Incidence Of Estrus Research Articles

Behavioural and physical signs associated with oestrus and some aspects of reproductive performance in Fogera cows and heifers.

An investigation was carried out into the behavioural and physical signs of oestrus in 70 Fogera cows and heifers between December 1993 and May 1994 at Metekel Cattle Breeding and Improvement Ranch, Ethiopia. Retrospective information generated from records made between 1991 and 1994 was evaluated for some aspects of the reproductive indices. The mean +/- SD duration of oestrus (n = 136) was 10.6 +/- 4.5 h (range 2.2-21). Most oestruses (63.2%) started during the day (06:00-18:00). The incidence of oestrus was significantly affected by months (chi 2 = 21.86; p < 0.001). Among the physical signs, standing to be mounted was the most consistent indication (97.8%) of oestrus. About 12.5% of the cows in oestrus did not mount other cows. The retrospective study indicated that the mean interoestrus interval for 46 oestruses was 29.2 +/- 19.7 days. The average gestation length for 141 cows was 276 days. Continuous and careful observation of oestrus would reduce the reproductive wastage that arises from less pronounced heat periods and those occurring at night, especially for ranches that use artificial insemination and have a limited number of bulls.

Estrus synchronization in ewes treated with sponges impregnated with different doses of medroxyprogesterone acetate

The objectives of this study were to determine residual and absorbed levels of medroxyprogesterone acetate (MAP) after treatment with intravaginal sponges impregnated with different doses of MAP in an ewe herd and to determine the effects of such treatments upon estrus incidence, interval to estrus onset and pregnancy rate. Polyurethane sponges impregnated with 40, 50 and 60 mg of MAP were prepared. Real amounts of progestagen on sponges were checked prior to sponge treatment insertion. During autumn 1999, 608 cyclic Merino ewes were treated with intravaginal sponges impregnated with different doses of MAP (groups I, 40; II, 50 and III, 60 mg). After 14 days, sponges were removed and residual levels of MAP (RMAP) on removed sponges were measured by spectrophotometry. Real amounts for unused sponges were 39.60±1.10, 44.10±1.06 and 59.10±1.26 mg for the intended doses of 40, 50 and 60 mg MAP respectively. RMAPs were different ( p<0.05) among groups (I: 17.98±1.97 mg; II: 24.32±2.03 mg; III: 34.25±3.23 mg). Absorbed levels of MAP were not different among groups (I: 21.62±1.97 mg; II: 19.78±2.03 mg; III: 24.85±3.23 mg). Artificial insemination was performed in 16 ewes from Group I, 17 ewes from Group II and 11 ewes from Group III, 12 h after estrus onset. There were no differences among groups, neither for estrus incidence (I: 79.27%; II: 77.42%; III: 80.87%) nor interval to estrus onset (I: 55.94±1.87 h; II: 56.74±1.13 h; III: 57.70±1.02 h). There were also no differences among groups for pregnancy rate (I: 43.75%; II: 52.94%; III: 45.45%). It was concluded that under similar conditions, a dose as low as 40 mg MAP could be effectively used for estrus synchronization in cyclic Merino ewes.

The effect of dietary molybdenum and sulphate on sexual activity and plasma progesterone concentrations of ewes

The effect of an induced copper (Cu) deficiency on the fertility of South Africa Mutton Merino ewes ( Ovis aries) was investigated. The incidence of oestrus of adult ewes suffering from an induced Cu deficiency by supplementing molybdenum (Mo – 38 mg Mo/kg feed) and sulphur (S – 0.34%) to their diet was compared to that of a control group (Mo – 1.3 mg/kg; S – 0.22%). Although no significant differences in plasma progesterone concentrations were recorded during the oestrus cycles, 75% of the four-to-six-tooth experimental ewes (Cu deficient) stopped showing signs of behavioral oestrus (silent heats) after 6 weeks on the diets (middle May). In Trial 2, 5-month-old ewes ( n = 13) reaching puberty were used. The effects of an induced Cu deficiency on plasma progesterone concentrations, shortly after reaching puberty, were investigated. According to the plasma progesterone concentrations during the oestrus cycle, Cu deficiency resulted in ewes going into a state of anoestrus approximately 2–4 weeks earlier (May–June) at the end of the active breeding season. Although the older ewes (four-to-six-tooth) still ovulated they did not show any signs of oestrus compared to the younger ewes which stopped ovulating.

