Adoptable Formulae for Estimating Testicular Volumes Using Ultrasound Biometrics in Red Sokoto Goat Bucks

Lukman Oladimeji Raji, Uchebuchi Ike Osuagwuh, Sadudeen Adetayo Amid, Rashidah Abimbola Mustapha 1Department of Theriogenology and Production, University of Ilorin, Ilorin, Nigeria 2Department of Theriogenology, Michael Okpara University of Agriculture, Abia, Nigeria 3Department of Veterinary Surgery and Radiology, University of Ilorin, Ilorin, Nigeria 4Department of Theriogenology and Production, Ahmadu Bello University, Zaria, Nigeria


Introduction
The Red Sokoto Goat (RSG) is an excellent source of protein in terms of meat and milk. It is one of the three major breeds of goats commonly reared in Nigeria. It is most populated in the Northern part of Nigeria (Akpa et al., 2002;Maidu et al., 2010). It is part of the small ruminants' population popularly referred to as the "cattle of the poor" because its rearing is peculiar to low income earners usually in the rural settings (Taiwo et al., 2005;Adebayo and Chineke, 2011). Therefore, improving on RSG production will definitely go a long way in alleviating the challenges of protein deficiency particularly amongst the poor population as affordable protein and income will be readily available (Kues and Niemann, 2004;Anaeto et al., 2010).
The RSG buck (typical of a male livestock) constitute about half of the reproductive capacity of the RSG farm and serves many does on the farm; at least at a ratio of 1:5 (Akpa et al., 2010). Therefore, regular assessment of its reproductive capability is of utmost importance for maximum production purposes. This is usually done using the Breeding Soundness Examination (BSE) protocol (Memon et al., 2007;Ford et al., 2009;Tibary et al., 2018). In recent times, testicular ultrasound is being adopted into this protocol for male animals (Kollin et al., 2006;Ali et al., 2011;Carazo et al., 2014;Saeed and Zaid, 2018). Also, this method has been used to take important testicular biometric parameters such as testicular volume -an index of spermatogenesis (Paltiel et al., 2002;Sotos and Tokar, 2012;Raji et al., 2016). However, there are no reports to this effect in the RSG buck. Therefore, this present study was carried out to determine the adoptable formula for estimating testicular volume by ultrasound in the RSG bucks for improved production purposes.

Animals
Sixteen RSG bucks were acquired and divided into two groups comprising of group A -pubertal bucks (n = 8) and group B -post pubertal bucks (n = 8). These age categories were determined by a preliminary study in which the bucks were electro-ejaculated and semen collected were analyzed. The RSG bucks that spermatozoa were observed in their ejaculate for the first time were categorized as pubertal bucks (six-month old bulks) while those that the semen characteristics were similar to those described in a study on West African Dwarf bucks (Raji and Ajala, 2015) for fully matured bucks were categorized as the post pubertal RSG bucks (two-year old bulks). The bucks were kept and stabilized at the goat unit of the Faculty of Veterinary Medicine, University of Ilorin, Ilorin, Kwara State, Nigeria.

Testicular ultrasound and biometrics
The mobile ultrasound machine (4Vet Mini made by Draminski) was used in this study. The bucks were properly restrained; the testes were thoroughly cleaned with cotton wool soaked in methylated alcohol before ultrasound gel was generously applied on them. The testes were not shaved because the hair on them were not significant enough to cause any obstruction to the sonogram. Testicular ultrasound was carried out on transverse and longitudinal planes on the right and left testes. The electronic caliper on the ultrasound machine was used to take important parameters such as testicular width, length, height and volume.

Testicular width
This was measured on the Transverse Plane as (TP) as the widest diameter between the lateral and the medial aspects of the testis (Figure 1).

Testicular height
This was measured on the LP as the distance between the highest ventral points to the lowest dorsal points on the testis ( Figure 2).

Testicular volume
Testicular Volume (TV) was then estimated from the Testicular Width (TW), Length (L) and Height (H) using the Prolate Ellipsoid Formula (PSF), Prolate Spheroid Formula (PSF) and Lambert Formula (LF) as described earlier (Sotos and Tokar, 2012;Raji et al., (2016). The formulas are as follows: The TV obtained by testicular ultrasound were then compared with the true testicular volumes obtained by the Water Displacement Method (WDM). The WDM was done as described earlier by Raji et al., (2016). Briefly, the testes were harvested, separated from the epididymides and put in calibrated measuring cylinder filled with normal saline. The volume of normal saline the testis displaced, was taken as its volume, representing the true testicular volume.

Statistics
Data obtained were expressed as means ± standard deviation. One-way Analysis of Variance (ANOVA) followed by Dunnet's post hoc test and independent samples t-test were used to analyze the data. Values of p < 0.05 were considered significant.

