Follicle deviation and ovulatory capacity in Bos indicus heifers

The objectives of Experiment 1 were to determine the interval from ovulation to deviation, and diameter of the dominant follicle (DF) and largest subordinate follicle (SF) at deviation in Nelore (Bos indicus) heifers by two methods (observed and calculated). Heifers (n = 12) were examined ultrasonographically every 12 h from ovulation (Day 0) to Day 5. The time of deviation and diameter of the DF and largest SF at deviation did not differ (P>0.05) between observed and calculated methods. Overall, deviation occurred 2.5+/-0.2 d (mean +/- S.E.M.) after ovulation, and diameters for DF and largest SF at deviation were 6.2+/-0.2 and 5.9 +/- 0.2 mm, respectively. Experiment 2 was designed to determine the size at which the DF acquires ovulatory capacity in B. indicus heifers. Twenty-nine heifers were monitored every 24 h by ultrasonography, from ovulation until the DF reached diameters of 7.0-8.4 mm (n=9), 8.5-10.0 mm (n=10), or >10.0 mm (n=10). At that time, heifers were treated with 25 mg of pLH and monitored by ultrasonography every 12 h for 48 h. Ovulation occurred in 3 of 9, 8 of 10, and 9 of 10 heifers, respectively (P<0.05). In summary, there was no significant difference between observed and calculated methods of determining the beginning of follicle deviation. Deviation occurred 2.5 d after ovulation when the DF reached 6.2 mm, and ovulatory capacity was acquired by DF as small as 7.0 mm.     

Ovarian function in Nelore (Bos taurus indicus) cows after post-ovulation hormonal treatments

Maternal recognition of pregnancy in the cow requires successful signaling by the conceptus to block luteolysis. Conceptus growth and function depend on an optimal uterine environment, regulated by luteal progesterone. The objective of this study was to test strategies to optimize luteal function, as well as prevent a dominant follicle from initiating luteolysis. Nelore (Bos taurus indicus) beef cows (n=40) were submitted to a GnRH/PGF(2alpha)/GnRH protocol. Cows that ovulated from a dominant ovarian follicle (ovulation=Day 0) were allocated to receive: no additional treatment (G(C); n=7); 3000IU of hCG on Day 5 (G(hCG); n=5); 5mg of estradiol-17beta on Day 12 (G(E2); n=6); or 3000IU of hCG on Day 5 and 5mg of estradiol-17beta on Day 12 (G(hCG/E2); n=5). Ultrasonographic imaging of the ovaries, assessment of plasma progesterone concentration, and detection of estrus were done daily from Day 5 to the day of subsequent ovulation. Treatment with hCG induced an accessory CL, increased CL volume, and plasma progesterone concentration throughout the luteal phase (P<0.01). Estradiol-17beta induced atresia and recruitment of a new wave of follicular growth; it eliminated a potentially estrogen-active, growing ovarian follicle within the critical period for maternal recognition of pregnancy, but it also hastened luteolysis (Days 16 or 17 vs. Days 18 or 19 in non-treated cows). In conclusion, the approaches tested enhanced luteal function (hCG) and altered ovarian follicular dynamics (estradiol-17beta), but were unable to extend the life-span of the CL in Nelore cows.     

Follicular dynamics and plasma FSH and progesterone concentrations during follicular deviation in the first post-ovulatory wave in Nelore (Bos indicus) heifers

The objective of the present study was to characterize ovarian follicular dynamics and hormone concentrations during follicular deviation in the first wave after ovulation in Nelore (Bos indicus) heifers. Ultrasonographic exams were performed and blood samples were collected every 12h from the day of estrus until 120-144 h after ovulation in seven females. Deviation was defined as the point at which the growth rate of the dominant follicle became greater than the growth rate of the largest subordinate follicle. Deviation occurred approximately 65 h after ovulation. Growth rate of the dominant follicle increased (P<0.05) after deviation, while growth rate of the subordinate follicle decreased (P<0.05). Diameter of the dominant follicle did not differ from the subordinate follicle at deviation (approximately 5.4mm). The dominant follicle (7.6mm) was larger (P<0.05) than the subordinate follicle (5.3mm) 96 h after ovulation or 24h after deviation. Plasma FSH concentrations did not change significantly during the post-ovulatory period. The first significant increase in mean plasma progesterone concentration occurred on the day of follicular deviation. In conclusion, the interval from ovulation to follicular deviation (2.7 days) was similar to that previously reported in B. taurus females, but follicles were smaller. Diameters of the dominant follicle and subordinate follicle did not differ before deviation and deviation was characterized by an increase in dominant follicle and decrease in subordinate follicle growth rate. Variations in FSH concentrations within 12-h intervals were not involved in follicular deviation in Nelore heifers.     

