Hormone concentrations temporally associated with contralateral and ipsilateral relationships between the CL and preovulatory follicle during the third follicular wave in heifers

Concentrations of circulating hormones after Day 14 (Day 0 = ovulation) were determined daily in 87 interovulatory intervals (IOIs) in heifers. The IOIs were grouped into four permutations according to an ipsilateral (Ipsi) or contralateral (Contra) relationship between the CL and the preovulatory follicle and two (2W) or three (3W) follicular waves per IOI. The number of IOIs per group differed (P < 0.005) from equality among the Ipsi-2W (n = 27), Contra-2W (n = 31), Ipsi-3W (n = 9), and Contra-3W (n = 20) groups. A continuous decrease in progesterone (luteolysis) began later (P < 0.05) in the Contra-3W group (Day 18.0 ± 0.4) than in each of the Ipsi-2W (15.4 ± 0.2), Contra-2W (15.6 ± 0.2), and Ipsi-3W (16.2 ± 0.5) groups. Concentrations of LH and estradiol began to increase near the beginning of luteolysis in each group. A minor FSH surge that did not stimulate a major follicular wave developed in about 50% of the IOIs in each group, except that none were detected in the Ipsi-3W group. The minor FSH surge reached a peak about 4 days before ovulation and several days after wave 3 had emerged. The hypothesis that luteolysis begins earliest in two-wave IOIs, intermediate in three-wave IOIs with an ipsilateral CL/follicle relationship, and latest in three-wave IOIs with a contralateral relationship was supported. The hypothesis that a minor FSH surge occurs most frequently in association with three follicular waves was not supported.     

Effect of progesterone concentrations,follicle diameter,timing of artificial insemination,and ovulatory stimulus on pregnancy rate to synchronized artificial insemination in postpubertal Nellore heifers

Two experiments were designed to evaluate the effects of treatments with low versus high serum progesterone (P₄) concentrations on factors associated with pregnancy success in postpubertal Nellore heifers submitted to either conventional or fixed timed artificial insemination (FTAI). Heifers were synchronized with a new controlled internal drug release device (CIDR; 1.9 g of P₄ [CIDR1]) or a CIDR previously used for 18 days (CIDR3) plus 2 mg of estradiol (E₂) benzoate on Day 0 and 12.5 mg of prostaglandin F2α on Day 7. In experiment 1 (n = 723), CIDR were removed on Day 7 or 9 and heifers were inseminated after estrus detection. In experiment 2 (n = 1083), CIDR were all removed on Day 9 and FTAI was performed either 48 hours later in heifers that received E₂ cypionate (ECP) on Day 9 (0.5 mg; E48) or 54 or 72 hours later in conjunction with administration of GnRH (100 μg; G54 or G72). Synchronization with CIDR1 resulted in greater serum P₄ concentrations and smaller follicle diameters on Days 7 and 9 in both experiments. In experiment 1, treatment with CIDR for 9 days decreased the interval from CIDR removal to estrus (Day 7, 3.76 ± 0.08 days vs. Day 9, 2.90 ± 0.07; P < 0.01) and improved conception (Day 7, 57.1% vs. Day 9, 65.8%; P = 0.05) and pregnancy rates (Day 7, 37.6% vs. Day 9, 45.3%; P = 0.04). In experiment 2, treatment with ECP improved (P < 0.01) the proportion of heifers in estrus (E48, 40.9%^a; G54, 17.1%^c; and G72, 32.0%^b), but the pregnancy rate was not affected (P = 0.64) by treatments (E48, 38.8%; G54, 35.5%; G72, 37.5%). Synchronization with CIDR3 increased follicle diameter at FTAI (CIDR1, 11.07 ± 0.10 vs. CIDR3, 11.61 ± 0.10 mm; P < 0.01), ovulation rate (CIDR1, 82.8% vs. CIDR3, 88.0%; P < 0.01) and did not affect conception (CIDR1, 42.2 vs. CIDR3, 45.1%; P = 0.38) or pregnancy rates (CIDR1, 34.7 vs. CIDR3, 39.4%; P = 0.11). In conclusion, length of treatment with P₄ affected the fertility of heifers bred based on estrus detection. When the heifers were submitted to FTAI protocol, follicle diameter at FTAI (≤10.7 mm, 23.6%; 10.8–15.7 mm, 51.5%; ≥15.8 mm, 30.0%; P < 0.01) was the main factor that affected conception and pregnancy rates.     