Effect of monensin and progesterone priming on ram-induced reproductive performance of boutsiko mountain breed ewes

The effects of monensin and progesterone priming on reproductive performance (estrous response, lambing rate and prolificacy) of grazing Boutsiko mountain breed adult and 18-mo-old ewes at the end of seasonal anestrus were investigated. In Experiment 1 the feed supplement with or without monensin was offered for 21 d after introduction of vasectomized rams (Day 0). Progesterone was administered to the ewes in the respective groups as a single injection at Day -3. Ewes of both age groups were assigned randomly to 1 of 4 treatments: C, C+P, C+M and C+M+P. In Experiment 2 the supplement C or M was offered from Day -26 to Day 21. The treatments consisted of C, C+P and C+M+P. Blood samples were taken 50 h after ram introduction for determination of plasma concentrations of P and insulin-like growth factor-I (IGF-I). There was a greater increase in estrous response at Days 17 to 19 and at Days 0 to 19 when supplementation was offered before rather than after ram introduction in both age groups. In the adult group ewes synchronization of estrus at Days 17 to 19 was significantly increased by administration of monensin (P<0.05) and progesterone (P<0.01) compared with the control group in the first but not the second experiment. The incidence of estrus at Days 17 to 19 or at Days 0 to 19 was highest in the adult groups treated with monensin and progesterone in both experiments. In 18-mo-old ewes progesterone was effective in synchronizing estrus only in Experiment 2. Mean plasma IGF-I concentrations were increased by monensin treatment (P<0.05) in adult ewes that were at the periovulatory stage at blood sampling time. Correlation coefficients between IGF-I and progesterone concentrations in monensin plus progesterone group adults were −0.715 (P<0.02) and −0.516 (P<0.01), respectively across all treatments. The results suggest that monensin and progesterone priming improved reproductive performance, and the monensin-induced increase in plasma IGF-I levels at the periovulatory stage may be causally related to the ability of ovulatory follicles to develop into functional corpora lutea (CL).

Synchronization of estrus and fertility in Zebu beef heifers treated with three estrus synchronization protocols

The effects on estrus and fertility of 3 estrus synchronization protocols were studied in Brahman beef heifers. In Treatment 1 (PGF protocol; n=234), heifers received 7.5 mg, im prostianol on Day 0 and were inseminated after observed estrus until Day 5. Treatment 2 (10-d NOR protocol; n=220) consisted of norgestomet (NOR; 3 mg, sc implant and 3 mg, im) and estradiol valerate (5 mg, im) treatment on Day -10, NOR implant removal and 400 IU, im PMSG on Day 0, and AI after observed estrus through to Day 5. Treatment 3 (14-d NOR+PGF protocol; n=168) constituted a NOR implant (3mg, sc) on Day -14, NOR implant removal on Day 0, PGF on Day 16, and AI after observed estrus through to Day 21. All heifers were examined for return to estrus at the next cycle and inseminated after observed estrus. The heifers were then exposed to bulls for at least 21 d. During the period of estrus observation (5 d) after treatment, those heifers treated with the PGF protocol had a lower (P<0.01) rate of estrual response (58%) than heifers treated with the 10-d NOR (87%) or 14-d NOR+PGF (88%) protocol. Heifers treated with the 10-d NOR protocol displayed estrus earlier and had a closer synchrony of estrus than heifers treated with either the PGF or the 14-d NOR+PGF protocol. Heifers treated with the 14-d NOR+PGF protocol had higher (P<0.05) conception and calving rates (51 and 46%) to AI at the induced estrus than heifers treated with the PGF (45 and 27%) or the 10-d NOR (38 and 33%) protocol. Calving rate to 2 rounds of AI was greater (P<0.05) for heifers treated with the 14-d NOR-PGF (50%) protocol than heifers treated with the 10-d NOR (38%) but not the PGF (43%) protocol. Breeding season calving rates were similar among the 3 protocols. The results show that the 14-d NOR+PGF estrus synchronization protocol induced a high incidence of estrus with comparatively high fertility in Brahman heifers.

