Metabolic and reproductive status are not improved from 11 to 25 day post-partum in non-weaned primiparous rabbit does

The aim of present work was to analyze the body reserves and ovarian features of lactating primiparous rabbit does under extensive reproductive management (artificial insemination (AI) at 25 days post-partum (dpp)) compared with the common insemination rhythm at 11 dpp. A total of 48 primiparous Californian×New Zealand White rabbit does suckling 8 kits were used to assess liveweight, estimated body composition, serum metabolic and endocrine parameters (oestradiol and progesterone concentrations) and ovarian features like follicle population and atresia rate, and oocyte maturation. Rabbit does were randomly allocated in two experimental groups: (a) lactating does euthanized at early post-partum period (11 dpp) according to a semi-intensive rhythm (n=24), and (b) lactating does euthanized at later post-partum period (25 dpp) according to a more extensive rhythm (n=24). Liveweight, body energy content, lipid depots and serum non-esterified fatty acids (NEFA) concentrations decreased from parturition to post-partum period (P<0.05). In addition, serum protein and glucose concentrations increased in the post-partum period (P<0.05). Similar oestradiol and progesterone levels were found in rhythms as well as similar follicle population and nuclear and cytoplasmic maturation rates measured as metaphase II and cortical granule migration, respectively in both post-partum times. However, the number of preovulatory follicles on the ovarian surface was lower (P<0.05) and the atresia rate tended to be higher with a lower percentage of healthy follicles (P<0.1) in ovaries from females of extensive group. In conclusion, the body reserves, serum metabolic parameters and oocyte quality of primiparous non-weaned rabbits does at the late post-partum time (25 days) were not improved. Thus this reproductive management did not present any advantages compared to earlier post-partum (11 days) reproductive rhythm.     

Oestrus synchronisation of rabbit does at early post-partum by doe-litter separation or ECG injection: Reproductive parameters and endocrine profiles

Inseminating rabbit does at early post-partum, in combination with early weaning, can increase prolificacy (total kits born and still born per parturition) and decrease parturition intervals. Oestrus synchronisation increases fertility and prolificacy, while decreasing the number of inseminations required for gestation. However, little is known about the effectiveness of different oestrus synchronisation methods at early post-partum. In this study, does (n = 138) were artificially inseminated nine times (over a period of 1 year, kits weaned at 25 days), on day 4 post-partum after separation from the litter (for 48 or 24 h) or 48 h after 25 UI eCG injection. Plasma levels of prolactin and estradiol were also evaluated in a subsample of 12 multiparous lactating does per treatment, on days 2, 3 and 4 post-partum. The three treatments increased overall fertility of multiparous females compared to controls (which were not synchronised), but there were no differences among treatments in total kits born or stillborn. Does treated with eCG had a higher culling rate. The interval between parturitions and the number of inseminations required for gestation tended to decrease with increasing number of inseminations. In lactating does, there was an interaction between treatment and insemination order. Fertility decreased with increasing inseminations in eCG does but tended to increase above control values in the separated does until the fourth insemination. Control lactating does had significantly less kits per parturition compared to treatments, but eCG lactating does had more stillborn kits. Oestradiol levels increased on day 4 post-partum in all synchronised lactating does (and immediately before artificial insemination in 48 h doe-litter separation), so ovarian activity could be stimulated at early post-partum using all treatments. However, the increase could not be explained by prolactin levels, since there were no effects of suckling absence on plasma prolactin in separated does. In conclusion, separating does from the litter before insemination can be just as effective as eCG treatment, especially during for the first four inseminations.     

Influence of hormonal and nonhormonal estrus synchronization methods on follicular and oocyte quality in primiparous lactating does at early postpartum period

High-yield lactating does need effective estrus synchronization methods to improve their reproductive outcome by enhancing ovarian function. The aim of the current work was to analyze ovarian follicular and oocyte characteristics of hormonal and nonhormonal estrus synchronization regimes in primiparous lactating rabbit does (Oryctolagus cuniculus) in the early postpartum period (Day 11). Females were randomly treated with either (1) a hormonal standard treatment with 25 IU equine chorionic gonadotropin (eCG) 48 h before artificial insemination (eCG group) or (2) an alternative nonhormonal treatment consisting of doe-litter separation 24 h before artificial insemination (Bio group). No significant differences were found in serum estradiol and progesterone concentrations between experimental groups. During the histologic study, the Bio group presented a higher number of primordial (P < 0.05) and primary follicles (P = 0.07) compared with that of the eCG group, whereas secondary and antral follicular populations were similar. Rates of late atretic follicles assessed by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling technique were not different between treatments, but the eCG group showed a significantly higher number of mid-atretic follicles compared with that of the Bio group. Nuclear in vitro oocyte maturation (IVM), measured as metaphase II rate, and in vitro steroidogenic response of cumulus-oocyte complexes, measured by ELISA, did not show significant differences between treatments. However, confocal study showed that cytoplasmic maturation of oocytes, in terms of cortical granule migration rate, was significantly higher in the Bio group compared with that after the eCG treatment. In conclusion, transient doe-litter separation seems to improve ovarian response in terms of follicular health and oocyte competence compared with that after the eCG treatment. Therefore, a 24-h-long transient weaning could be an alternative nonhormonal method for synchronizing estrus in primiparous lactating rabbit does inseminated in the early postpartum period.     

