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Pasture mating behaviour of donkeys (Equus asinus) at natural and induced oestrus

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The mating behaviour of 2 jacks, each with 21 non-pregnant jennies, was studied when the jennies were in natural oestrus and simultaneously induced oestrus. The main observations were: efficient pasture breeding at natural and induced oestrus, a territorial sociosexual structure, prolonged pre-copulatory interaction, gradual increase of mating activity up to 2 days before ovulation, a copulatory sequence similar to that of horses, vocalization of the jack as a conspicuous behaviour initiating pre-copulatory interaction, frequent heterotypical behaviour of jennies and active involvement of jennies in initiating pre-copulatory interaction.
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Printed in Great Britain
J.
Reprod.
Fert.,
Suppl.
44
(1991),
77-86 0
1991 Journals of Reproduction & Fertility Ltd
Pasture mating behaviour of donkeys (Equus minus) at
natural and induced oestrus
M. Henry, S.M. McDonnell*, L.D. Lodi and E.L. Gastalt
School of Veterinary Medicine, University of Minas Gerais Cp
567,31270
-
Belo Horizonte, Brazil; *Section
of Reproductive Studies, University of Pennsylvania, New Bolton Center, School of Veterinary Medicine,
Kennett Square, Pennsylvania 19348, USA and
?lnstituto
de Zootecnia, Post0 de Equideocultura de Colina
Cp II, 14770 Colina, Brazil
Summary.
The mating behaviour of 2 jacks, each with 21 non-pregnant jennies, was studied
when the jennies were in natural oestrus and simultaneously induced oestrus. The main
observations were: efficient pasture breeding at natural and induced oestrus, a territorial
sociosexual structure, prolonged pre-copulatory interaction, gradual increase of mating
activity up to 2 days before ovulation, a copulatory sequence similar to that of horses,
vocalization of the jack as a conspicuous behaviour initiating pre-copulatory interaction,
frequent heterotypical behaviour of jennies and active involvement of jennies in initiating
pre-copulatory interaction.
Introdktion
Numerous authors have described sociosexual behaviour of domestic horses (Collery, 1969; Pickett et al.,
1970; Collery, 1974; Asa et al., 1979; Bristol, 1982; Ginther, 1983; McDonnell, 1986; Bristol, 1987), feral
horses (Feist
&
McCullough, 1975, 1976; Klingel, 1982; Keiper
&
Houpt,
1984),
Przewalski’s horse
(Kolter
&
Zimmermann,
1988).
and plains, mountain and Grevy’s zebras (Klingel, 1975). However,
studies on social organization and reproductive behaviour of donkeys are few. A study of wild African and
Asiatic asses revealed a territorial, rather than harem, type of social organization. These jacks defend their
boundaries against neighbouring territorial males only under specific conditio& such as when a jenny is
in oestrus (Klingel, 1977). In a 2-year study of domestic jack semen collection (M. Henry, M.M.F.
Oliveira, C. Meira & E.L. Gastal, unpublished observations), the mean time from approach to ejaculation
of jacks running free with an oestrous jenny varied from 12-26 min. During this time, prolonged Flehmen
episodes, mounts without erection, partial drop of the penis, rapid and sudden withdrawal from the female
and grazing were observed. In that study, unexplainable, repeated failure to collect semen from some
individual jacks was noted. The rather long pre-copulatory interval in domestic jacks and the
dSiculty
in
collecting semen, compared with horses was noted also by Nishikawa (1959) and Kreuchauf (1984).
These findings, together with subject observations of slow sexual response of jacks, prompted
questions concerning their reproductive management. This experiment was conducted to describe
reproductive behaviour of domestic donkeys. To permit comparison with horses, our project design
included pasture breeding of donkeys under simultaneously induced oestrous conditions similar to those
described for horses by Bristol (1982, 1987).
Materials and Methods
Animalsandstudysites
The trials were conducted on donkey bneding farms near CarIos Chagas (Trial 1) and
Coh,
Brazil
flriai
2). In Trial
1,
Jack A (IZyears-old, 280 kg, Pega) was kept at pastu~. 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 fmm Trial 1 and 10 from
78 M. Henry et al.
Trial 2 had a foal at foot throughout the study. 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
remahing hours of these days, the jacks were
separated
from the jennies. On Days 17-60
in Trial
1
and Days 19-39 in Trial 2, the animals remained at
pasture
continuously.
In each trial, Jennies cycled naturally from Days
Id.
To induce oestrus,
prostaglandin
F2u (10 mg, intramuscularly
[i.m.])
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.