Results
The results of testicular ultrasound biometrics for the pubertal and post pubertal RSG bucks were as presented on Tables (1-5). Table 1 and Table 2 show the testicular volumes estimated using the WDM, PSF, PEF and LF for each of the right and left testes for the pubertal and post pubertal bucks respectively. Table 3 shows the comparison of true testicular volumes of both testes for the pubertal bucks obtained using the WDM with the testicular volumes obtained using the PSF, PEF and LF. There were no significant differences in the TV estimated using the PSF (p = 0.00) and LF (p = 0.01) when compared with the true TV obtained using the WDM. The testicular volume estimated using the PEF was significantly lower (p= 0.08) than those obtained using the WDM in the pubertal bucks. Table 4 shows the results for the post pubertal RSG bucks true TV obtained using the WDM compared with the TV obtained using the PSF, PEF and LF. There were no significant differences in the TV estimated using PSF (p = 0.00), PEF (p= 0.01) and LF (p= 0.03) methods when compared to that obtained using the WDM. Table 5 shows a comparison of the TV estimated using the WDM, PSF, PEF and LF for pubertal and post pubertal bucks. The mean TV obtained using the WDM, PSF, PEF and LF were all significantly higher (p < 0.05) in post pubertal bucks compared to those of the pubertal bucks. Table 1: Estimation of testicular volumes of pubertal goat bucks (mean ± SD) of the right and left testes by ultrasound using the prolate ellipsoid formula, prolate spheroid formula, Lambert formula and compared with true testicular volume estimated using the water displacement method.   Table 2. Estimation of testicular volumes of post pubertal goat bucks' (mean ± SD) of the right and left testes estimated by ultrasound using the prolate ellipsoid formula, prolate spheroid formula, Lambert formula and compared with true testicular volume estimated using the water displacement method.   3. Estimation testicular volumes of pubertal goat bucks' testicular volumes (means ± SD) of both testes by ultrasound using the prolate ellipsoid formula, prolate spheroid formula, Lambert formula and compared with true testicular volume estimated using the water displacement method.  Table 4. Red Sokoto post pubertal goat bucks' testicular volumes of both testes estimated by ultrasound using the prolate ellipsoid formula, prolate spheroid formula, Lambert formula and compared with true testicular volume estimated using the water displacement method (expressed in mean ± standard deviation).

Discussion
In this study, testicular ultrasound biometrics was carried out to determine the adoptable formula that could be used for estimating testicular volume of pubertal and post pubertal RSG bucks with the aim of improving on their BSE protocol. Results revealed that the TV estimated using PSF and LF were not significantly different from the true TV estimated using the WDM. However, the TV estimated using the PEF were significantly lower than the true TV obtained by the WDM. These suggest that the only two of the three formulae i.e. PSF and LF can be used for estimating testicular volume for the pubertal RSG bucks. We also observed that contrary to the pubertal RSG bucks, the three formulae i.e. PSF, LF and PEF were all suitable for estimating the TV by ultrasound for the post pubertal RSG bucks as their values were not significantly different from the true TV by WDM.
The findings of our present study are contrary to the report by Raji et al., (2016) where they recommended the PEF as the most suitable formula for estimating testicular volume by ultrasound in post pubertal West African Dwarf (WAD) goat bucks which are a different breed of goats. Also, the values of TV for the post pubertal RSG bucks in this study were higher than those reported earlier for fully matured WAD bucks (Raji et al., 2016). These variations may be attributed to the fact that these goat bucks are of two different breeds even though of the same species. This also further shows that testicular ultrasound biometrics is necessary for other breeds of goats as the data for the BSE of WAD bucks cannot be used for RSG bucks because they vary in values; also in formula for obtaining the TV for the two different breeds of goats varies as earlier highlighted. This study revealed that the use of a non-invasive methods such as testicular ultrasound in taking important reproductive parameters will replace the invasive methods which usually requires the harvest of the testes thereby compromising the reproductive lives of such male animals ((Alper and Ibrahim, 2019;Fesseha, 2019).
This study also revealed that the testicular volumes of the RSG post pubertal bucks estimated by ultrasound using the PSF, PEF, LF and the WDM were significantly higher than those of the pubertal bucks. This suggests that the post pubertal bucks will potentially produce more semen than the pubertal bucks. Hence, better performances are expected from the post pubertal bucks to increase the farm population and ultimately, increase protein supplies in terms of meat and milk. This further corroborates earlier reports that better results would be achieved to use post pubertal bucks that have reached their optimum breeding age in place of pubertal bucks which are often not fully ready for reproduction (Souza et al., 2011;and Raji and Ajala 2015).

Conclusion
The present study highlighted the testicular ultrasound biometrics of pubertal and post pubertal RSG bucks with particular emphasis on testicular volume estimation. The PSF, LF and PEF (in this order of preference) are recommended for the estimation of testicular volume by ultrasound for the post pubertal RSG bucks while only the PSF and LF are recommended for the pubertal RSG bucks. The findings of this study will be valuable in improving on the clinical practice of testicular ultrasound and BSE of RSG bucks thereby leading to increase RSG production and animal protein supply. However, based on our observation in the present study, we want to suggest that more researches should be done in the area of testicular ultrasound biometrics in the various breeds and species of animals as there could be variations in breeds and species of animals. This is important because testicular volume is an invaluable reproductive parameter usually evaluated during the BSE of male animals. It is an index of spermatogenesis i.e the higher the testicular volume of a male livestock animal, the higher the probability of it increasing the population of the farm animals (Kollin et al., 2006;Pintus et al., 2015).