Wave Dominant Follicle Research Articles

Temporal evaluation of follicular dynamics and endocrine patterns of Holstein (Bos taurus), Gir (Bos indicus), and Murrah (Bubalus bubalis) heifers kept under the same nutritional, management and environmental conditions

The objective of the study was to simultaneously compare ovarian follicular dynamics and endocrine parameters of taurine (Holstein; n = 14), zebuine (Gir; n = 5), and bubaline (Murrah; n = 15) heifers kept under the same environmental, nutritional and management conditions. Heifers were synchronized with two PGF treatments 14 days apart. Ovaries of cyclic heifers were scanned daily during two consecutive ovulations and blood samples were collected every 24 h from each animal. No significant difference was found for length of interovulatory interval, however, zebuine heifers presented a greater number of follicular waves, number of antral follicles on day of ovulation, and higher insulin concentration than the other two breeds. Taurine heifers had highest maximal diameter of first wave dominant and ovulatory follicles and CL volume. Taurine and bubaline heifer's dominant follicle of first wave had longer static and regression phases than zebuine heifers. Bubaline heifers presented overall lowest progesterone concentrations and CL volume, but higher IGF1 levels. No difference was observed between taurine and zebuine heifers regarding IGF1 concentration. Despite higher CL volume found in taurine heifers, no difference in mean progesterone concentration was observed between them and zebuine heifers. Insulin and IGF1 concentrations were greater in follicular phase than in luteal phase when breed was not evaluated. After evaluating the three breeds simultaneously, at the same nutritional and management status it is possible to conclude that each genetic group has a specific follicular development and endocrinology of the estrous cycle.

Effect of the locational relationship between the 1st wave dominant follicle and the corpus luteum on conception rate after embryo transfer: data analysis of 297 embryo transfers from a commercial embryo production program

The ovarian structures identified at the time of ET are important for the selection of recipients. In previous report, the first-wave dominant follicle, located ipsilateral to the corpus luteum on the ovary, was associated with reduced conception rate after artificial insemination. Thus, a similar locational relationship may affect conception rate during embryo transfer. Data from 297 transfers of fresh embryos to virgin heifers were analyzed aiming to check the effect of first-wave dominant follicle location in relation to the corpus luteum on conception rate using a multivariable logistic regression model with six confounders. The location of the first-wave dominant follicle in relation to the corpus luteum location had no significant effect on conception rate, suggesting that it is not necessary to consider the firstwave dominant follicle size and location in the ovaries for recipient selection.

Studies on Ovarian Follicular Dynamics and Steroid Profiles in Sahiwal Cattle

Background: Understanding of ovarian follicular dynamics and endocrine regulation is essential to design and use interventions to optimize reproductive efficiency. Bos indicus and Bos taurus cows have some differences in their follicular dynamics and ovarian steroidal hormones. The present study was planned to understand follicular dynamics vis-a-vis ovarian steroids profiles in Sahiwal cattle. Methods: The study was conducted in normal cyclic, pluriparous, non-lactating Sahiwal cows (n=7). Trans-rectal ultrasonography was performed to record the location, size, number of follicles and size of corpus luteum (CL) from the beginning, till the end of experiment. The dataset was used to characterize the follicular wave emergence, growth, regression, time of selection and ovulation of the dominant follicle in each cow. Result: Three Sahiwal cows showed two wave and four cows showed three wave estrous cycles with mean interovulatory length of 20.33±0.33 and 22.50±0.28 days, respectively. No significant difference was recorded in the maximum diameter of corpus luteum, P4 and E2 plasma levels between 2-wave and 3-wave estrous cycles. The peak progesterone values of 6.00±0.91 and 6.2±1.2 ng/ml and peak estradiol values of 15.83±0.60 and 14.31±0.44 ng/ml were recorded in 2-wave and 3-wave estrous cycle, respectively. The results showed that Sahiwal cows had 2-wave and 3-wave estrous cycle and the 3-wave estrous cycle had comparatively longer inter-ovulatory period and smaller maximum diameter of second wave dominant follicle than 2-wave estrous cycle.

Increased dietary energy alters follicle dynamics and wave patterns in heifers.