Observations
Two observers were stationed at elevated sites on opposite sides of the pasture (Trial 1) or at 3 different elevated sites
within the pasture (Trial 2). Primary focus was on the jack and secondary focus on the jennies. The observers recorded all
specific interactive responses between adult donkeys (i.e. olfactory, aggression, vocalization. mounting, insertion, thrusting
and ejaculation for the jack, approaching, posturing, jawing, ear and tail position for the jennies), and maintenance behaviours
(grazing,
&.ting,
drinking, elimination, grooming) on a time base using a microcomputer event recorder, audio recorder and
written notation. Ejaculation was identified by tail flagging and seminal reflux. The location of each animal relative to the
sectors was recorded at 2-h intervals. At 15-min intervals, the jennies close to the jack were identified as part of the ‘proximal
group’ and were considered to be sexually active if they stayed in the vicinity of the jack and postured to the jack at least once
during the 15min interval.
Observers recorded their subjective appraisal of each
jenny’s
oestrous or dioestrous condition each day based on jawing,
ear pinning and posturing to the jack.
Semen collection .
Attempts were made to collect semen from the jacks by artificial vagina on the day before the start of the trial and every
other day (alternating morning and afternoon) during natural and induced oesuus. Semen was also collected on Day 39 of Trial
2. All semen samples were evaluated as described by
Ketmey
et
al. (1983).
Ovarian
activiry
Ovarian activity was monitored by palpation per rectum
every
day during oestrus and every third day during dioestrus.
For Trial 2, follicular growth was monitored by ultrasound. At least once a week, the jennies were bled by jugular
venepuncture. Plasma was stored at -2o’C until progesterone analysis was performed by radioimunnossay (Vermeulen
&
Verdonck, 1976). The sensitivity of the assay was 0.5 @ml and the
intra-
and inter-assay coefficients of variation were 3.6
and 7.38, respectively. Palpation per rectum, collection of blood samples and ulttasonography were performed during the
evening of each observation day.
Statistical analysis
Proportional and quantitative data were evaluated by Chi squared tests and analysis of variance procedures, respectively.
Pierson correlation techniques were used to evaluate associations.
General breeding results
During Trials 1 and
2,20
(95%) and 21 (100%) of the jennies, respectively,
came into
oestms
(Fig. 1)
and 14 (67%) and 18 (85%) ovulated. The mean
(k
s.d.) length of ovulatory oestrus was 6 days
(*
2.1);
start
Of
oestNs
to
ovulation
was
5.4
days
(&
1.7)
and ovulation to end of
oestnts
was
0.7
(*
0.7)
days
(n
=
20). Length of anovulatory oestrus was 2.6 (k 2.2) days (n
=
12). One split ovulatory oestrus was
observed. One of the jennies showing anovulatory
oestt-us
ovulated during a subsequent oestrus that
started 8 days later, and 1 was cycling but neither a large follicle nor ovulation was detected. The
remaining jennies were not cycling, as indicated by the progesterone assay results (<
1
rig/ml
p]aStTKi).
Plasma progesterone concentrations (> 3
@ml)
indicated that the detected ovulations resulted in active
corpora lutea.
Pregnancy was diagnosed for all jennies by a Single palpation per rectum at least
40
days after
ovulation. .Of the 14 jennies that ovulated during Trial
1,
11
(78%) were diagnosed as pregnant after the
Pasture breeding behaviour of donkeys
79
.c
8
‘C
5
6
.-
5
'4
z"
-2
0
12 345678
9 lo
11 12 13 14 15 16 17 18
Days
Fig. 1.
Number of jennies showing oestrus per day during Trials 1
(0)
and 2
(W).
first cycle and 3 (22%) after the second cycle. For Trial 2, ultrasonography of the
uterus
began on Day 10
after ovulation. An embryo was detected by Day 12 after ovulation in 11/16 (69%) jennies mated during
the first cycle. Two jennies were not mated during the first ovulatory
oestrus.
All but 1 jenny became
pregnant within 2 cycles. Early embryonic death was detected in 2 jennies during the first cycle and in
1
in
the second cycle.
Sexual behaviour
Pre-copulatory interaction.
In both trials, arrival of the jack at the paddock each morning evoked
vocalization and vigorous general interaction with all jennies, followed by a more thorough individual
teasing of one of the jennies. Teasing behaviour included naso-nasal contact, nibbling the head, neck, knee,
and flank and sniffing parts of the body, mostly the perineal area. Teasing generally concluded with 1 or
more mounts without erection. As the jack interacted with an individual jenny, other jennies
(predominately those in oestrus) gathered in the vicinity. After each mount, the jacks grazed or rested for
22
(*
14.2) min before the next vocalization or period of teasing. During the rest period, the sexually
active jennies remained nearby, but if they approached the male they were generally rebuffed by
threatening or kicking behaviour.
.Spontaneous vocalization by the male, and less frequently by a female in oestrus, was the signal for a
period of pre-copulatory interaction. Occasionally, the approach of a jenny in oestrus was the stimulus for
the jack to vocalize after his rest. Immediately after the jack’s vocalization, the jennies in oestrus
approached the male. Intense teasing usually followed. Vocalization by jennies was more frequent when
they were in induced, as opposed to spontaneous, oestrus. During Trial 2, 12 of 21 jennies vocalized at
least once; 78% of the total number of vocalizations came from jennies in oestrus.
