Timed AI Protocol Research Articles

Pregnancy and Embryonic Loss Among Timed Artificial Insemination Protocols in Post-partum Dairy Buffaloes (Bubalus bubalis)

The aims of the study were to determine the pregnancies and embryonic losses following Timed Artificial Insemination (TAI) protocols and to generate strategic breeding management for buffaloes. In Study 1, buffaloes in natural estrus were inseminated, serving as Control (T1). In T2, buffaloes were subjected to the Controlled Internal Drug Release-Synch-human Chorionic Gonadotropin (CIDR-Synch-hCG) protocol. In T3, animals were subjected to Prostaglandin protocol, and T4 is similar to T3 except that hCG was supplemented on the Day of AI. In Study 2, buffaloes were subjected to the CIDR-Synch-hCG protocol, and the sizes of pre-ovulatory follicles were measured as the basis for the conduct of TAI. In Study 3, animals were similarly subjected to the CIDR-Synch-hCG protocol at different seasons. Results in Study 1 indicate that the CIDR-Synch-hCG protocol achieved pregnancy rates on Days 30 and 60 post-AI and embryonic loss, which are not significantly different (P<0.05) from those of natural estrus (T1), and that the Prostaglandin protocol supplemented with hCG (T4) resulted in significantly higher pregnancies and lower embryonic loss compared with Prostaglandin alone (T3) group. In Study 2, inseminating buffaloes with ≥12.0 mm pre-ovulatory follicle size (T3) yielded the highest pregnancies (P<0.05) at Days 30 and 60 with the lowest (P<0.05) embryonic loss among follicle size groups. In Study 3, TAI performed during January-March and October-December indicated significantly higher pregnancies (P<0.05) with lower embryonic loss (P<0.05) compared with the April-June and July-September seasons. In sum, the present study demonstrated the efficiencies of Timed AI protocols, which provided opportunities for their strategic use in breeding programs to achieve greater productivity and profitability from buffalo farming.

Effect of circulating prolactin, lactation days, and seasonal variations on first artificial insemination pregnancy rates using the PG7G protocol in dairy cows

Background and Aim: Dairy farm profitability is linked to milk yield and reproductive efficiency. High prolactin levels during lactation can negatively impact fertility. Timed AI protocols like PG7G are used to improve pregnancy rates. This study investigates the effects of extending the voluntary waiting period (VWP) from 63 to 73 days after the PG7G protocol on reproductive parameters, including progesterone and prolactin levels, pregnancy rates, and pregnancy losses, in lactating Holstein cows during summer and winter seasons. Materials and Methods: A total of 2100 lactating dairy cows were divided into groups and assigned to the PG7G protocol based on their parity. Two groups were formed based on the number of days in milk (DIM) after the first PGF2α injection. The first group (PG7G-63) received a PGF2α injection 30-day postpartum (pp) and followed a specific protocol. The second group, PG7G-73, followed the same protocol but received a PGF2α injection 40-day pp. Pregnancy was confirmed, and blood samples were collected for analysis. Temperature and humidity were also recorded throughout the study. Results: Extension of the VWP to 73-day (PG7G-73 group) significantly improved pregnancy rates on day 47 pp compared with the 63-day VWP (PG7G-63 group). However, the PG7G-63 group exhibited lower PLs. Seasonality markedly influenced reproductive outcomes, with higher P/AI in the moderate season for primiparous cows and in the hot season for multiparous cows. Conversely, PL in both groups increased during the hot season. Conclusion: Extending the VWP from 63 to 73 days pp in lactating Holstein cows significantly improved pregnancy rates, while seasonality affected reproductive outcomes, with higher pregnancy rates in moderate temperatures and increased pregnancy loss during hot seasons. Keywords: dairy cows, days in milk, pregnancy rate, prolactin, season, timed artificial insemination.

PSIII-6 Multi-sire artificial insemination of beef heifers in the Nebraska Sandhills effect on pregnancy rate compared with single-sire insemination

