Effect of continuous infusion of oxytocin on length of the oestrous cycle and luteolysis in cattle

In Exp. I oxytocin (60 micrograms/100 kg/day) was infused into the jugular vein of 3 heifers on Days 14-22, 15-18 and 16-19 of the oestrous cycle respectively. In Exp. II 5 heifers were infused with 12 micrograms oxytocin/100 kg/day from Day 15 of the oestrous cycle until clear signs of oestrus. Blood samples were taken from the contralateral jugular vein at 2-h intervals from the start of the infusion. The oestrous cycle before and after treatment served as the controls for each animal. Blood samples were taken less frequently during the control cycles. In Exp. III 3 heifers were infused with 12 micrograms oxytocin/100 kg/day for 50 h before expected oestrus and slaughtered 30-40 min after the end of infusion for determination of oxytocin receptor amounts in the endometrium. Three other heifers slaughtered at the same days of the cycle served as controls. Peripheral concentrations of oxytocin during infusion ranged between 155 and 641 pg/ml in Exp. I and 18 and 25 pg/ml in Exp. II. In 4 our of 8 heifers of Exps I and II, one high pulse of 15-keto-13,14-dihydro-prostaglandin F-2 alpha (PGFM) appeared soon after the start of oxytocin infusion followed by some irregular pulses. The first PGFM pulse was accompanied by a transient (10-14 h) decrease of blood progesterone concentration. High regular pulses of PGFM in all heifers examined were measured between Days 17 and 19 during spontaneous luteolysis. No change in length of the oestrous cycle or secretion patterns of progesterone, PGFM and LH was observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Extended function of the corpus luteum and earlier development of the second follicular wave in heifers treated with bovine somatotropin

Effects of recombinant bovine somatotropin (bST) on growth of the corpus luteum (CL) and development of ovarian follicles were tested. Starting at estrus (Day=0), the following treatments were administered: control (saline injected Days 0 to 19, n=5); bST[0-9] (25 mg bST injected Days 0 to 9, saline injected Days 10 to 19, n=5); bST[10-19] (saline injected Days 0 to 9, 25 mg bST injected Days 10 to 19, n=5); and bST[0-19] (25 mg bST injected Days 0 to 19, n=6). Blood was collected daily for progesterone analysis, and ultrasound examinations were performed daily for measurement of follicles and CL. Compared with the heifers treated with saline, those treated with bST had larger CL and more progesterone during the early (/=10 mm) follicles was greater (P<0.01) and largest follicles were smaller (P<0.001) in bST than in saline-treated heifers. Estrous cycle length and ovulation rate were similar for each group. In conclusion, bST increased initial development of the CL and extended its function. Furthermore, the second follicular wave was earlier with bST.     

Synthetic microspheres transferred to the rat oviduct on day 1 of pregnancy mimic the transport of native ova

Microspheres of various materials and diameters were transferred microsurgically to the rat oviduct on Day 1 of pregnancy and autopsies were done at various times thereafter up to Day 10 to assess the recovery and segmental distribution of microspheres and eggs in the genital tract or the viability of embryos. The number and distribution of eggs in the treated and control sides after unilateral transfers were not different on Day 4 and 5 and the number of embryos implanted on Day 10 was not significantly affected after bilateral transfers. The segmental distribution of eggs and starch microspheres within the oviduct on Days 2, 3 or 4 showed that both are transported partly intermingled from ampulla to uterus. When microspheres of poly(DL-lactide-co-glycolide), starch, dextran or dextran blue were transferred, their distribution in the genital tract in the morning of Day 5 showed that poly(DL-lactide-co-glycolide) and dextran microspheres stayed longer in the oviduct while starch and dextran blue microspheres were transported to the uterus at the same time as the eggs. Transfer of starch microspheres of 40-60 microns to one oviduct and 180-200 microns in diameter to the opposite oviduct showed that distribution on one side was nearly identical to that of the other side from Days 2 to 5. We conclude that the behaviour of synthetic surrogate ova in rats differs from that in rabbits. The rat oviduct does not change the rate of transport of native eggs following transfer of synthetic surrogate ova.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of the Storage in an Atomosphere of Carbon Dioxide on Ovomucin

The yolk index of newly laid egg was 0.50, while that of the egg stored at 30°C for 15 days in an atmosphere of carbon dioxide at a pressure of 2 kg/cm² and in air was 0.43 and 0.25, respectively.