The pattern of vocalization, general and individual teasing and retiring of the male was repeated
several times. Vocalization appeared to attract oestrous jennies to the vicinity. Occasionally, intense teasing
of an individual occurred, usually not culminating in mating with that particular individual. The long,
intermittent periods of sexual stimulation ended with the jack achieving an erection and mating with a
jenny, not necessarily the closest one. Erection and copulation occurred suddenly at the end of an
intermittent ‘rest’ period.
80
M. Henry et al.
Proximal group and sexually active jennies. A group of jennies stayed
close.
to the jack and expressed
both heterotypical and homotypical sexual behaviour. Heterotypical behaviour included mounting,
herding/chasing, teasing and Flehmen response, which are infrequently observed in mares. At least one
incident of heterotypical behaviour was exhibited by 37 of the 42 (88%) jennies. For Trials 1 and
2
combined, 169 mounts, 286 herding/chasing episodes, 62 teasing episodes and 99 Flehrnen responses
were observed. Mounting by jennies was more frequent during the second part of each trial when more
jennies were showing ocstms. All mounts during Trial 1 and 52/63 (82%) in Trial 2 involved one jenny
mounting another. During Trial 2,1 jenny mounted the jack 10 times and another jenny mounted the jack
once. Also during Trial 2, 46 of the 52 (88%) mounts involved jennies that were both in oestrus. On 3
occasions, only the jenny that mounted was in oestrus, on 2 occasions only the mounted jenny was in
ocstrus, and on 1 occasion, neither was in oestrus. Most heterotypical herding/chasing episodes occurred
during intense mutual teasing, increasing in frequency when the jack was about to mate a jenny.
Occasionally one jenny prevented the jack from mating another by kicking, biting, striking and pushing
the jack off the jenny.
The proximal group was comprised mostly of jennies in oestrus. During natural oestrus in both
tiais,
there was a clear separation of the proximal group from the remainder. During induced oestrus, the
division was less distinct. The remaining jennies continued to graze independently in all sectors of the
pasture. All pasture sectors were used by the jennies in a frequency varying from 14% for 1 sector to 75%
for another in Trial 1 and from
7-49%
in Trial 2.
From Day -8 to Day -3 before ovulation, individual jennies showed an increase in the time spent in the
proximal and sexually active groups, as well as an increase in the number of approaches to the jack (Fig.
2). There was a significant difference among days during the periovulatory period (P c OQOl) in the
number of approaches to the jack and in the sexually active group. Mean number of approaches by the
jennies and by the jack from Day -8 to
+l
were, respectively, 24.7 (3
l-7)
and 6.3 (9.3) (P < O-001)
per
day
and per jenny.
During induced oestrus in both trials, strong relationships were formed between certain jennies who
often approached the jack in pairs even if 1 of them was not in oestrus. Three such pairs were identified in
Trial 1, and 6 in Trial 2; possibly because jennies in Trial 2 were pastured together before the experiment.
With the increased number of oestrous jennies in the sexually active group during induced
~eshus,
the
number of jennies in the proximal group also increased.
-6 -7 -6 -5 -4 -3 -2 -1
0
1
Peri-ovulatory period (days)
Fig.
2. Frequency (%) in the proximal (m) and sexually active (*) groups and percentage of the total
number of approaches to the jack (
A
) during the peri-ovulatory period. Day 0 = day of ovulation.
Pasture breeding behaviour
of
donkeys
81
There was no correlation
(P
> O-05) between number of approaches and number of matings per day of
oestrus per jenny; or between the presence of a jenny in the proximal group per day of oestrus and number
of matings. The number of matings per jenny was correlated (r = 0.43,
P
< O-01) with the frequency of her
presence in the sexually active group.
Compared with horse mares, jennies played an active role in mating. The first sign indicative of
impending sexual receptivity was increased time in the proximal group: some joined this group just a few
hours before showing the first overt signs of oestrus. Some jennies displayed prolonged periods of
alternating sexual receptivity and rejection of the jack. During early oestrus, jennies frequently kicked at
the jacks approach. Kicking gradually decreased during the following days.
Copulatory frequencies and intervals.
The mean interval from introduction of the jack to fast mount
with ejaculation was 39.9
(&
30.4) mm for Jack A and 25.9
(dz
17.8) min for Jack B
(P
<
O-05). Mean
inter-
ejaculatory interval was 88.4
(&
71.5) min for Jack A and 93.3
(2
54.5) min for Jack B
(P
<
O-05). 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
,
1
2 3 4 5 6 7
8 9 101112131415~
Trial
1
30
25
20
Trial 2
1
2 3 4 5 6 7
8 9101112131415161718
o-
Day
50
00
,,.,,..,,......
abcdefghij
klmnopqrst-h
1
2
3
4 5
6
78
Jenny
9101112,314,5161716,g202,
Fig. 3.
Number of mounts with (m) and without (0) ejaculation by Day and Jenny in Trials 1 and 2.
82 M. Henry et al.
Table 1.