Abstract The objective of this study was to compare pregnancy outcomes resulting from artificial insemination (AI) with multi-sire semen (MS) compared with single-sire semen (SS) in beef heifers. Another study observed pregnancy and paternity outcomes to sexed MS without a control treatment. In the first study, unrelated ABS Global Angus bulls (n = 3) were selected for AI to 441 (Yr 1) and 391 (Yr 2) Angus crossbred heifers. Heifers were synchronized with the melengestrol acetate – prostaglandin F2α timed-AI protocol. Conventional semen, from each bull, were labeled A, B, or C. Remaining semen was pooled in equal amounts to form conventional MS straws. Heifers were AI using alternating treatment of MS or SS: A, B, or C with one-half of inseminated heifers receiving either MS or SS. The GLIMMIX procedure in SAS 9.4 analyzed responses to treatments using the BIN distribution option and reported as LSMEANS. Contrasts and estimates analyzed responses between treatments. Ultrasound determined SS pregnancy rate averaged 60% (SS-A = 64%, SS-B = 58%, SS-C = 58%) and MS average 62% (P = 0.63). Paternity was determined in 57 MS calves and confirmed in 49 SS calves. In Yr 1, Bull A sired 7%, bull B sired 56%, and bull C sired 37%. Although bull A was much less successful than bull B or C, the values are not significantly different due to the small sample size (P = 0.11 and P = 0.24, respectively). Few conclusions can be made from the ongoing study, but it is hypothesized MS may improve consistency of pregnancy rate by equilibrating semen quality in herds subjected to timed AI. In the observational study, multiple 5-way cross bulls born from the ranch herd were selected for AI of 951 ± 41 heifers for 3 yr. Heifers were synchronized using the previously mentioned protocol with split-time AI. Unequal amounts of semen were collected, pooled, and sexed to favor heifer progeny at an expected ratio of 9:1. Semen from 2 to 4 random bulls were pooled making 3 to 4 MS groups each year. Heifers exhibiting estrus were administered sexed MS, but there was no control treatment. The observed ultrasound determined average pregnancy rate of heifers administered sexed MS was 65% (Yr 1), 75% (Yr 2), and 72% (Yr 3). Previous literature suggests average pregnancy rate to AI with sexed SS is 53%. Paternity testing in Yr 2 found semen contribution mirrored paternity ratios within some groups but the sire group with 2 bulls found one sired 15% and the other sired 85%. This study exemplified a viable method for AI that requires further research. Further research into semen quality of a single sire, and pooled semen could lead to optimization of fertilization among individuals within a herd.

Comparison of two intravaginal progesterone-releasing devices in lactating Holstein cows synchronized with a 5-d GnRH-based timed-AI protocol

The objective of the study was to compare the effectiveness of CIDR vs. PRID-Delta devices for use in a 5-day Ovsynch protocol for TAI in lactating Holstein cows that were either not in estrus after the end of the voluntary waiting period or non-pregnant and not returning to estrus following the previous AI. Cows fitted with a collar-mounted automated activity monitoring system (Alta Cow Watch) were subjected to a standard 5-d Ovsynch protocol [100 μg of gonadorelin (GnRH) on Day 0 and 500 μg of cloprostenol on Days 5 and 6] and allocated randomly to receive either an intravaginal device containing 1.35 g (CIDR; n = 304) or 1.55 g (PRID ® DELTA; n = 304) of progesterone between Day 0 and 5. All cows received a second administration of GnRH at approximately 56 h and timed-AI (TAI) 72 h after intravaginal device removal. Inseminations were done using conventional frozen-thawed semen. Estrus events prior to TAI were recorded and transrectal ultrasonography was done on Day 0 to determine presence of a corpus luteum (CL) and 33 and 61 d post-TAI, respectively, to diagnose and confirm pregnancy. Cows had an average of 2.2 lactations, 124.3 days in milk, and a milk yield of 43.6 kg/d at enrollment. The overall percentage of cows with a CL at initiation of treatment was 68.8 % and did not differ between treatment groups. Cows with a CL had greater pregnancy per AI (P/AI) at 33 and 61 d post-TAI than cows without a CL (P < 0.01; 46.9 and 42.3 % vs. 32.1 and 27.4 %, respectively). The overall percentage of cows that expressed estrus prior to TAI was 24.8 % and did not differ between treatment groups; however, estrus expression prior to TAI affected P/AI at 33 and 61 d post-TAI (P < 0.01; 53.6 and 49.0 % vs. 38.5 and 33.9 % for those expressing or not expressing estrus, respectively). Pregnancy per AI at 33 d post-TAI tended to differ between treatment groups (P = 0.08; 46.1 vs. 38.5 % for PRID and CIDR groups, respectively) and P/AI at 61 d post-TAI was greater (P < 0.01) for PRID-treated cows (43.8 %) compared to CIDR-treated cows (31.6 %). Thus, PRID-treated cows had lower pregnancy loss than CIDR-treated cows (P < 0.01; 5.0 vs. 17.9 %). Also, treatment with a PRID tended (P = 0.08) to result in fewer twin pregnancies (7.9 vs. 14.5 % for PRID and CIDR treated cows, respectively). In conclusion, lactating dairy cows subjected to a 5-d Ovsynch TAI protocol plus a PRID-Delta had greater P/AI at 61 d post-TAI, lower pregnancy loss between 33 and 61 d post-TAI, and fewer twin pregnancies compared to cows subjected to a 5-d Ovsynch protocol plus a CIDR.

Reproductive outcomes in Holstein heifers synchronized with timed-AI protocols that provide for a lengthened proestrus.