Influence of different reproductive rhythms on serum estradiol and testosterone levels,features of follicular population and atresia rate,and oocyte maturation in controlled suckling rabbits

The aim of the current work was to analyze the features of ovarian follicular population and their quality in New Zealand white rabbit does synchronized by 24-h controlled doe-litter separation before artificial insemination (AI) during all their reproductive cycles. Synchronized animals were allocated systematically in two groups. A total of 73 rabbit does (group A) were submitted to a 35-day intensive rhythm (AI on day 4 post-partum [pp] and weaning at 25 days of lactation), and 108 rabbit does (group B) were submitted to a 42-day semi-intensive rhythm (AI on day 11 pp and weaning at 35 days of lactation) during 9 months. At the mid-end of their reproductive life, a total of 26 does (5.4 parturitions), under intensive (n = 15) or semi-intensive rhythm (n = 11) were either treated in each group with 25 IU eCG 48 h before laparotomy to recover their ovaries (n = 7 for group A and n = 6 for group B) (according to the Bioethics Committee of the University) or not synchronized with the hormonal treatment (n = 8 for group A and n = 5 for group B). Blood samples were collected at the moment of ovary recovery; morphometrical parameters, number of total follicles and number of follicles ≥1 mm in size in the ovarian surface were recorded. Oocytes from follicles of one ovary were recovered and matured in TCM 199 supplemented with 10 ng/ml EGF, 100 ng/ml IGF-I and 10% FCS. The counterpart ovaries were fixed in paraformaldehyde solution for histological studies. Detection of cell apoptosis was determined using the terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labelling (TUNEL) technique. Reproductive performance was affected by the rhythm used, with lower reproductive parameters in the intensive group. The average ovary height and width, the mean number of ≥1 mm follicles and the number of total follicles were similar between groups. Serum concentrations of estradiol (E₂) and testosterone (T) were significantly lower in group A vs. B (E₂: 232.4 ± 56.1 vs. 399.7 ± 53.0 pg/ml; P < 0.05 and T: 1.07 ± 0.10 vs. 1.68 ± 0.23 ng/ml; P < 0.05). No significant differences were found in follicular population or in the mean follicular apoptosis index between groups. Metaphase II rate was significantly lower in group A vs. B (48.5 ± 3.3 vs. 67.6 ± 3.7%; P < 0.01), as well as the migration rate of cortical granules (12.7 ± 2.7 vs. 38.2 ± 6.6%; P < 0.001). On the other hand, neither follicular population, nuclear maturation rate nor apoptosis rate were affected by the eCG treatment, but cytoplasmic maturation was higher in animals treated with eCG in group A (29.2% vs. 5.5%; P < 0.01). In conclusion, rabbit does under transient litter separation during their reproductive life have both their serum estradiol and testosterone concentrations and oocyte quality influenced by the intensive rhythm, leading to a decrease in reproductive parameters. Also, both intensive and semi-intensive rhythms seem to be less receptive to eCG treatment than expected.     

Effect of different number of frozen spermatozoa inseminated on the reproductive performance of rabbit does

The relationship between the number of frozen spermatozoa inseminated and fertility rate and litter size at birth in rabbit does was investigated. Six hundred artificial inseminations (AI) were performed on multiparous lactating does with three spermatozoa concentrations: 10, 25, 50x10(6)spermatozoa/AI. All the does were synchronized with 20 UI of eCG 2 days before AI. The estimated sexual receptivity was 87%. The freezing-thawing procedure strongly reduced kinetic and functional traits (acrosome integrity, capacitation) of the spermatozoa. The number of spermatozoa inseminated did not affect the reproductive performance: the mean fertility rate and litter size values were 51.5% and 7.6%, respectively. Sexually receptive does (n=522) inseminated with frozen spermatozoa showed a 58.0% fertility rate whereas, non-receptive does (n=78), had a very poor fertility rate (7.8%).     

Evolution of anti-eCG antibodies in response to eCG doses and number of injections. Relationship with productivity of rabbit does

