Preovulatory follicle development in goats following oestrous synchronization with progestagens or prostaglandins.

The study reports on differences in the dynamics of growth and functionality of preovulatory follicles in response to oestrous synchronization, either by the administration of two doses of prostaglandin or by an intravaginal progestagen sponge, in goats. The progestagen-treated group (n = 8) showed more follicles of preovulatory size (> or =5.5 mm) than the cloprostenol group (n = 8) during the follicular phase (4.5 +/- 0.6 vs 1.9 +/- 0.2, p < 0.01). The diameters of the largest follicles (LF1, LF2 and LF3) were also larger in the progestagen group (LF1, 7.8 +/- 0.3 vs 7.0 +/- 0.2 mm, p < 0.05; LF2, 6.7 +/- 0.2 vs 5.6 +/- 0.2 mm, p < 0.01; LF3, 5.5 +/- 0.3 vs 4.2 +/- 0.2 mm, p < 0.01). The study of the preovulatory follicles showed that 27.2% (3/11) of the follicles were in the static phase in the cloprostenol group, whilst 71.4% (10/14) were static in progestagen group (p < 0.05). Higher plasma oestradiol levels were recorded in the progestagen-treated goats during the 48 h prior to cloprostenol injection or progestagen withdrawal (4.2 +/- 0.4 vs 3.0 +/- 0.2 pg/ml, p < 0.05). In conclusion, goats with oestrus synchronized by progestagen showed a higher number of preovulatory-sized follicles, but a decreased oestradiol secretion when compared with does with oestrus synchronized by using prostaglandin analogues. These would support the development of alternative protocols for assisted reproduction.     

Effect of Nutrition on Plasma Progesterone Levels, Metabolic Parameters and Small Follicles Development in Unstimulated Goats Reared Under Constant Photoperiod Regimen

Sixteen local adult goats were submitted for 9 weeks to 2.09 (high group) and 0.54 (low group) x dietary maintenance respectively. During the experimental period, goats were weighed, oestrus was detected and plasma insulin, urea, non-esterified fatty acids and progesterone concentrations were assessed. At the end of the experiment, ovarian small follicles population was studied by histological analysis. Final weight loss in low group was 18.37 +/- 2.02%, whereas weight gain of high group was 13.84 +/- 2.70%. Insulin and urea were lower in low group, while non-esterified fatty acids were significantly higher. A lower number of fasted goats was in oestrus or ovulated and an extended length of oestrus (p < 0.05) and a higher frequency of short or long cycles (p < 0.05) were also observed. Fed animals showed heavier ovaries (p < 0.01) and a lower number of primordial follicles (p < 0.05). In restricted goats a significant qualitative alteration of follicle classes involved in the initiation process of primordial pool was found. In this phase, granulosa thickness and oocyte size were the most affected (p < 0.01). However in small follicles beyond the primary stage no differences were found between the groups in either number or qualitative characteristics (p > 0.05). Collectively, these results indicate that opposite dietary intakes for a medium period induce a composite reproductive response in goats and can regulate the early onset of follicle growth.     

Assessment of the Intensity of Behavioural Traits and Ovulation between Synchronized and Non-synchronized Cows

Thirty cyclic, non-suckled Brahman cows were divided into three groups, all of which were synchronized sequentially with CIDR-B and observed continuously for 100 h to determine different behavioural oestrus signs. Twenty-four hours after implant withdrawal, all synchronized cows in the group, together with all other cows displaying oestrus, were subjected to intensive ultrasonographic observations (every 6 h for 120 h) to pinpoint the moment of ovulation. In the first group, oestrus and ovulation response was 60% (6/10), in the second 44% (4/9) showed oestrus and six ovulated, and in the third group oestrus and ovulation were 80% (8/10). Significant differences were observed between the second and third groups (p < 0.05). No differences were observed in the duration of oestrus, time when oestrus was displayed after implant withdrawal, time of ovulation and onset of oestrus, end of oestrus to ovulation, and intensity of oestrus on a point scale. The relationship between duration of oestrus and time of ovulation was r(2) = 0.16. Ovulation, on average, was 32.1 +/- 14.5 h after the onset of oestrus, 22.3 +/- 16.5 h after the end of oestrus, and 91.8 +/- 16.7 after implant withdrawal, although no significant differences were observed. One non-synchronized animal showed oestrous activity in the second group but failed to ovulate. In the third group, 8 animals showed oestrus, 4 with high concentrations of progesterone. Of the other four one ovulated. In conclusion, oestrous behaviour is not necessarily the best marker to predict the time when ovulation takes place due to variation in the length of the oestrous period and the possible integration of non-ovulatory animals into sexually active groups.     