Effect of interval between two PGF 2α doses on superovulatory response and embryo recovery in crossbred sheep in tropics

An experiment was conducted to investigate the effects of different superovulatory regimes, including pregnant mare serum gonadotrophin (PMSG) and follicle-stimulating hormone (FSH-P) on steroidogenesis, oestrus, ovulation and premature luteal regression in sheep. Thirty mature Merino ewes were treated in the breeding season with intravaginal progestagen pessaries and 1200 IU PMSG (Group 1), 15 mg FSH-P (Group 2) or a combination of 700 IU PMSG and 11 mg FSH-P (PMSG/FSH-P; Group 3) to induce superovulation. After treatment with FSH-P alone, the incidence of oestrus was lower than after treatment with PMSG alone (6/10 vs. 10/10, P < 0.05) and the incidence of ovulation was lower than after treatment including PMSG (7/10 vs. 20/20, P < 0.05). However, there were no differences in the mean time to onset of oestrus (24.7 ± 2.3 h after pessary withdrawal) or the time to onset of ovulation (48–54 h after pessary withdrawal) between the treatment groups.The total ovarian response (corpora lutea + large follicles) was higher (P < 0.05) following stimulation with PMSG alone (17.1 ± 1.9) than with FSH-P (8.3 ± 12.5). However, the numbers of corpora lutea present on Day 6 (Day 0 = pessary withdrawal) were not affected by the exogenous gonadotrophin treatment (PMSG, 11.4 ± 1.8; FSH-P, 7.2 ± 2.5; PMSG/FSH-P, 11.1 ± 2.1; not significant). The mean pre-ovulatory peripheral plasma peak level of oestradiol-17β (E2) per follicle was higher following treatment with PMSG than with either of the other two regimes (PMSG, 23.2 ± 0.8 pg ml−1; FSHP, 10.8 ± 0.6 pg ml−1; PMSG/FSH-P, 13.9 ± 0.4 pg ml−1; P < 0.05). Moreover, E2 peaked earlier in the ewes treated with PMSG than with FSH-P or PMSG/FSH-P (7.6 ± 2.1 h vs. 33.7 ± 1.5 h and 24.8 ± 0.5 h respectively; P < 0.01). There were no differences detected in the peak levels of luteinizing hormone (LH) (8.6 ± 1.1 ng ml−1) or the mean time to LH peak (32 ± 1.4 h) between the ewes treated with the different exogenous gonadotrophins.Three ewes (one treated with PMSG alone and two with PMSG/FSH) had premature luteal regression by Day 6. In each case, a secondary peak of E2 secretion was observed 36–44 h after pessary withdrawal. These ewes each displayed a second oestrus on Days 5–6 and a mild superovulatory response at this oestrus.It is concluded that in sheep PMSG is highly steroidogenic in comparison with FSH-P. A combination of moderate doses of PMSG and FSH-P is a suitable superovulation regime for Merino ewes as it induces a consistently high superovulatory response without the secretion of excessive E2 levels. Perturbation of the periovulatory endocrine events may result in premature luteal regression.

Effect of eCG on the pregnancy rate of ewes transcervically inseminated with frozen-thawed semen outside the breeding season

An experiment was conducted to determine whether factors affecting pregnancy rate out-of-season are associated more with transcervical artificial insemination (T-AI) procedures or with the reproductive state of the ewe. Twenty Finncross ewes were treated with progesterone sponges, and at sponge removal (0 h) 10 ewes were treated with eCG. Blood samples were collected for LH and progesterone analyses, and follicular development was monitored using ultrasonography. Ewes were inseminated from 48 to 52 h with 200 million motile frozen-thawed spermatozoa. The incidence of estrus, LH surges and ovulation was greater (P<0.01) and intervals to these responses were shorter (P<0.01) in the eCG-treated ewes. The number of follicles >5 mm was higher (P<0.05) in eCGtreated than control ewes. Progesterone concentrations increased and remained elevated through Day 19 in 7 eCG-treated and in 1 control ewe, and these ewes were pregnant based upon ultrasonographic examination. The results demonstrate that the T-AI technique using frozen-thawed semen produces a relatively high (70%) pregnancy rate out-of-season. The pregnancy rate was found to reflect primarily the reproductive condition of the ewe.

