Mixing groups of sheep changes vocalizations when an individual animal is isolated

In recent years, welfare, which includes pleasurable and unpleasant emotions, is of utmost importance in animals reared under intensive farming systems. Various indices have been reported to evaluate welfare. Among them, vocalizations form non-invasive indices of animals’ inner state. The aim of the study was to determine whether changes in ewes’ raising group composition may alter differences in their vocal characteristics. Forty animals of two dairy sheep breeds (Chios and Karagouniki) were used. The experiment lasted for six months divided into three equal periods (A, B, and C). During period A, the animals were divided in two groups based on their breed. In period B the animals were equally mixed in two groups, while in period C the animals returned to their initial state, as in period A. The behaviour of the ewes was recorded during the entire experimental period. At the end of each period, each ewe was isolated, and its vocalizations and behaviour recorded. The composition of the group influenced (p < 0.05) the basic parameters related to frequency and amplitude, which indicates a negative emotional valence. This negative effect was also supported by the behavioural observations. Breed influenced parameters related to the bleat duration, fundamental frequency disturbance (i.e., shivering, shimmering) and behavioural indices including success index during an agonistic intersection and proportion of related affiliative behaviours. The study showed that changes in group composition can affect the emotional state of animals providing information for better handling practices with regard to improving welfare.