Influence of level of nutrition during late pregnancy on reproductive productivity of red deer I. Adult and primiparous hinds gestating red deer calves

Plasticity and repeatability in spring migration and parturition dates with implications for annual reproductive success

In seasonal environments, animals should be adapted to match important life-history traits to when environmental conditions are optimal. Most animal populations therefore reproduce when resource abundance is highest to increase annual reproductive success. When facing variable, and changing, environments animals can display behavioural plasticity to acclimate to changing conditions. Behaviours can further be repeatable. For example, timing of behaviours and life history traits such as timing of reproduction may indicate phenotypic variation. Such variation may buffer animal populations against the consequences of variation and change. Our goal was to quantify plasticity and repeatability in migration and parturition timing in response to timing of snowmelt and green-up in a migratory herbivore (caribou, Rangifer tarandus, n = 132 ID-years) and their effect on reproductive success. We used behavioural reaction norms to quantify repeatability in timing of migration and timing of parturition in caribou and their plasticity to timing of spring events, while also quantifying phenotypic covariance between behavioural and life-history traits. Timing of migration for individual caribou was positively correlated with timing of snowmelt. The timing of parturition for individual caribou varied as a function of inter-annual variation in timing of snowmelt and green-up. Repeatability for migration timing was moderate, but low for timing of parturition. Plasticity did not affect reproductive success. We also did not detect any evidence of phenotypic covariance among any traits examined-timing of migration was not correlated with timing of parturition, and neither was there a correlation in the plasticity of these traits. Repeatability in migration timing suggests the possibility that the timing of migration in migratory herbivores could evolve if the repeatability detected in this study has a genetic or otherwise heritable basis, but observed plasticity may obviate the need for an evolutionary response. Our results also suggest that observed shifts in caribou parturition timing are due to plasticity as opposed to an evolutionary response to changing conditions. While this provides some evidence that populations may be buffered from the consequences of climate change via plasticity, a lack of repeatability in parturition timing could impede adaptation as warming increases.

Tissue tectonics and the multi-scale regulation of developmental timing

Development encompasses processes that occur at multiple length scales, including gene-regulatory interactions, cell movements and reorganization, cell signalling and growth. It is essential that the timing of events in all of these different processes is coordinated to generate well-patterned tissues and organs. However, how the timing of intrinsic cell state changes is coordinated with events occurring at the multi-tissue and whole-organism level is unknown. Here, we argue that an important mechanism that accounts for the integration of timing across levels of organization is provided by tissue tectonics, i.e. how morphogenetic events driving tissue shape changes result in the relative displacement of signalling and responding tissues and coordinate developmental timing across scales. In doing so, tissue tectonics provides a mechanism by which the cell specification events intrinsic to cells can be modulated by the temporal exposure to extracellular signals. This exposure is in turn regulated by higher-order properties of the embryo, such as their physical properties, rates of growth and the combination of dynamic cell behaviours, impacting tissue morphogenesis. Tissue tectonics creates a downward flow of information from higher to lower levels of biological organization, providing an instance of downward causation in development.

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.

Commercial equine production in New Zealand. 1. Reproduction and breeding

The Thoroughbred and Standardbred studbooks are the largest in New Zealand, where the production of horses is pasture based. Each racing studbook is closed, and both have well structured systems in place for recording breeding data. There are significant pressures on the Thoroughbred and Standardbred breeding industries with declining broodmare numbers, and increasingly large book sizes for popular stallions. The breeding season for Thoroughbreds is very short, with disparity between the official breeding season and the physiologic breeding season for mares. These issues are confounded by variable gestation lengths of mares, making it difficult for mares to maintain yearly foaling patterns. However, the reproductive efficiency of Thoroughbred mares is improving, mainly due to veterinary and stud management practices such as those to ensure that dry mares are cycling at the start of the breeding season, foaling mares are bred on foal heat, and that mares are kept in good body condition at breeding. There is also a bias towards breeding younger mares with high fertility in preference to older mares, unless they have desired genetics or successful offspring. Careful management of popular Thoroughbred stallions ensures that large books of mares can be covered by natural service. In contrast, Standardbred stallions are collected every-other-day using an artificial vagina, allowing the breeding of mares at distant locations by artificial insemination, using chilled or frozen semen. Breeding horses kept at pasture under New Zealand conditions requires excellent stud management and veterinary management to achieve good outcomes.