Ovarian follicular dynamics in Nelore breed (Bos indicus) cattle

The most common beef cattle raised in Brazil is the Nelore breed (Bos indicus). Information obtained by ultrasonography on follicular growth in Bos taurus cattle has been accumulating rapidly. However, there are few publications to date on follicular development in Bos indicus breeds. The follicular dynamics in Nelore heifers and cows during natural or prostaglandin (PG)-induced estrous cycle were studied. From the detection of estrus onward, all animals were examined daily by ultrasonography for one (n = 35) or two (n = 10) consecutive estrous cycles. The follicular dynamic in Nelore cattle was characterized by the predominance of 2 follicular waves in the cows (83.3%, n = 18, P < 0.05) and 3 waves in the heifers (64.7%, n = 16, P < 0.05). Most of the cattle observed over 2 consecutive estrous cycles presented the same pattern of follicular waves in the first and second cycle, and only 30% showed variation in the number of waves from one cycle to the other. Most of the follicular parameters analyzed were not affected by PG treatment or age but were altered by follicular waves. Consequently, data on cows and heifers were combined according to the number of follicular waves. The ovulatory follicle was larger than the other dominant follicles (P < 0.05), and the ovulatory wave was shorter than the preceding waves (P < 0.05). The interovulatory interval was longer in animals showing 3 waves than those exhibiting 2 waves (P < 0.05). Maximum diameter of the dominant follicle (around 11 mm) and of the corpus luteum (CL, approximately 17 mm) were smaller than those reported for European breeds. In conclusion, the results demonstrate that although the dominant follicle and corpus luteum are smaller than in European breeds, the follicular dynamics in Nelore cattle were similar to those observed in European breeds and were characterized by 2 or 3 follicular waves for cows and heifers, respectively, during the natural or prostaglandin-induced estrous cycle.     

Proteome analysis of Nelore bull (Bos taurus indicus) seminal plasma

The Nelore bull (Bos taurus indicus) seminal plasma proteome was analyzed by MALDI-TOF MS and two-dimensional gel electrophoresis. A total of 260 spots were visualized in the 2-DE gel (pI range 3-10) and 13 spots could be identified by peptide mass fingerprinting corresponding to 11 different polypeptides. The results allowed the creation of the first proteomic map of Bos taurus indicus seminal plasma. The roles of the identified proteins in the bull seminal plasma are discussed.     

LH surge in Nelore cows (Bos indicus), after induced estrus or after ovarian superestimulation

Considering that there is limited information about the preovulatory LH surge in Zebu cattle (Bos indicus), the purpose of the present work was to assess the LH surge in Nelore cows during the estrous cycle and after ovarian superestimulation of ovarian follicular development with FSH. This information is particularly important to improve superovulatory protocols associated with fixed-time artificial insemination. Nelore cows (n=12) had their estrus synchronized with an intravaginal device containing progesterone (CIDR-B) associated with estradiol benzoate administration (EB, 2.5 mg, i.m., Day 0). Eight days later all animals were treated with PGF2alpha (Day 8) in the morning (8:00 h) and at night, when CIDR devices were removed (20:00 h). Starting 38h after the first PGF2alpha injection, blood sampling and ovarian ultrasonography took place every 4h, during 37 consecutive hours. Frequent handling may have resulted in a stress-induced suppression of LH secretion resulting in only 3 of 12 cows having ovulations at 46.7+/-4.9 and 72.3+/-3.8 h, respectively, after removal of CIDR-B. Thirty days later, the same animals received the described hormonal treatment associated with FSH (Folltropin), total dose=200 mg) administered twice a day, during 4 consecutive days, starting on Day 5. Thirty-six hours after the first injection of PGF2alpha, to minimize stress, only seven blood samples were collected at 4h interval each, and ultrasonography was performed every 12 h until ovulation. In 11 of 12 cows (92%) the LH surge and ovulation were observed 34.6+/-1.6 and 59.5+/-1.9 h, respectively, after removal of progesterone source. The maximum values for LH in those animals were 19.0+/-2.6 ng/ml (mean+/-S.E.M.). It is concluded that, in Nelore cows submitted to a ovarian superstimulation protocol, the LH surge occurs approximately 35 h after removal of intravaginal device containing progesterone, and approximately 12h before the LH surge observed after an induced estrus without ovarian superstimulation.     

