AI Protocol Research Articles

Comparison of timed insemination versus modified estrus detection protocol in beef heifers

Our objectives were to evaluate a fixed-time AI (FTAI) protocol versus a modified estrus detection with fixed-time AI (MTAI) protocol on estrus synchronization and pregnancy rates. Angus-based, crossbred heifers (n = 971; 346 ± 14 kg) were estrus synchronized via a melengestrol acetate-prostaglandin F2α (PG) protocol. An estrus detection aid (patch) was applied at PG injection. Each heifer was assigned a patch score (reflecting the amount of rub-off coating removed) at AI to reflect estrus status. At 72 h following PG, FTAI heifers received a 2-mL gonadotropin-releasing hormone injection and were inseminated. Estrus was detected in MTAI heifers at 58 and 70 h after PG. Approximately 72 h after PG, MTAI heifers were inseminated in the following order: heifers in estrus at 58 h after PG, heifers in estrus at 70 h after PG, and heifers not appearing in estrus at either observation. Heifers not expressing estrus received gonadotropin-releasing hormone at AI. Pregnancy was determined via transrectal ultrasonography 51 d after AI. In both treatments, heifers exhibiting estrus had greater (P < 0.01) AI conception rates than heifers not expressing estrus (71 and 66 ± 5% for FTAI vs. MTAI, respectively, vs. 47 and 53 ± 9% in nonestrus heifers for FTAI and MTAI, respectively). However, overall AI pregnancy rate (62 ± 5%) and final pregnancy rates were similar between treatments (P ≥ 0.49; 97 ± 3%). Similar AI pregnancy rates were achieved without the added labor of estrus detection.

12 OVARIAN STRUCTURES, ESTRUS EXPRESSION, AND PREGNANCY RATE IN BEEF HEIFERS USING ESTRADIOL CYPIONATE OR GnRH AS OVULATION INDUCTORS IN TIMED AI PROTOCOL

The aim of this study was to evaluate the effect of presence of corpus luteum (CL) at the onset of timed AI (TAI) protocol, size of ovulatory follicle and oestrus expression on pregnancy rate using E2 cypionate (EC) or GnRH as ovulation inductor in Angus heifers. On day 0, heifers [n = 414; 317 ± 23 kg; 3.08 ± 0.21 body condition score (1 to 5 scale) and 22–24 months of age] received a 1-g progesterone intravaginal device (Primer®, Agener União, Brazil) and 2 mg of oestradiol benzoate, IM, (RIC-BE®, Agener União, Brazil). On day 8, the device was removed, were administered 500 μg of sodium cloprostenol, IM, (Estron®, Agener União, Brazil) and heifers were divided in 2 groups: EC [n = 213; 0.5mg EC, IM, (SincroCP®, Ouro Fino, Brazil) on day 8] and GnRH [n = 201; 25 μg of Licerelin, IM, (GestranPlus®, Agener União, Brazil) at TAI] TAI was performed 50 h after device removal. Heifers were tail painted (Tell Tail®, GEA, New Zealand) to control oestrus expression from device removal to TAI. Heifers were scanned (7.5-MHz linear transducer MediSono® P3V, USA) to determine presence of CL (Day 0), ovulatory follicle diameter (OFD; Day 10) and ovulation (Day 11). Pregnancy was diagnosed 30 days after TAI. Oestrus expression was confirmed when marking ink was removed on day 10. Data were analysed using logistic regression and ANOVA. Oestrus expression was higher (P &lt; 0.05) in EC (93.90%, 200/213) compared to GnRH group (67.66%, 136/201). The OFD differed (P &lt; 0.05) according to presence of CL on Day 0 (10.3 mm) or not (9.6 mm), but was similar in treatment groups. Ovulation rate did not differ in EC (85%, 17/20) and GnRH (95%, 19/20) groups. Pregnancy rates were similar (P &gt; 0.05) between EC (52.58%, 112/213) and GnRH (59.20%, 119/201) groups; however, in heifers that expressed oestrus, rates were higher (P &lt; 0.05) (EC = 56%, 112/200; GnRH = 71.3%, 97/136) than in those did not show (EC = 0%, 0/13; GnRH = 33.8%, 22/65). Presence of CL at onset of TAI protocol was associated with higher pregnancy (P &lt; 0.05) in GnRH group (68%, 68/100) compared with EC (54.46%, 61/112) group, but in heifers without CL, pregnancy were similar for GnRH (50.5%, 51/101) and EC (50.5%, 51/101) groups. Heifers were also classified in 3 groups according OFD: small (≤9.5 mm), medium (9.6–11.5 mm), and large (≥11.6 mm) to verify its effect on oestrus expression and pregnancy. Medium and large OFD were implicated in higher (P &lt; 0.05) oestrus expression [(EC = 100%, 51/51; 96.97%, 32/33) and (GnRH = 83.02%, 44/53; 97.44%, 38/39)] than small OFD [(EC = 85%, 51/60) and (GnRH = 23.8%, 15/63)]. Pregnancy was lower (P &lt; 0.05) in small OFD groups (EC = 28.3%, 17/60; GnRH = 25.4%, 16/63). In medium and large OFD, pregnancy was similar in EC (72.55%, 37/51; 54.55%, 18/33) groups, but differed (P &lt; 0.05) between GnRH large (82.05%, 32/39) and medium (62.26%, 33/53). Higher pregnancy was achieved in heifers with CL in the beginning of TAI protocol treated with GnRH. Size of ovulatory follicle was associated with higher oestrus behaviour and pregnancy rate in EC and GnRH treatments.

