The GnRH antagonist acyline prevented ovulation, but did not affect ovarian follicular development or gestational corpora lutea in the domestic cat

Two experiments were conducted to investigate the effects of the GnRH antagonist acyline (330 μg/kg, given sc) on ovarian follicular development and ovulation, as well as on pregnancy maintenance in domestic cats. In the first experiment, seven queens in proestrus (total of 24 proestrus periods), were randomly assigned to treatment with either acyline (ACY; n = 17) or a placebo (PLC; n = 7). All queens were mated with a fertile tomcat. In the ACY and PLC groups, cessation of estrus occurred (mean ± SEM) 7.0 ± 1.3 and 7.0 ± 1.7 d after treatment (P > 0.1), ovulation occurred in 2 of 17 and all seven estrus periods (P < 0.05), and pregnancy rates were 1 of 16 and 7 of 7 (P < 0.05), respectively. In the ACY and PLC groups, intervals from treatment to the onset of the ensuing proestrus were 18.4 ± 1.7 and 120 ± 17.2 d. In the second experiment, 14 pregnant queens were randomly allocated, according to their mating date, to treatment with acyline in early pregnancy (from 20 to 25 d, n = 3), mid pregnancy (from 26 to 45 d; n = 4), late pregnancy (> 45 d; n = 3), or injection of a placebo in early (n = 1), mid (n = 2), or late pregnancy (n = 1). Ultrasonographic assessments of the uterus were done every second day for 2 wk post treatment, and serum progesterone (P₄) concentrations were determined before treatment, and at 7 and 14 d after treatment. No pregnancies were prematurely terminated and post-treatment P₄ concentrations did not differ among treatment groups (P > 0.1). In conclusion, in the domestic cat, GnRH withdrawal by acyline prevented ovulation when given in early follicular phase (proestrus), but did not significantly affect luteal function during pregnancy.     

Effect of a GnRH antagonist on GnRH agonist-implanted anestrous bitches

Various combinations of gonadotropin-releasing hormone (GnRH) antagonists and long-acting GnRH agonists have been assessed in several species to prevent the “flare-up” effect that agonists cause on the pituitary-gonadal axis. To determine the effect of a single administration of the GnRH antagonist acyline in anestrous GnRH agonist-implanted domestic bitches, 19 dogs (canis familiaris) were randomly assigned to receive either 10 mg sc deslorelin acetate (DA; n = 6) or DA combined with 330 μg/kg sc acyline within the first 48 h (DA&ACY; n = 13). These bitches were examined daily for detection of posttreatment flare-up, manifested as an estrous response during the month after treatment. In the DA and DA&ACY groups, an estrous response was detected in 6 of 6 and 9 of 12 (P < 0.5) of the bitches, starting 5.3 ± 1.3 and 10.1 ± 1.8 d (mean ± SEM, P = 0.5), respectively, after treatment. Based on serum progesterone concentrations, ovulation occurred in 6 of 6 and 5 of 9 of these bitches (P = 0.1). None of the dogs had any local or systemic side effects related to the treatments. In five DA and six DA&ACY bitches that could be followed up after the trial, interestrus intervals were 385 ± 22.5 and 330 ± 69.1 d, respectively (P > 0.1). It was concluded that the current antagonist protocol prevented initial ovarian stimulation in one quarter of the treated dogs, whereas the stimulation period was postponed and ovulation was inhibited in approximately half of the remainder.     

Efficiency of estrous synchronization in tropical sheep by combining short-interval cloprostenol-based protocols and “male effect”

This study assessed the efficacy of a protocol combining short-interval cloprostenol-based protocols and “male effect” for estrous synchronization in hair sheep. In Experiment 1, 24 ewes were randomly assigned to three groups (n = 8) and treated with cloprostenol on Days 3, 5 and 7 after ovulation, respectively. Estradiol secretion during the follicular phase was similar among groups. Onset of estrus (P < 0.001) and the timing of maximum LH concentration (P < 0.01) were earlier in group D3 than in D5 and D7 groups. During the subsequent cycle, the number and size of corpora lutea were higher (P < 0.05) in ewes of the groups D3 (1.9 ± 0.3 and 115.1 ± 14.3 mm²) and D5 (1.8 ± 0.2 and 100.2 ± 11.2 mm²) than in group D7 (1.3 ± 0.2 and 75.6 ± 6.4 mm²) group. In Experiment 2, 24 ewes were treated with two cloprostenol injections (7 days apart). Twelve ewes were exposed to “male effect” previous to an isolation period (ME group), whereas the remaining ewes were controls without male exposure (CTR group). Male effect induced earlier preovulatory LH surge (P < 0.05) and ovulation (P < 0.001) than CTR group. In Experiment 3, the estrus was synchronized in 68 ewes. Nineteen of them (group FGA) were treated using intravaginal sponges impregnated with fluorogestone acetate for 12 days and inseminated at 55 h. Forty-nine females (group ME) were treated like ME group. Twenty-four (ME48 group) and 25 ewes (ME55 group) were inseminated at 48 and 55 h after treatment, respectively. The fertility rate was numerically higher in ME48 than ME55 and FGA groups (62.5, 44.0 and 47.4%, respectively). In conclusions, the combined use of short-interval cloprostenol treatment and “male effect” may be an adequate alternative for synchronizing estrus and applying artificial insemination in hair sheep throughout the entire year.     

