Effects of maternal undernutrition on the hypothalamic-pituitary-gonadal axis function in female sheep offspring.

A study was conducted to evaluate the effects of maternal undernutrition on the hypothalamic-pituitary-gonadal axis in female sheep offspring. Pregnant ewes were fed to 100% throughout pregnancy (Control) or to 50% from 0 to 30 (R1) or from 31 to 100 days of gestation (R2). Female lambs were selected and fed to appetite throughout the study. At 2, 5.5 and 10 months of age a GnRH challenge was conducted. At the age of 10 months lambs were synchronized and blood samples were collected at 3 h intervals for 72 h following sponge removal. At slaughter (10 months) ovaries were removed and examined macroscopically. Maternal undernutrition did not affect the time of the onset of puberty, defined as the first increase in plasma progesterone concentrations >or=1 ng/ml. The magnitude of the pre-ovulatory gonadotrophin surge and the time to surge were unaffected by treatment. The LH and FSH response to GnRH challenge did not differ between groups at 2 and 5.5 months but at 10 months of age a higher (p < 0.05) FSH response was found in R1 group. Although the total number of visible follicles and corpora lutea did not differ between groups, a significant higher (p < 0.05) number of small (2-3 mm diameter) follicles in R1 group and a significant lower number (p < 0.05) of corpora lutea with diameter 8-11 mm and not even one with diameter >12 mm were detected in the ovaries of R2 lambs. In conclusion, maternal undernutrition during the first month of pregnancy resulted in increased pituitary sensitivity to GnRH and increased number of small follicles in the ovary, while during mid to late gestation resulted in a reduction of large corpora lutea in female offspring.

Combined administration of gonadotropin-releasing hormone, progesterone, and meloxicam is an effective treatment for the repeat-breeder cow.

In practice, the etiologic treatment of the repeat-breeder cow is nearly infeasible. In this study, we tested the hypothesis that a combined treatment would benefit the conception rate of repeat-breeder cows. The components of this regimen target ovulation defects, late progesterone (P4) rise, and premature luteolysis. In a 5-year period, 402 repeat-breeder cows were divided in five groups, and treatment regimens consisted of the following: gonadotropin-releasing hormone (GnRH; Group 1, n=115, 0.012mg buserelin im 4 to 6h before artificial insemination); P4 (Group 2, n=51, 100mg P4 intravaginally, on Days 5 to 7); meloxicam (Group 3, n=31, 0.5mgkg(-1), 24h(-1) melomicronxicam sc, on Days 16 to 18); GnRH+P4+meloxicam (Group 4, n=98); and no treatment (Group 5, control, n=107). Artificial insemination was conducted only after overt estrus; thereafter, the duration of the estrous cycle was assessed in all cows that were detected to return to heat. The conception and pregnancy rate was compared among groups. The proportion of cows that returned to estrus after artificial insemination did not differ among groups; the duration of estrous cycle was the shortest in Group 1 and the longest in Group 4. In Group 4, pregnancy rate was higher (P<0.05) than that of Groups 1 and 5 (35.71% vs. 20.00% and 17.76% for Groups 4, 1, and 5, respectively), but though numerically higher, it did not differ statistically from that of Groups 2 (27.45%) and 3 (22.58%). Our results imply that a multifaceted protocol has to be applied for the successful treatment of the repeat-breeder cow.

Impact of maternal undernutrition on the hypothalamic-pituitary-adrenal axis responsiveness in sheep at different ages postnatal.

Epidemiological and experimental data support the hypothesis of 'fetal programming', which proposes that alterations in fetal nutrition and endocrine status lead to permanent adaptations in fetal homeostatic mechanisms, producing long-term changes in physiology and determine susceptibility to later disease. Altered hypothalamic-pituitary-adrenal (HPA) axis function has been proposed to play an important role in programming of disease risk. The aim of the present study was to examine the effects of maternal nutrient restriction imposed during different periods of gestation on the HPA axis function in sheep, at different ages postnatal. Pregnant ewes were fed a 50% nutrient-restricted diet from days 0-30 (group R1, n = 7), or from days 31-100 of gestation (group R2, n = 7) or a control 100% diet throughout pregnancy, (Control, n = 8). Blood samples were collected at 10-day intervals from day 40 of gestation to term. Lambs were born naturally and fed to appetite throughout the study period. At 2, 5.5, and 10 months of age lambs were given an i.v. injection of corticotrophin-releasing hormone (CRH) and blood samples were collected at -15, 0, 15, 30, 60, 120, and 180 min postinjection. Maternal cortisol levels were significantly higher (P < 0.05) in group R1 compared with the other two groups, whereas maternal insulin levels were lower (P < 0.05) in group R2 compared with control. Birth weight of lambs was not affected by the maternal nutritional manipulation. The area under the curve for ACTH and cortisol response to CRH challenge was greater (P < 0.05) in lambs of group R1 at two months of age, whereas no difference was detected at the ages of 5.5 and 10 months. However, significantly higher (P < 0.01) basal cortisol levels were observed in lambs of R1 group at 5.5 months of age. There was no interaction between treatment and sex for both pituitary and adrenal responses to the challenge. A significant sex effect was evident with females responding with higher ACTH and cortisol levels at the age of 5.5 months (P < 0.01, P < 0.001 respectively) and with higher cortisol levels (P < 0.01) at 10 months of age than males. It is concluded that the HPA axis is programmable by altered nutrition in utero. The sensitivity of the axis to exogenous stimulation is enhanced during early postnatal life and attenuated with age, suggesting a role for the postnatal influences in resetting of the HPA axis and emphasizing the importance of identifying the impact of maternal undernutrition at several time points after birth.

Oestradiol concentration as a predictor of ovarian response in FSH stimulated ewe-lambs.

