Mounting behaviour in finishing pigs: Stable individual differences are not due to dominance or stage of sexual development
Abstract
Every year around 100 million male piglets are castrated in the EU, usually without anaesthesia
or post-operative analgesia. This surgical intervention is painful and stressful. Several
main players within the pig industry have voluntarily agreed to end the practice of surgical
pig castration in the EU by 2018. One alternative to castration is entire male pig production.
However, entire males behave differently than castrates, for example, by performing more
mounting behaviour, which is suggested to be a welfare problem.
The aim of our study was to develop a comprehensive ethogram of different types of
mounting and to investigate properties, causes and consequences of mounting behaviour
in finishing pigs.
The study included 80 entire male and 80 female pigs from two farrowing batches born
six weeks apart. Mixed sex and single-sex housing of pigs are both common in pig farming,
so to ensure our study was representative, the 160 pigs were assigned to social groups of
20 in three treatments: entire male pigs only (MM, 2 groups, n = 40), entire females only
(FF, 2 groups, n = 40) and entire males and females mixed together (MF, 4 groups, n = 80).
Measurements took place during the final six weeks before slaughter (between 63.5 and
105.5 kg). Observations of mounting behaviour on 12 days per batch suggested that: (i)
males mounted more than females, (ii) within sex, there was no effect of treatment on
the amount of mounting (although the statistical power of the study to detect these effects
was low), and (iii) there were individual differences in mounting that were stable over time
(within sex).
Classification of mounting into different categories revealed that sexual mounting was
most common overall and in males but only rare in females. Compared to other types of
mounting (e.g. caused by crowding or during a fight), sexual mounts lasted longer and provoked
more screaming by the recipient. There were no relationships between mounting
behaviour on the one hand and dominance rank in food competition tests, the circulating
levels of sex hormones (oestradiol, testosterone and progesterone) at the end of
the study, the health scores (lameness and scratches) or weight gain on the other hand.
Journal Title/Title of Proceedings
Applied Animal Behaviour Science
Rights
Copyright © 2013 Elsevier B.V. All rights reserved.
Version
Accepted Manuscript
Volume/Issue Number
147:1-2
Page Numbers
69‐80