Asinara male donkey (Equus africanus asinus var. Albina) and stallion (Equus ferus caballus) reproductive characteristics: Correlations between testicular blood supply and sperm production

The Asinara donkey is a rare small albino variety of feral donkey listed as "critical" by the Food and Agriculture Organization of the United Nations (FAO) and by the Domestic Animal Diversity Information System (DAD-IS) in 2022. The objectives of the present study were to evaluate the reproductive characteristics of healthy male Asinara donkeys through andrological evaluation and testicular echo-color-Doppler examination to assess correlations between testicular blood supply and sperm production and to compare it with horse reproductive characteristics. Eight healthy donkeys and stallions were subjected to semen collection and evaluation, ultrasound and Doppler evaluation of the testicles and serum testosterone determination. The testosterone concentrations in donkeys were 1.42 ± 0.69 ng/ml while in horses were 1.90 ± 0.63 ng/ml within the normal values reported in these species. Horses had greater mean and total testicular volume, semen gel-free volume, and total sperm number than donkeys (P