Activity of the jacks and mean number of jennies in natural and induced
O~S~IUS
Natural oestrus Induced oestrus
Mean number
per day
Jack A
mean
f
s.d.
Jack B
mean
f
s.d. Jack A
mean
f
s.d. Jack B
mean
f
s.d.
Jennies in oestrus
38
3~
0.8 5.4
f
0.5
8.5 +
0.8 9.5 rt
2.3
Mount without erection 14.8
+
2.8
11.4f2.8
16.2
+4.9
16.8
f
7.9
Ejaculatory mounts
5.6 5
2.3
6.2
zk
1.3
9.5
+
1.6 9.1 iz 1.2
Jennies bred
3-o+
1.4
3.0
f
1.2
4.8 +
1.8
4.6 +0.8
Masturbations
1.4+
1.1
3.2
&
1.3 2.0
tt
0.6
3.8
+_
1.3
Natural oestrus
= Days 2-6; induced oestrus
=
Days 11-16. There was no significant difference in
these measures (P > 0.05) between natural and induced oestrus for both jacks and between jacks for
natural and induced oestrus.
Table
2. Copulatory sequence of 2 jacks mating 21 jennies each in a free-range breeding
management system
Measures
(set)
+
Jack ‘A’ Jack ‘B’
Mean s.d.
n
Mean s.d.
n
Approach-erection* 0.5 1.7 98
446
101
Approach-mount* 13 19 98
32 49
104
Approach-ejaculation*
32 20
98 51
50
83
Mount-ejaculation 19 5.5 98 19 5
99
Mount-dismount* 25 598
30
12 121
Number of thrusts 5.5 1.4 98
4.9
1.5 110
n = number of observations.
*Significant difference between jacks, P < OGOl.
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).
Masturbation and spontaneous erection. This behaviour was observed during both trials. Incidences of
masturbation and spontaneous erection, respectively, were 24 and 8 (Jack A) and 56 and 24 (Jack B)
60
50
P
40
u
h
I&
30
.E
iij
;
20
B
10
0
Pasture breeding behaviour of donkeys
-a
-7 -6 -5 -4 -3
Day
I
-2
L
-1
0
t
Fig. 4. Number of matings per day (0) and per jenny in oestrus (x 10)
(U)
during the
peri-
ovulatory period. Day 0 = day of ovulation.
90
a0
70
60
I$
50
0
E
$
40
$
30
20
10
0
Day
-3
la
i
0
1
Fig
;.
!
5.
Percentage of jennies mated per day (Cl) and per number of jennies showing oestrus per
day (B). Day 0 = day of ovulation.
distributed over the duration of the trials with no discernible pattern.
Territorial social structure
-
‘,
observed in horses (McDonnell, 1986); were not observed in the present study. Infrequently, prolonged
chasing of an individual jenny (almost to exhaustion) was observed.
Jack A and B appeared to have
a
preferred area of pasture where they rolled; grazed, rested and
84 M. Henry et al.
Table 3.
Seminal characteristics of 2 jacks, before, during and at the end of a free-range breeding
management system
Day Period of
collection
Sperm-motility
total/progressive
@)
Sperm
vigour
(l-5)
Total no. of
spermatozoa
(x109)’
Jack ‘A
1
2,3,
15*
7
Jack ‘B’
1
7, 10,
$8*
6, 13, 15,
17*
39
morning
95f90
512.5
afternoon 65145
42.9 (2.2)
morning 85flO
46.2
morning 90185 519.3
afternoon 80170 3.5 1.7
(0.9)
morning
85/70 2.5
3.1
(2.1)
morning
85/80
5
4.8
* The results are expressed as the mean for the days indicated
(&
s.d.).
groomed, and where most matings occurred. Jacks A and B were within the range of 2 bordering sectors
of the pasture for, respectively, 73 and 65% of the 2-h interval recording times. Notwithstanding the
absence of harem behaviour, the jacks were alone in a given sector only 10% (Jack A) and 1% (Jack B) of
the time.
Quality of semen
Semen was collected from Jack A in the morning on Days 1 and 7 and in the afternoon on Days
2,4,7
and 15; and from Jack B in the morning on Days
1,6,13,15,17
and 39 and in the afternoon on Days 7,10
and 18. As shown in Table 3, all ejaculates yielded at least
1X109
spermatozoa. Morphologies were
evaluated on 4 samples from Jack A and 9 samples from Jack B. The mean (+
s.d.)
percentage of
abnormal heads, middle pieces and tails were, respectively, 2.6
(i
1.3), 5.1
(&
1.8) and
l-9
(It 0.9) for Jack
A and
12.9
(&
8.3),
12.1
(i
7.4),
2.3
(2 2.3) for Jack B.
Diiussion
Although the experiment was not designed to evaluate the breeding potential of donkeys, the findings
indicate that donkeys mate efficiently at pasture. All but 2 jennies showing ovulatory oestrus were mated
at least once. Of the 2 that were not mated, one showed overt oestrous behaviour for only 2 days and did
not approach the jack frequently, and the other had foaled recently and kicked the jack vigorously at the
beginning of her period of sexual receptivity. The jack rejected her later when she was in
oestrus.
First-
cycle pregnancy rate was 78% for Jack A (more than 40 days after ovulation) and 69% for Jack B (Day 12
after ovulation), which decreased to 56% with 2 early pregnancy losses. The final pregnancy rates at 40
days after ovulation were 100% and 89% for Jack A and B, respectively. This indicates, as semen quality
suggested at each collection, that high frequency of mating was not detrimental to fertility. Similar findings
were reported for mares mated at pasture under simiiar conditions (Bristol, 1982, 1987) and under farm
and feral conditions (Collery, 1974).
The observations of this study indicate that donkeys have a territorial, non-harem type of sociosexual
organization. The jacks spent most time and did most mating in two contiguous sectors. Jennies moved
freely around all sectors without any apparent concern or interference by the male. On one occasion,
during Trial 1, a second jack approached the fence; the original jack confronted the intruding male but did
not attempt to herd the jennies together.
Pasture breeding behaviour
of
donkeys
85
Another prominent featute was the sexually active group, which showed intense heterotypical and
homotypical behaviour. Gestrous responses appeared similar to those described by Clayton et al. (1981)
for domestic jennies, and by Trumler
(1958)
for zebras r&d donkeys&. jawing, ears depressed
aga+t
extended neck, tail slightly~ed.~urinati,onar~ posturing
for+.
jack*+ proximal group
,has,been
observed
‘m
pasture-bred maresi(Asa et
d:,
1979;
Bristol,
4982),
but mare&how much less heterotypical
behaviour. In contrast to Klingel’s
(i%9,
1975) studies of wild horses, during which mares assumed the
oestrous stance only when the stallion approached and mounted, jennies in this study exhibited
spontaneous external signs of oestrus and approached the jack frequently. There was a significant
difference between jennies in the number of approaches to the jack and frequency in the proximal and
sexually active groups. Cows in oestrus form a sexually active group, differing from jennies in that they
were extremely mobile and not restricted to the proximity of the male (Blockey, 1978). Another similarity
between cows and jennies was the high frequency of heterotypical behaviour, particularly mounting, a
behaviour rarely observed in mares. Heterotypically active jennies interfered with mating and, as described
in mares (Ginther et al., 1983), their efforts were directed toward the jennies before mounting and toward
the jack during mating.
Vocalization was more pronounced in donkeys than has been reported for horses and appeared to play
a role in initiating pm-copulatory interaction. The jacks
appear4
to disregard vocalization between dam
and foal. Vocalization was not noted as a prominent aspect of reproductive behaviour among wild African
and Asiatic asses (Klingel, 1977). In wild plains zebras
(Equs
quagga), a contact call that serves to keep
the herd members together was noted (Klingel, 1967). Feist & McCullough (1976) suggest that whinnying
in feral horses may be a prelude to aggressive interactions rather than cohesion.
Pasture breeding performance and copulatory behaviour were very efficient for both jacks, although’
their performance during attempts to collect semen was slow and inconsistent, as is observed in hand-
mated or intensely managed jacks. Mounts without erection, as seen in feral horses (Heist & McCullough,
1976), pmceded ejaculatory mounts.
Although the number of different jennies mated per day increased with the number of jennies in
oestms, the jacks still continued to mate individuals up to 6 times per day when the number of jennies in
oestrus per day was at its highest. Preference to mate certain individuals has been suggested in other
studies (Bristol, 1982;
Asa
e&al.,
1979) and was observed during Trial 2, when the jack persisted in
attempting to mate a particular jenny that did not promptly accept mounting. A high number of matings of
individual jennies (up to 18) did not appear to be due to preference of the male exclusively: jennies also
appeared to influence the number of times they were mated. There was a positive correlation between
participation in the sexually active group and number of matings per day per jenny. The number of
matings per day of anovulatory oestrus was less than for ovulatory oestrus and mating activity increased
graduahy up to the 2 days before the ovulation. Independent of the participation of the female, the jack
seemed to determine the exact time of mating and the target jenny. This had been reported in stallions
(Rhngel,
1969;
Bristol, 1982).
The copulatory behaviour sequence appeared similar to that of stallions. The mean number of thrusts
for stallions was 7 (Asa et al., 1979) compared with 5 in these jacks. Copulation time was about 30 set for
a stallion breeding at pasture (S.M. McDonnell & F. Bristol, unpublished observations) and varied from 25
to 30
set for stallions in a semen collection programme (McDonnell, 1986; Pickett et al., 1970). compared
with 25 and 30 set found for the jacks in this study.
,.-
We thank A. Vieira de Axemdo Coutinho, veterinarian and farmer, for partial financial
support
and for
providing the animals and facilities used in Trial 1; H. M. Piedade, veterinary student, for substantial
assistance during Trial 2 and M. Armstrong for assistance with preparation of the manuscript. This work
was supported partly by grants from the National Research Council
-
CNPq
-
Brazil.