Origin and characterisation of preovulatory follicles of hyperstimulated oestrous cycles in goats

The origin and evolution of preovulatory follicles (POF) in 9 hyperstimulated (polyovulatory) Serrana goats were characterised. After oestrus synchronisation and detection, transrectal ovarian ultrasonography was performed daily during two complete oestrous cycles. Blood samples were taken every 4 h during 24 h after oestrus detection for preovulatory LH peak and twice a week for plasma progesterone determinations. The interovulatory interval of 14 oestrous cycles with double ovulations was 21.1 +/- 0.3 days. The onset of ovulatory follicular wave occurred 4 days (-3.9 +/- 0.3 days, n = 14) prior to the ovulation day (day 0) with a POF size of 6.9 +/- 0.2 mm (n = 28). In goats with ovulations in both ovaries (78.6%), the emergence of the first POF occurred earlier (-4.1 +/- 0.3 days) than the second POF (-3.3 +/- 0.2 days, n = 11, P < 0.05). No differences in the total number of follicles > or = 2 mm were found between the day of POF emergence (4.3 +/- 0.4) and the day before ovulation (3.5 +/- 0.3, P > 0.05). These results showed the existence of a delay between the emergence of first and second POF and suggest a weak dominance effect in goats with double ovulations.     

Timing of preovulatory LH surge and ovulation in superovulated sheep are affected by follicular status at start of the FSH treatment.

The aims of this study were to evaluate the chronology of periovulatory events (oestrus behaviour, LH surge and ovulation) in 16 superovulated Manchega sheep and to determine whether follicular status at start of the FSH supply might affect their occurrence. Mean timing for onset of oestrus behaviour was detected at 28.1 +/- 0.7 h after sponge withdrawal; the preovulatory LH surge and ovulation started at 37.2 +/- 0.7 h and 65.4 +/- 0.7 h after progestagen withdrawal, respectively. The intervals between oestrus, LH surge and ovulation were affected by a high individual variability, which might be the cause for reported decreased efficiency in embryo production. Current results also addressed the role of follicular status at start of the superovulatory treatment on the preovulatory LH surge and the ovulation. The interval LH surge-ovulation was increased in ewes with a growing dominant follicle at starting the FSH treatment (32.3 +/- 0.9 vs 28.6 +/- 0.5 h, p < 0.05). The developmental stage of the largest follicle at starting the superovulatory treatment also affected occurrence of LH surge and ovulation; follicles in growing phase advanced the occurrence of the LH surge and ovulation when compared to decreasing follicles (33.0 +/- 1.0 vs 43.5 +/- 1.1 h, p < 0.05, for LH peak and 60.7 +/- 1.1 vs 72.8 +/- 1.2 h, p < 0.05, for ovulation). Thus, only ewes with growing follicles ovulated prior to 55 h after sponge withdrawal; conversely, no sheep with decreasing follicles ovulated earlier than 67 h, when an 85.7% of the ewes bearing growing follicles has ovulated at 63 h.     

The effect of timing of administration of oestradiol benzoate on characteristics of oestrus,timing of ovulation and fertility in Bos indicus heifers synchronised with a progesterone releasing intravaginal insert

OBJECTIVE: To compare the timing of onset of oestrus and ovulation, characteristics of oestrus, and fertility in Bos indicus heifers synchronised with a progesterone releasing intravaginal insert (IVP4) and administration of oestradiol benzoate (ODB) either at the time of removal of the insert or 24 h later. Design: Cohort study. PROCEDURE: Bos indicus and Bos indicus cross heifers were treated on two farms (Farm A, n = 273; Farm B, n = 47) with an IVP4 for 8 days with 1.0 mg of ODB administered at the time of device insertion and 250 mg of cloprostenol at the time of device removal. Heifers in the ODB-0 group were administered 0.75 mg of ODB at the time of device removal while heifers in the ODB-24 group were administered the same dose of ODB 24 h after device removal. Heifers were inseminated once daily after detection of oestrus. Heifers not detected in oestrus by 72 h after removal of inserts were inseminated at that time. Oestrus was detected in heifers on Farm A using heatmount detectors while on Farm B oestrus in heifers was monitored using radiotelemetry of mounting pressure. Ovarian follicular development was monitored daily in 30 heifers on Farm B from the time of administration of inserts until ovulation to a maximum of 96 h after removal of inserts, and again 11 days after removal of inserts (Day 19). A blood sample was collected from all heifers on Farm B on Day 19 and analysed for plasma concentration of progesterone. Pregnancy was diagnosed 6 to 8 weeks after insemination. RESULTS: Administration of ODB at the time of removal of inserts shortened the time interval to oestrus and ovulation (P < 0.001), increased the number of mounts recorded during oestrus (P = 0.04) and reduced the odds of pregnancy (P = 0.03). The proportion of heifers ovulating on Farm B was 67% and was not affected by treatment group (P = 0.61). The mean diameter of the largest follicle measured in ovaries was greater at the time of removal of inserts (9.1 +/- 0.6 vs 10.7 +/- 0.4; P = 0.03) and at the expected time of the LH surge (8.1 +/- 0.4 vs 11.5 +/- 0.3 mm; P < 0.001) in heifers that ovulated compared to heifers that failed to ovulate, respectively. Emergence of a new follicular wave was not detected during the synchronisation treatment in heifers that failed to ovulate. Concentrations of progesterone in plasma on Day 19 were less in non-pregnant heifers (P = 0.05) compared to heifers subsequently diagnosed as pregnant to insemination and were affected by the diameter of the ovulatory follicle (P = 0.01). CONCLUSION: Administration of ODB at the time of removal of inserts can shorten the time interval to oestrus and ovulation and can reduce fertility when insemination is carried out once daily. Further work is needed to determine if prolonged suppression of follicular development, anovulatory oestrus and premature ovulation occuring in some heifers is associated with administration of ODB.     