72 EFFECT OF PROGESTERONE SUPPLEMENTATION ON DAY 4 AFTER TIMED ARTIFICIAL INSEMINATION ON PREGNANCY RATE OF LACTATING DAIRY COWS

Progesterone plays an important role in the maintenance of pregnancy. It is hypothesised that insufficient progesterone early in pregnancy may result in embryonic loss, and that supplemental progesterone would decrease pregnancy loss in dairy cows. The aim of this study was to compare the effect of progesterone supplementation after timed AI on pregnancy rate of dairy cows. The experiment was conducted in a single commercial herd, in Sao Paulo State (Brazil), during a period of 1 year (January–December 2016). The cows were assigned at a nonpregnancy diagnosis 32 ± 3 days after AI to 1 to 6 resynchronization treatments. They were submitted to the same fixed time AI protocol: Day 0, 0.1 mg of gonadorelin, 2 mg of oestradiol benzoate, and an intravaginal device of 1.9 g of progesterone; Day 7, 25 mg of dinoprost tromethamine; Day 8, 25 mg of dinoprost tromethamine, 1 mg of oestradiol cipionate, and device withdrawal; Day 10, AI. At Day 14, the cows were alternately arranged in 2 groups. Group 1 received a 900-mg progesterone supplementation IM injection, and Group 2 did not receive progesterone supplementation. Then, 32 ± 3 days after insemination, pregnancy diagnosis was performed by transrectal ultrasonography, and the data were tabulated. Full statistical analysis will be done at the end of the study, when more than 500 cows will be allocated to the 2 groups. From January until April 2016, 230 lactating dairy cows were submitted to the experiment. Both groups had similar average days in lactation (166), average number of lactations (1.95), and average number of inseminations (4.3). Group 1 had a pregnancy rate of 25% (29/116), and group 2 had a pregnancy rate of 15.8% (18/114) (P = 0.01, one-way ANOVA). Based on these preliminary data, pregnancy rates of lactating dairy cows may be improved with progesterone supplementation on Day 4 after insemination. These results need to be confirmed on larger numbers of cows.

Development of fixed-time artificial insemination protocols for locally adapted Curraleiro Pé-Duro cows

ABSTRACT Two experiments were conducted aiming to evaluate the effects of two ovulatory inducers (Exp.1) and equine chorionic gonadotropin (eCG; Exp.2) on follicular and luteal dynamics in a fixed-time AI (FTAI) protocol in locally adapted Curraleiro Pé-Duro cows. In Exp. 1 multiparous cows (n=12) received an intravaginal device containing 1g of progesterone (P4) for 8 days and 2mg of estradiol benzoate (EB) intramuscularly (IM) at device insertion (Day 0). At device removal (Day 8) 0.150mg of Sodium D-Cloprostenol was administered IM and the cows were randomly assigned to receive 1mg of EB (EB8) or 1mg of estradiol cypionate (EC8) IM, or to not receive any ovulatory inducer (Control). All the animals participated in all treatments (crossover). The interval from P4 removal to ovulation was shorter and less variable in the EB8 treatment group (P≤0.05). In Exp. 2 (crossover), multiparous cows (n=12) received the same hormonal treatment as the EB8 group in Exp.1. At device removal (Day 8) cows were randomly assigned to receive 300UI of eCG IM or to not receive eCG (Control). No difference was ascertained on follicular and luteal parameters in Exp. 2 (P&gt;0.05). We concluded that EB can be used as the ovulatory inducer (Exp. 1) in a FTAI protocol in Curraleiro Pé-Duro cows. However, eCG (Exp. 2) was not able to stimulate follicular and luteal development. This result is probably due to the adaptive capacity of Curraleiro Pé-Duro cows that maintained a satisfactory body condition score even in dry and hot environments.

Effect of delayed insemination of nonestrus beef heifers in a melengestrol acetate–prostaglandin F2α timed artificial insemination protocol

ABSTRACT A study evaluated a 19-h-delayed AI following GnRH administration in a hybrid estrus detection and timed AI protocol. Angus-based, crossbred heifers (n = 453) managed at the Kelly Ranch (Sutherland, NE) or the University of Nebraska West Central Research and Extension Center (North Platte, NE) were synchronized using the melengestrol acetate–PGF2α protocol. Heifers were fed melengestrol acetate for 14 d (d 1 through d 14). Nineteen days later, on d 33, heifers received a PGF2α injection. Heifers (n = 319) expressing estrus were assigned to the first treatment group (EST), were removed from the herd, and received AI 12 h later. Seventy-two hours following the PGF2α injection, heifers not detected in estrus were administered GnRH and randomly assigned to 1 of 2 remaining treatment groups: immediate AI (n = 70, GNRH-I) or AI 19 ± 1 h following GnRH injection (n = 64, GNRH-D). Heifers artificially inseminated that had exhibited estrus had greater (P

Ovulation time in suckled beef cows is anticipated by use of low doses of progesterone and temporary calf removal on fixed timed AI protocol