The aim of this experiment was to study the kinetics of anti-eCG (equine chorionic gonadotrophin) antibodies in relation to eCG dose (8 or 25 IU) and number of injections (n = 11) in comparison with a control group (no injection), and to relate antibody production to sexual receptivity and productivity of rabbit does. In all, 124 lactating primiparous rabbit does were inseminated every 35 days for a year. Just before eCG injection (48 h before insemination), blood samples were collected from all the does to assay anti-eCG antibodies. The anti-eCG antibody binding rate, regardless of the injected dose, shows that none of the does developed detectable anti-eCG antibodies before the 7th injection. The level of detectable anti-eCG antibodies began to show an increase at the 7th injection and was significant only for the 25 IU dose at the 11th injection. At the end of the experiment, 15% and 39% of does treated with 8 and 25 IU, respectively, developed immunity to eCG (binding rate >6%: higher binding rate of the control group). Consequently, the immune response depends on the eCG dose and on the number of injections. Moreover, productivity of does estimated from the number of weaned rabbits produced per insemination is not influenced by the level of eCG antibodies (7.0 and 6.9 for binding rate <6% and binding rate 6%, respectively). Only 19 inseminations (n = 6 and n = 13 for 8 and 25 IU, respectively) were made on hyperimmune does. Consequently, the immune response to eCG seems to be marginal for rabbit does. Moreover, under the described experimental conditions, reproductive performances of hyperimmune does were not affected.     

Induction/synchronization of oestrus and ovulation in dairy goats with different short term treatments and fixed time intrauterine or exocervical insemination system

Two experiments were carried out on Ionica dairy goats in order to test the efficiency of: (1) short term-5-day combined progestogen-PGF2α-GnRH treatments on induction/synchronization of oestrus and fertility after natural mating in lactating goats and during the transition period (Experiment 1); (2) short term-9-day FGA-PGF2α-eCG treatments on synchronizing oestrus and ovulation (Experiment 2.1) and artificial insemination (AI) fixed time system in synchronized does (Experiment 2.2), during the breeding season. In Experiment 1, four treatment groups (N=24) were considered: (1) FPe-11d - control, FGA intravaginal sponges (11 days)+PGF2α (9th d)+eCG (11th d); (2) FPe-5d, FGA (5 days)+PGF2α (5th d)+eCG (5th d); (3) PFe-5d, PGF2α (D0)+FGA (5 days)+eCG (5th d); (4) GPe-5d, GnRH (D0)+PGF2α (5th d)+eCG (5th d). Goats were checked for oestrus and naturally mated. The occurrence of oestrus was 75.0, 78.3, 86.4, and 58.3% for groups 1-4, respectively, with significant differences (P<0.05) between groups 3 and 4. Interval to oestrus was earlier (P<0.05) in GPE-5d than in FPe-11d control group. There were no differences between the groups (P>0.05) in fertility or in prolificacy. In Experiment 2.1, 22 goats were subdivided into two treatment groups (N=11): (T1) FPe-11d (control), FGA (11 days)+PGF2α (9th d)+eCG (11th d); (T2) FPe-9d, FGA (9 days)+PGF2α (7th d)+eCG (9th d). Oestrus and ovulation times were monitored every 4h; ovulation rate was also determined. The induction of oestrus ranged from 91 to 100% and all goats ovulated. Intervals to oestrus, from the onset of oestrus to ovulation, from sponge removal to ovulation, and ovulation rates were 28.2±4.9 and 26.0±4.0h, 25.3±9.2 and 28.9±7.4h, 53.5±7.6 and 54.9±7.1h, 3.7±1.6 and 2.4±1.4 corpora lutea (P<0.05) for T1 and T2, respectively. In T2 a great abnormal ovulatory response was observed. In Experiment 2.2, 48 goats were synchronized with FPe-9d treatment and subjected to AI, performed 50h after s.r. with frozen semen, and subdivided into 2 AI system groups (N=24): T3, exocervical AI (100×10(6)Spz/doe); T4, intrauterine AI (20×10(6)Spz/doe). Fertility rate was higher (P<0.05) in T4. It seems that short term-5-day combined progestogen-PGF2α-GnRH-eCG treatments need to be investigated for AI fixed time.     

Effect of eCG on early resumption of ovarian activity in postpartum dairy cows

The purpose of the present study was to hasten the resumption of ovarian activity early postpartum in lactating dairy cows, using equine chorionic gonadotropin (eCG), to enhance follicular growth, followed by hCG, to induce ovulation. Primiparous Holstein dairy cows (n=21) were assigned equally into eCG, eCG-hCG and Control groups. Cows in the eCG and eCG-hCG groups received an i.m. injection of eCG (500 IU Folligon?) on Day 6 postpartum. Cows in the eCG-hCG group were also given an i.m. injection of hCG (500 IU Chorulon?), once dominant follicle reached the diameter of 13-16 mm following eCG injection. Cows in Control group did not receive any treatment. Daily blood sampling and ultrasound examination were conducted, starting at Day 6 postpartum until confirming the third ovulation. Follicles ≥10 mm in diameter were detected on Day 11.5±1.48, 10.1±0.52 and 11.1±1.36 after calving in Control, eCG and eCG-hCG groups, respectively (P>0.05). The first wave dominant follicle ovulated in 71.4% of cows treated with eCG and eCG-hCG. In contrast, none of the first wave dominant follicles ovulated in Control cows. By Day 20 postpartum, all cows in eCG group, 6/7 cows in eCG-hCG group and none of the cows in Control group ovulated (P<0.05). Short estrous cycles (≤16 days) were detected in 2/7, 1/7 and 6/7 cows in eCG, eCG-hCG and control groups, respectively (P<0.05). In conclusion, injection of eCG on Day 6 postpartum could assist the early resumption of ovarian activity by enhancing ovarian follicle growth and early ovulation in postpartum cows. In this context, subsequent hCG injection may not provide any more beneficial effect.     