Effect of Modified Eros Centre on Some Reproductive Parameters of the Sow

The effect of a modified eros centre on weaning to oestrus interval, follicle size, ovulation and farrowing rate and total born litter size was investigated. In modified eros centre 94.4% and in group housing 79.1% of the sows (p < 0.01) expressed oestrus within 10 days post‐weaning. Weaning to oestrus interval was shorter (p < 0.001) for sows kept in modified eros centre. The interval from onset of oestrus to the time of ovulation was longer for sows in group housing (p=0.05). The time of ovulation was negatively correlated (r=?0.50) with the interval from weaning to oestrus (p=0.005). The time of ovulation after onset of oestrus was significantly (p < 0.05) shorter for sows expressing oestrus within 2–4 days of weaning, compared with the animals that expressed oestrus between days 5 and 6 post‐weaning and was shortest for sows expressing oestrus after day 6 post‐weaning. Farrowing rate was not affected by a modified eros centre. Litter size tended to be smaller in group‐housed weaned sows (p=0.10). The timing of last artificial insemination relative to time of ovulation did not affect litter size (p > 0.10). The implication of these results is that a modified eros centre may improve some of the post‐weaning oestrous parameters of the sow.     

Comparison of oestrus synchronisation programmes in dairy cattle using oestradiol benzoate, short-acting progesterone and cloprostenol, or buserelin and cloprostenol

AIM: To evaluate the efficacy of a programme using oestradiol benzoate, progesterone and the prostaglandin-F2 (PG) analogue, cloprostenol, to synchronise oestrus and ovulation in dairy cows, compared with a programme using a gonadotropinreleasing hormone (GnRH) agonist, buserelin, and cloprostenol. METHODS: Twenty non-lactating dairy cows, at random stages of the oestrus cycle, were randomly assigned to 1 of 2 treatments. In Treatment 1 ( OPPG; n=10), cows were injected with 2 mg oestradiol benzoate intramuscularly (IM) plus 200 mg progesterone subcutaneously (SC) on Day 0, followed by 500 microg cloprostenol IM on Day 9 and 1 mg oestradiol benzoate on Day 10. In Treatment 2 (GPG; n=10), cows were injected with 10 microg buserelin IM on Day 0, 500 microg cloprostenol IM on Day 7 and 10 microg buserelin on Day 9. The ovaries of all cows were examined by ultrasonography, using an 8 MHz probe, from 5 days before the initial treatment until ovulation. Cows were observed for oestrus 3 times daily for 7 days after cloprostenol treatment. Blood samples were collected daily for determination of progesterone, and 6-hourly for 36 h after the second oestradiol or buserelin injection for the determination of follicle stimulating hormone (FSH) and luteinising hormone (LH) concentrations. RESULTS: The percentage of cows observed in oestrus was higher in the OPPG group than in the GPG group (100% vs 55.6%, p=0.018). Treatment with either short-acting progesterone plus oestradiol benzoate or buserelin was followed by atresia or ovulation of the dominant follicle. Emergence of a new follicular wave occurred earlier (p>0.001) in the GPG group (2.2+/-0.2 days) than in the OPPG group (3.6+/-0.2 days). There was no significant difference between treatment groups in the variation of time of follicular wave emergence or size of the largest follicles at either the time of initial treatment (10.8+/-1.4 mm vs 11.1+/-0.8 mm), cloprostenol treatment (13.8+/-0.7 mm vs 14.0+/-1.3 mm) or of ovulation (15.4+/-0.7 mm vs 17.6+/-1.1 mm; p=0.10). The LH surge occurred sooner after the second injection of buserelin (4.0+/-1.0 h) than after the second injection of oestradiol benzoate (22.8+/-1.2 h; p>0.001). The interval between the second injection of oestradiol benzoate or buserelin and ovulation did not differ significantly between treatment groups (1.7+/-0.3 days vs 1.6+/-0.2 days; p=0.69). CONCLUSIONS: The use of short-term progesterone treatment, combined with oestradiol benzoate for follicular wave synchronisation, and cloprostenol to cause lysis of residual luteal tissue, is a promising alternative to established methods of oestrus synchronisation in cows.     

Short‐term intake of β‐carotene‐supplemented diets enhances ovarian function and progesterone synthesis in goats

The effect of β‐carotene supplementation upon luteal activity, measured as number (CLT) and volume (VLT) of corpus luteum, and P4 synthesis in goats, was evaluated. Goats (n = 22, 34 months) were randomly assigned to one of two experimental groups: (i) β‐carotene [Beta, n = 10; body weight (BW = 44.8 ± 1.45 kg), body condition score (BCS = 3.25 ± 0.07)], and (ii) Control (Control, n = 12; BW = 45.30 ± 1.32 kg, BCS = 3.33 ± 0.06). Upon oestrus synchronization, the Beta group received 50 mg of β‐carotene per day during 35 days pre‐ and 17 days post‐ovulation. The day 4, 8, 12 and 16 post‐ovulation, blood samples were collected for quantification of serum P4 concentrations by radioimmmunoassay, and transrectal ultrasonographic scanning was performed at day 18 for evaluating CLT and VLT. Overall, CLT and VLT mean were 3.10 and 2211.1 mm³ respectively. The Beta‐goats depicted both the largest values for CLT (p = 0.07) and serum P4 levels (p = 0.05), with no differences (p = 0.53) for VLT between treatments. Results suggest a higher efficiency within the cellular‐enzymatic groups defining the steroidogenic pathways in the β‐carotene‐supplemented goats, generating a larger P4 synthesis. The last is essential for ovulation of healthy oocytes, maintenance of uterine quiescence, nourishment and survival of the embryo around implantation; all of them of paramount significance during the maternal recognition of pregnancy process.     

Pregnancy Rate Obtained with Short-term Protocol for Timed Artificial Insemination in Goats

Recent studies demonstrated that the Short-term Protocol of 5 days of progestogen treatment plus one dose of prostaglandin F(2alpha) and equine chorionic gonadotrophin (eCG) resulted in a close synchronized ovulation (60 h after the end of treatment approximately). In addition, oestradiol benzoate (ODB) is effective in synchronizing ovulation in goats and could be an alternative to eCG. This study was performed to determine the pregnancy rate using the Short-term Protocol comparing: (i) two different moments of timed artificial insemination (TAI) after eCG treatment (trial 1) and (ii) ODB as an alternative to eCG treatment (trial 2). In trial 1, 250 IU of eCG was given at the end of progestogen exposure, and cervical TAI with fresh semen was performed 48 h (n = 156) or 54 h (n = 168) later. In trial 2, 250 IU of eCG was given at sponge withdrawal (eCG group, n = 154) or 200 mug of ODB was given 24 h later (ODB group, n = 119). TAI was performed 54 h after the end of progestogen treatment. Pregnancy rate was determined by transrectal ultrasonography. In trial 1, the pregnancy rate for goats with TAI performed at 54 h (107/168, 63.7%) was higher than for those with TAI performed 48 h (77/156, 49.4%; p < 0.05) after sponge withdrawal. In trial 2, pregnancy rate was higher in eCG (94/154, 61.0%) than in ODB (49/119, 40.3%; p < 0.05) treated goats. In conclusion, the highest pregnancy rate was achieved using Short-term Protocol associated with eCG and TAI performed 54 h after treatment.     

Timing of follicular phase events and the postovulatory progesterone rise following synchronisation of oestrus in cows

