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PubMed1983

Induction of estrous behavior in ovariectomized rats by sequential replacement of estrogen and progesterone to the ventromedial hypothalamus.

The present experiment was designed to determine whether sequential replacement of estrogen and progesterone to the ventromedial hypothalamus (VMH) would be sufficient to induce estrous behavior in ovariectomized rats. Bilateral cannulae containing 17 beta-estradiol (E2) diluted with cholesterol (1:250) were lowered into the VMH, preoptic area or midbrain and left in place for 4 days. On day 5, the E2 inserts were removed and P-filled cannulae were lowered into half of the subjects. The remaining females received systemic progesterone (500 micrograms). This steroid regimen was repeated 2 weeks later with the mode of progesterone administration reversed. All subjects were tested for estrous behavior twice after progesterone treatment. In a second experiment, 3H-P:P-filled cannulae were lowered into the VMH of estrogen-primed females in order to estimate the extent of hormone spread from full-strength P-filled cannulae. Results indicated that estrogen and progesterone stimulation of the VMH is sufficient to activate estrous behavior in spayed female rats, however, precise localization of the hormone implants within the VMH is essential. 9 of the 11 females with both cannulae located within or at the border of the ventromedial nucleus (VMN) exhibited estrous behavior whereas only half of the females with only one implant resting in the VMN exhibited estrous responsiveness. Subjects with neither cannula located within or at the border of the VMN did not exhibit the behavior. The facilitative effects of P appeared to result from hormonal stimulation of the VMH and not from leakage of the steroid into other brain regions or into the systemic circulation. Following placement of tritiated progesterone implants into the VMH, high levels of radioactivity were recovered only from the mediobasal hypothalamus. The low levels of radioactivity measured in other brain regions, pituitary, uterus and blood indicate that relatively little if any hormone reached these tissues.

Animals↗
PubMed2005

Pregnancy rates in repeat-breeder heifers following multiple artificial inseminations during spontaneous oestrus.

Hormonal asynchronies during oestrus, related to the presence of suprabasal plasma-progesterone (P4) concentrations and a delayed ovulation, interfere with the fertility of repeat-breeder heifers (RBH). Since tubal dysfunction can occur in connection with hormonal asynchronies and constrained availability of fertile spermatozoa at the time of ovulation, the present study tested the hypothesis that frequent sperm deposition from onset of oestrus to ovulation may improve pregnancy rates in RBH. Five RBH and five virgin heifers (VH; controls) were repeatedly artificially inseminated (AI) at 6 h intervals from onset of oestrus to spontaneous ovulation. Hormone analyses revealed suprabasal P4 concentrations and a delay in the occurrence of the luteinising hormone (LH) surge, but a normal cortisol profile in RBH. Compared with controls, RBH presented longer interval from onset of oestrus to ovulation, and therefore, received more AIs. Pregnancy rates in RBH reached control levels (60%; NS), indicating that the hypothesis might be correct. Pregnancy rates in VH were below the expected range, presumably attributed to a deleterious influence of the frequent handling. The study suggests that pregnancy rates can be improved in RBH by frequent AI in relation to spontaneous ovulation. However, this practice of repeated manipulations, while seeming not to show adverse effects, lacks practicality for routine use.

Animals↗
PubMed2003

Immunotoxic destruction of distinct catecholaminergic neuron populations disrupts the reproductive response to glucoprivation in female rats.

We tested the hypothesis that hindbrain catecholamine (norepinephrine or epinephrine) neurons, in addition to their essential role in glucoprivic feeding, are responsible for suppressing estrous cycles during chronic glucoprivation. Normally cycling female rats were given bilateral injections of the retrogradely transported ribosomal toxin, saporin, conjugated to monoclonal dopamine beta-hydroxylase antibody (DSAP) into the paraventricular nucleus (PVN) of the hypothalamus to selectively destroy norepinephrine and epinephrine neurons projecting to the PVN. Controls were injected with unconjugated saporin. After recovery, we assessed the lesion effects on estrous cyclicity under basal conditions and found that DSAP did not alter estrous cycle length. Subsequently, we examined effects of chronic 2-deoxy-d-glucose-induced glucoprivation on cycle length. After two normal 4- to 5-d cycles, rats were injected with 2-deoxy-d-glucose (200 mg/kg every 6 h for 72 h) beginning 24 h after detection of estrus. Chronic glucoprivation increased cycle length in seven of eight unconjugated saporin rats but in only one of eight DSAP rats. Immunohistochemical results confirmed loss of dopamine beta-hydroxylase immunoreactivity in PVN. Thus, hindbrain catecholamine neurons with projections to the PVN are required for inhibition of reproductive function during chronic glucose deficit but are not required for normal estrous cyclicity when metabolic fuels are in abundance.