Understanding the impacts of nutrition on reproductive physiology in cattle are fundamental to improve reproductive efficiency for animals under different nutritional conditions. Starting on Day 0 (day of ovulation) until next ovulation, Holstein heifers (n = 24) were fed: low energy diet (ad libitum grass hay; LED) and high energy diet (ad libitum grass hay + concentrate supplement; HED). Heifers on HED gained more weight (average daily gain: 0.824 ± 0.07 vs 0.598 ± 0.09 kg/day) and had increased insulin concentrations. The dominant follicle of wave 1 in HED had greater growth rate overall from Days 0 to 8 and on Days 6-7 and 8-9 and started atresia later. The dominant follicle of wave 2 in HED had greater growth rate overall from Day 9 to 18 and on Days 14-15 and 15-16. In two-wave patterns, there was no difference in estradiol or progesterone concentrations but concentrations of FSH were lower in HED on Days 15 and 16. Estradiol concentrations increased earlier in two-wave patterns in association with earlier luteolysis. The frequency of two follicular waves was greater in HED than LED (11/12 vs 6/11; 92.7% vs 54.5%). In conclusion, an acute increase in dietary energy altered not only growth rate of the dominant follicle but also follicular wave pattern in heifers by increasing frequency of two follicular waves. The hypotheses were supported that an acute increase in dietary energy (1) prolongs growth period of dominant follicles and (2) alters follicular wave pattern in heifers.

Influence of ipsilateral coexistence of the first wave dominant follicle and corpus luteum on ovarian dynamics and plasma sex steroid hormone concentrations in lactating dairy cows treated with human chorionic gonadotropin.

We examined the effect of human chorionic gonadotropin (hCG) treatment 5 days after estrus on ovarian dynamics and plasma progesterone (P4) and estradiol (E2) concentrations when the first-wave dominant follicle (DF) was ipsilateral or contralateral to the corpus luteum (CL) in lactating dairy cows. Seventy cows were divided into two groups: (1) ipsilateral group (IG; n = 37), in which the first-wave DF was ipsilateral to the CL, and (2) contralateral group (CG; n = 33), in which the first-wave DF was contralateral to the CL. IG and CG were further subdivided into two groups: non-treatment group (IG, n = 18; CG, n = 19), and hCG treatment group: administrated 1500 IU of hCG 5 days after estrus (IG, n = 19; CG, n = 14). Blood sampling and ovarian examination were performed at 3, 5, 7, 9, 11, and 13 days after estrus. Mean diameter of the first-wave DF on Day 9 tended (P = 0.067) to be larger in IG than in CG in the non-treatment group. Mean diameter of CL and plasma P4 and E2 concentrations did not differ between IG and CG in the non-treatment and hCG treatment groups. Accessory CL development did not differ between IG and CG in the hCG treatment group. Our findings indicate that CL development and plasma P4 and E2 concentrations were not affected by the existence of the first-wave DF; however, first-wave DF development was affected by the existence of a CL in the same ovary.

Physiological characteristics and effects on fertility of the first follicular wave dominant follicle in cattle

The first follicular wave emerges soon after ovulation, and its dominant follicle (DF) develops during the first 8–10 days of the estrous cycle in cattle. And, the first-wave DF is a non-ovulatory follicle, because it develops during the first half of the estrous cycle simultaneously with the corpus luteum (CL), which produces and secretes progesterone. Regarding the characteristics of development and the mechanisms of deviation in the DF during the follicular wave, the first-wave DF has been well studied. However, the characteristics of the first-wave DF, such as growth, blood flow in the follicular wall, concentration of sex steroid hormones in the peripheral blood and follicular fluid, amounts of mRNA in granulosa cells, as well as the characteristics of the CL formed after the first-wave DF and the influence of the first-wave DF on fertility (conception rate), have not been well studied. Additionally, the first-wave DF synthesizes and secretes 17β-estradiol (E2), and plasma E2 concentration increases during the early stage of the estrous cycle. Consequently, there is a possibility that the first-wave DF might affect the fertility in cattle. In this review, to provide the new perspective on reproductive physiology in cattle, characteristics of the first-wave DF were examined in detail and its characteristics were compared with that of the second-wave DF. In addition, the locational effects of the first-wave DF and CL on conception rate are discussed.

Double ovulation rate of the first follicular wave follicles is higher in the first follicular wave dominant follicle in the ovary contralateral to the corpus luteum treated with human chorionic gonadotropin five days after estrus in lactating dairy cows.

We examined the effect of human chorionic gonadotropin (hCG) treatment on double ovulation rate of first-wave follicles five days after estrus in lactating dairy cows. Cows were divided into two groups: 1) Ipsilateral group (IG; n=35), in which the first-wave dominant follicle (DF) was ipsilateral to the corpus luteum (CL), and 2) Contralateral group (CG; n=30), in which the first-wave DF was contralateral to the CL five days after estrus, then 1,500 IU of hCG was administrated. Double ovulation rate was significantly higher in the CG (26.7%) than in the IG (2.9%). This study demonstrate that the double ovulation rate of first-wave follicles was higher in the first-wave DF located in the contralateral ovary to the CL.