Animal responses to environmental variation: physiological mechanisms in ecological models of performance in deer (Cervidae)

Context Proper assessment of the consequences of environmental variation on animals depends on our ability to predict how they will perform under different circumstances. This requires two kinds of information. We need to know which environmental factors influence animal performance and their mode of action, i.e. whether a given factor acts alone or through interaction with other factors, directly or indirectly, instantaneously or after a delay and so on. This essentially correlative process falls within the domain of ecology. We also need to know what determines the direction, amplitude and limits of animal responses to environmental variation and change. This essentially experimental process falls within the domain of physiology. Physiological mechanisms are frequently poorly integrated within the correlative framework of ecological models. This is evident where programmed responses are attributed to environmental forcing and where the effect of environmental factors is evaluated without reference to the physiological state and regulatory capacity of the animal on which they act. Aims Here we examine ways in which the impacts of external (environmental) stimuli and constraints on performance are moderated by the animals (deer) on which they impinge. Key results The analysis shows (1) how trade-offs in foraging behaviour, illustrated by the timing of activity under the threat of predation, are modulated by integration of short-term metabolic feedback and animal emotions that influence the motivation to feed, (2) how the influence of thermal and nutritional challenges on performance, illustrated by the effect of weather conditions during gestation on the body mass of reindeer (Rangifer tarandus) calves at weaning, depends on the metabolic state of the female at the time the challenge occurs and (3) how annual cycles of growth, appetite and reproduction in seasonal species of deer are governed by innate circannual timers, such that their responses to seasonal changes in food supply are anticipatory and governed by rheostatic systems that adjust homeostatic set- points, rather than being purely reactive. Conclusions Concepts like ‘maintenance’ and ‘energy balance’, which were originally derived from non-seasonal domestic ruminants, are unable to account for annual cycles in metabolic and nutritional status in seasonal deer. Contrasting seasonal phenotypes (fat and anoestrous in summer, lean and oestrous in winter) represent adaptive solutions to the predictable challenges presented by contrasting seasonal environments, not failure of homeostasis in one season and its success in another. Implications The analysis and interpretation of responses to environment in terms of interaction between the external stimuli and the internal systems that govern them offer a more comprehensive, multifaceted understanding of the influence of environmental variation on performance in deer and open lines of ecological enquiry defined by non-intuitive aspects of animal function.

Investigation of Toxoplasma gondii and association with early pregnancy and abortion rates in New Zealand farmed red deer (Cervus elaphus)

This study tested for association between Toxoplasma gondii and pregnancy and abortion to investigate sub-optimal reproduction in farmed red deer (Cervus elaphus). Sera from a sub-sample (n = 2304) of pregnant and non-pregnant hinds in early gestation at first pregnancy scan (scan 1) and approximately at the end of second trimester at second pregnancy scan (scan 2) were tested for T. gondii antibodies using a validated ELISA. Foetuses and/or uteri from pregnant, non-pregnant, and aborting hinds at scan 1, scan 2, or weaning were tested for T. gondii DNA by nested PCR. At scan 1, 31.1% of 861 rising two-year-old (R2) and 28.3% of 357 mixed-aged (MA, ≥ 2 years) hinds were sero-positive. There was no association between scan 1 serology and non-pregnancy at animal (R2, p = 0.05 and MA, p = 0.43) or herd level (R2, p = 0.37). Toxoplasma gondii DNA was detected in 3/18 placenta and 4/18 foetal brains from aborting R2 hinds and 15/157 R2 and 3/21 MA uteri from non-pregnant hinds at scan 1. At scan 2, sero-prevalence was higher (odds ratio = 1.6, 95% CI = 1.04-2.48) in aborted (34.3% of 268) than in non-aborted (23.5% of 446) R2 hinds (p = 0.03) and 7.9% of abortions between scans were attributable to T. gondii exposure. Within-herd sero-prevalence at scan 2 was positively associated with daily abortion rate in R2 herds with aborted hinds (p < 0.001) but not in MA herds (p = 0.07). Toxoplasma gondii DNA was detected in 27/169 uteri, 2/20 cotyledons, and 1/5 foetal brains from aborted hinds at scan 2 and in uteri from 5/33 hinds not rearing a calf to weaning. Toxoplasma gondii RFLP genotyping of five loci revealed a unique type I/III genotype pattern, TgRDNZ1, in a foetal brain sample, not been previously reported in deer. These findings provide serological and molecular evidence that T. gondii infection is associated with abortion in red deer, possibly in all three trimesters.

