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PubMed1988

Infanticide in rats: male strategy and female counter-strategy.

The present series of experiments addresses the question of whether mating governs infanticide in the male rat and, in addition, asks whether the female rat has available an effective counter-strategy to male infanticide. With regard to the first question, we found that mating provides a safeguard against the killing of own young. That is, mating induces a general inhibition of infanticide coincident with the birth of the male's young and a recrudescence of infanticide synchronized with their weaning. The particular gain realized in killing alien young depends on the age of young and consequently on whether the mother had reached postpartum estrus. We also found that the pregnant female has an effective strategy to counter male infanticide which she employs before the young are born. The data show that this counter-strategy involves the synthesis of a chemosignal of low volatility emitted during pregnancy. The possible role of the male's vomeronasal system in the reception of this chemosignal is discussed.

Aggression↗
PubMed2004

Relationships between sexual behaviour, dominant follicle area, uterus ultrasonic image and pregnancy rate in mares of two breeds differing in reproductive efficiency.

Weak or equivocal expression of oestrous behaviour, related to different level of mares' reactivity, may cause problems in oestrus detection and thus influence the reproductive efficiency. The aim of the study was to test whether a breed characterised by low pregnancy rate and high emotional reactivity (Thoroughbreds) differs in oestrous behaviour from a primitive breed with higher reproductive efficiency (Koniks). Additionally, the follicle size was examined to determine how it influences the intensity of oestrus and uterine ultrasonic image and whether the pregnancy rate differs in relation to the intensity of oestrous behaviour and the size of the dominant follicle(s) area on day preceding ovulation in both breeds. During four reproductive seasons the behaviour of 20 Konik polski (K) and 37 Thoroughbred (T) was observed during daily teasing. Simultaneously, the ultrasonic examinations of the reproductive system were carried out. The behaviour of mares was quantified by scoring on an 8-point scale (behavioural score, BS), according to increasing sexual receptivity. Cross-sectional follicular area (FA) was taken as a product of the two largest perpendicular follicular diameters and mean values for each breed were estimated on 1693 and 1982 mm2 for K and T mares, respectively (P < 0.05). Mares were classified according to the pooled area of dominant follicle (FA) during the preovulatory period: group A (FA < or = breed mean) and group B (FA > breed mean). Uterus image (UI) was scored (1-5) according to the increasing uterine echogenicity. The BS was higher (P < 0.01) in K mares (BS = 5.19) than in T mares (BS = 4.04). The BS was significantly related to increasing follicular area (FA). There was no breed difference in uterus image (UI) score. However, significant regression of UI on FA was found in K mares. The intensity of oestrus was positively related with UI (r = 0.29; P < 0.01) only in K mares, no such relationship was found in T mares. The pregnancy rate was significantly higher for K mares (88.5%) than for T mares (46.0%) and lower for T mares with less intense oestrous behaviour (29.4%) as compared to T mares with more intense oestrus (60.0%). No differences in pregnancy rate was found in mares belonging to A or B group of follicular area. The ascertained weaker oestrous behaviour in Thoroughbred was related to lower pregnancy rate. It is hypothesised that oestrus intensity may be the result of breed differences in the response of the neural system to follicular secretions, or may be an effect of higher incidence of multiple non-synchronic ovulation and/or higher sensitivity to stress in Thoroughbred mares.

Animals↗
PubMed1978

Recurrent breeding seasons in pinealectomized or optic-nerve-sectioned ferrets.

The breeding seasons of two groups of pinealectomized ferrets and one group of blind ferrets, with appropriate controls, were observed for up to 5 years after the operations. All animals showed recurrent breeding seasons. Both pinealectomized and blind animals became increasingly asynchronous after the first season, but showed no evidence of a free-running, endogenous circannual periodicity nor of synchronization to light or other environmental cues.

Animals↗
PubMed2006

Low blood ISG15 mRNA and progesterone levels are predictive of non-pregnant dairy cows.