Effects of human chorionic gonadotropin treatment after artificial inseminations on conception rate with the first follicular wave dominant follicle in the ovary ipsilateral to the corpus luteum in lactating dairy cows

We examined the effect of human chorionic gonadotropin (hCG) treatment 5 days after artificial insemination (AI) on conception rate when the first-wave dominant follicle (DF) in the ovaries was either ipsilateral or contralateral to the corpus luteum (CL) in lactating dairy cows. 577 cows from 4 dairy farms were divided into the following two groups 5 days after AI using transrectal ultrasonography: (1) the ipsilateral group (IG; n = 348), in which the DF was ipsilateral to the CL, and (2) the contralateral group (CG; n = 229), in which the DF was contralateral to the CL. IG and CG were further subdivided into two groups: non-treatment groups, which received no treatment (IG, n = 220; CG, n = 128), and hCG treatment group, that was administrated 1500 IU hCG 5 days after AI (IG, n = 143; CG, n = 86). Pregnancy was diagnosed by rectal palpation or transrectal ultrasonography from 53 to 67 days after AI. Conception rate was significantly (P < 0.01) higher in the hCG treatment group of IG (40.6%) than in the non-treatment group of IG (21.4%); however, there was no difference in the non-treatment (51.7%) and hCG treatment (43.0%) groups of CG. Parity, farm, days in milk at AI, interaction between the farm and hCG treatment and interaction between the farm and location of the first-wave DF and CL did not affect conception rate. Our results suggest that conception rate can be improved by administrating hCG only to cows with the first wave DF ipsilateral to the CL.

Inducing sub-luteal circulating concentrations of progesterone and persistent follicles in Holstein heifers and non-lactating cows using a modified CIDR device

Reducing progesterone from Controlled Internal Drug Release (CIDR) devices may allow for the comparison of contrasting steady state concentrations of progesterone (P4) in non-lactating dairy cows and heifers. This technical study was designed to determine if circulating P4 concentrations from the CIDR device could be reduced in cattle via ethanol extraction, and if reduced steady state concentrations of P4 would increase the percent of cows and heifers that developed a persistent follicle. Holstein heifers and non-lactating cows were treated with Ovsynch (100μg GnRH, 7 d later, 25mg dinoprost tromethamine, 2 d later, 100μg GnRH) to initiate a new cycle. Only heifers and cows that synchronized were included in this study. On d 7 of the newly induced estrous cycle, animals were assigned to three treatments all treated with new CIDRs as follows: CIDR-N, CIDR that was not manipulated; CIDR-W, CIDR immersed in water, or CIDR-E, CIDR immersed in a mixture of equal parts water/ethanol. All heifers and cows received 25mg dinoprost tromethamine at time of treatment to ensure regression of the d 7 corpora lutea (CL). Only data from heifers and cows having morphological CL regression observed with ultrasonography on d 1 and 2 following treatment, and with basal P4 concentrations (<0.15ng/mL) on d after CIDR removal, were considered in the final analyses (n =30). CIDR-E had lower circulating concentrations of P4 during the treatment period compared to CIDR-N and CIDR-W in cycling heifers and non-lactating cows and a significant interaction of treatment x d from CIDR insertion was observed. CIDR-W had lower P4 compared to CIDR-N in heifers, but not in cows. With the three treatments combined, non-lactating cows had lower circulating concentrations of P4 than heifers. The 1st wave dominant follicle became atretic followed by a new wave of follicles in 4 of 5 non-lactating cows and heifers treated with CIDR-N compared to 1 of 12 in the CIDR-E and 3 of 13 in CIDR-W treatments during the 7 d treatment period. In summary, reduced steady state serum concentrations of progesterone from a CIDR device resulted in continued growth of persistent follicles in cows and heifers compared to a non-manipulated CIDR device.

Stimulation of regressing subordinate follicles of wave 2 with a gonadotropin product in heifers

