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.     

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

The present study aimed to relate feed intake of red deer hinds during late pregnancy to dam body condition, foetal development and calf growth. Across 3 years, multiparous (n=33) or primiparous (n=18) hinds with known conception dates were housed in individual pens from days 150-220 of pregnancy, during which time they were each offered one of three daily allowances of pelletised rations (11 MJME/kg DM; 16% CP): high (H; ad libitum), medium (M; approximately 30% less; multiparous hinds only) and low (L; approximately 50% less). Restricted intake levels were retrospectively calculated from the mean intake of H hinds 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. Additionally, hinds in the first year of study underwent CT scans on days 150 and 215 of pregnancy to assess compositional changes of the dam and conceptus. Mean daily ad libitum intakes of H hinds increased from 1.8 to 2.0 kg DM (0.6-0.7 MJME/kg0.75) at around day 150 to 2.8-3.2 kg DM (0.8-0.9 MJME/kg0.75) by day 220. Those of M and L hinds peaked at 1.8 and 1.6 kg DM, respectively, by day 220. This was reflected in significant treatment effects on liveweight gain and change in BCS and LS by the time of calving. CT scans indicated a significant treatment effect by day 215 on the mass of hind tissues (fat and lean) and a non-significant trend on conceptus/foetal weights. Despite apparent differences in foetal growth trajectories, there were no discernable treatment effects on sex-adjusted birth weights. However, there was an unexpectedly wide spread in calving dates that reflected considerable variation in gestation length. Furthermore, gestation length was negatively correlated with change in hind liveweight (but not BCS) between days 150 and 220 of pregnancy for all groups of hinds (P<0.05). Of three neonatal calf mortalities, none were related to overweight (dystocia) or underweight (non-viability) calves. Subsequent growth rates (g/day) of surviving calves did not reflect prior treatment of their dams, although variation in birth date influenced weights on specific dates. It is concluded from this study that while variation in nutrition to hinds during the last trimester may strongly influence foetal development, under conditions of modest feed imbalance, variation in gestation length compensates to ensure optimisation of birth weight.     

Birth spacing in langur monkeys (Presbytis entellus)

This paper presents 10 years of reproductive data on birth interval length and 5 years of data on reproductive behavior postpartum from a captive colony of gray langur monkeys (Presbytis entellus)housed in Berkeley, California. Birth intervals of females following different pregnancy and nursing schedules are compared. Females whose infants survive to the age of 9 months have a median birth interval of 15.4 months. The experimental separation of mothers from infants for a period of 2 weeks, 6 to 9 months postpartum, had no significant effect on the median birth interval length. Females experiencing a pregnancy failure or the loss of a neonate had median birth intervals of 9.6 and 10.7 months, respectively. These intervals were significantly shorter than the birth intervals of females whose infants survived to 9 months, showing that the presence of a nursing infant delays the female’s time to next conception by approximately 5 to 6 months. Females experienced a median of three estrous periods (two estrous cycles) before conceiving postpartum, regardless of pregnancy outcome or length of infant survival, and females rarely conceived during their first estrous period postpartum. Weaning did not occur until after the mother’s next conception. These data indicate that, in populations of langurs characterized by average birth intervals of 15 to 16 months, the loss of an infant after the age of 5 to 6 months will not accelerate a female’s ability to conceive or shorten the birth interval length. The available data on birth spacing from populations of free-ranging langurs are reviewed. It could not be demonstrated that non-Himalayan populations are characterized by birth intervals which are as long as 20 to 24 months. Rather, it is suggested that female langurs inhabiting seasonally arid sites, such as Jodhpur, Abu, and Dharwar, may be capable of producing infants on the average of every 15 to 16 months. Flexibility in the timing of births and the lack of well-defined birth seasons at these sites may be explained by this species’ dietary and digestive adaptations. Additionally, data on birth spacing and the age of missing infants from the above field sites, where it has been suggested that infanticide following changes in male leadership occurs habitually, do not lend support to the sexual selection hypothesis of infanticide as proposed by S. Hrdy (1974, 1977).     

Conception dates in relation to age and condition in two populations of Red deer in Scotland

The conception dates of wild Red deer ( Cervus elaphus L .) in two parts of Northern Scotland (the Isle of Rhum in the Inner Hebrides, and Glen Feshie in the Central Highlands) were estimated from foetus weights and from the known birth dates of calves. In both localities, the conceptions were spread over periods of about 100 days from late September to late December with a peak in October. The median conception date was seven to ten days earlier on Rhum than at Glen Feshie.
The conception data from shot hinds showed distinct patterns in relation to age, whether or not the hinds had current year's calves, and to body condition. Body condition may be the most important "secondary factor" influencing the time of conception; hinds in poor condition tended to conceive later than those in good condition. Body condition could also account for year to year fluctuations in the time of breeding; hinds tended to breed earlier in years when they were in better condition.     

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.     

A comparison of the calving behaviour of farmed adult and yearling red deer (Cervus elaphus) hinds

Mortality of newborn red deer (Cervus elaphus) calves is a major concern on New Zealand farms, as perinatal losses average approximately 10% of calves born. Primiparous red deer (calving as yearlings) lose more calves than multiparous hinds (adults). We performed a study on yearling and adult red deer hinds in order to improve knowledge of their calving behaviour and determine any apparent reasons for calf mortality. Pacing along fence lines was observed frequently during the 24 h period before birth (individuals were pacing in 43% of observations during this period). Adult hinds had a significantly earlier onset and longer duration of pacing (P<0.05). Hinds were often observed isolated (>20 m) from the rest of the herd during the 2 days prior to parturition, and this behaviour was also observed earlier in the adults than in the yearlings (P<0.05). Forty-four percent of adult hinds and 60% of yearlings experienced some form of interference from other hinds during parturition. Among hinds that were interfered with, yearlings had a higher average number of interferences from other hinds during parturition than adults (P<0.05). Calves born to yearling hinds took significantly longer to suckle for the first time (mean=44 min) from their dams than calves born to adult hinds (33 min; P<0.05). We concluded that an inability of hinds to express natural isolation behaviour was likely to contribute to calf mortality due to increased anxiety (indicated by fence line pacing) and encroachment on the birth areas of others, and that calves of yearlings were at an increased risk of mortality due to the higher number of interferences taking place during parturition and the longer time interval between birth and suckling.     

Serum progesterone changes in luteal cyclicity and duration of estrous cycle in Formosan sika deer (Cervus nippon taiouanus) hinds

A study was conducted to investigate the serum progesterone (SP(4)) profiles and duration of estrous cycles in the farmed Formosan sika deer (FSD; Cervus nippon taiouanus) during the major breeding season. Five parous, open and non-milking hinds were allotted to collect peripheral blood samples twice weekly for P(4) measurement by radioimmunoassay beginning at the initiation of the rutting season indicated by rutting behaviors of the sexually mature stags. The hinds were polyestrous as proved by cyclic changes of SP4 levels. After the presumptive estrus shown by the lowest concentration of SP(4) (0.20+/-0.01 ng/ml), this ovarian hormone markedly elevated on day 7 of the cycle (1.67+/-0.11 ng/ml), reached plateau (3.15+/-0.16 ng/ml, P<0.01) during days 11 to 18, and then declined to the basal levels in the subsequent estrus. It is concluded that mean duration of the estrous cycle in FSD during the major rutting season is 19.3 days with a range of 17 to 21 days, and that the patterns of circulating progesterone profiles during the estrous cycles of the FSD are similar to those of other deer species so far investigated.     

Compensatory extension of gestation length with advance of conception in red deer (Cervus elaphus)

Calving date in many mammals is matched to the time of greatest food availability. Out of season calving results in heavy penalties in terms of own and offspring survival or body condition. This study examined whether gestation length is affected by advancing fertilisation. Thirty-six red deer hinds (of the Iberian and Scottish subspecies) were subjected to a synchronisation treatment of oestrus, ovulation, and artificial insemination on three dates, with remaining non-pregnant females mated with an intact male in a last group. Gestation was longer the more the fertilisation was advanced; gestation lasted 241.5+/-1.3 days (d) in the first group, 237.4+/-1.2 d in the second, 235.1+/-1.3 d in the third, and 231.2+/-1.6 d in the last. Mean gestation lasted 234.2+/-0.7 d. Hinds gained less weight during gestation the more the fertilisation was advanced. The difference was due at least in part to net body weight of the hind after calving compared to that at mating, and calves did not differ in birth weight. As early born calves suffer greater mortality in the field, this enlargening of gestation might be a compensatory response of the hinds to match calving with food availability. Under natural conditions, similar small modifications of gestation length may help hinds to overcome short-term adverse conditions for calving. Because calf mortality is correlated with birth weight, hinds may have kept calf birth weight constant at the expense of greater body weight loss.     

