Interluteal Phase Research Articles

Utilising routine non-invasive faecal samples for the detection of oestrus and early gestation in okapi (Okapi johnstoni)

Zoos play a vital role in conservation with an overall aim of preserving species, such as the okapi (Okapi johnstoni), from extinction. To ensure species survival, sustainable ex-situ populations are required, and therefore understanding the reproductive status of individuals is important for population management. In this study, the oestrous cycles and gestations of four okapi (n = 7 pregnancies) were monitored through non-invasive faecal sampling methods to quantify progestagen and oestrogen metabolites. Baseline criteria for determining oestrous cycles was developed using approximately 20 months of sampling from each of two non-pregnant females, before being applied to pre- and early conception data. Pre-conception oestrous cycles were characterised in two females with luteal phase (mean ± SD) was 8.47 ± 1.41 days (n = 59) with an inter-luteal phase of 7.38 ± 1.67 days (n = 58), and overall average cycle length of 15.83 ± 2.02 days (n = 54 full cycles only). Observed in all four females, oestrogen metabolite peaks occurred at the beginning of the inter-luteal phase as progestagen metabolites were decreasing. Gestation was confirmed when progestagen metabolite concentrations remained at luteal phase concentrations for at least 20 days, with concentrations remaining at this level for the first 120 days of gestation without return to baseline values. A secondary increase at around 150 days lasted until parturition. These data demonstrate that okapi exhibit similar oestrous cycles to other members of the giraffidae family, with faecal oestrogens for the first time indicating that ovulation occurs at the beginning of the inter-luteal phase while progestagens are still elevated. Furthermore, we have shown that through routine sample collection and hormone monitoring, gestation can be confirmed within the first trimester, which can benefit the management of the species in ex-situ populations.

Monitoring estrous cycle in Brazilian dwarf brocket deer (Mazama nana) by fecal progestagen metabolites and behavior

Data on the reproductive physiology of the Brazilian dwarf brocket deer (Mazama nana) is still scarce in many aspects, such as its reproductive cycle and endocrine pattern. Therefore, this study aimed to characterize the estrous cycle (length and fecal progestagen metabolites -FPM- profile) in captive females of M. nana, by non-invasive hormonal monitoring. The study was performed with females (n = 4), housed at two different facilities: 1) in a collective enclosure at the Danilo José Galafassi Municipal Zoo, in Cascavel, Paraná, Brazil, (n = 3). 2) in an individual pen at the Deer Research and Conservation Center (n = 1), from UNESP, Jaboticabal, São Paulo, Brazil. Fecal samples were collected three times a week during two complete estrous cycles, based on behavioral observations. FPM profiles were analyzed by enzyme immunoassay (EIA). The estrous cycle length was defined as the intervals between behavioral estrus observations and fecal hormonal monitoring. The mean duration (± SEM) of the estrous cycle was 23.9 ± 0.6 days, and the mean duration of behavioral estrus was 1.6 ± 0.3 days. Mean concentrations (± SEM) of FPM for the luteal phase and inter-luteal phase were 6183.0 ± 2268.7 ng/g and 754.5 ± 216.1 ng/g, respectively.

Reproductive monitoring of collared peccary females (Pecari tajacu) by analysis of fecal progesterone metabolites

The measurement of fecal progesterone metabolites (fPM) by enzyme immunoassay analysis is a non-invasive technique that permits gathering reproductive information from wildlife without the stress associated with restraint. In the collared peccary (Pecari tajacu), a high correlation between serum progesterone and fPM levels (r2 = 0.783) suggests that fPM can be used to monitor their reproductive function. We monitored fPM during the estrous cycle of 15 collared peccary females. Estrous cycles averaged 27.9 ± 4.5 days (n = 28), ranging from 21 to 36 days. The luteal phase was 22.2 ± 4.8 days and the inter-luteal phase was 4.3 ± 1.4 days. Mean concentration of fPM across pregnancy were not different from those found during the luteal phase (1230 ± 718 and 1265 ± 584 ng/100 mg dried feces, respectively), however, significant differences were found when luteal phase concentrations were compared only against fPM concentrations during late pregnancy. In addition, late pregnancy fPM concentrations (1893 ± 551 ng/100 mg) were also significantly higher than those in the early (639 ± 339 ng/100 mg) and mid (1134 ± 449 ng/100 mg) pregnancy. For females during the early post-partum period, fPM concentrations were significantly increased (243 ± 118 ng/100 mg) than those of non-cycling females (103 ± 89 ng/100 mg). The analysis of fPM is a simple, non-invasive methodology to detect the ovarian activity in the collared peccary; moreover, it provides a husbandry tool, which may be used to help understand how social structure may impact reproduction.