The carbohydrate content of ovomucin gel (B) obtained from the eggs stored in an atmosphere of carbon dioxide was higher than that of ovomucin gel (B) obtained from the eggs stored in air.

The free boundary electrophoretic pattern of ovomucin gel (B) obtained from the eggs stored in an atmosphere of carbon dioxide consisted of two peaks, and the relative mobility of each peak showed the same value as that of the corresponding each peak of ovomucin gel (B) obtained from newly laid egg white.

The fractionation pattern obtained by density gradient column electrophoresis of ovomucin gel (B) obtained from the eggs stored in an atmosphere of carbon dioxide showed two peaks, peak-F and peak-S, while that of the eggs stored in air showed a considerable diminution in peak-F.

From these results, discussion was made about the occurrence and mechanism of egg white thinning when eggs were stored in an atmosphere of carbon dioxide.     

Neither plasma progesterone concentrations nor exogenous eCG affects rates of ovulation or pregnancy in fixed-time artificial insemination (FTAI) protocols for puberal Nellore heifers

The objective was to evaluate the effects of plasma progesterone (P4) concentrations and exogenous eCG on ovulation and pregnancy rates of pubertal Nellore heifers in fixed-time artificial insemination (FTAI) protocols. In Experiment 1 (Exp. 1), on Day 0 (7 d after ovulation), heifers (n = 15) were given 2 mg of estradiol benzoate (EB) im and randomly allocated to receive: an intravaginal progesterone-releasing device containing 0.558 g of P4 (group 0.5G, n = 4); an intravaginal device containing 1 g of P4 (group 1G, n = 4); 0.558 g of P4 and PGF_2α (PGF; 150 μg d-cloprostenol, group 0.5G/PGF, n = 4); or 1 g of P4 and PGF (group 1G/PGF, n = 3). On Day 8, PGF was given to all heifers and intravaginal devices removed; 24 h later (Day 9), all heifers were given 1 mg EB im. In Exp. 2, pubertal Nellore heifers (n = 292) were treated as in Exp. 1, with FTAI on Day 10 (30 to 36 h after EB). In Exp. 3, pubertal heifers (n = 459) received the treatments described for groups 0.5G/PGF and 1G/PGF and were also given 300 IU of eCG im (groups 0.5G/PGF/eCG and 1G/PGF/eCG) at device removal (Day 8). In Exp. 1, plasma P4 concentrations were significantly higher in heifers that received 1.0 vs 0.588 g P4, and were significantly lower in heifers that received PGF on Day 0. In Exp. 2 and 3, there were no significant differences among groups in rates of ovulation (65-77%) or pregnancy (Exp. 2: 26-33%; Exp. 3: 39-43%). In Exp. 3, diameter of the dominant ovarian follicle on Day 9 was larger in heifers given 0.558 g vs 1.0 g P4 (10.3 ± 0.2 vs 9.3 ± 0.2 mm; P < 0.01). In conclusion, lesser amounts of P4 in the intravaginal device or PGF on Day 0 decreased plasma P4 from Days 1 to 8 and increased diameter of the dominant follicle on Day 9. However, neither of these nor 300 IU of eCG on Day 8 significantly increased rates of ovulation or pregnancy.     

Embryo survival in heifers after transfer of an egg to the uterine horn contralateral to the corpus luteum and the effect of treatments with progesterone or hCG on pregnancy rates.

Day 7 eggs (oestrus = Day 0) were surgically transferred singly to the uterine horn contralateral to the CL and heifers were either slaughtered on Day 24-26 (Group 1) or palpated per rectum on Day 42 (Group 2) to determine the presence of a developing conceptus and a maintained corpus luteum. There was a fall in pregnancy rate of the control heifers in Groups 1a (6/10) and 2a (2/10) (P = 0.085). Pregnancy rate was unaffected by progesterone treatments from Day 13 to the day before slaughter in Group 1b (8/10), or to Day 23 in Group 2b (2/10). Two of the conceptuses recovered in Group 1b were developing in the presence of regressed corpora lutea. There was, however, an increase in pregnancy rate in Group 2d (6/10) compared with Group 2a (2/10) when heifers were treated with hCG from Days 13 to 35 (P = 0.085). The results indicated that embryonic death is occurring after Day 24 and suggest that a change in the nature of the embryonic signal may be occurring at this time.     