The recovery of regressing wave-2 subordinate follicles was studied by treating heifers with a gonadotropin product that had about 84% and 16% of follicle-stimulating hormone and luteinizing hormone activity, respectively. A treated group (n = 8) received a single dose of 50 mg (2.5 mL) of the gonadotropin product, and a control group (n = 8) received 2.5 mL of saline vehicle. The group assignment of heifers was not known to the ultrasonographer who tracked the follicles and measured follicle diameters. Follicle measurements began on the day of expected follicle deviation in wave 2 (largest follicle closest to 8.5 mm), and treatment (hour 0) was given on Day 13.4 ± 0.2 (Day 0 = ovulation) when the dominant follicles of waves 1 and 2 were 14.1 ± 0.3 mm and 10.7 ± 0.1 mm, respectively. Subordinate follicles of wave 2 that had regressed to a 3-mm category (3.0–3.9 mm) or 4-mm category by hour 0 decreased in diameter for at least 48 h before hour 0, whereas follicles that were in the 5-mm or 6-mm categories at hour 0 did not change significantly in diameter during the previous 48 h. About 55% of the follicles that had regressed to the 3-mm and 4-mm categories at hour 0% and 78% of the follicles in the 5-mm and 6-mm categories increased in diameter after gonadotropin treatment, whereas follicles in the control group continued to decrease (regress) in diameter. The follicles for each of the 4 diameter categories were greater (P < 0.05) in diameter 9 h after treatment in the treated group than in the control group. The dominant follicle of wave 1 and the largest subordinate follicle of wave 2 in the treated group also increased in diameter so that diameter was greater (P < 0.05) than in the controls at hour 9. The results demonstrated that subordinate follicles of wave 2 that had decreased in diameter (regressed) for at least 48 h retained the capability to recover as indicated by a diameter increase when exposed to a gonadotropin product.

Follicular fluid and serum metabolites in Holstein cows are predictive of genetic merit for fertility.

The aims of the present study were to: (1) characterise the metabolome of follicular fluid and serum in dairy cows with similar genetic merit for milk production but with extremes of good (Fert+) or poor (Fert-) genetic merit for fertility; and (2) identify potential biomarkers of dairy cow fertility. Follicular fluid from the first wave dominant follicle and serum were collected on Day 7 of the oestrous cycle. The most pronounced effect of genotype was noted in the serum, where the abundance of total polyunsaturated fatty acids and n-6 polyunsaturated fatty acids was greater in Fert+ cows, and the abundance of total saturated fatty acids was greater in Fert- cows. The abundance of nine fatty acids (arachidic acid, heneicosanoic acid, myristic acid, behenic acid, myristoleic acid, heptadecenoic acid, cis-11-eicosanoic acid, nervonic acid and γ-linolenic acid) in follicular fluid was affected by genotype. Concentrations of cysteine, leucine, ornithine, proline and tyrosine in follicular fluid, and asparagine, creatinine, cysteine, methionine, proline and valine in serum, were also affected by genotype. Receiver operating characteristic curve analysis indicated that the follicular fluid and serum fatty acids and follicular fluid amino acids that were significantly affected by genotype were highly predictive of fertility genotype.

Temporality of two-way functional coupling between FSH and follicles in heifers

The intervals from removal of FSH suppressants by follicle ablation to an increase in FSH and from an increase in FSH to an increase in follicle diameter were determined hourly during follicular wave 1 in a follicles-intact group (n = 7) and a follicles-ablated group (n = 20). Follicles other than the largest subordinate follicle of wave 1 (SF1) were ablated when the dominant follicle of wave 1 (DF1) was about 11 mm (hour 0) and FSH concentration was basal. In an ablated-regressed subgroup (n = 5), SF1 diameter decreased constantly during hours 0 to 8. In an ablated-maintained subgroup (n = 15), SF1 decreased for 2 or 3 hours and then increased (n = 11) or increased constantly (n = 4). Average diameter of SF1 during 8 hours was greater (P < 0.01) in the maintained subgroup (8.3 ± 0.07 mm) than in the regressed subgroup (7.3 ± 0.09 mm). Concentration of FSH increased (P < 0.02) similarly between the two ablated subgroups but did not change during the 8 hours in the follicles-intact group. In each wave in the ablated-maintained subgroup with a decrease and then an increase in SF1 diameter (n = 11), the SF1 increase was preceded by an FSH increase. The interval from hour 0 (removal of source of FSH suppressants) to the beginning of an increase in FSH was 0.8 ± 0.3 hours. The interval from the beginning of an FSH increase to the beginning of an SF1 diameter increase was 2.8 ± 0.4 hours. The immediate coupling and decoupling between follicles and FSH may be essential aspects of follicle deviation during selection of DF1 by impeding the growth rate of the future SF1 before it can attain the developmental stage needed for continued growth during low FSH.

