FERTILITY OF EPIDIDYMAL CAUDA SPERM FROM SUBFERTILE STALLIONS

Abstract

Epididymal sperm harvest aims the recovery of genetic material from valuable stallions that
gone dead, euthanized or with obstructive processes. However, subfertile stallions may also
benefit from this technique, since epididymal sperm has no contact with potentially
deleterious seminal plasma (SP). The goal of the present study was to compare sperm
viability between ejaculated (Group 1, G1) and epididymal cauda sperm (Group 2, G2) and to
test fertility of epididymal sperm post-thaw from subfertile stallions. Two stallions from
Mangalarga Marchador breed with history of subfertility were used. Three ejaculates from
each stallion were collected and frozen in G1. One week later the stallions were castrated and
sperm were harvested from epididymis using retrograde flushing (G2) with Botu-SêmenTM
and then frozen with Botu-CrioTM. For fertility trial, 8 mares were inseminated with postthawed epididymal sperm from G2. Immediately after the detection of ovulation, mares were
inseminated with 800x106
sperm (400 x106
from each stallion) in tip of uterine horn. All
sperm parameters were analyzed by ANOVA followed by Tukey’s test to identify significant
differences (p<0.05). Sperm concentration obtained in G1 and G2 were, respectively:
6.9±3.37b
e 20.4±5.37a
x 109
. Sperm parameters for G1 and G2 before freezing were,
respectively: a) Total Motility (TM): 16.0±6.16b
; 66.5±6.24a
; b) Progressive Motility (PM):
4.5±2.52b
; 26.3±7.93ª; c) Rapid Sperm (RAP): 7.7±4.27b
; 48.8±5.38a
; d) Plasma Membrane
Integrity (PMI): 26.8±12.36a
; 46.3±19.87ª; frozen-thawed parameters were: a)TM: 7.7±2.22b
;
33.3±2.06ª; b) PM:1.8±1.26b
; 12.5±3.32ª; c)RAP: 2±1.41b
; 19.3±1.26ª; d)PMI: 22.3±6.02b
;
41.8±10.59ª. Sperm parameters (TM and RAP) before and after freezing were superior in G2.
Sperm harvested from epididymal cauda were not in contact with SP, which can be one of the
possible causes of G1 increase on sperm viability. The conception rate obtained in G2 was
25% (2/8). Based on these results, we can conclude that harvesting sperm from epididymal
cauda of stallions with poor semen viability has increased on TM and RAP when compared to
the ejaculate. Moreover, pregnancy rates of 25% demonstrate that post-thawed epididymal
cauda sperm were able to fertilize the oocyte. This result demonstrates the possibility to
obtain foals from epididymal cauda sperm of subfertile stallions. However, more studies are
necessary to identify the possible detrimental effects of SP on semen quality of infertile and
subfertile stallions.