scholarly journals Reproductive performance of Nellore heifers raised in extensive system undergoing different vaccination protocols in fixed-time artificial insemination (FTAI)

2019 ◽  
Vol 49 (11) ◽  
Author(s):  
Ernest Schillings Neto ◽  
Eriklis Nogueira ◽  
Rodrigo Jardim ◽  
Urbano Gomes Pinto de Abreu ◽  
Fabiana Andrade de Melo Sterza ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Reproductive Performance ◽  
Artificial Insemination ◽  
Body Condition Score ◽  
Natural Infection ◽  
Fixed Time ◽  
Occurrence Rate ◽  
Fetal Mortality ◽  
Diarrhea Virus ◽  
Vaccination Protocol

ABSTRACT: This study evaluated the reproductive performance of Nellore heifers without previous vaccination undergoing fixed-time artificial insemination (FTAI) and subsequent natural breeding under different vaccination protocols against infectious bovine herpesvirus 1 (BHV-1), bovine viral diarrhea virus (BVDV), and bovine leptospirosis (BL). A total of 763 animals were included; the group assignment was as follows: T1, control without vaccination; T2, vaccination against BL; T3, vaccination against BHV-1and BVDV; T4,vaccination against combination of BL + BHV-1and BVDV. Vaccination was started 30 days before FTAI (D-40), and a booster dose was administered at D-10. Serological tests were used to verify the occurrence rate of natural infection by BL, BHV-1, and BVDV. Initial pregnancy was diagnosed at D30, D60, and D120 after FTAI. Final pregnancy rates were evaluated by group, weight, body-condition score, occurrence of estrus, inseminator, bull, and occurrence of abortions or embryonic death. In all groups, results indicated seropositivity of 100% for leptospirosis, 77.0-94.0% for BHV-1, and 64.0-87.0% for BVDV. The vaccination protocol was not a significant influencing factor of pregnancy rate and embryonic or fetal mortality; whereas, animal weight at the beginning of the breeding season and presence of estrus at FTAI were significant influencing factors of pregnancy rate. The vaccination protocol had no interference with the reproductive performance of the experimental groups.

scholarly journals Comparison of the effects of Presynch-Ovsynch, Presynch- Ovsynch+CIDR, and G6G protocols on the reproductive performance of lactating Holstein cows in the postpartum period

2021 ◽  
Vol 53 (4) ◽  
Author(s):  
Hesam Kohsari ◽  
Khatereh Berenjian
Keyword(s):  
Serum Concentration ◽  
Pregnancy Rate ◽  
Reproductive Performance ◽  
Body Condition Score ◽  
Dairy Farm ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Holstein Cows ◽  
Treatment Protocols ◽  
Ovulatory Follicle