Pharmacokinetics of eCG and induction of fertile estrus in bitches using eCG followed by hCG

The aim was to design a protocol combining eCG followed by hCG for estrus induction in the bitch. In Experiment 1, three ovariohysterectomized bitches received 10 000 IU of eCG iv, and 15 days later 10 000 IU of eCG im. Blood samples were taken up to 144 h after each injection to measure eCG concentrations. In Experiment 2, 25 healthy, intact late anestrous bitches were assigned to one of five doses of eCG (5, 10, 15, 20, 44, or 50 IU/kg eCG im; [TRT5-TRT50]). Sexual behavior (SB), clinical signs of estrus (CSE) and vaginal cytology (VC) samples were obtained and scored before eCG administration and every other day until onset of estrus, or for 14 days. In Experiment 3, intact late anestrous bitches were assigned to a treatment group (TRT; n = 16) and received eCG (50 IU/kg im) followed by hCG (500 IU im) 7 days later; or to a placebo group (PLA; n = 8) where they received 1 mL saline solution im. All bitches that were induced in estrus were mated or AI with fresh semen. In Experiment 1, maximum observed concentration (C_max) eCG were similar between im and iv routes (6.1 ± 0.9 vs. 8.6 ± 0.5 IU/mL, P > 0.08), whereas time for maximum observed concentration (T_max.) was longer for im compared to iv routes (17.5 ± 0.5 vs. 11.6 ± 0.3 h, P < 0.01). The area under the curve (AUC) was similar for im and iv routes (P > 0.48), and eCG was detectable in serum for at least 144 h for both routes. In Experiment 2, 3 days or 3 to 5 days after treatment, all bitches in TRT50 had higher scores compared to TRT5-44 animals (P < 0.01). In TRT50, the mean interval from treatment to estrus was 4.0 ± 0.4 days. In Experiment 3, the mean interval from treatment to estrus was shorter in the TRT group compared to the PLA group (4.1 ± 3.3 vs. 68.5 ± 4.4 days, P < 0.01). The previous interestrus interval was similar for TRT and PLA groups (199.6 ± 7.2 vs. 197.5 ± 10.2 days), but the new interestrus interval was shorter for the TRT compared to the PLA group (164.0 ± 7.2 vs. 212.2 ± 10.2 days; treatment by interval interaction, P < 0.007). Serum P₄ concentrations increased on the first day of cytologic diestrus after treatment in bitches in TRT (0.7 ± 0.3 vs. 22.8 ± 4.2 ng/mL; P < 0.01); but did not change in PLA (P > 0.84). Ninety-four percent of animals were bred (15/16; AI, n = 7; natural mating, n = 8), and 80% (12/15) became pregnant. None of the bitches had any side effects from the eCG and hCG therapy. We concluded that 50 IU/kg of eCG combined 7 days later with 500 IU of hCG was effective to induce normal and fertile estrus in bitches at 164 days post estrus, with an 80% pregnancy rate, with no side effects, and with a reduction of 48 days of the interestrus interval.     

