The aim of the present study is to define and compare the predictive power of two different Bayesian models for donkey sperm quality after the evaluation of linear and combined testicular biometry indices and their relationship with age and body weight (BW). Testicular morphometry was ultrasonographically obtained from 23 donkeys (six juveniles and 17 adults), while 40 ejaculates from eight mature donkeys were analyzed for sperm output and quality assessment. Bayesian linear regression analyses were considered to build two statistical models using gel-free volume, concentration, total sperm number, motility, total motile sperm, and morphology as dependent variables. Predictive model 1 comprised the covariate of age and the independent factors testicular measurements (length, height and width), while model 2 included the covariate of age and the factors of BW, testicular volume, and gonadosomatic ratio. Although goodness-of-fit was similar, the combination of predictors in model 1 evidenced higher likelihood to predict gel-free volume (mL), concentration (×10⁶/mL), and motility (%). Alternatively, the combination of predictors in model 2 evidenced higher predictive power for total sperm number (×10⁹), morphologically normal spermatozoa (%), and total motile sperm count (×10⁹). The application of the present models may be useful to gather relevant information that could be used hereafter for assisted reproductive technologies.

The ultrastructure of human oocytes has been described only qualitatively. To offer a precise organelle spatial distribution and organelle volume during the main maturation stages, we previously conducted stereological studies on prophase-I (GV) and metaphase-I (MI) oocytes, and here we present results on metaphase-II (MII) oocytes. Five donor oocytes from different donors were processed for transmission electron microscopy, and quantification of organelle distribution was performed using point-counting stereology. Statistical tests compared the means of the relative volumes occupied by organelles among oocyte regions. The most abundant organelles were elements of the smooth endoplasmic reticulum (SER), such as SER small vesicles, SER medium vesicles, SER large vesicles and SER isolated tubules, along with mitochondria, followed by SER tubular aggregates, cortical vesicles and lysosomes. Significant differences between oocyte regions were found for lysosomes, cortical vesicles and SER large vesicles. Comparisons of MII oocytes to previous findings in GV and MI oocytes evidenced specific patterns of organelle distribution and relative volumes. This final evaluation thus enables to track organelle spatial reorganization across oocyte stages, which, in addition to gathered knowledge, may be useful to assist in improvements of stimulation protocols, in-vitro maturation media and cryopreservation techniques.

Bovine ovarian cumulus-oocyte complexes (COCs) are used for in vitro maturation and fertilization after selection by size and morphology, but their d