Comparison of oocyte developmental competence and follicular steroid content of nulliparous heifers and cows at different stages of lactation

Reduced reproductive performance and lower conception rates of lactating cows are closely associated with genetic progress for high milk production. In contrast, the fertility of nulliparous Holstein heifers has remained fairly stable over the years and appears to be markedly higher than that of mature lactating cows. Possible differences in oocyte quality and follicular steroid levels, which could be associated with the low fertility of high-lactating cows, were examined in 13-month-old heifers, cows around the time of first AI (60-95 d post-partum, yielding 49+/-2.4 kg/d) and cows at mid-lactation (120-225 d post-partum, yielding 37+/-2.1 kg/d). Estrus was synchronized by two doses of PGF2alpha and follicles (5-8 mm) were aspirated on days 4, 8, 11 and 15 of the cycle by an ultrasound-guided procedure. Oocytes were morphologically examined, matured in vitro, chemically activated and cultured for 8d. Cleavage rate and the proportion of developing parthenogenetic blastocysts were determined on days 3 and 8 post-activation, respectively. On day 17, heifers and cows received additional PGF2alpha and follicular fluids from preovulatory follicles were collected on day 19 perior to the expected estrus. Follicular-fluid volumes were similar in cows and heifers, as were estradiol, progesterone and androstenedione concentrations in the follicular fluid. Percentages of high-grade oocytes, proportions of cleaved oocytes and developed blastocysts did not differ between the groups. Results suggest that the fertility gap between nulliparous heifers and high-lactating cows is not directly related to steroid content in the preovulatory follicular fluid or oocyte developmental competence.     

Ovarian responses and embryo survival in recipient lactating Holstein cows treated with equine chorionic gonadotropin

The objectives of Experiment 1 were to determine a dose of eCG that would increase total luteal volume and plasma progesterone (P4) concentration on estrous cycle Day 7 in cows. The objectives of Experiment 2 were to determine the effects of treating embryo recipient lactating Holstein cows with eCG on pregnancy per embryo transfer (P/ET). In Experiment 1, lactating dairy cows at 63 ± 3 d postpartum (DIM) received no treatment (control, n = 10), or 600 (eCG6, n = 19), or 800 (eCG8, n = 19) IU of eCG 2 d after the start of the ovulation-synchronization protocol, Day -8 (Day -10 GnRH, Day -3 PGF_2α, Day 0 GnRH). Blood was sampled on Days -10, -8, -3, 0, 7, and 14 for P4 concentration. Ovaries were examined by ultrasound on Days -10, -3, 0, and 7. In Experiment 2, lactating dairy cows were paired according to parity and previous insemination (0 or > 1 insemination) and assigned to receive 800 IU of eCG (eCG8, n = 152) 2 d after the start of the ovulation-synchronization protocol (Day -10 GnRH, Day -3 PGF_2α, Day 0 GnRH) or to receive no treatment (control, n = 162). Blood was sampled on Days -10, -3, 0, 7, and 14 for determination of P4 concentration. Ovaries were examined by ultrasound on Days -10, -3, and 7, and cows with a CL > 20 mm in diameter on Day 7 received an embryo. In Experiment 1, P4 concentration on Day 7 was higher (P < 0.05) for eCG8 cows (2.3 ± 0.3 ng/mL) compared with control (1.2 ± 0.3 ng/mL) and eCG6 (1.1 ± 0.3 ng/mL) cows. In Experiment 2, eCG8 primiparous cows had more (P < 0.01) follicles > 10 mm on Day -3 compared with control primiparous cows (2.5 ± 0.9 vs 1.7 ± 0.5 mm), but multiparous control and eCG8 cows did not differ. A larger (P = 0.03) percentage of control cows received an embryo (87.5 vs 79.1%) compared with eCG8 cows. Among cows that received an embryo, total luteal volume on Day 7 was affected (P = 0.05) by treatment (eCG8 = 8.3 ± 0.4 cm³, control = 6.2 ± 0.4 cm³), but P4 concentration on Day 7 did not differ significantly between treatments. The percentage of cows pregnant 53 d after ET (overall, 24.2%) was not significantly different between control and eCG8 cows. In the current study, no differences in P/ET were observed between control and eCG8 cows and treatment with eCG increased the percentage of cows with asynchronous estrous cycle.     

Embryo yield and plasma progesterone profiles in superovulated dairy cows and heifers.