Estrous behavior and the estrus-to-ovulation interval in nelore cattle ( [formula omitted] with natural estrus or estrus induced with prostaglandin F2α or norgestomet and estradiol valerate

Estrous behavior and the estrus-to-ovulation interval are essential for estimating the best time to artificially inseminate cattle. Because these parameters are not well characterized in the Nelore breed ( Bos indicus ), the main purpose of the this study was to determine the estrus-to-ovulation interval in Nelore heifers and cows with natural estrus or with estrus induced by treatments with PGF2α or norgestomet and estradiol valerate (NEV). The cows and heifers were observed continuously (24 h a day) to determine the onset of estrus and to study estrous behavior in the cows. Ten hours after the start of estrus the ovaries were scanned every 2 h by ultrasonography to monitor the dominant follicle until ovulation. Blood samples were collected periodically to determine progesterone levels by RIA. Administration of PGF2α (2 injections, 11 days apart) did not induce estrus in most Nelore females in spite of the presence of functional CL, indicated by progesterone concentrations above 6.0 ng/ml in 25 of 28 animals. Treatment with NEV induced high sexual receptivity in cows ( 10 11 ), but only 66% ovulated. Cows with natural or induced estrus exhibited behavioral estrus of 10.9 ± 1.4 h, and ovulation occurred 26.6 ± 0.44 h (n=26) after the onset of estrus. In most of the cows (53.8%) estrus began at night (between 1801 and 600 h), and 34.6% it started and finished during the night. It is concluded that in Nelore females ovulation occurs approximately 26 h after the onset of estrus. Additionally, estrous behavior is shorter than in European breeds, and there is a high incidence of estrus at night, which makes it difficult to detect and, consequently, impairs Al in Nelore cattle. The observation that a high percentage of Nelore females with an active CL did not respond to usual dosages of PGF2α warrants further investigation.

The effect of dietary protein on reproduction in the mare. III. Ovarian and uterine changes during the anovulatory, transitional and ovulatory periods in the non-pregnant mare.

In the main experiment the total daily protein intake and quality (essential amino-acids) was varied in 4 groups of mares. The incidence of oestrus in mares during the transitional period was unaffected by protein nutrition. Ovarian activity, as evaluated by follicular development and size of the ovaries, was affected. Mares that received low-quality protein (Groups 1 and 2) had a higher number of smaller follicles (< 10 mm) that developed during the transitional period compared to mares on a high-quality protein intake (Groups 3 and 4). The mares that received the high quality protein ovulated 2-3 weeks earlier in the breeding season in a synchronised period of 4-5 weeks compared to a period of 6-8 weeks in Groups 1 and 2. The duration of the subsequent oestrous cycles was not affected. There was no difference in the diameter of the largest follicle of mares between groups on the day before ovulation. In a separate experiment, 5 maiden Anglo-Arab mares, 4-5 years of age, were slaughtered at different stages during the anovulatory, transitional and ovulatory periods of the breeding cycle. The morphology of the ovaries and uteri of these mares was described and photographed for use as guidelines when comparing ovarian changes and follicular activity of mares.

Estrus and luteal function in suckled beef cows that were anestrous when treated with an intravaginal device containing progesterone with or without a subsequent injection of estradiol benzoate.

The objectives in this study were to determine whether treatment with progesterone (P4) via an intravaginal device would induce estrus and development of corpora lutea (CL) with typical life spans and whether treatment with estradiol benzoate (EB) following device removal would enhance the responses. At treatment initiation (d 0), suckled beef cows (n = 362) that were anestrous received one of the following: 1) an intravaginal device containing P4 for 7 d plus an injection of 1 mg of EB 24 to 30 h after device removal (P4+EB), 2) an intravaginal device containing P4 for 7 d (P4), 3) a sham device for 7 d plus an injection of 1 mg of EB 24 to 30 h after device removal (EB), or 4) a sham device for 7 d (control). Progesterone treatment increased the proportion of cows that formed CL with a typical lifespan (P < .001) and exhibited behavioral estrus (P < .05). Treatment with EB in combination with P4 increased (P < .001) the proportion of cows that exhibited estrus. Treatment with P4 alone had no effect, but the combination of P4 and EB increased (P < .01) the proportion of cows that formed short-lived or typical lifespan CL by the end of the experiment compared with untreated cows. In summary, treatment with P4 increased the incidence of estrus and the proportion of cows that formed CL with a typical lifespan. Treatment with P4 resulted in resumption of luteal function in suckled beef cows that were anestrous, with most cows developing CL with a typical lifespan, whereas EB enhanced the expression of estrus.