Role of progesterone receptors during postpartum estrus in rats

We studied the role of progesterone receptor (PR) in the display of female sexual behavior during postpartum estrus in rats. Adult female rats were treated with the PR antagonist, RU486 (1.25 and 5 mg), 3 h after parturition and sexual behavior was evaluated throughout the first postpartum day. Estradiol and progesterone serum levels changed during the first 24 h postpartum. The highest estradiol and progesterone levels were found at 9 and 12 h postpartum, respectively. The predominant PR isoform in the hypothalamus and the preoptic area was PR-A during postpartum day. The content of PR-A increased at 6 h postpartum in the hypothalamus and the preoptic area, and decreased in both regions at 9 h. PR-B content only increased in the preoptic area at 12 h postpartum. The highest display of lordotic and proceptive behaviors were found at 12 h postpartum. The treatment with 1.25 and 5 mg of RU486 respectively reduced lordosis by 61% and 92% at 12 h postpartum. These results suggest that PR is essential in the display of postpartum estrus in rats.     

The effects of exclusion of progesterone or Day 0 GnRH from a GnRH,prostaglandin, GnRH + progesterone program on synchronization of ovulation in pasture-based dairy heifers

This study evaluated the effect of removing the GnRH injection on Day 0 or the progesterone (P4) device from a GnRH, PGF2α, GnRH (GPG) + P4 program on follicular dynamics and synchronization of ovulation in dairy heifers. Friesian and Friesian × Jersey heifers, in autumn 2009 (n = 35) and spring 2010 (n = 38), were randomly allocated to one of three estrus synchronization programs. The first group (GPG + P4) received 100 μg GnRH on Day 0, a P4-releasing intravaginal device from Days 0 to 7, 500 μg PGF2α on Day 7, and 100 μg GnRH on Day 9, followed by fixed-time artificial insemination 16 to 20 hours later. The program for group 2 (GPG) was the same as group 1 with the exclusion of the P4 device. Group 3 (P + G + P4) was treated the same as group 1, except for the absence of the GnRH treatment on Day 0. Ultrasonography was performed on Days 0, 1, 2, 3, and 7 and then at 12 hourly intervals on Days 9 to 11. Dominant follicle size was affected by both treatment and day, and there was also a significant interaction (P < 0.02) between treatment and day. Mean dominant follicle size was larger in the heifers treated with P + G + P4 on Days 1 to 3 than those treated with GPG + P4 (P < 0.02) and, on Day 2, than those treated with GPG (P = 0.005). However, on Day 7, mean dominant follicle size was larger in heifers treated with GPG than heifers treated with P + G + P4 (P = 0.03). The emergence of a new follicular wave was later in heifers treated with P + G + P4 than heifers, which received a GnRH injection on Day 0 (4.3 ± 0.7 days, compared with combined GPG + P4 and GPG 3.0 ± 0.3 days; P = 0.03). The proportion of heifers that ovulated within the first 48 hours after the Day 9 injection of GnRH was not affected by treatment (GPG, 81%; GPG + P4, 84%; and P + G + P4, 100% [including early ovulation]; P = 0.11). The timing of the ovulation was not different between treatments (P = 0.97).     

Intraovarian effect of dominant follicle and corpus luteum on number of follicles during a follicular wave in heifers

The intraovarian relationships among dominant follicle (DF), corpus luteum (CL), and number of follicles between Days 0 to 5 (Day 0 = ovulation) in wave 1 (n = 65 waves) and Days 9 to 13 in wave 2 (n = 62) were analyzed in separate experiments in Bos taurus heifers. Ovaries were grouped into intraovarian patterns of DF–CL, DF alone, CL alone, and neither DF nor CL. In wave 1, the pattern frequencies of DF–CL or neither DF nor CL (34% each) were greater (P < 0.0004) than for DF alone or CL alone (16% each). The number of growing follicles ≥5.0 mm, was greater (P < 0.0001) in ovaries with the DF, even when the DF was removed from the tally (P < 0.03). In a factorial analysis of wave 1, there was a positive main effect of DF (3.9 ± 0.2 vs. 2.2 ± 0.2 follicles; P < 0.0001), but the main effect of CL and the interaction of DF and CL were not significant. In a factorial analysis of wave 2, there were more (P < 0.0001) follicles greater than 6 mm in ovaries with a DF when the DF was included and an approaching difference (P < 0.09) when the DF was excluded. The main effect of CL and the interaction of DF and CL were not significant. The hypothesis that both the DF and CL have a positive intraovarian effect on number of follicles in waves 1 and 2 was only partly supported; the DF, but not the CL, had an effect in the factorial analyses. Previous reports in cattle and sheep of a positive intraovarian effect of CL on number of follicles are questionable in that location of the DF was not considered.     

