Number Of Oestrous Cycles Research Articles

Long-term chronic stress exposure induces PCO phenotype in rat.

Thus far the effects of chronic stress on the ovary were studied for shorter durations. However, responses of the ovary may vary with durations of exposure to stress. Hence, we investigated the responses of the ovary following exposure to different durations of chronic stress. Exposure of rats to restraint (1 h) and after a gap of 4 h to forced swimming (15 min) daily for 4 or 8 weeks resulted in significant decreases in the activities of the ovarian antioxidant enzymes, 3β-hydroxysteroid dehydrogenase and percentage of healthy granulosa cells with concomitant increases in the number of atretic follicles, the percentage of apoptotic granulosa cells and ovarian malondialdehyde concentration. However, the response of the ovary to similar stress regime for 12 weeks was paradoxical as there were increases in the activities of ovarian antioxidant enzymes and 3β-hydroxysteroid dehydrogenase, the number of healthy antral follicles, and decreases in ovarian malondialdehyde concentration and percentage of apoptotic granulosa cells. These changes were accompanied by hyperglycaemia and an increase in the serum levels of insulin, testosterone and oestradiol. In addition the cystic follicles were found in the ovaries of these rats. However, the number of oestrous cycles and active corpora lutea showed significant decrease in all the durations of stress exposure. The results demonstrate a differential response of ovary to short- and long-term exposure to chronic stress.

EFFECT OF DIFFERENT FEEDING REGIMES ON: 2- PRODUCTIVE AND REPRODUCTIVE PERFORMANCE OF GROWING BUFFALO HEIFERS

This study was conducted to investigate the effect of different feeding levels on productive and reproductive performance and some body measurements of growing buffalo heifers during the period from first services up to ninetieth days of pregnancy. Eighteen buffalo heifers at the first services were divided into three treated groups (6 heifers each) and received their feeding allowance according to Kearl, (1982) in which animals in group one (R1) fed 100% of their allowances up to the end of the experiment (control) and those in group two (R2) fed 80% of the allowances until heifers grow up to 300 kg, and then fed 100% of the allowances up to the end of the experiment, while those in the third group (R3) fed 80% of the allowances during the whole experimental period. Average age of heifers at first service was 517.3, 571.7 and 594.7 days old and live body weight were 347.8, 339.3 and 349.0 kg for R1, R2 and R3, respectively. Results indicated that heifers fed 80% of the allowance (R3) recorded the lowest values in most of nutrient digestion coefficients and feeding values (TDN and CP%) in comparison with the other experimental groups, while CF digestibility had the inverse trend. Also, animals in R3 recorded the lowest (P<0.05) blood constituents and oldest ages at first service and conception than those in other experimental groups. Heifers fed 100% of the allowance (R1) recorded the higher body condition score than those in the experimental groups. There were significant differences between heifers in both R1and R2 in comparison with those in R3 respecting the most of growth performance parameters and animals in both groups (R1 and R2) were significantly better than those in R2. However, Heifers fed 80% of the allowance (R3) had a better (P<0.05) feed conversion ratio expressed as the amount of intake of DM, TDN or CP than those in R1 and R2 groups. Interval from puberty to the first service or to conception was significantly shorter for heifers in R2 than those in R1 and R3 groups. Number of oestrous cycles from Puberty to the first service or to the conception was significantly the lowest with heifers in R1 followed by those in R2 then the highest values were recorded with those in R3 group. It could be concluded that feeding growing buffalo heifers at first service on (R2) had more beneficial effect on heifers’ reproductive performance, indicating positive reflection on the subsequent first lactation season of primiparous cows under Egyptian condition.

Effects of three steroidal compounds on oestrus suppression in queens.

