Sexual behavior and ejaculate characteristics in Pêga donkeys (Equus asinus) mounting estrous horse mares (Equus caballus)

Canisso, I.F.; Carvalho, G.R.; Morel, M.C.G. Davies; Guimarães, J.D.; McDonnell, S.M.

doi:10.1016/j.theriogenology.2009.07.026

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Volume 73, Issue 1 , Pages 56-63, 1 January 2010

Sexual behavior and ejaculate characteristics in Pêga donkeys (Equus asinus) mounting estrous horse mares (Equus caballus)

I.F. Canisso
- Equid Breeding Center, Department of Animal Science, Federal University of Viçosa, Viçosa, Minas Gerais, Brazil
- Corresponding author. Present address: Section of Theriogenology, Equine Research Park/Hospital for Animals, Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA. Tel.: +1 607 253 3097; fax: +1 607 253 3035.
G.R. Carvalho
- Equid Breeding Center, Department of Animal Science, Federal University of Viçosa, Viçosa, Minas Gerais, Brazil
M.C.G. Davies Morel
- Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, Ceredigion, United Kingdom
J.D. Guimarães
- Animal Reproduction Laboratory Department of Veterinary, Federal University of Viçosa, Viçosa, Minas Gerais, Brazil
S.M. McDonnell
- Equine Behavior Clinic, University of Pennsylvania School Veterinary Medicine, Kennett Square, Pennsylvania, USA

Received 13 May 2009; received in revised form 6 July 2009; accepted 17 July 2009.

Abstract

The objectives were to (i) characterize sexual behavior of donkey stallions (jacks; Equus asinus) during on-farm semen collection using estrous horse mares (mares; Equus caballus); (ii) compare behavior of young (less experienced) versus older (more experienced) jacks; (iii) determine whether semen suitable for artificial insemination (AI) could be collected using mares; and (iv) determine the suitability of using mares in field collection of semen from jacks. Six Pêga jacks (3.5 to 16 yr old), previously conditioned to breed mares, were used. Mount mares were confirmed in estrus by a teaser horse stallion (stallion) and a jack. Semen was collected with an artificial vagina, at intervals of 48 to 72h (180 collections). The mean±SD (young [3.5 yr] vs. old [14 to 16 yr]) were Flehmen response frequency, 7.4±5.8 (8.1±3.0 vs. 7.0±2.0); number of mounts without erection, 1.1±1.3 (2.1±1.4 vs. 1.2±0.4, P<0.05); latency from first exposure to mare to full erection on the ejaculatory mount, 18.3±17.7min (25.3±21.3 vs. 12.2±6.2, P<0.05); latency from erection to insertion, 5.1±3.5sec (5.3±3.8 vs. 4.8±3.2); and duration of copulation from insertion to dismount after ejaculation, 25.4±7.8sec (22.1±2.9 vs. 28.1±9.3). In all jacks, sexual behavior was generally normal, with the notable absence of open mouth behavior. Mare estrous behavior was markedly less intense than that in the presence of a stallion and usually absent. Semen characteristics were gel free volume, 47.3±28.7mL; gel volume, 71.8±54.8mL; total motility, 84.3±6.0%; progressive motility, 74.3±74.5%; sperm vigor, 3.9±0.5 (scale 1 to 5); sperm concentration, 253×10⁶ cells/mL; and total number of sperm, 10.3×10⁹ cells. Copulation duration was significantly correlated with gel free volume (r=0.9) and gel volume (r=0.7). We concluded that (i) the sexual behavior of jacks during semen collection using mares was similar to that reported for natural mating to jennies, (ii) precopulatory and copulatory behavior for the young (less experienced) jacks and older (more experienced) jacks were generally similar (except number of mounts without erection and latency to full erection); (iii) semen obtained using mares as stimulus and mount females was similar to that reported with estrous jennies; and (iv) semen collection from previously conditioned jacks, using estrous mares, was appropriate for field collection of semen.