The post-weaning period (weaning to approximately 10 weeks of age) is one of the most welfare-critical phases in pig production. Abrupt separation from the sow, dietary change from milk to solid feed, social mixing with unfamiliar pigs, and environmental change create a convergence of stressors causing the "post-weaning stress syndrome." Effective weaner management dramatically improves welfare and production outcomes.
Stressors at Weaning
Commercial weaning typically occurs at 21–28 days in the UK (EU law mandates minimum 21 days). The simultaneous occurrence of multiple stressors is the core welfare problem:
- Loss of maternal contact and dam's milk — sudden nutritional change and loss of comfort
- Social mixing — new pen-mates cause aggression and re-establishment of hierarchy
- Dietary transition — from highly digestible sow's milk to plant-based solid feed; immature gut digestive capacity causes post-weaning diarrhoea
- Environmental novelty — new pen, housing system, temperature
Nutritional Management
Weaner diet formulation is critical for gut health and welfare:
- Phase 1 diet (weeks 1–2 post-weaning): highly digestible ingredients (spray-dried plasma, fish meal, whey, cooked cereals); maximum digestibility to support gut recovery
- Phase 2 diet (weeks 3–4): gradual transition to more economical ingredients
- Phase 3: conventional grower diet introduction
- Feed presentation: wet or porridge feeding improves intake in the first days post-weaning; pelleted or rolled cereals preferred over coarse meal initially
Post-Weaning Diarrhoea (PWD)
PWD — primarily caused by enterotoxigenic E. coli (ETEC) — is the most common weaner health challenge. Contributing factors include overeating at weaning, villous atrophy from dietary change, and immunological immaturity. Prevention strategies include:
- Highly digestible weaner diets with controlled starch levels
- Zinc oxide (pharmacological dose) has been historically effective but is now restricted in the EU due to environmental concerns
- Acidifiers (organic acids) reducing gut pH inhibit ETEC proliferation
- Vaccination (against ETEC K88, K99, 987P fimbriae) via sow vaccination pre-farrowing
Environmental Temperature
Weaners have limited ability to thermoregulate — standard weaner temperatures of 28–30°C in the first week post-weaning (reducing 1°C/week) are essential. Wet, draughty housing dramatically increases respiratory disease risk and welfare compromise. Solid flooring in the dunging area maintains body temperature better than fully slatted systems.
Welfare Monitoring
Daily observation of all weaners — checking for dullness, separation from group, reluctance to eat, diarrhoea, poor growth, respiratory signs, and injuries — enables early detection and treatment. Mortality and morbidity recording provides benchmarking data for welfare improvement over time.