Pearsons’ correlation. Differences in nominal variables, for example, the mating quality score, were analysed using the x
2
-test. Where differences between different boar teams were demonstrated, data were also analysed for each team separately. Differences
between animals in ordinal data, for example, TTFM and MA duration of boars, were analysed using ANOVA incorporating effect of group and animal nested within group.
Differences in the mating frequency, MA duration and TTFM between boars of different social status were analysed using two-way ANOVA with social status and boar team as
factors. Post-hoc comparisons between pregnant and nonpregnant gilts were carried out using Student’s t-test. All the statistical analyses were carried out using the Minitab
Ž .
software package Minitab, 1998 .
3. Results
3.1. Mating quality aspects Almost one third of the observed MA were classified as ‘ very poor’ and only 9
Ž .
were rated as ‘ very good’ Fig. 1 . In more than 60 of the cases, the gilt was immobile Ž
. during the final boar mounting or she exhibited only some movement - 12 m . On the
other hand, in 23 of the observed MA, the gilt appeared agitated at having the boar on her back and moved around the pen to avoid this. Also, from Fig. 1, it can be seen that
45 of the services were ended by gilts either moving away or lying down. In this latter case, the gilt suddenly appeared to collapse under the weight of the boar. Moreover,
when a mating was taking place in the service pens, it was much more likely to be
Ž
2
interrupted by another boar than by another gilt 29.2 vs. 1.5, x s 151.7, df s 1, .
p - 0.001 . Ž
. The mean TTFM was 2.27 0.08 min with a range of 0.03 to 18.3 min, while the
Ž .
mean MA duration was 7.51 0.16 min with a range of 0.34 to 35.98 min. Significant Ž
. differences were found between boars in TTFM F
s 5.98, p - 0.001 , although
10,588
Ž .
there was no group effect, and in duration of MA F s 9.24, p - 0.001 , where a
10,588
Ž .
group effect also existed F s 3.25, p - 0.05 . Moreover, a significant correlation
2,588
Ž .
r s q0.58, p - 0.01 was identified between TTFM and duration of MA. However, Ž
. there was no correlation between the TTFM and TTGB r s y0.31, p s 0.43 . Also,
the TTFM did not differ significantly for the different classes of mating quality Ž
. F
s 2.01, p s 0.09 , but the duration of MA differed significantly between the
4,596
Ž .
mating quality classes F s 8.56, p - 0.001 .
4,596
The quality of mating was strongly related to the degree of movement of the gilt Ž
2
. when the boar was on her back
x s 88.7, df s 16, p - 0.001 and to the reason for
Ž
2
. termination of the observed mating event
x s 119.4, df s 20, p - 0.001 , indicating
that interruption from other competitor boars and the inability of the gilt to support the Ž
. boar’s weight when she terminated the mating event by lying down were most strongly
linked to a mating of poor quality. 3.2. Diurnal pattern of mating eÕents
Mating events followed a diurnal pattern with a peak shortly after the feeding time Ž
. 0900 h . Moreover, the number of MAs had two minor peaks early in the morning
Ž .
Ž .
0500 to 0600 h and early in the afternoon 1300 to 1400 h . The lowest number of Ž
mating events was observed between 1900 and 2000 h only four MAs in the 54 days of .
the study . 3.3. Boar mating dexterity
The difference in mating quality between and within the teams of boars was Ž
. significant Fig. 2 . The old team and the new team of boars in pen A did not differ
Ž
2
. significantly
x s 3.5, df s 2, p s 0.17 but both achieved significantly better quality
Ž
2
results compared with the pen B team of boars x s 44.6, df s 2, p - 0.001 vs. pen A
2
. old team and x s 106.7, df s 2, p - 0.001 vs. pen A new team . Also significant was
Ž
2
the difference between boars of the same team for pen A old team: x s 21.8, df s 4, p - 0.001; for pen B team x
2
s 15.6, df s 8, p - 0.05; for pen A new team x
2
s 20.2, .
