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
Of the 933 MAs observed in this study, 35 were classified as ‘ very poor’, whereas 18 and 9 were classified as ‘good’ and ‘ very good’, respectively. Other studies
Ž .
Rikard-Bell, 1992; Grigoriadis, 1997 found different results, with a much higher proportion of good quality matings. A comparison between these and the present study
Ž is not possible however, because of the difference in the nature of the criteria used i.e.,
. Ž
qualitative vs. quantitative and in the service systems examined i.e., conventional vs. .
dynamic . It is to be expected that overall mating quality would be better in a conventional individual service system, since sows are not introduced to the boar until
believed to be showing standing oestrus. Although in the dynamic service system, relatively few MAs occurred outside the oestrus period of the gilts, it seemed that many
MAs were made during pro-oestrus when the gilts may have been giving olfactory andror behavioural indications of impending oestrus but not yet showing a full standing
Ž .
response. Shaw and Edwards 1995 , examining the mating efficiency in an outdoor multi-sire mating system for multiparous sows, reported quite similar results to the
present study. The mean boar first mount latency in this study was 2.27 min, which is much more
than that observed in other investigations taking place in conventional mating systems Ž43 s by Signoret, 1970; 41 s by Hemsworth et al., 1991; 39 s by Soede and Schouten,
. 1991; and 40 s by Grigoriadis, 1997 . This difference makes sense considering that in
Ž the current system, the animals had a number of influences from outside other boars,
. oestrous gilts , which distracted the boar from the gilt and prolonged the first mount
latency. Also, the dimensions of the service pens in this study were much bigger than a typical mating pen, thus the gilt could avoid mounting quite easily by running away
when not in full standing oestrus.
The percentage of mating events, which were terminated by the gilt lying down, was as high as 27. In these cases, the gilt could not support the weight of the boar and
collapsed. Similar results have been found in an outdoor mating system by Shaw and Ž
. Edwards 1995 . The boars used in the study were of various weights, ranging from 162
to 308 kg while the average gilt weight was 109 kg ranging from 95 to 115 kg. This difference makes it understandable why, in so many cases, the gilt could not support the
weight of the boar, and highlights the need for a high replacement rate with young boars in such a system where boar feed intake cannot be controlled.
Mating events in this study followed a diurnal pattern with a major peak after feeding Ž
. Ž
. 0900 h . This finding is not in agreement with Tanida et al. 1989 , who indicated that
mounting activities in a multi-sire mating system were concentrated in the period between midnight and morning. The reason for this difference may lie in the high
temperatures and different photoperiod under which Tanida et al. carried out their investigation, which may have discouraged the animals from sexual activities during the
day.
The mating quality difference between individuals was significant in all the boar teams. Boars of the pen A new team achieved higher quality MAs compared with the
Ž .
other teams. These boars were of young age 11 months old and much more active than Ž
. boars in pen B and the old team in pen A 14 and 16 months old, respectively . There is
a need for longitudinal studies of a dynamic service system to verify this aspect. There was no significant effect of boar social status on the mating frequency, the
TTFM and the duration of mating event. However, there was a striking trend for low ranking boars to achieve more frequent, better quality and longer duration MAs than
high ranking boars. Moreover, mating quality grade was related to the boar social status. A number of authors have reported that in the wild dominant boars have priority of
Ž .
access to all resources including mates Craig, 1986; Mendl et al., 1992 , but this does not seem the norm in the semi-intensive conditions of a dynamic service system. It may
be that oestrous females were not considered to be a limiting resource in these circumstances, or that pair feeding tests are not the most appropriate method to decide
the male reproductive hierarchy in a dynamic service system. Social and sexual status of the boars raised under these conditions, where they continuously have access to oestrous
females, are two completely different parameters and they should not be confused. Mate
Ž .
preferences exhibited by females Tanida et al., 1991; Hemsworth et al., 1992 may play an important role in the organisation of sexual hierarchy in a team of boars.
In total, 84 of the observed gilts were PD tested positive while 16 were negative. These PD results are satisfactory compared with other studies examining animals treated
Ž .
in the same way Schilling and Cerne, 1972; Britt et al., 1987 and general UK data Ž
. MLC, 1998 . Differences between pregnant and non pregnant animals in the number of
total MAs and ‘good’q ‘ very good’ MAs received were significant. These results Ž
. Ž
. support findings by Drugociu 1968 and Hemsworth et al. 1978, 1991 , but not those
Ž .
Ž .
from Soede and Schouten 1991 and Grigoriadis 1997 , who stated that conception rate was independent of the quality of natural service. Examination of the pattern of MAs
received by the PD negative gilts indicated that they had generally received a low number and poor quality MAs, although 90 of them had shown some sign of oestrous
behaviour. However, some gilts had received good quality MAs, indicating that other factors, for example, boar fertility, had an influence on gilt pregnancy and might account
for the difference between pens. Gilts that would later test positive were significantly
Ž .
heavier than negatives at selection 15–17 days prior to entry into the service pens . However, positive and negative tested gilts did not differ significantly in their age and
mean lesion score. This latter finding indicates that the level of fighting in the service pens was not a major determinant of the gilt conception rate and is not in agreement
Ž .
Ž .
with Mendl et al. 1992 and Simmins 1993 . An increase in the recorded lesions was observed 3 days after entry due to intense
fighting especially in the first 2 h after the new and old gilts first met. Then, they declined rapidly and remained relatively constant from 21 days onwards. These results
Ž support findings from studies with group-housed females Arey and Jamieson, 1997,
. Ž
1998 and studies with female dynamic groups Spoolder et al., 1996; Rigat et al., .
1998 .
5. Conclusion