Non-invasive hormonal characterization of the ovarian cycle, pregnancy, and seasonal anestrus of the female addra gazelle (Nanger dama ruficollis)

Non-invasive fecal hormone metabolite monitoring was used to characterize the estrous cycle, pregnancy, and seasonal anestrus of the critically endangered addra gazelle (Nanger dama ruficollis). With less than 250 animals remaining in the wild and ∼168 individuals managed in captivity, it is crucial to maintain sustainable populations. Progestogen and estrogen profiles were obtained from analysis of fecal samples collected approximately every other day, within varying intervals, over the course of 7 years (n = 8 adult females). Average estrous cycle length was 19.5 ± 0.4 days (range, 14–26 days), with a luteal phase length of 14.6 ± 1.2 days (range, 10–16 days), and an inter-luteal period of 5.2 ± 1.4 days (range, 2–7 days). Mean gestation length for six pregnancies was 200.7 ± 0.4 days (range, 200–202 days). Fecal progestogens increased at 12 weeks of gestation and remained elevated until parturition. Addra gazelle females exhibited a period of seasonal anestrus with consistently low progestogen concentrations and no cyclic activity from about September to March. Analysis of reproductive and climate records demonstrated a peak in U.S. births that coincided with maximal rainfall in the native habitat of the addra gazelle. Results show that estrous cycle, luteal phase, and inter-luteal phase lengths in addra are similar to those observed in other gazelle species, however, to our knowledge, this is the first study to demonstrate seasonal anestrus in the Nanger genus.

Ovarian cycle of southern brown howler monkey (Alouatta guariba clamitans) through fecal progestin measurement.

The ovarian cycle in howler monkeys (genus Alouatta) has beean investigated through several biological parameters (ranging between 16.3 and 29.5days); however, no data exist concerning the ovarian activity of the southern brown howler monkey (Alouatta guariba clamitans). This study aimed to describe the ovarian cycle of A. g. clamitans by profiling fecal progestin concentrations. Over 20weeks, fecal samples of eight captive adult females of A. g. clamitans were collected. The collections were made at dawn, 5days a week, and the samples were frozen immediately following collection. Next, they were dried, pulverized and hormonal metabolites were extracted to determine progestin concentrations by enzyme immunoassay. Of the 758 samples tested, the mean concentration of fecal progestins was 2866.40±470.03ng/g of dry feces, while the mean concentration at baseline was 814.47±164.36ng/g of dry feces. Among the eight females, one showed no ovarian cyclicity and three presented periods of probable absence of cyclicity and low progestin concentrations. A mean duration of 16±0.52days was observed for the 35 cycles studied. The interluteal phase lasted 4±0.37days on average, with a mean concentration of fecal progestins of 467.98±29.12ng/g of dry feces, while the luteal phase lasted 11±0.50days, with a mean concentration of 4283.27±193.31ng/g of dry feces. Besides describing the characteristics of the ovarian cycle, possible causes for the low concentrations of fecal progestins and periods of absence of cyclicity are also discussed.

Determination of ovarian cyclicity and pregnancy using fecal progesterone in forest musk deer (Moschus berezovskii)

