Measuring Pig Travel By Image Analysis
1Author is Research Scientist in Animal Science at The Danish Institute of Animal Science, Dept. of Animal Health and Welfare, Research Center Foulum, P. O. Box 39, 8830 Tjele, Denmark, e-mail: Nabil.Brandl@sh.min.dk, HomePge: http://nabilnabil.homestead.com
An attempt has been made at Foulum Research Center, in Denmark, to measure the travelling distance for each pig within its environment, using image analysis system (a semiautomatic system). These measurements explained the behaviour and pig's conditions. Video analysis had been used to assess the pigs' movement. This method is difficult and costly. The main purpose of this paper was to develop an alternative method in measuring pigs activities without disturbing them. The method had been developed using a computer pc based program, video and image analysis techniques. The program works in two ways, first selected a series of video frames with time laps, then qualified an interactive operator to select points, which locate pigs position on the image, and saved the results on a computer ASCII file for further analysis. Using the saved data to compute the travelling distance for each pig. The material, which had been used was 10 Yorkshire pigs. Half of the pigs were normal, while the second half were dwarf. The results showed pig's pattern of activities in one hour observations. This pattern explained pig's movements surrounding the feeder, sleeping and manure places, which demonstrated the pig's conditions. It concluded that image analysis is a promising method to monitor pigs activities in pigs' houses, as well as monitor activities manually (video analysis), which it recommended to be used in applied ethological studies.
Keywords: Travelling distance, Video techniques, Image analysis, Animal behaviour, Animal locomotion and pigs.
Animal health and welfare can be assessed by measuring its locomotion. Many researchers have confirmed that lack of animal locomotion will indicate lack of welfare. The skeletal system of animal will provide the animal by mechanical strength and calcium/phosphorus contents. Therefore muscles and bones are essential for the normal movement. Any change in normal pattern, will change animal well being. Perrin and Bowland (1977) had investigated the effects of enforced exercise on the incidence of leg weakness in growing boars. They found insignificant effect of exercise. Marchant and Broom (1996), who investigated the effect of dry sow housing conditions on muscle weight and bone strength. They found significance effect, where the sows have more space to move about. Studying movement in pigs houses can be useful to evaluate the animal condition, such as number of time visiting the feeder, or the travel distance. Gonyou (1992) has studied the feeding behaviour. He found that individual pigs spent more time and eating more than pigs kept in groups, while Hsia and Wood-Gush (1983) had found that social facilitation will increase eating time. Christison & deGoodijer (1986) had found that it was much easier for a person to watch the animals and quickly draw on a grid on paper, than it was to record the movements on video camera. The alternative method in measuring the pigs' movement is image analysis. The image analysis techniques provide an alternative method, instead of the manual direct method (video watching). Schwarting et al (1993) had designed an image analysis system to monitor the rats movement, to distinguish between the conditional movement from the unconditional one. Bonatz et al (1987) had proved the validity of image analysis method to monitor the movement of animal, which injected by amphetamine into the brain area (substantia nigra), to detect brain lesions. Also Barber et al (1973) had investigated the rotation behaviour in rats with brain lesions, by designing an electronic apparatus.
The main purpose of this paper was to develop a method for the behaviour tests and observations on pigs, by measuring pigs' activities without disturbing them, using a semiautomatic image analysis system.
MATERIAL AND METHODS
Ten pigs of Yorkshire breed have been used to measure their movement. The pigs have descended from one litter, which contains 5 dwarf and 5 normal pigs. The choice of this litter was to test the abnormal movement in the pen. Therefore the dwarf pigs were placed together in one pen (1.53X3.25 m) and the normal pigs placed in another pen with the same size. The pigs were video recording from above. The video frames were gathered on a video tape with normal speed (30 frames per second) for a period of 1 hours in the morning.
Figure 1. Two successive video frames.
Two PC programmes have been used to analyse the video frames (Figure 1). One to subtract images with 4 seconds intervals and storage on pc-disk. The other to measure the travel distance by determining the pigs' positions (x,y co-ordinates), using pc-mouse and software, which was windows-based system. The software was built in a user friendly way, which allowed the users to load the images and click with the mouse to determined the x,y co-ordinates. The x,y co-ordinates were saved automatically on an ASCII file for further analysis. 200 images were collected to represent the most active period for the dwarf and normal pigs (from 8 am to 9 am).
The measuring variable was the travelling distance, which calculated as follows: