Copulatory frequencies and intervals of two jack donkeys


Animals and sites

The trials were conducted on donkey breeding farms near CarIos Chagas (Trial 1) and Colina, Brazil (Trial 2).

 In Trial 1, Jack A (12 years-old, 280 kg, Pega) was kept at pasture for 60 days starting in February 1989, with 21 grade jennies.
 
In Trial 2, Jack B (3.5years-old, 360 kg, Brazilian breed) was pastured for 39 days during January and February 1990 with 21
Brazilian jennies that had been together for at least I.5 years before the experiment. Three jennies from Trial 1 and 10 from 
Trial 2 had a foal at foot throughout the study.

Trial-1, The jacks and jennies at pasture together were observed for 6 daylight hours on
Day 1 and Days 7-10; and 12 daylight hours on Days 2-6 and II-16 for Trial 1.

For Trial 2, they were observed for 12 daylight hours on Days I-18. For the remaining hours of these days, the jacks were separated from the jennies. 

In each trial, Jennies cycled naturally from Days 1-6. To induce oestrus, prostaglandin F2u (10 mg, intramuscularly)
was administered on Day 6 to all females not in oestrus.

The pastures were rectangular and approximately 15 hectares (* 37 acres) each. One was divided longitudinally by a
creek (Trial 1) and the other had a pond near the fence (Trial 2). Each pasture was divided into 6 sectors by imaginary lines
based on landmarks or easily observed fence marks made for this purpose. During the trials, ambient temperature varied from
26 to 42°C. Rain of less than 30 min duration occurred once in each trial.

Day 1/Trial 1- 5 ejaculatory mounts / Day 2/Trial 1- 6 ejaculatory mounts / Day 3/Trial 1- 7 ejaculatory mounts / Day 4/Trial 1- 7 ejaculatory mounts / Day 5/Trial 1- 5 ejaculatory mounts / Day 6/Trial 1- 2 ejaculatory mounts / Day 7/Trial 1- 3 ejaculatory mounts / Day 8/Trial 1- 3 ejaculatory mounts / Day 9/Trial 1- 5 ejaculatory mounts / Day 10/Trial 1- 6 ejaculatory mounts / Day 11/Trial 1- 11 ejaculatory mounts / Day 12/Trial 1- 7 ejaculatory mounts / Day 13/Trial 1- 7 ejaculatory mounts / Day 14/Trial 1- 8 ejaculatory mounts / Day 15/Trial 1- 12 ejaculatory mounts / Day 16/Trial 1- 13 ejaculatory mounts. Jack A ejaculate at mount 107 times in 16 days or average of 6.5 times a day.

Jack A Trial-1 / total ejaculatory and non-ejaculatory mounts were, respectively, 107 (33%) and 217 (67%)
Jack B Trial-2 / total ejaculatory and non-ejaculatory mounts were,133 (32%) and 286 (68%)



 The mean interval from introduction of the jack to fast mount
with ejaculation was 39.9 min. for Jack A and 25.9 min. for Jack B (P < O-05). Mean interjaculate interval was 88.4 min for Jack A and 93.3 min for Jack B. 
Details of the activity of the 2 jacks during natural and induced oestrus are given in Table 1.
Total ejaculatory and non-ejaculatory mounts were, respectively, 107 (33%) and 217 (67%) for Jack A,
and 133 (32%) and 286 (68%) for Jack B. The numbers of mounts with and without ejaculation per day ( \
and jenny for Trials 1 and 2 are shown in Fig. 3. Mating frequency was not related to time of day (P >
O-05) for either trial. Matings per jenny per ovulatory oestrus ranged from O-18 in Trials 1 and 2 together.
individual jennies did not affect the number of mounts without ejaculation or matings per day of ovulatory
oestrus (P > O-05). Of 10 jennies in anovulatory oestrus, 3 were mated, compared to 30 of 32 in ovulatory
oestrus. Also, there were fewer (P < O-05) matings per day among jennies in anovulatory oestrus (5/31)
than those in ovulatory oestrus (165/212, Jack A + Jack B). Jack A exhibited fewer mounts without
ejaculation per day of anovulatory oestrus (P < 0.01). Significant correlations were observed between
number of jennies in oestrus and number of matings per day for each jack individually and for both together (P < 0.01; r = 0.61; Jack A and Jack B) and between number of jennies showing oestrus and
different number of jennies mated. (P c 0.01; r = 0.71; Jack A and Jack B).
A gradual increase in frequency of matings and number of jennies mated per day and per number of
jennies showing oestrus per day, from Days -8 to -2 (of ovulation) was observed (P < O-05; Figs 4 & 5).
For statistical analysis, the data of both trials were combined. Frequency of matings and proportion of
jennies mated among days were compared using combined data for Days -8 to -5,4 to -3, -2 to -1 and 0 to
Day +l.
Copulatory sequences for both jacks are shown in Table 2. For Jack A, there was a difference among
jennies in the interval from approach to mount and from approach to ejaculation (P < 0.05). For Jack B,
there were differences among jennies for all measures except the interval from approach to erection and
number of thrusts (P < O-05). Except for the mean number of thrusts, Jack A demonstrated no significant
differences related to day. Jack B showed an effect related to day for all copulatory measures except
number of thrusts (P < 0.05). Throughout the trials, there was no trend toward increasing or decreasing
copulatory performance. There was no effect of time of day on any copulatory measures for either jack (P
> 0.05) except for mean number of thrusts for Jack A (5.5 in the morning, 5.9 in the afternoon; P C O-05).