This study was conducted to compare the superovulatory (SOV) response of dairy cows (n=172) and heifers (n=172), with two SOV treatments started at the mid-luteal-phase of the estrus cycle. Donors were randomly treated either with equine chorionic gonadotrophin (eCG) plus neutra-eCG serum (eCG+N group, n=167) or follicle stimulating gonadotrophin (FSH-P group, n=177).No significant differences were observed among groups in the percentage of superovulatory responsive donors (SR donors; corpora lutea (CL) >/=2), the mean number of total ova, fertilized ova and viable embryos recovered. Cows yielded significantly less total ova and less fertilized ova (P<0.05) and tended to yield less viable embryos (P<0.06) than heifers.Plasma progesterone (P4) concentrations (n=135 donors) on the day of PGF(2alpha) (PGF) injection and on the day of SOV estrus were significantly higher (P<0.01) in eCG+N than in FSH-P donors and, the increase between those 2 days was also significantly higher (P<0.05) in group eCG+N than in group FSH-P, suggesting a higher luteotrophic effect of eCG than FSH-P. SR donors had P4 levels significantly higher (P<0.001) than non-SR donors only on day 5 after the SOV estrus and on the day of embryo recovery. Plasma P4 concentrations at 5 days after the SOV estrus and at embryo recovery correlated significantly (r=0.76, P<0.001).Heifers had significantly higher P4 levels than cows at gonadotrophin injection (P<0.01), PGF injection (P<0.001), 5 days (P<0.01) and 7 days (P<0.001) after the SOV estrus. At day 7 after the SOV estrus, P4 concentrations per ova recovered were significantly higher in heifers than in cows (P<0.01). The increase of plasma P4 per ova recovered, between days 5 and 7 after the SOV estrus, was significantly (P<0.01) higher in heifers than in cows. Also, the increase of plasma P4 between injections of gonadotrophin and PGF was significantly higher (P<0.05) in heifers than in cows.These results suggest that heifers have higher plasma P4 concentrations at diestrus (either before or after the SOV treatment) and this is associated with a higher embryo yield and quality, as compared to lactating cows. These higher plasma P4 concentrations reflect not only differences in ovulation rate as well as the competence of the corpus luteum, which is potentialized by gonadotrophin stimulation.     

Effect of repeated eCG treatments and ovum pick-up on ovarian response and oocyte recovery during early pregnancy in suckling beef cows

This study was designed to evaluate in suckling early pregnant beef cows with and without eCG-pre-stimulation: (i) the influence of day gestation (from 40 to 101 days) and the consecutive eCG treatments on the follicular growth induced by means of ultrasound-guided transvaginal follicle ablation (FA; all follicles ≥ 5 mm) and the number and quality oocytes recovered by ovum pick-up (OPU) and (ii) the possible effects of repeated hormonal stimulation and FA/OPU on pregnancy outcome. Twelve suckling early pregnant Angus cows (40 days post fixed-time artificial insemination) were randomly assigned to each of two groups (n=6 group(-1)). Group 1 treatments included: FA (Day 0), eCG (1600 IU; Day 1) and OPU (Day 5). Group 2: as cited Group 1 with no eCG treatment. In both groups, OPU was repeated five times (Days 45, 59, 73, 87 and 101 of gestation). The numbers (mean ± SEM) of class II (5-9 mm; 4.3 ± 0.9) and class III (≥10 mm; 2.5 ± 0.4) follicles visualized per cow per OPU session in eCG-treated cows were greater (P<0.05) than for non-treated cows (0.9 ± 0.1 and 0.9 ± 0.1, respectively). In contrast, the number (mean ± SEM) of class I (<5mm) follicles per cow per OPU session was lower for cows with eCG treatment (2.8 ± 0.4) than for non-treated cows (5.7 ± 0.5). The mean number of aspirated follicles was not significantly different (P<0.05) between eCG-treated cows and non-treated cows at 45 and 59 days of pregnancy. However, the mean number of aspirated follicles was greater (P=0.03) in eCG-treated cows than non-treated cows from 73 day of pregnancy onwards. The numbers (mean ± SEM) of recovered oocytes and viable oocytes/cow/session were greater (P<0.05) for eCG-treated cows (2.2 ± 0.2 and 1.6 ± 0.4, respectively) than for non-treated cows (1.0 ± 0.2 and 0.9 ± 0.2, respectively). No donor pregnancies were lost either during or following OPU procedure. We can conclude that (1) eCG-treated pregnant suckled cows can be a source of oocytes for IVF at least to 100 days of gestation and (2) repeated FA/eCG treatment/OPU procedures did not affect the pregnancy outcome.     

