Behaviour and productivity of pigs in groups composed of disproportionate numbers of littermates

Abstract

Gonyou, H. W. 1997. Behaviour and productivity of pigs in groups composed of disproportionate numbers of littermates. Can. J. Anim. Sci. 77: [205][206][207][208][209]. Forty litters of eight pigs each were paired by age and weight and re-grouped at the beginning of a 12-wk grower/finisher period. Each pair of litters was assigned to two pens, with two pigs from one litter (Minority) and six pigs from the other (Majority) in each pen. Four pairs of litters were removed from the experiment due to loss of pigs from injury or poor health. Agonistic encounters following re-grouping were used to rank each Minority pig and to classify it as being within the Dominant or Subordinate half of the social hierarchy. Minority pigs within a pen tended to obtain similar social ranks (within two ranks in 20 of 30 pens; P < 0.05), but were as likely to be Dominant as Subordinate (11 vs. 9 pairs, respectively). The activity and position of all pigs were sampled once daily, 5 days a week. One Minority pig was designated as the focal pig for these observations. The second Minority pig was more likely to be engaged in the same activity as the focal pig than were Majority pigs (P < 0.01), and would lie closer to the focal pig than would the Majority pigs (P < 0.01). There were no differences in the proportion of Majority and Minority pigs which were removed from the experiment due to injuries, nor in the type of injuries requiring their removal. Examination of all pigs at the mid-point of the study revealed some evidence of injury on the head, ears, shoulders, back, flanks, ramp and tail of 76, 75, 87, 90, 91 and 95% of the pigs, respectively, but no differences between Majority and Minority pigs in location or severity of injuries. Average daily gain for the entire experiment was 775 g d -1 , and did not differ between Majority and Minority pigs during any 2-wk period of the study. It is concluded that littermates continue to associate with each other after re-grouping and that they attain similar social status. However, the litter with the largest number of pigs present does not consistently achieve social dominance or a competitive advantage manifested in improved weight gain. . Pour des raisons de blessures ou de mauvaises santé, quatre paires de portées étaient retirées de l'expérience. La fréquence des rencontres de type agonistique à la suite du réallotement servait à classer chaque porc de minorité selon son appartenance à la fraction dominante ou subordonnée de la hiérarchie sociale. Les porcs minoritaires d'un même enclos manifestaient généralement le même rang social (écart de 2 rangs dans 20 enclos sur 30, P < 0,05), mais ils avaient autant de chance d'être dominants que subordonnés (11 paires contre 9). L'activité et la position de tous les porcs étaient observées une fois par jour, 5 jours par semaine et, pour ces observations, un porc minoritaire était désigné porc cible. L'autre porc minoritaire était plus susceptible de s'adonner à la même occupation que le porc cible que les porcs en majorité (P < 0,01) et aussi de s...

Energy metabolism in young pigs as affected by establishment of new groups prior to transport

“…This conclusion is supported by results of F RIEND et al. (1983), G ONYOU (1997) and M C G LONE et al. (1987), who found no long‐term effect of mixing.…”

“…Although regrouping can cause an extra amount of (social) stress (F RIEND et al. 1983; R UNDGREN and Lö FQUIST 1989; H ESSING and T IELEN 1994), no long‐term effects of mixing were found in studies of G ONYOU (1997), F RIEND et al. (1983), and H EETKAMP et al.…”