Animals↗
PubMed2006

Relationship between the first ovulation within three weeks postpartum and subsequent ovarian cycles and fertility in high producing dairy cows.

The aim of this study was to investigate the relationship between the first ovulation within 3 weeks postpartum and subsequent ovarian cycles and fertility in high producing dairy cattle in Hokkaido, Japan. In Experiment 1, 110 cows (44 primiparous and 66 multiparous) were used to determine the effects of the first ovulation within 3 weeks postpartum on subsequent ovarian cycles. Milk samples were collected twice weekly from 7 to 100 days postpartum. The first ovulation was identified by an increase in milk progesterone (P4) to more than 1 ng/ml within 3 weeks postpartum. The numbers of cows showing ovulation and anovulation within 3 weeks postpartum were 31 (70.5%) and 13 (29.5%) in the primiparous cows and 35 (53.0%) and 31 (47.0%) in the multiparous cows, respectively. The patterns of ovarian resumption after calving were classified into two types (normal ovarian cycles and abnormal ovarian cycles) on the basis of milk P4 concentrations. Initiation of normal ovarian function in cows ovulated within 3 weeks postpartum occurred earlier than in anovulated cows regardless of the number of calvings (primiparous, 27.8 days vs. 44.4 days; multiparous, 30.6 days vs. 55.7 days; P<0.01). Out of the multiparous cows that ovulated within 3 weeks postpartum, initiation of normal ovarian function followed by a normal luteal phase was earlier than when it was followed by an abnormal luteal phase (25.5 days vs. 40.4 days; P<0.05). Milk P4 concentrations after the first ovulation were lower than those after the second ovulation in both the primiparous and multiparous cows (P<0.05). In Experiment 2, 22 multiparous cows were used to determine the effects of the first ovulation within 3 weeks postpartum on subsequent fertility. Blood samples were collected once a week from 0 to 3 weeks postpartum. The interval from parturition to first service in ovulated cows was shorter than in anovulated cows (68.4 days vs. 94.8 days; P<0.05). The conception rate by 100 days after calving tended to be higher in ovulated cows than in anovulated cows (50.0% vs. 16.7%, P=0.09). In conclusion, our data strongly suggests that ovulation within 3 weeks postpartum is a crucial phenomenon for subsequent resumption of ovarian function and conception, and thus it can be used as an index of subsequent reproductive performance.

Animals↗
PubMed2003

Development of a method of diagnosing ovarian disorders in sows and gilts using uterine ultrasonography.

In ultrasonographic diagnosis of ovarian disorders and the estrous cycle in sows, transverse observation of the uterus yielded more characteristic findings than observation of sagittal sections. Transverse ultrasonography revealed that the low progesterone (P) type uterus showed a round structure, while the high P type uterus showed a flattened structure. These results corresponded well with rectal palpation findings: the low P type uterus had a hard, pipe-like structure and the high P type a soft, balloon-like structure. For gilts, we employed a minimum convex type transrectal prostate probe that had an approximately 18 cm insertion handle. The images of the uterus obtained thereby were a similar to those obtained from sows. The above results suggest that it should be possible to diagnose and treat many ovarian disorders in sows and gilts based only on the ultrasonograhic findings. In short, ultrasonograhic findings of a round structure of the uterine wall might be an indication for PMSG (pregnant mare serum gonadotropin) treatment, while findings of a flattened structure might be an indication for PGF(2) (alpha) administration.

Animals↗
PubMed2003

Application of timed artificial insemination protocols to grazing Japanese black cattle with long open period.

To investigate the viability of timed artificial insemination (TAI) protocols in grazing Japanese Black cattle with long open period, ovarian status and progesterone and estradiol-17 beta profiles of the animals during the protocol were monitored. In 1998, prosta-glandin F(2a) (PG) was administered to 36 animals seven days after GnRH injection. Three out of the 36 animals were inseminated after detection of estrus and did not receive further treatment. The second GnRH was injected to the remaining 33 animals 48 hr after the PG injection and TAI was performed 24 hr later. In 1999, PG was injected to 25 animals six days after GnRH, the second GnRH was injected to 22 animals 48 hr after PG, and TAI was performed 16 hr later (The other three animals were inseminated before the time of TAI). The percentage of the animals with at least one functional corpus luteum and one follicle equal to or greater than 10 mm in diameter at PG injection was similar between the groups in 1998 and 1999. Likewise, the hormonal profiles were similar between the two groups. Pregnancy rates (PR) after the TAI protocols and natural mating in 1998 and 1999 were 75.0% and 88.0%, respectively. These figures were comparable to the PR obtained by conventional estrus synchronization protocols using PG (in 1995; 69.4%) or CIDR (in 1996; 59.1%). In conclusion, the TAI protocol can be applicable into grazing Japanese Black cattle with long open period.

Animals↗
PubMed1986

Multiple mating and siring success during natural oestrus in the ewe.