The effects of platelet-activating factor on the output of prostaglandins from the guinea-pig uterus

Platelet-activating factor (PAF) significantly increased the output of prostaglandin (PG) F2 alpha from the guinea-pig uterus during the mid-cycle phase (Days 6-10), but only had a small, non-significant stimulatory effect on the outputs of PGE2 and 6-keto-PGF1 alpha. PAF significantly increased the outputs of PGF2 alpha, PGE2 and 6-keto-PGF1 alpha from the guinea-pig uterus during the later phase of the cycle (Days 15-17). Lack of extracellular calcium did not affect the stimulatory effect of PAF on uterine PG output. However, TMB-8 (an intracellular calcium antagonist) prevented the increases in uterine PG output produced by PAF at both phases of the cycle. These results suggest that the stimulatory effect of PAF on uterine PG output in the guinea-pig is dependent upon the mobilization of intracellular calcium but is not dependent upon the uptake of extracellular calcium. Also, the weak stimulatory effect of PAF on PGE2 output from the uterus during the mid-cycle phase indicates that, if PAF is involved in implantation in guinea-pigs, it probably does not act via PGE2. Also, the lack of an inhibitory effect of PAF on uterine PGF2 alpha synthesis and release suggests that PAF is not the anti-luteolytic factor produced by the guinea-pig conceptus during early pregnancy.     

Accuracy of ultrasonography for pregnancy diagnosis on days 10 to 22 in heifers

Two operators independently conducted ultrasonic pregnancy examinations on nulliparous Holstein heifers on Days 10, 12, 14, 16, 18, 20 and 22, and assigned a diagnosis (pregnant or nonpregnant) and a score for degree of certainty in the diagnosis (1, 2 or 3 for low, intermediate or high, respectively). Pregnancy was retrospectively confirmed by the ultrasonographic detection of an embryo proper and embryonic heartbeat on Day 24 in 20 25 bred heifers; the five nonpregnant heifers were excluded from the analyses. Eleven nonbred heifers were included as an unequivocal source of nonpregnant heifers. Accuracy was not significantly greater than a guess (50%) before Day 18, but reached 100% on Days 20 and 22. Mean accuracy was higher (P<0.005) for nonpregnant (65 77 , 84%) than pregnant heifers (91.5 140 , 65%). For certainty score, there were main effects of day (P<0.0001), reproductive status (pregnant or nonpregnant, P<0.003), and an interaction of day and reproductive status (P<0.0001). The certainty score increased in all heifers among days and was higher (P<0.05) in pregnant than nonpregnant heifers on Days 16 to 20. For luteal area (area of corpus luteum, excluding area of fluid filled center, if present), there were significant main effects of day, reproductive status and a day by status interaction (P<0.0001 for each). Luteal area was approximately constant in pregnant heifers, but in nonpregnant heifers it was lower (P<0.05) on Days 16 to 22 than on Days 10 to 14. Uterine echotexture was scored on a scale of 1 to 3, characteristic of a diestrus, intermediate and estrus uterus, respectively. There were main effects of day and reproductive status (P<0.0001 for each) and an interaction of day and reproductive status (P<0.025). Uterine echotexture was approximately constant in pregnant heifers, but in nonpregnant heifers it was higher (P<0.05) on Days 16 to 22 than on Days 10 to 14. Pregnancy diagnosis on Days 10 to 14 was based on detection of the conceptus; however, detection of the conceptus was not accurate prior to visualization of the embryo proper (mean Day 22, range Days 20 to 24). In nonpregnant heifers, a correct diagnosis with high certainty was made when a small corpus luteum and uterine echotexture characteristic of estrus were detected. In the absence of these changes on Days 18 to 22, a diagnosis of pregnancy was made with high accuracy and intermediate or high certainty.     