ISG15 is induced by conceptus-derived interferon-tau in the endometrium on days 15-45 of pregnancy. It was hypothesized that pregnancy induces blood cell ISG15 gene expression and that low blood ISG15 mRNA levels provide an indication of non-pregnant cows on day 18. Blood was collected either on day 18 (n = 78) or on days 15-21, 25, and 32 (n = 21; serial collection) from dairy cows following artificial insemination (AI). Plasma progesterone concentration was determined using RIA. ISG15 mRNA levels were determined using real-time PCR. Pregnancy was diagnosed on day 32 using transrectal ultrasound. ISG15 mRNA levels increased after day 16, peaked at day 20 and then declined to day 16 levels by 32 days following AI. The average pregnancy rate was 43% based on blood cell ISG15 mRNA. The average pregnancy rate was 33% based on the transrectal ultrasound. Lower levels of ISG15 mRNA or progesterone during serial collections were 100% accurate in predicting non-pregnant cows based on day 32 transrectal ultrasound. However, detection of ISG15 mRNA yielded 78% accuracy in predicting pregnant cows, while progesterone yielded 58% accuracy. Average plasma progesterone based on pregnancy status according to ultrasound was consistently higher in pregnant (> 4 ng/ml) when compared with non-pregnant cows from days 15 to 32, except on day 16. It is concluded that detection of low blood ISG15 mRNA levels during serial collection from days 17 to 25 serves as an accurate indicator of cows that are not pregnant, thus allowing re-synchronization and insemination.

Animals↗
PubMed1993

Effect of environmental heat stress on follicular development and steroidogenesis in lactating Holstein cows.

Lactating Holstein cows were utilized over two replicate periods (July and September, 1990) to examine the effect of summer heat stress on follicular growth and steroidogenesis. On day of synchronized ovulations, cows were assigned to shade (n=11) or no shade (n=12) management systems. Follicular development was monitored daily by ultrasonography until ovariectomy on Day 8 post estrus. At time of ovariectomy, dominant and second largest follicles were dissected from the ovary. Aromatase activity and steroid concentrations in dominant and subordinate follicles were measured. Acute heat stress had no effects on patterns of growth of first wave dominant and subordinate follicles between Days 1 and 7 of the cycle. Compared with shaded cows, the heat stressed cows did not have suppression of medium size (6 to 9 mm) follicles between Days 5 and 7. A treatment x follicle interaction was detected (P<0.01) for follicular diameter and fluid volume at Day 8. Dominant follicles in shade were bigger (16.4>14.5 mm) and contained more fluid (1.9>1.1 ml) than dominant follicles in no shade. Conversely, subordinate follicles in no shade were bigger (10.1>7.9 mm) and contained more fluid (0.4>0.2 ml) than subordinate follicles in shade. Concentrations of estradiol in plasma and follicular fluid were higher (P<0.01) in July than in September. Heat stress appears to alter the efficiency of follicular selection and dominance, and to have adverse effects on the quality of ovarian follicles.

Journal Article↗
PubMed2003

Short communication: presynchronization using a single injection of PGF2alpha before synchronized ovulation and first timed artificial insemination in dairy cows.

Conception to synchronized ovulation (Ovsynch) using injections of GnRH and PGF2alpha and timed artificial insemination has been shown to be maximized when the program is initiated 5 to 12 d after estrus. The objective of this double-blinded field trial was to assess the effect of one injection of PGF2alpha, 10 d before the Ovsynch program, on the probability of pregnancy at first insemination in lactating dairy cows. The hypothesis was that cows that underwent luteolysis in response to PGF2alpha would be between 5 and 8 d postestrus at the start of Ovsynch. In five commercial dairy herds in Ontario, Canada, at 52 +/- 12 d in milk, 506 cows were assigned at random to receive either one i.m. injection of 500 microg of cloprostenol or saline. Ten days later, all cows received 100 microg of GnRH i.m., followed in 7 d by 500 microg of cloprostenol i.m. and 100 microg of GnRH i.m. 48 h later. All cows were artificially inseminated 0 to 20 h after the second injection of GnRH, without regard to detection of estrus. Pregnancy was diagnosed by transrectal palpation at least 35 d after insemination. The probability of pregnancy after first insemination was modeled with logistic regression, accounting for the correlation of cows with herd and the effect of season of calving. There was no difference in pregnancy risk between cows that received PGF2alpha presynchronization and controls (37.3 and 36.6%, respectively; odds ratio = 1.03, 95% confidence interval, 0.88 to 1.20). Parity and days in milk at insemination were not significant covariates.

Animals↗
PubMed2003

A progesterone-based timed AI protocol more effectively prevents premature estrus and incomplete luteal regression than an Ovsynch protocol in lactating Holstein cows.