Endocrine effects of the GnRH antagonist, acyline, in domestic dogs

Gonadotrophin-releasing hormone (GnRH) antagonists may have a future role in the control of canine reproductive function. In this study, the effects of a single dose of the potent GnRH antagonist, acyline, on serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone (T) were evaluated in male dogs. Blood samples were drawn before (Day −1) and after (30, 60, and 90 min, 3, 6, 9, 12, and 24 h, and 3, 6, 9, 14, 22, and 29 d) treatment with acyline (330 μg/kg, sc); serum concentrations of FSH, LH, and T varied throughout the study period (P < 0.01, <0.05, and <0.01, respectively). Gonadotrophins decreased below pretreatment concentrations 60 min after injection, whereas T took 90 min to decrease below baseline (P > 0.05). Follicle-stimulating hormone, LH and T decreased until Day 9, when they reached their nadir at 2.0 ±1.1 ng/mL (P < 0.01), 1.2 ± 0.2 ng/mL (P > 0.05), and 0.5 ± 0.2 ng/mL (P < 0.05), respectively. Both gonadotrophins and T began increasing on Day 14 after treatment, although FSH and T serum concentrations still remained below baseline on that day (P > 0.05). Follicle-stimulating hormone and T rebounded above baseline on Day 29, whereas LH reached concentrations were similar to baseline at this time (P > 0.05). No local or systemic side effects were detected in any dog following acyline treatment. In conclusion, a single acyline treatment safely and reversibly decreased serum gonadotrophin and T concentrations in dogs for 9 d.     

The use of digital infrared thermal imaging to detect estrus in gilts

Yorkshire/Landrace crossbred gilts (N = 32) were evaluated using digital infrared thermal imaging (DITI) to discriminate between estrus and diestrus phases of the porcine estrous cycle. Gilts (N = 32) were part of an ongoing reproductive efficiency study involving the use of raw soybean (RSB; N = 15) versus soybean meal (SBM; N = 17) as a source of dietary protein. Gilts were monitored daily for signs of estrus using a teaser boar. Thermal images of vulva surface temperatures (TEMP) were recorded at standing estrus and diestrus. Measurements for analysis included minimum (MIN), maximum (MAX), mean (AVG), and standard deviation (SD) of temperature gradients. At imaging, ambient (AMB) and rectal temperatures (RT) were recorded, and blood samples taken for serum progesterone (P₄) concentration analysis (by RIA) to confirm stage of cycle. Mean serum progesterone values at estrus and diestrus were (mean ± SD) 1.0 ± 0.1 and 10.9 ± 0.8 ng/mL, respectively. Vulva MIN, MAX, and AVG thermal images were positively correlated with one another (P < 0.01), and were positively correlated with ambient temperature (P < 0.01). Vulva MAX and AVG thermal temperatures were greater (P < 0.05) at estrus than at diestrus (36.6 ± 0.2 °C and 33.4 ± 0.3 °C vs. 35.6 ± 0.3 °C and 31.8 ± 0.6 °C, respectively), whereas MIN and SD had no differences (P > 0.05) between stages of the cycle. No differences (P > 0.05) in RT were detected between stages and RT was not significantly correlated with vulva thermal images. Diet had no significant effect on RT or vulva temperature.     

Comparison of long-term CIDR-based protocols to synchronize estrus in beef heifers

Two experiments evaluated long-term controlled internal drug release (CIDR) insert-based protocols to synchronize estrus and compare differences in their potential ability to facilitate fixed-time artificial insemination (FTAI) in beef heifers. In Experiment 1 estrous cycling heifers (n = 85) were assigned to one of two treatments by age and body weight (BW). Heifers with T1 received a CIDR from days 0 to 14, gonadotropin releasing hormone (GnRH) on day 23, and prostaglandin F_2α (PG) on day 30. Heifers with T2 received a CIDR from days 2 to 16, GnRH on day 23, and PG on day 30. Ovaries were evaluated by ultrasonography on days 23 and 25 to determine ovulatory response to GnRH. In Experiment 2 heifers (n = 353) were assigned within reproductive tract scores by age and BW to one of four treatments. Heifers in T1 and T2 received the same treatments described in Experiment 1. Heifers in T3 and T4 received the same treatments as T1 and T2, respectively, minus the addition of GnRH. In Experiments 1 and 2, heifers were fitted with HeatWatch transmitters for estrous detection and AI was performed 12 h after estrus. In Experiment 1 heifers assigned to T1 had larger dominant follicles at GnRH compared to T2 (P < 0.01) but response to GnRH, estrous response after PG, mean interval to estrus, and variance for interval to estrus after PG did not differ (P > 0.10). AI conception and final pregnancy rate were similar (P > 0.50). In Experiment 2 estrous response after PG did not differ (P > 0.70). Differences in mean interval to estrus and variance for interval to estrus (P < 0.05) differed based on the three-way interaction of treatment length, GnRH, and estrous cyclicity status. AI conception and final pregnancy rates were similar (P > 0.10). In summary, the greater estrous response following PG and resulting AI conception and final pregnancy rates reported for heifers assigned to the two treatments in Experiment 1 and among the four treatments in Experiment 2 suggest that each of these long-term CIDR-based protocols was effective in synchronizing estrus in prepubertal and estrous cycling beef heifers. However, the three-way interaction involving treatment length, GnRH, and estrous cyclicity status in Experiment 2 clearly suggests that further evaluation of long-term CIDR-based protocols is required with and without the addition of GnRH and on the basis of estrous cyclicity status to determine the efficacy of these protocols for use in facilitating FTAI.     