Superovulation and embryo production in ewes using a commercial p-FSH

The effectiveness of a commercial porcine pituitary extract (p-FSH) with a 1:1 FSH/LH ratio was assessed on ovarian response and embryo yield in ewes. During the breeding season, 60 Altamurana ewes were synchronized with FGA-impregnated intravaginal sponges and subdivided into four treatment groups ( n = 15). Beginning 24 h before sponge removal, ewes were treated with 250 (Group 1), 500 (Group 2), 750 (Group 3) or 1000 IU p-FSH (Group 4) administered in a series of four decreasing doses over a period of 36 h. The ewes were monitored for estrus every 4 h, with ovarian response and embryos evaluated on the seventh day following sponge removal. No differences were found among the treatments in incidence of estrus and ovulation. Although treatment with 250 IU p-FSH produced the fewest ovulations, animals in this group yielded a higher ( P < 0.01) number of viable embryos, a lower ( P < 0.01) number of unfertilized ova, and a lower ( P < 0.05) incidence of unovulated follicles and abnormal corpora lutea when compared with animals treated with 750 or 1000 IU p-FSH, while treatment with 500 IU p-FSH yielded intermediate results. It is concluded that the commercial porcine pituitary extract (Pluset) at moderate doses (250 IU) is suitable for superovulation in ewes as it induces a high ovulatory response and transferable embryo yield.

Reproductive Response in Seasonally Anestrous Suffolk Ewes After a Treatment Combining Melatonin Feeding and the 'Male Effect'.

Fifty-eight anestrous Suffolk ewes, raised in Hokkaido, were randomly divided into 2 groups, with or without melatonin feeding as follows: Group 1 ewes (n=33) were fed melatonin daily for 45-90 days from the early or mid-anestrous season (late March to June) and Group 2 ewes (n=25) were not. All the ewes were introduced to fertile rams for 6-12 weeks starting between April and July. The incidence of estrus in Group 1 ewes during the joining of the rams was higher than that in Group 2 ewes (100% vs. 32%, p<0.01). The first estrus in Group 1 was observed 7-10 weeks after the beginning of melatonin feeding. The intervals from the ram introduction to the onset of estrus in 8 ewes that showed estrous response in Group 2 were not distinguishable from those in the ewes fed melatonin for over 5 weeks before the ram introduction in Group 1. The conception rate in Group 1 was higher than that in Group 2 (93.9% vs. 8%, p<0.01). The prolificacy in the Group 1 and 2 ewes was 148% and 8%, respectively. These results indicates that Suffolk ewes were responsive to the 'male effect' 5 weeks onward after the start of the melatonin feeding during early and mid- anestrous season.

Oestrous synchronisation in farmed fallow deer (Dama dama): effects of season, treatment duration and the male on the efficacy of the intravaginal CIDR device

In three experiments conducted over successive breeding seasons'we aimed to determine the effects of season, treatment duration and the male on the incidence of oestrus, oestrous synchrony, ovulation and fertility in farmed fallow deer following treatment with an intravaginal progesterone device (CIDR-G). Stage of breeding season was studied in Experiment 1. Synchronisation involved device insertion for 14 days, with injections of prostaglandin analogue (PG) at insertion and 10 days later. Eighty mature does were divided into four equal groups that each received at least two repeated synchronisation treatments over a 9 week period. Treatment initiation was staggered between successive groups by 7 day intervals from March to May to span the rut. Untreated control does (n = 42) were mated to a crayon-harnessed buck to define the rut. Oestrus was recorded on 69% of occasions and ovulation on 80% among the treated does after device withdrawal. Oestrus was followed by ovulation on 98% of occasions. Silent ovulations occurred most frequently early in the breeding season. An oestrous response was absent initially but increased to 89–100% after the onset of natural rutting. Mean intervals to oestrous onset decreased, and oestrous synchrony improved progressively during the study, reflecting a pronounced seasonal effect.

