VALORACIÓN DE LA APTITUD REPRODUCTIVA DE TOROS A TRAVÉS DEL ANÁLISIS DE IMAGEN DE LA ECOGRAFÍA TESTICULAR: PARÁMETROS DE HOMOGENEIDAD, HISTOGRAMA Y MICROESTRUTURA

Arantxa Echegaray Artajo¹, Nicolás Escartín Casas¹, Marta Guillén Palacín¹, Marta Oliván Nerín¹, Irene Fernández¹

(1)-Humeco

Introduction

Testicular ultrasonography is a crucial tool in bovine reproduction, allowing for the early detection of testicular abnormalities, assessing testicular parenchyma, and evaluating reproductive potential in breeding bulls. This non-invasive imaging technique provides detailed insights into testicular consistency, vascularization, and the presence of pathological conditions such as fibrosis or degeneration, which can significantly impact fertility. Moreover, ultrasonography is essential for monitoring testicular development in young bulls, aiding in the selection of high-quality sires for genetic improvement programs. In 2019, we developed a software to evaluate the echotexture of the testicles, ECOTEXT, allowing us to predict semen quality in males. Now, we are developing a new improved version, with new interesting parameters related to the homogeneity of the parenchyma. In this assay, we evaluate these new parameters, their interaction with the other ECOTEXT parameters and their prediction regarding bull fertility.

 

Material and methods

Ultrasound scans of the testicular area  were performed on a total of 54 bulls aged between 1 and 9 years. Ultrasonograms (3 transverse sonographic images of
each testicle) were carried out using an EXAPAD mini scanner (IMV IMAGING,
France) connected to a 5-7.5 MHz linear probe.

The echographic images were analysed by the
algorithms, selecting a region of interest (ROI) and obtaining the median
values of the 3 images for the following parameters: (EC1) black pixels, (EC2)
white pixels, (EC3) mean grey level of pixels, (Density) density of
hypoechogenic areas, (Diameter)  mean
diameter of hypoechogenic areas and (Area) percentage of hypoechogenic areas.
As a novelty, we have added 2 parameters, vertical and horizontal zonification,
related to the non-homogeneity of the parenchyma in the total area of the ROI.
The zonification values were expressed in levels of grey (0 to 256 in an 8-bit
image). Vertical zonification was measured in the vertical sense of the ROI and
horizontal zonification was measured in the horizontal path.

Afterwards, we electroejaculated the bulls to obtain a
semen sample. Then, we evaluated the following semen quantity and quality parameters:
volume (ml),  individual motility (%) sperm
concentration (millions of spermatozoa/ml) 
and percentage of major and minor morphoanomalies according to the
classification of Bloom (1973).

The relationship between the above parameters and
semen quality was analysed, using a Pearson correlation test, ANOVA, and
logistic regression analysis.

Results and discussion

There
were no differences between ipsilateral testicles in echotextural parameters
(p>0.05).

The Pearson correlation showed a high positive significant relationship between the age of the bull and the density of hypoechogenic areas in the ultrasonogram (R=0,78 p<0.01). Bulls younger than 1,3 years (n=23), most of them peripubertal, have very homogenous and compact parenchyma, with very low vertical zonification (mean values 11.4 + 4,4). Besides, these young bulls have a mean value of hypoechogenic areas of 77 ± 12,5 HA/cm2.  Older bulls have mean values of 132.2 ± 12,4 HA/cm2 and the difference with young bulls was highly significant (p<0.001). 34,8% of these peripubertal bulls do not give a sperm sample when electroejaculated and another 62.5% of them give ejaculates with very low sperm concentration and very high percentages of major sperm morphoanomalies.

As
in other ECOTEXT trials density of HA was the parameter better related to semen
quality. It showed very high and highly significant correlation coefficients with
semen concentration (p=+ 0.785, p<0.001)  and very high negative correlation coefficients
with major sperm anomalies (p=-0.873, p <0.001). This relationship is so strong
in this assay because our bull population is very heterogeneous in age and
semen quality.

A percentage of bulls with evident multifocal fibrosis (n=6)  showed elevated significant different values of vertical zonification (14,7 + 2,3 ) and horizontal zonification (14,3 + 3,7). More interesting, as not evident by the eye, all testicular parenchyma with a value of vertical or horizontal zonification inferior to 9,0 or superior to 12,0 is related to lower hypoechogenic areas density (p<0.004) and/or higher major sperm morphoanomalies (p<0.03). Our linear regression analysis showed the significant predictive potential of horizontal zonification (p=0.08) and hypoechogenic area density (p=0.004) for the percentage of major sperm anomalies with a regression coefficient r2 of 0.79.

Bibliography

Blom E. The ultrastructure of some characteristic sperm defects and a proposal for a new classification of the bull spermiogram. Nord Vet Med 1973;25:383–91.