In cows the timing of both ovulation and the subsequent postovulatory progesterone rise are critical to successful fertilisation and early embryo development. The aim of this study was to determine the degree of variability in the timing of ovulation relative to other follicular phase events and to determine how variations in the timing of follicular phase events contribute to the timing of the postovulatory progesterone rise. Plasma concentrations of progesterone, oestradiol and luteinising hormone (LH) and the timing of oestrus and ovulation were determined following induction of luteolysis were determined in 18 mature, non-lactating Holstein-Friesian cows. Four cows were excluded on the basis of abnormal reproductive function. In the remaining 14 cows oestrus occurred at 57.4+/-4.3h and the LH surge at 54.6+/-4.0h following luteolysis (progesterone <1ngmL(-1)) followed by a fall in circulating oestradiol concentration at 64.6+/-4.4h. Cows ovulated at 88.0+/-4.7h with the postovulatory progesterone rise (to >1ngmL(-1)) occurring 159+/-7.2h after luteolysis. There was considerable variation in the timing of ovulation following luteolysis (range 64-136h) onset of oestrus (range 24-40h) and onset of the LH surge (range 24-44h). Cows were then split on the basis of interval from progesterone fall to progesterone rise giving groups (n=7 per group) with intervals of 180.6+/-6.7 and 138.3+/-5.7h (P<0.001). Between groups, both the intervals from luteolysis to ovulation (98.3+/-6.9 vs 77.7+/-3.4h; P<0.05) and ovulation to progesterone rise (82.3+/-4.2 vs. 60.6+/-5.5h; P<0.01) were longer in late rise cows. There was no difference between groups in the interval from oestrus or LH surge to ovulation. In conclusion the results of this study further highlight the high variability that exists in the timing and interrelationships of follicular phase events in the modern dairy cow, reemphasising the challenges that exist in optimising mating strategies. However, the data do suggest that in cows with poor post ovulatory progesterone secretion, the key problem appears to be poor post ovulatory development rather than a delay in ovulation.     

The Effect of Intravaginal Applied GnRH-agonist on the Time of Ovulation and Subsequent Reproductive Performance of Weaned Multiparous Sows

In order to prove the effect of 'fixed time insemination' and insemination at standing oestrus after post-weaning application of GnRH, in a Croatian large breeding unit, 502 sows were assigned to three groups and were artificially inseminated (AI) at their first post-weaning oestrus as many times as they stand, in 24-h intervals. The groups were treated as follows: group 1 (control, n = 160) were AI during their standing reflex; group 2 ['GnRH-fixed time insemination' (GnRH-FT-AI), n = 175] were AI, independent of detection of oestrus and following administration of GnRH-agonist at 96 h post-weaning; group 3 [GnRH insemination at standing oestrus (GnRH-OE-AI), n = 167] the animals were GnRH-agonist treated as group 2 and were AI at their standing reflex. Pre-trial daily average lactational feed intake, average daily feed intake from weaning to oestrus, oestrus within 6 days post-weaning (%), ovulation within 6 days post-weaning (%), weaning-to-oestrus interval (h), duration of oestrus (h), follicle size (mm), interval from oestrus to ovulation (h), subsequent day 24 pregnancy rate (%), farrowing rate (%) and total pigs born were evaluated. Pre-trial average daily lactational voluntary feed intake was 7.1 +/- 0.08 kg in group 1, 7.0 +/- 0.07 kg in group 2 and 7.1 +/- 0.17 kg in group 3 (p > 0.05). Average voluntary daily feed intake from weaning to oestrus was 5.1 +/- 0.3 kg in group 1, 5.2 +/- 0.5 kg in group 2 and 5.2 +/- 0.19 kg in group 3 (p > 0.05). Oestrus was detected within 6 days post-weaning in 134 (83.8%) in control, 164 (93.7%) in GnRH-FT-AI and 155 (92.8%) animals in GnRH-OE-AI groups (p = 0.05). Follicle size did not differ (p > 0.05) among the groups. In control 82.8%, in GnRH-FT-AI 91.5% and in GnRH-OE-AI 91.0% of the sows ovulated within 6 days post-weaning (p = 0.04), and had 80.6, 90.9 and 89.7% 24-day pregnancy rates (p = 0.16), respectively. In GnRH-FT-AI group 90.2%, in GnRH-OE-AI sows 89.7%, in control animals 79.9% farrowing rates were recorded (p = 0.17). Weaning to oestrus interval was 113.1 h in control, 114.1 h in GnRH-FT-AI and 112.6 h GnRH-OE-AI (p > 0.05). Duration of oestrus was significantly shorter in GnRH-FT-AI (44.9 h) and GnRH-OE-AI (48.1 h) animals, compared with the control (62.9 h) sows (p = 0.001). Similarly, the interval from oestrus to ovulation revealed significant (p = 0.004) differences between the groups (control 44.1 h, GnRH-OE-AI 34.1 h and GnRH-FT-AI 32.9 h). GnRH-FT-AI (12.5) and GnRH-OE-AI (12.6) sows had significantly higher (p = 0.01) number of total pigs born (n = 10.4) compared with control sows. GnRH-agonist-gel treatment to the sow shortens duration of oestrus, the interval from oestrus to ovulation, and may eliminate the need for oestrus detection in the hands of skilled personnel.     