Effects of hyperadrenal states on luteinizing hormone in cattle

The effect of an induced hyperadrenal state on luteinizing hormone (LH) secretion and subsequent ovarian function was examined in both intact and adrenalectomized (ADRX) heifers. Treatments were begun on Day 2 or Day 16 of an estrous cycle in order to examine their effect on corpus luteum development or ovulation, respectively. In Experiment I, continuous intravenous infusion of ACTH (1.0 mg/24 h) to intact heifers decreased LH concentrations during the early phase of the cycle (Days 3-5). Treatment of ADRX heifers with hydrocortisone succinate (HS) (100 mg/24 h) did not appear to change mean LH concentrations, although da Rosa and Wagner (1981) have reported reduced plasma concentrations of progesterone at mid-cycle in these ACTH-treated intact heifers and HS-treated ADRX heifers. ACTH treatment of ADRX heifers had no effect on LH or progesterone. In the second study, there were similar frequencies of LH surges at the anticipated time of ovulation in all treatment groups. HS (100 mg/24 h) in ADRX heifers and ACTH (0.5 mg/24 h) in intact heifers was given continuously beginning on Day 16 of an estrous cycle. Although some animals in all groups exhibited LH surges, the ACTH-treated intact and HS-treated ADRX heifers failed to show a consistent subsequent increase in progesterone concentrations in plasma, suggesting a failure of luteal development. Although no difference was seen in baseline concentrations of LH, there was a greater difference between basal and overall mean LH concentrations in control groups than was observed in ACTH- or HS-treated animals. These induced hyperadrenal states resulted in depression of ovarian function as shown by decreased plasma progesterone during the luteal phase of the cycle. It is not known if other noncorticoid steroids from the adrenal cortex are necessary for a full expression of this effect.     

Superovulation in heifers given FSH initiated either at day 2 or day 10 of the estrous cycle

The aim of this study was to determine if initiation of superovulation in heifers during the time of development of the first dominant follicle (Days 2 to 6) would give equivalent ovulation and embryo production rates as treatment initiated at mid-cycle. Estrus was synchronized in 60 beef heifers using luprostiol (PG) and they were randomly allocated to treatment with 4.5, 3.5, 2.5 and 1.5 mg of porcine follicle stimulating hormone (FSH) administered twice daily, either on Days 2, 4, 5 and 6 (Day-2 group), respectively, or with similar doses at four consecutive days during mid-cycle (Day-10 group, initiation on Day 9 to 11). All heifers received 500 mug cloprostenol at the fifth FSH injection and 250 mug at the sixth injection. Blood samples for progesterone determination were collected at the time of FSH injections. Heifers were slaughtered 7 d post estrus, and the number of ovulations and large follicles (>/=10mm) were determined on visual inspection of the ovary. Following flushing of the uterine horns the quality of embryos and the fertilization rate were determined. Significant differences between treatments were determined using a two-sided t-test, and frequency distributions were compared using Chi-square tests. The mean number (+/-SEM) of ovulations for heifers in the Day-10 group was 12.9+/-1.0, and 8.5+/-0.9 embryos were recovered. Both the number of ovulations (6.7+/-0.8) and embryos recovered (4.1+/-0.6) were lower (P=0.0001) in heifers in the Day-2 group. Following grading based on a morphological basis, a higher number (P=0.002) of embryos was categorized as Grades 1 and 2 (4.1+/-0.6) and Grade 3 (2.1+/-0.4) in Day-10 heifers than in the Day-2 group (Grade 1 and 2, 1.9+/-0.3; Grade 3, 0.7+/-0.2). The number of Grade 4 and 5 embryos (Day 10, 1.6+/-0.2; Day 2, 1.4+/-0.2) and the number of unfertilized ova (Day 10, 0.7+/-0.4; Day 2, 0.2+/-0.1) did not differ between treatments. Progesterone concentrations were lower (P=0.0001) in Day-2 heifers at FSH treatment prior to prostaglandin, and the decline was more rapid following prostaglandin injection at Day 5 (P=0.02). Results of this study indicate that the number of ovulations and embryos recovered was lower in heifers when FSH treatment was initiated on Day 2 compared with Day 10 of the estrous cycle.     

Embryo transport through the mare's oviduct depends upon cleavage and is independent of the ipsilateral corpus luteum.

