Conception rate following timed artificial insemination protocols in dairy heifers synchronised by PGF2α and GnRH

The objective of this study was to evaluate the efficiency and cost of two distinct hormonal protocols for induction of puberty in Bos indicus heifers in the western Amazon region. Nelore prepubertal heifers (n = 127) aged 20 to 24 months (21 ± 0.3 months) and weighing 300 to 340 kg (318 ± 7 kg) were submitted to two distinct protocols for induction of cyclicity. Females were previously submitted to two ovarian ultrasound examinations (12-day interval) to verify the absence of the corpus luteum (CL). Then, the heifers were divided into two experimental groups: G-CIDR/EC (n = 54) and G-P4/EC (n = 73). The G-CIDR/EC group utilized a CIDR® for 12 days and on the day of its withdrawal, 0.6 mg of estradiol cypionate (IM) was administered. The G-P4/EC group received 150 mg of injectable progesterone (IM) and one injection of 0.6 mg EC 12 days after the progesterone injection. Twelve days after the end of the hormonal protocols, the heifers were submitted to another ultrasound evaluation for identification of cyclicity (ovulatory follicle or CL). These females were then submitted to a conventional protocol of synchronization of ovulation for timed artificial insemination (TAI). Only heifers responsive to puberty induction (G-CIDR/EC (n=30) and G-P4/EC (n=51)) were included in the TAI protocol. After seven days of insemination, both groups were exposed to natural breeding. In addition, an economic analysis was performed to evaluate cyclicity induction, the TAI protocol, and pregnancy in both groups. The G-CIDR/EC group showed 81.48% (44/54) of females responsive to induction of cyclicity (presence of CL) while the G-P4/EC group obtained 86.3% (63/73; p=0.463). Regarding the conception rate to TAI and to bull (natural breeding), the G-CIDR/EC group displayed 43.33% (13/30) and 33.33% (10/30), respectively, and the G-P4/EC group exhibited 54.9% (28/51) and 39.22% (20/51), respectively. The overall pregnancy rate (TAI+Bull) was 76.67% (23/30) in the G-CIDR/EC group compared to 94.12% (48/51; P=0.023) in the G-P4/EC group. The cost of the hormonal protocol to cyclicity induction resulted in an economy of 42.8% for injectable P4 compared to the intravaginal P4 group. In addition, the final cost of cyclic induction associated with TAI was 34% lower in the G-P4/EC group compared to the G-CIDR/EC group. We concluded that both cycling induction protocols were efficient in Bos indicus heifers from the western Amazon. However, injectable P4 provided a higher conception rate and lower pregnancy cost at the end of the reproductive season.

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Effect of day of the estrous cycle at the initiation of a timed artificial insemination protocol on reproductive responses in dairy heifers.

Journal of Animal Science ◽

10.2527/2000.7861568x ◽

2000 ◽

Vol 78 (6) ◽

pp. 1568 ◽

Cited By ~ 157

Author(s):

F Moreira ◽

R L de la Sota ◽

T Diaz ◽

W W Thatcher

Keyword(s):

Estrous Cycle ◽

Artificial Insemination ◽

Dairy Heifers ◽

Timed Artificial Insemination

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Pregnancy-associated glycoproteins (PAGs) and progesterone concentrations in Holstein heifers following two methods of estrus syncronization

Veterinaria México OA ◽

10.22201/fmvz.24486760e.2019.2.646 ◽

2019 ◽

Vol 6 (2) ◽

Cited By ~ 1

Author(s):

Mehmet Akkose ◽

Cigdem Cebi Sen ◽

Adnan Kirmit ◽

Omer Korkmaz ◽

Murat Onur Yazlik ◽

...

Keyword(s):

Artificial Insemination ◽

Fetal Death ◽

Prostaglandin F2α ◽

Control Group ◽

Estrus Synchronization ◽

Serum Progesterone ◽

Death Rates ◽

Dairy Heifers ◽

Multiple Sampling ◽

Timed Artificial Insemination

Pregnancy-associated glycoproteins (PAGs) and progesterone concentrations were assessed in Holstein heifers 28 days post-insemination, following estrus synchronization with either a double prostaglandin (PG) injection or the ovsynch protocol. Animals between 15 and 20 months of age, with a 3-3.5 BCS, were randomly assigned to three groups: Heifers in the control group (n = 70) were monitored for estrus behaviour for 21 days and inseminated when detected in standing heat; Estrus of heifers in the Ovsynch group (n = 70)) was synchronized following the Ovsynch protocol, and timed artificial insemination was performed 16 h after the completion of treatment; Animals in the PG group (n = 70) received two prostaglandin-F2α injections 11 days apart, were monitored for estrus behaviour for 2-5 days following the last injection, and inseminated when in heat. Serum PAGs and progesterone concentrations were measured in pregnant heifers (control group n = 25; ovsynch group n = 22; PG group n = 21) on day 28 after artificial insemination (AI). Mean serum PAGs concentrations (OD: optical density) were similar between groups (control = 3.37 ± 0.148, Ovsynch = 3.21 ± 0.136, and PG = 3.34 ± 0.143; p > 0.05). However, serum progesterone concentrations were found to be lower in the ovsynch group (4.70 ± 0.17 ng/mL) when compared to the PG (5.34 ± 0.13 ng/mL) or the control (5.37 ± 0.08 ng/mL) groups (p < 0.001). There was no correlation between serum PAGs and progesterone levels at day 28 post-insemination, or between early pregnancy PAGs concentrations and fetal death rates. Further research, including multiple sampling time points throughout gestation, after estrus synchronization protocols is warranted, to determine if there are associated temporal changes in PAGs and progesterone profiles that could impact reproductive parameters in dairy heifers.

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