This study was performed on an industrial dairy farm near Tehran province, Iran, on 666 lactating Holstein cows from September 2019 to June 2020 in order to eliminate the harmful effects of heat stress on the reproductive performance of the cows. The hypothesis of the recent study was that by increasing the serum concentration of progesterone (P4) in the luteal phase before insemination in the form of Presynch-Ovsynch+CIDR (POC) and G6G protocols, the pregnancy rate of cows would be increased compared to the Presynch-Ovsynch (PO) protocol. The aim of the present study was to evaluate the effects of Presynch-Ovsynch (PGF2α-14d- PGF2α-12d-Ovsynch (OVS: GnRH(GnRH1)- 7d-PGF2α(PG)-2d-GnRH)-18h-Fixed-time artificial insemination (FTAI), n=212), Presynch-Ovsynch+CIDR (similar to the PO protocol, plus the use of a CIDR for 7 days, from the start of the OVS+FTAI protocol to the time of PG injection, n=230), and G6G (PGF2α- 2d-GnRH-6d-OVS+FTAI, n=224) protocols on the reproductive performance and pregnancy rate of lactating Holstein cows. The average body condition score (BCS) for the cows was about 2.5 at the time of the onset of the OVS+FTAI program. The average daily milk production for cows at the time of the start of the OVS+FTAI program was 38.3 kg/day. On average, the studied cows were inseminated 86 days postpartum. Implementation of the G6G protocol in comparison to the PO and POC protocols increased the serum concentration of P4 at GnRH1 (P=0.04). The cows that received the G6G protocol had a greater number of corpuses luteum (CL) on their ovaries at PG in comparison to the cows in the PO and POC protocols (P=0.03 and P=0.05, respectively). For all treatment protocols, the pregnancy rate of cows with >2 CLs on their ovaries at PG was significantly higher than for cows with ≤2 CLs on their ovaries at this time. The overall pregnancy rate for all cows studied was 42%. Separately, pregnancy rates for cows in PO, POC, and G6G protocols were calculated at 36.7%, 41.7%, and 47.3% respectively. The highest and the lowest pregnancy rates were obtained in the G6G and PO protocols, respectively (P=0.03). It can be concluded that the G6G protocol increased the pregnancy rate of cows in comparison to the PO but not to the POC protocol. This result can be attributed to the increase in serum concentration of P4 at GnRH1 and the greater number of CLs at PG following implementation of the G6G compared to the PO protocol. Although CIDR administration in the POC protocol led to an increase in the pregnancy rate of cows compared to the PO protocol, possibly by increasing the synchrony rate and the quality of the ovulatory follicle, this increase was not statistically significant (P=0.09).

scholarly journals AVALIAÇÃO DO DESEMPENHO REPRODUTIVO DE VACAS NA REGIÃO DO PANTANAL SUL-MATO-GROSSENSE SUBMETIDAS A IATF Com Aplicação De GnRH

Nativa ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 281-285
Author(s):  
Gabriel Rodrigo Hass Perucchi ◽  
Gabriela de Souza Sartori ◽  
Richarlla Aparecida Buscariol Silva ◽  
Murilo da Silva Garcia ◽  
Rodrigo José Delgado Jardim ◽  
...  
Keyword(s):  
Beef Cattle ◽  
Pregnancy Rate ◽  
Reproductive Performance ◽  
Artificial Insemination ◽  
Body Condition Score ◽  
The Body ◽  
Mato Grosso ◽  
Condition Score ◽  
Timed Artificial Insemination ◽  
Mato Grosso Do Sul

A Inseminação artificial em tempo fixo (IATF) está se difundindo no Brasil, pois contribui para o aumento da produtividade. O objetivo neste trabalho foi avaliar o uso do GnRH em protocolos de IATF de vacas criadas no pantanal Sul-mato-grossense. Participaram da pesquisa 531 vacas paridas da raça Nelore, que foram avaliadas de acordo com o escore de condição corporal (ECC), submetidas a três tipos de protocolos de IATF (lote 1, 2 e 3). Após 40 dias da inseminação artificial foi realizado diagnóstico de gestação. As matrizes que não receberam GnRH no lote 1 (estro aparente), lote 2 (estro parcial) e lote 3 (sem apresentação de estro) apresentaram, respectivamente 55,4%, 19,2% e 25,9% de prenhez, enquanto as que receberam o fármaco apresentaram 48,6%, 37,2% e 38,8%. Relacionado ao ECC, pode-se observar que a maior taxa de prenhez ocorreu em animais com ECC 3. Primíparas apresentaram melhor taxa de prenhez quando receberam GnRH independente do ECC. Concluiu-se que o uso de GnRH mostrou-se eficiente para melhoria da taxa de prenhez principalmente em primíparas, assim como nos animais que não apresentaram estro ou apresentaram estro parcial, e que matrizes com ECC 3 apresentaram melhores taxas de prenhez que vacas com escore inferior. Palavras-chave: bovino de corte; inseminação artificial em tempo fixo; produtividade; GnRH; Nelore.   Evaluation of cow reproductive performance in the region of Mato Grosso do Sul swamp submitted to TAI with GnRH application   ABSTRACT: The technique of timed artificial insemination (TAI) is spreading in Brazil, as it contributes to the increase of productivity. The objective of this work was to evaluate the use of GnRH in TAI protocols of cows raised in the swamp of Mato Grosso do Sul. 531 Nelore breed calved cows participate in the survey, which were evaluated according to the body condition score (BCS), and then performed three types of TAI protocols (batch 1, 2 and 3). After 40 days of the insemination, a pregnancy diagnosis was made. The matrices that did not receive GnRH in batch 1 (apparent oestrus), batch 2 (partial oestrus) and batch 3 (no oestrus presentation) presented respectively 55.4%, 19.2% and 25.9% of pregnancy, while those receiving the drug showed 48.6%, 37.2% and 38.8%. Related to BCS, it can be observed that the highest pregnancy rate occurred in animals with BCS 3. Primiparous had a better pregnancy rate when receiving GnRH regardless of BCS. It was concluded that the use of GnRH was efficient to improve the pregnancy rate mainly in primiparous as well as animals that showed no oestrus or partial oestrus, and matrices with BCS 3 had better pregnancy rates than cows with lower scores. Keywords: beef cattle; timed artificial insemination; productivity; GnRH; Nelore.