Corpus luteum function following single and double ovulation during estrous cycle in Sanjabi ewes

This study compared the effect of double and single ovulation on serum progesterone concentrations and luteal characteristics in Sanjabi ewes at different days of the estrous cycle. The estrous cycles of 197 Sanjabi ewes were synchronized by a 12-day treatment with intravaginal sponges (Chronogest^®). Estrus was detected in 144 ewes 27–39 h after sponge removal. Daily blood samples were taken every morning and analyzed for serum progesterone (P4). Ewes were then transported to a local abattoir, where nine ewes were slaughtered on each experimental day (days 1–16 after estrus) for ovary collection. The ovarian follicles were measured and categorized by size (very small <2 mm; small 2–3.5 mm; medium 3.5–5 mm; large >5 mm). On each slaughter day, the number of corpora lutea per ewe was classified as single and double ovulation. The results show that the effect of dominant follicles was less during the mid-luteal phase. Ovulation rate of right, left and both ovaries were (54.9%), (23.6%) and (21.5%), respectively. The incidence of double ovulations was 40.2%. In the case of ewes exhibiting double ovulation, 46.6% occurred unilateral (ewes exhibited both ovulations on the right ovary); whereas 53.4% occurred bilateral (ewes exhibited ovulations on the right and left ovaries). Unilateral double ovulation was not observed in the left ovary. The right ovary appeared to play a significantly greater role in ewes showing single and double ovulations than the left ovary (P < 0.05). Serum progesterone concentration showed minimum and maximum levels of 0.29 ± 0.15 and 5.51 ± 0.75 ng/ml on days 16 and 11 post-estrous, respectively (P < 0.001). The mean volume of individual corpus lutea in ewes with single ovulations was significantly higher than in ewes with double ovulations (P < 0.01). However, the total volume of corpus lutea in ewes with single ovulation was significantly lower than in ewes with double ovulations in some days of estrous cycle (P < 0.01). The serum progesterone concentration was significantly higher in double than single ovulating animals on days 1–16 of the estrous cycle (P < 0.001). These results indicated a relatively high incidence of double ovulation in ewes associated with increasing total luteal volume and high circulating concentrations of progesterone.     

Calcium, parathyroid hormone, oxytocin and pH profiles in the whelping bitch

Despite the high prevalence of primary uterine inertia in whelping bitches, the underlying pathogenesis remains unclear. The objectives were to i) determine serum concentrations of total calcium, ionized calcium (iCa), parathyroid hormone (PTH), and blood pH in normally whelping bitches throughout the peri-parturient period; and ii) investigate relationships among iCa, PTH, and acid-base status, and the role that they and oxytocin may have in the underlying pathogenesis of canine uterine inertia. Bitches were randomly selected from a population of German Shepherd Dog bitches with a history of uncomplicated parturition (Group 1; n = 10), and from a population of Labrador bitches with a clinical history of an increased incidence of uterine inertia and stillbirths (Group 2; n = 20). Jugular blood samples were collected daily from -4 d to the onset of whelping (t = 0 h), and then every 4 h until the last pup was born. Overall, bitches from Group 2 had higher mean ± SEM serum concentrations of PTH (4.72 ± 2.45 pmol/L, P < 0.001), lower iCa (1.31 ± 0.08 pmol/L, P < 0.05), and higher venous pH (7.41 ± 0.03, P < 0.005) than bitches from Group 1 (2.9 ± 1.44 pmol/L, 1.38 ± 0.06 mmol/L, and 7.33 ± 0.02, respectively) during the periparturient period. However, there was no significant difference between Groups 1 and 2 for serum oxytocin concentrations during the periparturient period (45.5 ± 40 and 65.5 ± 82 pg/mL). We inferred that low iCa resulting from a rising pH and decreasing PTH during the periparturient period may have contributed to decreased uterine contractility and increased risk of stillbirths. Therefore, manipulating the cationic/anionic difference in diets of pregnant bitches, similar to the bovine model for hypocalcamia, may reduce the incidence of stillbirths in the bitch.     