Fertility on synchronized estrus in crossbred (Bos taurus x Bos indicus) heifers

This study was performed in Western Maharastra (India). The 272 crossbred heifers were randomly allocated within herds to one of the four following groups: 1) silastic coils, 10 days treatment (n = 65); 2) Norgestomet implants, 10 days treatment (n = 71); 3) prostaglandin F(2alpha) two injections 11 days apart (n = 70); and 4) control (n = 66). Almost all heifers in the treated groups were detected in heat during the four days following treatment (88-100%) vs 26% in the control group in the first 21 days. Mean conception rates at first AIs were respectively 62,48 and 60% in groups 1,2 and 4 (p > 0.05) and only 29% in group 3. By 90 days after treatment, 66, 59, 46 and 33 per cent of the females were pregnant for groups 1 to 4, respectively (p < 0.001). In conclusion, progestogen treatments seemed to be highly satisfactory both in terms of conception rates and intervals from treatment to pregnancy.     

Superovulation, collection and transfer of embryos and demi-embryos from Boran(Bos indicus ) cows and heifers

Twenty-three Boran(Bos indicus ) cows and heifers were superovulated with pregnant mare serum gonadotropin (PMSG); a total of four embryos and 4.1 +/- 0.3 (mean +/- SEM) ova per ova-producing donor resulted. Follicle stimulating hormone (FSH-P) was then used to superovulate 49 Boran cows for a total of 106 superovulations, of which 63 (59.4%) produced an average of 3.7 +/- 0.4 (mean +/- SEM) embryos. The embryo production was not influenced by either the season or the number of times(one to five) the cows were superovulated. A higher pregnancy rate was obtained when the selection of Boran recipients was based on their plasma-progesterone values (overall 52.5%, single embryos 63.3%, twin demi-embryos 45.8%) than when they were selected by palpation per rectum only (overall 43.8%, single embryos 50%, twin demi-embryos 36.4%). The twinning rate of twin demiembryos was 62.5%, whereas only single calves were born after transfer of two embryos per recipient. No pregnancies were produced following transfer of twin demi-embryos without zonae pellucidae. Transferring single demi-embryos gave a low pregnancy rate (13.3%). Twelve donor Boran cows (21 superovulations) bred with their fathers resulted in a high rate of early embryonic death; additionally, only 20.9% (overall) of the recipients became pregnant. Estrus synchronization of Boran cows with a progesterone releasing intravaginal device (PRID) for a short period (7 d) combined with one injection of prostaglandin (Day 6) produced a larger number of good quality recipients (70.5%) than using double prostaglandin injections (60%).     

Plasma progesterone concentration in Bos taurus and Bos indicus heifers

Progesterone concentrations were determined by radioimmunoassay in the plasma of heifers of German Brown Swiss, Holstein-Friesian and White Fulani cattle during two consecutive estrous cycles in the dry and wet seasons in a tropical climate. Seasonal differences in the levels were not significant but peak levels were significantly higher in the $\text{Bos}$$\text{taurus}$ than in the $\text{Bos}$$\text{indicus}$ heifers. The low levels at estrus and the gradual rise five days after estrus were similar among the heifers. The levels on the 1st and 2nd days preceding estrus were significantly higher in the $\text{Bos}$$\text{taurus}$ than in the $\text{Bos}$$\text{indicus}$ heifers, and suggest a possible tendency for the former to be more susceptible to infertility arising from high progesterone levels 1 and 2 days preceding estrus and insemination. The genital tract and ovaries at the mature luteal phase were generally smaller in the $\text{Bos}$$\text{indicus}$ than in the $\text{Bos}$$\text{taurus}$ heifers.     