We investigated the prediction of ovarian response using oestradiol determination, in 37 gonadotrophin stimulated Karagouniko ewe-lambs. Ovarian stimulation was induced by serial FSH administrations, and laparoscopic follicular aspiration (OPU) was conducted 12h after the last FSH injection. Oestradiol concentration was assessed in six blood samples collected prior to each FSH injection and in one sample collected prior to follicular aspiration. According to ovarian response, ewe-lambs were allotted in three groups: good, L1 (n=17); moderate, L2 (n=10); and poor, L3 (n=10). Based on the data obtained from 28 (75%) randomly selected animals, a statistical model was designed and tested on the remaining nine lambs for its ability to predict the probability of good ovarian response. From the 2nd sample, oestradiol concentration was constantly higher in group L1 in comparison with L3 lambs (all p-values for the contrasts were

Oocyte pick-up in juvenile lambs affects neither onset of puberty nor their future fertility.

A study was designed to evaluate whether the time of onset of puberty and fertility of young ewe lambs would be affected by oocyte pick-up conducted in single or repeated sessions during the first months of lambs' live. Five groups of lambs from the Karagouniko breed were used (A-E each n=12). In group A no treatments were applied (control group) while, laparoscopical follicular aspiration (OPU) was performed early in the third, fourth and fifth month of lambs age (groups C-E, respectively). From the second to fifth month of their age, group B lambs were aspirated four times in monthly intervals. All lambs were weighed at birth, weaning, at second month and monthly thereafter until the eighth month of age. Progesterone priming and ovarian stimulation by serial FSH administrations proceeded each OPU session. To determine onset of puberty blood progesterone concentration was assayed in samples collected initially every week and after the seventh month of age twice weekly. From the seventh month a fertile ram was introduced in each group and oestrous behavior/mating was daily monitored and recorded. Pregnancy diagnosis was carried out by transabdominal ultrasound scanning 55 days after rams' removal. At the fourth and fifth month of age group B lambs were lighter (p<0.05) than controls, but this difference was later equalized. The time of onset of puberty did not differ between groups (p=0.069) and ranged between 224 and 270 days. Some animals (n=15) entered puberty with a full-length luteal phase having progesterone concentration greater than 1ng/ml, while others (n=32) exhibited one or two short luteal phases before luteal length restoration. During the first breeding season 41 animals were fertilized and maintained pregnancy to term, without noticeable differences between groups (p=0.555). During the second breeding season, all ewes were naturally served and lambed at the expected time. It is concluded that OPU in young dairy lambs does not affect the time of onset of puberty, the endocrine profile of the lambs and it does not compromise their future fertility even if it is applied at four successive months.

Luteal stage dependence of pituitary response to gonadotrophin-releasing hormone in cyclic dairy ewes subjected to synchronisation of ovulation.

Possible hormonal aberrations precluding conception or maintenance of pregnancy in dairy ewes subjected to ovulation synchronisation were investigated in this study. The pituitary response to exogenous gonadotrophin-releasing hormone (GnRH) was tested at different luteal stages in 36 ewes. Oestruses were synchronised by using progestagen-impregnated sponges and the animals were randomly allotted into one of three treatment groups (A, B and C; n = 12 for each). Treatments commenced on Days 4, 9 and 14 of the new cycle (oestrus was defined as Day 0). Ewes were given two GnRH injections, 5 days before and 36 h after a prostaglandin F2+/- (PGF2+/-) injection, and the animals were inseminated 12-14 h after the second GnRH injection (modified OVSYNCH). For luteinising hormone (LH) determination blood samples were withdrawn from six ewes of each group at the time of GnRH administration, and 30, 90, 180, 270 and 360 min later. Progesterone was assayed in samples taken every other day starting from oestrus and for 17 days after the second GnRH injection, and in an additional sample collected on the day of insemination. After the first GnRH injection, the LH concentration was higher in Group C than in Groups B and A (mean +/- s.d.: 64.8 +/- 10.0 ng mL(-1), 41.3 +/- 3.7 ng mL(-1) and 24.6 +/- 9.0 ng mL(-1), respectively; P < 0.05), whereas after the second GnRH injection a uniform LH release was found in all groups. PGF2+/- caused a significant decrease in progesterone (P4) concentration in all groups; however, at artificial insemination ewes that conceived had significantly lower P4 concentration in comparison with those that failed to conceive. As early as Day 5, pregnant animals had higher P4 concentrations than non-pregnant animals. Overall, 21 animals conceived (seven, nine and five ewes from Groups A, B and C, respectively). These results indicate that the proposed protocol is equally effective in inducing a preovulatory LH surge at any stage of the luteal phase, and that elevated P4 concentration along with a delayed P4 increase should be considered as a causative factor for inability to conceive.

Early pregnancy diagnosis in swine by direct radioimmunoassay for progesterone in blood spotted on filter paper.

A direct radioimmunoassay method for the measurement of progesterone in blood dried on filter paper has been developed for the early pregnancy diagnosis in sows, as well as for monitoring progesterone levels during the oestrous cycle. Pregnancy diagnosis was performed with 95 sows on Days 17-22 after artificial insemination (AI). The cut-off value for pregnancy diagnosis of 7.5 ng/ml was calculated (mean+/-2S.D.) from the progesterone concentrations measured on the same days from non-inseminated animals. There were 85 cases considered pregnant on the basis of progesterone concentration, leaving 10 animals non-pregnant. The accuracy for the positive cases was 98.8%. Two of the 10 sows considered as negative subsequently farrowed, giving an accuracy of 80%. The overall accuracy of the method was 96.8%. The blood-spot assay may be a useful tool for early pregnancy diagnosis in swine, with respect to sampling, simplicity, speed and accuracy.