The forest musk deer (FMD, Moschus berezovskii) is a threatened species in China. Although crucial for its artificial breeding management and thus protection, to date, gonadal steroidogenic activity data are unavailable in this species. Thus, the objectives of the present study were to characterize ovarian activity throughout the estrous cycle, non-pregnant luteal phase, and gestation in female FMD. These goals were accomplished using an enzyme immunoassay to measure fecal concentrations of estradiol (E2) and progesterone. Fecal samples were collected from female FMD (aged 3–4 years) for one year, including during breeding and non-breeding seasons. Non-pregnant estrous cycles were recorded in females, based on fecal progesterone concentrations, their overall estrous cycle length was (mean±SEM) 24.3±0.5 days, with 21.6±0.5 days in the luteal phase and 2.7±0.3 days in the inter-luteal phase. Fecal progesterone and E2 concentrations were also measured in females that became pregnant and gave birth after gestating approximately 6 months. Two weeks after becoming pregnant, the average fecal progesterone concentration was significantly greater than that during non-pregnancy. The average fecal progesterone concentrations during pregnancy increased 3.2-fold above non-pregnant concentrations, decreasing to non-pregnant concentrations only after parturition. By contrast, average fecal E2 concentrations during gestation and after parturition were not different from average non-pregnant concentration. In addition, no difference was observed between progesterone concentration in the first month after pregnancy and the value during the luteal phase. However, progesterone concentration during the second month of pregnancy was significantly higher than the value during the luteal phase. In conclusion, monitoring fecal progesterone is an effective method for assessing ovarian function in FMD and will be a useful tool for breeding management and development of assisted reproductive techniques, such as artificial insemination, in this species.

Fecal progestins during pregnancy and postpartum periods of captive red brocket deer (Mazama americana)

This study aimed to validate the enzyme immunoassay (EIA) for fecal progestin quantification of the species Mazama americana, define its excretion profile during periods of gestation and postpartum and determine the gestation period and resumption of postpartum ovarian activity in this species in captivity. Fecal samples were collected twice a week during gestation and every day in the postpartum period, and analyzed using EIA. The mean concentrations (±SEM) of fecal progestins during gestation were 2180.0±299.1ng/g in early pregnancy (week 1–11), 3271.4±406.9ng/g in middle pregnancy (week 12–22) and 5592.0±1125.8ng/g in late pregnancy (week 23–32). The gestation period determined for the species was 220.9±1.2 days. The concentration of progestins reached its peak prior to parturition and returned to baseline levels in 4±0.31 days after parturition. In the postpartum period, the mean concentrations of fecal progestins were 1564.2±182.6ng/g in the interval between parturition and resumption of ovarian activity, 469.8±24.5ng/g in the inter-luteal phase and 2401.7±318.5ng/g during the luteal phase, such that the postpartum period and the luteal phase differed from the inter-luteal phase. Fecal progestin profiling permitted the detection of ovulation 26.9±3.4 days after parturition in all the hinds studied and estimation of the mean duration of the estrous cycle, 21.3±1.1 days. Analysis established that concentrations of progestins above 3038.76ng/g diagnosed pregnancy, a value determined from the week 12 of gestation. Moreover, the quantification of fecal progestins by EIA proved to be an important tool for noninvasive endocrine monitoring and to obtain reproductive data on the species M. americana in captivity.

Characterization of the estrous cycle and reproductive traits of the aoudad (Ammotragus lervia) in captivity

In this study the estrous cycle of the aoudad has been analyzed and characterized for the first time, using non-invasive methods for tracking reproductive cyclicity. The duration of the estrous cycle is 23 days (range 16–32 days), with a luteal phase of 17 days (range 12–27 days) and an interluteal phase of 6 days (range 3–14 days). The estrous cycle did not differ between females, but it was affected by the time of the year. Intraindividual variation of the cycle was observed in one out of the nine individuals. The average hormone concentration values, the estrogen:progestogen ratio, as well as their minimum and maximum values for each interluteal and luteal phases of the estrous cycle, are shown. Interindividual differences found in these values were basically associated with age. Females tended to start their cycle when in the presence of an adult male. Anestrus was observed in study females except for the oldest (14 years old). Age and anestrus onset were correlated, with younger females starting earlier than the older ones. This study reveals that Ammotragus reproductive biology is more similar to that of Capra than Ovis, except for some endocrinological features.