Different maternal investment strategies for male and female calves in a polygynous mammal

Maternal effects occur when the phenotype of the mother influences that of the young to the detriment of her survival, growth or fitness. The investment of the mother can be affected by maternal body condition and/or experience. Trivers-Willard Hypothesis (TWH) and Local Resource Competition Hypothesis (LRCH) are the main hypotheses used to explain bias in birth sex-ratios in mammals, as well as for sex-biased maternal investment. Both hypotheses suggest that a different amount of investment must be expected according to the sex of the young. However, recent studies suggest that these differences are not in quantity but in the strategies: mechanisms and objectives may differ for each sex. We studied how maternal characteristics (age, body mass, body condition, and dominance status) influence relevant aspects of the birth and early growth of the calf (birth date, birth body mass, body mass at weaning, and body condition at weaning) separately for each sex; and how that investment is mediated by milk production and composition (lactose, fat, and protein). One hundred eighty-eight newborns from 75 captive red deer hinds aged from 2 to 19 years were analyzed. The main differential investment observed was related to birth date: when producing a female, hinds give birth earlier in the season only if they have a good body condition; however, when gestating a male it is the older hinds those which deliver earlier. Subsequently, milk production and composition are correlated with birth body mass in female calves, but to weaning body mass in males. Thus, only hind body mass affects the weaning body mass of female calves, compared with age and hind body mass in males. These results suggest that while TWH fits the maternal investment strategy found for male calves, it is LRCH which correlates with the maternal investment patterns observed for females.

Incubation behavior adjustments, driven by ambient temperature variation, improve synchrony between hatch dates and caterpillar peak in a wild bird population

For organisms living in seasonal environments, synchronizing the peak energetic demands of reproduction with peak food availability is a key challenge. Understanding the extent to which animals can adjust behavior to optimize reproductive timing, and the cues they use to do this, is essential for predicting how they will respond to future climate change. In birds, the timing of peak energetic demand is largely determined by the timing of clutch initiation; however, considerable alterations can still occur once egg laying has begun. Here, we use a wild population of great tits (Parus major) to quantify individual variation in different aspects of incubation behavior (onset, duration, and daily intensity) and conduct a comprehensive assessment of the causes and consequences of this variation. Using a 54‐year dataset, we demonstrate that timing of hatching relative to peak prey abundance (synchrony) is a better predictor of reproductive success than clutch initiation or clutch completion timing, suggesting adjustments to reproductive timing via incubation are adaptive in this species. Using detailed in‐nest temperature recordings, we found that postlaying, birds improved their synchrony with the food peak primarily by varying the onset of incubation, with duration changes playing a lesser role. We then used a sliding time window approach to explore which spring temperature cues best predict variance in each aspect of incubation behavior. Variation in the onset of incubation correlated with mean temperatures just prior to laying; however, incubation duration could not be explained by any of our temperature variables. Daily incubation intensity varied in response to daily maximum temperatures throughout incubation, suggesting female great tits respond to temperature cues even in late stages of incubation. Our results suggest that multiple aspects of the breeding cycle influence the final timing of peak energetic demand. Such adjustments could compensate, in part, for poor initial timing, which has significant fitness impacts.

Examining the impacts of red deer hind body condition score and pasture forage mass on calf weaning weight

The effect of pre-calving hind body condition and the interaction with pasture forage mass during lactation on calf growth and intake to weaning were investigated. Two-hundred and forty red deer hinds (Cervus elaphus scoticus × hippelaphus) of average body condition score (BCS) 3.5 were subjected to either ad libitum or restricted feeding for the 4 weeks before the expected start of calving (31 October) to create hinds of low (2.5) or high (3.5) BCS. The hinds were then grazed continuously on pasture of either low (<1200 kg DM/ha) or high (>2400 kg DM/ha) forage mass during lactation (29 October–25 March). In a 2 × 2 crossover design liveweight, liveweight gain and pasture intake were measured in both hinds and calves. Low hind body condition score (BCS 2.5) at the onset of lactation resulted in low calf weaning weight (46.9 kg) when forage mass was low, but not when forage mass was high (57.3 kg). High BCS (3.5) in hinds resulted in intermediate calf weaning weight when on low forage mass (51.2 kg) and high calf weaning weight when forage mass was high (56.6 kg). Both BCS and forage mass influenced calculated total milk production.