The objective of this study was to evaluate pregnancy rates in lactating Holstein cows treated with an Ovsynch protocol (GnRH-PGF(2alpha)-GnRH) or a progesterone-based timed AI (TAI) protocol, and to determine the factors that may influence pregnancy rate following protocol treatment. In experiment 1, lactating Holstein cows were randomly assigned to three treatments: (1) an injection of GnRH (Day 0), an injection of PGF(2alpha) on Day 7, a second injection of GnRH on Day 9, and TAI 16h after the second GnRH injection (GPG group, n = 34); (2) insertion of a CIDR intravaginal progesterone (1.9g) device combined with a capsule containing 10mg estradiol benzoate (Day 0), an injection of PGF(2alpha) and removal of the device on Day 7, an injection of GnRH on Day 9, and TAI 16h after the GnRH injection (CPG group, n = 34); (3) an injection of PGF(2alpha) after confirming the presence of CL by ultrasonographical observation and artificial insemination at estrus (AIE) (P group, n = 75). The pregnancy rate after TAI following the CPG protocol (41.2%) was higher (P<0.05) than that after TAI following the GPG protocol (20.6%) and that after AIE (20.0%). In experiment 2, lactating Holstein cows were randomly assigned to two treatments: a GPG group (n = 31) and a CPG group (n = 31). The GPG and CPG protocols were identical to those used in experiment 1. The proportion of cows with premature estrus prior to injection of PGF(2alpha) and with incomplete luteal regression tended (P = 0.056) to be or were greater (P<0.05) in the GPG group (4/31, 8/31) than in the CPG group (0/31, 2/31), respectively. Average diameters of dominant follicles (1.5+/-0.1mm versus 1.4+/-0.1mm) on Day 7 and preovulatory follicles (1.8+/-0.1mm versus 1.6+/-0.1mm) on Day 9, and the proportion of cows with synchronized ovulation by 40h after the second GnRH injection were not different (81.5% versus 87.1%, P>0.05) between groups, respectively. We conclude that the pregnancy rate after TAI following the CPG protocol was higher than that after TAI following the GPG protocol, probably due to a decreased incidence of premature estrus and incomplete luteal regression.

Administration, Intravaginal↗
PubMed1993

In synchronized pigs, the duration of ovulation is not affected by insemination and is not a determinant for early embryonic diversity.

The duration of ovulation (i.e., the time interval between the ovulation of the first and the last follicle in a sow during an estrus) is said to be related to embryonic diversity, which in turn is related to embryonic mortality. The relationship between the duration of ovulation and within-litter early embryonic diversity and the influence of insemination on the duration of ovulation were studied. To determine whether ovulation assessment (transrectal ultrasonography) influenced early embryonic development, control sows were not scanned. Multiparous cyclic sows with an exogenously induced estrus were used. Ovulation detection by means of transrectal ultrasonography did not influence fertilization rate, accessory sperm count, early embryonic development or early embryonic diversity, and, therefore, ultrasonography appears to be a worthwhile method for studying the time and duration of ovulation. Insemination did not influence (P>0.05) the duration of ovulation, in sows which ovulated between 39 and 49 hours after hCG injection. The duration of ovulation (mean+/-SD(range)) was 2.4+/-0.7 (1.1 to 4.0) hours in 15 sows which were artificially inseminated at 22 and 30 hours after hCG injection. In 8 noninseminated sows, the duration of ovulation was 2.3+/-0.5 (1.5 to 3.3) hours. The duration of ovulation was not related to embryonic diversity (SD of the number of nuclei or the number of cell cycles of embryos in a litter) at 114 to 121 hours after ovulation. Thus, a difference of up to 3 hours in the duration of ovulation does not seem to be an important determinant of variation in embryonic diversity between sows.

Journal Article↗
PubMed1976

Adenylyl cyclase activities in ovarian tissues. III. Regulation of responsiveness to LH, FSH, and PGE1 in the prepubertal, cycling, pregnant, and pseudopregnant rat.

