Seasonal patterns of luteal cyclicity in young red deer (Cervus elaphus) and sambar deer (Cervus unicolor)

Reproductive seasonality and rate of increase of wild sambar deer (Rusa unicolor) in a new environment, Victoria, Australia

Sambar (Rusa unicolor) are the most numerous and rapidly expanding of Australia's six introduced deer species, however, there is little information about the reproductive biology of sambar deer in their natural habitat. To better predict and manage wild sambar populations in Australia it is important to understand their reproductive seasonality and rate of population growth. From results of the present study, there is reporting of field estimates of age at first breeding, reproductive lifespan, juvenile survival, adult bodyweights and fecundity to derive estimates of the current and intrinsic rates of increase for sambar in Victoria, Australia. Mean age of first reproduction was estimated to be 1.8 years, approximately 80 % of hinds calved between April and August, juvenile survival was estimated as 0.81 and age of last reproduction 12.75 years. Seasonality of reproduction is apparently compressed at 36° latitude compared to sambar at the equator indicating a response to photoperiod. Demographic data were used to estimate the current rate of growth of the Victorian population using the two stage Lotke-Euler equation and age-specific schedules of survival and fecundity in a lifetable. These estimates of r were 0.21 and 0.14, respectively, inferring annual rates of population increase of 24 % and 15 %. These data are in the context of a population which, even though there is a marked harvesting, is reportedly growing and dispersing northwards. Suggestions for how this information can inform management decisions directed at the conservation for sustainable use and/or population reduction in Australia are made.

Impacts of nutrition on reproduction in female red deer: phenotypic flexibility within a photoperiod-mediated seasonal cycle

Red deer (Cervus elaphus) are widely distributed throughout cold northern temperate latitudes, where they have evolved to cope within highly seasonal continental environments. Naturalisation of red deer to the more moderate seasonal (but variable climatic) environment of New Zealand has been spectacularly successful, and they are widely farmed in the country’s pastoral environment for venison and antlers. The species is genetically programmed to exhibit photoperiodic control of voluntary feed intake, growth and reproduction, ensuring that energy demands are aligned with seasonally available resources and offspring are born in summer when climate is favourable for survival. However, despite genetic control of their endogenous seasonal cycles, there appears to be a strong ability for environmental factors such as nutrition to generate large phenotypic variation of seasonal traits. This may have contributed to their successful naturalisation to a wider range of seasonal environments than would be expected within their ancestral range. While precise timing of conception and duration of gestation length are the two fundamental mechanisms by which the strict seasonality of birth is maintained in seasonally breeding mammals, red deer exhibit considerable variation in both these traits. The present paper examines the outcomes of recent studies on farmed red deer on the impacts of lactation on conception date, the influence of nutrition during pregnancy on gestation length, and early life growth effects on the onset of female puberty. These studies have collectively demonstrated that while red deer are assumed to be under fairly rigorous genetic control of seasonality traits, they have a repertoire of phenotypic variation at various points of the reproductive cycle that may potentially allow a degree of adaptation to climatic variation that influences annual feed supply. This may explain the success of red deer in colonising a range of new environments that differ seasonally from their ancestral environment.

The rôles of photoperiod and nutrition in the seasonal increases in growth and insulin-like growth factor-1 secretion in male red deer

Young male red deer follow a seasonal growth pattern that can be shifted by altering the photoperiod they experience. An increase in photoperiod to 16 h of light per day (16L : 8D) during winter advances the onset of rapid growth and high food intake that normally commences in spring. These changes are associated with increased growth hormone (GH) and insulin-like growth factor-1 (IGF-1) secretion. The GH/IGF-1 axis is acutely sensitive to the level of nutrition and the relative rôles of photoperiod and nutrition in determining the spring IGF-1 rise is unknown. The present experiment set out to examine this by exposing two groups of deer (no. = 8 per group) to a photoperiod shift during their 1st year of life (16L : 8D from 2 June), designed to cause accelerated growth and increased food intake after approximately 7 weeks. However, after 6 weeks the food intake (pellets containing 11 MJ metabolizable energy and 160 g crude protein per kg dry matter (DM)) of one group (LDRES) was clamped, thereby preventing the intake component of the response. The intake of the other group (LDAL) remained ad libitum for a further 12 weeks until 6 October, when the experiment concluded.

During the first 6 weeks of 16L : 8D, growth rate (118 (s.e. 15·4) g/day) and food intake (1·37 (s.e. 0·031) kg DM per head per day) did not differ between the groups. Food intake following the clamp in LDRES averaged 1·40 (s.e. 0·015) kg per head per day. The intake of LDAL increased 2 weeks after the clamp and thereafter was higher than LDRES (P < 0·001). Food intake of LDAL averaged 2·13 (s.e. 0·051) kg during the nutritional clamp period. Growth rates increased in both groups during the first 3 weeks of the clamp, averaging 237 (s.e. 25·0) g/day, then growth slowed in LDRES and live weights diverged. Growth rates until the end of the experiment (147 (s.e.23·0) g/ day v. 299 (s.e. 12·5) g/day, P < 0·001) and mean live weight over the last 5 weeks of the experiment were lower (P < 0·05) in LDRES than LDAL, weights reaching 88·3 (s.e. 1·86) kg and 97·9 (s.e. 2·74) kg respectively on the final sampling date. Metatarsal bone length grew more in LDAL than in LDRES (3·1 v. 2·2 cm, s.e.d. = 0·23, P < 0·01). Prior to the nutritional clamp, mean plasma prolactin and IGF-1 concentrations increased at 3 and 6 weeks after 16L : 8D respectively, in both groups. Prolactin concentrations were lower in LDRES than LDAL on two occasions, at weeks 3 and 7 after the onset of the nutritional clamp, and IGF-1 concentrations were lower in LDRES than LDAL (676 v. 872 ng/ml, s.e.d. = 73·8, P < 0·05) over the last 7 weeks of sampling.

In summary, a photoperiodically driven increase in IGF-1 occurred even when the usual associated increase in food intake was prevented. This indicates that the seasonal IGF-1 rise in red deer is not a consequence of the increased food intake, although the latter appears necessary to maintain elevated IGF-1 concentrations. The rise in IGF-1 may therefore be considered as a component of the photoperiodically entrained seasonal drive to grow, and the increase in food intake a response to satisfy the increased energy demand.

Reproductive characteristics of female lesser mouse deers (Tragulus javanicus) based on fecal progestagens and breeding records

Information about breeding and the reproductive biology of mouse deer is limited in the wild and captivity. No reports on reproductive endocrinology are available. The objective of the present study was to observe the reproductive biology based on breeding records, to validate the utility of the non-invasive endocrine monitoring technique using feces of the female lesser mouse deer (Tragulus javanicus), and thus to clarify the reproductive physiology. Breeding records from 2 females were investigated and the fecal progestagen profile was monitored in captivity. Fecal progestagens were extracted using methanol and measured by enzyme immunoassay. From the breeding records, many births occurred in May (spring) and November-December (winter); however, fecal progestagen profile showed cyclical changes throughout the year in a female mouse deer. Most mounting and mating behaviors were observed 2-3 days after the peak of progestagen concentration during luteal phase. The ovarian cycle length based on the fecal progestagen profile averaged 14.5±0.3 days. The fecal progestagen concentration remained high during pregnancy. Fecal progestagen monitoring is useful for evaluating ovarian activity and pregnancy in the lesser mouse deer.

Seasonal luteal cyclicity of pubertal and adult red deer (Cervus elaphus)