Effects of biostimulation and nutritional supplementation on pubertal age and pregnancy rates of Nelore heifers (Bos indicus) in a tropical environment

To determine effects of biostimulation (BIO) and dietary supplementation (BIO+S) on pubertal age and pregnancy rates, Nelore heifers (n=392) were randomly assigned to one of four treatment groups (n=98/group). All animals were in tropical environmental conditions, in the middle-west region of Brazil, grazing in pastures of Brachiaria brizantha, cv. Marandu; Panicum Maximum, cv. Tanzania and Brachiaria humidícula. The heifers of the BIO group were kept in the presence of bulls while being maintained on pasture; the animals in the BIO+S group were kept in the presence of bulls while being managed on pasture and were fed a diet with greater energy and protein content to produce 0.49 kg of BW gain/day; the animals in control group (the NBIO) were kept away from bulls and under pasture conditions; and the animals in the NBIO+S group were kept away from bulls, were maintained on pasture, and were fed the same diet as the BIO+S group. Heifers were bred at 22-23 months of age, and pregnancy diagnosis was made 45 days after the end of the breeding season. There were differences (P<0.05) between groups regarding pubertal heifers up to 19 months (NPH), final body weight (FBW) and pregnancy rates (P<0.01), with an advantage for the animals in the BIO and BIO+S groups. Although the effect of a diet with greater protein and energy content was not clear in this experiment, the exposure of heifers to a male during the prepubertal period decreased age at the first breeding season, resulting in a significant reduction in age of first pregnancy in Nelore heifers kept under extensive management systems in a tropical environment.     

Plasma concentrations of progesterone, 17beta-estradiol and androstenedione and superovulatory response of Nelore cows (Bos indicus) treated with FSH

Progesterone (P(4)), 17beta- estradiol (E(2)) and androstenedione (A(4)) plasma concentrations were correlated with palpated corpora lutea (CL), recovered embryos and viable embryos in 13 Nelore cows induced to superovulate with FSH, starting on Day 10 of the estrous cycle. Administration of FSH increased the number of ovulations and recovered embryos. Plasma P(4), E(2) and A(4) levels on Day 0 and of P(4) on Days 10 and 11 of the cycle were not correlated with the superovulatory response. Determination of CL by palpation per rectum was used to estimate the number of recovered embryos. Plasma P(4) levels higher than 1 ng/ml on the induced estrus day (Day 14) had an adverse effect on the embryo viability rate. Plasma E(2) concentrations on Day 14 were positively correlated with the number of viable embryos collected, a correlation that has not been previously reported. The present data indicate that plasma P(4) and E(2) concentrations in FSH-PGF2alpha-treated Nelore cows are useful for the identification of 2 different populations of Nelore donors and are correlated with superovulatory response and, particularly, with the number of viable embryos.     

Comparison of embryo yield and pregnancy rate between in vivo and in vitro methods in the same Nelore (Bos indicus) donor cows

To investigate why the preferred means to produce bovine embryos in Brazil has changed from in vivo to in vitro, we compared these two approaches in the same Nelore cows (n = 30) and assessed total embryo production and pregnancy rates. Without a specific schedule, all cows were subjected to ultrasound-guided ovum pick up (OPU)/in vitro production (IVP) and MOET, with intervals ranging from 15 to 45 d between procedures, respectively. To produce in vivo embryos, cows were superovulated and embryos were recovered nonsurgically from 1 to 3 times (1.4 ± 0.6), whereas OPU/IVP was repeated from 1 to 5 times (3.2 ± 1.2) in each donor cow during a 12-mo interval. Embryos obtained from both methods were transferred to crossbred heifers. On average, 25.6 ± 15.3 immature oocytes were collected per OPU attempt. The average number of embryos produced by OPU/IVP (9.4 ± 5.3) was higher (P < 0.05) than the MOET method (6.7 ± 3.7). However, pregnancy rates were lower (P < 0.05) following transfer of IVP (33.5%) versus in vivo-derived embryos (41.5%) embryos. Embryonic losses between Days 30 and 60 and fetal sex ratio were similar (P > 0.05) between in vivo and in vitro-derived embryos. We concluded that in Nelore cows, with an interval of 15 d between OPU procedures, it was possible to produce more embryos and pregnancies compared to conventional MOET.     