Reproductive parameters of clouded leopards (Neofelis nebulosa)

Reproductive data compiled from the International Clouded Leopard Studbook revealed that 75% of all litters were born to females between one and five years of age. Sixty-three percent of the males had sired litters by four years of age with reproduction declining after six years of age. Sixteen zoological institutions surveyed worldwide contributed estrous cycle data from 28 clouded leopards. Sexual maturity (age at first estrus) for these females ranged from 17 to 28 months of age with a mean estrous cycle length of 29.9 ± 13.8 days. The mean length of estrus was six days. Gestation length ranged from 85 to 121 days (X? = 93.4 ± 6.3). There was a significantly higher incidence of estrus in fall and winter compared with spring and summer over latitudes ranging from 36°–45° and 51°–55° (P < .005). Mating occurred in all months except June and October, and cubs were produced in all months except December. The highest frequency of mating occurred during the month of December corresponding with a birth peak in March.     

Monitoring ovarian cycles and pregnancy in brown brocket deer (Mazama gouazoubira) by measurement of fecal progesterone metabolites

In the present study, pregnancy and the estrous cycle were monitored in captive brown brocket deer (Mazama gouazoubira) by measuring fecal progestagens with a commercial enzyme immunoassay (EIA), along with behavioral data. Fecal samples were collected twice a week during pregnancy and daily during the estrous cycle and post-partum period. It was possible to distinguish between inter-luteal and luteal phases of the estrous cycle. Behavioral estrus corresponded with low concentrations of fecal progestagens. Samples from two consecutive cycles were available from five hinds, and the mean estrous cycle (n=10) was 26.9+/-1.7 d (mean+/-S.E.M.). However, when two extreme cycles (34 and 37 d) were deleted, the mean estrous cycle was 24.7+/-1.2 d. Three animals became pregnant (gestation ranged from 208 to 215 d). After fertile breeding, progestagen concentration in these hinds remained among luteal phase concentrations throughout pregnancy, with the exception of a few peaks. Within 4 d post-partum, two hinds reached interluteal phase values, while one hind maintained luteal concentrations for at least 1 week.     

Fixed-time artificial insemination in red deer (Cervus elaphus) in Argentina

Synchronization of estrous and fixed-time artificial insemination (FTAI) was conducted during the reproductive season of 2008 (March–April) in a local red deer breeding farm in Argentina. Multiparous suckling hinds (n = 38) were artificially inseminated following hormonal treatment (intravaginal sponge containing 100 mg of medroxiprogesterone acetate). At the time of sponge removal (day 12) 250 IU of eCG and 500 μg of PGF2α were given to each hind. The FTAI was performed at 48–55 h after device removal with cryopreserved semen imported from New Zealand. Rectal-transcervical AI method (similar to that in cattle) was performed and semen was deposited within the uterine body (n = 28) or the cervix (n = 10). Pregnancy was diagnosed by means of ultrasonography 44 days after FTAI. The overall pregnancy rate was 36.8% (14/38). Percentage of does that became pregnant with intrauterine seminal deposition was 42.9% (12/28) whereas pregnancy rate in the hinds with intracervical AI was 20% (2/10; P = 0.27).     

Reproduction in the slender loris (Loris tardigradus malabaricus)

A breeding colony of slender lorises (Loris tardigradus malabaricus) was studied to obtain data for comparison with other prosimian species, to contribute reproductive information for improving management of captive lorises, and to resolve some uncertainties in the literature regarding reproduction in the slender loris. At the Duke University Primate Center, a female slender loris reached sexual maturity at approximately ten months of age and conceived at one year of age. The length of the estrous cycle was 29–40 days, with copulation occurring over two consecutive days during estrus. Gestation length was 166–169 days. Litter size for each six births was one. Conception did not occur during an immediate post-partum estrus, but four months after birth, resulting in a 9 1/2-month interbirth interval. There was no evidence of reproductive seasonality. Lactation lasted between five and seven months. Reproductive rates of slender lorises are among the lowest of primates less than 500 g. Differences in reproductive parameters may exist between different subspecies of slender lorises.     