86 M. Henry et al.
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... The results of the present study revealed several ovarian and uterine characteristics that appear to be specific for Caribbean jennies and other features similar to small-frame donkey breeds. Characteristics such as length of the estrous cycle, follicle diameter at ovulation, and incidence of multiple ovulations have been reported to be influenced by the breed in donkeys [5,17,19,20,[29][30][31][32][33] and horses [11,[34][35][36]. The duration of the IOI in Caribbean jennies appeared to be slightly shorter (22.9 days; range: 20-25 days) than observed in other donkey breeds, such as Mammoth, Catalonian, Pega, Standard, Mexican Burro, and crossbreed donkeys (23.3-24.9 ...
... The authors noted that the second-largest follicle never grew to >20 mm in diameter in Mexican Burro jennies [18], which was similar to what was observed in 93% of the cycles in Caribbean jennies; this might be a characteristic of these donkey breeds and may explain the lack of multiple ovulations. Two to three follicular waves have been described in other larger donkey breeds, such as Pega [31] and Dezhou Black jennies [17]. Interestingly, the three follicular wave patterns observed in Dezhou Black jennies [17] occurred in autumn. ...
... In contrast, two follicular waves, similar to those of the Caribbean jennies in the present study, were observed during the rest of the year in Dezhou Black jennies. The authors suggested that the three-waves pattern in Dezhou Black jennies was associated with changes in FSH surges observed during autumn [17], which has also been described in mares [56] and might be associated with some degree of seasonality in donkey species, although the reproductive activity of jennies has been shown to be less affected by seasons than that of mares [17,31,33]. It is worth noting that the present study was performed during the breeding season in the northern hemisphere. ...
Article
Full-text available
Eight non-bred, non-pregnant, regularly cycling Caribbean jennies were examined daily via transrectal ultrasound to define the ovarian and uterine dynamics during four consecutive estrous cycles. Blood samples were collected every other day for progesterone analysis. The mean (±SD) overall inter-ovulatory interval across all donkeys and cycles was 22.93 ± 1.99 days. The maximum follicular diameter was 34.6 ± 2.9 mm. A two-wave pattern was evident in 97% (30/31) of the cycles. The emergence of the future dominant follicle and the largest subordinate follicle of the major primary wave coincided on Day 5.7 ± 3.6 post-ovulation, whereas the secondary wave emerged on Day 19.8 ± 2.9 during estrus of the previous cycle or early diestrus. The secondary wave was often minor (93%, 28/30 cycles). Follicular deviation occurred 8.2 ± 1.4 days before the subsequent ovulation. Luteal volume increased for the first four days after ovulation and reached a maximum volume of 8.5 ± 2.7 mm3 at Day 5.4 ± 0.4, before gradually regressing after Day 15. Serum progesterone concentration increased from Day 1 after ovulation, peaking at 27.0 ± 9.6 ng/mL between 7 and 10 days after ovulation. Progesterone concentration dropped precipitously around Day 15 after ovulation and was below 2 ng/mL around Day 17 ± 2. A day effect (p < 0.0001) was observed for corpus luteum’s volume, progesterone concentration, and uterine tone, but not for endometrial edema (p > 0.05). This study helps to clarify and define normal estrous characteristics of jennies in the Eastern Caribbean.
... Therefore, they are likely less acclimated to temperate environments than horses, probably due to their descent from African wild asses, which were adapted to semi-arid climates. (Aganga and Tsopito, 1998;Canacoo and Avornyo, 1998;Couto et al., 2016;Lamoot et al., 2005aLamoot et al., , 2005bMueller et al., 1998;Proops et al., 2019;Regan et al., 2014;Zakari et al., 2018Zakari et al., , 2016) Temperament 2 (French, 1993;Gonzalez-De Cara et al., 2017) Social behaviour Intra-specific 6 (Brément et al., 2019;Hoffmann, 1983;McCool et al., 1981;Murray et al., 2013;Normando et al., 2017;Rudman, 1998) Sexual behaviour 11 (Carluccio et al., 2013;Clayton et al., 1981;Contri et al., 2014;Gastal et al., 1996;Henry et al., 1991Henry et al., , 1987Quaresma et al., 2015;Quartuccio et al., 2011;Rota et al., 2018;Taberner et al., 2008;Vandeplassche et al., 1981) Mother-foal bond 6 (D' Alessandro et al., 2011Alessandro et al., , 2007Alessandro et al., , 2005French, 1998;Houpt and Antczak, 1998 Minero et al., 2016;Pritchard et al., 2006Pritchard et al., , 2005Raw et al., 2020;Regan et al., 2016Regan et al., , 2015Sommerville et al., 2018;van Dierendonck et al., 2020) of the animal towards humans, other individuals or the environment, was investigated by two studies within those included in this review (French, 1993;Gonzalez-De Cara et al., 2017). Its assessment can be useful support when selecting animals for AAIs and other activities in which the animal's attitude towards humans is crucial. ...