Estrus detection and estrus characteristics in housed and pastured Holstein-Friesian cows

This study compared three methods of estrus detection and characteristics of standing estrus between dairy cows kept in cubicle housing and fed a total mixed ration diet (HOUSED treatment) and those kept at pasture with concentrate ration supplementation (PASTURE treatment). The 23 spring-calved Holstein-Friesians in each treatment were monitored by three estrus detection methods simultaneously—visual observations, tail paint and radiotelemetry (HeatWatch)—for 9 wk. Milk progesterone profiles were used to determine the dates of true standing estrus events. All three detection methods had a higher efficiency of estrus detection in the PASTURE treatment than in the HOUSED treatment (P < 0.001), but there was no difference in the accuracy of estrus detection between the two treatments (P > 0.05). Within each treatment there was no difference between the efficiency and accuracy of the three methods (P > 0.05). HeatWatch was as efficient as visual observations at detecting standing estrus events. However, during visual observation sessions all occasions when animals were observed standing to be mounted were not recorded by HeatWatch. More cows expressed sub-estrus events and fewer expressed standing estrus events in the HOUSED than in the PASTURE treatment (P < 0.05). The interval between parturition and the second standing estrus was longer in the HOUSED treatment than in the PASTURE treatment (P < 0.05). All three detection methods were much less effective in the HOUSED than in the PASTURE treatment. This is because all of the detection methods tested relied solely on standing to be mounted and this was reduced in the HOUSED cows. Alternative approaches to estrus detection are needed for cows kept indoors on concrete.     

Immunization against inhibin enhances both embryo quantity and quality in Holstein heifers after superovulation and insemination with sex-sorted semen

The objective was to investigate the feasibility of improving embryo yield in superovulated cows following insemination with sex-sorted semen by prior immunization against inhibin. Twenty-eight heifers were allocated into three groups: High (n = 10), Low (n = 10), and Control (n = 8). The High group received one primary (1 mg) and two booster (0.5 mg) vaccinations (28-d intervals) with a recombinant inhibin α-subunit in 1 mL of white oil adjuvant, whereas the Low group received half that dose, and the Control group received only adjuvant. After the last immunization, all heifers underwent a standard superovulation treatment (decreasing doses of pFSH for 4 d), followed by two AI with 2 × 10⁶ sex-sorted semen after the onset of estrus. Inhibin-immunized heifers had higher (P < 0.01) plasma antibody titres, and an earlier onset of estrus (P < 0.05) than Control heifers. The total number of embryo/ova, transferable, and grade 1 embryos in the High group (15.4 ± 1.9, 5.7 ± 0.7, and 3.8 ± 1.0, respectively) was significantly greater than that of the Control group (9.1 ± 1.2, 3.1 ± 0.5, and 0.6 ± 0.2), but was intermediate (P > 0.05) in the Low group (13.0 ± 2.3, 4.4 ± 0.7, and 1.2 ± 0.3). There were no significant differences among groups in number of unfertilized ova and degenerated embryos. The High group also had higher (P > 0.05) plasma progesterone concentrations on the day of embryo collection. In conclusion, immunization against inhibin improved both embryo quantity and quality following superovulation and insemination with sex-sorted semen.     

Epidermal growth factor, transforming growth factor-α, and epidermal growth factor receptor expression and localization in the canine endometrium during the estrous cycle and in bitches with pyometra

Gene expression and immunohistochemical localization of epidermal growth factor (EGF), transforming growth factor-α (TGF-α), and epidermal growth factor receptor (EGF-R) were compared between the endometrium of bitches (Canis familiaris) with pyometra accompanied by cystic endometrial hyperplasia (CEH) and that of healthy bitches at similar stages of the estrous cycle. In normal bitches, endometrial TGF-α mRNA levels were highest at proestrus and gradually decreased as the cycle progressed to anestrus. Epidermal growth factor receptor mRNA levels were not significantly affected by the stage of the estrous cycle. Epidermal growth factor mRNA levels were higher at Day 35 of diestrus than at other stages of the estrous cycle (P < 0.05). In bitches with pyometra, endometrial TGF-α and EGF-R mRNA levels did not differ significantly from those at diestrus in normal bitches, but EGF mRNA levels were lower than those at Day 35 of diestrus in normal bitches (P < 0.05). In normal bitches, positive immunohistochemical staining for TGF-α, EGF, and EGF-R was mainly present in the glandular and luminal epithelial cells of the endometrium. In contrast, in bitches with pyometra, immunoreactivity for EGF was clearly present in endometrial stromal cells. Inflammatory cells that had infiltrated the endometrial stroma stained strongly for TGF-α and EGF-R. Luminal and glandular epithelial cells also stained positive for EGF-R. In conclusion, expression of TGF-α by inflammatory cells and a low level of expression and differential localization of EGF may be involved in aberrant growth of endometrial glands and development of CEH.     