Ewes were each mated on four separate occasions, at 3, 9, 15 and 21 h after the start of oestrus and at each time by a different ram. The progeny were assigned to sires by blood typing, supplemented by resemblance between lambs and rams. The paternity of 64 lambs, born to 41 ewes, was established: 2 were conceived at a 3-h mating, 27 at 9h, 23 at 15 h and 12 at 21 h. The optimum time for a ram to inseminate, when in competition with others, is therefore 9-15 h after onset of oestrus, and this finding accords with behavioural observations. Ewes tended to lamb during the same half of the day as that when they had come into oestrus.

Animals↗
PubMed1982

[Menstrual cycle lengths and the estimated time of ovulation in the cynomolgus monkey (Macaca fascicularis)].

Establishing of an efficient system for the judgement of an optimal mating time is an important prerequisite for the successful development of a large scale breeding of macaques as laboratory animals. In general, an optimal mating time has been judged on the basis of individual records of menstruation. The length of the previous menstrual cycle has usually been used for the prediction of the next cycle length. In the present study, the lengths of 240 menstrual cycles of 60 cynomolgus monkeys of our breeding colony were statistically analysed. The mean and the standard deviation of those cycle-lengths were 29.4 and 4.3 days, respectively. Correlationship between the length of a menstrual cycle and the length of its previous cycle was statistically significant (p less than 0.05). However, practically the correlation was not meaningful because the correlation coefficient (r) was very small even if the length of the second one of two successive cycles (r = 0.26) or the average length of three successive cycles (r = 0.36) is selected as a reference length. In other words, a cycle length can not be predicted on the basis of the length of the previous menstrual cycle. However, a marked increase of serum follicle stimulating hormone (FSH) concentration was observed from 8 to 15 days after menstruation. In 60 per cent of the animals observed, FSH increased 10 to 11 days after menstruation. Ovulation was observed one or two days later than the day of FSH increase. Therefore, the optimal mating time is judged to be between 11 and 14 days after menstruation regardless of the menstrual cycle length.

Animals↗
PubMed2000

Ram seminal plasma and fertility: results from an ongoing field study.

The effects of partial replacement of ram semen diluent with ram seminal plasma on the fertility of ewes were studied. Crossbred Chios ewes (n = 152) were assigned to six groups. The oestrous cycles of the ewes were synchronised at the peak (Groups A, B, C and D) and at the end (Groups E and F) of the breeding season by means of intravaginal sponges impregnated with fluorogestone acetate (FGA) for 14 days. Four hundred IU of PMSG were injected intramuscularly at the time of sponge removal. Ewes of Groups A, C and E were artificially inseminated with ram semen diluted with skim milk extender, while those of Groups B, D and F with ram semen diluted with 50% skim milk and 50% ram seminal plasma. The addition of ram seminal plasma induced a significant increase (P < 0.05) in litter size in Groups B and D when compared with that of Groups A and C (1.85 and 1.88 vs. 1.39 and 1.52, respectively). This increase was not significant when insemination was performed at the end of the breeding season (2.0 vs. 1.4). These results indicate that the addition of seminal plasma can influence the fertility of ewes or the fertilising capacity of extended ram semen to some extent.

Animals↗
PubMed2000

Herd characteristics and management practices associated with bulk-tank somatic cell counts in herds in official Dairy Herd Improvement Association programs in Ohio.

OBJECTIVE: To identify herd characteristics and management practices associated with bulk-tank somatic cell counts (BTSCC) in dairy herds in Ohio enrolled in official Dairy Herd Improvement Association (DHIA) programs. SAMPLE POPULATION: 186 dairies in Ohio. PROCEDURE: All herds in official DHIA programs in 9 counties were asked to participate. Extensive information regarding herd characteristics and management practices was obtained, using a standardized questionnaire. Bulk-tank milk samples were requested from all participating herds for bacterial culture. Official DHIA test-day records for January 1997 were obtained from all herds enrolled in official DHIA programs in the 9 counties. Potential associations were identified, using multivariable ANOVA. RESULTS: Participation was 186 of 479 (39%) herds. Streptococcus agalactiae and Mycoplasma spp were not isolated from bulk-tank milk samples. Staphylococcus aureus was isolated from 64 of 172 (37%) of the herds. The BTSCC were inversely associated with peak daily milk production, postmilking teat disinfection, percentage of eligible cows in the herd detected in estrus, and directly related to the extent to which BTSCC was perceived as a herd problem during the preceding 2 years. Type of housing for nonlactating cows and product used for treatment of nonlactating cows also were significantly associated with BTSCC. CONCLUSIONS AND CLINICAL RELEVANCE: Consideration of herd characteristics and implementation of management practices associated with BTSCC could result in increased milk yield and production of milk with lower BTSCC.

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