The heritability of pampiniform plexus vessel size and varicocele in boars

Authors: GRUHOT, TASHA - University Of Nebraska; Rempel, Lea; SPANGLER, MATTHEW - University Of Nebraska; STEPHEN, KACHMAN - University Of Nebraska; MOTE, BENNY - University Of Nebraska

Submitted to: Reproduction in Domestic Animals
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2018
Publication Date: 2/1/2019
Citation: Gruhot, T.R., Rempel, L.A., Spangler, M.L., Stephen, K.D., Mote, B.E. 2019. The heritability of pampiniform plexus vessel size and varicocele in boars. Reproduction of Domestic Animals. 54(2):270-274. https://doi.org/10.1111/rda.13350.
DOI: https://doi.org/10.1111/rda.13350

Interpretive Summary: The vasculature found just outside the testicular cavity, known as the pampiniform plexus, allows for countercurrent heat exchange to either warm or cool blood before it enters the testicles. When the blood vessels within the pampiniform plexus are abnormally dilated or have lesions it leads to a condition known as varicocele. Varicocele can cause inappropriate blood flow and thermal regulation especially during moderate heat stress, such as summer or autumn seasons. In humans, varicocele has been associated with male infertility and affected by genetics. An ARS scientist along with University of Nebraska researchers, using ultrasonography, measured the right and left pampiniform plexus vessel area and determined the presence of varicocele in a large population of young boars and derived the genetic heritability of vessel area and varicocele. Pampiniform plexus vessel area was highly heritable while presence of varicocele was moderately heritable. These data suggest that boars could be selected for both vessel area and presence of varicocele, thereby improving fertility characteristics of breeding boars, which would lead to improved economic and animal production efficiencies.

Technical Abstract: Ultrasonography was used to capture a coronal-sagittal image of the veins of the pampiniform plexus (PP) and the testicular artery of 327 maternal-line boars at approximately 6 months of age at the University of Nebraska-Lincoln. Varicocele was diagnosed by two methods. Method 1 diagnosed varicocele as when the average vessel area on one side of the scrotum was 1.5 times larger than the average vessel area on the other side of the scrotum. Method 2 diagnosed varicocele when the average vessel area on one side of the scrotum of a boar was 1.5 times larger than the average vessel for the same side of the scrotum of the boar’s cohorts (same population and year). Varicocele was diagnosed in 23.17% and 15.1% of boars measured using method 1 and method 2, respectively. Ultrasonography showed to be an effective means to measure PP vessel size in boars and may even allow for earlier detection of varicocele than by using palpation. Animal models were employed to estimate the heritability for: average area of right PP vessels (0.52), average area of the left PP vessels (0.46), varicocele presence using method 1 (0.26), and varicocele presence using method 2 (0.25). These heritability estimates suggest that vessel size and varicocele could be selected against in breeding programs to potentially improve boar semen quality.