In the ovaries of prepubertal rats, responsiveness of adenylyl cyclase (AC) to LH, FSH, and PGE1 is acquired at day 10, coinciding with the appearance of the ability to produce steroids in response to gonadotrophins. The activity and responsiveness of AC on day 11 were similar to those at puberty on day 40 and relatively stable in between. In the follicles of the cycle, the responsiveness of AC to LH and FSH was poor (ca 2-fold stimulation) on metestrus and diestrus, and became high (ca 10-fold stimulation) between 1000 h of diestrus and 1000 h of proestrus. Thereafter, the system slowly became desensitized to LH and FSH, being unresponsive by the morning of estrus. Nembutal injected at 1230 h and again at 1500 h on proestrus blocked ovulation and prevented the decline in LH- and FSH-stimulated AC activity. In the CL of the cycle, the AC was unresponsive to LH on day 1 (estrus), became responsive by the morning of day 2 (metestrus), and maintained responsiveness throughout that day. Thereafter, the responsiveness and basal AC activity declined rapidly. In the CL of pregnancy, LH-stimulated AC was indistinguishable from that of the CL of the cycle during days 1 and 2, then increased steadily until day 9, showing a transient decrease on days 10 and 11, followed by a sharp rise to maximal activity on days 15 and 16. Thereafter, activity declined as parturition approached. In the CL of pseudopregnancy (PSP), LH-stimulated AC was very similar to that of the CL of pregnancy during the first 11 days. Thereafter, it decreased coincident with the termination of PSP. Injections of PRL (100 mug SC twice daily, from metestrus through estrus, and from proestrus through proestrus) or estradiol-17 beta (20 mug, SC at 1230 h on metestrus) resulted in "rescue" of the CL-AC system, which remained at metestrus levels when measured on the days of expected proestrus or estrus. Injections of pregnant mare serum gonadotrophin into prepubertal rats at day 26 (3 IU, iv), induced by day 28 a highly responsive AC system in follicles, with activities equivalent to those found in Graafian follicles on proestrus. By day 29, synchronous ovulation had occurred with a concomitant loss of LH-stimulated AC such as seen in the 1-day-old CL of mature rats. Our results suggest that the LH-sensitive AC may be indicative of the final development of ovulability of the follicles, and that it may correlate with the functional capacity of CL during various reproductive stages of the rat.

Adenylyl Cyclases↗
PubMed1991

[Estradiol, progesterone and cyclic nucleotides in the fluid of persistent follicles and luteal phase follicles in the estrus cycle in cows].

The objective of the present study was to compare the concentrations of 17 beta-estradiol, progesterone, cyclic adenosine monophosphate and cyclic quinosine monophosphate in the largest follicles of cows that persist for seven days after insemination following the preceding synchronization of oestrus and superovulation and in follicles of the luteal phase of cycle (5th-10th days). Animals included in the experiment were selected on the basis of rectal examination. Synchronization of oestrus was achieved in 24 crossbreds of Slovak Pied x Lowland Black Pied breeds (SS x Nc) using two doses of cloprostenol of Czechoslovak provenience Oestrophan Spofa, 500 micrograms in each, within 11 days. Serum gonadotrophin at the amount of 2500 I. U. was administered forty-eight hours before administration of the second dose PGF2 alpha. Experimental animals were inseminated after 72 hours. On the 7th day after mating the cows were killed at a slaughterhouse. Evaluated were only the ovaries of the 14 cows in which the persistent large follicles occurred. Ovaries of the 13 control cows in the luteal phase between the 5th-10th days were obtained at the slaughterhouse by the method after Ireland et al. (1980). Correct determination of the phase of sexual cycle was substantiated by determination of progesterone concentrations in blood serum. Follicular fluid was obtained from the largest follicles by aspiration and centrifuged in a cooled centrifuge at 3000 G. The concentrations of 17 beta-estradiol and progesterone in follicular fluid were determined using kits from URVJT at Kosice, designated RIA-test-ESTRA (SI-125-9) or RIA-test-Prog (SI-125-6).2+ persistent follicles (9.15 +/- 5.47 nmol.l-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Spontaneous multiple ovulation in the mare and its effect on the incidence of twin embryo collections.

Records from 183 nonlactating mares that experienced spontaneous multiple ovulation were examined to determine if: 1) double ovulations are as likely to be unilateral as bilateral; 2) the interval between two ovulations is shorter when the ovulations are unilateral than when they are bilateral; 3) the mean diameter of the two follicles on the day prior to ovulation is less when the ovulations are synchronous and unilateral; 4) for both unilateral and bilateral ovulation, twin embryos are more likely to be detected when double ovulations are asynchronous; and 5) for both synchronous and asynchronous ovulations, twin embryos are more likely to be detected when the ovulations are bilateral. Mares were teased daily with a stallion and follicular development was assessed daily during estrus by ultrasonography. Mares were inseminated daily during estrus and embryo recovery attempts were performed 6 to 7 d post ovulation. Double ovulations occurred as frequently from the same, as from opposite ovaries. The interval between the double ovulations was not shorter (P > 0.05) in unilateral versus bilateral ovulations. In addition, size of the largest and second largest preovulatory follicles was not altered (P > 0.05) by type of ovulation (bilateral vs unilateral) or synchrony of ovulation. Synchrony of ovulations had no affect (P > 0.05) on the incidence of twin embryos recovered. However, more (P < 0.05) twin embryos were recovered from bilateral ovulators compared to unilateral ovulators.

Journal Article↗