Two experiments were conducted using 14 mares. In Exp. 1, mares were inseminated with semen treated with TEPA, which, in other species, has been shown to lead to an arrest in ovum cleavage at 2--4 cells. The oviducts and/or uterus were then flushed 7--10 days after ovulation in 6 mares (Group A) or 2--6 days after ovulation in 5 mares (Group B). Fresh eggs were found in the oviduct flushes of 5 Group A and 5 Group B mares: 9 of the 10 eggs appeared to have cleaved, but none had developed beyond 16-cells. Seven eggs contained spermatozoa and 3 of 4 eggs from each group showed evidence of fertilization when examined ultrastructurally. Group A mares had thus retained fertilized eggs in the oviduct beyond the time at which they would normally have entered the uterus (6 days), indicating that development beyond at least the 2- to 4-cell stage is necessary for normal transport. In Exp. 2, 5 attempts were made to recover the embryo within 4 days of ovulation and transfer it to the contralateral oviduct. A single pregnancy resulted, indicating that a unilateral interaction with the corpus luteum was not necessary for the transport of the embryo to the uterus.     

Effect of a unilateral or bilateral twin embryo distribution on twinning and embryo survival rate in the cow

Uni- and bilateral twin embryo distributions were effected by the transfer of one embryo on Day 7 to the ipsi- or contralateral uterine horn of previously inseminated heifers (123, Exp. 1) or cows (95, Exp. 2). The embryo transfers were surgical in Exp. 1 and non-surgical in Exp. 2. Transferred and native embryos were distinguished by breed. Embryo survival rate was measured in a proportion (N = 40) of the heifers at Day 53 of gestation and in the remainder of the heifers and all of the cows at term. In the heifers (Exp. 1) overall pregnancy rates of 76% and 75% were recorded after uni- and bilateral twin embryo distributions respectively. Twinning rates of 55% and 60% at Day 53 of gestation and 60% and 60% at term were recorded for uni- and bilateral distributions respectively. In the cows (Exp. 2) calving rates of 61% and 63% and twinning rates of 33% and 38% were recorded following uni- and bilateral twin embryo distributions respectively. When the data from both experiments were combined, overall embryo survival rates were similar for both twin embryo distributions although the ipsilateral transfer of an embryo reduced the survival rate of the native embryo. It is concluded that the confinement of two embryos in one uterine horn on or after Day 7 does not depress pregnancy, twinning or overall survival rate to term.     

Studies on maturation of genitalia in murrah buffalo-heifers

Studies on the growth of uterine horns and cervix were conducted on 161 prepuberal, puberal and postpuberal (non-gravid) farm-reared buffalo heifers. Age of the buffalo heifers varied between 17 and 37 months, while body weight range was 180–500 kg. The approximate diameters of the mid-cervix and uterine cornua (at the point of pseudobifurcation) were visualized mentally by palpating the organs per rectum with fingers of the left hand while focusing the adjudged diameters between the jaws of a vernier caliper held in the other hand. Both uterus and cervix increased progessively with the advancing age and body weight of heifers, however, the growth of the cervix was more consistent compared to that of the uterus. A marked enlargement in uterine cornua was noted at the time of puberty, however, the rate of cornual growth declined with subsequent estrous cycles.     

A study of two protocols combining aglepristone and cloprostenol to treat open cervix pyometra in the bitch

To compare the efficacy and safety of two protocols using a combination of aglepristone and cloprostenol for the treatment of open cervix pyometra in the bitch and to describe the progesterone (P4) serum profiles before and during treatments, 15 bitches were randomly allocated into two treatment groups: I (n = 8): aglepristone was administered at 10mg/kg, s.c., on Days 1, 3, 8, and 15 (if not cured), combined with cloprostenol at the dose of 1 microg/kg, s.c., on Days 3 and 8, and II (n = 7): received the same treatment with aglepristone as Treatment I but cloprostenol on Days 3, 5, 8 10, 12, and 15 (if not cured). Before the beginning of the treatments and then on Days 8, 15, and 29 all bitches were evaluated for clinical signs, side effects, hemogram, serum P4 concentrations, and uterus diameters. Bitches in both treatment groups, with (n = 6) or without (n = 9; > or =1.2 ng/ml) initial basal P4 serum concentrations, achieved treatment success without side effects and no significant differences, either on Day 15 (6/8 for Treatment I and 4/7 for Treatment II) or on Day 29 (2/8 for Treatment I and 3/7 for Treatment II). In both treatments groups, clinical signs, blood parameters, and uterine diameters improved to normal values throughout the experiments. A significant interaction between day and treatment was found for percentage change in P4 when all bitches were considered together. Redevelopment of pyometra in the next estrous cycle occurred in 20% of the bitches. One nonrecurrent bitch was mated and whelped a normal litter. It is concluded that these two combined protocols proved to be efficient and safe in reversing clinical signs of open cervix pyometra independently of initial P4 concentrations and that the number of cloprostenol administrations seemed to have an effect on P4 serum changes throughout treatments.     

