Comparison of melengestrol acetate and controlled internal drug-release long-term progestin-based synchronization protocols on fixed-time artificial-insemination pregnancy rate in beef heifers

The aim of the present study was to determine the effects of one or two doses of prostaglandin F2α (PGF) on the pregnancy rate (PR) in Simmental cows subjected to the Ovsynch or Ovsynch + Controlled internal drug release (CIDR) protocols. On d 0, 100 µg gonadorelin diacetate tetrahydrate (GnRH) was injected into cows in group 1 (n = 50) and group 2 (n = 40) and CIDR was intravaginally inserted. On d 7, 25 mg dinoprost tromethamine (PGF2α, PGF) was administered, and GnRH was injected 56 h later. Fixed-time artificial insemination (TAI) was performed 16 h after GnRH injection. In group 3 (n = 62) and group 4 (n = 63), PGF was administered 7 d following GnRH treatment, and GnRH was injected 56 h later. TAI was performed 16 h after GnRH injection. In groups 2 and 4, a second dose of PGF was injected 24 h after the first dose. Pregnancy was determined by transrectal ultrasonography on d 30 and 60 post-TAI. The pregnancy rate (PR) on d 30 post-TAI was significantly different among the groups: 46%, 55%, 29%, and 36.5%, in groups 1, 2, 3, and 4, respectively (P = 0.048). In addition, the PR was 36.3% and 43.7% in the single PGF and double PGF injection groups, respectively. There was no statistical difference in the PR on d 60 post-TAI (P > 0.05). Pregnancy loss was between 4.34% and 11.11% (P > 0.05). The highest PR in the primiparous cows was observed in group 3 (57.7%). The PR was not significantly different among multiparous cows (P > 0.05). In conclusion, two injections of PGF administered 24 h apart in Simmental cows may increase the PR in the Ovsynch or Ovsynch + CIDR protocols.

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Association between length of proestrus, follicular size, estrus behavior, and pregnancy rate in beef heifers subjected to fixed–time artificial insemination

Theriogenology ◽

10.1016/j.theriogenology.2021.12.028 ◽

2021 ◽

Author(s):

R. Núñez–Olivera ◽

G.A. Bó ◽

A. Menchaca

Keyword(s):

Pregnancy Rate ◽

Artificial Insemination ◽

Fixed Time ◽

Beef Heifers ◽

Follicular Size ◽

Estrus Behavior

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233 Estrus Response and Pregnancy Rates of Beef Replacement Heifers Enrolled in Two Fixed-time Artificial Insemination Protocols, with or Without Pre-synchronization

Journal of Animal Science ◽

10.1093/jas/skab235.228 ◽

2021 ◽

Vol 99 (Supplement_3) ◽

pp. 125-126

Author(s):

Vitor R G Rodrigues Gomes Mercadante ◽

G Cliff C Lamb ◽

Nicky Oosthuizen ◽

Nicholas W Wege Dias ◽

Stefania Pancini ◽

...

Keyword(s):

Body Weight ◽

Pregnancy Rate ◽

Artificial Insemination ◽

Prolonged Exposure ◽

Prostaglandin F2α ◽

Fixed Time ◽

Transrectal Ultrasonography ◽

Beef Heifers ◽

Estrus Response ◽

Exogenous Progesterone

Abstract Pre-synchronization strategies with prolonged exposure to exogenous progesterone have the potential to alter estrus expression and improve fertility in replacement beef heifers. The objective of this study was to evaluate the estrus response and pregnancy rate of beef heifers enrolled in two fixed-time artificial insemination (TAI) protocols. A total of 306 heifers (14 ± 2 months of age; 372 ± 24 kg body weight [BW]) at three locations were enrolled in the study. Within location, heifers were stratified by age and BW and randomly assigned to one of two treatments: 1) PG-CIDR54 (n = 152), heifers were administered prostaglandin F2α (PGF; 25 mg) and a controlled internal drug releasing (CIDR) insert (Day -14), an injection of GnRH [100 μg (Day -7)], PGF injection and CIDR removal (Day 0), and a second injection of GnRH concurrently with TAI 54 ± 2 h later (Day 2); 2) 7-day CO-Synch+CIDR (CTRL; n = 154), heifers were administered GnRH (100 μg) and a CIDR insert (Day -7), PGF (25 mg) injection and CIDR removal (Day 0), and a second injection of GnRH concurrently with TAI 54 ± 2 h later (Day 2). All heifers received an estrus alert patch on Day 0 and were evaluated for patch activation at TAI on Day 2. Pregnancy was diagnosed by transrectal ultrasonography between 35 and 55 days after TAI. The percentage of heifers exhibiting estrus between Day 0 and 2 was greater (P < 0.01) in PG-CIDR54 compared with CTRL (77.0 and 39.6%, respectively). In addition, pregnancy rate to TAI tended (P = 0.08) to be greater for PG-CIDR54 compared with CTRL (48.0 and 38.3%, respectively). We conclude that beef heifers enrolled in the PG-CIDR54 protocol had increased estrus expression and tended to have greater pregnancy rate when compared with heifers enrolled in the 7-day CO-Synch+CIDR protocol.

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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 ◽

10.3390/ani11030849 ◽

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.

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