Effect of early luteolysis in progesterone-based timed AI protocols in Bos indicus, Bos indicus x Bos taurus, and Bos taurus heifers

The objective of this study was to evaluate the effects of treatment with an intravaginal progesterone-releasing device (CIDR) and estradiol benzoate (EB) on follicular dynamics in Bos indicus (n=23), Bos taurus (n=25), and cross-bred (n=23) heifers. To assess the influence of reduced serum progesterone concentrations during 8 days of treatment with a progesterone-releasing device on follicular dynamics, half of the heifers received PGF at CIDR insertion (Day 0; 3 x 2 factorial design). Mean (+/-S.E.M.) serum progesterone concentrations during CIDR treatment varied (P<0.05) among genetic groups: B. indicus (5.4+/-0.1 ng/mL), B. taurus (3.3+/-0.0 ng/mL), and cross-bred (4.3+/-0.1 ng/mL). Maximum diameter of the dominant follicle (DF) was smaller (P<0.01) in B. indicus heifers (9.5+/-0.5 mm) than in cross-bred (12.3+/-0.4 mm) or B. taurus heifers (11.6+/-0.5 mm). B. indicus experienced lower (P<0.01) ovulation rate (39.1%) than did B. taurus (72.7%) and cross-bred (84.0%). Heifers treated with PGF on Day 0 had lower (P<0.05) serum progesterone concentrations during progesterone treatment. The PGF treatment on Day 0 increased (P<0.01) the diameter of the DF (11.9+/-0.4 mm vs. 10.5+/-0.4 mm). Moreover, greater (P=0.02) ovulation rates (78.8 vs. 54.0%) occurred in heifers treated with PGF on Day 0. In summary, B. indicus heifers had greater serum progesterone concentrations, smaller DF diameter, and a lower ovulation rate compared to B. taurus heifers. Prostaglandin treatment on the day of CIDR insertion reduced serum progesterone during treatment, and resulted in increased maximum DF diameter and ovulation rate.     

Effects of dominant follicle aspiration and treatment with recombinant bovine somatotropin (BST) on ovarian follicular development in nelore (Bos indicus) heifers

Follicle ablation has been recognized as an efficient method of follicular wave synchronization. Treatment with recombinant bovine somatotropin (BST) has been shown to enhance follicular development in Bos taurus. This experiment assessed the effects of these treatments in Nelore (B. indicus) heifers. Eight cycling Nelore heifers were randomly assigned to 3 different treatments. On Day 2 of a synchronized cycle (Day 0 = day of ovulation), heifers assigned to Treatments 1 and 2 received 2 mL of saline, whereas heifers assigned to Treatment 3 received 320 mg of BST. On Day 5, the first-wave dominant follicle was ablated by ultrasound-guided transvaginal aspiration in heifers in Treatments 2 and 3, and all heifers received an injection of prostaglandin on Day 11. Aspiration of the dominant follicle advanced and synchronized (P < 0.05) the day of second-wave emergence (6.9 +/- 0.1 vs. 8.4 +/- 0.4) and the day of the pre-wave FSH peak (6.0 +/- 0.0 vs. 6.9 +/- 0.4), and increased FSH peak concentrations (381 +/- 21 vs. 292 +/- 30; pg/mL; P < 0.01). Recombinant bovine somatotropin treatment caused a two-fold increase in plasma insulin-like growth factor-I (IGF-I) concentrations (P < 0.001) and resulted in a 36% increase in the number of small follicles (<5 mm; P < 0.001) compared with saline-treated heifers. In summary, in agreement with previous reports on B. taurus, dominant follicle aspiration synchronized ovarian follicular development, and BST treatment increased peripheral concentrations of IGF-I in Nelore heifers. Recombinant bovine somatotropin also increased the number of small follicles, but this response appeared to be inferior to that reported for B. taurus.     

Logistic regression analysis of pregnancy rate following transfer of Bos indicus embryos into Bos indicus x Bos taurus heifers

Factors affecting pregnancy rate of 5627 Zebu embryos in crossbred females with unknown proportions of Holstein and Zebu breeding were examined. After evaluation for developmental stage, quality, and viability, embryos were immediately transferred to recipients. Pregnancy diagnosis was conducted approximately 53 d after transfer; pregnancy rate was coded as a binomial event and analyzed using logistic regression models. Maximum likelihood methodology and the likelihood ratio statistic were used to estimate regression coefficients and test hypotheses. Explanatory variables were year of transfer (1992-1999), season of transfer (summer, autumn, winter and spring), breed of the embryo (Guzerat, Gyr or Nellore), stage of the embryo (morula, early blastocyst, blastocyst, expanded blastocyst, and hatching blastocyst), quality of the embryo (excellent, good or regular), and donor-recipient synchrony (estrus in the recipient occurred 2-3 d before, 1 d before, the day of, 1 d after, or 2-3 d after estrus in the donor). Average pregnancy rate was 63.7%. Pregnancy rates were not significantly affected by breed of embryo. The best multiple-logistic model to explain the pregnancy result included the effects of year and season of transfer, embryo stage and quality, and estrous synchrony between donor and recipient (P相似文献   