This study compared reproductive outcomes among two protocols for synchronization of ovulation that provide for a lengthened proestrus with the conventional oestradiol-based protocol currently used for timed-AI (TAI). Holstein heifers (13-15 months) at one location were assigned randomly to one of three TAI protocols. Heifers (n = 150) in the 7-day oestradiol benzoate (EB) group received a progesterone device (Cue-Mate) and 2 mg EB on Day 0; 500 μg of cloprostenol (PGF) and Cue-Mate removal on Day 7; 1 mg of EB on Day 8 and TAI on Day 9 (54 h after Cue-Mate removal). Heifers (n = 150) in the 5-day CO-Synch (CO) group received a Cue-Mate and 100 μg of gonadotropin-releasing hormone (GnRH) on Day 2; Cue-Mate removal and PGF (twice, 12 h apart) on Day 7; and GnRH along with TAI on Day 10 (72 h after Cue-Mate removal). Heifers (n = 150) in the J-Synch (JS) group received a Cue-Mate and 2 mg of EB on Day 1; PGF and Cue-Mate removal on Day 7; GnRH and TAI on Day 10 (72 h after Cue-Mate removal). Heifers were inseminated by one technician with frozen-thawed conventional semen from one of four commercially available sires. Plasma progesterone (P4) concentrations (ng/mL) were determined at Cue-Mate removal and TAI. Ovarian ultrasonography was done in a subset of 217 heifers at the initiation of protocols, at Cue-Mate removal; TAI; and 7 days after TAI. Approximately, 28 and 50 days after TAI pregnancy status was determined by ultrasonography. Mean (±SEM) plasma P4 concentration at Cue-Mate removal was greater (p < .01) in CO (6.02 ± 0.2) and JS (6.51 ± 0.2) compared to EB heifers (4.53 ± 0.2). Mean (±SEM) plasma P4 concentration at TAI was lowest in the JS (0.28 ± 0.05), intermediate in CO (0.46 ± 0.02), and greatest in EB heifers (0.66 ± 0.05, p < .01). The diameter of the ovulatory follicle (mean ± SEM) was the smallest in the JS group compared to that in the CO and EB groups (15.8 ± 0.5; 13.9 ± 0.5; and 12.7 ± 0.5 mm for EB, CO and JS, respectively). More (p < .01) heifers in the JS group had their oestrous cycle synchronized (50.0, 78.8 and 82.4% for EB, CO and JS groups), and were pregnant at 28 (40.3, 51.3 and 63.3% for EB, CO and JS groups) and 50 days after TAI (32.6, 46.0 and 60.0% for EB, CO and JS groups). In summary, heifers subjected to the J-Synch TAI protocol had lower P4 at TAI, and better overall response to hormonal treatments, which resulted in increased P/AI at 28 and 50 days after TAI compared to those heifers subjected to either a 7-day EB protocol or a 5-day CO-synch protocol.

Treatment alternatives to induce follicular wave emergence for timed-AI in lactating dairy Cows

Two experiments evaluated the effect of different hormonal treatments to synchronize follicle wave emergence on follicle dynamics and pregnancies per AI (P/AI) in estradiol (E2)/progesterone (P4) timed-AI (TAI) protocols in lactating dairy cows. In Experiment 1, lactating, primiparous Holstein cows (n = 36) received a P4 releasing device (Day 0) and were allocated at random to one of the following three treatment groups: Group EB received 2 mg E2 benzoate (EB) intramuscularly (i.m.), Group EB + GnRH received 2 mg EB+20 μg buserelin (GnRH) i.m., or Group EB + P4 received 2 mg EB + 100 mg of injectable P4 (iP4) in oil i.m. All cows received 0.150 mg D-Cloprostenol on Days 7 and 8 followed by P4 device removal, 400 IU eCG and 1 mg ECP on Day 8. Daily ultrasound examinations revealed that although the interval from P4 device removal to ovulation was not affected by treatment, cows that received EB + GnRH had an earlier (P < 0.05) emergence of the new follicular wave (Day 2.6 ± 0.2) than the other two treatment groups (Days 3.5 ± 0.3 and 6.1 ± 0.3, for EB and EB + P4, respectively). In Experiment 2, 808 lactating cows were assigned randomly to the three treatments evaluated in Experiment 1, and all the cows were TAI to determine P/AI. Cows in the EB + GnRH group had greater P/AI (57.4 %, P < 0.01) than those in the EB (44.6 %) or EB + P4 (45.7 %) groups. In conclusion, the administration of GnRH, but not iP4, on the day of insertion of a P4 device improves P/AI in lactating dairy cows synchronized for TAI with an estradiol/P4-based protocol.

