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Evaluation of later timepoints for fixed-time artificial insemination of beef heifers and cows when using sex-sorted semen.
- Source :
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Theriogenology . Jan2024, Vol. 214, p334-341. 8p. - Publication Year :
- 2024
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Abstract
- Two experiments were designed to evaluate later timepoints for fixed-time artificial insemination (FTAI) of beef heifers and cows, with the hypothesis that use of a later timepoint would allow a greater proportion of animals to express estrus prior to FTAI and result in greater conception rates among estrous females inseminated with sex-sorted semen. In Experiment 1, estrus was synchronized for 1640 heifers using the 14 d CIDR-PG protocol: insertion of an intravaginal progesterone-releasing insert (CIDR; 1.38 g progesterone) on Day −33 and removal on Day −19, and administration of prostaglandin F 2α (PG; 500 μg cloprostenol sodium) on Day −3. Heifers were inseminated at one of three FTAI timepoints: 66 h, 70 h, or 74 h after PG administration. In Experiment 2, estrus was synchronized for 414 beef cows using the 7 & 7 Synch protocol: administration of PG coincident with CIDR insertion on Day −17, gonadotropin-releasing hormone (GnRH; 100 μg gonadorelin) on Day −10, and PG coincident with CIDR removal on Day −3. Cows were inseminated at one of two FTAI timepoints: 66 h or 72 h after PG administration. In both experiments, only animals that expressed estrus prior to FTAI were inseminated with sex-sorted semen. In Experiment 1, the proportion of heifers that expressed estrus prior to FTAI (66 h: 62 %; 70 h: 67 %; 74 h: 71 %) was greater when FTAI was performed at 74 h versus 66 h (P = 0.0097); however, conception rate of heifers that expressed estrus and were serviced with sex-sorted semen did not differ among treatments (P = 0.67; 66 h: 56 %; 70 h: 53 %; 74 h: 53 %). In Experiment 2, the proportion of cows expressing estrus prior to FTAI did not differ between treatments (P = 0.30; 66 h: 71 %; 72 h: 76 %). Additionally, conception rate of estrous cows inseminated with sex-sorted semen did not differ between treatments (P = 0.24; 66 h: 45 %; 72 h: 40 %). These results indicate that performing FTAI later following the 14 d CIDR-PG protocol increases the proportion of heifers that express estrus and are serviced with sex-sorted semen but does not improve conception rates. Later timing of FTAI following the 7 & 7 Synch protocol was not observed to increase the proportion of cows expressing estrus prior to FTAI or improve conception rates among estrous cows inseminated with sex-sorted semen. Together, these results provide further insight into optimal timing of FTAI when using sex-sorted semen. • Delayed timing of FTAI when using sex-sorted semen was evaluated. • A greater proportion of heifers expressed estrus prior to FTAI at later timepoints. • Conception rates were not improved among animals inseminated at later timepoints. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 0093691X
- Volume :
- 214
- Database :
- Academic Search Index
- Journal :
- Theriogenology
- Publication Type :
- Academic Journal
- Accession number :
- 173856010
- Full Text :
- https://doi.org/10.1016/j.theriogenology.2023.11.005