scholarly journals Evaluation of Ovsynch Protocol on Reproductive Performance of Anestrous Buffaloes during Breeding Season in Chitwan, Nepal

2017 ◽  
Vol 34 ◽  
pp. 41-50
Author(s):  
C.N. Kharel ◽  
B. Devkota ◽  
S.K. Sah ◽  
R.K. Karki
Keyword(s):  
Pregnancy Rate ◽  
Reproductive Performance ◽  
Body Condition Score ◽  
Fixed Time ◽  
Breeding Technique ◽  
Management Condition ◽  
Internal Genitalia ◽  
Condition Score ◽  
Deposition Intensity ◽  
Ovarian Cyclicity

This study evaluated the effectiveness of Ovsynch/FTAI protocol (day 0 fertirelin inj. 100μg I/M, day 7 cloprostenol inj. 500μg I/M, day 9 fertirelin inj. 100μg I/M, and day 10 fixed time artificial insemination 18 hours after second injection of fertirelin) in anestrous buffaloes of Chitwan, Nepal (n=14). Protocol was evaluated in terms of estrus characteristics, ovulation and pregnancy rate. Responses were analyzed by grouping the buffaloes based on type of anestrus, length of anestrus, body condition score (BCS), milking status, parity, age, management condition, follicle count on day of second GnRH treatment and site of semen deposition. Intensity of estrus characteristics on day of AI was mild. Major estrus signs observed were uterine tonicity, alertness, mucus discharge on rectal manipulation of internal genitalia, swelling of vulva and teat engorgement. Mucus discharge on rectal manipulation of internal genitalia and teat engorgement were clearly noticed in 50 % buffaloes. There was higher tendency (P=0.08) of estrus expression by buffalos with anestrous period of 10 months or lower compared to those with anestrous period longer than 10 months. Overall ovulation rate was 85.7%. Pregnancy rate to FTAI was 28.6% (22.2% and 40% in true anestrous and silent estrus buffaloes). 64.3% (66.7% and 60% of true anestrous and silent estrus) buffaloes were pregnant when checked at 102 days of FTAI including subsequent breeding. Although Ovsynch/FTAI seems to be alternative breeding technique in silent estrus buffaloes, further study with increased sample size is recommended. This protocol can potentially be used for resumption of ovarian cyclicity in true anestrus buffaloes.

scholarly journals The use of insulin to improve fertility of timed-inseminated postpartum suckled beef cows

2010 ◽  
Vol 45 (10) ◽  
pp. 1219-1221 ◽  
Author(s):  
Augusto Schneider ◽  
Luiz Francisco Machado Pfeifer ◽  
Eduardo Schmitt ◽  
Ivan Bianchi ◽  
Marcelo Brandi Vieira ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Body Condition ◽  
Chorionic Gonadotropin ◽  
Artificial Insemination ◽  
Body Condition Score ◽  
Insulin Injection ◽  
Fixed Time ◽  
Beef Cows ◽  
Condition Score ◽  
Equine Chorionic Gonadotropin