Early induction of luteolysis in a timed AI protocol increases reproductive performance in beef cows

The aim of this study was to produce a longer proestrus by early administration of prostaglandin F2α (PGF) in a timed artificial insemination (TAI) protocol in non-suckling Bos taurus (Angus crossbreed) beef cows. On day 0, cows (n = 489) were treated with an intravaginal 1 g progesterone (P4) device and 2 mg of estradiol benzoate. On day 7, cows were randomized into two groups: PGF7(n = 244; 500 µg of sodium cloprostenol 24 h before P4 device removal) or PFG8 (n = 245; 500 µg of sodium cloprostenol at P4 device removal). On day 8, P4 device was removed and cows received 0.5 mg of estradiol cypionate. All cows were submitted to TAI on day 10 (48–50 hours after P4 device removal). Cows treated with PGF on day 7 had greater expression of estrus (91.3 vs 79.1 %; P = 0.0011), regardless of CL presence at beginning of the protocol. Cows from PGF7 group had lower circulating P4 concentrations on day 8 in comparison with PGF8 treated cows (1.86 vs 2.99 ng/mL; P < 0.001). However, preovulatory follicle diameter did not differ among treatments at TAI (11.9 vs 11.8 mm; P = 0.7881). Pregnancy per TAI (P/TAI) was greater for PGF7 (63.9 vs 50.6 %; P = 0.0114) than PGF8 treated cows. In cows with follicles <8.5 mm at TAI, expression of estrus (33.3 vs 26.6 %; P = 0.6427) and P/TAI (40 vs 26.6 %; P = 0.3657) were low in both PGF7 and PGF8 treated cows, respectively. In cows with medium follicle size (8.5 to 11.9 mm) PGF7 treated cows had greater expression of estrus (90.5 vs 80 %; P = 0.033) and P/TAI (62.2 vs 49 %; P = 0.053). In cows with follicles >12 mm, expression of estrus was greater for PGF7 than PGF8 treated cows (99.1 vs 93.3 %; P = 0.045), however P/TAI did not differ (68.2 vs 59 %; P = 0.149). In cows with P4 < 1.99 ng/mL on day 8, expression of estrus was similar between PGF7 and PGF8 treated cows (92.6 vs 90.4 %; P = 0.53), and P/TAI tended to be greater for PGF7 than PGF8 treated cows (63 vs 52.1 % P = 0.076). However, in cows with P4 > 2 ng/mL PGF7 cows had higher expression of estrus (89 vs 67.5 %; P = 0.0005) and P/TAI (64.8 vs 48.7 %; P = 0.021) than PGF8. Thus, increasing the proestrous period by inducing luteolysis 24 hours earlier than removing the P4 intravaginal device enhanced fertility in non-suckling cyclic beef cows by increasing expression of estrus and P/TAI.

Evolution over the last 40 years of the assisted reproduction technologies in cattle - the Brazilian perspective I - timed artificial insemination.

The reproductive efficiency of the herd is correlated with higher productivity in livestock. Reproduction biotechniques, such as ovulation synchronization protocols, are important to optimize production and accelerate genetic profit in beef and dairy herds. The objective of this review is to describe the evolution over the last 40 years of the artificial insemination (AI) and the timed-AI (TAI) protocols in cattle from a Brazilian perspective. TAI protocols are based on synchronizing emergence of the wave of follicular growth, controlling circulating progesterone (P4) concentrations, stimulating the final growth of the follicle and inducing a synchronized ovulation. Hormonal alternatives that optimize the response at the end of the protocol and strategies to induce final follicle growth and ovulation in categories of females with low expression of estrus are described. Furthermore, the potential positive effect of previous exposure to injectable P4 on fertility of Bos indicus and Bos taurus cows is also discussed.

319 Single Timed-Ai Heifer Development and Delayed Feedlot Entry of Non-Pregnant Heifers

Abstract To ranch managers, reproduction is the single most important element of profitability, because heifers that calve early with their first calf produce more pounds of beef product and have greater longevity and productivity. Artificial insemination affords ranchers access to elite sires known for above average production potential and replacement heifers bred to elite sires replace themselves with offspring having genomic enhanced genetic potential. This long-term multi-year project is designed to compare control heifers reared in drylot (DLOT) to heifers managed grazing either native range (NR) or a combination of native range and annual forages (field pea-barley, corn, cover crop) grown in a diverse cropping system (ANN), which are bred using a common single Timed-AI protocol (14 d CIDR-PG) and all non-pregnant heifers are finished for grid marketing. As such, following synchronization cleanup bulls are placed with the DLOT control heifers; however, there are no cleanup bulls placed with the grazing treatments. The project objectives were to evaluate reproductive and economic efficiencies among the three systems. Grazing heifer gains during the 121 d grazing period for the DLOT, ANN and NR were 33.7, 119.5, and 126.5 kg, respectively (P = 0.001). Synchronized timed-AI pregnancy rates were 59.4, 43.8, and 62.5% (P = 0.27) for the DLOT, ANN and NR treatments, respectively. Total pregnancy rate was 90.6, 43.8, and 62.5% (P = 0.002) for the DLOT, ANN and NR treatments, respectively. Grazing heifer feedlot performance (ANN vs. NR) did not differ for start weight (452 vs 456 kg, P = 0.29), end weight (610.0 vs 600.0 kg, P = 0.74), gain (157 vs 164 kg, P = 0.69), ADG (1.42 vs 1.48 kg, P = 0.70), daily DM feed intake (15.0 vs 14.7 kg, P = 0.73), G:F (0.04298 vs 0.04554 kg, P = 0.42), daily feed cost ($4.38 vs $4.30, P = 0.73), feed cost/kg gain ($3.11 vs $2.95, P = 0.51), and feed and yardage cost/kg gain ($3.42 vs $3.24, P = 0.55). Grazing heifer carcass measurements did not differ for, HCW (369 vs 365 kg, P = 0.83), Dressing Percent (60.7 vs 61.0, P = 0.69), marbling score (524 vs 531, P = 0.78), and percent Choice (100% vs 100%). Gross pregnant heifer and gross carcass return for DLOT, ANN and NR was $1,325, $1,702, and $1,601, respectively. These data indicate that grazing systems combining bred heifer value and grid-based carcass value are competitive.