Short communication: Development of the first follicular wave dominant follicle on the ovary ipsilateral to the corpus luteum is associated with decreased conception rate in dairy cattle

In this study, we examined the effect of the locations of the first-wave dominant follicle (DF) and corpus luteum (CL) on fertility. In total, 350 artificial insemination (AI) procedures were conducted (lactating dairy cows: n=238, dairy heifers: n=112). Ovulation was confirmed 24 h after AI. The locations of the first-wave DF and CL were examined 5 to 9d after AI using rectal palpation or transrectal ultrasonography. Lactating dairy cows and dairy heifers were divided into 2 groups: (1) the ipsilateral group (IG), in which the DF was ipsilateral to the CL; and (2) the contralateral group (CG), in which the DF was contralateral to the CL. Pregnancy was diagnosed using transrectal ultrasonography 40d after AI. Conception rates were 54.0% in all cattle: 48.9% in lactating dairy cows, and 58.9% in dairy heifers. The incidence of the first-wave DF location did not differ between IG and CG (all cattle: 184 vs. 166; lactating cows: 129 vs. 109; heifers: 55 vs. 57 for IG vs. CG). Conception rates were lower in IG than in CG (all cattle: 40.2 vs. 69.3%; lactating dairy cows: 38.0 vs. 67.0%; dairy heifers: 45.5 vs. 73.7%, for IG vs. CG). Conception rate was not affected by season or live weight in heifers and lactating cows. In addition, days in milk at AI, milk production, body condition score, and parity did not affect conception in lactating cows. In summary, development of the first-wave DF in the ovary ipsilateral to the CL was associated with reduced conception rates in both lactating cows and heifers.

116 THE CHARACTERISTICS OF CORPUS LUTEUM SIZE, BLOOD FLOW, AND PLASMA PROGESTERONE CONCENTRATION AFTER OVULATION OF THE FIRST AND SECOND WAVE DOMINANT FOLLICLE

The characteristics of the corpus luteum (CL) are greatly affected by the characteristics of the preceeding preovulatory follicle, such as follicle size and function. A previous study reported that the concentration of oestradiol in follicular fluid and production of androstenedione and progesterone (P4) by cultured theca cells are higher in the first follicular wave dominant follicle than in the second follicular wave dominant follicle. In addition, blood flow in the wall of the preovulatory follicle is higher in the first follicular wave than in the second follicular wave. These results suggest that the characteristics of the dominant follicle in the first and the second follicular wave may be different. The objective of this study was to compare CL characteristics, such as diameter, cross-sectional area, blood flow area, and plasma P4 concentration after ovulation of the dominant follicle between the first and the second follicular waves. Preovulatory follicles and CL formed after ovulation of the first follicular wave (W1; n = 5) and second follicular wave (W2; n = 6) were examined in non-lactating Holstein cows. In W1, PGF2α and GnRH were administrated on D7 and D9 of the oestrus cycle (D0 = oestrus), respectively, to induce follicular maturation. In W2, GnRH was administrated on D6 to induce a new follicular wave; subsequently, PGF2α and GnRH were administrated on D14 and D16, respectively. Diameter and percentage of follicular circumference with blood flow of preovulatory follicle on D10 in W1 and D17 in W2 were measured by transrectal colour Doppler ultrasonography. Diameter, cross-sectional area, and blood flow area of CL formed after ovulation in W1 (W1CL) and W2 (W2CL) were also examined on Day 3, 6, and 9 after ovulation (Day 1 = ovulation day). Blood samples were collected from Day 1 to 9 for P4 measurement. Quantitative end-points for diameter and percentage of follicular circumference with blood flow of the preovulatory follicle were analysed between the groups by using the unpaired Student's t-test. Diameter, cross-sectional area, blood flow area of CL, and plasma P4 concentration were analysed by repeated-measures ANOVA followed by Scheffe's F-test as a multiple comparison test. Larger diameter and higher percentage of follicular circumference with blood flow of the preovulatory follicle were observed in W1 compared with those in W2 (P &lt; 0.01). Diameter of CL was larger in W1CL than in W2CL regardless of day (P &lt; 0.001). Cross-sectional area of CL was larger in W1CL than in W2CL on Day 6 and 9 but not on Day 3. Blood flow area of CL was larger in W1CL than in W2CL on Day 3 and 6 but not in Day 9. Plasma P4 concentrations were higher in W1CL than in W2CL on Day5 and 7 (P &lt; 0.05). In conclusion, larger size and higher percentage of follicular circumference with blood flow of preovulatory follicle in W1 lead to a larger size and a blood flow area of CL as well as higher plasma P4 concentration. These results suggest that preovulatory blood flow status affects the morphology and function of CL.