This study was designed to evaluate the effect of concentrations of P4 during a fixed-time artificial insemination (TAI) protocol and 48 hours temporary calf removal (CR; i.e., calves were temporally weaned for 48 hours) or treatment with 300 IU of eCG on ovulation time in suckled beef cows. One hundred and fourteen Nellore cows were estrous synchronized by receiving an intravaginal P4 releasing device containing 1.9 g of P4 (CIDR) plus 2.0-mg estradiol benzoate on Day 0, 12.5-mg dinoprost tromethamine on Day 7, and CIDR removal plus 0.5-mg estradiol cypionate on Day 9. Concentrations of P4 (P4 conc.) were manipulated by insertion of a new CIDR containing 1.9 g of P4 (CIDR1) or a CIDR previously used for 9 days (CIDR2), 18 days (CIDR3), or 27 days (CIDR4). On Day 9, within CIDR uses, cows received either CR or eCG. On Day 11 (48 hours after CIDR removal), all cows received a single TAI. Estrus was observed twice, a day between Day 9 and TAI. Ovulation by 60 hours or 72 hours after CIDR removal was defined as the disappearance of the largest follicle (LF) detected on Day 11 and presence of CL on Day 18, determined by transrectal ultrasonography. Cows ovulating after 72 hours were deemed to have a dominant follicle at 60 hours and 72 hours but also had a CL on Day 18. Serum P4 conc. were evaluated on Days 9, 11, and 18. Cows from CIDR4 + CR treatment ovulated at 60 hours (53.3%) tended to be greater (P = 0.07) than CIDR4 + eCG (21.4%). For the remaining treatments, this effect was not detected (CIDR1 + eCG: 6.3% vs. CIDR1 + CR: 0.0%; CIDR2 + eCG: 6.7% vs. CIDR2 + CR: 12.5%; CIDR3 + eCG: 0.0% vs. CIDR3 + CR: 25%). As a consequence, the percentage of cows from CIDR4 + CR treatment ovulating by 72 hours (26.7%) was lesser (P < 0.05) than that of cows in the CIDR4 + eCG treatment (78.6%), but for the remaining CIDR uses ovulation was not affected. The analysis of ovulating time revealed that earlier ovulation was associated (P < 0.01) to: (a) lesser P4 conc. on Day 9 (2.69b, 3.36a, and 3.82a ng/mL, standard error of the mean [SEM]: 0.12); (b) greater LF on Day 11 (12.46a, 12.09a, and 11.06b mm, SEM: 0.34); (c) greater estrus rate (94.1%a, 80.0%a, and 28.6%b), for ovulation at 60 hours, 72 hours, or >72 hours, respectively. Thereafter, previously used CIDR resulted (P < 0.01) in lesser P4 conc. on Day 9 (4.84a, 3.24b, 3.00b, and 2.50c ng/mL, SEM: 0.12), greater LF (10.50b, 12.07a, 11.98a, and 12.33a mm, SEM: 0.18) but only CIDR4 increased (P < 0.05) estrus rate (53.1%b, 65.6%b, 57.9%b, and 90.3%a), for CIDR1, CIDR2, CIDR3, and CIDR4, respectively. In conclusion, cows with low concentrations of P4 during a TAI protocol exhibited increased follicle diameter and an increased rate of estrus. This resulted in a greater percentage of cows ovulating by 60 hours when they had experienced calf removal.

Expression of Na+/H+ exchanger isoforms 1, 2, 3, and 4 in bovine endometrium and the influence of uterine pH at time of fixed-time AI of pregnancy success

Cows that exhibit estrus prior to fixed-time AI had increased sperm transport to the site of fertilization, and improved embryo quality on d 6 after insemination. Sperm transport is influenced by uterine pH, and research has reported that uterine pH decreased at onset of estrus, but must return to normal prior to ovulation. Therefore, the objectives of these studies were to investigate a possible mechanism for the regulation of uterine pH around the onset of estrus, and to determine if uterine pH at time of fixed-time AI influenced pregnancy success. In experiment 1, Angus-cross beef cows (n=40 and 28 in rep. 1 and 2, respectively) were synchronized with the PG 6-day CIDR protocol (PGF2α on d -9, GnRH and insertion of a CIDR on d -6, and PGF2α and CIDR removal on d 0). Cows were blocked by follicle size at time of CIDR removal, and uterine biopsies were collected at 0, 12, 24, 36, 48, 60 (Rep. 1), 72, 84, or 96h (Rep2) after CIDR removal, and total cellular RNA was extracted from all biopsies. Estrus was monitored by the HeatWatch Estrous Detection System. In experiment 2, 223 postpartum beef cows in 2 herds were synchronized with a fixed-time AI protocol (herd 1: n=97; CO-Synch plus CIDR protocol; herd 2: n=126; Co-synch protocol). Uterine pH was determined at time of AI (n=80 and 63 for herd 1 and 2, respectively), and estrus was monitored by visual estrus detection with the aid of an ESTROTECT estrous detection patches, and pregnancy was determined by transrectal ultrasonography. In experiment 1, there was a significant (P<0.01), quadratic relationship in expression of Na+/H+ exchanger isoforms 1, 2, and 3 among animals that exhibited estrus, with expression greatest at time of CIDR removal, decreasing to the onset of estrus, and then increasing again following the onset of estrus. Among cows that did not exhibit estrus, the preceding relationship did not exist (P>0.46). In experiment 2, cows that had initiated estrus prior to fixed-time AI had decreased (P=0.01) uterine pH compared to cows that did not initiate estrus (6.78±0.03 and 6.89±0.03, respectively), and uterine pH at AI had an approximately linear effect on pregnancy success within the observed pH range. Furthermore, cows that initiated estrus prior to AI had increased (P=0.05) pregnancy success (52% vs. 38%) compared to cows that had not initiated estrus. In summary, expression of Na+/H+ exchanger isoforms 1, 2, and 3 decreased after CIDR removal among cows that exhibited estrus, but did not change among cows that did not exhibit estrus. Additionally, as uterine pH decreased pregnancy success tended to increase (P=0.076, logistics regression). Thus, Na+/H+ exchanger isoforms 1, 2, and 3 appear to be key regulators of uterine pH around the onset of estrus, and this change in uterine pH is critical for pregnancy success. Summary sentenceExpression of Na+/H+ exchanger isoforms 1, 2, and 3 decreased after CIDR removal among cows that exhibited estrus, but did not change among cows that did not exhibit estrus, and as uterine pH decreased, pregnancy success tended to increase.