df s 8, p - 0.01 . 3.4. Number of MAs and mating quality in each hour of oestrus
Only 6 of MAs were inappropriately directed to gilts outside their oestrous period, most commonly toward gilts newly introduced into the pen although all the gilts in the
Fig. 2. The mating quality scores of each of the three teams of boars observed.
study were synchronised to come into oestrus 6 to 8 days after entry. Also, one gilt appeared to have an abnormal oestrous pattern; she received and accepted continuous
MAs for over a 10-day period, suggesting a physiological disorder. The time course of MAs during oestrus are illustrated in Fig. 3. Gilts received a high
number of MAs in the very first hour of their oestrus since, by definition, the first MA in the series defined oestrus onset. Subsequently, a strong negative correlation was
found between the hours after first MA and the number of MAs that a gilt received per
Ž Fig. 3. Number of mating events that gilts received and average mating quality in each hour of oestrus based
. on 602 MAs observed in 49 gilts with continuous data throughout oestrus . The first hour of oestrus was
considered as the time of the first observed MA in the oestrus sequence.
Ž .
hour r s y0.55, p - 0.001 . The quality of the observed MAs during the first 3 h of oestrus was not good and it did not become satisfactory until the end of day 2
Ž .
r s q0.38, p - 0.005 , suggesting that early MAs occurred before full standing oestrus was established.
3.5. The relationship between social rank and reproductiÕe behaÕiour The hierarchies in all the three teams of boars that participated in the study were
linear. There was no significant correlation between boar social status and body weight. Ž
2
Mating quality score achieved was influenced by social status x
s 35.8, df s 16, .
p - 0.01 , with results suggesting that high ranking boars tended to have poorer quality MA compared with their lower ranking team mates. Moreover, subordinate boars tended
Ž .
to have more frequent MAs number of MAsrdays of observation than their dominant team mates in the period of observation, although differences were not statistically
Ž .
significant F s 2.22, p s 0.16 . Low ranking animals also tended to have longer
4,6
Ž .
MAs, but again this difference was not significant F s 0.83, p s 0.55 . Finally, there
4,6
were no significant differences between boars of different social status in TTFM Ž
. F s 0.57, p s 0.69 .
4,6
3.6. Gilt lesion scores As indicated in Fig. 4, gilt lesion scores reached a maximum just after entry and then
Ž .
declined to a level lower than the lesion scores they had prior to their entry . A significant negative correlation was found between the number of days that a gilt had
Ž .
spent in the service pen and her lesion score r s y0.75, p - 0.05 . Mean lesion score did not differ between pens.
Video recordings showed that the newly entered gilts spent most of the time at a distance from the resident animals and their sleeping areas were distinctly different. This
lasted for about a week until a new batch of gilts entered the mating pen and the fighting started again.
Ž .
Fig. 4. Gilt skin lesion scores relation to the time of introduction to the service pens ns 48 .
Table 2 The total number of MA and number of ‘good’q‘ very good’ MA that a gilt received in the period she spent in
Ž the service pens in relation to the PD result. Only continuous recordings have been taken into account 48
. animals
PD test N
Total MAs ‘Good’q‘ very good’ MAs
Positive 38
12.42 4.13
Negative 10
6.50 1.20
sed 2.53
1.30 p Value
0.024 0.029
3.7. Conception rate Eighty four percent of the 80 gilts in the study had a positive pregnancy diagnosis
Ž .
PD and 16 were negative. The proportion of negative PD animals differed signifi- Ž
2
cantly between groups, with pen A having 10r30 and pen B 3r37 x
s 4.5, df s 1, .
p - 0.05 . Gilts with a positive PD result had received more total MA and total Ž
‘good’q ‘ very good’ MA T s 2.33, p - 0.05 and T s 2.25, p - 0.05, respectively; .
Table 2 . Gilts with a positive PD were also significantly heavier at the time of selection Ž
. 15–17 days before their entry into the service pen; T s 2.80, p - 0.01 . However, there
Ž .
was no significant difference in the age at entry T s 0.95, p s 0.34 , or in the mean Ž
. lesion scores per gilt between positive and negative gilts T s 0.51, p s 0.33 .
4. Discussion