Effects of density, climate, and supplementary forage on body mass and pregnancy rates of female red deer in Spain

The influence of short- and long-term (cohort) effects of climate and density on the life-histories of ungulates in temperate regions may vary with latitude, habitat, and management practices, but the life-histories of ungulates in the Mediterranean region are less well known. This study examined the short- and long-term effects of rainfall and absolute density on hinds in two of the southernmost populations of red deer (Cervus elaphus hispanicus) in Europe. One population received supplementary forage. Unlike more northerly latitudes, where red deer hinds lose body mass in winter as a result of adverse weather, in the Spanish populations, hinds did not lose body mass. Hinds in the population that received supplementary forage were heavier and more likely to become pregnant than were the hinds in the unsupplemented population. The likelihood of pregnancy occurring was strongly influenced by hind body mass; the proportion of yearlings that became pregnant was consequently lower in the unsupplemented population than in the population that received supplementary forage. Cohort effects on hind body mass (negative for density and positive for rainfall at birth) and on the probability of pregnancy (negative for density at birth) were apparent only in the unsupplemented population, which implies that supplemental feeding may partially compensate for negative density-dependent factors during early growth, and that supplemented deer hinds may experience reduced selection pressures. These results reflect the particular seasonal variation in the abundance and quality of food in Mediterranean habitats. The delayed effects of climate and density at birth on adult hind body mass and the prevalence of pregnancy probably affects population dynamics and constitutes a mechanism by which cohort effects affect the population dynamics in Iberian red deer. The management of Iberian red deer populations should take into account cohort effects and supplemental feeding practices, which can buffer density- and climate-dependent effects and reduce natural selection pressures.     

Plasma concentrations of progesterone in female red deer (Cervus elaphus) during the breeding season, pregnancy and anoestrus

Concentrations of progesterone in peripheral plasma of red deer hinds were basal (less than 1 ng/ml) during lactation/seasonal anoestrus, but increased abruptly at the onset of the breeding season. Lactating hinds (N = 19) started ovarian cycles 10 days later (P less than 0.01) and conceived 16 days later (P less than 0.001) than did 13 weaned hinds. There was no evidence, from plasma progesterone values, of silent oestrus at the start of the season. Progestagen/PMSG treatment induced early ovulations in 8 anoestrous hinds but fertility was low, only 2 conceiving and giving birth. Pregnant hinds (N = 42) had high plasma concentrations of progesterone (mean 3-5 ng/ml) which declined just before parturition.     

Pregnancies following long luteal phases in southern white rhinoceros (Ceratotherium simum simum)

All extant species in the Rhinocerotidae family are experiencing escalating threats in the wild, making self-sustaining captive populations essential genetic reservoirs for species survival. Assisted reproductive technologies (ARTs) will become increasingly important for achieving and maintaining ex situ population sustainability and genetic diversity. Previous reports have shown that a large proportion of captive southern white rhinoceros (SWR) females are irregularly cyclic or acyclic, and that cycling females display two different estrous cycle lengths of approximately 30 or 70 days. It has been suggested that the longer estrous cycle length is infertile or subfertile, as no term pregnancies have been observed following long cycles. Here we report the achievement of two pregnancies following long luteal phases, using ovulation induction and artificial insemination with either fresh or frozen-thawed semen. One female SWR conceived on the first insemination attempt and gave birth to a live offspring. A second female conceived twice in consecutive long cycles although the first embryo was resorbed by 33 days post-insemination. A pregnancy from this female's second insemination is ongoing with expected parturition in November 2019. Whether prolonged estrous cycles in SWR are subfertile or infertile in natural breeding situations remains unclear. However, our findings demonstrate that the application of ARTs following prolonged cycles can result the successful establishment of pregnancies in SWR. Therefore, with ARTs, female SWR otherwise considered nonreproductive due to long estrous cycles may still have the potential for representation and contribution to the ex situ population.     

Oestrous cycles and the breeding season of the Père David's deer hind (Elaphurus davidianus)

Reproductive cycles were studied in a group of tame Père David's deer hinds. The non-pregnant hind is seasonally polyoestrous and, in animals studied over 2 years, the breeding season began in early August (2 August +/- 3.3 days; s.e.m., N = 9) and ended in mid-December (18 December +/- 5.7 days; N = 8) and early January (6 January +/- 3.2 days; N = 11) in consecutive years. During the anoestrous period, plasma progesterone concentrations were low (0.2 +/- 0.01 ng/ml) or non-detectable. There was a small, transient increase in progesterone values before the onset of the first cycle of the breeding season. In daily samples taken during an oestrous cycle in which hinds were mated by a marked vasectomized stag, progesterone concentrations remained low (less than 0.5 ng/ml) for a period of about 6 days around the time of oestrus, showed a significant increase above oestrous levels by Day 4 (Day 0 = day of oestrus) and then continued to increase for 18 +/- 2.8 days to reach mean maximum luteal levels of 3.5 +/- 0.6 ng/ml. The plasma progesterone profiles from a number of animals indicated that marking of the hinds by the vasectomized stag did not occur at each ovulation during the breeding season and therefore an estimate of the cycle length could not be determined by this method. In the following year, detection of oestrus in 5 hinds was based on behavioural observations made in the absence of the stag. A total of 19 oestrous cycles with a mean length of 19.5 +/- 0.6 days was observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

