Satiety splits drinking behavior into bouts: Organization of drinking in turkeys

The regulation of the drinking behavior of animals is usually overlooked, and the traits associated with it are not well defined. We used a unique data set of measurements of individual drinking behavior in turkeys 1) to validate the system of data generation, 2) to develop a methodology to allow clustering of drinking events and splitting behavior into bouts, and 3) to develop traits related to drinking behavior and its regulation and investigate how these traits may be affected by bird genotype. Visits to drinkers were generated by an electronic, custom-made equipment that automatically measures the individual drinking behavior of a large number of turkeys from 3 different genetic lines. The overall reliability of the electronic system was estimated from video observations and resulted in a predictability of 98.8% and sensitivity of 98.6%. A novel method based on mixture distribution models allowed clustering of drinking events and splitting behavior into bouts by estimating the shortest interval between visits to the drinker that was considered to be part of a bout (bout criterion). The method predicted that after the end of a given bout the probability of the bird initiating the next bout was low but increased with time since the last bout. As a result, drinking bouts were not randomly distributed but were predicated on the physiological principle of satiety, suggesting that they constitute biologically appropriate units for expressing drinking behavior. The applied method resulted in bout criteria estimates of 665, 672, and 602 s for genetic lines A, B, and C, respectively. On the basis of this methodology, a number of drinking behavior traits, such as bout duration and frequency, and water intake per bout were identified that revealed differences (P < 0.01) in the drinking behavior between the turkey genetic lines. Similarly, time accumulation patterns of drinking behavior traits within a day differed (P < 0.01) within and between genetic lines, suggesting that variation in drinking behavior exists and birds use different behavioral strategies to meet their water intake requirements. Development of drinking behavior over time was similar between the lines, suggesting conservation of this behavioral organization. As well as providing ideas about the regulation of drinking behavior, the developed behavioral traits may be of practical relevance because water utilization, along with feed efficiency, is part of overall biological efficiency.