110 EFFECT OF HUMAN CHORIONIC GONADOTROPIN (hCG) ADMINISTRATION ON DAYS 1, 2, 3, OR 4 POST-OESTRUS ON CORPUS LUTEUM DEVELOPMENT AND CIRCULATING PROGESTERONE CONCENTRATIONS IN BEEF HEIFERS

The steroid hormone progesterone (P4) plays a key role in the reproductive events associated with the establishment and maintenance of pregnancy. Elevated concentrations of circulating P4 in the immediate post-conception period have been associated with advanced conceptus elongation, increased interferon-tau production, and greater pregnancy rates in cattle. Several strategies have been employed to supplement the endogenous P4 supplied by the corpus luteum (CL). One such strategy is the administration of human chorionic gonadotropin (hCG) during the early luteal phase (typically Day 5) that induces ovulation of the first wave dominant follicle and formation of a functional accessory CL, in turn leading to increased circulating concentrations of P4. In addition to this effect, hCG also stimulates hypertrophy of the original CL, leading to a significant deviation in P4 concentrations 2 days after administration. The aim of this study was to examine whether administration of hCG earlier during the metoestrus period would lead to an earlier rise in P4 by stimulation of the developing endogenous CL. The oestrous cycles of cross-bred beef heifers (n = 50) were synchronised and those recorded in standing oestrus (Day 0) were assigned randomly to one of 5 treatments and administered a single IM injection of saline on Day 1 after oestrus (Control) or 3000 IU hCG on Day 1, 2, 3, or 4 after oestrus. Daily blood samples were collected from Day 0 to 14 by coccygeal venipuncture to measure serum P4 concentration. The dimensions of the original CL and induced CL, when present, were measured by daily ultrasound scanning beginning on Day 3 after oestrus until Day 14. Data were analysed using the PROC MIXED procedure of SAS (SAS Institute Inc., Cary, NC, USA). In terms of effects on the CL, administration of hCG on Day 1 had no effect on CL area. Administration on Day 2 increased CL area from Day 6 to 12 (P ≤ 0.05). hCG on Day 3 increased CL area from Day 9 to 11, while administration on Day 4 increased CL size on Day 9 and 10 (P ≤ 0.05). Administration of hCG on Day 4 induced the formation of an accessory CL in 89% of heifers, resulting in a significant increase in total luteal tissue area on the ovaries compared to all other groups. Consistent with the effects on the CL, hCG on Day 1 did not affect P4 concentrations. Administration on Day 2 significantly increased P4 compared to the control from Day 6 to 11 (P ≤ 0.05). Administration on Day 3 resulted in a nonsignificant increase in P4, while hCG on Day 4 increased P4 from Day 8 to 13 compared to the control (P ≤ 0.05). In conclusion, administration of hCG as early as Day 2 post oestrus results in increased P4 in circulation from Day 6 which should have beneficial downstream effects in terms of uterine receptivity and conceptus elongation. Funded by Science Foundation Ireland (07/SRC/B1156) and the Spanish Ministry of Science and Innovation AGL2009-11810.

Comparison between lactating and non-lactating dairy cows on follicular growth and corpus luteum development, and endocrine patterns of ovarian steroids and luteinizing hormone in the estrous cycles

The dynamics of ovarian follicle, corpus luteum (CL), and peripheral plasma ovarian steroids were compared between lactating and non-lactating cows, and a possible association of pulsatile luteinizing hormone (LH) secretion with the dynamics was examined. Lactating (n=5) and non-lactating (n=5) cows were monitored daily for follicle and CL throughout two consecutive estrous cycles (Day 0: day of ovulation). Blood samples were collected daily and at 15min intervals for 8h on Days 2, 4, 6, 8, and 14 of the second cycle. Lactating cows had larger CL (25.4±1.8mm vs. 23.5±1.5mm, P<0.01) and greater progesterone concentrations (4.6±1.0ng/ml vs. 3.9±0.9ng/ml, P<0.01) during mid-luteal phase compared with non-lactating cows. Maximal diameters of the first wave dominant follicle (17.2±1.8mm vs. 15.5±0.8mm) and the ovulatory follicle (17.9±1.2mm vs. 15.2±0.8mm) were greater (P<0.05) in lactating cows than in non-lactating cows during the estrous cycles with two follicular waves, but no significant differences were detected between the groups during the estrous cycles with three follicular waves. Plasma estradiol concentrations did not differ between the groups throughout the experiment. Lactating cows had more LH pulses from Days 2 to 14 than non-lactating cows. These results imply that differences in ovarian dynamics may exist between lactating and non-lactating cows, for which the increased number of LH pulses observed in lactating cows may have responsibility.