Human chorionic gonadotropin affects original (ovulatory) and induced (accessory) corpora lutea,progesterone concentrations,and pregnancy rates in anestrous dairy goats

Two experiments were conducted in acyclic Alpine (A) and Saanen (S) goats that received intravaginal sponges containing 60 mg of medroxyprogesterone acetate for 6 days, as well as 200 IU of eCG and 30 μg d-cloprostenol i.m. 24 h before sponge removal. On day 7 (day 0 = onset of synchronized estrus), all goats were randomly divided into two groups: animals treated with 300 IU of hCG i.m. (hCG; Exp.1: n = 8A; Exp.2: n = 75A + S) and untreated controls (Control; Exp.1: n = 8A; Exp. 2: n = 70A + S). In Exp.2, all goats were artificially inseminated. Transrectal ovarian ultrasonography and blood collection were done on days 7, 10, 13, 17, and 21 (Exp.1), and pregnancy detection on day 60 (Exp.2). Estrus and ovulations occurred in five hCG and seven Control animals. Accessory CL (aCL) were detected in all hCG does. The total luteal area of ovulatory corpora lutea (oCL) increased (P < 0.05) on day 10 in hCG does and remained greater (P < 0.05) than in Control until day 21. Total and high-velocity color Doppler area were greater (P < 0.05) for oCL of hCG does on days 13 and 17. Progesterone concentrations were greater (P < 0.05) in hCG does from days 13 to 21 and related directly to the total luteal and oCL area for the duration of the study in all does. The pregnancy rate was higher (P < 0.05) in hCG than in Control by 22.5 %. Human chorionic gonadotropin given on day 7 of the synchronized estrous cycle positively affected CL function and pregnancy rates in seasonally anovular dairy goats.     

Effect of progesterone administration on the ovarian response to superovulatory treatments in cattle

To evaluate ovarian response in Angus cows previously treated with progesterone (P4), animals were randomly assigned to two groups: T600 group (n=14), 600 mg of P4/day. P4 was injected from days 3 to 7 of the estrous cycle. On day 7, superovulatory treatments began. The control group (n=12) was given vehicle only. The superovulatory treatments in the control group began on days 7-9 of the estrous cycle. The superovulatory total treatment dose of 400mg NIH FSH P1 was given twice a day over a 4-day period. Ultrasonography of the ovaries was conducted 3 days preceding the initiation of superovulatory treatment, every 24h. In both groups, an additional ultrasonographic evaluation was made at 24h after the end of superovulatory treatment. Blood samples were collected 4 days preceding the initiation of superovulatory treatment, every 24h. Additional samples were taken from the P600 group for 12 day after of initiation of superovulatory treatment every 24h, except on the fifth day after the initiation of superovulatory treatment. In the P600 group, P4 concentrations were greater than in the control group (P<0.01) and remained over 1 ng/ml up to day 11 after beginning of superovulatory treatment. The diameter of the dominant follicle was larger in the animals of the control group (P<0.01). Cows of the P600 group had a greater number of Class I (3-4mm) follicles (P<0.01). A significant day and treatment effect (P<0.01) were observed in Class II (5-9 mm) follicles. Effects due to treatment on the number of Class III follicles (P<0.05) were observed. In the P600 group, no estrous post-superovulatory was observed and there were no ovulations that occurred. Conversely, 100% of the cows of the control group showed estrous. In the P600 group, there were a greater number of Class III follicles (P<0.01) and a lesser number of Class II follicles (P<0.05) at 24h after the end of superovulatory. In the control group, 66.7% of the cows responded to superovulatory treatments. In conclusion, the daily administration of 600 mg of P4, from days 3 to 7 of the estrous cycle, produces an increase of plasma concentrations of this hormone from day 4, resulting in changes in follicular dynamics (absence of follicles greater than 10mm of diameter and an increase of the population of Class I follicles). As to the ovarian stimulation using Folltropin V in animals receiving a daily injection of 600 mg of P4 from days 3 to 7 of the estrous cycle, a greater population of follicles>or=10mm developed by 24h after superovulatory treatments were completed.     