Reproductive failure of rising-two-year-old (R(2)) hinds and seasonal misalignment between calving and pastoral feed production are two factors limiting reproductive productivity of farmed red deer hinds in New Zealand. This study aimed to better understand processes around female puberty and breeding seasonality by describing the potential breeding season (i.e., oestrous cyclicity) of three red deer genotypes. A total of 27 hinds born in December 2005, representing Eastern European (Cervus elaphus hippelaphus), Western European (C.e. scoticus) and F1 crossbred (C.e. hippelaphus×scoticus) red deer, were blood sampled thrice-weekly for 7-8 months (February-September/October) across two years spanning the potential breeding seasons as R(2)'s in 2007 (i.e., puberty) and as adults in 2008. Plasma progesterone profiles were used to construct breeding cycle histories for each hind. Four R(2) hinds failed to initiate oestrous cycles (i.e., puberty failure). The remaining R(2) hinds, including all F1 hinds, exhibited between two and seven oestrous cycles. F1 hinds were significantly earlier to initiate, and later to terminate, cyclic activity, resulting in a longer mean pubertal breeding season (139 days) than for Eastern (86 days) and Western hinds (86 days). However, the data for R(2) hinds are confounded by live-weight, with the F1 hinds being significantly heavier than other genotypes. There were significant correlations between live-weight and seasonality parameters in 2007. All hinds were cyclic as adults in 2008, exhibiting between four and nine oestrous cycles, and a mean breeding season duration of between 132 (Western) and 137 (F1) days. For adult hinds there were no significant genotype differences in cyclic onset and cessation timing, and no observable relationships between live-weight and any reproductive parameter. However, the mean dates for the onset of the breeding season for all genotypes in 2008 were 2-3 weeks later than normally expected for adult hinds in New Zealand. The reasons for this are unclear but may relate to chronic stress of frequent animal handling. The study has demonstrated that puberty in red deer hinds is associated with a shorter potential breeding season than for adult hinds, and that perturbation of breeding activity appears to be quite common, leading to incidences of puberty failure and possibly other aberrant cyclic events. Live-weight×genotype interactions may influence puberty but do not appear to be strongly expressed in adults. However, the relatively late onset of oestrous cyclicity in the adult hinds may be an artefact of the study that has masked genetic influences on seasonal breeding patterns.

Reproductive cycles of deer

The cervids are a complex assemblage of taxa showing extreme diversity in morphology, physiology, ecology and geographical distribution. Reproductive strategies adopted by various species are also diverse, and include a range from highly seasonal to completely aseasonal birth patterns. The recent growth in knowledge on cervid reproduction is strongly biased towards the larger-bodied, gregarious mixed grazer-browser species that have adapted well to human management and commercialisation. These species tend to represent 'K-selected' climax species characterised by very productive annual breeding success, singleton births and long breeding life (10+ years). Conversely, we know relatively little about the reproductive patterns of the 'r-selected' smaller-bodied, solitary (and often highly territorial), forest-dwelling browser species, often characterised by great fecundity (twinning) and shorter breeding life (<10 years). This group includes many of the endangered cervid taxa. This review extends earlier reviews to include more recent work on cervid reproductive cycles, particularly in relation to environmental factors influencing gestation length.

Photoperiodic requirements for rapid growth in young male red deer

Winter growth of young male red deer can be increased by exposure to 16 h of light (L) and 8 h of dark (D) per day (16L: 8D). This study tested the duration of photoperiod required for this growth response, determined if the time to reach slaughter weight can be reduced and monitored plasma IGF-1, prolactin and reproductive development. Fifty male calves were allocated to five equal groups. Four groups were housed indoors and for 33 weeks from the winter solstice (22 June, southern hemisphere) until 11 February were placed under either 16L: 8D (16L), 13·25L: 10·75D (13L), 10·751:13·25D (111) or 8L: 16D (8L) photoperiods. The fifth group of deer (OC) remained outside in a gravelled enclosure. All groups were given a pelleted diet ad libitum. Group food intake was recorded daily, individual live weight was measured weekly and testes diameter and blood samples taken at weekly or 2-week intervals.

Plasma prolactin concentrations in 16L increased within 4 weeks of treatment and were different (P < 0·001) between groups from 14 August to 4 September. IGF-1 increased in both 16L and 13L 4 weeks after treatments and then increased further in 16L above that of 13L (P < 0·01). All groups grew at the same rate for the first 7 weeks. 16L then gained more weight (P < 0·001) than the other groups over the next 19 weeks (50·7 kg v. 38·5 for 13L, 35·7 for 11L, 37·0 for 8L and 37·4 for OC; s.e.d. 3·76). Food intake was positively related to growth rate in a similar way among the inside groups (P < 0·001), however there was a higher energy requirement outdoors (P < 0·05). A target live weight for slaughter of 95 kg was reached 7 weeks earlier for 16L than the other groups (P < 0·01). Testes diameter of 16L was larger than in the other groups from 13 November until 24 December (P < 0·001). The growth oflSL slowed from 1 January while that of OC increased and the live weight ofOC was equal to 16L by the end of the experiment. OC also had the largest testes diameter from 5 February onwards (P < 0·01). The live-weight increase in OC was associated with increases in both prolactin and IGF-1 levels.