Peripheral plasma progesterone concentration in zebu (Bos indicus) cows during pregnancy

Plasma progesterone concentrations were determined weekly during gestation averaging 283 +/- 2 d in Ethiopian zebu (Bos indicus) cows. Mean progesterone levels increased from 0.2 +/- 0.1 ng/ml at oestrus (service) to 3.1 +/- 1.6 ng/ml on d 7 and 8.1 +/- 2.1 ng/ml on d 21. Progesterone levels remained elevated throughout pregnancy. Hormone concentration differed significantly between cows (P less than 0.001) and with the wk of pregnancy (P less than 0.05); it tended to be higher during the last trimester of pregnancy. Mean levels dropped sharply to below 1 ng/ml during the last wk of pregnancy with considerable variation (C.V. = 39 to 63%) among cows. These data indicate that pregnancy in Ethiopian zebu cows can be reliably diagnosed by determining circulatory plasma progesterone levels.     

Association between MUC1 gene polymorphism and expected progeny differences in Nelore cattle (Bos primigenius indicus)

MUC1 is a heavily glycosylated mammalian transmembrane protein expressed by mucosal secretory tissues for both protection against microbial infection and lubrication. An important characteristic of MUC1 is its variable number of tandem repeats (VNTR) containing several sites for O-glycosylation. VNTR length has been associated with many human diseases and with certain economically important traits in domestic ruminants. The aim of the present study was to correlate the length of MUC1 gene VNTR with expected progeny differences (EPDs) obtained for growth, fertility and carcass traits. Five alleles were identified, with alleles containing short VNTRs being more frequent than those with long, thereby demonstrating that Brazilian Nelore cattle are characterized by high frequencies in short MUC1 VNTRs. Statistical analyses revealed there to be no significant association between VNTR length and EPDs for weight at 120 days (W(120) ), scrotal circumference at 365 (SC (365) ) and 450 (SC (450) ) days, age at first calving (AFC), and rib eye area (REA).     

Effect of timing of estradiol benzoate administration upon synchronization of ovulation in suckling Nelore cows (Bos indicus) treated with a progesterone-releasing intravaginal device

The present study investigated how the timing of the administration of estradiol benzoate (EB) impacted the synchronization of ovulation in fixed-time artificial insemination protocols of cattle. To accomplish this, two experiments were conducted, with EB injection occurring at different times: at withdrawal of the progesterone-releasing (P4) intravaginal device or 24h later. The effectiveness of these times was compared by examining ovarian follicular dynamics (Experiment 1, n=30) and conception rates (Experiment 2, n=504). In Experiment 1, follicular dynamics was performed in 30 Nelore cows (Bos indicus) allocated into two groups. On a random day of the estrous cycle (Day 0), both groups received 2mg of EB i.m. and a P4-releasing intravaginal device, which was removed on Day 8, when 400 IU of eCG and 150 microg of PGF were administered. The control group (G-EB9; n=15) received 1mg of EB on Day 9, while Group EB8 (G-EB8; n=15) received the same dose a day earlier. Ovarian ultrasonographic evaluations were performed every 8h after device removal until ovulation. The timing of EB administration (Day 8 compared with Day 9) did affect the interval between P4 device removal to ovulation (59.4+/-2.0 h compared with 69.3+/-1.7h) and maximum diameter of dominant (1.54+/-0.06 acm compared with 1.71+/-0.05 bcm, P=0.03) and ovulatory (1.46+/-0.05 acm compared with 1.58+/-0.04 bcm, P<0.01) follicles. In Experiment 2, 504 suckling cows received the same treatment described in Experiment 1, but insemination was performed as follows: Group EB8-AI48 h (G-EB8-AI48 h; n=119) and Group EB8-AI54 h (G-EB8-AI54 h; n=134) received 1mg of EB on Day 8 and FTAI was performed, respectively, 48 or 54 h after P4 device removal. Group EB9-AI48h (G-EB9-AI48 h; n=126) and Group EB9-AI54 h (G-EB9-AI54 h; n=125) received the same treatments and underwent the same FTAI protocols as G-EB8-AI48 h and G-EB8-AI54 h, respectively; however, EB was administered on Day 9. Conception rates were greater (P<0.05) in G-EB9-AI54 h [63.2% (79/125) a], G-EB9-AI48 h [58.7% (74/126) a] and G-EB8-AI48 h [58.8% (70/119) a] than in G-EB8-AI54 h [34.3% (46/134) b]. We concluded that when EB administration occurred at device withdrawal (D8), the interval to ovulation shortened and dominant and ovulatory follicle diameters decreased. Furthermore, when EB treatment was performed 24h after device removal, FTAI conducted at either 48 or 54 h resulted in similar conception rates. However, EB treatment on the same day as device withdrawal resulted in a lesser conception rate when FTAI was conducted 54 h after device removal.     