Viability of bovine demi- and quarter-embryos after transfer

The viability of bovine demi- and quarter-embryos was investigated. Early compacting morulae were nonsurgically flushed from superovulated donor cows and were bisected by two microneedles. One of the halves was then split further into two quarters. Each demi- and quarter-embryo was placed in an evacuated zona pellucida. One demi- or two quarter-embryos were transferred non-surgically into cow or heifer recipients. Viability was measured by ultrasound scanning of the fetuses on Days 35, 48 and 60 of pregnancy. The pregnancy rates at Day 60 were 46.2% (6 13 ) for heifers and 33.3% (4 12 ) for cows after the transfer of a single demi-embryo. The transfer of two quarter-embryos resulted in a pregnancy rate of 61.5% (8 13 ) for heifers and 8.3% (1 12 ) for cows. Seven (53.8%) and four (33.3%) live fetuses were found on Day 60 following the transfer of demi-embryos into heifers and cows, respectively. The transfer of quarter-embryos resulted in 10 fetuses (38.5%) in the heifer recipients and only one fetus (4.2%) in the cow recipients. The results of this study suggest that heifers are more suitable than cows as recipients for quarter-embryos.     

Suppression of dominant and subordinate ovarian follicles by a proteinaceous fraction of follicular fluid in heifers

Nulliparous Holstein heifers were examined ultrasonically once daily during an interovulatory interval (ovulation = Day 0). Follicles with a diameter >/=4 mm were sequentially identified. Heifers were randomized into four groups (n = 4 heifers per group): untreated control heifers and those treated on Days 0 to 3, Days 3 to 6, or Days 6 to 11. Heifers designated for treatment were given an intravenous injection, twice daily, of a proteinaceous fraction of follicular fluid (PFFF; 16 ml) prepared by extracting bovine follicular fluid with activated charcoal. Mean cessation of growth of the dominant follicle of Wave 1 was later (P<0.005) in control heifers (Day 5.5) than in heifers treated on Days 0 to 3 (Day 1.5) or Days 3 to 6 (Day 3.5). Mean onset of regression of the dominant follicle of Wave 1 was later (P<0.005) in control heifers (Day 12.0) than in heifers treated on Days 0 to 3 (Day 5.0) or Days 3 to 6 (Day 7.5). Mean cessation of growth of the largest subordinate follicle of Wave 1 was later (P<0.05) in control heifers (Day 3.0) than in heifers treated on Days 0 to 3 (Day 1.2). Mean onset of regression of the largest subordinate follicle of Wave 1 was later (P<0.05) in control heifers (Day 7.0) than in heifers treated on Days 0 to 3 (Day 4.8). In heifers treated on Days 6 to 11, cessation of growth and onset of regression of the dominant follicle (means, Days 5.2 and 12.0, respectively) were not significantly different from those of the controls. The hypothesis that PFFF treatment on Days 0 to 3 would cause suppression of all follicles of Wave 1 was supported. The hypothesis that PFFF treatment on Days 3 to 6 would not alter growth of the dominant follicle of Wave 1 was not supported. The mean day of detection of the dominant follicle of Wave 2 was different (P<0.005) in control heifers (Day 8.5) than in heifers treated on Day 0 to 3 (Day 5.5) or Days 6 to 11 (Day 14.2). The mean length of the interovulatory interval was shorter (P<0.05) in control heifers (20.5 d) than in heifers treated on Days 6 to 11 (23.2 d). The hypothesis that PFFF treatment on Days 6 to 11 would delay the emergence of Wave 2 was supported. The proportion of heifers with 2-wave interovulatory intervals was 3 4 for control heifers and 0 4 , 1 4 , and 4 4 for heifers treated on Days 0 to 3, Days 3 to 6, and Days 6 to 11, respectively (3 4 vs 0 4 , P<0.05); the remaining heifers had 3-wave interovulatory intervals. On average, in PFFF-treated heifers, follicles stopped growing 1 d after treatment was started, and Wave 2 was detected 3 d after treatment was stopped.     

