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13 Feb 2020 - By Kasia Kupisiewicz, Project Manager R&D

No relevant correlation between progressive motility and field fertility

Progressive motility is one of the semen quality parameters evaluated in the laboratory, and it describes the ability of spermatozoa to progressively move towards oocyte and is seen by many parties as directly correlated to field fertility.

Progressive motility can be evaluated either subjectively using a microscope or via CASA instruments. At VikingGenetics, progressive motility is routinely measured for sexed semen but not for conventional semen. Our semen production laboratory in Assentoft, Denmark has IVOS II (CASA) instruments that enable objective, and precise measurements of the percentage of progressive motile sperm cells.

Although an insemination trial performed by VikingGenetics has shown that progressive motility is indeed correlated to field fertility, it was unable to contribute more understanding other than measuring concentration and viability.

Addressing increasing interest in progressive motility, we investigated the correlation between progressive motility and field fertility of sexed doses produced at VikingGenetics. Field fertility is represented by a non-return rate of 56 days (NRR 56), which is an internationally recognised measurement for fertility. NRR 56 describes a percentage of dams not returning to oestrus within 56 days of insemination.

The data were obtained for all sexed lots produced in 2017, 2018 and in the first quarter of 2019. Around 3,900 different samples were evaluated. The average progressive motility for each bull was correlated to his NRR 56.

The graph below shows the average progressive motility of sexed doses for a bull as a percentage (X-axis) and NRR 56 of the bull, also in percentages. Progressive motility is plotted against NRR 56 and there is no correlation between these two parameters. The correlation is illustrated by R2 value. R2 value can be between 0 and 1. An R2 value close to 0 means no correlation and vice versa, the closer the R2 value to 1 the greater the correlation between the two parameters. The calculated R2 value of 0.007 means that for the data used, there is no correlation between progressive motility and field fertility.