A comparison of the seasonal hormone changes and patterns of growth, voluntary food intake and reproduction in juvenile and adult red deer (Cervus elaphus) and Père David's deer (Elaphurus davidianus) hinds

Abstract

Non-domesticated seasonally breeding ungulates exhibit marked seasonal changes in metabolic rate, voluntary food intake (VFI), pelage growth and moult and hormone secretion. It is not known whether these seasonal rhythms are regulated by the same central processes which control the onset and termination of the breeding season. Here we compare two closely related deer species which have significantly different mating and calving seasons. Seasonal changes in VFI, liveweight, coat growth, plasma prolactin and tri-iodothyronine (T3), and the timing of the breeding season were examined over a 15-month period in six adult post-pubertal red and Père David's deer from January to April the following year. The timing of the seasonal changes in prolactin, T3, VFI and coat growth were all significantly advanced by 56, 23, 60 and 54 days respectively in the Père David's deer. The times of onset and termination of the breeding season of Père David's deer were also significantly advanced by 90 days, but in both species, the breeding season was of similar duration (160 +/- 5 (S.E.M.) days). Changes in liveweight of adult red deer could be explained by changes in VFI rather than efficiency of utilization. This was not the case in Père David's deer and may indicate seasonal changes in the efficiency of energy utilization. In order to establish whether these species differences develop with age, we undertook a second study in which seasonal changes in VFI, growth, plasma prolactin concentrations and the timing of the onset of the breeding season were recorded for ten red deer and six Père David's deer from 6 to 18 months of age. Both species exhibited a similar decline in VFI in the first autumn of life. Subsequently, the Père David's deer exhibited an advance in the timing of the seasonal peak in VFI and prolactin (21 and 66 days respectively); puberty occurred 3 months earlier than in red deer. The earlier breeding season of the Père David's deer was associated with a significant advance in a range of seasonal endocrine and physiological parameters. These species differences may develop with age. Our data indicate that seasonal patterns of metabolism and growth may be closely linked to those mechanisms which also regulate the onset and termination of the breeding season.

GH as a co-gonadotropin: the relevance of correlative changes in GH secretion and reproductive state

“…Since GH regulates intermediary metabolism, many of these cycles appear to be related to changes in food intake, rather than changes in photoperiod, temperature or other environmental parameters. However, as seasonal patterns of metabolism and food intake are often closely linked to the onset and termination of seasonal breeding, seasonal changes in GH secretion may occur coincident with reproductive cycles, as occurs in adult red deer and Père David's deer (Loudon et al 1989, Webster et al 1996 and white-tailed deer (Bubenik et al 1975). Male reindeer also have high plasma GH levels during the rutting season, when food intake is low (Suttie et al 1992).…”

Ultradian, circadian and seasonal rhythms in cortisol secretion and adrenal responsiveness to ACTH and yarding in unrestrained red deer (Cervus elaphus) stags

“…These include changes in secretion of hormones involved in the reproductive (Lincoln & Kay 1979, Suttie et al 1992) and growth and metabolic (Suttie et al 1989) axes. Changes in behaviour at this time include increased aggression (Suttie 1985) and a reduced voluntary food intake (Loudon et al 1989) resulting in pronounced weight loss (Kay 1979). It is well documented in other mammalian species that HPA axis activity can be modulated by changes in reproductive function (increased activity and responsiveness in castrates compared with entire males (Bass et al 1982, Verkerk & Macmillan 1997) and changing metabolic and growth demands (Yanovski et al 1997) as well as by social factors (Lyons et al 1988).…”

Carcass composition comparison of male and female red deer and hybrids with Père David's deer

“…Female pure Pere David's deer have a 70% greater mature live weight than reds (Loudon et al 1989). Heterosis could not be calculated in this experiment as pure PD were not run with the hybrid and red genotypes.…”

“…On this basis, the expected live weight of the pure PDs would be 4 x 8% = 32%. In fact, the difference between these genotypes reported by Loudon et al (1989) was 70%. Even with some allowance for a genotype by environment interaction, this suggests that the backcross hybrids in the current study (reared indoors) performed well below expectation as males and females achieved live weights 2.6% and 1.9% lower than red deer, respectively.…”

“…Red deer differ markedly from Pere David's deer (Elaphurus davidianus, PD) in terms of seasonally (breeding cycle is about three months earlier in PD (Loudon et al 1989)) and mature size (PD females are about 70% larger). There are also differences between these species in their behaviour (Altmann & Scheel 1980), morphology (Wemmer 1983), and disease resistance (Orr & Mackintosh 1988).…”