Summary Pregnancy prevention raises much concern to many pet owners. Female cats usually show undesirable behaviour during oestrus. Nowadays, researchers try to explore the reliable and effective ways to prevent oestrus signs in queens. The results of their studies prove that hormone therapy is probably one of the most reliable methods for this purpose. The aim of our study was to compare the effect of three steroidal preparations on oestrus suppression in queens. Twenty clinically healthy adult female cats and three healthy adult male cats with natural libido were used in the present study. The female cats were randomly divided into 4 groups (n = 5). The male cats were caged separately and maintained near females for sexual stimulation. The photoperiod was regulated artificially to induce oestrus in cats (14 h light and 10 h dark). The experimental cats were kept in a roofed room for about 3 months for adaptation and confirmation of oestrus detection. After this period, group I (control group) did not receive any treatment, group II received 12.5 mg methyltestosterone/week orally for 90 days, group III received one tablet of contraceptive LD/day (0.15 mg levonorgestrel + 0.03 mg ethinyloestradiol) orally for 90 days and group IV received 3 mg medroxyprogesterone acetate intramuscularly. The cats were monitored clinically every day (4 h in the morning and 4 h in the afternoon). The number of queens observed in oestrus and the number of oestrous cycles were recorded during the study. The results of the present study showed that in group I (control) oestrus was detected twice in 2 out of 3 cats. In group II oestrus was detected 3 times in 3 cats, which was not statistically different to that of the group I (P>0.05). In group III oestrus was detected 13 times (more than the other groups). All 5 cats of this group showed oestrus, which was statistically increased compared to group I (P<0.05). In group IV no oestrus was detected, which was statistically decreased compared to group I (P<0.05). According to our results, methyltestosterone prevented the oestrus for only 1 month so that it can be used for oestrus suppression for a short time; contraceptive LD unexpectedly increased the frequency of oestrus in queens, therefore this drug can not be advised for prevention of the oestrus in queens; however, medroxyprogesterone acetate completely prevented the oestrus during the treatment. Therefore, Medroxyprogesterone acetate is reliable, and only one injection is sufficient to prevent the occurrence of the oestrous cycle.

The effect of oestrous cycle number, at constant age, on gilt reproduction in a dynamic service system

AbstractPrevious studies examining the effect of age on gilt reproduction have generally failed to discriminate between chronological (i.e. days) and physiological age (i.e. number of oestrous cycles experienced) and the importance of each factor remains unclear in the pig. The present investigation tested the hypothesis that the physiological age at which gilts are bred in a dynamic service system (DSS) affects their reproductive behaviour and performance. A hundred and ninety gilts were randomly allocated between two treatments. They were introduced into the service pens of a DSS to be bred at the same age (215 days) but either at second (2H; no. = 96) or third (3H;no. = 94) post-pubertal heat period. The sexual behaviour of half of them was continuously recorded over a 13-week period and reproductive data from all the gilts were collected. Gilts of 2H treatment were significantly heavier at entry into the service pens (123 v. 119 kg; P &lt; 0·05) than 3H gilts, but there was no significant difference in their backfat thickness. Treatment failed to affect the quality and frequency of mating attempts (MAs) gilts received or oestrus duration. Conception rate to first oestrus in the DSS (82%) was not affected by treatment. Litter size and number of piglets born alive was similar for 3H and 2H gilts (12·0 v. 11·7, s.e.d. 0·40 and 11·5 v. 11·0, s.e.d. 0·4 respectively; all P &gt; 0·05). It is concluded that the reproductive behaviour and performance of gilts that had experienced either two or three oestrous cycles prior to mating at a constant age does not differ significantly in a DSS. More studies are needed in order to clarify the possible interactive influence of repeated and frequent services, which are common in a DSS, on gilt reproduction.

Influence of Nutritionally Induced Anaemia on the Oestrous Cycle of Mice

Investigations were carried out to evaluate the probable effect of anaemia due to food restriction on the oestrous cycle of mice. Female mice were divided into four groups and maintained on normal and restricted diet for 21 days as follows: Group I, maintained on ad libitum food; Group II, 25% diet restriction (2.7 g/day/animal); Group III, 50% diet restriction (1.8 g/day/animal; Group IV, 75% diet restriction (0.9 g/day/animal). Following 21 days diest restriction, the starved mice exhibited weight loss. Haemoglobin concentration and plasma protein levels were found to be reduced in direct proportion to the degree of diet restriction. The red blood cell (RBC) count did not vary much. These observations suggest that diet restriction may interfere with haemoglobin synthesis. Underfed mice exhibited a significant reduction in the average number of oestrous cycles compared to that of normally fed mice. Thus a probable influence of anaemia on mouse oestrous cycle is evident.

