Observations on CASA analyses of frozen bull semen

• Published in: Animal reproduction science Vol. 247; p. 107135
• Main Authors: McPherson, Françoise J, Chenoweth, Peter J
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2022
• ISSN: 0378-4320; 1873-2232
• DOI: 10.1016/j.anireprosci.2022.107135

Animal andrology laboratories (AALs) can be useful for identifying livestock semen fertility problems and providing Quality Assurance (QA) for semen processors. In the process, data are accumulated which is potentially useful for AAL QA and client feedback. To illustrate the former, this abstract presents results from laboratory analyses of frozen bull semen samples (0.25ml straws, total n=6417) submitted to a commercial AAL. Computer assisted sperm analyses (CASA, SpermVision©, Vostro 320, Minitube USA) included post-thaw total sperm motility (TMOT; initial and 2h), progressive sperm motility (PMOT; initial) and sperm concentration (CONC). In addition, four consecutive CASA readings on 108 samples were compared for TMOT, PMOT and CONC using Graph-Pad Prism Ver. 9.3. Descriptive statistics, correlations among traits and the repeatability of assessments (one-way ANOVA) were obtained with Graph-Pad Prism Ver. 9.3. Mean values (±SD) included: Initial TMOT 58.36 (±17.51% (n=5769); TMOT 2h incubation @ 370C, 29.06 (±20.49)% (n=648); Initial PMOT, 40.50 (±16.95)% (n=911); CONC, 126.6 (±61.5) 106/ml (n=6497); %N sperm, 77.14 (±14.55) % (n=13,932); and PIA, 86.9 (±10.93)% (n=1,045). Correlation coefficients included, TMOT vs PMOT, r = 0.88, TMOT vs CONC, r = 0.56, and PMOT vs CONC, r = 0.51 (all P<0.001). Results for CASA consecutive readings included: TMOT overall mean 47.89 (±17.61)%; consecutive means 48.33, 45.43, 42.50, 41.96 respectively, all ns; PMOT overall mean 35.34 ±16.41%, consecutive means 35.66, 32.69, 30.28, 28.90 respectively, all ns; and CONC overall mean 129.5 ±50.36 ×106/ml, consecutive means 130.7, 129.4, 129.6, 126.8 respectively, all ns. Although the mean and SD were lower for PMOT than TMOT, the two assessments were highly correlated with each other, implying that either could be reliably used as an assessment of frozen thawed bull semen motility. The significant associations (P<0.001) which were obtained between CASA motilities (TMOT and PMOT) and CONC do, however, reinforced the use of recommended sperm concentrations for CASA assessments as well as routine replay to ensure all sperm are appropriately tagged. Finally, the similarities between consecutive CASA readings for TMOT, PMOT and CONC for individual samples confirmed the validity of using rapid consecutive CASA measures to routinely check initial readings. This approach, however, is recommended in conjunction with other QC measures, such as image replay, to provide assurance that all sperm are being appropriately designated.