Effects of exogenous progesterone and cloprostenol on ovarian follicular development and first ovulation in prepubertal heifers

The objective of this study was to determine the effects of progesterone and cloprostenol (a PGF_2α analogue) on ovarian follicular development and ovulation in prepubertal heifers. In Experiment 1, crossbred Hereford heifers (Bos taurus; 10 to 12 mo old, 255 to 320 kg) were assigned randomly to three groups and given (1) an intravaginal progesterone-releasing insert (CIDR; P group, n = 13); (2) a CIDR plus 500 μg cloprostenol im (PGF_2α analogue) at CIDR removal (PPG group, n = 11); or (3) no treatment (control group, n = 14). The CIDR inserts were removed 5 d after follicular wave emergence. Progesterone-treated heifers (P and PPG groups) had a larger dominant follicle than that of the control group (P = 0.01). The percentage ovulating was highest in the PPG group (8 of 11, 73%), intermediate in the P group (4 of 13, 31%), and lowest in the control group (1 of 14, 7%; P < 0.02). In Experiment 2, 16 heifers (14 to 16 mo old, 300 to 330 kg) were designated to have follicular wave emergence synchronized with either a CIDR and 1 mg estradiol benzoate im (EP group, n = 8) on Day 0 (beginning of experiment) or by transvaginal ultrasound-guided ablation of all follicles ≥5 mm on Day 3 (FA group, n = 8). On Day 7, CIDRs were removed in the EP group, and all heifers received 500 μg cloprostenol im. Ovulation was detected in 6 of 8 heifers (75%) in both groups. In summary, the use of PGF_2α with or without exogenous progesterone treatment increased the percentage ovulating in heifers close to spontaneous puberty.     

Repeatability of 2-wave and 3-wave patterns of ovarian follicular development during the bovine estrous cycle

Characteristics predictive of a 2-wave versus 3-wave pattern of ovarian follicular development during the interovulatory interval (IOI) were examined by ultrasonographic monitoring of 91 IOIs from 31 beef heifers. Repeatability of the wave pattern within individuals and the effects of season and age were determined using a subset of 75 IOIs from 15 heifers examined for multiple IOIs. The 2-wave pattern was detected in 62 of 91 (68%) IOIs, and the 3-wave pattern was detected in 29 of 91 (32%) IOIs. The preponderance of the 2-wave versus 3-wave pattern (P < 0.05) was not influenced by season (P = 0.61) but was even greater in the more mature age group (P = 0.02). The majority of IOIs ≤21 d was of the 2-wave pattern (88%; P < 0.05), whereas the majority of IOIs ≥22 d was of the 3-wave pattern (78%; P < 0.05). The proportion of nonalternating patterns (repeatability) was more than twofold greater than the proportion of alternating patterns (70% vs. 30%; P < 0.01). This relationship was consistent among seasons (P < 0.01) and even more marked in the more mature age group (P = 0.01). Emergence and follicular dominance of Wave 2 were delayed (P < 0.01), and the onset of corpus luteum regression was earlier (P < 0.01) in 2-wave versus 3-wave IOI. In conclusion, the duration of the IOI was predictive of the wave pattern, and the pattern was repeatable within individuals. Factors influencing the period of follicular dominance of Wave 1 in 2-wave versus 3-wave IOI may be responsible for regulating the wave pattern and may be associated with heifer maturity or relative nutritional demand during the postpubertal period. The impact of greater follicular attrition recorded in 3-wave versus 2-wave IOI on ovarian depletion and reproductive senescence is worthy of critical evaluation.     

Effect of restraint stress on plasma concentrations of cortisol, progesterone and pregnancy associated-glycoprotein-1 in pregnant heifers during late embryonic development