Performance of crossbred progeny of Trangie Fertility Merino and Booroola Merino rams and Poll Dorset ewes. 3. Reproduction, liveweight and wool production of adult ewes

Reproduction, liveweight and wool production are reported for 4 cohorts of 377 Trangie Fertility x Dorset (TD) and 261 Booroola x Dorset (BD) ewes over 6 years. The BD ewes were 3-4 kg lighter (P&lt;0.001) and had a higher ovulation rate prior to joining in February-March (2.37 � 0.03 v. 1.65 � 0.03) than TD ewes. This resulted in a higher litter size (2.07 � 0.03 v. 1.66 � 0.04) and number of lambs born per ewe joined (1.92 � 0.04 v. 1.56 � 0.04) for the BD ewes. Lamb survival was lower from BD than TD ewes (0.71 � 0.02 v. 0.85 � 0.02), so that the 2 ewe strains weaned the same number of lambs. The growth rate of lambs was lower from the BD ewes and overall they weaned 3.8 kg less (P&lt;0.001) weight of lamb than TD ewes. Chill (index of environmental conditions at lambing), litter size and average birth weight of lambs in the litter (linear and quadratic) affected (P&lt;0.001) lamb survival. At moderate levels of chill there was little difference in survival of single and twin lambs from BD and TD dams when birth weight was 4-5 kg, but survival declined more rapidly for progeny of BD ewes at lower birth weight. Under severe lambing conditions survival was depressed more for lambs born from BD ewes than TD ewes. Almost all ewes expressed oestrus over the 3, 6-week periods, December-January, January-February and March (joining). There was significant variation (P&lt;0.001) in incidence of oestrus due to year and age (linear and non-linear), but not liveweight at joining, and there was little difference between ewe strains. Similarly, for post-lambing oestrus (to fit 8-monthly joining) and post-lambing anoestrous interval, there was little difference between strains, but year and age were highly significant (P&lt;0.001). BD ewes had a lower (P&lt;0.001) greasy fleece weight (3.76 v. 3.86 kg), than TD ewes. BD ewes were classified as either carriers (F+) or non-carriers (++) of the FecB gene, which was significant (P&lt;0.001) for ovulation rate (+1.14 ovulations), litter size (+0.8 lambs), lamb survival (-18%), lambs born per ewe joined (+0.64 lambs) and total weight of lamb born per ewe joined (0.5 kg, P&lt;0.01). The effect of the FecB gene was non-significant for lamb survival when litter size and lamb birth weight (P&lt;0.001) were included in the model. Repeatability estimates based on over 3 records per ewe were about 0.2 for lambs born, weight of lamb born, lambs weaned and weight of lamb weaned per ewe joined. Component traits ranged from 0.27 for litter size to 0.10 for lamb survival, with fertility intermediate (0.15). Greasy fleece weight (0.72) and ovulation rate (0.41) had high repeatabilities with post-lambing anoestrous interval being low (0.11). Repeatability for ovulation rate was reduced to 0.34 when F+ ewes were excluded.

Chronobiological characterization of the first estrous cycle in Brasileiro de Hipismo mares during the postpartum period

This study was conducted on 32 mares during the first 30 d of the postpartum period to characterize the first estrous cycle, assessing ovarian cyclicity by determining plasma progesterone concentration and by transrectal palpation. The total pregnancy rate of the breeding season was 81.25%. The present results show that the incidence of estrus occurring at the beginning of the breeding season were early, long and anovulatory. The mares that did not become pregnant ovulated on average 14.5 d post partum, and those that became pregnant ovulated at 19.6 d post partum (P<0.05). On the basis of clinical and hormonal data, we divided the animals into 4 groups, all presenting signs of estrus: Group 1, animals that did not ovulate (n=7) and that presented basal P(4) levels (0.01-2.34 ng/ml) during the first 30 postpartum days; Group 2, animals that ovulated and did not become pregnant (n=13); Group 3, animals that ovulated and became pregnant (n=8). Maximal P(4) levels ranged from 4.40 to 13.50 ng/ml (Group 2) and from 3.70 to 20.50 ng/ml (Group 3). Group 4 were animals that presented high plasma P(4) levels before any clinical sign of ovulation (n=3). The absence of pregnancy could not be attributed to a failure of the corpus luteum, since the groups of mares that became pregnant exhibited similar plasma P(4) levels as the group of nonpregnant mares. Our findings demonstrated that mares exhibited differences in the timing of the first postpartum estrus, the duration of the first postpartum estrus and the timing of the first postpartum ovulation according to the month of the breeding season in which foaling occurs under tropical conditions. Furthermore, our results indicate that the foal heat may be used since its utilization did not affect the total pregnancy rate of the breeding season.