Onset of autumn shapes the timing of birth in Pyrenean chamois more than onset of spring

In seasonal environments, birth dates are a central component for a species' life history, with potential long-term fitness consequences. Yet our understanding of selective pressures of environmental changes on birth dates is limited in wild mammals due to the difficulty of data collection. In a context of rapid climate change, the question of a possible mismatch between plant phenology and birth phenology also remains unanswered for most species. We assessed whether and how the timing of birth in a mountain mammal (isard, also named Pyrenean chamois, Rupicapra pyrenaica pyrenaica) tracked changes in plant growing season, accounting for maternal traits, individual heterogeneity and population density. We not only focused on spring conditions but also assessed to what extent onset of autumn can be a driver of phenological biological events and compared the magnitude of the response to the magnitude of the environmental changes. We relied on a 22-year study based on intensively monitored marked individuals of known age. Births were highly synchronized (80% of kids born within 25 days) and highly repeatable (84%; between-female variation of 9.6 days, within-female variation of 4.2 days). Individual phenotypic plasticity allows females to respond rapidly to interannual changes in plant phenology but did not prevent the existence of a mismatch: a 10-day advance in the autumn or spring plant phenology led to 3.9 and 1.3 days advance in birth dates, respectively. Our findings suggest that plant phenology may act as a cue to induce important stages of the reproductive cycle (e.g. conception and gestation length), subsequently affecting parturition dates, and stressed the importance of focusing on long-term changes during spring for which females may show much lower adaptive potential than during autumn. These results also question the extent to which individual plasticity along with high heterogeneity among individuals will allow species to cope with demographic consequences of climate changes.

Analysis of Annual Changes in the Concentrations of Selected Macro- and Microelements, Thyroxine, and Testosterone in the Serum of Red Deer (Cervus elaphus) Stags

The aim of the study was to analyze seasonal changes in the concentrations of calcium, phosphorus, magnesium, and selenium as well as thyroxine and testosterone in adult red deer stags. The highest testosterone concentrations (mean 6.29±4.36 ng/ml) were observed from the end of August to November, confirming an increase in testicular secretory activity during the mating season. The changes in thyroxine concentration show circannual rhythms, most likely related to changes in the air temperature. The highest mean level of thyroxine was observed in spring (55.69±10.99 ng/ml). The concentration of selenium also reached the highest level during this season (0.107±0.027 μg/ml). In the case of the studied macroelements, the concentrations were stable from spring to summer but then decreased to the lowest mean values in autumn in both years of the experiment (Ca, 61.17±10.60; P, 47.08±9.59; Mg, 15.96±2.39 μg/ml). The dynamics of thyroxine secretion does not seem to affect directly the metabolism of calcium, phosphorus, and magnesium. In turn, sexual activity, manifested in the increase in secretion of testosterone, may affect changes in the concentration of calcium. Additionally, we cannot exclude a connection between changes in the concentrations of testosterone and selenium.

Effect of conception date and hind nutrition on fetal growth trajectory and gestation length of red deer (Cervus elaphus)