Fecal progesterone metabolites and ovarian activity in cycling and pregnant mountain gazelles ( Gazella gazella)

Fecal reproductive progestagen monitoring in the mountain gazelle ( Gazella gazella) provided a non-invasive method for tracking reproductive cycling, estimating age of sexual maturity and diagnosing pregnancy in this species of gazelle. Fresh fecal samples were collected from eight female mountain gazelle ( Gazella gazella) for a period of two months. Two of the animals were pregnant while the other six were not. Using the progestagen profile the luteal phase, interluteal (follicular) phase and estrous cycle in adult female gazelles were determined to be 12.5 ± 1.2, 5.9 ± 0.59 and 18.8 ± 0.98 days respectively. Significant inter-animal differences in fecal progestagen concentration were observed in both the luteal and follicular phases. Significant differences were observed in the levels of fecal progestagen between cycling females and females in late pregnancy. Low concentrations of fecal progestagen in females aged less than 18 months old indicated that sexual maturity in captivity is not attained before that age.

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.

Hormonal characterization of the reproductive cycle and pregnancy in the female Mohor gazelle (Gazella dama mhorr).

The oestrous cycles of seven captive Mohor Gazelles (Gazella dama mhorr) were investigated. Hormone profiles obtained from faecal samples collected each day from cyclic females indicated that the mean duration of the oestrous cycle was 18.62 +/- 0.26 days (range 16-22 days; n = 37 oestrous cycles). No inter-individual differences in the concentration of faecal progestagen metabolites excreted were observed, but mean faecal oestrogen excretion during both the luteal and inter-luteal phases of the oestrous cycle varied among females (P < 0.001 and P = 0.070, respectively). Oestrous cycles were synchronized using controlled internal drug release (CIDR) devices, before natural mating with an intact male. Concentrations of faecal progestagen metabolites remained approximately constant for the first 10 weeks of gestation (mean +/- SEM = 4048 +/- 407 ng g(-1) faeces), before increasing to a mean of 23 556 +/- 1176 ng g(-1) faeces. Two of seven female gazelles conceived immediately after removal of the CIDR device, a similar proportion to that conceived at the postpartum oestrus under natural conditions. Life history data for these individuals indicated that the mean time to conception in female gazelles is positively correlated with peak values in the ratio of excreted oestrogen : progestagen during the inter-luteal period of their oestrous cycles (R(2) = 0.58; P < 0.05). This finding indicates that interactions between steroid production and metabolism may influence the likelihood of conception occurring in this species.

Hormonal characterization of the reproductive cycle and pregnancy in the female Mohor gazelle (Gazella dama mhorr)

The oestrous cycles of seven captive Mohor Gazelles (Gazella dama mhorr) were investigated. Hormone profiles obtained from faecal samples collected each day from cyclic females indicated that the mean duration of the oestrous cycle was 18.62 +/- 0.26 days (range 16-22 days; n = 37 oestrous cycles). No inter-individual differences in the concentration of faecal progestagen metabolites excreted were observed, but mean faecal oestrogen excretion during both the luteal and inter-luteal phases of the oestrous cycle varied among females (P < 0.001 and P = 0.070, respectively). Oestrous cycles were synchronized using controlled internal drug release (CIDR) devices, before natural mating with an intact male. Concentrations of faecal progestagen metabolites remained approximately constant for the first 10 weeks of gestation (mean +/- SEM = 4048 +/- 407 ng g(-1) faeces), before increasing to a mean of 23 556 +/- 1176 ng g(-1) faeces. Two of seven female gazelles conceived immediately after removal of the CIDR device, a similar proportion to that conceived at the postpartum oestrus under natural conditions. Life history data for these individuals indicated that the mean time to conception in female gazelles is positively correlated with peak values in the ratio of excreted oestrogen : progestagen during the inter-luteal period of their oestrous cycles (R(2) = 0.58; P < 0.05). This finding indicates that interactions between steroid production and metabolism may influence the likelihood of conception occurring in this species.