Ovarian activity and reproductive responses of lactating Angus cows due to a mineral supplementation throughout a timed AI protocol.

Two experiments were conducted to evaluate the effect of intramuscular administration of minerals during a TAI program on the reproductive responses of lactating Angus cows. All cows (n=353) were subjected to a 9-day TAI program based on CIDR insertion plus injections of estradiol, cloprostenol, and eCG, and then TAI 48 h later. In experiment 1, two groups were randomly created, one control with a placebo injection (CON, n=109), and the second received 10 mL of Fosfosan® (MIN, n=172) on day 0 of the synchronization. Conception rate (66.9 vs. 55%) and estrus percentage (55.8 vs. 44%) were higher (P≤0.05) in MIN than in CON cows. Given these results, a second experiment was conducted randomly assigning the cows to two treatments (n=36 each): a single injection of 10 mL of Fosfosan® (MIN-O) on day 0 or two injections of 10 mL of Fosfosan® (MIN-T) on synchronization days 0 and 7. Four cows of each treatment were randomly selected to be scanned with transrectal ultrasound before and during the synchronization protocol to assess ovarian structures and cyclicity, and at day 39 post-TAI for pregnancy diagnosis. Also, blood samples were obtained for the determination of serum minerals and progesterone (P4) concentrations. The number of mineral injections did not affect conception rate (P≥0.1229) conception rate, serum mineral and P4 concentrations, number, and size of emerging follicles, or follicle size according to 1 to 4 classifications. The MIN-T promoted (P<0.05) earlier follicular wave emergence than MIN-O. However, MIN-O cows had a dominant follicle of 15.12 mm, which is more significant (P<0.05) than that in MIN-T cows (13.5 mm). In conclusion, providing a single mineral injection of Fosfosan® at the start of a TAI program is an excellent reproductive strategy in lactating Angus cows to improve the dominant follicle growth, estrus response, and conception rate.

Effect of an additional GnRH 2 d after the initiation of the Resynch-25 program on pregnancy per artificial insemination in lactating dairy cows

Timed-AI protocols for the reinsemination of nonpregnant cows significantly reduce the interval between inseminations (AI) in lactating dairy cows. One of the most used programs is the Resynch-25, which starts Ovsynch on d 25 after previous AI in all cows, and only nonpregnant cows continue with the pro­gram on d 32 after previous AI. Low ovulatory response to d 25 GnRH administration can compromise the proportion of cows synchronized to the program and pregnancy per AI (P/AI) after timed-AI. One of the factors that can affect ovulatory response to this d 25 GnRH is the stage of antral follicle development at the time of treatment. For instance, non-dominant follicles can­not ovulate due to a lack of LH receptors in the granulosa cells. Thus, we hypothesized that adding an extra GnRH 2 d after d25 GnRH would increase P/AI to the Resynch-25 program. Our ob­jective was to determine the effect of an additional GnRH 2 d after initiating the Resynch-25 program on P/AI.

Performing AI 55 or 65h after progesterone device removal did not differ in a 7-d progesterone-based protocol for timed-AI in Nellore suckled cows.

This study aimed to evaluate the reproductive performance of Nellore suckled cows inseminated 55 (n = 304) or 65 (n = 296) h after progesterone (P4) removal in a 7-d protocol. The protocol consisted of the insertion of a device with 2g of P4 and 2mg of estradiol benzoate on d 0, with the device remaining in the cows for 7 d. Cows in the 55-h treatment had the P4 device removed in the morning, while cows in the 65-h treatment had the P4 device removed in the afternoon. At P4 removal, cows received intramuscularly 300IU of eCG, 0.6mg of estradiol cypionate and 0.52mg cloprostenol sodium. Artificial insemination was performed according to treatments (55 vs. 65h after P4 removal). The results of the study showed that the estrus detection rate (69% vs 65%) and pregnancy per AI (P/AI; 49% vs 49%) did no differ in cows inseminated 55 or 65h after P4 removal, respectively. Furthermore, ovulation rate, the diameter of the largest follicle at the time of AI, and P4 concentration after AI were not affected by treatments. The probability of P/AI was not affected by parity, BCS, age, diameter of largest follicle at AI, days postpartum, BW and time to AI. This study suggests that performing AI from 55 to 65h after the P4 removal in the 7-d-P4 protocol did not affect the reproductive performance in Nellore cows, and opens the possibility for producers to take more time to perform AI of cows in the field without affecting P/AI.

