| Population: |
York X Landrace, Piglet, (US). |
| Sample size: |
56 litters.
Before weaning: 48 litters.
After weaning: 192 piglets selected (48 post-weaning groups of piglets consisting of 16 post-weaning groups per pre-weaning treatment group).
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| Intervention details: |
Pre-weaning treatment groups: Group 1 control, no socialisation (CM0): n = 16 litters. Housing design: Standard farrowing crates from birth until weaning on day 18.
Group 2 socialisation with one unfamiliar litter (CM1): n = 16 litters. Socialisation housing design: co-mingle with one unfamiliar litter from days 10–18. Socialisation was facilitated by removing the barrier between adjacent farrowing pens. Socialisation group size: two litters per pen (socialisation group size is the number of litters that interact with one another during lactation).
Group 3 socialisation with two unfamiliar litter (CM2): n = 16 litters. Socialisation housing design: co-mingle with one unfamiliar litter from days 10–14 then another unfamiliar litter from days 14–18. Socialisation was facilitated by removing the barrier between adjacent farrowing pens. Socialisation group size: two litters per pen.
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| Study design: |
Non-randomised controlled trial. |
| Outcome studied: |
Weaning age: approximately day 18.
Socialisation length: 8 days.
Regroup condition: One male and one female from one litter, plus one male and one female from another litter, within the same pre-weaning treatment group. Both pairs of littermates had similar weight and were unfamiliar to one another.
Post-weaning group size: four piglets.
Familiarity ratio: 1:1.
Growth performance:
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Mean daily weight gain / average daily weight gain (ADWG): days 2, 9, 13, 17, 21 and 25.
Behavioural indicators:
Behavioural tests. Behaviour: 48 hour post-mixing (using 10 min scan sampling). -
Ear injuries: days 2, 9, 13, 17, 21 and 25. Average ear injuries score for the entire experiment and time points.
Social challenge: days 13, 17 and 21. Two unfamiliar piglets = one focal piglet + one piglet from another litter. Observed social interactions for 10 min. Social recognition: days 16 and 25. Social investigation (frequency, duration, and latency).
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| Main Findings (relevant to PICO question) |
Growth performance:
Ear injuries: no significant difference found. -
Behaviour: 48 hours post-mixing.
Belly-nosing: CM2 spent a higher proportion of observations performing belly-nosing than CM0 (significant, P = 0.05). CM2 > CM1 > CM0 (trend only). All aggressive interactions: CM1 spent a lower proportion of observations in this than CM0 (significant, P < 0.05). CM1 < CM2 < CM0 (trend only). Aggression towards non-littermates: CM1 spent a lower proportion of observations in this than CM0 (significant, P < 0.05). CM1 < CM2 < CM0 (trend only). All activities with non-littermates: CM1 < CM0 (trend only), CM2 no significant difference from the two.
Behavioural tests – not examined in this review because it did not specifically report post-weaning results.
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| Limitations: |
Treatment group allocation method was not stated. The pre-weaning selection criteria of 48 litters out of 56 litters was not explained. Outcomes were measured in focal piglets only. Selection criteria for focal piglets included sex and weight only. Ear injury scoring system was not quantified (vague definition such as score 1 = few scratches). For social challenge or social recognition, the post weaning result was not isolated from the pre weaning result. Total number of piglets before weaning was unknown. Number of piglets in each treatment group pre-weaning and post-weaning was not specified. The number of assessors for behaviours and ear injuries was not specified.
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