Reproductive seasonality in the female scimitar-horned oryx (Oryx dammah)

Faecal oestrogen and progestin analyses were used to assess ovarian activity in non-pregnant scimitar-horned oryx (Oryx dammah) during a 13-month interval. Mean (± SE) luteal phase, interluteal phase and oestrous cycle duration were 18.8 (± 0.5), 5.1 (± 0.2) and 23.8 (± 1.3) days, respectively. All females exhibited a synchronized anovulatory period that ranged from 36–95 days during spring. Short ovarian cycles (10.6 (± 0.8) days) were observed intermittently throughout the year and before the spontaneous resumption of oestrous cyclicity. Periovulatory peaks in oestrogen concentrations were detected for 42.5% (31/73) of ovarian cycles. A parallel analysis of reproductive data from the North American studbook (1985–1994) revealed that captive-held scimitar-horned oryx gave birth throughout the year. Sex ratio at birth was male-biased (54.4%), and 19.1% of all calves failed to survive to 6 months of age (220 out of 1149 births). Only 0.7% of births resulted in twins. Median interbirth interval was 277 days, and 75% of these intervals were less than 332 days. Interbirth interval was extended (P < 0.05) if parturition occurred from January through May. In summary, the scimitar-horned oryx is a seasonally polyoestrous species that experiences a distinct anovulatory period during spring in north-east America.

Reproductive seasonality in the female scimitar‐horned oryx (Oryx dammah)

AbstractFaecal oestrogen and progestin analyses were used to assess ovarian activity in non‐pregnant scimitar‐horned oryx (Oryx dammah) during a 13‐month interval. Mean (± SE) luteal phase, interluteal phase and oestrous cycle duration were 18.8 (± 0.5), 5.1 (± 0.2) and 23.8 (± 1.3) days, respectively. All females exhibited a synchronized anovulatory period that ranged from 36–95 days during spring. Short ovarian cycles (10.6 (± 0.8) days) were observed intermittently throughout the year and before the spontaneous resumption of oestrous cyclicity. Periovulatory peaks in oestrogen concentrations were detected for 42.5% (31/73) of ovarian cycles. A parallel analysis of reproductive data from the North American studbook (1985–1994) revealed that captive‐held scimitar‐horned oryx gave birth throughout the year. Sex ratio at birth was male‐biased (54.4%), and 19.1% of all calves failed to survive to 6 months of age (220 out of 1149 births). Only 0.7% of births resulted in twins. Median interbirth interval was 277 days, and 75% of these intervals were less than 332 days. Interbirth interval was extended (P &lt; 0.05) if parturition occurred from January through May. In summary, the scimitar‐horned oryx is a seasonally polyoestrous species that experiences a distinct anovulatory period during spring in north‐east America.

Reproductive cycle length and pregnancy in the southern white rhinoceros (Ceratotherium simum simum) as determined by fecal pregnane analysis and observations of mating behavior

Pregnancy and the reproductive cycle were monitored in 13 captive southern white rhinoceros (Ceratotherium simum simum) by measuring progesterone metabolites in fecal extracts and by observing behavior patterns. Fecal hormones were measured using a monoclonal antibody produced against 4-pregnen-11-o1-3,20-dione hemisuccinate:BSA. Several subjects exhibited flat or erratic endocrine profiles, but we found evidence for 17 reproductive cycles in five females. Mating behavior coincided with nadirs in pregnane concentrations. These cycles appeared to fall into two general categories: those of approximately 1 month in duration (Type I: X¯ ± SEM = 35.4± 2.2 days; n = 10) and those lasting approximately 2 months (Type II: 65.9± 2.4 days; n = 7). Interluteal phase lengths were similar for the two cycle types, but Type II cycles were characterized by extended luteal phases lasting more than twice as long as Type I luteal phases. Because Type I cycles predominated in our data and because evidence suggests that some Type II cycles may be aberrant, we argue that these approximately monthly cycles represent the typical reproductive cycle for this species. Three females became pregnant during the course of the study. We were able to detect pregnancy by approximately 3 months post-breeding, as indicated by sustained pregnane concentrations markedly higher than nonpregnant luteal phase concentrations. These data help to characterize important reproductive events of this species and should be useful for captive breeding efforts for this threatened species. Zoo Biol 18:111–127, 1999. © 1999 Wiley-Liss, Inc.

