2018: TESTICULAR SIZE AS AN INDICATOR OF POOR SPERM OUTPUT IN WHITE-TAILED (ODOCOILEUS VIRGINIANUS) AND MULE (ODOCOILEUS HEMIONUS) DEER BUCKS


 

Testicular size as an indicator of poor sperm output in white-tailed (Odocoileus virginianus) and 
mule (Odocoileus hemionus) deer bucks 

 
 With rising popularity of cervid hunting, there is an increased demand for epididymal harvesting 
as a final option to preserve genetics of valuable bucks. While seasonality plays a crucial role in 
reproductive characteristic fluctuations in bucks, little is known about minimal testicular volume and 
sperm output.1 Here we describe morphological and histological characteristics of abnormal testes from 
captive white-tailed deer (WTD) and mule deer (MD) bucks and a normal white-tailed deer (CONT) in 
rut. 
 All three testicle pairs were obtained postmortem examination during peak rut (Oct to Dec) and 
shipped overnight on ice for routine epididymal sperm harvest. Cauda epididymis and vas deferens were 
removed, dissected, and flushed with Optixcell extender (IMV Technologies). The CONT flush yielded a 
total output of 2.5 billion sperm with 56% motility. In comparison, the WTD flush yielded dilute semen 
(<10 million sperm/mL) with 50% motility. The MD flush revealed no mature spermatozoa, but 
numerous spheroids. Testes measurements were used to estimate testicular volume, as shown in the table. 
The CONT testes exceeded the minimum recommended volume of 25 cm3, whereas the WTD and MD 
testes were subpar.  
 Testes were fixed in 10% formalin, paraffin-embedded, and stained with hematoxylin and eosin 
and Masson’s trichrome. The WTD testes had marked collagen and connective tissue present within 
interstitial spaces. Additionally, there was reduced spermatogenesis within seminiferous tubules 
compared to CONT. The MD testes showed no evidence of spermiogenesis within the seminiferous 
tubules and increased collagen deposition and disorganization within the interstitial space. Lack of 
spermiogenesis in the MD suggests potential hereditary hypoplasia, whereas the WTD may have been 
undergoing testicular atrophy.2 Though different etiologies, both findings indicate that testicular size can 
be useful as an indicator of sperm output and a predictor of sub- or infertility in WTD and MD. 
Establishment of minimal testicular volume necessary for a successful epididymal flush would prevent 
unnecessary shipment of unusable testes. 
 
Table. Testicular volume estimation (TV=0.5236×L×W2; L=length, W=width)1 

 
Keywords: Cervidae, epididymal sperm harvest, hypogonadism, semen quality 
 
References 
1. Stewart J, Schmidt L, Ellerbrock RE, et al: Effects of seasonality on male white-tailed deer (Odocoileus virginianus) 

reproductive characteristics. Am Assoc Small Rumin Pract Research Summary, Omaha, NE. 2017. 
2. Marburger RG, Robinson R, Thomas JW: Genital hypoplasia of white-tailed deer. J Mammal 1967;48:674-676. 

 CONT WTD  WTD MD  
Left Right Left Right Left Right 

Length (cm) 7.8 7.5 3.9 4.5 4.4 3.8 
Width (cm 3.7 4.5 2.5 3.2 2.0 2.0 
Volume (cm3) 55.91 79.52 12.76 24.13 9.21 7.98 

Clinical Theriogenology • Volume 10,  Number 3 • September 2018359

N. Sugaia, C.F. Shipleya, R.E. Ellerbrockb, J.L. Stewarta 
aCollege of Veterinary Medicine, University of Illinois Urbana-Champaign, Urbana, IL  

bCollege of Veterinary Medicine, University of Georgia, Athens, GA