Fresh Semen Testing

Improve decisions with precise semen analysis on fresh semen pen-side

Bull fertility can be compromised for a myriad of reasons, poor nutrition [1], obesity [2], heat stress [3], and bacterial infection [4]. The majority of farm vets still rely on visual assessment using an optical microscope at the farm. When 65 farm vets were asked to assess the % progressive motility of a single video, results between experts varied by over 40% [5]. The challenge of accurate assessment is further exacerbated by air flow around open microscopes at the farm and issues around sample preparation protocols.

Pen-side fresh semen testing

The Dynescan is a portable, enclosed instrument with a unique underpinning technology that performs measurements of equal precision at the farm and in the laboratory using sealed channel slides for consistent sample preparation. Measurements of the % progressive motility and speed of spermatozoa can be performed over a wide range of concentrations from 1 – 550 million cells/ml, unlike other semen analysers. Results are reproducible with less than 3% standard deviation between users and measurements can be repeated at regular intervals over time to explore whether motility will be sustained in low oxygen conditions similar to the reproductive tract. When measuring fresh semen on farm we recommend a dilution of 1 part fresh ejaculate to 9 parts buffer (e.g. phosphate buffer saline) to obtain accurate measurement of % progressive motility. While it is possible to measure the % progressive motility within 2 minutes, we recommend taking regular measurements for up to 15 minutes with fresh diluted semen as shown in Figure 1.

Assessing Spermatozoa Swimming Speed and Progressive Motility in Low Oxygen
Fig 1. Dynescan measurements of the a) swimming speed and b) % progressive motility of spermatozoa over time allow us to explore the ability of spermatozoa to remain motile in low oxygen conditions, similar to the reproductive tract. Bull 3 is unable to retain motility in low oxygen conditions.

Bull 1 is an example of an excellent bull. The speed begins at 350 µm/s and then reduces after 10 minutes to around 150 µm/s. A drop in speed signifies the transition in the metabolic pathway from consuming oxygen to other energy sources within the media. Despite the drop in speed, the % progressive motility remains constant between 65-68% throughout.

Bull 2 is an example of bull that would not pass a bull fertility exam on the basis of poor % progressive motility. The speed is slow at around 40 µm/s. The % progressive motility is low at around 19-22% throughout. Bull 3 is an example of a bull that would have passed a bull fertility exam on the basis of its initial % progressive motility being over 60%, measured at 74% initially, and a vigourous swimming speed of 308 µm/s. As expected, the speed halves within 5 minutes indicating the transition in metabolic pathway to low-oxygen conditions. Unexpectedly, the % progressive motility drops dramatically falling to less than 15% within 10 minutes. This bull should not pass a bull fertility exam because its spermatozoa are unable to maintain motility in low-oxygen conditions similar to the reproductive tract. It is vital that spermatozoa are motile in low-oxygen conditions in order to fertilise the oocyte. A loss of motility at early times is associated with poor embryo growth and poor fertility outcomes [6].

A fast method to identify poorly performing bulls

Dynescan also has the capability to analyse undiluted fresh semen. While its capacity to measure accurately % progressive motility at concentrations above 550 million cells/ml may be affected by the presence of correlated motion, known as gross motility, Dynescan can measure swimming speed which provides insights into how well semen sustains motility in low oxygen conditions. Performing measurements on undiluted semen we measured 69% progressive motility for bull 1, 24% for bull 2 and 11% for bull 3 indicating that Dynescan measurements on fresh undiluted samples, taking just 2 minutes, are a good guide to understand motility in the reproductive tract. This is because the oxygen is consumed very quickly, before the measurement, at high cell concentrations. Strictly, it is not possible to measure accurately the % progressive motility of fresh semen at high concentrations because non-motile cells are swept along by motile cells but results suggest
that Dynescan measurements on undiluted fresh semen offer insights into activity in low-oxygen conditions.

Bull recovery plans

Bull 3 was observed to be lame suggesting that injury or infection has affected the anaerobic (low oxygen) pathway for spermatozoa. We anticipate that Dynescan measurements will become useful for detecting underlying conditions that are otherwise unobserved. Through developing a richer understanding of the connection between disease and semen quality, we will be able to identify treatment pathways and use the Dynescan to observe recovery of the bull. This will ensure that we are able to keep bulls with top genetic merit within the herd and reduce biosecurity risks associated with bring new bulls onto the farm. We encourage and support research projects to help improve our understanding of factors affecting bull fertility.

Picture of Hannah Nicholson

Hannah Nicholson

Junior Researcher, University of Edinburgh

The experiments were conducted by Hannah Nicholson, a Junior Researcher on placement at Dyneval.

This article might interest you

Semen longevity under heat stress conditions

References

  1. A. K. Singh, S. K. Rajak, K. Priyaranjan, S. Kerketta and R. K. Yogi, “Nutrition and bull fertility: A review,” Journal of Entomology and Zoology Studies, vol. 6, no. 6, pp. 635-643, 2018.
  2. P. I. P. Fontes, L. M. Goncalves, S. M. Zoca and S. Burato, “Impact of Sire Over-conditioning on Bull Fertility,” ARSBC Proceedings, 2023.
  3. M. B. Rahman, K. Schellander, N. L. Luceno and A. Van Soom, “Heat stress responses in spermatozoa: Mechanisms and consequences for cattle fertility,” Theriogenology, vol. 113, pp. 102-112, 2018.
  4. E. Moretti, S. Capitani, N. Figura, A. Pammolli, M. Grazia Federico, V. Giannerini and G. Collodel, “The presence of bacteria species in semen and sperm quality,” Journal of Assisted Reproduction and Genetics, vol. 26, pp. 47-56, 2009.
  5. Dyneval survey of 65 attendees of the British Cattle Veterinary Association congress in 2023, https://www.dyneval.com/dynescan-proves-to-take-bull-fertility-exams-to-a-new-level/
  6. J. G. Alvarez, J. F. Mortola, D. Minaretzis, I. E. Thompson and C. Brent Barrett, “The sperm stress test: a novel test that predicts pregnancy in assisted reproductive technologies,” Fertility and Sterility, vol. 2, p. 65, 1996.

Extend your capabilities with Dynescan

Join the Dyneval community to share your Dynescan research insights and connect with peers.

Latest

You have successfully subscribed!