Reproductive cycle length and pregnancy in the southern white rhinoceros (Ceratotherium simum simum) as determined by fecal pregnane analysis and observations of mating behavior

Pregnancy and the reproductive cycle were monitored in 13 captive southern white rhinoceros (Ceratotherium simum simum) by measuring progesterone metabolites in fecal extracts and by observing behavior patterns. Fecal hormones were measured using a monoclonal antibody produced against 4-pregnen-11-o1-3,20-dione hemisuccinate:BSA. Several subjects exhibited flat or erratic endocrine profiles, but we found evidence for 17 reproductive cycles in five females. Mating behavior coincided with nadirs in pregnane concentrations. These cycles appeared to fall into two general categories: those of approximately 1 month in duration (Type I: X¯ ± SEM = 35.4± 2.2 days; n = 10) and those lasting approximately 2 months (Type II: 65.9± 2.4 days; n = 7). Interluteal phase lengths were similar for the two cycle types, but Type II cycles were characterized by extended luteal phases lasting more than twice as long as Type I luteal phases. Because Type I cycles predominated in our data and because evidence suggests that some Type II cycles may be aberrant, we argue that these approximately monthly cycles represent the typical reproductive cycle for this species. Three females became pregnant during the course of the study. We were able to detect pregnancy by approximately 3 months post-breeding, as indicated by sustained pregnane concentrations markedly higher than nonpregnant luteal phase concentrations. These data help to characterize important reproductive events of this species and should be useful for captive breeding efforts for this threatened species. Zoo Biol 18:111–127, 1999. © 1999 Wiley-Liss, Inc.

Characterization of Estrous Cyclicity in the Sable Antelope(Hippotragus niger)through Fecal Progestagen Monitoring

Fecal progesterone metabolite monitoring techniques were validated for the sable antelope and used to characterize ovarian cycle dynamics and reproductive seasonality in a captive population at the National Zoological Park's Conservation and Research Center. Hormone was homogeneously distributed within fecal samples. Longitudinal fluctuations in fecal progesterone metabolites were consistent with typical luteal phase patterns and corresponded closely with changes in serum progesterone. The lag time from an im injection of progesterone to peak excretion in feces was 16 h. The pattern of births showed a slight peak in the summer (May–July), but year-round endocrine monitoring of six nonpregnant females showed no evidence of seasonality in ovarian activity. Females exhibited 11–14 estrous cycles per year, averaging 24.2 ± 0.9 days in length. Luteal and interluteal phases were 18.4 ± 0.9 and 5.8 ± 0.4 days in length, respectively. Although only a small number of hippotragine antelope species have been studied, data indicate that they exhibit considerable interspecific variability in estrous cycle length and reproductive seasonality and thus may be a useful group for further investigation of factors regulating fertility.

Resumption of oestrous and ovarian cyclicity during the post-partum period in autumn-lambing ewes is not influenced by age or dietary protein content

AbstractThe objective was to determine the effect of age and dietary protein content on post-partum oestrous and ovarian cyclicity in autumn-lambing ewes. Twenty-four multiparous (age 4·5 (s.e. 0·61) years) and 24 primiparous (age 1·5 years) ewes which lambed on 28 October (s.e. 0·2) and were rearing 2·0 and. 1·7 (s.e. 0·13) lambs, respectively, were equally allocated to two dietary treatments in a 2 × 2 factorial design. Diets comprised a d libitum hay supplemented with concentrate (12·5 MJ metabolizable energy per kg dry matter (DM) and either 210 or 140 g crude protein per kg DM), offered at a daily allowance of 1·2 kg per ewe from lambing to weaning (18 December) and 0·4 kg per ewe thereafter. Throughout the study (3 November to 24 May) ewes were group-housed in straw-bedded pens under natural photoperiod at 57°N and their live weights and body condition scores were assessed at 2-week intervals. A raddled vasectomized ram was continually present with each group and ewes marked by the ram were recorded thrice weekly. Blood samples were obtained thrice weekly for measurement of peripheral progesterone concentrations and ovulation rate was determined by laparoscopy during January and March. There was no significant effect of dietary protein content on any of the variables measured. For multiparous and primiparous ewes, mean live weights and body condition scores at lambing were 79·5 (s.e. 1·41) v. 58·4 (s.e. 1·54) kg (P &lt; 0·001) and 2·5 (s.e. 0·05) v. 2·2 (s.e. 0·05) (P &lt; 0·001) and daily live-weight losses over the suckling period were 153 (s.e. 19·3) v. 85 (s.e. 21·1) glday (P &lt; 0·05). Intervals from parturition to first overt oestrus were 39 (s.e. 3·2) v. 33 (s.e. 2·3) days and to the onset of ovarian cyclicity were 29 (s.e. 4·9) v. 25 (s.e. 1·5) days. Durations of ovarian cyclicity were 133 (s.e. 27·1) and 110 (s.e. 5·7) days (P &lt; 0·01) during which 7·6 (s.e. 0·32) and 6·5 (s.e. 0·34) (P &lt; 0·05) ovarian cycles were recorded respectively. Fifteen ewes had initial short cycles (≤10 days), six had prolonged cycles (≥21 days) and 11 had extended inter-luteal phase intervals (≥8 days). All ewes had recent ovulations at the January laparoscopy but only 19 multiparous and nine primiparous ewes had ovulations in March. Mean ovulation rates were: January 2·2 (s.e. 0·14) and 1·4 (s.e. 0·13) (P &lt; 0·001), and March 1·6 (s.e. 0·23) and 1·2 (s.e. 0·15) for multiparous and primiparous ewes, respectively. It is concluded that, for ewes lambing at their normal time of mating, (i) the strong seasonal drive for reproduction results in the resumption of oestrous and ovarian cyclicity during the early post-partum period; (ii) initial luteal phases may be of short or extended duration; (Hi) there is no effect of age or dietary protein content, within the range studied, on the onset of ovarian cyclicity; and (iv) multiparous ewes experience a greater number of ovarian cycles and achieve higher ovulation rates than primiparous ewes.