Ovarian follicular dynamics and plasma steroid concentrations are not significantly different in ewes given intravaginal sponges containing either 20 or 40 mg of fluorogestone acetate

Although various progestagens are often used to induce and synchronize estrus and ovulation in ruminants, concerns regarding residues are the impetus to develop alternative approaches, including reduced doses of progestagens. Therefore, the objective was to determine whether ovarian function was affected by halving the dose of fluorogestone acetate in intravaginal sponges for synchronizing ovulation in sheep during the physiologic breeding season. Twenty Manchega ewes, 4-6-year-old, were randomly allocated to receive an intravaginal sponge containing either 20 mg (P20, n = 10) or 40 mg of fluorogestone acetate (P40, n = 10). Cloprostenol (125 μg) was given at sponge insertion, and all sponges were removed after 6 d. Ovarian follicular dynamics (monitored by daily ultrasonography) and other aspects of ovarian function did not differ significantly between the two groups. Ovulatory follicles (OF) grew at a similar growth rate (r = 0.62; P < 0.001), with comparable initial and maximum diameters (4.2 ± 0.4 to 6.0 ± 0.3 mm in P20 vs. 4.6 ± 0.6 to 5.7 ± 0.2 mm in P40, mean ± S.E.M.). Plasma estradiol concentrations (determined once daily) increased linearly during the 72 h interval after sponge removal (1.3 ± 0.1 to 3.3 ± 0.1 pg/mL for P20, P < 0.005 and 1.4 ± 0.1 to 3.1 ± 0.2 pg/mL for P40, P < 0.005). Ten days after sponge removal, ovulation rates (1.2 ± 0.2 for P20 and 1.4 ± 0.3 for P40), and plasma progesterone concentrations (3.8 ± 0.35 ng/mL for P20 and 3.9 ± 0.38 ng/mL for P40) were similar. In conclusion, reducing the dose of fluorogestone acetate from 40 to 20 mg did not affect significantly ovarian follicular dynamics or other aspects of ovarian function.     

The reproductive performance of female Formosan sambar deer (Cervus unicolor swinhoei) in semi-domesticated herds

This study documented the reproductive performance of 210 adult female Formosan sambar deer (FSD, Cervus unicolor swinhoei) from four semi-domesticated deer herds in Taiwan. An extensive analysis of 525 reproductive records from 2000 to 2008, including the conditions of estrus, gestation, and parturition was conducted. The mean ± S.E.M. lengths of the estrous cycle, gestation, and fawning interval were 18.2 ± 0.5 d (n = 56), 258.6 ± 0.3 d (n = 160), and 369.9 ± 2.3 d (n = 122), respectively. Hand breeding was performed between June and December (n = 494), with the majority (93.1%) occurring between July and October (P < 0.05). Fawning occurred from February to September (n = 318), and most frequently (83.0%) between April and June (P < 0.05). Pregnancy rate per mating in FSD hinds was 64.4%. There was a 1.3:1 male-to-female ratio at birth (P < 0.05) among 320 fawns, and only two cases of twinning (0.63%). The postnatal mortality rate was 6.6% (21/320), and the mortality rate in fawns before weaning did not exceed 8% on any farm. Fecundity was enhanced by high pregnancy rates and high offspring survival rates. This study provides baseline information on reproductive performance of FSD, which should be valuable to veterinarians and deer industry personnel for management of FSD on farms in subtropical countries.     

Administration of sulpiride or domperidone for advancing the first ovulation in deep anestrous mares

Since results with using sulpiride and domperidone are conflicting and since both have not been tested at the same time, the aim of this study was to compare the efficacy of these substances for the induction of ovulation in deep anestrous mares in the same experimental conditions and to determine their fertility after artificial insemination (AI) at the induced estrus. Twenty-six non-pregnant, non-lactating standardbred anestrous mares were randomly assigned to three groups and treated daily for 25 days (from February 3rd to February 28th) with either sulpiride (1 mg/kg of body weight im SID, n = 10), or domperidone (1 mg/kg po SID, n = 10); 6 animals were used as control. The beginning of the transition period and the first ovulation were hastened in sulpiride (16.4 ± 0.8 days) but not in domperidone (46.0 ± 3.3 days) treated mares (P < 0.05). The diameter of the largest follicle was affected by treatment, time and interaction of treatment-by-day (P < 0.05) and significantly increased in the sulpiride group (P < 0.05). Although a main effect of treatment on plasma LH concentration was not observed (P = 0.06), time and interaction of treatment-by-day were statistically significant (P < 0.05). The interval from the beginning of treatment to first ovulation was shorter (P < 0.05) in the sulpiride group (36.9 ± 2.5 days) than in the domperidone (74.7 ± 3.3 days) and control (81.4 ± 3.1) groups. The establishment of pregnancy was significantly (P < 0.05) hastened in sulpiride (61.0 ± 35.2 days) but not in domperidone (83.0 ± 44.0 days) treated mares. Treated mares not pregnant after the first AI, showed normal estrous cycles with regular interovulatory intervals (P > 0.05). It was concluded that sulpiride is effective in advancing the beginning of transition period and the first ovulation whereas domperidone is successful only in some mares.     

