Developmental aspects of motivated behavior in domestic animals.

Biological functions like health, reproduction or the performance of specific behavior programs change over time. Therefore, their actual significance can only be understood fully if their history or development is well known. This point is illustrated with respect to behavior patterns in farm animals. Early life or ontogenetic processes strongly determine (sub)adult behavior. Prepuce suckling performed by group-housed veal calves during the age of 2 to 8 wk depends on sucking experience of the same calves during their first week of life. Restless behavior of fattening pigs is largely determined by rearing conditions in the first weeks of life. Disturbed behaviors like stereotypies develop out of conflict behaviors (biting, escape, etc.), as is the case in tethered sows. These stereotypies appear to promote the release of endorphins. In veal calves, different stereotypies (biting or licking the crate and tongue playing) develop during different periods of time and probably are related to different sorts of conflicts experienced by the developing calf. Tongue playing shows a specific relationship with abomasal ulcers. In veal calves, individual coping differences are observed that strongly parallel those described in other vertebrates (rats, dogs, men).