Progesterone and behavioral features when estrous is induced in Alpine goats

The objective of the present study was to evaluate the endocrine and behavioral features of estrous-induced Alpine goats. A total of 36 nulliparous, 40 non-lactating and 42 lactating does were treated with intravaginal 60 mg medroxyprogesterone acetate sponges for 9 d plus 200 IU eCG and 22.5 microg d-cloprostenol 24 h before sponge removal. Plasma progesterone concentration was analyzed from blood sampled on days 0 (sponge insertion), 5, 8 (cloprostenol administration) and 9 (sponge removal) in 11 nulliparous, 13 non-lactating and 11 lactating does. Estrous response did not differ (P>0.05) among nulliparous (97.2%), non-lactating (90.00%) and lactating does (85.7%). Interval to estrus and duration of estrus did not differ (P>0.05) among nulliparous (22.8+/-9.9 and 25.6+/-6.8h), non-lactating (23.7+/-15.8 and 25.0+/-6.0 h) and lactating does (22.2+/-10.4 and 24.9+/-4.2h). The accumulative percentage of does in estrus during the first 36 h after sponge removal was 88.1%. The correlation between interval to estrus and duration of estrus was r=-0.32 (P<0.001). Endogenous progesterone production is decreased until day 8 or suppressed by MAP on day 9. Conception rate was greater (P<0.01) in lactating (77.8%) than non-lactating (44.4%) but similar (P>0.05) to nulliparous (60.0%) goats. Estrus can be efficiently induced by means of hormonal treatment in goats and acceptable fertility can be obtained regardless of animal category.     

The effect of lecirelin (GnRH) dosage on the reproductive performance of nulliparous and lactating rabbit does

The present study attempted to evaluate the effect of different doses of lecirelin intramuscularly administered at the moment of insemination on parameters such as the conception rate, the total number of rabbits per litter, the number of stillborns per litter and the abortion rate in nulliparous and lactating crossbred rabbit does. The experiment was performed with 295 crossbred female rabbits Hyplus strain PS 19 that were housed in a rabbit farm. Six days before insemination, the light-dark cycles were as follows: 16-h light (70 lx and more):8-h dark, and all does were subcutaneously injected with 25 IU of eCG 48 h before insemination. The doses of lecirelin were as follows: 0.05, 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 4.0 microg/doe, and were tested in both nulliparous and lactating female does; the doses were applied at the moment of insemination. The conception rate in nulliparous does ranged significantly from 10.0% (0.05 microg) to 89.5% (1.5 microg). The conception rate in lactating does was the lowest at a dose of 0.05 microg (10.0%), as compared with the doses starting from 0.3 microg, and was confirmed statistically significant. The lowest number of rabbits per litter was found at a lecirelin dose of 0.1 microg (6.64). This finding was statistically significant, as compared with doses equal to or exceeding 0.3 microg. No statistical differences were found for doses ranging from 0.3 to 4.0 microg in nulliparous does (9.06 versus 10.29, respectively). The lowest number of rabbits per litter in lactating does was found at a dose of 0.05 microg (8.28) while the highest number of rabbits was detected at a dose of 4.0 microg (10.73), without statistically significant differences among individual doses. Generally, the number of rabbits per litter in lactating rabbit does was higher than that in nulliparous does (P<0.05). One negative finding is that abortions occurred in lactating does at the intramuscular application of a dose equal to or exceeding 1.5 microg, and in nulliparous does at a dose equal to or exceeding 2.0 microg.     

Preliminary report on induction of estrus with multiple eCG injections in Colored Mohair goats during the anestrus season

This trial was conducted to evaluate the effectiveness of multiple eCG injections in the induction of estrus and pregnancy in Colored Mohair goats during the anestrus season. It was also aimed to determine total dose of eCG required for induction of estrus. Ten multiparous and lactating goats were used. The goats were randomly divided into two groups and treatments were started on May 22. Group eCG (n=5) was treated with eCG intramuscularly for 6 days. Daily dosages of eCG from May 22 to May 27 were 300 IU, 200 IU, 200 IU, 100 IU, 100 IU and 50 IU, respectively. Goats in control group received no treatment. Blood samples were taken from animals in each of the two groups just before and after the beginning of the treatments and serum progesterone concentrations were assayed by RIA. Starting on the fourth day after the first treatments, goats were exposed to fertile bucks twice daily for 30 min to detect standing heat. The estrus goats were allowed to be mated by the bucks. Pregnancies were determined 40 days after mating by real-time ultrasonography. One goat on day 5 and three goats on day 7 exhibited behavioral estrus in eCG group (80%) after the first eCG injection. Three of them (75%) became pregnant. None of the goats in the control group exhibited behavioral estrus. Mean serum progesterone concentrations had prominent elevations indicating ovulation in eCG group, but not in control group, after 20 days from the first treatments. Progesterone concentrations of eCG group were significantly different than those of control group on days 20 and 28 (P<0.05). The results suggest that divided multiple injections of a total 950 IU eCG are effective without progestagen pretreatment in the induction of estrus and obtaining successful pregnancy and live kids in Colored Mohair goats during the anestrus season.     

