Optimizing amount of straw for growing-finishing pigs : considering time spent in manipulative behaviour

Abstract: In support to a decision to be made by the Swedish central competent authority on a minimal amount of straw for conventional growing-finishing pigs, a study using 168 pigs provided 7 different amounts of straw (20, 40, 60, 80, 100, 200 or 300 grams/pig/day) was performed. The straw was provided either once or four times per day. Detailed behaviour observations were made using focal animal sampling and continuous recording for one hour between 9 and 10 am and again between 3 and 4 pm. The data analysis is presented in three ways: broken stick model, polynomial trend line and logarithmic trend line. No method was suitable on its own but the use of all the methods simultaneously was found to portray the data in the best way.No significant differences were found when comparing pens provided with straw once or four times per day. The maximum time spent in manipulative behavior towards straw could not be observed in the current study suggesting that the amount of straw needed for pigs to perform that behavior at maximum is above 300g. The time spent in manipulative behaviour directed towards straw was increased over 10% ranging up to 27% in all the pens receiving over 200g of straw per day compared to the range from 4-22% in pens receiving 20-100g of straw. Meanwhile, the time spent in redirected behaviour was decreased below 5% in all the pens receiving over 200g of straw per day. 200g is also the value received when using the broken stick model for data of redirected behaviour from all the pens.