Influence of CRH and ACTH Administration on Endocrine Profile and Ovulation in Sows

Grouping of sows is a stressful event until the ranking is established. The purpose of this study was to simulate stress by repeated administration of porcine corticotropin releasing hormone (CRH) and adrenocorticotropic hormone (ACTH)/tetracosactide and to study its influence on endocrine profile and ovulation. Four multiparous sows were used and blood was collected every 2 h from the onset of pro-oestrus until 12 h after ovulation. The first oestrus after weaning was used to check ovulation and acclimate the sows to their environment. The second oestrus after weaning was used as control. At their third oestrus CRH (0.6 microg/kg) and at their fourth oestrus ACTH (5 microg/kg) were given every 4 h from onset of oestrus until ovulation. The total 'area under the curve' of cortisol was twofold larger in two of four sows during the CRH treatment period, and two- to fourfold larger (p < or = 0.05) during the ACTH treatment period, compared with the corresponding control period. In three sows, there was no clear effect of either CRH or ACTH on the levels of oestradiol 17beta, luteinizing hormone (LH) or on the timing of ovulation. One sow was different in all hormonal patterns and also in the timing of ovulation. In all four sows, ACTH treatment lowered the baseline level of prostaglandin F(2 alpha)-metabolite. Therefore, we conclude that stage of the oestrous cycle seems to be of importance when investigating the influence of exogenous administration of CRH/ACTH on hormonal pattern and ovulation time in the sow.     

Administration of hCG 5 days after Breeding and Reproductive Performance in Nulliparous Dairy Goats

The objective of this study was to investigate the effect of hCG administration 5 days after breeding on plasma progesterone (P4) concentration and reproductive performance of oestrous-induced nulliparous dairy goats. A total of 59 nulliparous goats (36 Alpine and 23 Saanen) received intravaginal sponges with 60 mg medroxyprogesterone acetate for 9 days plus 200 IU equine chorionic gonadotrophin (eCG) and 22.5 microg d-cloprostenol 24 h before sponge removal. After detection of oestrus (day of oestrus = day 0) and breeding, 49 females were randomly assigned, according to the breed, into two treatments (T1 and T2). In T1 (n = 25) and T2 (n = 24), animals received intramuscular injection of 1 ml of saline solution (control) or 250 IU hCG, respectively, 5 days after breeding. Plasma P4 concentration (ng/ml) was determined from blood sampled on days 0, 5, 7, 13, 17, 21, 28 and 45 after breeding. Animals were scanned by transrectal ultrasound (5 MHz probe) on days 35 and 70 after breeding for detection of pregnancy. Plasma P4 concentration did not differ (p > 0.05) between treatments in all days, but it was increased (p < 0.05) in Saanen than in Alpine goats from days 13 to 45. Pregnancy and parturition rates, litter size and gestation period were similar (p > 0.05) to treatments and breeds. Results of this study indicate that human chorionic gonadotrophin (hCG) administration 5 days after breeding did not significantly alter reproductive performance in dairy nulliparous goats and that plasma P4 differed between Saanen and Alpine goats.     

Patterns of Follicular Growth in Superovulated Sheep and Influence on Endocrine and Ovarian Response

Objectives of this study were to characterize patterns of follicular development in sheep superovulated with purified follicle stimulating hormone (FSH) (OVAGEN^TM, ICP, Auckland, New Zealand) and to determine its influence on preovulatory events (onset of the oestrus behaviour and timing of the preovulatory luteinizing hormone surge) and ovarian response (ovulation rate and embryo yield). Number and size of all ≥ 23 mm follicles from the first FSH injection to withdrawal of progestagen sponges was determined by transrectal ultrasonography just prior to every FSH injection in nine Manchega ewes superovulated with eight decreasing doses (ml) (1.5 × 3, 1.25 × 2 and 1 × 3) of OVAGEN injected twice daily from 60 h before to 24 h after the withdrawal of 40 mg fluorogestone acetate sponges. Oestrous detection and jugular blood sampling for LH radioimmunoassay were performed every 3 h from 14 to 53 h after sponge removal and ovulation rate and number of embryos were determined 4 days after progestagen withdrawal. Administration of OVAGEN induced a significant rise (p < 0.0005) in the number of follicles ≥ 4 mm in size because of an increased growth in size of follicles from the first FSH injection to sponge removal, an increase in the number of newly detected follicles from 12 to 36 h of the first FSH dose (p < 0.005) and a decrease in regression rate from 24 h (p < 0.001). The number of follicles 2–3 mm in size at first FSH dose (10.4 ± 1.5) was positively correlated with the number of ≥ 4 mm follicles at 0 h (19.0 ± 2.7, p < 0.01). A higher number of ≥ 4 mm follicles at 0 h was related with an earlier appearance of oestrus (31.5 ± 1.5 h, p = 0.08) and LH surge (45.0 ± 2.3 h, p < 0.005), and a higher ovulation rate (18.2 ± 3.8, p < 0.005). On the other hand, the rate of embryo recovery was decreased in ewes with earlier preovulatory LH peaks (p < 0.005), with a shorter interval between oestrus and LH peak (p < 0.05).     

Peri-oestrus hormone profiles and follicle growth in lactating sows with oestrus induced by intermittent suckling.

This study describes follicle dynamics, endocrine profiles in multiparous sows with lactational oestrus compared with conventionally weaned sows (C). Lactational oestrus was induced by Intermittent Suckling (IS) with separation of sows and piglets for either 12 consecutive hours per day (IS12, n = 14) or twice per day for 6 h per occasion (IS6, n = 13) from day 14 of lactation onwards. Control sows (n = 23) were weaned at day 21 of lactation. Pre-ovulatory follicles (> or =6 mm) were observed in 100% of IS12, 92% of IS6 and 26% of C sows before day 21 of lactation and in the remaining 74% C sows within 7 days after weaning. All sows with pre-ovulatory follicles showed oestrus, but not all sows showed ovulation. Four IS6 sows and one IS12 sow developed cystic follicles of which two IS6 sows partially ovulated. Follicle growth, ovulation rate and time of ovulation were similar. E(2) levels tended to be higher in IS sows (p = 0.06), the pre-ovulatory LH surge tended to be lower in IS12 (5.1 +/- 1.7 ng/ml) than in C sows (8.4 +/- 5.0 ng/ml; p = 0.08) and P(4) levels were lower in IS12 and IS6 than in C sows (at 75 h after ovulation: 8.8 +/- 2.4 ng/ml vs 7.0 +/- 1.4 ng/ml vs 17.1 +/- 4.4 ng/ml; p < 0.01). In conclusion, sows with lactational oestrus induced by IS are similar to weaned sows in the timing of oestrus, early follicle development and ovulation rates, but the pre-ovulatory LH surge and post-ovulatory P(4) increase are lower.     

The time of oestrus and ovulation following various synchronisation techniques using progesterone impregnated intravaginal devices

SUMMARY Progesterone releasing intravaginal devices (PRIDs) were used in 4 experiments involving 67 cattle to study the effect of the stage of the oestrous cycle and of oestradiol benzoate (ODB) administration on the time interval from PRID removal to oestrus and/or ovulation. Cows in which PRIDs were inserted on days 2 to 4 of the oestrous cycle for 14 days were subsequently observed by endoscopy to ovulate significantly later than cows given identical treatments on days 13 and 14 of the cycle. The concentration of progesterone was higher in the former group at the time PRIDs were removed and remained at a higher level for 3 days thereafter. The length of the oestrous cycle of untreated heifers was significantly longer than in heifers treated for 12 days with PRIDs only inserted on day 3 of cycle (19.7 v 18.2; p <0.01). Treatment with PRIDs inserted for 12 days together with ODB further shortened the cycle length from 18.2 days to 16.9 days (p <0.01). The intervals from PRID removal to onset of standing oestrus in heifers treated with PRID only and those treated with PRID and ODB were 80h and 45h, respectively (p <0.01); the respective variances were 280 and 4; p <0.01). Plasma progesterone concentration, at PRID removal, was 3 times higher in heifers treated with PRID only than in heifers treated with PRID and ODB (p <0.01) and the interval from PRID removal to the lowest progesterone value following it was 3.8 and 1.2 days for the 2 groups, respectively (p <0.05). The study indicated that the stage of oestrous cycle at PRID insertion is an important factor which influences the interval from withdrawal of PRIDs to ovulation. The results suggest closer synchronisation would follow insertion in the mid-luteal phase (Day 13 to 14) or use of ODB treatment at the time of insertion of PRIDs.     

Follicle Development during Luteal Phase and Altrenogest Treatment in Pigs

Synchronization of the oestrous cycle of gilts using altrenogest treatment has been found to increase ovulation rate. The current experiment investigated if the increase in ovulation rate after altrenogest treatment is related to increased follicle size at the end of altrenogest treatment compared with late luteal phase follicles. Crossbred gilts (n = 15) received altrenogest during 18 days [20 mg Regumate (Janssen Animal Health, Beerse, Belgium)], starting 5-7 days after onset of first oestrus. Control gilts (n = 15) did not receive altrenogest. At days 10-12 of the oestrous cycle [i.e. in the presence of corpora lutea (CL)], average follicle development was 2.51 +/- 0.20 mm (assessed with ultrasound) in altrenogest-treated gilts and 2.58 +/- 0.16 mm in control gilts (p > 0.10). During the last days of altrenogest treatment (i.e. when CL had gone into regression), average follicle size had increased to 3.01 +/- 0.31 mm (p < 0.05). Subsequent ovulation rate was 16.6 +/- 1.7 in altrenogest treated gilts and 15.1 +/- 1.2 in control gilts (p < 0.05). Altrenogest treatment resulted in increased follicle size after regression of the CL, showing that suppression of follicle growth by altrenogest alone is less severe than suppression by endogenous progesterone (either with or without altrenogest). Altrenogest treatment also resulted in a higher ovulation rate. However, it is unclear if the increased follicle size and higher ovulation rate after altrenogest treatment are causally related, as the relation between the two on an animal level was not significant.     