... As previously reported, in certain conditions donkey's sociosexual organisation is territorial, with stallions holding territory and breeding with jennies passing through or residing there (Henry et al., 1991;Quartuccio et al., 2011;Rota et al., 2018;Taberner et al., 2008). This aspect is mirrored by some peculiarities of donkeys' sexual behaviour. ...
... A high frequency of homotypical and heterotypical behaviour (i.e. herding/chasing, sniffing, teasing, the flehmen response, and mounting in particular) is described in receptive jennies along with a prolonged pre-copulatory interaction during both natural and induced oestrus (i.e. the period of the sexual cycle when a mare is receptive to the stallion (Clayton et al., 1981;Henry et al., 1991). In males, vocalization seems to play a key role in initiating the pre-copulatory interaction and attracting oestrus jennies to the vicinity, as reported by Gastal et al. (1996). ...
Article
Despite their diffusion worldwide, many aspects of donkeys’ behaviour and cognitive abilities are still poorly understood and overshadowed by a corpus of commonplaces. The possibility of better knowing this species is of key relevance for its wellbeing and to establish a good human-donkey relationship. This review aims to investigate scientific literature on donkey behaviour and cognition, along with the behavioural tests that have been used so far to explore these topics. Searches of Web of Science (WoS) Core Collection, Scielo and Medline (through the WoS platform) and Google Scholar performed prior to March 2020 resulted in 75 records dealing with the question outlined in the present review. This research allowed us to delineate a qualitative synthesis of the studies’ characteristics, as well as a narrative summary of the topics covered by the investigated scientific literature, and to identify the behavioural tests used for donkeys. The hope is that a deeper knowledge of this species in regard to of the abovementioned aspects would allow donkeys to benefit from an improvement of human respect for their welfare.
... Donkeys' sexual behavior has been well studied under pasture breeding and semen collection using jennies and mares [13][14][15][16] . However, it has not been studied under an intensive semen collection schedule such as that required for obtaining the act -DSO. ...
... There were no effects of jacks or collection order for any of the behavioral parameters assessed herein ( Fig. 1 ). Dezhou jacks enrolled in the study displayed typical precopulatory behavior (e.g., vocalization, sniffing, and biting the jenny's perineal area, inguinal, hindlegs, and ventral abdomen) with the jenny in estrus as previously described by other authors during semen collection or natural mating [13][14][15][16] . ...
... Donkeys are known to be particularly sensitive to environmental interference during semen collection or natural mating [16] ; this particularity helps to explain in part the lack of variation across jacks and days hereby as the semen collections were conducted in a breeding shed and external interferences were minimized to avoid confounding factors. Another study also minimized the external interferences to avoid variations [19] , and some authors even proposed using ground collection [13] as an approach to prevent variations across collections. ...
Article
This study aimed to assess the sexual behavior of jacks mounting jennies in estrus and determine the daily sperm output (DSO) and spermatogenic efficiency using two equations to calculate testicular volume (TV). Eight sexually rested mature jacks, aging 5 to 10 years old, had semen collected once a day for 10 consecutive days using jennies in good standing estrus for mounting. Sexual behavior and semen parameters were assessed during each collection. Testicular measurements of height, width, and length were taken immediately before the first semen collection, and these measurements were used to calculate TV. After that, the TV was used to predict the DSO. The average total sperm number (TSN) obtained on days 8 to 10 was deemed the actual DSO. Differences in the predicted vs. the actual DSO were used to calculate the spermatogenic efficiency. In addition, the actual DSO was also used to calculate the number of inseminating doses a jack could produce for both on- and off-site breeding. Jack's sexual behavior and sperm motility did not vary across collection days. Sperm concentration and TSN reduced over time (p < 0.05). The actual DSO was 9.1 ± 4.1 billion, and the predicted DSO varied from 4.7 to 18 billion. Spermatogenic efficiency varied from 50 to 150% based on jack and the equation used to calculate TV. The number of inseminating doses ranged from 15 to 47 at 300-500 million progressively motile sperm (pms)/dose for on-site breeding. In contrast, the number of breeding doses with cooled-shipped semen (1 billion pms/dose) varied from 4 to 14 doses across donkeys. In conclusion, sexual behavior was not affected by daily semen collections. Sexual rest did not affect sperm motility. The predicted DSO varied with the equation used to determiHne TV. Clinically normal donkeys have high spermatogenic efficiency, which confirms previous histology reports.
... Observations regarding reproductive behavior of feral and domestic horses indicate that stallions at hand-breed systems have lower rates of sexual vigor and fertility and higher rates of sexual behavior dysfunction compared to equids breeding freely (McDonnell, 2000). There are reports on stallions and donkeys at pasture breeding females every 1 or 2 h during the day and at night with excellent sustained fertility (Bristol, 1982;Henry et al., 1991;Steinbjörnsson and Kristjansson, 1999), whereas for most hand-breed stallions, libido and fertility decrease with breeding schedules of more than once or twice per day (McDonnell, 2000). ...
