Journal article
Effect of time from estrus to AI on pregnancy rates in estrous synchronized beef heifers
Animal reproduction science, Vol.127(1), pp.1-6
2011
Handle:
https://hdl.handle.net/2376/109056
PMID: 21911186
Abstract
For the last 65 years, the industry standard for time of artificial insemination (AI) relative to onset of estrus has been established as 12
h after observed estrus. More recent experiments indicated the optimum time for AI was 4–12
h after onset of estrus in dairy cattle, but little recent information is available on the effect of time of AI relative to the onset of estrus in beef cattle. Therefore, we conducted a retrospective study on the impact of time from onset of estrus to artificial insemination using records from estrous synchronized crossbred Angus heifers (
n
=
1205). Data were compiled from experiments on estrous synchronization systems and AI where estrous detection was performed electronically with HeatWatch
®. Only data from heifers detected in estrus was used. Heifers averaged 440 days of age, and weighed 368
kg at insemination. Heifers were assigned to one of the following 4
h blocks of time based on time from onset of estrus (hour 0) to insemination: 0–4 (
n
=
79), 4–8 (
n
=
163), 8–12 (
n
=
211), 12–16 (
n
=
163), 16–20 (
n
=
193), 20–24 (
n
=
149), >24
h (
n
=
247). Pregnancy rates to AI were not affected by AI technician or season of breeding (
P
>
0.80). However, time of insemination relative to onset of estrus affected (
P
<
0.01) pregnancy rates to AI. Heifers inseminated between 4 and 24
h after onset of estrus had greater AI pregnancy rates (
P
<
0.05; 63.7%) compared to the 0–4
h (48.1%) and >24
h (55.9%) groups. The time period for achieving acceptable pregnancy rates to AI in beef heifers appears to be approximately 20
h in length. Estrous synchronization programs resulting in a majority of heifers in estrus between 4 and 24
h before AI should yield the greatest pregnancy rates.
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Details
- Title
- Effect of time from estrus to AI on pregnancy rates in estrous synchronized beef heifers
- Creators
- B.R Dorsey - Department of Animal and Poultry Sciences, 3500 Litton Reaves, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USAR Kasimanickam - Department of Large Animal Clinical Sciences, VA-MD Regional College of Veterinary Medicine – Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USAW.D Whittier - Department of Large Animal Clinical Sciences, VA-MD Regional College of Veterinary Medicine – Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USAR.L Nebel - Select Sires, Inc., 11740 U.S. 42 North, Plain City, OH 43064, USAM.L Wahlberg - Department of Animal and Poultry Sciences, 3500 Litton Reaves, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USAJ.B Hall - Department of Animal and Poultry Sciences, 3500 Litton Reaves, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
- Publication Details
- Animal reproduction science, Vol.127(1), pp.1-6
- Academic Unit
- Veterinary Clinical Sciences, Department of
- Publisher
- Elsevier B.V
- Identifiers
- 99900546744801842
- Language
- English
- Resource Type
- Journal article