The objective of this work was to evaluate the effect of insulin alone or in association with equine chorionic gonadotropin (eCG) on the fertility of postpartum beef cows subjected to synchronization. A total of 340 cows was subjected to fixed time artificial insemination. In the trial 1, the cows were subjected to temporary weaning (TW), while in the trial 2 the same protocol was tested without TW. The addition of an insulin injection to a progesterone/eCG-based protocol without TW increased the pregnancy rate of beef cows with body condition score (BCS) equal to or lower than 2.5. Insulin had no effect on cows submitted to TW or with BCS equal to or higher than 3.0.

scholarly journals Impact of vaccination on the reproductive performance of multiparous Nellore cows

2018 ◽  
Vol 38 (3) ◽  
pp. 456-461 ◽  
Author(s):  
Luiz C.L. Ferreira ◽  
Henrique J. Fernandes ◽  
Aline G. Silva ◽  
Carlos E. Fernandes ◽  
Iveraldo S. Dutra ◽  
...  
Keyword(s):  
Reproductive Performance ◽  
Artificial Insemination ◽  
Pregnancy Loss ◽  
Serum Antibody ◽  
Fixed Time ◽  
Beef Cows ◽  
Mato Grosso ◽  
Diarrhea Virus ◽  
Significant Difference ◽  
The Impact

ABSTRACT: Two experiments were conducted to evaluate the impact of two vaccines on the reproductive performance of multiparous beef cows in Mato Grosso do Sul, Midwest Brazil. In Experiment 1,765 calved multiparous Nellore cows were subjected to the same fixed-time artificial insemination (FTAI) protocol and rebred. Ultrasound pregnancy diagnosis was performed 30 and 90 days post-FTAI (DPI). Rates of pregnancy and pregnancy loss were determined for three periods: from 30 to 90 DPI, from 30 DPI to calving, and from 90 DPI to calving. The cows were assigned to three groups with different vaccination protocols - namely, Group VACMULT (n=250): vaccine against bovine herpesvirus 1 (BoHV-1), bovine viral diarrhea virus (BVDV), and leptospirosis; Group VACL (n=245): vaccine against leptospirosis alone; Group NOVAC (n=270): no vaccination. Serum antibody titers for BoHV-1, BVDV, and leptospirosis, measured in 57 cows from each group indicated active infection, suggesting circulation of these pathogens in the herd. No differences in pregnancy rates were observed across groups. Pregnancy loss rates did not differ significantly across groups within any of the periods investigated (30 to 90 DPI, 30 DPI to calving, or 90 DPI to calving). In Experiment 2, two vaccination protocols for each vaccine were investigated. Group VACGEST was vaccinated on day zero of FTAI (D0) and again 30 days post-FTAI (30 DPI). Group VACPREV was vaccinated on D0 and again on the day of insemination (D11). No significant difference was observed between groups, or significant gestational loss in the group that received the second vaccine on the day of insemination. The results revealed that neither vaccine interfered with the reproductive performance of multiparous cows. No differences were observed between vaccination carried out on both D0 and D11 and that performed on both D0 and D30. The performance of the IBR/BVDV/Leptospirosis vaccine on the day of the artificial insemination did not cause adverse effects on the reproductive parameters.

scholarly journals The effect of clitoral stimulation post artificial insemination on pregnancy rates of multiparous Bos indicus beef cows submitted to estradiol/progesterone-based estrus synchronization protocol

2020 ◽  
Vol 98 (7) ◽  
Author(s):  
Ramiro V Oliveira Filho ◽  
Reinaldo F Cooke ◽  
Gustavo A de Mello ◽  
Victor M Pereira ◽  
Jose Luiz M Vasconcelos ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Artificial Insemination ◽  
Body Condition Score ◽  
Bos Indicus ◽  
Fixed Time ◽  
Beef Cows ◽  
Pregnancy Rates ◽  
Estrus Synchronization ◽  
Exit Velocity ◽  
Clitoral Stimulation