Evaluation of three estrus synchronization regimens for use in extensively managed Bos indicus and Bos indicus/taurus heifers in Northern Australia

Two herds of extensively managed yearling Bos indicus and Bos indicus x Bos taurus heifers (n = 169) were assigned to one of three estrus synchronization treatment groups. The treatments consisted of 1) two injections of the prostaglandin (F(2)alpha) analogue, luprostiol (7.5 mg), given 12-d apart; 2) insertion of an intravaginal progesterone-releasing device (CIDR-B), followed by 400 IU i.m. pregnant mare serum gonadotrophin (PMSG) and 7.5 mg luprostinol at CIDR-B removal or 3) subcutaneous progestagen implant (SMB) for 10-d, followed by 400 IU i.m. and 7.5 mg i.m. luprostiol at implant removal. A dual tail paint-raddle system was used to evaluate response to treatment. Each treatment group was inseminated according to the manufacturer's recommendations for fixed-time artificial insemination (A.I.; luprostiol, 72h after the second injection, SMB and CIDR-B 48h after implant/device removal). The overall 51-d pregnancy rates for the three treatments were 18.6% (luprostiol), 48.8% (CIDR-B), and 53.3% (SMB). There were significant differences in the pregnancy rate between CIDR-B and luprostiol (P = 0.004) and between SMB and luprostiol (P =< 0.0001), but there was no difference in pregnancy rate between CIDR-B and SMB treatment.     

Exogenous progesterone enhances ova and embryo quality following superstimulation of the first follicular wave in Nelore (Bos indicus) donors

Three experiments were conducted to evaluate the effects of exogenous progesterone on superovulatory response and ova/embryo quality in Bos indicus donors superstimulated during the first follicular wave (FFW). We hypothesized that exogenous progesterone during gonadotropin treatments would improve ova and embryo quality. In Experiment 1, 18 Nelore cows were randomly allocated to three groups: (1) FFW; (2) FFW plus a progesterone-releasing device (FFW+P4); and (3) control (E2+P4). Cows in the FFW groups were superstimulated beginning at synchronized ovulation, whereas cows in the control group were superstimulated after synchronization of follicular wave emergence with estradiol plus progesterone (E2+P4). There were no differences in mean (± SD) numbers of transferable embryos between FFW+P4 (8.0 ± 4.5) and control (6.7 ± 4.8) groups, but both were higher (P = 0.006) than the FFW group (0.2 ± 0.4). In Experiment 2, FFW and FFW+P4 were compared in 20 Nelore donors; exogenous progesterone increased the number of transferable embryos (3.9 ± 3.4 vs. 1.3 ± 4.1, P = 0.003). In Experiment 3, FFW and FFW+P4 were compared in 10 Nelore donors except that cows were slaughtered 12 h after pLH (Lutropin-V^®, Bioniche Animal Health, Belleville, ON, Canada) treatment. More mature cumulus oocyte complex (COC) (expanded cumulus cell layers) were collected in the FFW+P4 group than in the FFW group (21.8 ± 13.1 vs. 10.8±14.7; P = 0.003). In summary, superovulatory response was satisfactory when FSH (Folltropin-V^®, Bioniche Animal Health) treatment was initiated at emergence of the first follicular wave in Nelore (Bos indicus) donors, and the hypothesis that administration of exogenous progesterone during the treatment will improve oocyte and embryo quality was supported.