Suppression of estrus in cats with melatonin implants

The objective of this study was to assess the efficacy of a subcutaneous melatonin implant to suppress estrus in queens (felis catus). The hypothesis was that this implant would temporarily and reversibly suppress estrus in queens without producing any clinically detectable side effects. Fourteen adult queens were maintained in cages under artificial illumination (14 h light:10 h dark) for 45 d and then randomly assigned to one of two treatments. At interestrus, queens received a single subcutaneous melatonin implant (18 mg; Melovine [CEVA Sante Animal, Libourne, France]; MEL: n = 9), or a single subcutaneous placebo implant without melatonin (0 mg; PLA; n = 5). At the next estrus, all queens received a second MEL (n = 9) or PLA (n = 5) implant. Blood samples were taken when queens displayed estrous signs and during interestrus to measure estradiol (E₂) and progesterone (P₄), respectively, by radioimmunoassay. There were no significant differences in duration of the interestrus interval in PLA cats, regardless of whether the implants were placed during interestrus or estrus (6.0 ± 9.7 d vs. 6.0 ± 9.7 d, respectively; least square means [LSM] ± SEM). However, when MEL implants were placed during interestrus, the duration of interestrus was approximately twice as long as that occurring when MEL implants were placed during estrus (113.3 ± 6.1 d vs. 61.1 ± 6.8 d, respectively; P < 0.01). Serum E₂ and P₄ concentrations were similar in queens with PLA and MEL implants and in queens that received implants in estrus and interestrus. In conclusion, a subcutaneous MEL implant effectively and reversibly suppressed estrus in queens for approximately 2 to 4 mo with no clinically detectable side effects.     

Ovarian antral follicular dynamics in sheep revisited: Comparison among estrous cycles with three or four follicular waves

In this study, the characteristics of ovarian follicular waves and patterns of serum concentrations of follicle-stimulating hormone (FSH), estradiol, and progesterone were compared between cycles with three (n = 9) or four (n = 10) follicular waves in Western White Face (WWF) ewes (Ovis aries). Transrectal ultrasonography and blood sampling were performed daily during one cycle. Estrous cycles were 17.11 ± 0.3 and 17.20 ± 0.2 d long in cycles with three and four waves, respectively (P > 0.05). The first interwave interval and the interval from the emergence of the final wave to the day of ovulation were longer in cycles with three waves compared with those in cycles with four waves (P < 0.05). The growth phase (5.1 ± 0.5 vs. 3.1 ± 0.4 d) and life span (5.67 ± 0.3 vs. 4.3 ± 0.3 d) of the largest follicle growing in the last or ovulatory wave was longer in cycles with three waves compared with that in cycles with four waves (P < 0.05). The maximum diameter of the largest follicle was greater in the first wave and the ovulatory wave compared with that in other waves of the cycle (P < 0.05). The regression phase of the largest follicle growing in the first wave was longer in cycles with three waves compared with that in cycles with four waves (4.44 ± 0.4 vs. 3.4 ± 0.4 d; P < 0.05). The length of the life span, regression phase, and, although not significant in every case, FSH peak concentration and amplitude decreased across the cycle (P < 0.05). We concluded that estrous cycles with three or four follicular waves were confined within the same length of cycle in WWF ewes. In this study, there were no apparent endocrine or follicular characteristics that could explain the regulation of the different number of follicular waves (three vs. four) during cycles of similar length.     

