Phenotypic characteristics and sexual behavior of <i>Sennar</i> Jacks (<i> Equus asinus</i>)

Abstract

This study was carried out with an objective of evaluating the breeding soundness and sexual behavior of Sennar jackasses. The physical characteristics such as the body weight, height at wither, body condition, and age of the jacks was measured and recorded. The characteristics of sexual behavior as determined by score of the sex derive, and the time taken for erection, first mount and intromission were assessed in the presence of estrous Jennies and recorded before semen collection. The body weight of the jacks range between119 and 380 kg, with mean body condition score of 7 for the breeding and 4.8 for the working jacks. The mean (±SE) of height at wither, the chest girth and the head-tail length were118±5.54 cm, 124.4±2.2 cm, 150.3±1.0 cm, respectively. The frequency of mounting without erection and with erection, time to full erection, time to ejaculation and number of ejaculatorythrust were in the order of 4.62±1.93 and 1.9±0.88, 13.45±7.02 minutes, 23.03±7.78 minutes, 4.21±0.61, respectively. Libido score was mostly (89.5%) strong during the 160 collections. The longest time to ejaculation was 58 minutes. The most frequent sexual behavior was sniffing of the vulva, flehmen, and mounting with or without erection. Flehmen responses and mounts without erection greatly varied among the jacks.The most notable difference from Abyssinian donkeys was the libido, which was relatively stronger in Sennar donkeys. However, they usually took longer time for ejaculation, which is also a common behavior among donkeys as compared to stallions. This study confirms that body characteristics of Sennar donkeys with respect to size are better than other donkey types, and semen collection and AI are feasible procedures for breed improvement in Sennar donkeys.

Keywords: Sennar donkeys, Body morphometry, Sexual behavior, Jacks, Gondar