Estrus Synchronization Using CIDR in Heifers.

The efficacy of the use of controlled internal drug releasing (CIDRR) device containing 1.9g progesterone in inducing estrus synchronization of heifers in Japan was first attested. Eighty-eight Holstein heifers were randomly designated for the 7, 12, and 14 days of CIDRR insertion periods. The effects of CIDRR with and without estradiol-benzoate (E2) and prostaglandin F2α (PGF2α) at 7, 12 and 14 days of insertion periods were evaluated and compared in terms of progesterone concentrations during the 1st and 2nd day of insertion periods, at CIDRR removal and at the AI time; retention rates, estrus incidence, and pregnancy rates.An overall CIDRR device retention rate of 85.2% (75/88), estrus incidence of 90.7% (68/75) and pregnancy rate of 63.3% (38/60) were recorded. Specifically, estrus incidence and pregnancy rates in both 7 days (86.8 and 60.7%) and 12 days (93.3 and 61.5%) insertion groups showed encouraging results. No significant difference was found between treatment groups. However, the 14 days insertion period without the use of additional hormones showed the highest pregnancy rate of 83.3% (5/6). An E2 capsule implanted at insertion and PGF2α injected at CIDRR removal showed no effect on pregnancy rate, but the incidence of 'standing' estrus increased significantly significantly (p<0.05) with PGF2α treatment.

Effectiveness of prostaglandin F2α in the initial treatment of bovine ovarian cysts

This study was conducted to evaluate the use of prostaglandin F2α (PGF2α) in the initial treatment of ovarian cysts in dairy cattle. Two hundred and sixty three cows diagnosed cystic on palpation per rectum were randomly assigned to one of three treatment groups (A, B or C). Cows in Groups A and B were treated with 25 mg i.m.of PGF2α at the time of diagnosis (Day 0), while cows in Group C received 100 μg of GnRH. Seven days following initial treatment (Day 7), cows from Group A that were not observed in estrus were treated with GnRH. Cows from Groups B and C were not treated. On Day 14, all cows that had not been inseminated received PGF2α. A blood sample was obtained from all cows on Days 0, 7 and 14 and was analyzed for progesterone (P4) using radioimmunoassay. Incidences of estrus were recorded and cows that were more than 60 d in milk at the time of diagnosis were bred when observed in estrus. The incidence of follicular cysts on Day 0 (as defined as P4 <0.5 ng/ml) was similar between groups and constituted about 40% of all cysts. There were significantly more cows pregnant to insemination within 7 d of initial treatment in Group B than in Groups A and C (P<0.05). After Day 14, the pregnancy rate was not statistically different between Group B and C, but Groups B and C had a statistically higher pregnancy rate than Group A from Day 21 to Day 35. At the end of the study, there was no statistical difference for the pregnancy rate between groups. We concluded that treatment of ovarian cysts diagnosed by per rectum examination with prostaglandin (at time of diagnosis and 14 d later for cows that were not inseminated) was as effective as initial treatment with GnRH followed by prostaglandins 14 d later for cows that were not inseminated previously. Cows that were initially treated with prostaglandins also tended to become pregnant sooner.

Endocrine responses and conception rates in fallow deer (Dama dama) following oestrous synchronization and cervical insemination with fresh or frozen-thawed spermatozoa

In Expt 1, 59 mature fallow deer does were allocated to six treatments (n = 9-10 per treatment). Does assigned to treatments 1, 2 and 3 each received an i.m. injection of 500 micrograms cloprostenol on day 13 of a luteal cycle. Does in treatments 2 and 3 received 50 or 100 iu pregnant mares' serum gonadotrophin (PMSG), respectively, at the time of prostaglandin administration. Does assigned to treatments 4, 5 and 6 each received single intravaginal controlled internal drug release (CIDR) devices for 14 days. Does in treatments 5 and 6 received 50 or 100 iu PMSG, respectively, at the time of CIDR device withdrawal. Incidence of oestrus was higher following treatment with CIDR devices than with prostaglandin (29 of 30 versus 12 of 29, P < 0.001). PMSG induced earlier onset of oestrus (34.6 +/- 0.9 h versus 44.7 +/- 2.4 h, P < 0.01) and reduced the range in the time to onset of oestrus (from 22 to 8 h for prostaglandin-treated does and from 36 to 14 h for progesterone-treated does). The number of LH surges was higher following treatment with CIDR devices than with prostaglandin (10 of 12 versus 3 of 12, P < 0.01). The overall mean peak LH concentration and time to LH peak were 30.2 +/- 3.4 ng ml-1 and 45.2 +/- 2.2 h after prostaglandin administration or CIDR device withdrawal. The overall median time of ovulation was 26 h after the onset of oestrus.(ABSTRACT TRUNCATED AT 250 WORDS)