Effects of recombinant bovine somatotropin administration at breeding on cow, conceptus, and subsequent offspring performance of beef cattle.

The effects of administration of recombinant bovine ST (bST) on plasma hormone concentrations of cows, conceptus development, and postnatal calf performance were examined. Lactating beef cows ( = 190) were exposed to a fixed-time AI (TAI) protocol from d -10 to 0 (TAI on d 0). Cows were blocked by breed and stratified by days postpartum and then randomly assigned to receive, subcutaneously 1) 2 injections of saline (1 mL of 0.9% saline), 1 on d 0 at TAI and a second injection on d 14 (CTRL; = 53); 2) an injection of 325 mg of bST on d 0 and a saline injection on d 14 (bST0; = 48); 3) a saline injection on d 0 and an injection of 325 mg of bST on d 14 (bST14; = 49); or 4) 2 injections of 325 mg of bST, 1 on d 0 and a second injection on d 14 (bST0+14; = 40). Pregnancy status, crown-to-rump length (CRL) on Day 35, and crown-to-nose length (CNL) on Day 65 were determined via transrectal ultrasonography. Blood samples were collected on d 0, 7, 14, 21, 35, and 65, relative to TAI, to determine plasma concentrations of progesterone (P4), IGF-1, and pregnancy-specific protein B (PSPB) and also on d 18 and 21 for isolation of peripheral blood leukocytes for RNA extraction and measurement of interferon-stimulated genes transcript abundance. Individual calf BW was determined at birth and every 30 d until weaning. A subset of 24 calves was randomly selected for liver biopsies at birth to determine mRNA expression of target genes. Administration of bST to cows increased ( < 0.0001) concentrations of plasma IGF-1 for 14 d after injection compared with CTRL but did not affect fetal CRL and CNL ( = 0.23). Cows receiving bST only on d 0 had a greater ( = 0.05) transcript abundance in myxovirus resistance 2 on d 21 compared with 2bST cows (2.0- and 0.8-fold for bST0 and 2bST, respectively), whereas cows receiving bST14 and CTRL were intermediate (1.2- and 0.9-fold, respectively). Calf BW did not differ ( ≥ 0.100) among treatments on d 0, 30, 60, 90, 120, and 150 relative to birth. Injection of bST only on d 0 tended ( = 0.062) to increase calf liver mRNA expression of at birth compared with the calves born to cows in other treatments. Therefore, during a TAI protocol, the administration of 1 or 2 injections of 325 mg of bST to lactating beef cows enhanced their plasma concentrations of IGF-1 but failed to improve fetal size and plasma concentrations of maternal PSPB and P4 and had no effect on postnatal calf growth performance.

098 Impact of elevated preovulatory estradiol during a fixed-time AI protocol on uterine environment and embryonic survival to Day 16

098 Impact of elevated preovulatory estradiol during a fixed-time AI protocol on uterine environment and embryonic survival to Day 16

315 Relationship between ovarian reserve and preovulatory estradiol during a fixed-time AI protocol in beef heifers

315 Relationship between ovarian reserve and preovulatory estradiol during a fixed-time AI protocol in beef heifers

Expression of estrus before fixed-time AI affects conception rates and factors that impact expression of estrus and the repeatability of expression of estrus in sequential breeding seasons