This study confirmed that 16L: 8D stimulates rapid growth of young male red deer during winter for sufficient time to achieve an earlier slaughter date. The live-weight advantage was lost by late summer however. The increased growth rate was mediated by food intake and associated with increases in IGF-1 and prolactin and earlier reproductive development. Photoperiods of 13 h of light per day or less did not stimulate growth and increases in IGF-1 and prolactin were of a lower amplitude than under 16L: 8D.

The reproductive performance of female Formosan sambar deer (Cervus unicolor swinhoei) in semi-domesticated herds

This study documented the reproductive performance of 210 adult female Formosan sambar deer (FSD, Cervus unicolor swinhoei) from four semi-domesticated deer herds in Taiwan. An extensive analysis of 525 reproductive records from 2000 to 2008, including the conditions of estrus, gestation, and parturition was conducted. The mean+/-S.E.M. lengths of the estrous cycle, gestation, and fawning interval were 18.2+/-0.5d (n=56), 258.6+/-0.3d (n=160), and 369.9+/-2.3d (n=122), respectively. Hand breeding was performed between June and December (n=494), with the majority (93.1%) occurring between July and October (P<0.05). Fawning occurred from February to September (n=318), and most frequently (83.0%) between April and June (P<0.05). Pregnancy rate per mating in FSD hinds was 64.4%. There was a 1.3:1 male-to-female ratio at birth (P<0.05) among 320 fawns, and only two cases of twinning (0.63%). The postnatal mortality rate was 6.6% (21/320), and the mortality rate in fawns before weaning did not exceed 8% on any farm. Fecundity was enhanced by high pregnancy rates and high offspring survival rates. This study provides baseline information on reproductive performance of FSD, which should be valuable to veterinarians and deer industry personnel for management of FSD on farms in subtropical countries.

Application of sensitive enzymeimmunoassays for oxytocin and prolactin determination in blood plasma of yaks (Poephagus grunniens L.) during milk let down and cyclicity

Highly sensitive and specific enzymeimmunoassays for oxytocin and prolactin determination in yak plasma using the biotin-streptavidin amplification system and the second antibody coating technique were validated and applied for determining their profiles during milk let down and cyclicity in yaks. Oxytocin EIA was conducted taking duplicate 200 microl of unknown plasma samples and standards per well. The lowest detection limit was 0.2 pg/well, which corresponded to 1pg/ml plasma. Prolactin EIA was carried out directly in 50 microl of yak plasma. The sensitivity of EIA procedure was 5 pg/well prolactin, which corresponded to 0.1 ng/ml plasma. Mean plasma prolactin concentrations although high at estrus were not statistically different (P > 0.05) from the hormone concentrations on other days. Mean plasma prolactin concentrations during non-breeding season were significantly higher (P < 0.001) than that recorded in breeding season. Oxytocin and prolactin profiles were also obtained in two yaks before, during and after milking. A sharp release of oxytocin and prolactin shortly after udder stimulation was observed. High levels of oxytocin and prolactin were maintained during milking, falling sharply thereafter.

