Behaviour of animals changes with the time of day, time of year, weather, food supply, reproductive state and stressors, like handling and transportation.
Most grazing ruminants rest at night, with alternate grazing and resting / ruminating periods during the day (Kent 1977). In contrast, rats are active and feed during the hours of darkness (Liles and Flecknell 1993a).
Pain may influence the pattern of behaviour shown by animals in a 24 hour period. The normal behaviour pattern, for each species of animal under its/their husbandry conditions, needs to be established before alterations to the pattern by a parameter like pain can be confirmed.
Twenty-four hour monitoring may be required to appreciate subtle changes in patterns of behaviour (Thornton & Waterman-Pearson 2002). However, an animal in pain may be recognised by an alteration in its response to regular supplementary feeding i.e. it does not come and feed with the rest of the flock / herd.
Thornton & Waterman-Pearson (2002) showed that lambs, castrated with rings at less than a week of age, played less than control lambs in the three days after the day of treatment. Liles and Flecknell (1993a) reported decreased food and water intake during dark hours after surgical interference. Analgesic treatment reversing the response.