This study tested the hypothesis that the negative association between gestation length and conception date in red deer is mediated by nutrition. Twenty-eight pregnant red deer were randomly allocated to four groups according to a 2 × 2 factorial design, with the factors conception date (14 March, E; 28 April, L) and level of nutrition (ad libitum, H; restricted, R). Animals were housed indoors in individual pens from early winter until calving and offered daily an ad libitum pelleted ration. The daily ration was then restricted from late winter in ER (134 days post-conception) and LR (89 days post-conception) groups, so that these hinds did not experience a seasonal increase in food intake. X-Ray computed tomography scans were taken at Days 120, 150, 180 and 210 of gestation (mid–late gestation) to estimate weight of various conceptus components. Growth rate of the total fetus was significantly higher in LH than in other treatments (P < 0.01) between Days 180 and 210 of gestation. Birthweight was not significantly different (P > 0.05) between treatments or calf sex. Birthweight was associated directly with change in hind liveweight (P = 0.03) and body condition score during the third trimester of pregnancy (P = 0.01), but was not significantly associated with gestation length (P = 0.34). Gestation length was 4.4 days longer in LR than LH hinds (P = 0.03) and was negatively associated with both food intake (P = 0.03) and LW gain (P = 0.02) during the final trimester of gestation. Feeding late-conceiving hinds an ad libitum diet of high-quality food during the third trimester of gestation maximises fetal growth and shortens gestation length.

Genetics of early conception and its relationship to growth traits in red deer (Cervus elaphus)

The genetics of early conception success and live-animal growth were studied in five herds of red deer in New Zealand. Conception date (CD) was used as the criterion of success in seasonally mated hinds, with 2493 mating records available. Liveweights analysed were weaning weight, yearling weight, 15-month weight and mature weight (hinds only). CD and liveweights were analysed using restricted maximum likelihood procedures with an animal model, including all available pedigree records. Under the management conditions applied, CD had a phenotypic standard deviation of 7.9 days, a repeatability across years of 0.29 ± 0.03 and a direct (univariate) heritability of 0.20 ± 0.06. Regression procedures using DNA markers to adjust the data for genetic differences resulting from an animal’s ancestral region of origin (mainly western vs eastern European) had little effect on the parameter estimates above. Direct heritability estimates for the four weight traits were 0.38 ± 0.03, 0.49 ± 0.02, 0.48 ± 0.04 and 0.46 ± 0.04, respectively, while the genetic correlations between CD and these traits (e.g. using 1763 paired records of CD with yearling weight) were –0.24 ± 0.11, –0.24 ± 0.09, –0.16 ± 0.10 and –0.04 ± 0.09, respectively. Selection for earlier CD would be successful and compatible with selection for higher juvenile weights.

Gestation length and occurrence of daytime foaling of Standardbred mares on two stud farms in New Zealand

AIMS

To examine the gestation lengths and occurrence of daytime foaling of Standardbred mares foaling outdoors at stud farms in Southland, New Zealand (latitude 45˚S).

METHODS

Data were collected prospectively at two commercial Standardbred stud farms (Farms A and B), during the 2008/9 and 2009/10 breeding seasons (October to February). For each foaling, the identity of the mare, date and time of foaling, gender of foal, time the mare passed the fetal membranes, time the foal stood, and foaling problems including dystocias, were recorded. The effect of farm, season, gender of foal, month of artificial insemination (AI) or foaling, age and parity of mare on gestation length, percentage of mares foaling during daylight hours, and percentage of foalings recorded as dystocia, were examined.

RESULTS

A total of 614 foaling records were obtained from 507 mares. For 594 foalings with complete records, mean gestation length was 349 (SE 0.5) days. Mean gestation length was shorter for fillies (347.8 (SE 0.6) days) than colts (350.3 (SE 0.6) days) p = 0.021) and decreased with month of AI, from October to February (p = 0.001). The time of foaling was bimodally distributed with the primary peak around 0200 hours and a secondary smaller peak around 1300 hours. The percentage of mares foaling in daylight was lower on Farm A (69/285 (24%)) than Farm B (128/313 (41%)) (p = 0.001). Colt foals were less likely to be born during the day than fillies (OR = 0.63; (95% CI = 0.44-0.88); p = 0.008), but there was no effect of age or parity of mare or month of foaling (p>0.05).

CONCLUSIONS AND CLINICAL RELEVANCE

Mean gestation length of mares in this study was longer than that previously reported from other countries. Longer gestation length decreases the time available for these mares to get back into foal in the same season. It is important that managers take this into account and ensure optimum conditions for conception; breeding at the first postpartum oestrus may be essential. There were more mares foaling in daylight hours on one stud than has previously been reported. Under these conditions mares should be monitored for foaling during daytime as well as at night.

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.