Early versus late body condition score loss in dairy cows: Reproductive performance.

This study aimed to compare milk production and reproductive performance in high yield Holstein cows that lose BCS early and late in the postpartum period. Lactating dairy cows (n = 76) were received first timed AI at 60 to 75 DIM using the farm-managed estradiol-progesterone-GnRH-based timed AI protocol. The BCS of all cows was daily evaluated by automated BCS cameras. Aiming to evaluate the effect of the days in milk (DIM) in which a cow reached the nadir BCS on the reproductive parameters, cows were separated into two groups: early BCS loss (n = 42), cows that reached the nadir BCS ≤ 34 DIM, and late BCS loss (n = 34), cows that reached the nadir BCS > 34 DIM. The optimal cut-off point for determining the relationship between days to nadir BCS and pregnancy by 150 DIM (P150) was calculated using the receiver operating characteristic (ROC) curve. From the ROC analysis, the cut-off was 34 DIM (Se, 80.9%; Sp, 66.7%; AUC, 0.74; P < 0.01). No differences (P>0.05) were detected between groups on the BCS and milk production. The average of milk production in both groups was 46.65 ± 6.15 Kg/day. Cows that reached the nadir BCS early postpartum presented lower (P < 0.01) calving interval and greater (P < 0.01) pregnancy at first AI and P150. In summary, cows that lost BCS early had better reproductive performance and had similar milk yield compared with cows that lost BCS late in the postpartum period.

Effects of early weaning on the reproductive performance of suckled Nelore cows in the subsequent breeding season.

This study aimed to evaluate the effects of early weaning (EW) on body composition, hormone concentrations and metabolites, and reproductive performance of Nelore cows in the subsequent breeding season (BS). Suckled cows that became pregnant by timed-AI (TAI) in the 2020-BS were exposed in 2021 to early weaning at 150 d (27 primiparous [PRI] and 74 multiparous [MUL]) or conventional weaning (CW) at 240 d postpartum (30 PRI and 77 MUL). Body weight (BW) and body condition score (BCS) were determined at 2020-BS, EW, CW, prepartum, and 2021-BS. Blood samples were collected at EW, CW, prepartum (54.75 ± 0.56 d prepartum), and 2021-TAI and assayed for insulin-like growth factor-1 (IGF-I), non-esterified fatty acid (NEFA), and β-hydroxybutyrate (BHB) concentrations. In 2021-BS, cows were exposed to a P4/E2-based protocol for TAI at day 0 (D0), and a second TAI was performed at D22 in females detected with luteolysis (D20) by Doppler ultrasound. The presence of corpus luteum (CL) on D10, estrous expression, and dominant follicle (DF) diameter, and blood perfusion (BP) on D2 and D0 were determined. Data were analyzed by ANOVA or logistic regression of SAS as a 2 × 2 factorial with main factors of parity (PRI or MUL) and weaning strategy (EW or CW). An interaction of parity and weaning strategy was not observed (P > 0.1), but the weight (kg) and BCS were greater (P < 0.05) in MUL cows at the five timepoints, and EW cows were heavier than CW at the moment of CW (541 vs. 493 kg; and 5.3 vs. 4.3), prepartum (551 vs. 506 kg; and 5.2 vs. 4.4) and 2021-BS (475 vs. 450 kg; and 4.5 vs. 3.7). Plasma urea concentration at 2021-BS was greater (P = 0.01) for PRI than for MUL. A parity-by-time interaction was observed (P ≤ 0.05) for concentrations of IGF-I, NEFA, and BHB. PRI cows had greater (P ≤ 0.05) concentrations of IGF-I at EW and greater (P ≤ 0.05) prepartum concentrations of NEFA and BHB than MUL cows. The proportion of cows with CL at D10 was not affected (P > 0.1) by weaning but was greater (P < 0.05) in MUL than in PRI cows (40.4 vs. 15.7%). The diameter of DF and proportion of BP on D0 were greater (P < 0.05) in EW cows than in CW cows. The pregnancy rate (P/AI, %) at the first TAI was greater (P < 0.05) in EW cows (60% vs. 45%), whereas no difference (P > 0.1) was observed at the second TAI. Cumulative P/AI (first and second TAIs) was greater (P < 0.05) in EW cows (81% vs. 63%). In conclusion, weaning at 150 d in Nelore cattle is a strategy to successfully recover the parous cow's body condition and to improve pregnancy success in the next BS, regardless of the cow's parity order.