The male effect in the Australian cashmere goat. 1. Ovarian and behavioural response of seasonally anovulatory does following the introduction of bucks

The ovulatory and oestrous responses of seasonally anovulatory Australian cashmere does to the introduction of bucks in six experiments are reviewed. Experiments were carried out at Wollongbar (28°48′S, 153°25′E) in February (Experiment 5), March (Experiments 2 and 6), April (Experiments 1 and 3) and October (Experiment 4). Treatments from these experiments in which groups of does ( n=5–20) were exposed to one or two bucks for 10 days in small paddocks or pens are described here. Ovarian activity was determined by laparoscopy pre-experimentally, and on Days 5 and 10 after buck introduction. Oestrus was assessed daily by examination for raddle marks. Overall, 74% of 319 anovulatory does ovulated and 59% exhibited oestrus during the 10 days following buck introduction. Of those does ovulating, 57% ovulated twice during the 10 days, with a short luteal phase separating the ovulations, 25% ovulated once only between Days 6 and 10, 13% ovulated by Day 5 followed by a short luteal phase and a lapse into an anovulatory state, and 5% ovulated before Day 5 followed by formation of a corpus luteum that was still functional on Day 10. Differences between experiments in the proportions of does ovulating appeared to be due to the intensity of the buck stimulus used, rather than variation in female responsiveness. The ovulation rate (mean 1.28, range 1.07–1.44) was positively correlated with doe liveweight within and between experiments and did not differ between the first and second ovulations in does ovulating twice. The incidence of oestrus peaked on Days 2–3 (25% of does) and on Days 7 and 8 (33% of does) with a mean (± SEM) oestrous interval of 5.4 ± 0.14 days. The incidence of oestrus at the first induced ovulation varied widely between experiments (mean 45%, range 14–70%), whereas it was uniformly high at the second ovulation (mean 89%, range 67–92%). The percentage of does exhibiting oestrus at the first ovulation was positively correlated with doe age ( r=0.91, n=6, P<0.05) and was significantly higher amongst does that ovulated twice compared with those ovulating only once. These findings confirm that the male effect is an effective means of inducing ovulation and oestrus in seasonally anovulatory Australian cashmere does and they suggest that the female response may be influenced more by the intensity of the buck stimulus applied, and the age and liveweight of the does, than by seasonal variation in the responsiveness of does.

Effects of PMSG and ram contact on the reproductive performance of progestagen-treated ewes during breeding and anestrous seasons

The objective of this study was to evaluate the efficacy of combinations of PMSG treatment and ram contact on the reproductive performance of progestagen-treated ewes during three different times of the year, Febraury (early anestrus), July (late anestrus) and October (breeding season). A total of 109 multiparous Dorset ewes was used. Ewes were treated with intravaginal progestagen pessaries for 12 days, injected with 500 IU PMSG at pessary removal and either isolated from rams prior to mating ( n = 12, February; n = 12, July; n = 8, October) or exposed to rams during pessary treatment ( n = 17, February; n = 12, July; n = 8, October). A third treatment group ( n = 18, February; n = 6, July; n = 8, October) received pessaries and ram exposure but no PMSG. An additional treatment of progestagen pessaries alone was included in October ( n = 8). There were no differences among treatments in their ability to induce estrus at different times of the year, but incidence of estrus tended ( P < 0.10) to be lower for PMSG treatment during the July breeding. During February, the use of pessaries with PMSG treatment increased ( P < 0.05) conception and lambing rates, whereas ram contact was without any beneficial effects. The trend was reversed during July breeding, when ram contact increased ( P < 0.05) fertility of progestagen-treated ewes compared with other treatment combinations. Pessaries alone were sufficient to attain acceptable levels of fertility and fecundity in October.