The gestation length of wapiti (Cervus elaphus) revisited

As an ancillary activity to an artificial insemination program in farmed wapiti, the length of gestation of 28 wapiti hinds that delivered single calves of established parentage was calculated. Estrus was synchronized in 47 wapiti using progesterone impregnated devices (controlled internal drug release, CIDR) and an injection of PMSG. All hinds were artificially inseminated between 60 and 63h after CIDR removal. Pregnancy was determined between 45 and 65 days by ultrasound. A verifiable figure for gestation length was obtained based both upon timed-artificial insemination, date of parturition, and confirmation of sire identity through microsatellite DNA technology. The calculated gestational length of 247 +/- 5 days was significantly (P < 0.0001) shorter than the generally quoted figure of 255 +/- 7 days.     

Ovarian follicular and luteal dynamics in wapiti during the estrous cycle

The reproductive tracts of 13 mature hinds were examined daily by transrectal ultrasonography and blood samples were taken daily from October to January to characterize follicular, luteal, and endocrine dynamics in wapiti during the estrous season. Follicle development occurred in waves characterized by regular, synchronous development of a group of follicles in temporal succession to a surge in serum FSH concentration. The mean interovulatory interval was 21.3 +/- 0.1 d, but was shorter in hinds exhibiting two follicular waves than in hinds exhibiting three and four waves (P < 0.05). The interwave interval was similar among waves in two-wave cycles and the first wave of three-wave cycles. All other interwave intervals in three- and four-wave cycles were shorter (P < 0.05). The maximum diameter of the dominant follicle of the first wave was similar among two-, three-, and four-wave cycles. For all other waves in three- and four-wave cycles, the maximum diameter was smaller (P < 0.05). Corpus luteum diameter and plasma progesterone concentrations were similar between two- and three-wave cycles, but the luteal phase was longer (P < 0.05) in four-wave cycles. The dominant follicle emerged at a diameter of 4 mm at 0.4 +/- 0.1 and 0.8 +/- 0.1 d before the largest and second largest subordinate follicles, respectively. The follicle destined to become dominant was larger (P < 0.05) than the largest subordinate follicle one day after emergence, which coincided with the first significant decrease in serum FSH concentration. We concluded that the estrous cycle in wapiti is characterized by two, three, or four waves of follicular development (each preceded by a surge in circulating FSH), that there is a positive relationship between the number of waves and the duration of the cycle, and an inverse relationship between the number of waves and the magnitude of follicular dominance (diameter and duration of the dominant follicle).     

Nonsurgical embryo transfer in the scimitar-horned oryx (Oryx dammah): Birth of a live offspring

The objective of this project was to determine if modifications of methods of estrous synchronization, superovulation, embryo recovery, and transfer used successfully in other ungulates, both domestic and nondomestic, could be applied to scimitar-horned oryx (Oryx dammah). Donors were two parous females and recipients were one parous and two nulliparous females that were given a total of two cloprostenol injections at an interval of 0 and 13 or 12 days, respectively. Donors were treated with follicle-stimulating hormone (FSH-P, Schering, Kenilworth, NJ) b.i.d. for 4 days and placed with a fertile male. Seven days after the last FSH-P injection, nonsurgical uterine lavages were performed on both donors. One good-quality embryo at the morula stage was recovered and nonsurgically transferred into the right uterine horn of the parous recipient. A healthy female calf born at 247 days post-transfer represents the first known live birth of scimitarhorned oryx following embryo transfer. These results provide additional evidence that estrous synchronization and embryo transfer techniques used in other ungulates can be applied to endangered antelopes such as the scimitar-horned oryx.     

Modulation of the estrous cycle by pheromones from pregnant and lactating rats

Female rats were exposed to odors from females that went through a birth cycle of pregnancy, birth and lactation. The estrous cycle was shortened by odors from pregnant rats and lengthened by odors from lactating rats and their pups. Changes in estrous cycle length were accompanied by changes in the length of the luteal phase (metestrus-early diestrus). A log survivor plot demonstrated that variation in cycle length was the result of different rates of ovulation within the population under each condition. Neither pregnancy nor lactation odors affected the intensity or timing of the lordosis reflex. These odors could modulate fertility and coordinate birth cycles within a group of rats.