Melatonin concentrations in the two jugular veins, and relationship with the seasonal reproductive activity in goats

Abstract

16We investigated whether melatonin concentrations vary between the two jugular 17 veins and whether absolute (nocturnal) or relative (nocturnal/diurnal ratio) plasma 18 melatonin concentrations are associated with seasonal reproductive activity measured 19 by oestrous or ovulatory activity in Payoya goats. Thirty-two adult Payoya goats were 20 penned under natural photoperiod. Oestrous activity was tested daily using aproned 21 males -twice a week plasma was sampled for progesterone. Melatonin plasma 22concentrations were studied at each equinox and solstice of the year in jugular samples 23 taken simultaneously by venipuncture. Nocturnal and diurnal plasma melatonin 24 concentrations from each jugular vein were assessed in 3 and 2 plasma samples per 25 goat, respectively, taken at hourly intervals in each period. No differences in melatonin 26 concentrations between the two veins were observed, but there was a significant 27 interaction (P<0.001) between jugular vein and animal in nocturnal melatonin 28 concentrations. There was no effect of sampling period on melatonin concentrations and 29 the coefficient of correlation between sampling periods was very high. The analyses 30 performed indicated that neither absolute nor relative melatonin concentrations were 31 related with the dates of onset or end of ovulatory/oestrous activity. Therefore, we 32 concluded that in goats (1)

Effects of melatonin implantation on cashmere yield, fibre characteristics, duration of cashmere growth as well as growth and reproductive performance of Inner Mongolian cashmere goats

“…Reproductive activity in goats shows an annual pattern with a period of breeding activity occurring when day length is decreasing, and the onset of seasonal anoestrus when day length is increasing [25]. Investigation of the effects of exogenous melatonin on the reproductive performance has seldom been conducted in cashmere goats.…”

Annual Change of Reproductive Hormones in Female Angora Goats

“…The most important environmental factor affecting the seasonal reproduction dependence in small ruminants is the annual change in day length (photoperiod). (Zarazaga et al, 2010;Fatet et al, 2011, Abecia et al, 2012.…”

Trends in goat research, a review

“…In the same field, Valencia et al (2010) investigated the effect of male exposure on luteolytic activity, concluding that during the reproductive season, the introduction of the buck to a group of cyclic goats does not exert a luteolytic effect and consequently does not anticipate the next oestrus. Zarazaga et al (2010) observed the melatonin concentrations in the two jugular veins and the relationship with the seasonal reproductive activity in goats. The authors concluded that melatonin is highly variable between jugular veins in the same individual and absolute and relative amplitudes of melatonin concentrations are not linked to the seasonal breeding activity in Mediterranean goats.…”