The effect of intravaginal applied gonadotropin-releasing hormone agonist on different oestrous parameters and reproductive performance in post weaned sows

In a Hungarian large breeding unit, 481 weaned sows were assigned to three groups and were treated as follows. Sows in Group 1 (Control, n=161) were artificially inseminated (3.01 +/- 0.4 times) during their standing reflex; sows in Group 2 (n=160) were artificially inseminated 3 times at 12-hour intervals, independent of detection of oestrus and immediately after administration of a GnRH-agonist at 96 hours postweaning; and sows in Group 3 (n=160) were artificially inseminated 3 times at 12-hour intervals, beginning at their standing reflex after administration of a GnRH-agonist. Pre-trial daily average lactational feed intake, average daily feed intake from weaning to oestrus, oestrus within 6 days of weaning (%), ovulation within 6 days of weaning (%), wean-to-oestrus interval (h), duration of oestrus (h), follicle size (mm), interval from oestrus to ovulation (h), subsequent day 24 pregnancy rate (%), farrowing rate (%) and total number of pigs born were evaluated. Pre-trial average daily voluntary lactational feed intake was 7.1 +/- 0.5 kg in Group 1, 7.2 +/- 0.4 kg in Group 2, and 7.3 +/- 0.7 kg in Group 3 (P > 0.05). Average voluntary daily feed intake from weaning-to-oestrus was 4.3 +/- 0.9 kg in Group 1, 4.2 +/- 0.8 kg in Group 2, and 4.1 +/- 0.5 kg in Group 3 (P > 0.05). Oestrus was detected within 6 days of weaning in 143 (88.8%) sows in Group 1, 143 (89.4%) sows in Group 2, and in 142 (88.8%) sows in Group 3. Follicle size did not differ (P > 0.05) among the groups. In Group 1, 83.2%, in Group 2, 90.6%, and in Group 3,91.3% of the sows ovulated within 6 days of weaning (P < 0.05), but there were no significant (P > 0.05) differences in 24 Day pregnancy rates (81.4%; 91.3%; and 92.5%). Farrowing rates were in Group 1, 84.5%, in Group 2, 91.3%, in Group 3, 91.9% (P > 0.05). Wean-to-oestrus interval was 115.5 h in Group 1, 114.9 h in Group 2, and 115.7 h in Group 3 (P > 0.05). Duration of oestrus was significantly shorter in Group 2 (41.9 h) and Group 3 (42.1 h) than in Group 1 (68.3 h) (P < 0.001). Similarly, the interval from oestrus to ovulation was significantly different (P < 0.01) between the groups (Group 1, 49.0 h Group 2, 32.0 h, and Group 3, 31.1 h). Sows in Group 2 (12.7) and Group 3 (12.6) had a significantly higher (P < 0.01) number of pigs born than sows in Group 1 (n = 10.9). The interval between oestrus and ovulation was highly and positively correlated (r = 0.83) with the duration of oestrus.     

Effects of Exogenous ACTH during Oestrus on Early Embryo Development and Oviductal Transport in the Sow

This study was conducted to assess the effects of ACTH injections on the early development of embryos and their transportation to the uterus. Fifteen sows were monitored for ovulation using transrectal ultrasonography during the first two oestrous periods after weaning. The sows were randomly divided into a control group (C group, n = 8) and an ACTH-treated group (ACTH group, n = 7), and were all surgically fitted with intra-jugular catheters. From the onset of the second standing oestrus after weaning, the sows were injected (NaCl/synthetic ACTH) every 4 h. Blood samples were collected immediately before and 45 min after each injection. All sows were inseminated once 10-33 h before ovulation in their second oestrus after weaning. At 48 (n = 4) or 60 (n = 11) h after ovulation during their second oestrus, the sows were killed and the embryos retrieved from the oviduct and uterus. The embryos were counted and compared with the number of corpora lutea, cleavage rate was noted and, finally, the embryos were prepared for confocal laser scanning microscopy and transmission electron microscopy. There was no difference between the groups regarding cleavage rate, the cytoskeleton, or the number of active nucleoli. However, the ACTH group had significantly (p < 0.05) fewer ova/embryos retrieved (51%) than the C group (81%), and there was a tendency towards faster transportation to the uterus in the ACTH group, possibly because of high progesterone concentrations during treatment. To conclude, administration of ACTH every 4 h from onset of oestrus to 48 h caused significant loss of oocytes or embryos, and possibly faster transportation through the oviduct.