Use of evolutionary operation technique on farm level

Heidi M.L. Andersen Erik Jørgensen & Lene J. Pedersen


48th Congress of the International Society for Applied Animal Ethology


To solve health or welfare problems on herd level, farmers try different management initiatives. Often more than one procedure on the farm is changed at the same time without a systematic plan, making it difficult to get an overview of the impact of the different procedures and possible interactions between them. Evolutionary operation (EVOP) is a technique for the systematic experimentation with and improvement of an ongoing full-scale production without actually interrupting it. EVOP use a randomized controlled trial to solve a specific problem, normally by optimizing two or three parameters at a time. EVOP is intended to introduce small changes in the process during normal production. These changes are not large enough to interrupt production, but are significant enough to provide valuable local knowledge about what the optimal herd procedures are. EVOP is used in other areas including biological processes, but has, to our knowledge, not been used in animal production. he purpose of this project was to exemplify the use of EVOP on a pig herd and use the EVOP technique to see how three different management procedures affect the pigs’ water intake during the day. As it is assumed, water consumption can be used as a measure of the animals’ circadian rhythm.

A three factorial experiment with 654 pigs (34.3±4.1 kg) was carried out. The variables were: stocking density (14 or 18 pigs per pen), number of straw allocations (one allocation of 140 g straw per pig/day or four daily allocations of 35 g straw per pig) and allocation of pigs to pens (randomly or by size). The pigs were fed ad libitum. Water use and temperature at pen level were continually measured during the experimental period (28 days). The day was divided into two 12 h periods: ‘day’ (from 7:00 h to 18:59 h) and ‘night’ (from 19:00 h to 06:59 h) and the proportion of water use during the night of the total water used was calculated at pen level. Data was analyzed using a linear model. On average, 25.9% of the total amount of water was used during night. Increasing stocking density increased the proportion of water used during night with 2.2 percentage points (P=0.02). Random distribution of the pigs instead of sorting pigs by size at pen level reduced the proportion of water used during night by 2.3 percentage points (P=0.03), while no significant effect of the number of straw distributions (P=0.40) or interactions were found. If the water consumption is a measure of the animals’ circadian rhythm, the results indicate that the stocking density and sorting of pigs by size impact on the pig’s circadian rhythm.

The results show that the use of EVOP may be powerful enough to give a fast indication of the optimal combination of production factors within the herd.