Caratteristiche della comunicazione acustica e comportamento sociale in suinetti allo svezzamento

The present study aims to increase the information on the mechanism involved in the development ofthe hierarchy consequent to litters grouping and on the relationships among phonic behaviour and hierarchic state. 32 Goland hybrids piglets aged 28 days were used. An isolation test was performed in an anechoie cage immediately before animal mixing. Vocalisations were recorded and number of signals, signal length, maximum frequency, fundamental frequency and formants number analysed by means of an analogic Sonograph (Sona-Graph 5500. Kay Elemetrics Co). Afterwards, litters from 2 primiparous and 2 pluriparous sows were mixed to produce 2 experimental groups (l litter from a primiparous was mixed with l litter from a pluriparous sow for each group) and the social behaviour was observed. Gathered data were used to calculate the hierarchy in each group using 3 different hierarchic indexes (social) rank index, social tension index and dominance value). Results showed that sex and sow farrowing order did not affect hierarchy of piglets in both groups. A positive correlation between the 3 hierarchic indexes was found. The latter were also positively correlated with the live weight of the animals. Therefore, the heavier was the piglet the higher was its social rank within the group. Moreover, when the litters were mixed a higher number of tights was observed among piglets from different litters compared to littermates. Hierarchic indexes were also negatively correlated with signal length and fundamental frequency. Therefore, dominant animals tended to produce shorter signals with a peculiar sound characterised by a lower fundamental frequency. Possibly, animals with different social ranks produce signal with different phonic characteristics, thus allowing their hierarchic state to be recognised at distance. A better understanding of vocal behaviour may be useful to improve farm management