Seasonal changes in melatonin concentrations in female Iberian red deer (Cervus elaphus hispanicus)

Abstract

: In deer, most of the earlier investigations on pineal function examined the effects of artificial photoperiods or the administration of melatonin to manipulate reproduction. However, endogenous melatonin rhythms have not been studied in red deer. Thus, we monitored seasonal changes in plasma melatonin concentrations in 16 adult female Iberian red deer living in outdoor enclosures. Blood was sampled on the day of each seasonal change every 3–4 hr overnight and 1 hr before and after sunset and sunrise. In addition, in six of the previous hinds, blood sampling during the hour prior and after sunset and sunrise was collected every 20 min. Significant differences were found both in amplitude and duration of the nocturnal plasma melatonin profiles in the four seasonal changes (P<0.01). The nocturnal mean level of melatonin, the duration of nocturnal secretion levels and maximal concentrations were significantly higher at the winter solstice than in summer solstice or equinoxes (P<0.05). Moreover, the mean overnight concentrations were significantly higher at the spring equinox and winter solstice than during the summer solstice and autumn equinox (P<0.05). A pronounced elevation from low levels was recorded 1 hr after sunset, remained elevated during the hours of darkness and declined to low levels 1 hr after dawn. Concentrations close to sunrise were higher than those near sunset at all changes of season (P<0.05). These results show for the first time in red deer that the pineal gland of the adult female is highly responsive to both daily and seasonal changes in natural environmental illumination, although overnight levels lasted longer than the photoperiodic night is all cases, particularly at the winter solstice.

Seasonal variations in the nycthemeral rhythm of plasma melatonin in the camel (Camelus dromedarius)

“…The amplitude of the nocturnal melatonin peak showed large inter‐individual variations from about 20–200 pg/mL in the camels we studied. These levels are similar to those reported in three female camels in south of France [21] and close to those reported in the wild red deer [27], in goats [28] and in man [29] varying from 50 to 100 pg/mL. However in sheep, melatonin peak levels are much higher ranging from 100 to 600 pg/mL [30, 31], while in other domestic species such as pig, melatonin concentrations are much lower ranging from 10 to 30 pg/mL [18].…”

Seasonal variations in red deer (Cervus elaphus) hematology related to antler growth and biometrics measurements

“…Animals were maintained in a 10,000 m 2 fenced enclosure and were fed ad libitum on barley straw and meal from barley, alfalfa, oat, and sugar beets (16% crude protein, 11% humidity, whole meal composition described by Landete‐Castillejos et al, 2007a). Natural photoperiod oscillated between 9 (December) and 15 (June) hr light/day (García et al, 2003). …”

“…After casting, the new antler grows and at the end of summer it is cleaned from velvet (Suttie et al, '91). This cycle is controlled by seasonal endocrinological changes (Suttie et al, '91; Gaspar‐López et al, 2010) that are triggered by the transduction of the photoperiod by the pineal gland (García et al, 2003). These endocrine signals have been reported to affect hematopoiesis in other species (Pages et al, '92; Sletvold et al, '98).…”

Plasmatic protein values in captive adult Iberian red deer stags (Cervus elaphus hispanicus)

“…Deer were fed ad libitum on barley straw and meal from barley, alfalfa, oat and sugar beets (16% crude protein, 11% humidity, whole meal composition described by Landete-Castillejos et al [10]). The natural photoperiod oscillated between nine (December) and 15 (June) hours of light/day [11].…”