CASA kinetic parameters are often evaluated in a diagnostic centre. How storage conditions affect ejaculates up to evaluation is unclear. We assessed, in 25 commercial bulls electroejaculated in the field, the impact of time until evaluation (0–2 h, 4–6 h, and 24 h post-ejaculation), holding temperature (5 °C vs. room temperature), and extender (AndroMed®, BIOXcell® or INRA96®) on CASA kinetic parameters. Total and progressive motility, VCL, VAP, VCL, ALH, BCF, STR, LIN, and WOB were assessed. CASA kinetic parameters were preserved for up to 4–6 h post-ejaculation, except for AndroMed®. Regardless of extender or temperature, motility decreased from 4–6 h up to 24 h, with the best values obtained with BIOXcell® at 5 °C. Our results suggest that BIOXcell® can preserve sperm motility for up to 6 h, either at 5 °C or room temperature, and also INRA96® at room temperature, with motility assessments and the percentage of the most rapid sperms being the lowest with INRA96® at 5 °C. The kinetic parameters decreased when analyses were performed at 24 h. Therefore, we suggest evaluating seminal quality as soon as possible, before 6 h after collection. These results help to fix adequate protocols for the short-term storage and shipment of bovine semen collected under field conditions.

Seminal parameters can be evaluated in situ, or samples can be delivered to a diagnostic centre. How storage conditions affect ejaculates up to evaluation is unclear. We assessed, in 25 commercial bulls electroejaculated in the field, the impact of time until evaluation (0–2 h, 4–6 h, and 24 h post-ejaculation), holding temperature (5 °C vs. room temperature), and extender (AndroMed®, BIOXcell® or INRA96®) on semen quality. Acrosome integrity, sperm viability and morphology, CASA-total and progressive motility, pH, and colony-forming units were assessed. Semen quality was preserved for up to 4–6 h post-ejaculation, except for INRA96® at 5 °C. Regardless of extender or temperature, motility decreased from 4 to 6 h up to 24 h, with the best values obtained with BIOXcell® at 5 °C. pH differed from 4 to 6 h up to 24 h, acidifying when stored at room temperature. Microbiological load was stable over time with AndroMed® and BIOXcell®, and increased at room temperature with INRA96®. Our results suggest that AndroMed® and BIOXcell® can preserve semen quality for up to 6 h, either at 5 °C or room temperature, while INRA96® only at room temperature. These results help to fix adequate protocols for short-term storage and shipment of bovine semen collected under field conditions.

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.

Background In beef herds, increasing animal welfare, improving reproductive performance and easing animal management are key goals in farm economics. This study 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 whether such a modified protocol would provide an acceptable, 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), the standard 5d Co-synch 72 h protocol (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). Heifers were considered synchronized (TSR) if serum progesterone value > 1.0 ng/mL and the corpus luteus (CL) was detectable by ultrasonography on Day 5, if progesterone < 1.0 ng/mL and at least one follicle had a diameter > 8 mm on Day 7.5, and if progesterone > 1.0 ng/mL and CL was detectable on Day 15. In Experiment 2, 309 cycling beef heifers on 18 commercial farms were subjected to the 5d Co-synch 72 h or 6d Co-synch 48 h protocol and conception rate (CR) studied. Results In experiment 1, the three protocols in dairy heifers 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). Heifer age, body condition score or stress score did not significantly affect conception rate. Conclusions These results suggest that delaying removal of the intravaginal progesterone device by 24 h during the standard 5d Co-synch 72 h protocol provides satisfactory results without reducing reproductive efficiency of heifers.