5d CIDR-Heatsynch improves the circulatory estradiol levels, estrus expression and conception rate in anestrus buffalo (Bubalus bubalis)

The present study aimed to investigate whether increasing estradiol (E2) during preovulatory period would increase estrous expression, luteal profiles and conception rate in 5d CIDR based timed AI protocol. A total 156 anestrus buffalo allocated (78 per group) to either 5d CIDR-Cosynch (d-5: CIDR + GnRH; d0: PGF2α+CIDR removal; 72 h post-CIDR removal: GnRH) or 5d CIDR-Heatsynch (d-5: CIDR + GnRH; d0: PGF2α+CIDR removal; 24 h post-CIDR removal: estradiol benzoate) group. All the buffaloes inseminated at 72 and 84 h post-CIDR removal. A subset of buffalo (n = 58) were subjected to examination of the follicle diameter and luteal profile during protocol, post-AI on days 5 and 12. The buffalo in 5d CIDR-Heatsynch had greater (p < .05) E2 concentrations, estrus induction and increasing trend (p < .08) for conception rate (57.7% vs. 43.6%) than 5d CIDR-Cosynch. The percentage of pregnant buffalo that exhibited estrus signs was greater (p < .01) in 5d CIDR-Heatsynch than 5d CIDR-Cosynch. Positive correlation (p < .01) was observed between POF and E2 concentrations; POF and CL diameter, CL diameter and P4 concentrations. Estrus response and P4 concentrations were indicators of probability of pregnancy. In conclusion, 5d CIDR-Heatsynch tended to improve conception rate. The estrus expression and P4 concentrations (d5 and 12 post-first-AI) is the indicator of probability of pregnancy in buffalo.

180 Effect of treatment with a long-acting cloprostenol sodium formulation in timed AI protocol in beef cattle

Reproduction, Fertility and Development is an international journal publishing original research , review and comment in the fields of reproduction and developmental biology in humans, domestic animals and wildlife

The effect of progesterone length in timed AI in ewes.

This study aimed to evaluate the reproductive performance of ewes submitted to timed AI protocol with 7 (D7) or 9 (D9) days of progesterone. A total of 220 crossbred ewes (Doper × Santa Ines) were distributed in the treatments according to body weight (52.67 ± 11.76kg), body condition score (2.5 ± 0.8; scale of 1-5), and the female category (multiparous, nulliparous and primiparous). Ewes received an intravaginal device of 0.3g of progesterone (CIDR® Easy breed) on day 0, keeping in ewes for 7 or 9days, which were the experimental treatments. At the time of P4 withdrawal, ewes received 300IU of eCG (Novormon®) and 6.70mg of dinoprost tromethamine (Lutalyse®). Insemination by laparoscopy was performed between 46 and 59h after device removal, lasting from 1 to 5min/ewe, which did not differ between protocols. The estrus detection rate was higher in the 9-day protocol compared to the 7-day protocol (82% and 65%, respectively, P = 0.0096). However, the 7-day protocol tended to increase pregnancy rate on the TAI compared to the 9-day protocol (45% and 33%, respectively, P = 0.09). The plasma concentration of progesterone at device removal was higher in the 7-day protocol than in the 9-day protocol (2.35 and 1.22ng/mL, respectively, P = 0.04). We conclude that reducing the length of the estrus synchronization protocol to 7days is recommended, which improved the reproductive response in ewes.

Effect of nerve growth factor-β administered at insemination for lactating Holstein dairy cows bred after timed-artificial insemination protocol

The objectives of this study were to determine the effects of nerve growth factor-β (NGF), purified from bulls' seminal plasma and administered at the time of artificial insemination (AI), on progesterone post-AI, interferon-stimulated genes (ISG), and pregnancy per AI (P/AI) for lactating Holstein dairy cows enrolled in a timed-AI protocol. We hypothesized that administration of NGF at the time of AI would increase plasma progesterone post-AI, upregulate relative abundance of ISG, and improve P/AI in lactating dairy cows. Holstein cows (n = 557) from a single commercial dairy farm were blocked by parity and randomly assigned to receive an intramuscular injection containing 296 µg of bovine purified NGF at the time of AI, diluted in 2 mL of phosphate-buffered saline (NGF: n = 275), or receive only the 2 mL of phosphate-buffered saline (control: n = 282). Plasma progesterone and corpus luteum size were assessed in a subset of cows (NGF: n = 32; control: n = 36) at d 7, 14, and 19 post-AI. Relative mRNA abundance of ISG (ISG15, MX1, MX2, and RTP4) was assessed in peripheral blood leukocytes on d 19 post-AI. Pregnancy diagnosis was performed at 37 and 65 d post-AI. There was an interaction effect between treatment and parity for plasma progesterone; however, plasma progesterone and ISG did not differ between treatments. There were no effects of NGF for P/AI at 37 d post-AI (NGF = 40.0% vs. control = 41.6%), 65 d post-AI (NGF = 36.0% vs. control = 38.1%), and for pregnancy loss (NGF = 8.4% vs. control = 7.7%). The current study revealed that effects to NGF in lactating Holstein cows were minor and contingent with parity for progesterone, and no improvement in ISG relative abundance and P/AI were observed.

