Do sows drink at night? This was the question posed by the Ministry of Food, Agriculture and Fisheries to scientists at Aarhus University, who have now provided an answer based on a survey of the drinking behaviour in an organic herd of free-range pigs. The question was posed not just out of curiosity, but because it is of practical importance for producers of free-range pigs where the pigs are kept outdoors all year round – even when it freezes.

Current legislation stipulates that free-range pigs must have access to drinking water that is clear of ice all the time. If sows only drink during the day, this means that the producer would not need to keep the supply going at night and thus reduce the risk of the water system freezing up during periods with frost. This was why the Ministry asked scientists from Aarhus University to investigate the drinking habits and diurnal rhythm of the sows.

The investigation shows that the sows drink water both day and night – also when the temperature goes below zero.

In order to test if the sows made use of the availability of water during the night, the scientists put up a flow meter and video camera of the water cups in the field. The drinking habits of the sows were monitored during lactation both when the temperature was over and when it was below freezing point. Lactating sows were chosen because they are assumed to have the largest need of water. In this way, the investigation will have a solid basis for an assessment of the extent to which sows drink water during frosty nights.

More water is drunk during the day

There was a sharp rise in the daily water consumption after farrowing when the milk production started. Most of the drinking took place during the day.

- We saw a clear diurnal rhythm in the water intake of outdoor sows. Pigs drank 70-75 percent of their water between 8 in the morning and 8 in the evening. The rest was drunk with on average two trips to the drinking cup between 8 in the evening and 8 in the morning, irrespective of weather conditions, explains scientist Heidi Mai-Lis Andersen from Aarhus University.  

There was, however, some variation in the drinking behaviour of the sows. During rainy periods, the sows drank less from the water cups. This was probably because they drank from puddles instead. During frosty periods, the water consumption was, on the other hand, higher. The results do not give an unambiguous explanation of why this is so, but both a higher feed intake at low temperatures, and a change in plant dry matter content and less precipitation in frosty weather could be contributing factors.

- On the background of the investigation we can say that outdoor farrowing and lactating sows get 25-30 percent of their daily water intake during the night when the water cups are located 8-15 m from hut entrances, says Heidi Mai-Lis Andersen.

Read also the article ”Pigs on the water wagon” here.

Further information: Project scientist Heidi Mai-Lis Andersen, Department of Animal Science, email: heidimai.andersen@agrsci.dk, telephone: +45 8715 7835