Does nose ringing make any sense?

Summary

Outdoor sows are nose ringed to maintain grass cover. Intact pasture insures the sows possibility to graze and is also assumed to reduce the nutrient leaching. However, no evidence of reduced leaching from fields with ringed sows is available. Rooting behaviour constitutes an essential part of the sows’ natural behavioural repertoire. In organic husbandry it is an established aim to consider the animals’ natural behaviour, and by allowing nose ringing in organic pig production the natural behaviour of the animals has been prevented in order to consider the environment. The purpose of this experiment was to relate grazing and rooting activity of sows to grass cover and nutrient leaching. Three treatments were tested on 78 sows in total: 1: sows with nose rings, 2: sows without nose rings, 3: sows without nose rings and with a gradual pasture allocation. All treatments were carried out with pregnant and lactating sows. The stocking rate was the same for all three treatments and the experiment was carried out May to September 2002. The behaviour of the sows, level of activity and position in the field were registered for one day each week during the entire grazing season. In July and September the grass cover was quantified by remote sensing and in September soil samples were taken in order to determine the nutrient leaching. Data were analysed using ANOVA. The incidence of grazing behaviour was the same in all three treatments. Grass cover was twice as dense in fields with ringed sows than in fields with unringed sows (p<0.05). When unringed sows graze as much as ringed it would indicate that the nourishment in the grass is similar even though the cover is less, i.e. the grass is growing more in the fields with unringed sows. Growing grass absorbs nutrients, which may result in a reduced nutrient leaching.