Expression of estrus after PG and before fixed-time AI has been reported to change the uterine environment, increase accessory sperm numbers, fertilization rates, and overall embryo survival. Thus, expression of estrus can strongly impact overall pregnancy success. Because of variation in percentage of beef females detected in estrus and number of animals per study, it can be difficult to detect a significant effect of estrus on pregnancy success. Thus, a meta-analysis was conducted using data from 10,116 beef females in 22 studies that utilized variations of the 5 most common fixed-time AI protocols (CO-Synch, 7-day CO-Synch+CIDR, 5-day CIDR, PG 6-day CIDR, and the 14-day CIDR protocols) to examine the effect of detection in standing estrus on subsequent fixed-time AI pregnancy success. A random-effects model was used to combine the studies/herds. The overall model indicated a positive effect of estrus on conception rates with cows detected in estrus before fixed-time AI having a 27% greater (P<0.05; 95% CI=22–32%) conception rate compared with those not detected in estrus. Next we determined factors that influenced expression of estrus. Data were available on 547 cows synchronized with a CIDR based fixed-time AI protocols and observed for estrus before AI during 2–4 breeding seasons. Analysis of these cows indicated that days postpartum (P=0.22) did not impact estrous expression. In contrast, BCS influenced estrous expression (P=0.04) with cows in a BCS of ≤4 (51±5%) having decreased expression of estrus compared to cows with a BCS>4 (≥70±4%). Initiation of estrous cycles before the breeding season also influenced estrous expression (P=0.03), with anestrous cows having greater expression of estrus compared with estrus-cycling cows (78±5% vs. 70±5%, respectively). In conclusion, among all currently recommended fixed-time AI protocols, cows detected in estrus before fixed-time AI had improved conception rates, with BCS and estrus-cycling status having the greatest influence on expression of estrus.

Effects of vaccination against foot-and-mouth disease virus on reproductive performance of beef cows.

This study compared reproductive performance of cows vaccinated against the foot-and-mouth disease (FMD) virus before timed AI or during early pregnancy (Exp. 1), as well as rectal temperature (RT) and plasma concentrations of the acute-phase protein haptoglobin in cattle vaccinated or not against the FMD virus (Exp. 2). Cattle utilized in Exp. 1 and 2 originated from herds with no historical occurrences of FMD and that received vaccination against the FMD virus biannually. In Exp. 1, 604 lactating, multiparous, nonpregnant Nelore cows were randomly assigned on d -31 of the experiment to receive 1) vaccination against the FMD virus on d ≥ 31 (VACPRE; = 291) and 2) vaccination against FMD virus on d 30 (VACGEST; = 313). From d -11 to 0, all cows were assigned to an estrus synchronization + timed AI (d 0) protocol. Pregnancy status to AI was verified on d 30 and 90 via transrectal ultrasonography. A treatment × day interaction was detected ( < 0.01) for pregnancy rates to AI, which were similar ( = 0.17) between VACPRE and VACGEST on d 30 (61.8% vs. 56.2%, respectively; SEM = 2.8) but greater ( < 0.01) for VACPRE on d 90 (59.4% vs. 46.9%, respectively; SEM = 2.8). Pregnancy loss from d 30 to 90 was greater ( < 0.01) in VACGEST compared with VACPRE (16.5% vs. 3.9%, respectively; SEM = 2.2). In Exp. 2, 40 pregnant Nelore females (20 nulliparous and 20 multiparous cows; BCS = 4.73 ± 0.12) were ranked by parity and assigned to receive (VAC; = 20) or not receive (NOVAC; = 20) vaccination against the FMD virus. Blood samples were collected and RT was recorded before (h 0) and 24, 72, 120, and 168 h after treatment administration. Treatment × day interactions were detected ( < 0.01) for RT and plasma haptoglobin. The RT was greater ( < 0.01) in VAC compared with NOVAC at 24 h after treatment administration and was similar ( ≥ 0.31) between treatments at all other sampling hours. Plasma haptoglobin concentration was similar ( = 0.98) between VAC and NOVAC before treatment administration ( = 0.48) and greater ( < 0.01) in VAC at 24, 72, 120, and 168 h after treatment administration. In summary, vaccinating beef cows against the FMD virus resulted in a 4-fold increase in pregnancy loss when the vaccine was administered 30 d after timed AI compared with 31 d before timed AI. These outcomes can be associated with inflammatory and acute-phase reactions elicited by the FMD vaccine, which are known to impair pregnancy maintenance in cattle.

Endocrine and metabolic differences between Bos taurus and Bos indicus cows andimplications for reproductive management

Based on the considerable differences in ovarian morphology and function, as well as circulating hormones and metabolites between Bos indicus (B. indicus) and Bos taurus (B. taurus), researchers are using this acquired knowledge to optimize protocols for fixed-time artificial insemination (FTAI), and production of in vivo derived embryos by multiple ovulation or by in vitro embryo production (IVP). In B. indicus, at the time of follicle deviation, the dominant follicle is smaller and acquires ovulatory capacity at a smaller diameter than B. taurus. Moreover, despite ovulating smaller follicles and having smaller corpora lutea (CL), circulating concentrations of estradiol (E2) and progesterone (P4) are greater in B. indicus than B. taurus. These physiological differences may be related to greater circulating cholesterol, insulin and IGF1 in B. indicus than in B. taurus. For both genetic groups there is a negative relationship between circulating P4 and ovulatory response to the first GnRH treatment of a fixed-time AI (FTAI) protocol. Moreover, despite lower clearance rates of steroid hormones in B. indicus than B. taurus, the dose of 2 mg estradiol benzoate seems to be the most effective either for Nelore (B. indicus beef), Angus (B. taurus beef), or Holstein (B. taurus dairy) cows at the initiation of an E2/P4-based FTAI protocol to optimize synchronization and pregnancy per AI (P/AI). Several studies have shown that only one recommended dose of PGF2α at a FTAI protocol may be insufficient for adequate luteolysis in B. indicus and B. taurus. When submitted to multiple ovulation and embryo transfer, B. indicus cows and heifers need less FSH than B. taurus to achieve superovulation. Moreover, IVP has been more successful in B. indicus than B. taurus due to greater antral follicle count and anti-mullerian hormone, and better oocyte quality