Characteristics of the oestrous cycle of Iberian red deer (Cervus elaphus hispanicus) assessed by progesterone profiles

This study examines the length of the oestrous cycle in 16 Iberian red deer females assessed by means of changes in progesterone concentrations, along with the changes in the profile of this hormone. Samples were collected three occasions per week from the week after calving (15 May to 15 June) up to May of the following year. The oestrous cycle lasted 19.57+/-0.29 days (range 10-27 d) calculated in 130 oestrous cycles examined. Progesterone titres did not rise above 0.5 ng/ml in the follicular phase, except in four samples. The maximum peak in progesterone concentration during the luteal phase remained above 1 ng/ml in most cases. Twenty-five percent of the individuals studied (4 out of 16) showed an oestrous cycle lasting shorter than the mean (15.2+/-0.30 days) before the start of the reproductive season, followed by a period of sexual inactivity. The standard progesterone profile in natural oestrous cycles rose from basal levels to those above 0.5 ng/ml four days after onset of oestrus, reached a peak of 1.71+/-0.07 ng/ml and then declined to less than 0.2 ng/ml after day 20. Following the rapid decline of progesterone after day 14, the concentration remained around the baseline level of 0.1 to 0.2 ng/ml during the immediate pre- and post-ovulatory phase of the cycle.

Reproductive seasonality in female Iberian red deer (Cervus elaphus hispanicus)

This study characterized the seasonal pattern of luteal cyclicity in Iberian red deer (n=16), by measuring plasma progesterone concentrations in hinds (female red deer) twice per week from calving (May and June) 1996 until May 1997. In eight of these hinds we also examined plasma prolactin profiles to assess seasonal responses to photoperiod. Plasma progesterone concentration in the 16 hinds studied indicated that the reproductive pattern is seasonal, and lasts for 5.73 +/- 0.27 months. After calving, progesterone levels remained basal (no luteal activity) for several months, except in a hind that lost her calf just after calving, and thus did not have to suckle it. This hind showed two consecutive estrus cycles in the month following calving, which suggests that suckling has an inhibiting effect on the resumption of ovarian activity. These results also showed that as long as the hinds do not become pregnant, they show between 5 and 10 estrus cycles per reproductive season (8.06 +/- 0.35), ranging between 105 and 249 days from onset of the first cycle to end of the last one. Uninterrupted cycling lasted for 3.5-6.4 months (mean, 4.6 +/- 0.24). Cyclic luteal activity was found from October to February in all hinds, with a smaller, but notable proportion in September (56.25%) and March (68.8%), whereas it was negligible in the remaining period. Our results show a reproductive season similar to or longer than that recorded by other authors. Prolactin plasma concentrations showed a yearly trend following that of photoperiod, with peak concentrations from April to July, a decrease in August, minimal concentrations from September to February and a sharp increase in March.

Annual ovarian cycles in an aseasonal breeder, the springbok (Antidorcas marsupialis)

The springbok is an arid-adapted antelope inhabiting the desert and semidesert regions of southern Africa. Because it thrives in these sparsely vegetated areas, the springbok is of potential agricultural importance and the prospect of domestication has been speculated for many years. However, apart from observational studies on its breeding in the wild, suggesting it is an aseasonal breeder, little is known about the underlying reproductive endocrinology of this species. In this study, biweekly peripheral blood samples were collected from eight captive springbok ewes from October 1995 until September 1998 and analyzed for progesterone. At the start of the study, six ewes were prepubertal and cycling commenced spontaneously between November 1995 and June 1996. Cycling had already commenced in two ewes. At the end of November 1996, estrous cycles ceased abruptly in all ewes and restarted in April 1997. Cycling ceased again between December 1997 and February 1998 and restarted in June 1998 in six ewes; there was no cessation of estrous cycles in two ewes. Thus, although some individuals cycle continuously, there is a clear endocrine anestrus of between 4 and 5 mo in springbok, the timing and duration of which is synchronized between some individuals but the time of onset and cessation is variable from year to year. To ensure that the fluctuations we observed in progesterone levels were reliable indicators of changes in the estrous cycle, blood samples were collected every 6 h for 16 days in August 1998. A surge in LH secretion was observed in all ewes 55 +/- 5 h after the fall in progesterone. Progesterone levels increased again 45 +/- 8 h after the surge. A final study showed that the pattern of melatonin release in springbok exhibits a normal day/night profile, and thus photoperiodic information is transformed into an endocrine code to springbok but does not appear to affect reproduction. Rather, our data raise the possibility that the prevailing ambient temperature may influence the onset of ovarian activity in this species.