The aim of the present study was to evaluate the effect of restraint stress, which is commonly practised in the field, on plasma concentrations of cortisol, progesterone (P4) and bovine pregnancy-associated glycoprotein-1 (boPAG-1) in pregnant heifers between Days 30 to 40 of gestation. Twelve Holstein-Friesian heifers between Days 30 (Day 0 of experiment) and 40 (Day 10 of experiment) of pregnancy in a Hungarian dairy farm were used in the present study. The heifers were exposed to an acute stressor consisting of immobilisation (restraint stress) in a crush for 2 h (Group 1, n = 6) on Day 2 (Hour 48) and for 2 × 2 h (Group 2, n = 6) on Days 2 and 3 (Hour 72) of the experiment.Transrectal ultrasonography (7.5 MHz linear-array rectal transducer) was performed daily from Day 0 to Day 10 of the experiment to detect embryonic heartbeat or the fate of the conceptus. Blood samples were withdrawn before each ultrasonographic examination. Additional blood samples were withdrawn by 1 and 2 h (at Hours 49 and 50 in Groups 1 and 2 and Hours 73 and 74 in Group 2) of the onset of applying the stressor. Plasma cortisol, P4 and boPAG-1 concentrations were measured by radioimmunoassay. Acute restraint stress significantly (P < 0.001) increased the plasma cortisol level in pregnant heifers at 1 h of the exposure to the stressor at Days 2 (48 h) and 3 (72 h) of the experiment. On the other hand, the restraint stress did not affect the concentration of P4 and boPAG-1 concentrations in both groups. In conclusion, restraint stress for 2 h during early pregnancy in heifers increased blood cortisol, but it did not affect the concentrations of P4 and boPAG-1 between Days 30 to 40 of gestation.     

Age-related dynamics of follicles and hormones during an induced ovulatory follicular wave in mares

An ovulatory follicular wave was induced by ablation of follicles ≥6 mm and treatment with prostaglandin F2α (PGF) on Day 10 (ovulation = Day 0). Follicle and hormone dynamics of the induced waves were compared among three age groups: young (5-6 y, n = 14 waves), intermediate (10-14 y, n = 16), and old (≥18 y, n = 15). During the common-growth phase of the induced wave (Days 12-17), diameter of the future ovulatory follicle was not different among ages, but the young group had more (P < 0.05) follicles that reached ≥10 mm. The number was correlated (r = +0.7; P < 0.0001) within mares between consecutive interovulatory intervals, indicating repeatability. Concentrations of LH increased in all age groups during Days 12-17, but were greatest (P < 0.002) in the young group and continued to be greater (P < 0.0001) throughout the ovulatory LH surge. During several days before Day −1, there were no age-related effects on systemic estradiol concentrations, diameter of the preovulatory follicle, or B-mode echo texture or color-Doppler signals of blood flow in the follicle wall. Interpretations were: (1) greater number of follicles in the young group reflected a greater follicle reserve, (2) greater LH concentrations throughout the ovulatory surge in the young group reflected a more positive response to an extraovarian/environmental influence after removal of the negative effect of progesterone, and (3) lower LH concentrations in the older groups were adequate for the preovulatory changes in the follicle.     

Effect of high progesterone concentrations during the early luteal phase on the length of the ovulatory cycle of goats

The effect of exogenous progesterone exposure early in the oestrous cycle on the duration of the interovulatory interval was studied in dairy goats. A controlled intravaginal drug release (CIDR-G) device was inserted for 5 days starting at day 0 (D0 group, n=6) or day 3 (D3 group, n=5) postovulation. A third group was composed of untreated control goats (control group, n=7). Daily transrectal ultrasound was carried out during the interovulatory interval to assess the ovarian dynamics. Oestrous behaviour was checked twice a day and serum progesterone levels were assayed in daily jugular blood samples. Treated goats showed two different responses. In three D0 goats and one D3 goat, progesterone concentrations fell immediately after CIDR withdrawal and this was followed by oestrus and ovulation between days 8 and 11 (short cycles). In the other three D0 goats and in four D3 goats the treatment significantly reduced the interovulatory interval (18.3+/-0.3 and 18.5+/-0.3 days, respectively) (shortened cycles) compared with the control group (20.0+/-0.2 days; P<0.05), but the intervals with progesterone concentrations over 1 ng/ml were not different (15.7+/-0.3, 15.8+/-0.7 and 16.0+/-0.5 days for D0, D3 and control goats, respectively). In all D0 goats with a short cycle response, the ovulatory follicle arose from the first follicular wave but in the D3 goat with a short cycle it arose from the second follicular wave. These results showed that premature progesterone exposure early in the ovulatory cycle of the goat affected its length inducing short or shortened cycles. The effect of progesterone could either affect luteotropic support of the corpus luteum (CL) and/or stimulate a premature release of the luteolysin.     

