Seasonal alterations in circadian melatonin rhythms of the European wild boar and domestic gilt

Abstract

The aims of the present study were: 1) to determine if the European wild boar exhibits a circadian pattern of melatonin secretion under its natural light environment; 2) to compare this pattern with the pattern in domestic pigs reared under the light environment typical for domesticity; and 3) to determine if there are seasonal alterations in melatonin rhythms. Four to six young, pure-bred, European wild boars and four to six cross-bred (Yorkshire x Finnish Landrace) domestic gilts were sampled at 2-hr intervals for 48 hr at the spring/autumn equinoxes and summer/winter solstices. Samples were obtained via saphenous arterial catheters from the wild boars and via ear vein catheters from the domestic gilts. The ambient light intensity was recorded simultaneously with sampling both outdoors and indoors. Following ether extraction, the serum samples were assayed for melatonin using a commercial RIA (Bühlman). All the experimental animals exhibited a distinct circadian pattern in melatonin secretion, with high concentrations occurring during the scotophase. There was no difference in scotophase melatonin response between the wild boars and domestic gilts in any season in terms of mean melatonin concentration or peak value. The mean duration of increased melatonin secretion (more than two standard deviations over a mean photophase concentration) in 24 hr in the wild boars in spring, summer, autumn and winter, was 10, 6, 11 and 17 hr, respectively, and in the domestic gilts, 9, 8, 12 and 11 hr, respectively. These results demonstrate the existence of circadian rhythm in melatonin secretion in both the European wild boar and domestic pig. In both groups, the duration of secretion is subject to seasonal alterations. The results suggest no difference in photoperiodic-melatonin transduction between the European wild boar and domestic pig whether due to altered genotype or reduced light environment.

The influence of boar breed and season on semen parameters

“…It is well known that the conditions under which boars are maintained have a significant impact on the quality of their ejaculates (Corcuera et al, 2002). It is believed that during domestication pigs lost their diurnal rhythm of melatonin secretion or it just weakened (Tast et al, 2001). Mediterranean climate research on photoperiod in boars showed no significant differences in semen parameters analysed, although there was a change in concentration and motility (Rivera et al, 2005).…”

“…The quantity and quality of ejaculates are affected by animal and environmental factors such as breed, age, feeding, health status and season (Cheon et al, 2002). The seasonality of breeding performance in sows and boars is often discussed in the literature (Peltoniemi et al, 2000;Strzeżek et al, 2000;Basset et al, 2001;Tast et al, 2001). Changes in the composition of semen during the year may vary between 25% and 30% (Colenbrander & Kemp, 1990).…”

Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters

“…Several examples of photoperiodic variation in the amplitude of the MEL peak have been observed, for example, in the pig (McConnell and Ellendorf, 1987;Taste et al, 2001), mule , Siberian hamster (Lerchl and Schlatt, 1992;Steinlechner et al, 1995;Miguez et al, 1996;Ribelayga et al, 2000), European hamster (Vivien-Roels et al, 1992, 1997, and horse (Guérin et al, 1995). Annual variations in the amplitude of the nocturnal MEL peak are especially visible when animals are maintained in their natural environment.…”

Effects of season and regulated photoperiod on the reproductive performance of sows

“…Long light duration on lactating sows has an indirect positive influence on the return to oestrus after weaning via an increase in appetite. It has been shown that pigs adjust their circadian melatonin secretion according to changes in photoperiod (Tast et al, 2001a). Bassett et al (2001) found that melatonin implants which were inserted at the spring equinox were able to prevent seasonal anoestrus, thus providing further support for the contention that the duration of the daily photoperiod is the primary determinant of the reproductive seasonality.…”

“…The pattern of melatonin secretion transduces information of lighting conditions to the endocrinological control system of gonadotrophins in the hypothalamus (Malpaux et al, 1996;. A circadian secretion pattern of melatonin in the domestic pig is similar to that of the European wild boar (Sus scrofa), which is a short day breeder (Mauget, 1982;Tast et al, 2001a). There is preliminary evidence that reduced fertility traits due to changes in day length can be corrected by a simple and effective light programme (Foxcroft, 1997).…”