Effects of equine chorionic gonadotropin and type of ovulatory stimulus in a timed-AI protocol on reproductive responses in dairy cows

The objectives were to evaluate the effects of equine chorionic gonadotropin (eCG) supplementation (with or without eCG) and type of ovulatory stimulus (GnRH or ECP) on ovarian follicular dynamics, luteal function, and pregnancies per AI (P/AI) in Holstein cows receiving timed artificial insemination (TAI). On Day 0, 742 cows in a total of 782 breedings, received 2 mg of estradiol benzoate (EB) and one intravaginal progesterone (P4) insert (CIDR). On Day 8, the CIDR was removed, and all cows were given PGF2α and assigned to one of four treatments in a 2 × 2 factorial arrangement: (1) CG: GnRH 48 h later; (2) CE: ECP; (3) EG: eCG + GnRH 48 h later; (4) EE: eCG + ECP. There were significant interactions for eCG × ovulatory stimulus and eCG × BCS. Cows in the CG group were less likely (28.9% vs. 33.8%; P < 0.05) to become pregnant compared with those in the EG group (odds ratio [OR] = 0.28). There were no differences in P/AI between CE and EE cows (30.9% vs. 29.1%; OR = 0.85; P = 0.56), respectively. Thinner cows not receiving eCG had lower P/AI than thinner cows receiving eCG (15.2% vs. 38.0%; OR = 0.20; P < 0.01). Treatment with eCG tended to increase serum progestesterone concentrations during the diestrus following synchronized ovulation (P < 0.10). However, the treatment used to induce ovulation did not affect CL volume or serum progesterone concentrations. In conclusion, both ECP and GnRH yielded comparable P/AI. However, eCG treatment at CIDR removal increased pregnancy rate in cows induced to ovulate with GnRH and in cows with lower BCS.     

The effect of administering equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG) post artificial insemination on fertility of lactating dairy cows

The objective was to evaluate the effect of equine chorionic gonadotropin (eCG) and hCG post artificial insemination (AI) on fertility of lactating dairy cows. In Experiment 1, cows were either treated with eCG on Day 22 post AI (400 IU; n = 80) or left untreated (n = 84). On Day 29, pregnant cows were either treated with hCG (2500 IU; n = 32) or left untreated (n = 36). Pregnancy and progesterone were evaluated on Days 29 and 45. In Experiment 2, cows (n = 28) were either treated with eCG on Day 22 (n = 13) or left untreated (n = 15) and either treated with hCG on Day 29 (n = 14) or left untreated (n = 14). Blood sampling and ultrasonography were conducted between Days 22 and 45. In Experiment 3, cows were either treated with eCG on Day 22 post AI (n = 229) or left untreated (n = 241). Pregnancy was evaluated on Days 36 and 85. In Experiment 1, eCG on Day 22 increased (P < 0.02) the number of pregnant cows on Day 29 (50.0 vs. 33.3%) and on Day 45, the increase was higher (P < 0.01) in cows with timed AI (41.2 vs. 6.5%) than in cows AI at detected estrus (50.0 vs. 37.8%). Pregnancy losses were reduced by eCG and hCG, but increased in cows that did not receive eCG but were given hCG (P < 0.01). Treatment with hCG tended (P < 0.06) to increase progesterone in control cows, but not in cows treated with eCG. In Experiment 2, hCG increased (P < 0.01) the number of accessory CLs on Day 35 (28.5 vs. 0.0%) and tended (P < 0.07) to increase progesterone. In Experiment 3, eCG increased the number of pregnant cows (P < 0.05) on Days 36 and 85, but only in cows with low body condition (eCG = 45.6 and 43.5%; Control = 22.9 and 22.9%). In conclusion, eCG at 22 days post insemination increased fertility, primarily in cows with low body condition and reduced pregnancy losses when given 7 days before hCG; hCG induced accessory CLs and slightly increased progesterone, but hCG given in the absence of a prior eCG treatment reduced fertility.     

Effects of pregnant mare serum gonadotropin (eCG) on follicle development and granulosa-cell apoptosis in the pig

The effect of eCG on follicular development and granulosa-cell apoptosis in sexually mature and immature gilts and on granulosa-cell apoptosis in vitro were studied. The sexually mature gilts were treated with eCG on Day 11 of the estrous cycle, and effects were analyzed at different times after treatment with untreated animals at corresponding stages of the cycle as controls. Apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), hematoxylin and eosin staining, and DNA ladder. The proportion of apoptotic cells in atretic follicles (39%) was significantly higher (P<0.01) than that in healthy follicles (9%). At 24h after eCG treatment in mature gilts, the total number of follicles visible on the ovarian surface (57 per ovary), the number of small (<3mm) follicles (31.5 per ovary) and the number of medium-sized (3-5mm) follicles (23 per ovary) were significantly higher (P<0.05) than those of control animals (28, 20 and 6.5 per ovary, respectively), and declined gradually thereafter to below the level of control animals. The number of large (>or=5mm) follicles began to show a marked increase at 72h after eCG (8.5 versus 2.5, P<0.05). At 24h after eCG treatment, the proportions of apoptotic cells in small (7.2%) and medium-sized follicles (7.4%) were markedly lower (P<0.01) than those in controls (21.5 and 21%, respectively) and increased gradually thereafter to approach the level in controls. The percentage of apoptotic cells in large follicles (10% at 24h post-eCG) did not change significantly. Before eCG treatment, there were markedly fewer follicles of all types on ovaries of immature gilts than of mature gilts (9 versus 25 per ovary) and the proportion of apoptotic cells in small and medium follicles was high (25 and 34%, respectively). After eCG treatment, the changes in follicle number and proportion of apoptotic cells in the immature gilts followed a similar pattern to that of the mature gilts. Equine chorion gonadotropin inhibited apoptosis of granulosa cells cultured either in vitro or in intact follicles in a dose-dependent manner. Thus, follicular atresia in the pig, as in other animals, was characterized by apoptosis of large numbers of granulosa cells, and eCG promoted follicular development by inhibition of granulosa-cell apoptosis.     