Impacts of meloxicam administration before temporary calf weaning on physiological and reproductive responses of Bos indicus beef cows1

The objective of this experiment was to evaluate temperament, physiological, and reproductive variables in beef cows assigned to an estrus synchronization + timed AI protocol including eCG administration, 48-h temporary calf weaning (TCW), or TCW + meloxicam administration. A total of 943 lactating, multiparous, nonpregnant Nelore cows, allocated into 8 groups of approximately 120 cows each, were assigned to the experiment. Groups were maintained in individual pastures and assigned to the following estrus synchronization + timed AI protocol: a 2-mg injection of estradiol benzoate and an intravaginal progesterone-releasing device (CIDR) on d 0, a 12.5-mg injection of PGF on d 7, CIDR removal in addition to a 0.6-mg injection of estradiol cypionate on d 9, and timed AI on d 11. Within each group, cows were randomly assigned on d 9 to 1) TCW from d 9 to 11 (TCW-CON; = 317), 2) no TCW and a 300-IU injection of eCG on d 9 (NOTCW; = 311), and 3) TCW-CON in addition to meloxicam administration (intramuscular; 0.5 mg/kg BW) on d 9 (TCW-MEL; = 315). Cow BW and BCS were assessed on d 0. On d 9 and 11, blood samples were collected, and cow temperament was evaluated via chute score and exit velocity. Pregnancy status was verified 30 d after timed AI via transrectal ultrasonography. No treatment differences were detected ( ≥ 0.23) for cow age, days postpartum, BW, and BCS on d 0 of the estrus synchronization + timed AI protocol. No treatment effects were detected ( ≥ 0.41) for any of the temperament variables evaluated. A treatment × day interaction was detected ( = 0.02) for serum cortisol concentrations, which were similar ( = 0.55) between treatments on d 9 but greater ( ≤ 0.05) in TCW-CON and TCW-MEL compared with NOTCW cows on d 11. No treatment effects were detected ( = 0.90) for serum haptoglobin concentrations, which decreased from d 9 to 11 in all treatments (day effect; < 0.01). No treatment differences were detected ( = 0.84) for pregnancy rates to timed AI. In summary, TCW during estrus synchronization did not impact temperament or serum haptoglobin concentrations in beef cows but increased serum cortisol concentrations compared with cows not assigned to TCW, although such an outcome was not sufficient to impact pregnancy rates to timed AI. Moreover, administration of meloxicam did not alleviate the TCW-induced increase in serum cortisol concentrations and failed to benefit pregnancy rates to timed AI in beef cows.

Gestación en vacas lecheras con dos protocolos de sincronización de la ovulación e inseminación a tiempo fijo

Se comparó la tasa de gestación (TG) en vacas lecheras inseminadas a tiempo fijo mediante dos protocolos. El día 32 posparto, 275 vacas recibieron dos inyecciones de PGF2α con intervalo de 14 días. Doce días después de la segunda inyección, se asignaron a los siguientes tratamientos: 1) Ovsynch (n=144) recibieron GnRH; siete díasdespués PGF2α; 56 h más tarde GnRH y se inseminaron 16 h después 2) PRID5d (n=131) recibieron GnRH y un dispositivo intravaginal liberador de progesterona durante cinco días; al retirar el dispositivo, se aplicaron dosinyecciones de PGF2α con intervalo de 24 h; 56 h posterior al retiro del dispositivo, se aplicó GnRH y se inseminaron 16 h después. La gestación se diagnosticó por palpación rectal el día 45 posinseminación. Se comparó la TG mediante regresión logística. Las variables independientes fueron: tratamiento (Ovsynch vs PRID5d), producción láctea (≤40 vs &gt;40 kg), técnico inseminador (1 vs 2), tipo de puerperio (normal vs anormal), partos previos (primíparas vs multíparas) y si mostraron estro en la presincronización. La TG fue similar (P&gt;0.1) entre los tratamientos (27 vs 21 %; Ovsynch y PRID5d, respectivamente). Ninguna de las otras variables independientes afectó la TG (P&gt;0.1); no hubo efecto de la interacción de dichas variables con el tratamiento en la TG (P&gt;0.1). Se concluye que la TG fue similar entre las vacas inseminadas con un protocolo Ovsynch o mediante un protocolo Ovsynch modificado que incluyó 5 días de progesterona y la reducción de 7 a 5 días entre la inyección de GnRH y la PGF2α.