Turkey hen fertility and egg production after artificial insemination and multiple oviduct eversion during the pre-laying period

The onset of egg production (mean 18.3 days after the onset of photostimulation) and the rate of egg production (flock averaged 4.9 eggs per bird per week for the first 8 weeks of egg production) were not affected by 5 days of twice daily oviduct eversion ('venting') in the pre-laying period when compared to unvented controls. After the onset of photostimulation, pre-laying hens were inseminated twice daily on Days 12 to 16 with 3 microliter semen containing 15 x 10(6) spermatozoa, and compared with groups of hens inseminated once daily on Days 15 and 16 with 15 microliters semen containing 75 x 10(6) spermatozoa or 41 microliter semen containing 200 x 10(6) spermatozoa. Fertility remained high for the first 5 weeks of egg production. However, by Week 6 the fertility of the hens receiving frequent low doses of semen dropped significantly below that of the others, which suggests that multiple inseminations with a low semen volume containing relatively low numbers of spermatozoa does not lead to an increase in the efficacy of sperm transport and storage in the oviduct.     

A model for cystic endometrial hyperplasia/pyometra complex in the bitch

The objective of this study was to develop a reliable model for the study of the cystic endometrial hyperplasia and pyometra complex (CEH/P) in the bitch. Greyhound bitches (n = 15) were ovariectomised and allocated into three groups (Group 1, n = 5; Group 2, n = 5; Group 3, n = 10, including 5 used from Group 1). Simulated proestrus, estrus and diestrus were induced by treatment with estradiol benzoate and megestrol acetate. The duration of cervical opening during estrus was determined by the intra-vaginal infusion of radio-opaque medium and subsequent radiography of the uterus (Group 1). One milliliter of a culture of Escherichia coli (with five uro-pathogenic virulence factors as identified by PCR: pap, sfa, hlyA, cnf1 and fim) was inoculated intra-vaginally daily throughout the simulated estrus (Group 2). One milliliter of the culture (n = 6) or sterile Luria-Bertani broth (n = 4) was introduced directly into the uterus on simulated diestrus Days 8 or 12 (Group 3). Necropsies were performed 12 and 7-14 days after the inoculation (Groups 2 and 3). The cervix remained open throughout the duration of simulated estrus (5-6 days) in four out of five bitches, and for a shorter duration (3 days of a 6-day estrus period) in one bitch (Group 1). CEH/P was induced by inoculation of bacteria into the uterus (10/10 bitches) but not into the vagina (0/5 bitches), (P = 0.003). A model for the study of CEH/P has been validated.     

Effect of purified llama ovulation-inducing factor (OIF) on ovarian function in cattle

Two experiments were designed to determine the effect of purified ovulation inducing factor (OIF) on ovarian function in cattle. In Experiment 1, prepubertal heifers (n = 11 per group) were treated on Day 5 (Day 0 = day of follicular wave emergence) of the follicular wave with an intramuscular dose of saline (1 mL), GnRH (100 μg), or purified OIF (1 mg/100 kg body weight). Ovulation occurred in 9/11 heifers treated with GnRH, and 1/11 heifers in each of the OIF- and saline-treated groups (P < 0.05). Compared to saline-treated controls, OIF treatment was associated with a smaller dominant follicle diameter (P < 0.01), a rise in plasma FSH concentration (P < 0.1), and earlier emergence of the next follicular wave (P < 0.05). In Experiment 2, sexually mature heifers were given either GnRH or purified OIF on Days 3, 6 or 9 of the first follicular wave (i.e., early growing, early static, or late static phase of the dominant follicle; n = 5 per group per day), or were untreated (n = 10). In heifers treated with OIF on Day 6, the dominant follicle diameter profile tended to be smaller than in controls, and was associated with a rise (P < 0.05) in plasma FSH concentrations. A similar rise in FSH was detected after OIF treatment on Day 9. Compared to untreated controls, treatment with OIF and GnRH was associated with a larger CL diameter (Days 3 and 6 groups; P < 0.05) and a greater concentration of plasma progesterone (Days 6 and 9 groups; P < 0.05). Treatment with purified OIF did not induce ovulation in heifers, but hastened new follicular wave emergence in prepubertal heifers, influenced follicular dynamics in a phase-specific manner in mature heifers, and was luteotrophic.