Causes of mortality and diseases in farmed deer in Switzerland

To investigate diseases and causes of mortality in Swiss farmed deer, deer found dead or shot due to diseased condition between March 2003 and December 2004 were requested for a complete postmortem examination. One hundred and sixty-two animals were submitted. Perinatal mortality, necrobacillosis in 3 week to 6 month old deer, and endoparasitosis in 6 month to 2 year old deer were identified as the most important causes of loss, followed by ruminal acidosis, which was diagnosed in 22% of deer older than 1 year. Congenital malformations were observed in 15% of deer less than 6 months old. Reportable infectious diseases known as major problems in deer farming in other countries were rare (yersiniosis, malignant catarrhal fever) or not observed (tuberculosis, chronic wasting disease). Overall, the results indicate that the Swiss deer population does not present major health problems of concern for domestic animals.

Dystocia in Formosan sambar deer (Cervus unicolor swinhoei) in semi-domesticated herds

Over a nine-year period (2000 to 2008), 22 instances of dystocia and 50 normal fawnings in Formosan sambar deer (Cervus unicolor swinhoei) hinds from semi-domesticated herds were investigated. The majority of the hinds (17, 77.3 per cent) that suffered dystocia were categorised as having a body condition score (BCS) in the medium range (between 2.5 and 3.5 inclusive), indicating that there was no significant relationship between obesity (BCS >3.5) in hinds and the occurrence of dystocia. In addition, maternal body condition had no effect on the birthweight of the offspring. Among the 22 instances of dystocia, 16 of the fawns (72.7 per cent) did not survive; one of these deaths was anteparturient and the other 15 were parturient. Eighteen (81.8 per cent) of the cases of dystocia involved male fawns, and 15 (93.8 per cent) of the deaths were of male fawns (P=0.044). Nine (40.9 per cent) of the instances of dystocia resulted from maternal excitement, mainly attributable to disturbances caused by human beings. In 12 of the cases that resulted in the death of the fawn, the request for veterinary assistance had been delayed at least one day. There were six cases in which the fawns survived; these were the ones that had received assistance within six hours after the onset of parturition.

Development of body condition in hinds of Iberian red deer during gestation and its effects on calf birth weight and milk production

Reproductive effort affects body reserves and subsequent ability to reproduce. In fact, the energy costs of gestation and lactation in hinds of red deer have a marked effect on maternal condition. The objectives of this study were to examine the development of hind monthly body condition during gestation in relation to reproductive rest, age and age class, just as its effects on total milk yield and calf birth weight. Eighty hinds of Iberian red deer were used as subjects during 2 years of study. They had ad libitum access to food and water. Animals were weighed weekly, and body condition was individually assessed. Milking was carried out under anesthesia with a milking machine followed by hand milking to collect the remaining milk. Age and reproductive rest influenced body condition, improving with age (coefficient: 0.10+/-0.01; P<0.001) and reproductive rest (mean+/-SEM, 3.75+/-0.05 vs. 3.25+/-0.02, with and without rest respectively; P<0.001). Hind age correlated positively with her body condition (R=0.62, P<0.001), however, when age class was included in the model, age was not significant. The greater the age class (up to age class 4) the greater the body condition; however, hinds of age class 5 had a lower body condition, but no significant differences were observed. Development of the body condition during gestation was different to age class 1 with respect to the others, just as between hinds that rested the preceding year and those that did not.

The effect of conception date on gestation length of red deer (Cervus elaphus)