7 KISSPEPTIN SLOWLY ADMINISTERED DURING PROESTRUS IMPROVES FOLLICLE GROWTH AND OVULATION IN ANESTROUS COWS

This study evaluated whether kisspeptin (Kp) administered slowly from the moment of prostaglandin F2α (PGF) treatment for fixed-time AI protocol of anestrous cows provides suitable dominant follicle (DF) growth similarly to eCG. Postpartum, anestrous, primiparous Nelore cows (n = 50; &lt;8-mm follicles with no corpus luteum) and lean (body condition score 2.7 ± 0.1; 0–5 score scale) were enrolled. On Day 0, females received an intravaginal device with 1.0 g of progesterone (Sincrogest®, Ourofino, Brazil) and 2 mg of oestradiol benzoate IM (Sincrodiol®, Ourofino, Brazil). On Day 8, the device was removed, and cows were administered 500 μg of sodic cloprostenol IM (Sincrocio®, Ourofino, Brazil) and 1 mg of oestradiol cypionate IM (E.C.P.®, Zoetis, Brazil). Females were blocked by dominant follicle diameter and allotted in following groups: (1) control (CTRL), 1.5 mL of saline IM; (2) eCG, 300 IU IM of eCG (Novormon®, Intervet, Brazil); and (3) Kp SC with an osmotic minipump (9.65 μg kg–1 of Kp diluted in saline) over 48 h. Dominant follicle growth and ovulation evaluation were performed by ultrasound at 0, 24, 48, 60, 72, 84, and 96 h after PGF treatment. Dominant follicle growth rate was calculated by difference on DF from 0 to 48 h. Ovulation dispersion was analysed by proc GLIMMIX of SAS (SAS Institute Inc., Cary, NC, USA). Follicle variables, ovulation rate, and interval from PGF to ovulation were analysed by orthogonal contrast. Differences were considered when P &lt; 0.05, and tendencies were considered when P &lt; 0.1. There were no difference between CTRL and growth promoters (eCG and Kp) or between growth promoters on DF diameter at 0 h, larger follicle registered from 0 h to ovulation, ovulatory DF diameter, ovulation rate, and interval between PGF treatment and ovulation (Table 1). Dominant follicle diameter at 48 h was larger for growth promoters than for CTRL. Treatment with Kp proved as efficient as eCG in the DF growth rate, with tendency (P = 0.1) to be greater than CTRL. Data from our laboratory (Sales et al. 2011 Anim. Rep. Sci. 124, 12–18.) with same model and animal profile (n = 150 per group) presented positive effect of eCG treatment for growth and size of DF. Cows treated with Kp ovulated in only 3 specific times (60, 72, and 84 h), unlike eCG (48, 60, 72, and 84 h) and CTRL (24, 48, 60, 72, 84, and 96 h; P &gt; 0.05). Also, it is noted that Kp treatment dose and releasing does not cause negative effect on follicle growth and ovulation (down-regulation on LH releasing) or alteration on interval of PGF treatment to ovulation. Thus, synchronized anestrous cows treated with Kp delivered slowly during proestrus have similar results to eCG on follicle growth and ovulation. Table 1.Ovarian variables of anestrous Nelore cows treated with saline, eCG (300 IU), or kisspeptin (Kp; 9.65 μg kg–1). Data were analysed by orthogonal contrast, where C1 = growth promoter (eCG and Kp) v. control; C2 = eCG v. Kp

Effects of administration of prostaglandin F at initiation of the seven-day CO-Synch+controlled internal drug release ovulation synchronization protocol for suckled beef cows and replacement beef heifers.

Two experiments were conducted to determine the effect of administering PGF at the initiation of the 7-d CO-Synch+controlled internal drug release (CIDR) fixed-timed AI (TAI) protocol on pregnancy rates of suckled beef cows and replacement heifers. Within location, cows were stratified by days postpartum (DPP), BCS, and parity (Exp. 1; = 1,551) and heifers were stratified by BCS (Exp. 2; = 999) and randomly assigned to 1 of 2 treatments: 1) CO-Synch+CIDR (100-μg injection of GnRH at CIDR insertion [d -10] with a 25-mg injection of PGF at CIDR removal [d -3] followed by injection of GnRH and TAI on d 0) or 2) PG-CO-Synch+CIDR (a 25-mg injection of PGF on d -10 of the CO-Synch+CIDR protocol). Follicle diameter and corpus luteum (CL) development were assessed on d -10 and -3, and pregnancy status was determined on d 30 to 35. Blood was collected on d -20, -10, -3, and 0 relative to TAI to determine concentrations of progesterone (P4). In Exp. 1, TAI pregnancy rates did not differ ( = 0.667) between treatments and were affected by BCS ( = 0.003) and DPP ( = 0.006). Concentrations of P4 were greater ( < 0.0001) on d -3 for CO-Synch+CIDR than for PG-CO-Synch+CIDR (4.1 ± 0.2 and 3.4 ± 0.2 ng/mL, respectively). Follicle diameter on d -3 differed ( = 0.05) between PG-CO-Synch+CIDR (13.4 ± 0.3 mm) and CO-Synch+CIDR (12.5 ± 0.3 mm) treatments. Cows with P4 > 2.5 ng/mL on d -10 had greater ( = 0.024) pregnancy rate to TAI (56.5%) compared with cows with 2.5 ng/mL < P4 > 1 (43.0%), whereas cows with P4 < 1 ng/mL were intermediate (51.6%). Cows with a CL on d -10 had greater ( = 0.012) pregnancy rates to TAI than cows without a CL (66.3 vs. 39.4%, respectively). In Exp. 2, TAI pregnancy rates did not differ ( = 0.316) between treatments. Concentrations of P4 differed ( < 0.0001) on d -3 with greater concentrations of P4 for CO-Synch+CIDR than for PG-CO-Synch+CIDR (3.75 ± 0.20 ng/mL and 3.60 ± 0.21 ng/mL, respectively). Follicle diameter was similar ( = 0.749) between treatments on d -10 and -3. Regardless of treatment, cyclic status tended ( = 0.062) to improve pregnancy rates to TAI (55 vs. 45%, for cycling and noncycling heifers, respectively). We concluded that addition of PGF to the 7-d CO-Synch+CIDR protocol decreased concentrations of P4 in cows and heifers and increased follicle diameter at CIDR removal in cows but failed to increase TAI pregnancy rates.