Effect of Lipopolysaccharide on Progesterone Production during Luteinization of Granulosa and Theca cells In Vitro

The aim of this study is to examine the effect of lipopolysaccharide (LPS) on progesterone production during luteinization of granulosa and theca cells isolated from bovine large follicles. Granulosa and theca cells isolated from large follicles of bovine ovaries were exposed to LPS under appropriate hormone conditions in vitro. Progesterone (P4) production in theca cells, but not granulosa cells, was decreased by long‐term exposure of LPS. Long‐term exposure of LPS suppressed the gene expression of luteinizing hormone receptor in theca cells. Although long‐term exposure of LPS did not affect the expression of steroidogenic acute regulatory protein (StAR) and 3β‐hydroxy‐steroid dehydrogenase (3β‐HSD) genes, it did inhibit the protein expression of StAR and 3β‐HSD in theca cells. These findings suggest that theca cells, rather than granulosa cells, are susceptible to LPS during luteinization and that LPS inhibits P4 production by decreasing protein levels of StAR during luteinization of theca cells.     

Effects of low versus physiologic plasma progesterone concentrations on ovarian follicular development and fertility in beef cattle

The objective of this study was to determine the effects of low versus physiologic plasma progesterone concentrations during the ovulatory wave on fertility in cattle. Suckled beef cows (Bos taurus; n = 129) and pubertal heifers (Bos taurus; n = 150) at random stages of the estrous cycle were given a luteolytic dose of prostaglandin F_2α (500 μg cloprostenol; PGF) twice, 11 d apart. Ten days after the second PGF treatment, cattle were given estradiol benzoate im (1.5 and 1.0 mg for cows and heifers, respectively) and a progesterone-releasing intravaginal device (Cue-Mate) with a single pod containing 0.78 g progesterone (Day 0). Cattle in the low-progesterone group (n = 148) received a luteolytic dose of PGF on Day 0, whereas those in the high-progesterone (i.e., physiologic plasma concentrations) group (n = 131) were allowed to retain their corpora lutea. On Day 8, the Cue-Mate was removed, and PGF was given to both groups. Fifty-four hours to 56 h later, cattle received 12.5 mg of porcine LH (pLH) im and were concurrently artificially inseminated. The dominant follicle in the low-progesterone group was larger (P < 0.001) than that in the high-progesterone group on the day of insemination (14.9 ± 0.3 mm vs. 12.7 ± 0.3 mm, mean ± SEM). At 7 d after ovulation, the low-progesterone group had a larger corpus luteum (24.5 ± 0.54 mm vs. 21.9 ± 0.64 mm, P < 0.01) and higher plasma progesterone concentration (4.0 ± 0.3 vs. 3.1 ± 0.2, P < 0.01) than that of the high-progesterone group. However, pregnancy rates did not differ (79 of 148, 53.4%, and 70 of 131, 53.4%) for low- and high-progesterone groups, respectively). In summary, low circulating progesterone concentrations during the growing phase of the ovulatory follicle resulted in a larger dominant follicle and a larger CL that produced more progesterone, with no significant effect on pregnancy rate.     

Effects of body weight loss on serum progesterone concentrations of non-lactating dairy cows

The objective was to evaluate serum concentrations of nonesterified fatty acids (NEFA), cortisol, insulin, and progesterone (P4) of dairy cows maintaining or mobilizing body weight (BW). Eleven non-lactating, non-pregnant, and ovariectomized Gir × Holstein cows were stratified by BW and body condition score (BCS), and randomly assigned to: 1) BW loss (six cows; LOSS) and 2) BW maintenance (five cows; MAINT). Treatments were achieved through a grazing schedule using three pastures. From Days −7 to 1 of the study, all cows were maintained in Pasture A (12 kg of dry matter/cow daily). From Days 2 to 30, LOSS cows were maintained in Pasture B (less than 1.0 kg of dry matter/cow daily), whereas MAINT cows were maintained in Pasture C (12 kg of dry matter/cow daily). However, from Days 3 to 30 of the study, cows from both treatments were regrouped daily into Pasture A from 0600 to 1200 h to allow LOSS cows to consume, on average, 4.5 kg/d of forage dry matter. On Day −66 of the study, all cows received an intravaginal drug releasing device containing 1.9 g of P4 (replaced every 14 d and removed on Day 3). Cow BW and BCS were assessed on Day 0 and 30 and blood samples were collected daily from Days 0 to 30 at 0600 and 1200 h. Changes in BW and BCS were greater (P ≤ 0.05) in LOSS cows compared to MAINT cows. Within samples collected at 0600 h, serum NEFA concentrations were often greater (P < 0.05) in LOSS cows compared to MAINT after Day 14. Serum P4 concentrations were greater (P < 0.05) on Days 21 and 22, and tended (P < 0.10) to be greater on Days 16, 23, and 24 of the study in LOSS cows compared to MAINT. In conclusion, BW loss was associated with increased circulating concentrations of P4 in non-lactating ovariectomized dairy cows; this was mainly attributed to fat mobilization and consequent release of P4 stored in adipose tissues.     

