al. 1990, Mur- ray 1993). It may therefore be speculated that a non-physiological hormonal change detected in the peripheral circulation could also affect the composition of the oviductal ﬂuid as well as the oviductal transport of the ova. Conclusions It can be concluded that stress induced by food deprivation immediately after ovulation de- creased the concentration of insulin and in- creased the levels of free fatty acids and PGF2α metabolite but had no effect on the levels of glucose, triglycerides or P4. Stress due to fast- ing also delayed ova transport through the isth- mic part of the oviduct, which is probably an ef- fect of many causes. One of these could be a prolonged α-adrenergic response (contrac- tions) in the smooth circular muscle layers around the isthmus, although the exact mecha- nism of this phenomenon has to be further eval- uated. Acknowledgements The authors wish to thank The Swedish Council for Forestry and Agricultural Research and Swedish Meats for ﬁnancial support, Lotta Sundström for an- alysing the PGF2α-metabolite and Dr. Mats Forsberg for his help with analysing the other blood parame- ters. Heléne Gille, Carola Jansson, Mari Wallbring, Ulrika Mattsson and Kjell-Ove Eklund are gratefully acknowledged for their help with the experimental animals. References Ashworth CJ: Effect of pre-mating nutritional status and post-mating progesterone supplementation on embryo survival and conceptus growth in gilts. Anim. Reprod. Sci. 1991, 26, 311-321. Booth PJ, Cosgrove JR, Foxcroft GR: Endocrine and metabolic responses to realimentation in feed-re- stricted prepubertal gilts: associations among go- nadotropins, metabolic hormones, glucose, and uteroovarian development. J. Anim. Sci. 1996, 74, 840-848. Brouns F, Edwards SA: Social rank and feeding be- haviour of group-housed sows fed competitively or ad libitum. Appl. Anim. Behav. Sci. 1994, 39, 225-235. Buhi WC, Alvarez IM, Sudhipong V, Dones-Smith MM: Identiﬁcation and characterisation of de Acta vet. scand. vol. 42 no. 1, 2001