Fixed-time AI pregnancy rate following insemination with frozen-thawed or fresh-extended semen in progesterone supplemented CO-Synch protocol in beef cows

The objective of this study was to compare fixed-time AI pregnancy rate in Angus crossbred beef cows inseminated with frozen-thawed or fresh-extended semen. Two ejaculates from each of two Angus bulls were collected by artificial vagina and pooled for each bull. The pooled semen from each bull was divided into two aliquots; Aliquot 1 was extended using Caprogen^® (LIC, Hamilton, New Zealand) to a concentration of 3 × 10⁶ sperm/straw and Aliquot 2 was extended using egg-yolk-glycerol extender to a concentration of 20 × 10⁶ sperm/straw. Semen extended with Caprogen^® was maintained at ambient temperature and semen extended with egg-yolk-glycerol extender was frozen and maintained at −196 °C until insemination. In each of two breeding seasons (Fall 2007 and Spring 2008), Angus-crossbeef cows (N = 1455) at 12 locations were randomly assigned within location to semen type [Fresh (N = 736) vs. Frozen (N = 719)] and sire [1 (N = 731) vs. 2 (N = 724)]. All cows were synchronized with 100 μg of GnRH im and a progesterone Controlled Internal Drug Release insert (CIDR) on Day 0, and on Day 7, 25 mg of PGF2_α im and CIDR removal. All cows received 100 μg of GnRH im and were inseminated at a fixed-time on Day 10, 66 h after CIDR removal. Timed-AI pregnancy rates were influenced by season (P < 0.05), cows detected in estrus prior to and at AI (P < 0.001), and dam age (P < 0.01). Pregnancy rates were not affected by semen type (Fresh = 51.5% vs. Frozen = 50.4%; P = 0.66) and there were no significant interactions of semen type by estrus expression, semen type by sire, or semen type by season (P > 0.1). In conclusion, commercial beef cows inseminated with fresh-extended semen (3 × 10⁶ sperm/straw) yielded comparable pregnancy rates to conventional frozen-thawed semen in a progesterone supplemented, CO-Synch fixed-time AI synchronization protocol and may provide an alternate to frozen semen for more efficient utilization of superior genetics.     

The effect of hormone treatments (hCG and cloprostenol) and season on the incidence of hemorrhagic anovulatory follicles in the mare: A field study

The association between use of hormone treatments to induce estrus and ovulation and the incidence of hemorrhagic anovulatory follicles (HAFs) was studied in a mixed population of mares (Equus caballus) during two breeding seasons in a commercial breeding clinic. Mares treated with cloprostenol (CLO) were more likely to develop HAFs than were mares with spontaneous cycles (P < 0.001) or those treated with human chorionic gonadotropin alone (P = 0.08). There was no significant effect of season on the incidence of HAFs. The mean (±SEM) interval from CLO treatment to beginning of HAF development was 6.1 ± 0.5 d. Age of mares with HAF cycles was not different (12 ± 1.3 yr; P > 0.05) from that of mares with ovulatory cycles (10.5 ± 1.5 yr).     

Estrus induction in Beagle bitches with the GnRH-agonist implant containing 4.7 mg Deslorelin

Estrogens, gonadotrophins, dopamine agonists, gonadotrophin releasing hormone (GnRH) and its agonists have been used for estrus induction in bitches. A long acting GnRH agonist implant (4.7 mg Deslorelin; Suprelorin®, Virbac) with a continuous hormone release has been developed for suppression of sexual function in male dogs. In this study we administered the Deslorelin implant placed subcutaneously on the medial side of the leg to induce estrus in 11 anestrous Beagle bitches (group A). 6 Beagle bitches (group B) with a spontaneous estrous cycle were used as controls. The progress of pre-estrus and estrus was documented by behaviour, vaginoscopy, vaginal cytology and progesterone concentration. In group A a bloody vaginal discharge was detected on average 4.8 (range 3-10) d after application of the implant. At this moment implants were removed under local anaesthesia. Pre-estrus lasted for an average of 4.5 d (range 1-12). All bitches showed estrous signs and ovulated. The ovulation took place on day 8.2 (range 4-15) after start of pre-estrus. In group B pre-estrus lasted for 7.5 d (range 6-9), and the mean day of ovulation was day 11 (range 9-13). As a consequence of ovulation, progesterone serum concentrations exceeded 10 ng/ml during or after the time of ovulation in all bitches. All bitches were bred to fertile Beagle stud dogs or inseminated with fresh semen intravaginally. Between days nine and 19 after ovulation all bitches underwent ovariohysterectomy. The uterine horns were flushed and flushes were examined for ova or embryos. The pregnancy rate in group A was 63.6% and in group B 66.7%. Despite the significantly shorter period of pre-estrus a fertile estrus could be induced in 7 out of 11 treated bitches. Induction of a fertile estrus can be achieved with a GnRH-implant—already registered for the use in male dogs—placed subcutaneously on the medial side of the leg.