Influence of day of postpartum breeding on pregnancy rate, pregnancy loss rate, and foaling rate in Thoroughbred mares

Records (years 2005-2007) were analyzed from a Thoroughbred stud farm in central Kentucky. Data from all breeding cycles of foaling mares were tabulated (3184 cycles of 2003 foaling mares bred between 7 and 163 days postpartum). A multiple logistic regression model employing Bayesian statistics was used to adjust for factors that significantly affected outcome; odds ratios (ORs) for pregnancy rate, pregnancy loss rate, and foaling rate were determined to examine the influence of day of postpartum breeding on these parameters. Mares bred before Day 22 (Day 0 = day of foaling) postpartum had a decreased OR for becoming pregnant (P < 0.05); the median OR for becoming pregnant (1.00) was not reached until Day 46 postpartum. Mares bred before Day 13 postpartum had an increased OR for pregnancy loss (P < 0.05). The median OR for pregnancy loss did not decline below 1.00 until Day 78 postpartum. Mares bred before Day 20 postpartum had a decreased OR for producing a foal (P < 0.05). The median OR for producing a foal (1.00) was not reached until Day 75 postpartum. We concluded that fertility (in terms of a higher OR for becoming pregnant and a lower OR for pregnancy loss, resulting in a higher OR for producing a foal) continued to improve in Thoroughbred mares for approximately 2.5 mo postpartum. These findings are of importance to management strategies directed at early postpartum breeding, and explain some of the reported drift in subsequent foaling dates of Thoroughbred mares, despite management practices that employ early postpartum breeding.     

Effect of progesterone and medroxyprogesterone acetate on pregnancy length and litter size in mink

The objective of these studies was to determine the effect of progesterone and medroxyprogesterone injected at varying times post coitum on gestation length and litter size. During a 3-year period mink females of "Standard" strain were given progesterone at a dose 5 mg at 15 and 20 days in the first year and at 17-20 days in the second year, after the last mating. The respective control groups were given the vehicle. Medroxyprogesterone acetate was given in the second year at a dose of 4 mg at 14-19 days following the last mating and in the third year at a dose of 2 mg at 8 days after the last mating. The results on pregnancy length and litter size after progesterone injections in the experimental and respective control groups were as follows: 52.7 days and 4.3 kits, 51.3 days and 4.3 kits, 52.2 days and 5.8 kits, 50.2 days and 4.8 kits, 44.7 days and 5.6 kits, 46.0 days and 6.1 kits. A dose of 4 mg MPA resulted in the blockage of parturition in pregnant females. After administration of MPA at doses of 2 mg at 8 days following the last mating, the pregnancy length and litter size in the experimental group were: 48.0 days and 6.1 kits and in the control: 52.2 days and 4.8 kits.     

Effect of breeding season and pregnancy status on serum progesterone,sodium, potassium,copper and iron of estrous synchronized Aradi goat does