Ovulatory cycles and anovulatory periods in the addax (Addax nasomaculatus)

Changes in serum oestradiol and progesterone were measured to study their dynamics during ovulatory cycles in six female addax, an endangered antelope. Blood was collected three times per week, during chute restraint, for 3 months (November to February) before introduction of a male, and continued until pregnancy was diagnosed with ultrasound. Serum was analysed by enzymeimmunoassay. Mean luteal phase, interluteal phase, and cycle durations were 22.7 +/- 2.0, 8.78 +/- 0.5 and 32.3 +/- 1.7 days, respectively. Ultrasonography revealed coiled uterine horns and maximum follicle and corpus luteum diameters of 15 and 27 mm, respectively. Each female experienced an anovulatory period, during which oestradiol continued to fluctuate, but progesterone remained below 2 ng ml-1. These periods ranged from 39 to 131 days and were not synchronous; ovulatory cycles resumed spontaneously in all females. All four females placed with a male conceived. Because addax give birth all year round, they are not considered seasonal breeders. The sporadic periods of anovulation that occurred during the winter months of this study suggest a possible seasonal effect. However, systematic sampling has not been conducted during summer and early autumn and will be necessary to address this question.

Post-Partum and Post-Conceptional Ovarian Activity of Dairy Cows: Evaluation Based on Progesterone Profiles

The progesterone level of milk was measured daily in 20 Icelandic dairy cows for 50-90 days post-partum and for 30-50 days post-conception by radioimmunoassay. In 40% of the cows the 1st post-partum ovarian cycle was shorter and the progesterone level lower than in normal cycles. The average duration of the 1st post-partum luteal phase was significantly shorter and the progesterone values lower than in the 2nd and 3rd phases. The progesterone level rose to a plateau at the onset of luteal function within 5 +/- 2 (mean +/- s.d.) days, whereas the decrease in progesterone at the end of the luteal phase was more rapid i.e. 3 +/- 1 days. The progesterone value for a normal interluteal phase was 1.5 +/- 1.3 nmol/l. However in 9 of 48 interluteal phases the progesterone values did not decline below 3 nmol/l. The average progesterone concentration was significantly increased during the first 30 days post-conception. In 4 of 20 cows a significant drop in progesterone concentration was found 15-19 days post-conception. The results indicate that the luteal activity of the 1st post-partum ovarian cycle is inferior to that of the following cycles. There is a significant correlation in the intensity of the luteal activity between cycles. Ovarian cyclicity continues in early pregnancy in, at least, 20% of cows. The sampling frequency is of importance in studies concerning the luteal activity.