Abstract Clitoral stimulation after artificial insemination (AI) in beef cattle is a common practice utilized by AI technicians; however, the effect of clitoral stimulation during fixed-time AI (TAI) is still unknown. The objective of the present experiment was to evaluate the effect of clitoral stimulation on temperament responses and pregnancy rates to TAI in Bos indicus beef cows. A total of 1,186 multiparous Nellore cows across three different locations were assigned to an estradiol/progesterone-based estrus synchronization + TAI protocol (day −11 to 0). Cows were randomly assigned to receive either 3 s of clitoral stimulation (n = 602) or no clitoral stimulation (n = 584) immediately after TAI (day 0). Cow body condition score (BCS) was recorded on day −11. Estrus expression was evaluated based on estrus detection visual aid patch activation on day 0 (estrus, ≥50% activated; no estrus, <50% activated). Temperament was assessed by individual chute score based on a 5-point scale before TAI, and individual exit velocity was measured after clitoral stimulation. Pregnancy diagnosis was performed 30 d after TAI via transrectal ultrasonography. Pregnancy rate to TAI was positively affected by BCS (P < 0.01) and estrus expression (P = 0.03). Pregnancy rates of cows receiving clitoral stimulation did not differ (P = 0.39) from cows non-stimulated (47.5 ± 4.6% vs. 44.3 ± 4.6%, respectively). No interaction of clitoral stimulation and estrus expression was observed (P = 0.26). Chute score was positively correlated to exit velocity (P < 0.01; r = 0.29); however, clitoral stimulation did not affect exit velocity (P = 0.86). In summary, pregnancy rates to TAI are influenced by various factors and multiple strategies have the potential to increase the fertility of beef cows submitted to TAI; however, clitoral stimulation of Bos indicus beef cows did not improve TAI pregnancy rate.

scholarly journals Influence of nutritional and ovarian parameters on pregnancy rates of Nelore cows artificially inseminated at fixed time

2020 ◽  
Vol 9 (9) ◽  
pp. e907998091
Author(s):  
Maria Paula Marinho de Negreiros ◽  
Guilherme Henrique de Freitas Seugling ◽  
Ana Beatriz Marques de Almeida ◽  
Myrian Megumy Tsunokawa Hidalgo ◽  
Maria Isabel Mello Martins ◽  
...  
Keyword(s):  
Weight Gain ◽  
Pregnancy Rate ◽  
Artificial Insemination ◽  
Body Condition Score ◽  
Transrectal Ultrasound ◽  
Fixed Time ◽  
The Body ◽  
Antral Follicles ◽  
Pregnancy Diagnosis ◽  
Condition Score

This experiment aimed to evaluate the effect of weight gain, body condition score and antral follicle count on the fertility of cows subjected to fixed-time artificial insemination. To this study, it was used 194 Nelore, pluriparous cows, between the 30th and the 45th day of the postpartum period. The cows were weighed, was classified by the body condition score and a transrectal ultrasound was performed in the ovaries to identify the corpus luteum and for counting the antral follicles. Then, the females were submitted to a hormonal protocol to perform the artificial insemination in fixed time. Thirty days after the artificial insemination, the cows were weighed again and the pregnancy was diagnosed by transrectal ultrasound. The pregnancy rate did not interact (P>0.05) with the body score condition, nor the presence of the corpus luteum, neither with the antral follicles count. The weight gain between the artificial insemination moment and the pregnancy diagnosis showed an interaction (P = 0.02) with the pregnancy rate. The weight gain average between the FTAI and the pregnancy diagnosis was 9.0 kg. The animals that gained up to 73 kg, showed higher pregnancy rate. In conclusion, the weight gain between the artificial insemination in fixed time and the pregnancy diagnosis influenced the pregnancy rate.