Eighteen out of 88 estrous synchronized Aradi goat does were randomly chosen to be bled during May–July (Out breeding season, n = 9) and during September–December (Within breeding season, n = 9). Estrous synchronization was applied by using a control internal drug release (CIDR) as a reproductive management regimen throughout the year. Nineteen days after CIDR insertion, a 500 IU eCG was injected (i.m.) and CIDR was removed. Does were subjected to fertile bucks 48-60 h after CIDR removal. Jugular blood samples were collected in non-heparinized Vacutainer tubes at 0 h just before CIDR insertion, every 3 days during CIDR insert, at day of CIDR removal, at incidence of estrus and mating, at day 1, 8 and 30 post mating. Data on pregnancy were recorded and serum levels of progesterone (P), sodium (Na), potassium (K), copper (Cu) and iron (Fe) were determined. Progesterone concentration was higher (p < 0.05) within (2.85 ± 0.15 ng/ml) than outside (2.37 ± 0.13 ng/ml) the breeding season. Pregnant does exhibited higher (p < 0.05) levels of progesterone (2.76 ± 0.17 ng/ml) than non-pregnant does (2.37 ± 0.10 ng/ml). No significant interaction was found between season and pregnancy status on progesterone concentration. A typical progesterone profile was found during treatment days, as levels of P increased during CIDR insertion and declined at CIDR removal and thereafter. Neither breeding season nor pregnancy status affected Na⁺ concentration. Contrariwise, mean levels of K⁺ was higher (p < 0.05) outside (148.34 ± 3.91 mg/L) than within (136.27 ± 3.91 mg/L) the breeding season. Pregnancy status did not influence K concentration. Sodium/potassium (Na⁺/K⁺) ratio was significantly (p < 0.01) higher within (30.29 ± 0.44) than outside (27.62 ± 0.44) the breeding season. On the contrary, pregnancy status did not affect this ratio. Iron concentrations neither affected by season nor pregnancy. Likewise, Cu concentrations were not affected by season, however Cu levels were higher (p < 0.05) in pregnant (147.75 ± 7.24 μg/L) than in non-pregnant (127.31 ± 5.03 μg/L) does.     

Duration of daily bull exposure on resumption of ovulatory activity in postpartum,primiparous, suckled,beef cows

The objective of this experiment was to determine if duration of daily bull exposure influences length of postpartum anestrus in primiparous, anovular, suckled, beef cows. The null hypotheses were that intervals from calving or the start of bull exposure (D 0) to resumption of ovulatory activity (OA), and proportions of cows that resumed OA during the experiment does not differ among cows exposed to bulls for 0 h, 6 h, or 12 h daily, and that there is no relationship between the duration of bull exposure and interval to resumption of OA in cows exposed to bulls for 0 h, 6 h, or 12 h daily. At 51.5 ± 2.3 d (±SE) after calving, cows were assigned randomly to be exposed for 12 h (BE12; n = 15) or 6 h daily (BE6; n = 14) to bulls, or not exposed to bulls (NE; n = 10) for 45 d. Interval from calving or from D 0 to resumption of OA was shorter (P < 0.05) and the proportion of cows that resumed OA during the experiment was greater (P < 0.05) for BE12 than for NE cows. Interval from D 0 to resumption of OA did not differ (P > 0.10) between BE6 cows and either BE12 or NE cows. However, interval from calving to resumption of OA was shorter (P < 0.05) for BE6 than NE cows. The proportion of cows that resumed OA did not differ (P > 0.10) between BE6 cows and BE12 cows; however, the proportion of cows that resumed OA during the experiment tended (P = 0.08) to be greater for BE6 cows than for NE cows. There was a linear relationship between intervals from calving (b₁ = −7.64 d/h; P < 0.05) and D 0 (b₁ = −3.3 d/h; P < 0.05) to resumption of OA and duration of daily bull exposure. Thus, the duration of bull-pheromone stimuli that cows perceive each day is related to when primiparous, postpartum, anestrous, suckled cows respond to this stimulus and undergo the physiological changes necessary to resume ovulatory activity.     

Effect of individual heifer oocyte donors on cloned embryo development in vitro

The aim of this study was to determine the effect of individual oocyte donors on cloned embryo development in vitro. Five Holstein heifers of varied genetic origins were subject to ovum pick up (OPU) once weekly. In total, 913 oocytes were recovered from 1304 follicles. A mean of 7.7+/-0.4 oocytes was recovered per session per animal. Individual mean oocyte production varied significantly in quantity but not in quality (morphological categories) among heifers. Oocytes from individual heifers were used as recipient cytoplasm for somatic cell nuclear transfer (SCNT). Cumulus cells, collected from a single Holstein cow genetically unrelated to the oocyte donor, were used as donor cells. Although the percentage of reconstructed embryos that started to cleave was nearly constant, the percentage of cleaved embryos that developed into blastocysts showed clear individual heifer variation (61%, 51%, 31%, 28% and 24%, respectively), with a mean of 38% showing blastocyst formation. In vitro fertilization (IVF) was also conducted with oocyte from the same heifers used in SCNT. A variation of blastocyst production among individual heifers was also shown in the IVF experiment, but the rank of oocyte donor based on the blastocyst rate was changed. In conclusion, individual oocyte donor may have an effect on cloned embryo development in vitro, which differed from the effect on IVF embryos.