Effect of eCG on early resumption of ovarian activity in postpartum dairy cows

The purpose of the present study was to hasten the resumption of ovarian activity early postpartum in lactating dairy cows, using equine chorionic gonadotropin (eCG), to enhance follicular growth, followed by hCG, to induce ovulation. Primiparous Holstein dairy cows ( n = 21) were assigned equally into eCG, eCG–hCG and Control groups. Cows in the eCG and eCG–hCG groups received an i.m. injection of eCG (500 IU Folligon ®) on Day 6 postpartum. Cows in the eCG–hCG group were also given an i.m. injection of hCG (500 IU Chorulon ®), once dominant follicle reached the diameter of 13–16 mm following eCG injection. Cows in Control group did not receive any treatment. Daily blood sampling and ultrasound examination were conducted, starting at Day 6 postpartum until confirming the third ovulation. Follicles ≥10 mm in diameter were detected on Day 11.5 ± 1.48, 10.1 ± 0.52 and 11.1 ± 1.36 after calving in Control, eCG and eCG–hCG groups, respectively ( P > 0.05). The first wave dominant follicle ovulated in 71.4% of cows treated with eCG and eCG–hCG. In contrast, none of the first wave dominant follicles ovulated in Control cows. By Day 20 postpartum, all cows in eCG group, 6/7 cows in eCG–hCG group and none of the cows in Control group ovulated ( P < 0.05). Short estrous cycles (≤16 days) were detected in 2/7, 1/7 and 6/7 cows in eCG, eCG–hCG and control groups, respectively ( P < 0.05). In conclusion, injection of eCG on Day 6 postpartum could assist the early resumption of ovarian activity by enhancing ovarian follicle growth and early ovulation in postpartum cows. In this context, subsequent hCG injection may not provide any more beneficial effect.

Efeito do tempo da aplicação de prostaglandina na resposta folicular em ovelhas durante o ciclo estral

Avaliou-se a resposta ovariana, usando ultrassonografia transretal, à aplicação de duas injeções de prostaglandina (PGF2α) em diferentes intervalos. Foram utilizadas 14 fêmeas ovinas da raça Bergamácia durante a estação reprodutiva, sendo que todas receberam uma dose intramuscular de um análogo de PGF2α. As ovelhas foram distribuídas em dois grupos (n = 7). Em um dos grupos, a PGF2α foi administrada sete dias (PG7) e, no outro, nove dias (PG9) depois da ovulação, quando o folículo dominante da onda 2 encontrava-se nas fases de crescimento e platô, respectivamente. Examinaram-se os ovários diariamente, utilizando-se um ultrassom Aloka 500, provido de um transdutor linear transretal de 7,5 MHz. A ultrassonografia foi iniciada um dia antes da segunda aplicação de prostaglandina até o dia 10 depois da ovulação em ambos os grupos. Amostras de sangue foram colhidas, via punção jugular, a cada dia, para quantificação de progesterona. As concentrações plasmáticas de progesterona mostraram-se menores no PG7 quando comparado com o PG9, imediatamente antes do tratamento com a PGF2α (4,10 ± 0,17 vs 4,91 ± 0,29 ng/mL; respectivamente). A média do diâmetro máximo atingido pelo folículo dominante da onda 2 foi maior no grupo tratado PG7 comparado com o PG9 (5,5 ± 0,19 vs 4,29 ± 0,26 mm). Houve efeito do dia nos folículos totais. A quantidade de folículos pequenos (2-2,5 mm) foi maior (4,57 ± 0,78 versus 8,42 ± 1,36) no dia 6, nos grupos PG7 e PG9, respectivamente, mas não foram observadas mudanças nos folículos médios (3-3,5 mm) entre os grupos tratados. A proporção de folículos grandes (4 mm) aumentou depois da luteólise; os valores foram menores nas ovelhas tratadas no PG7 e mantiveram-se estáveis no tempo no PG9. Em ovelhas com rápida e completa luteólise, a ovulação ocorre no folículo dominante da onda 2 em fêmeas tratadas sete ou nove dias após a ovulação.

Administration of human chorionic gonadotropin at embryo transfer induced ovulation of a first wave dominant follicle, and increased progesterone and transfer pregnancy rates