scholarly journals Effects on Synchronization and Reproductive Efficiency of Delaying the Removal of the Intravaginal Progesterone Device by 24 h in the 5d Co-synch Protocol in Heifers

Animals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 849
Author(s):  
Aitor Fernandez-Novo ◽  
Sergio Santos-Lopez ◽  
Jose Luis Pesantez-Pacheco ◽  
Natividad Pérez-Villalobos ◽  
Ana Heras-Molina ◽  
...  
Keyword(s):  
Animal Welfare ◽  
Reproductive Performance ◽  
Artificial Insemination ◽  
Fixed Time ◽  
Reproductive Efficiency ◽  
Beef Heifers ◽  
Animal Management ◽  
Commercial Farms ◽  
Beef Herds ◽  
Farm Economics

In beef herds, increasing animal welfare, improving reproductive performance and easing animal management are key goals in farm economics. We explored whether delaying the removal of the intravaginal progesterone device by 24 h in heifers synchronized with a 5d Co-synch 72-h protocol could improve reproductive efficiency of fixed-time artificial insemination (FTAI). In experiment 1, we examined the total synchronization rate (TSR) in cycling Holstein heifers. Heifers (13.4 ± 0.69 mo.) were randomly assigned to the standard 5d Co-synch 56-h protocol (5dCo56; n = 10), 5d Co-synch 72-h (5dCo72; n = 17), or the modified 5d Co-synch 72-h protocol, in which removal of the progesterone device was delayed by 24 h (6dCo48; n = 19). In experiment 2, 309 cycling beef heifers on 18 commercial farms were subjected to the 5d Co-synch 72-h or 6-d Co-synch 48-h protocol and conception rate (CR) studied. In experiment 1, the three protocols led no differences on TSRs of 80.0% (5dCo56), 88.2% (5dCo72), and 89.5% (6dCo48). In experiment 2, the CR from the beef heifers, observed during two consecutive reproductive seasons did not differ: 59.7% for 5dCo72 and 62.0% for 6dCo48 (p = 0.907). Therefore, delaying removal by 24 h provides satisfactory results without reducing reproductive efficiency of heifers.

scholarly journals Luteogenesis and Embryo Implantation Are Enhanced by Exogenous hCG in Goats Subjected to an Out-of-Season Fixed-Time Artificial Insemination Protocol

Biology ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 429
Author(s):  
Jorge A. Bustamante-Andrade ◽  
César A. Meza-Herrera ◽  
Rafael Rodríguez-Martínez ◽  
Zurisaday Santos-Jimenez ◽  
Oscar Ángel-García ◽  
...  
Keyword(s):  
Corpus Luteum ◽  
Artificial Insemination ◽  
Body Condition Score ◽  
Embryo Implantation ◽  
Implantation Rate ◽  
Fixed Time ◽  
Efficiency Index ◽  
Control Group ◽  
Condition Score ◽  
Interesting Approach

