Routine bull breeding soundness examinations are common prior to the breeding season for rural mixed animal and bovine practices.  We have been conditioned to perform a quick semen evaluation including sperm motility and morphology and concern ourselves with only meeting the minimum standards of 30% or greater progression motility (PM) and 70% or greater normal morphology.  Essentially this is creating a pass or fail, both in the way we present the findings and the way cattle producers often interpret the results of the semen evaluation.  A complete differential spermiogram includes a percent of sperm PM and the percent of normal and the percent of each individual morphological abnormality.  Each morphological abnormality can have a different and significant effect on potential conception rates.  Taking the time to perform a complete differential spermiogram can help veterinarians to better assess potential bull fertility and prognosis, and help producers improve herd reproductive management.  Comparing two bull semen evaluations shows how we can use a complete differential spermiogram as an invaluable tool in assessing bull potential fertility.

Case #1: Differential spermiogram results: PM = 60%, morphologically normal sperm = 66% with pyriform/tapered heads = 9%, nuclear vacuoles = 5%, Detached head = 8 %, Rolled Head = 1%, Distal midpiece reflex = 7%, Tail stump defect = 3%, Teratoid = 1% and 2 round cells observed, no other differential morphological abnormalities.

Case # 2 Differential spermiogram results: PM = 70 %, morphologically normal sperm = 74 %, with pyriform/tapered heads = 13%, nuclear vacuoles = 9%, Detached head = 1 %, Rolled Head = 0%, Distal midpiece reflex = 3 %, Coiled principal piece = 1%, no other differential morphological abnormalities.

Following a strict morphologically normal sperm of 70% the bull case #1 would not be a satisfactory potential breeder where the bull in case # 2 would be considered a satisfactory potential breeder.  However, with closer analysis of the differential spermiogram and utilizing evidence-based parameters of the individual effects of each abnormality, would bring the astute observer to a different conclusion.  In case #1 detached heads account for 8% of the abnormalities, evidence has shown that levels of detached heads have little to no impact on fertility until approaching 30 -40% (Cooper, 1983) (Perry, 2018) and the total of pyriform/tapered heads, nuclear vacuoles, rolled – nuclear – giant heads, and proximal cytoplasmic droplets are less than 15% well within tolerable levels.  If removing the 8% of detached heads from the calculation of normal by taking 65% normal divided by a total of 92 sperm, we now have a 70% morphologically normal sperm.  This is now with in the normal limits.  In case #2 the total of pyriform/tapered plus nuclear vacuoles is 22% which levels have been shown to be high enough to have some detrimental effects on potential fertility. (Perry, 2018) (Barth, 2013)  This bull would be expected to have less than optimal results when used for breeding.

A complete blood count (CBC) could be used as an analogy.  Few good veterinary practitioners will only look at the white blood cell count and compare if the value is above or below the normal high designated number.  Especially if the results of the test are close to but not over this parameter.  We would then consider not only the history and physical exam findings but the complete differential.  If the patient has a high neutrophil count with band cells, we would treat the patient different than one where all differentials were within normal limits.

Understanding and utilizing a complete differential spermiogram can create real excellence in our performance of bull breeding soundness examinations.  It allows us a veterinary practitioner to help our clients optimize reproduction and the efficiencies within their herd.

The spermiogram chart can help create and use a complete spermiogram. The money collected from any sales will go towards creating more content and products to help improve herd reproductive efficiency through better bull breeding soundness evaluations.

References

Barth, A. D., 2013. Bull Breeding Soundness. 3rd ed. Saskatoon(Saskatchewan): Western Canadian Association of Bovine Practitioners.

Cooper, A., 1983. Infertility in a Herefor bull associated with increased numbers of detached sperm heads in his ejaculate.. Australian Veterinary Journal, Volume 60, pp. 225-6.

Perry, V., 2018. A refresher on sperm morphology. Brisbane, s.n.