Analysis of the feeding behavior of pigs using different models

Short-term feeding behavior is conventionally analysed using random process models. The assumption underlying these models have recently been question ed and this article describes the application of both random, and more biol ogically based, models to the feeding behavior of pigs. Feeder visits of 16 growing pigs, housed individually from 17 to 52 kg live weight, were recor ded electronically over a continuous period of 35 days. Daily food intake i ncreased linearly with time, but there was considerable individuality in th e degree of order. Pigs made between 18.8 and 80.3 (mean 47.9) daily visits to the feeder. Intervals between visits could be described by two log-norm al distributions. Two Gaussian density functions were fitted to the distrib ution of the log-transformed intervals. For the combined data from all anim als the within- and between-meal intervals were 11.2 s and 100.1 min, respe ctively. A model with three Gaussian functions gave an improved fit to the interval distribution. The within and between meal intervals were then esti mated to be 4.2 s and 93.9 min, respectively. The middle distribution of in tervals ranged from 0.5 to 38.1 min. The intervals were also described by r andom process models; again, a three-process model gave an improved fit com pared to a two-process model. The mean estimated number of meals per day fr om the three Gaussian model was 14.3, and from the three process random mod el, 16.3. A biological interpretation of the three types of interval sugges ts that: (1) pigs eat in meals separated by long intervals; (2) meals consi st of clusters of eating bouts separated by shorter intervals, sometimes as sociated with drinking; (3) within each eating bout short intervals occur a s pigs constantly move in and out of the feeder. It remains unclear what un derlies the observed patterns of eating. (C) 2000 Elsevier Science Inc. All rights reserved.