The aim of this study was to evaluate the possible effect of two doses of hCG (100 and 300 IU) applied at two different times (7 and 14 d) after a fixed-time artificial insemination protocol (FTAI) upon some variables involved in the embryonic implantation rate in goats during the natural deep anestrous season (April, 25° north). The experimental units considered crossbred, multiparous, anovulatory goats (n = 69, Alpine, Saanen, Nubian x Criollo), with average body weight (43.6 ± 5.7 kg) and body condition score (1.86 ± 0.28 units) located in northern–semiarid Mexico (25° N, 103° W). Once the goat’s anestrus status was confirmed, goats were subjected to an estrus induction protocol. Upon estrus induction confirmation, goats (n = 61) were subjected to a FTAI procedure. Immediately after the FTAI, the goats were randomly distributed to five experimental groups: (1). G100-7 (n = 13) 100 IU, hCG 7 d post-FTAI, (2). G100-14 (n = 12) 100 IU hCG, 14 d post-FTAI, (3). G300-7 (n = 12) 300 IU, hCG, 7 d post-FTAI, (4). G300-14 (n = 12) 300 IU hCG 14 d post-FTAI, and (5). Control group, CONT (n = 12) 0.5 mL saline, 7 and 14 d post-FTAI. The response variables conception rate (39.36 ± 0.23), fertility rate (27.96%), prolificacy rate (1.1 ± 0.29 kids), ovulation rate (0.74 ± 0.20 corpus luteum) corpus luteum diameter (10.15 ± 0.59 mm), embryo number (1.58 ± 0.20), and embryo implantation rate (48.96%), did not differ between treatments. However, while the variables fecundity rate (67%), embryo efficiency index-1 (33.99 ± 0.20%), and embryo efficiency index-2 (27.94 ± 0.30%) were favored by the G300-14 treatment, the corpus luteum area was favored (p < 0.05) by both G300-7 (113.30 ± 0.19 mm2) and G300-14 (103.04 ± 0.17 mm2). Such reproductive strategy emerges as an interesting approach, not only to enhance the out-of-season reproductive outcomes, but also to boost one of the main rulers defining the global reproductive efficiency of a heard, namely, the embryo implantation efficiency.

Efficiency of mating, artificial insemination or resynchronisation at different times after first timed artificial insemination in postpartum Nellore cows to produce crossbred calves

2019 ◽  
Vol 59 (2) ◽  
pp. 225 ◽  
Author(s):  
Walvonvitis Baes Rodrigues ◽  
Jean do Prado Jara ◽  
Juliana Correa Borges ◽  
Luiz Orcirio Fialho de Oliveira ◽  
Urbano Pinto Gomes de Abreu ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Breeding Season ◽  
Chorionic Gonadotropin ◽  
Artificial Insemination ◽  
Fixed Time ◽  
Beef Cows ◽  
Device Removal ◽  
Oestradiol Benzoate ◽  
Timed Artificial Insemination ◽  
Equine Chorionic Gonadotropin

The objective of this trial was to evaluate different post-timed artificial insemination (TAI) reproductive managements in postpartum beef cows to produce crossbred calves from artificial insemination (AI). Nellore cows (n = 607), with 45 days postpartum, were inseminated at a fixed time, using a protocol that included an intravaginal progesterone-releasing device along with oestradiol benzoate, prostaglandin, equine chorionic gonadotropin, and oestradiol cypionate, followed TAI 48 h post-device removal. Four post-TAI treatments were evaluated: in CONTROL (T1, n = 161), cows were exposed to Nellore clean-up bulls until the end of the breeding season (75 days). In OBSERVATION (T2, n = 132), heat detection was performed for 15–25 days post-TAI, followed by AI. In RESYNC22 (T3, n = 157) and RESYNC30 (T4, n = 157), resynchronisation started after 22 or 30 days, following second TAI at Day 32 or 40 days after first TAI. In T2, T3 and T4, after the second AI, cows were exposed to Nellore clean-up bulls until the end of the breeding season (75 days). The pregnancy rate (PR) for the first TAI did not differ (54.6%, 53.0%, 59.2%, and 51.6% for CONTROL, OBSERVATION, RESYNC 22, and RESYNC 30, respectively; P = 0.66), and no difference was observed for the second TAI (RESYNC 22 = 45.31% and RESYNC30 = 46.05%; P = 0.137), in the PR at the end of the breeding season (86.33%, 86.36%, 78.98%, and 81.52%, P = 0.43), or embryonic losses (4.54%, 2.85%, 6.45% and 7.40%, respectively; P = 0.61), but the percentage of crossbred pregnancy was higher in groups with resynchronisation (RESYNC22 and RESYNC30) than CONTROL and OBSERVATION (98.38%, 90.62%, 63.30%, 78.95%, P &lt; 0.001). In conclusion, resynchronisation programs of 22 or 30 days are more efficient to produce AI products, and the final pregnancy rate is similar among the treatments, differing only in the amount of calves produced by AI.

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