The association between basal body temperature, plasma progesterone and the oestrous cycle in a marsupial, the Tasmanian bettong (Bettongia gaimardi).

Basal body temperature, quantitative changes in vaginal smears and plasma concentrations of progesterone were measured during a number of oestrous cycles in Tasmanian bettongs (Bettongia gaimardi). These methods of monitoring the reproductive cycle were compared in an attempt to find a technique that allowed non-stressful assessment of the reproductive condition of the bettongs. Telemetric measurement of basal body temperature showed that there was a diurnal variation of 1.3 degrees C, typical of a nocturnal animal. During the oestrous cycle, there was a small, but not significant, peak in basal body temperature at oestrus (day 0) followed by a significant trough on day 2. There was a significant increase on day 3 and the temperature remained raised until day 10, during which time plasma progesterone concentrations are also high; the temperature then fell 2 days before oestrus. This fall corresponds to a decrease in concentration of plasma progesterone and in the numbers of leucocytes in vaginal smears. Telemetric measurement of body temperature may be useful as a non-stressful method of monitoring the oestrous cycle in bettongs.

Relationship between herd calving to conception interval and culling rate for failure to conceive

The factors affecting herd calving to conception intervals and culling rate are the interval to first service, the efficiency of heat detection, the pregnancy rate and the maximum number of oestrous cycles allowed to occur before the cow is considered to be so far into lactation that even if it does conceive, the length of the dry period and the delay to the next calving will make its production uneconomic. Depending on the fertility factor (the product of the average herd pregnancy rate and the oestrus detection rate) it is the maximum number of oestrous cycles, usually dictated by the length of the calving interval desired, that decides the outcome. A graphical representation of these mathematical relationships demonstrates methods for achieving different economic and other objectives.

Puberty attainment and reproductive characteristics in ewe lambs of Chios and Karagouniki breeds raised on two planes of nutrition

Twenty ewe lambs from each of the two Greek breeds Chios (C) and Karagouniki (K) were assigned at random to high (H) and low (L) planes of nutrition. The level of feeding was adjusted weekly according to live weight so that at the time of expected puberty the animals of the H and L groups would reach 70 and 50%, respectively, of the mature ewe body weight estimated for the flock. The occurrence of oestrus was detected by ram presentation, and the ovarian activity was monitored by progesterone concentrations in blood samples collected twice weekly. Progesterone and oestradiol profiles around the second pubertal ovulation were also determined by blood sampling in twenty animals. Ovulation rate was assessed by laparoscopy at four defined oestrous cycles. Ewe lambs in the H group grew faster ( P<0.01) and were heavier ( P<0.01) at the beginning of the first breeding season than those on the L plane of nutrition. The Chios started to ovulate 12 days earlier ( P<0.05) and showed oestrus 9 days earlier than the Karagouniki ewe lambs. Chios showed breeding activity for 26 days ( P<0.01) longer than the Karagouniki ewe lambs, and animals in the H group 25 days ( P<0.01) longer than those in the L group. The duration of the breeding season and the number of oestrous cycles per ewe lamb were correlated with age at first ( r= −0.71 and r= −0.66. P<0.001) and last ovulation ( r=0.80 and r=0.82, P<0.001). Ewe lambs in the H feeding group showed a significantly higher ovulation rate than those in the L group. Ovulation rates during the second breeding season were affected by carry-over effects of the nutritional regime. The level of progesterone was higher while oestradiol was lower in Chios than in Karagouniki ewe lambs during the luteal phase of the first pubertal cycle. Ewes in the H group had a higher ( P<0.05) oestradiol concentration during the oestrous cycle than ewes in the L group, while the preovulatory peak was of the same magnitude for both feeding groups. The results indicate that the two breeds are different in terms of reproductive characteristics and that differences in growth rate and body weight, imposed by feed intake manipulation in early life, have significant effects on most pubertal reproductive characteristics of the ewes and carry-over effects in their second breeding season.