Effect of the addition of GnRH and a second prostaglandin F2α treatment on pregnancy per artificial insemination in lactating dairy cows submitted to an estradiol/progesterone-based timed-AI protocol

Two experiments determined whether the addition of GnRH at the beginning of an estradiol (E2)/progesterone (P4)- based synchronization protocol and/or a second dose of prostaglandin F2α (PGF2α) the day before P4 device removal improves pregnancy rate in lactating dairy cows. On Day 0, all cows received a CIDR-B device and 2 mg i.m. estradiol benzoate, and half received 200 μg i.m. gonadorelin acetate (GnRH). On Day 7, cows were further subdivided to receive PGF2α (500 μg i.m. cloprostenol) or no PGF2α treatment. On Day 8, CIDR-B were removed, and all cows received PGF2α, 1 mg estradiol cypionate and 400 IU eCG i.m., and an estrus detection aid. Experiment 1 was designed to evaluate the effect of treatments on follicular development from P4 device removal to ovulation, expression of estrus, time of ovulation and serum P4 concentrations. Cows (n = 76) were examined by ultrasonography and bled for serum P4 determinations every 12 h from the time of P4 device removal but were not inseminated. In Experiment 2, all cows (n = 1036) were inseminated based on estrus detection using tail-paint. Cows with >50% of the paint rubbed-off by 48 h after P4 device removal were inseminated at that time, whereas those not in estrus received 100 μg i.m. of GnRH and were inseminated 12 h later. In Experiment 1, the interval from P4 device removal to ovulation was 71.7 ± 1.5 h and did not differ among groups. However, cows that received 2 injections of PGF2α had a greater (P < 0.01) estrus rate and lower (P < 0.01) P4 concentrations at 48 h after P4 device removal than those that received 1 PGF2α (estrus rate: 86.8% vs 68.4% and P4 concentration: 0.12 ± 0.01 vs 0.36 ± 0.07, for 2 and 1 PGF2α, respectively). In Experiment 2, estrus rate was also influenced by the number of PGF2α treatments, regardless of whether cows received or did not receive GnRH on Day 0 (2 PGF2α: 84.7%, 438/517 vs 1 PGF2α: 65.7%, 341/519; P < 0.01). Furthermore, there was a GnRH treatment by number of PGF2α treatments interaction (P < 0.05) on P/AI that was attributed to greater (P < 0.05) P/AI in cows that received GnRH on Day 0 and 2 PGF2α than in the other three treatment groups (EB+1 PGF2α: 45.2%, 119/263; EB+2 PGF2α: 45.8%, 119/260; EB + GnRH + 1 PGF2α: 45.7%, 117/256 and EB + GnRH + 2 PGF2α: 57.2%, 147/257). It was concluded that the addition of GnRH on Day 0 and a second dose of PGF2α the day before P4 device removal improves P/AI in lactating dairy cows synchronized with an estradiol/P4-based protocol.

Postponing TAI in beef cows with small preovulatory follicles

The aims of this study were (1) to establish an optimal cut-off point for evaluating the effect of the preovulatory follicle (POF) diameter in timed AI (TAI) programs, and (2) to evaluate the effect of postponing TAI in cows with smaller follicles on pregnancy per AI (P/AI). In Study 1, Nelore cows (n = 426) were subjected to an estradiol-progesterone (P4) based TAI protocol. The diameter of POF was measured at TAI, 48 h after P4 insert removal. From the ROC curves for determining the relationship between the POF diameter and pregnancy, the cut-off was 11 mm (P < 0.001). Cows with larger POF had greater (P < 0.05) P/AI (62.5%) than cows with smaller POF (34.8%). In Study 2, Nelore cows (n = 1257) were subjected to the same TAI protocol as in Study 1. Before TAI, cows were separated according to POF diameter in three groups: (1) Larger POF (LP, n = 873; POF ≥11 mm), (2) Smaller POF 0 h (SP0, n = 195; POF <11 mm), and (3) Smaller POF 24 h (SP24, n = 189; POF <11 mm). Cows in the LP and SP0 were TAI at 48 h and cows in the SP24 group were TAI at 72 h after P4 insert removal. Cows in the LP group had the greatest (P < 0.05) P/AI (60.25%), followed by cows in the SP24 group (41.8%), while cows in the SP0 group had the lowest P/AI (31.8%). In conclusion, cows with smaller follicles have lower P/AI, but postponing the TAI by 24 h in these cows increases P/AI.