We hypothesized that administration of hCG to recipients at embryo transfer (ET) would induce accessory CL, increase serum progesterone concentrations, and reduce early embryonic loss (as measured by increased transfer pregnancy rates). At three locations, purebred and crossbred Angus, Simmental, and Hereford recipients (n = 719) were assigned alternately to receive i.m. 1,000 IU hCG or 1 mL saline (control) at ET. Fresh or frozen-thawed embryos were transferred to recipients with a palpable CL on Days 5.5 to 8.5 (median = Day 7) of the cycle (Locations 1 and 2), or on Day 7 after timed ovulation (Location 3). Pregnancy diagnoses (transrectal ultrasonography) were done 28 to 39 d (median = 35 d) and reconfirmed 58 to 77 d (median = 67 d) post-estrus. At Location 1 (n = 108), ovaries were examined at pregnancy diagnosis to enumerate CL. More (P < 0.001) pregnant hCG-treated cows (69.0%) had multiple CL than pregnant controls (0%). Serum progesterone (ng/mL) determined at Locations 1 and 2 (n = 471) at both pregnancy diagnoses in pregnant cows was greater (P ≤ 0.05) after hCG treatment than in controls (first: 8.1 ± 0.9 vs 6.1 ± 0.8; second: 8.8 ± 0.9 vs 6.6 ± 0.7), respectively. Unadjusted pregnancy rates at the first diagnosis were 61.8 and 53.9% for hCG and controls. At the second diagnosis, pregnancy rates were 58.6 and 51.3%, respectively. Treatment (P = 0.026), embryo type (P = 0.016), and BCS (P = 0.074) affected transfer pregnancy rates. Based on odds ratios, greater pregnancy rates occurred in recipients receiving hCG, a fresh embryo (66.3 vs 55.5%), and having BCS >5 (62.3 vs 55.3%). We concluded that giving hCG at ET increased incidence of accessory CL, serum progesterone in pregnant recipients, and transfer pregnancy rates. Furthermore, we inferred that increased progesterone resulting from hCG-induced ovulation reduced early embryonic losses after transfer of embryos to recipients.

211 EFFECT OF ESTRADIOL BENZOATE ON THE FIRST WAVE DOMINANT FOLLICLE IN HOLSTEIN HEIFERS

The objective of this study was to evaluate the effect of different doses of estradiol benzoate on the first wave dominant follicle in Holstein heifers. Estrous cycle of cyclic Holstein heifers (n = 16; 13.84 ± 0.44 months of age; 335.5 ± 6.65 kg) was synchronized using CIDR (14 days; VetoCIDR®, Aburaihan, Tehran, Iran) in association with GnRH analogue (12.5 μgi.m. Vetaroline®, Aburaihan) on Day 6 and PGF2 analogue (500 μg; Vetaprost®, Aburaihan) on day 13 after CIDR insertion. On Days 5 to 7 of the ensuing cycle (Day 0 of the experiment), heifers were assigned into 4 experimental groups. Heifers in Groups 1, 2, and 3 (n = 4 in each group) received 2, 5, and 10 mg of estradiol benzoate (i.m. Vetastrol®, Aburaihan), respectively, concurrent with 100 mg of progesterone (i.m. Vetagesterone®, Aburaihan). Heifers in the control group (n = 4) received distilled water as a placebo intramuscularly. Ovarian follicles were monitored daily, from Days 0 to 16, using an ultrasound scanner (Sonovet 2000, Korea) equipped with a 7.5-MHz transrectal probe. Initiation of follicle regression was defined when there was a sudden decrease of 1 to 2 mm followed by a progressive decrease in the diameter of the ovarian follicle. Emergence of anew follicle wave was defined as the day that the dominant follicle was, retrospectively, identified at a diameter of 4 to 5 mm. Data were analyzed using Kruskal-Wallis one-way ANOVA in SAS (SAS Institute, Cary, NC). On Day 0, there was a functional CL (19.62 ± 0.57 mm) and a growing dominant follicle (11.25 ± 0.62 mm) on the ovary of all heifers. The dominant follicle regressed on Day 3.5 ± 1.04, 3.2 ± 0.85, 2.7 ± 0.75, and 8.5 ± 0.50 in Groups 1, 2, 3, and control, respectively (P &lt; 0.05). A new follicle wave emerged on Day 7.7 ± 0.25, 8.2 ± 0.48, 9.7 ± 1.44, and 7.2 ± 1.11 in Groups 1, 2, 3, and control, respectively (P &gt; 0.05). Estrus was detected on Day 12.0 ± 1, 11.7 ± 0.34, 13.0 ± 0.00, and 15.2 ± 1.75 in Groups 1, 2, 3, and control, respectively (P &gt; 0.05). The interval between steroid injections (Day 0) and ovulation were 13 ± 0.41, 13 ± 0, 14.3 ± 0.33, and 16.2 ± 1.75 days for Groups 1, 2, 3, and control, respectively (P &gt; 0.05). Interovulatory intervals were 18.7 ± 0.33, 18.7 ± 0.33, 20.7 ± 0.67, and 20.5 ± 1.55 days for Groups 1, 2, 3, and control, respectively (P &gt; 0.05). In conclusion, estradiol benzoate induced early regression of the dominant follicle of the first wave but did not affect the interval between steroid treatment and ovulation in Holstein heifers. This research was funded by Aburaihan Pharmaceutical Company (Tehran, Iran).