... Greater mating activity has been reported for stallions and donkeys breeding at pasture (Bristol, 1982;Henry et al., 1991;Steinbjörnsson and Kristjansson, 1999), while those submitted to a hand-breed system could have their libido and fertility decreased when mounts are accomplished more frequently than once or twice a day (McDonnell, 2000). In the first year when the daily observations lasted about 8.1 h, the average number of matings/day was 1.2. ...
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Full-text available
Aspects related to social organization and its effects on the reproductive behavior of domestic stallions breeding under free range management systems have not been studied. This study was carried out with the following objectives: to identify the social units established between Brazilian Pony Breed stallions and mares; to verify the effect of the stallion in harem composition and mating activity; and to verify nocturnal sexual activity. This study was carried out during two breeding seasons. In the first year animals were observed for 12 days (8.1 h/day). In the second year, another group was observed in three periods with an average daily duration of 9.6 hours. Stallions ranging in age from 3 to more than 12 years and a group of mares ranging in age from 3 to 20 years were used. Two social units were identified: harem and bachelor group. Three-year-old stallions did not form a harem. Hierarchic relationships among stallions and inside harems were established. Dominance, fight ability, aggressive behavior and age of stallions seem to influence size and harems maintenance. The total observed matings in Years I and II was 28 and 134, respectively. Mares were mated on average 1.9 times and the average number of daily mating was 1.2. The average number of receptive mares and matings per day was 8.5 and 1.1, respectively. The average copulation time was 38.4 and 37 sec in Years I and II, and the average daily interval between matings was 79.8 and 104.1 min, respectively. Considering the three observation periods in Year II, the mares were mated on average 2.2 times. The average number of daily matings was 2.1. The average number of receptive and mated mares per day was 20.7 and 1.8, respectively. In the two years nocturnal sexual activity was verified. The general pregnancy rate was 79.4% in the first and 72.2% in the second year.
... asinus), which evolved in desert environments (Moehlman, 1998). Lying to roll is a frequent behavior in adult donkeys, related to heat stress control and mating (Henry, McDonnell, Lodi, & Gastalt, 1991;Regan, Hockenehull, Pritchard, Watermanpearson, & Whay, 2014). In a previous study (Luz, Maia, & Puoli-Filho, 2022) we observed that mules roll frequently more than horses under free-range conditions in specific rolling bowls, expressing relevant differences in the behavior pattern. ...
Article
Rolling is a natural behavior of equids that is beneficial to their well-being. However, more intensive domestic environments offer fewer opportunities for animals to roll, neglecting its importance. We believe that the inclusion of recreational areas for animals, containing substrates and conditions that encourage the occurrence of natural behaviors, is essential to promote their well-being. Therefore, we evaluated the preference of horses (Equus cabal-lus; n = 8) and mules (E. asinus x E. caballus; n = 8) for different rolling substrates (sand, grass, manure), and the influence of this behavior on thermoregulation after exercise. Horses rolled preferentially on grass, whereas mules preferred sand, both of which were cooler substrates when compared to manure. In addition, the temperature of the animals significantly reduced after rolling. Thus, horses and mules must roll for thermoregulation after exercise, choosing cooler and more efficient sub-strates for heat dissipation. The differences in preferences between mules and horses showed particularities between the equine species and its hybrid, which is important for management that is focused more on the individual animal.
... Donkeys in temperate regions of China are seasonal estrus animals, with a gestation period of nearly a year. Spring (late March to early June) is the peak estrus season for donkeys and the season with the highest mating success rate (Henry et al., 1991). Despite the similar climate between spring and autumn, the distribution of donkey foal births is uneven throughout the year, and fertility peaks between March and May, during which 61.7% of the total births occur. ...
... The social structure of donkeys is composed of a territorial-based system [20][21][22], with complex hierarchies within groups [23]. The only permanent bond among donkey social structures is between jennies and their foals [24]. ...
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Article
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African and Asiatic Wild Asses (Equus africanus and E. hemionus) live in unstable groups or herds of variable composition. Some of the adult stallions are territorial in large territories in which they tolerate other ♂ ♂. The territorial ♂ ♂ are dominant over all their conspecifics. Die soziale Organisation des afrikanischen Wildesels (Equus africanus) wurde während, die des asiatischen Halbesels (E. hemionus) für kurze Zeit außerhalb der Fortpflanzungsperiode im Freiland untersucht. Bei beiden Arten konnte Territorialität nachgewiesen werden; ihre Sozialsysteme entsprechen dem des Grevy-Zebras (E. grevyi). Die Territorien sind groß; sie liegen beim Wildesel in der Größenordnung von 20 km2, beim Halbesel dürften sie noch größer sein. Die Mitglieder beider Arten leben in veränderlichen Gruppen unterschiedlicher Zusammensetzung. Für das Vorkommen dauerhafter Bindungen zwischen erwachsenen Tieren gab es keine Hinweise.
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Thesis (M. Agr. Sc.)--University College Dublin, 1983. Appendix.
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