Sow and piglet behaviour and weight: implications of different ages of weaning : a study within Swedish piglet production

Abstract: Natural weaning of piglets occurs gradually and finalises between 14-17 weeks of age. In 2017, Swedish pig production faced changes in national regulations regarding weaning procedures. The new regulations implemented a decrease of weaning age from 28 days of age to 21 days of age for a maximum of 10 % of piglets in each batch. The change of regulations derived from a pilot study suggesting that a decrease in weaning age would increase productivity. The pilot study also suggested that the late weaning age in Swedish pig production negatively affects sow body condition due to increased litter sizes in the genetic lines used. However, this has not been confirmed in other studies. Instead, other studies suggest that the negative impact of decreased weaning age on piglets outweigh the potential positive effects on the sow. Most studies comparing differences in weaning age have been performed in other production systems than the Swedish, distinguished by loose farrowing pens with straw provisions compared with the farrowing crates used in most studies on this topic. Thereby, the knowledge on how weaning age affects piglets and sows under Swedish production conditions is lacking. The current master thesis is a pilot study designed to map and investigate how differences in weaning age affect sows before weaning and the effects on piglets before and after weaning, aiming to increase the knowledge about the effects of different weaning ages in an environment similar to Swedish production systems. The study compared three groups with different weaning ages; 3 (n=7 litters), 4 (n=6 litters), and 5 (n=6 litters) weeks and contained both scan sampling and continuous recording of sow and piglet behaviour from 14 days of age up until 44 days of age. The behavioural recording was performed two days per week, on day 1 and 3 of each week. Scans were collected once per hour between 07:00 and 20:00, while continuous recording was performed three times per day (09:00, 13:00, 17:00) for five minutes each. Sow weight and backfat thickness were collected in connection to farrowing and weaning. Piglet growth was collected between farrowing and nine weeks of age. The results of this study indicate that piglets weaned at 21 days of age spend more time standing up, eating solid food, fighting, belly nosing and mounting after weaning than piglets weaned at 35 days of age. Piglets weaned at 28 days of age were belly nosing more after weaning than those weaned at 35 days of age. Piglets weaned at 21 days of age had a significantly higher growth rate between 28 days and 9 weeks of age than piglets weaned on days 28 and 35. Regarding the sows, there were no statistically significant results found on behaviour, weight or backfat thickness. However, the descriptive statistics show that sows weaned from their piglets on day 35 had less backfat than those weaned on days 28 and 21. They also showed that sows spent less time having snout contact with the piglets and laid down less the longer they stayed with the piglets. Since this is a pilot study, the results found should be interpreted with caution. However, the results show a need for further research to confirm whether these findings apply to larger populations.