| Population: |
Breed unknown, piglet, (Spain). |
| Sample size: |
Before weaning: 52 litters.
After weaning: 16 weaning pens, about 39 piglets per pen (range from 31–45).
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| Intervention details: |
Pre-weaning treatment groups: Piglets were randomly allocated into a treatment group.
Group 1 no socialisation / control (CON): n = 12 litters. Housing design: littermate-only with sow in a farrowing pen until weaning.
Group 2 socialisation from day 7 postpartum to day 25 (M7): n = 20 litters (262 piglets). Socialisation housing design: littermate-only with sow in a farrowing pen until day 7, then the barrier between two adjacent farrowing pens was removed at day 7 post-partum. 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 from day 14 postpartum to day 25 (M14): n = 20 litters (253 piglets). Socialisation housing design: littermate-only with sow in a farrowing pen until day 14, then the barrier between two adjacent farrowing pens was removed at day 14 post-partum. Socialisation group size: two litters per pen.
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| Study design: |
Randomised control trial. |
| Outcome studied: |
Weaning age: 25 days.
Socialisation length: 18 days for M7, 11 days for M14.
Regroup condition: Regroup with unfamiliar piglets from the same treatment group based on similar body size.
For outcome measurement: Six piglets per litter of the 12 largest litters in each pre-weaning treatment group were selected (heaviest male and female, lightest male and female, median pen weight male and female). In total, 72 piglets were selected from each pre-weaning treatment group for post-weaning outcome measurement.
Physiological indicators:
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Salivary cortisol. 1 day before weaning (premixing), 1 day after weaning (+1), 2 days after weaning (+2) in a sample of 72 piglets per treatment group. Basal level of salivary cortisol = premixing / preweaning level.
Growth performance:
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Average daily weight gain (ADWG). Weighed at days 1, 7, 14, 21, 28 and 35 after birth.
Behavioural indicator:
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| Main Findings (relevant to PICO question) |
Physiological indicators:
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Salivary cortisol.
No significant difference between basal levels (pre-mixing) of cortisol among treatment groups. CON piglets showed greater increase in cortisol than M7 and M14 piglets (significant, P = 0.02 respectively). Impact of sampling time: later sampled piglets showing significantly higher cortisol level (P = 0.01).
Growth performance:
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ADWG
Week 1 (lactation): CON > M7 (significant, P = 0.01); CON > M14 > M7 (trend). Week 2 (M7 socialisation starts): no significant difference found. Week 3 (M14 socialisation starts): CON > M7 (significant, P < 0.01); CON < M14 (significant, P = 0.01). Week 4 (at weaning): all group dropped, but no significant difference among treatments. Week 5 (1 week after weaning): all slightly increased, but no significant difference among treatments.
Behavioural indicators:
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Number of skin lesions.
However, number of skin lesions on any day (–1, +1, +2) do not significantly differ among treatment groups.
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| Limitations: |
Total numbers of piglets before and after weaning were not specified. Number of piglets in pre-weaning control group was unknown. The mechanism of randomisation for treatment group allocation was not reported. Post-weaning group size was unknown. Only selected piglets were measured for skin lesions and salivary cortisol. Though measurement was conducted in a sample of 72 piglets per treatment group, the final result presented for skin lesion contained less data (only CON n = 66, M7 n = 60, M14 n = 60). No explanation was given for the missing data. The proportion of familiar piglet to unfamiliar piglet in a pen (familiarity ratio) after regrouping was not specified.
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