Improvement of follicular development rather than gonadotrophin secretion by thyroxine treatment in infertile immature hypothyroid rdw rats

Despite extensive study of reproductive abnormalities in female hypothyroid animals, little is known of folliculogenesis and gonadotrophin secretion in spontaneously hypothyroid animals, especially in response to exogenous hormone treatment. In this study, follicular development and plasma hormone concentrations in the presence or absence of thyroxine and eCG treatment were investigated in infertile immature spontaneously hypothyroid rdw rats. Administration of thyroxine once a day from day 21 to day 29 after birth resulted in increases in body weight (P < 0.001) and ovary mass on day 30 (P < 0.01). Similar populations of both healthy and atretic antral follicles ranging from 101 to 400 micrometer in diameter were observed in control rdw and normal rats. In rdw rats, thyroxine treatment markedly increased the number of healthy antral uniovular follicles 101-400 or > 550 micrometer in diameter in the absence or presence of eCG, respectively. Combined treatment of thyroxine and eCG in rdw rats also markedly increased the number of healthy antral biovular follicles. Thyroxine treatment did not affect the population of atretic antral follicles, but resulted in decrease in the number of atretic large antral follicles (> 400 microm) in the presence of eCG. Plasma oestradiol concentrations in rdw rats given both thyroxine and eCG were significantly higher than they were in rdw rats given eCG alone (P < 0.001). There were no significant differences in plasma FSH concentrations on day 28 between rdw (10.7 +/- 1.6 ng ml(-1)) and normal rats (12.0 +/- 1.4 ng ml(-1); P > 0. 05). Although there were no significant differences in plasma LH concentrations between control rdw (1.9 +/- 0.1 ng ml(-1)) and normal rats on day 30 (1.8 +/- 0.1 ng ml(-1); P > 0.05), eCG treatment increased plasma LH to a peak concentration 52 h after injection in normal (24.9 +/- 2.4 ng ml(-1)) but not in rdw rats treated with thyroxine (4.8 +/- 0.3 ng ml(-1); P < 0.05). In conclusion, the results of the present study indicate that thyroxine treatment improves follicular development but does not rescue the defect of the preovulatory surge of LH in eCG-primed rdw rats.     

Is an ovulation-inducing factor (OIF) present in the seminal plasma of rabbits?

The objectives of this study were (1) to determine the effect of rabbit seminal plasma on LH secretion and ovulation using the llama animal model as an in vivo ovulation bioassay and (2) to determine the effect of llama or rabbit seminal plasma on ovulation induction in the rabbit model. In Experiment 1, llamas with a growing follicle ≥8mm in diameter were assigned randomly to one of three groups (n=5 per group) and given an intramuscular dose of 1mL of: (a) llama seminal plasma, (b) rabbit seminal plasma, or (c) phosphate buffered saline (PBS; negative control). Blood samples for LH measurement were taken every 15 min from 1.5 h before to 8 h after treatment (Day 0: starting of treatment). Llamas were examined by ultrasonography every 12h from treatment to ovulation, and then every other day until Day 16 after treatment to evaluate corpus luteum (CL) development. Blood samples for progesterone measurement were taken every other day from Day 0 to Day 16. Ovulation was detected in 4 of 5, 5 of 5, and 0 of 0 llamas treated with llama or rabbit seminal plasma and PBS, respectively (P<0.001). After treatment, plasma LH concentration increased and decreased (P<0.01) in the llama and rabbit seminal plasma group but not in the PBS-treated group. No differences were observed on CL development (P≥0.3) and progesterone secretion (P>0.05) between both seminal plasma treated groups. In Experiment 2, receptive female rabbits (n=5-7 per group) were given an intramuscular dose of: (a) 0.5, (b) 1.0 and (c) 2.0mL of either rabbit or llama seminal plasma, (d) 0.5mL PBS (negative control), or (e) 25μg of gonadoreline acetate (GnRH; positive control). Does were submitted to laparotomy 24-36 h after treatment to determine the ovulatory response and the presence of antral and hemorrhagic anovulatory follicles. Ovulation sites (7.0±0.6) were only detected in GnRH-treated does (P<0.01). There was an increase (P<0.01), in the total number of follicles (antral plus hemorraghic follicles) in those females treated with 1mL of rabbit seminal plasma and there was a tendency (P=0.08) for more hemorrhagic anovulatory follicles in does treated with 1.0 and 2.0mL of either rabbit or llama seminal plasma. Results document the presence of OIF in the seminal plasma of rabbits. The differential ovulatory response between species, however, requires further investigation.