Hypothyroidism affects reproductive refractoriness and the seasonal oestrous period in Welsh Mountain ewes

Welsh Mountain ewes (n = 6) were rendered hypothyroid by daily treatment with methylthiouracil (35 mg/kg), beginning in early August and ending in late February. Plasma thyroxine levels were reduced by mid-September to about 33% of those in untreated ewes (n = 6). The two groups of ewes were held under natural daylengths until 5 October, then on 12 h light: 12 h darkness (12L:12D) until 28 February when the photoperiod was reduced to 8L:16D. The onset of reproductive cyclicity in October was similar in both groups of ewes but the end of the reproductive period occurred later (P less than 0.05) in the hypothyroid ewes (29 January +/- 7 days (S.E.M.] than in the untreated controls (6 January +/- 7 days). As a result, the duration of the seasonal reproductive period was significantly (P less than 0.05) longer in the hypothyroid (122 +/- 9 days) than in the untreated ewes (91 +/- 10 days). The number of oestrous cycles (duration 15.4 and 15.7 days in the hypothyroid and untreated ewes respectively) was 7.0 +/- 0.6 in the hypothyroid ewes and 5.0 +/- 0.5 (P less than 0.05) in the normal ewes. Reducing the photo-period overcame the reproductive refractoriness and anoestrus in both groups, the hypothyroid ewes beginning to cycle on 13 April (+/- 0.5 days) after an anoestrous period of 72.8 +/- 7.1 days. The untreated ewes began to cycle 2 weeks later on 26 April (+/- 1.7 days) after an anoestrous period of 112.0 +/- 8.5 days (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Oestrous cycle and breeding season of farmed fallow deer, Dama dama.

Oestrus was detected on 177 occasions in 34 fallow does for the duration of the breeding season. A total of 142 cycles had a mean length of 22.4 (+/- 1.3, s.d.) days. Cycle length increased and became more variable as the season proceeded but was not affected by doe age or liveweight. First oestrus occurred within a 12-day period, but the length of the breeding season, and therefore the number of oestrous cycles, was related to doe age. Serum progesterone profiles suggest that silent ovulations, associated with short-lived corpora lutea, occurred before the first behavioural oestrus. Ovulations without oestrus may have also occurred at the end of the breeding season.

Effect on Perinatal Mortality of a Single Selenium Injection To Sows and Gilts

Selenium treatment of pregnant sows and gilts was conducted as a double-blind placebo-controlled study in 5 commercial herds with a total of 350 sows and gilts (Danish Landrace, Yorkshire and Landrace-Yorkshire crossbreeds). At 3–6 weeks before farrowing the animals were injected once intramuscularly with either Na-selenite (0.05 mg Se per kg) or placebo. Blood samples were taken immediately before treatment and once again at 3–6 weeks after farrowing, to evaluate the Se status. The productivity of the sows and gilts was recorded. Within herds there was no pretreatment difference in Se status between the two treatment groups, while a considerable variation was seen among herds. After farrowing there were only minor differences in Se status between the treatment groups, whereas the variation among herds persisted. Overall, no effect of the Na-selenite injection was seen, in that there was no difference in number of liveborn, stillborn, and weaned piglets between the treatment groups. The number of days from weaning to oestrus and the number of oestrous cycles per pregnancy were not influenced by the Na-selenite treatment.

Characteristics of oestrous cycles and plasma progesterone profiles of young female sheep during their first breeding season

ABSTRACTPatterns of oestrous cycle activity in the first breeding season were studied in 30 Suffolk × Mule ewe lambs, Twenty-eight reached puberty and the mean date of first oestrus was 27 November (s.d. 13·6 days). Mean live weight at first oestrus was 37·7 (s.d. 3·63) kg. The mean number of oestrous cycles was 3·3 (s.d. 1·6), 0·92 (65) being normal length single cycles (14 to 19 days), 0·03 (2) long single cycles (20 to 26 days) and 0·05 (4) multiple cycles (&gt; 26 days).Plasma progesterone profiles before and after the breeding season were studied in 10 randomly selected animals. All showed profiles suggesting one or two silent ovulations preceding the first oestrus but none showed any indication of silent ovulations following the last oestrus.Plasma progesterone profiles were also studied on the four animals showing multiple cycles and on the two animals that did not reach puberty. These suggested that, in all four animals showing multiple cycles, one or two silent ovulations had occurred between the two overt oestrous periods. Of the two animals that did not reach puberty, one showed three abnormal silent cycles and the other showed no change in progesterone concentration from a low basal level.