Inducing ovulation with oestradiol cypionate allows flexibility in the timing of insemination and removes the need for gonadotrophin-releasing hormone in timed AI protocols for dairy cows.

The effects of addition of gonadotrophin-releasing hormone (GnRH) to a progesterone plus oestradiol-based protocol and timing of insemination in Holstein cows treated for timed AI (TAI) were evaluated. Cows (n=481) received a progesterone device and 2mg oestradiol benzoate. After 8 days, the device was removed and 25mg dinoprost was administered. Cows were allocated to one of three (Study 1; n=57) or four (Study 2; n=424) groups, accordingly to ovulation inducer alone (Study 1; oestradiol cypionate (EC), GnRH or both) or ovulation inducer (EC alone or combined with GnRH) and timing of insemination (48 or 54h after device removal; Study 2). In Study 1, the diameter of the ovulatory follicle was greater for GnRH than EC. Oestrus and ovulation rates were similar regardless of ovulatory stimuli. However, time to ovulation was delayed when GnRH only was used. In Study 2, cows treated with GnRH or not had similar pregnancy per AI (P/AI) 30 days (41.5% vs 37.3%; P=0.28) and 60 days (35.9% vs 33.0%; P=0.61) after TAI. TAI 48 and 54h after device removal resulted similar P/AI at 30 days (40.3% vs 38.5%; P=0.63) and 60 days (33.8% vs 35.1%; P=0.72). Thus, adding GnRH at TAI does not improve pregnancy rates in dairy cows receiving EC. The flexibility of time to insemination enables TAI of a large number of cows using the same protocol and splitting the time of AI.

Use of estradiol benzoate to induce ovulation in a short-term protocol for fixed-time AI in sheep

O objetivo do presente estudo foi testar protocolo hormonal para inseminacao em tempo fixo (IATF) usando dispositivo de progesterona vaginal por seis dias e aplicacao de eCG (gonadotrofina corionica equina) ou BE (benzoato de estradiol) como indutor de ovulacao em ovelhas. No dia 0 (D0), as ovelhas (n=31) receberam CIDR e foram divididas em tres grupos. O grupo controle (G-CT) usou CIDR por nove dias e na retirada do dispositivo foi administrado PGF2a e eCG. No grupo eCG (G-eCG), CIDR foi mantido por seis dias, ao inves de nove como no G-CT, com aplicacao de PGF2a e eCG na retirada da progesterona. No grupo benzoato de estradiol (G-EB), o CIDR tambem foi administrado por seis dias, mas nao foi utilizado eCG, o BE foi usado para induzir ovulacao e foi aplicado 24 horas apos a remocao do CIDR e administracao de PGF2a. A IATF foi feita em todos os grupos 50h apos a retirada do CIDR. A taxa de prenhez do G-eCG (66%) foi maior (p 0,05) do G-CT (30%). E possivel reduzir o tempo de permanencia da progesterona usando eCG para IATF em ovelhas, entretanto o uso de BE resultou em baixa taxa de ovulacao.

Effect of interval from induction of puberty to initiation of a timed AI protocol on pregnancy rate in Nellore heifers

Prepubertal Bos indicus heifers (n = 774) were submitted to an E2/P4-based timed artificial insemination (TAI) protocol at three different intervals after induction of their pubertal ovulation by insertion of an intravaginal progesterone (P4) device for 12 days. Heifers were randomly assigned to start the TAI protocol at 10 (group 10; n = 253), 12 (group 12; n = 265), or 14 (group 14; n = 256) days after the P4 device was removed. The TAI protocol consisted of the following: insertion of intravaginal device containing P4 (Controlled internal drug release [CIDR]; previously used twice for 9 days each) + estradiol benzoate (2 mg) on Day 0, CIDR withdrawal + estradiol cypionate (0.5 mg) and PGF2α (12.5 mg) on Day 9, and TAI on Day 11. A subgroup of heifers (n = 472) was evaluated by ultrasound on Days 9 and 11 to evaluate the ovaries and to determine P4 concentrations on Day 9. On Day 9, more (P < 0.05) CLs were present, and follicular diameter was smaller (P < 0.05) for group 10 than for groups 12 and 14 (38.4%, 29.3%, and 23.3% with CL and 9.4 ± 0.1, 9.9 ± 0.1, and 9.8 ± 0.1 mm diameter, respectively), but P4 concentrations did not differ (P > 0.1) between treatments (2.4 ± 0.06 ng/mL). Follicular diameter at TAI (11.08 ± 0.09 mm) and ovulation rate (88.4%) did not differ between treatments (P > 0.1). However, conception and pregnancy rates for all heifers were greater (P < 0.05) in group 12 (50.4% and 45.5%, respectively) than in group 10 (38.2% and 33.7%, respectively), with group 14 intermediate to other treatments (45.6% and 40.6%, respectively). The final pregnancy rate did not differ between treatments (80.9%). In conclusion, a 12-day interval from the end of the puberty induction protocol to the start of the TAI protocol resulted in greater conception and pregnancy rates in prepubertal Nellore heifers.