Recent studies have demonstrated that gestation length of red deer (Cervus elaphus) is highly variable and influenced by various environmental factors, and this may confer survival advantages for neonates. The current study investigated the relationship between conception date and gestation length to test the hypothesis that within-herd synchrony of red deer births is facilitated by a 'push/pull' control over gestation length, such that hinds conceiving early and late in the breeding season have longer and shorter gestation periods, respectively. In Study 1, data on conception and calving dates were obtained for 393 naturally cycling hinds across two herds. In Study 2, conception and calving dates were obtained from 91 hinds in which oestrus/conception were artificially synchronised across a 4-week range of dates spanning the natural rut. Gestation length for each population was analysed by linear regression, fitting conception day followed by terms for the fixed effect which included hind age (pubertal vs. adult), hind genotype (Cervus elaphus scoticus vs. Cervus elaphus hippelaphus and their crossbreds), calf sex, sire genotype (Study 1 only), birth weight and year. In Study 1, both populations of naturally cycling hinds exhibited highly significant (P<0.001) negative slopes (-0.36, -0.49) for the regression of gestation length against conception date, with indications of a significant hind genotype effect favouring shorter overall gestation lengths for crossbred hinds. Other effects for hind age, calf sex, birth weight, sire genotype and year were not significant. In Study 2, in which conception dates were artificially induced, there was a highly significant negative slope (-0.19), with a notable but non-significant effect of hind age favouring shorter overall gestation length for primiparous (pubertal) hinds (P>0.05). Other effects for hind live weight, calf sex and calf birth weight were not significant. All data sets support the hypothesis, and indicate that for every 10 days difference in conception date there was a change in gestation length of 1.9-4.9 days. This hints at the adaptive importance of optimisation of birth date in wild populations of red deer but the precise physiological mechanisms remain to be resolved. It is postulated that variation in fetal age during the latter stages of pregnancy, when feed quality and voluntary feed intake cycles are in a state of flux, may drive differential growth trajectories for early and late conceived fetuses, leading to nutritional control over fetal maturation and induction of parturition. However, consideration is also given to a putative direct effect of prevailing photoperiod on control of parturition processes in red deer.

Influence of level of nutrition during late pregnancy on reproductive productivity of red deer (2) Adult hinds gestating wapitixred deer crossbred calves

The present study aimed to relate feed intake of red deer hinds in the later stages of gestating wapitixred deer crossbred foetuses on dam body condition, gestation length, birth weight and calf growth. Multiparous hinds (N=18) conceiving at known dates to either wapiti (n=12) or red deer (n=6) sires were housed in individual pens from days 150-220 of pregnancy, during which time they were offered either ad libitum access to pelletised rations (n=6 crossbred-bearing hinds [HH] and n=6 red deer-bearing hinds [RH]) or a restricted offer (n=6 crossbred-bearing hinds [HL]) set at 70% of the average ad libitum intake of HH hind in the previous week. Hinds were returned to pasture at day 220 and calving was closely monitored. Liveweights, body condition score (BCS), and lactation score (LS) of hinds were recorded weekly from day 130 of pregnancy until calves were weaned at 12 weeks of age. Calves were tagged and weighed at birth, and subsequently weighed at 7 and 12 weeks of age. HH and RH hinds exhibited similar patterns and levels of MEI/kg0.75, which peaked at 7.8 MJME/kg0.75 at day 220. HL hinds peaked at approximately 5 MJME/kg0.75 and showed significantly lower rates of liveweight gain during pregnancy. Interestingly, both crossbred-bearing groups initiated mammary development in advance of the RH hinds. While there were significant effects of foetal genotype on mean gestation length (239 days versus 234 days for crossbred versus red deer) and mean birth weight (14.5 kg versus 10 kg), the nutritional contrast for gestation length of crossbred-bearing hinds (i.e. HH versus HL) was not significant but approached significance for birth weight (14.5 kg versus 11.9 kg; P=0.06). Regression analysis revealed weak relationships between changes in hind liveweight and gestation length (P>0.05) but a significant relationship with birth weight (P<0.05). However, change in hind BCS was significantly related to both gestation length and birth weight. Crossbred calves reared by HH hinds were 30% heavier at 7 and 12 weeks of age than the red deer calves. However, those reared by HL hinds were significantly lighter than their genotype contemporaries and only marginally heavier than the red deer calves. These results generally contrast with the previous studies on red deer hinds gestating red deer foetuses [Asher, G.W., Mulley, R.C., O'Neill, K.T., Scott, I.C., Jopson, N.B., Littlejohn, R. 2004. Influence of level of nutrition during late pregnancy on reproductive productivity of red deer, (1) Adult and primiparous hinds gestating red deer calves. Anim. Reprod. Sci., in press] and indicate that the genetically determined higher growth requirements of crossbred foetuses may override any mechanism of compensatory control of gestation length at the expense of calf birth weight. Furthermore, there were marked carryover effects of late gestational feeding on crossbred calf growth and their dam's BCS that highlight the high nutritional demands of lactation.