Studies on the breeding season and reproduction of the ewe Part III. The breeding season and artificial light Part IV. Studies on the reproduction of the ewe Part V. Mating behaviour and pregnancy diagnosis

During the course of three breeding seasons, daily observations of oestrus were undertaken on the following groups of ewes, all of which were running with ochred rams. One hundred and twenty ewes (pure bred and first-cross) of different breeds and ages, running with vasectomized rams under natural conditions. Twenty-eight grade Suffolk ewes fed on a submaintenance diet. Eighteen grade Suffolk ewes running with a fertile ram. Twenty ewes of several breeds exposed to artificial light.The effects of heredity (breed and individual), environment (season, year and nutrition), age and artificial light on the breeding season and related phenomena have been investigated. The results and conclusions were as follows:1. (a) There are breed differences in the extent of the breeding season, cycle length, incidence of silent heat and duration of heat (Table 29). (b) The duration of the breeding season is related to the geographical origin (latitude and altitude) of the breed, (c) The duration of the breeding season of the first-cross is intermediate between that of the two parents, (d) Individual differences in the number of oestrous cycles per ewe per season were more marked in the mountain breeds.2. (a) Of the ewe lambs, 79% exhibited oestrus during the shortest days only of the first breeding season. Their breeding season is not spread evenly about the shortest day as it is with adults. (b) The occurrence and length of the breeding season in ewe lambs is associated with early birth dates or with higher growth rates.3. (a) Significant differences exist between breeds in the age at first oestrus. (b) Ewe lambs born early in the season showed their first oestrus at later age and heavier weight than those born late.4. Annual differences in the duration of the breeding season, cycle length, incidence of silent heat and occurrence of first oestrus were negligible.5. (a) Submaintenance diet had no effect on the onset of the breeding season, but it converted oestrus into silent heat. Conception occurred less frequently after periods of underfeeding. (b) At high latitudes nutrition has only a minor effect on the breeding season of the ewe.6. (a) A constant high ratio of artificial darkness (8 hr. light: 16 hr. darkness) hastened the onset of the breeding season some 57 and 27 days in the two experimental groups. (b) A constant high ratio of artificial light (16 hr. light: 8 hr. darkness) hastened the end of the breeding season some 104 days on an average (in one experimental group), (c) There were breed differences in the latency of initiation and of cessation of the induced breeding season, (d) In the induced breeding season cycles of ovulation preceded the first oestrus, (e) Two thresholds of pituitary activity are suggested, one for the onset of ovulation, and the other for the manifestation of oestrus.7. (a) A high frequency of cycles outside the normal range (14–19 days) was observed in the mountain breeds and in ewe lambs. (b) The shortest average cycle length coincided with the shortest days of the year.8. A high frequency of silent heats (during the breeding season) was observed in the mountain breeds, in ewe lambs and during the second half of the breeding season.9. Oestrus was of longer duration in adults and yearlings than in ewe lambs.10. (a) Post-partum heat occurred in 56% of Suffolk ewes with an average lactation anoestrus of 35 days. (b) There is a relationship between the early onset of the breeding season and the incidence of post-partum heat, (c) Conception post-partum is partly inhibited by lactation.11. Mating behaviour was observed in animals of several breeds and ages (three patterns were recorded for ewes and eight patterns for rams).12. Irregular columnar cells in the vaginal smear of the ewe characterized late pregnancy.In addition, the breeding season of wild and domestic sheep was reviewed in relation to the environment with special reference to the length of daylight.