| Popis: |
In this thesis I summarise and discuss the results of studies regarding motivational aspects on feeding behaviour in dairy cows. Questions addressed concern how feeding duration and rumen fill in cattle influence some behavioural variables reflecting frustrated feeding motivation, such as stereotypies and behaviours related to feed-searching, and also how rumen fill and feeding duration relate to oxytocin and cortisol. We have also investigated if operant conditioning is a useful method to measure and quantify the motivational strength to obtain roughages with different characteristics and sensory qualities. The aim was to test the hypothesis that oral manipulation of feed is a behavioural need in cattle, irrespective of rumen load. Low rumen content and long eating time had the effect that the cows spent a rather short time with behaviours related to feed-searching and showed low levels of stereotypies. The cows with long eating time had a larger oxytocin release during the afternoons compared with the cows with short eating time. The cows with high rumen content and short eating time spent relatively more time with behaviours related to feed-searching and with stereotypies. The cortisol concentration in the morning sampling period was higher in the treatment with short eating time compared with the cows with long eating time. The studies with operant conditioning showed large individual differences between cows in their motivation to work for feed in general. The results also showed that cows have individual preference for one specific side. It can be concluded that oral manipulation of feed is a behavioural need in cattle irrespective of rumen load. A short duration of feeding behaviours combined with a low rumen load seriously impairs the welfare of cattle. The results imply that there are physiological mechanisms, possibly in the form of oxytocin, involved in the motivation of feeding. I also conclude that operant conditioning could be a fruitful method to measure and quantify feed preference of dairy cows. However, the results only reflect the preference of the individual animal, and a complete mapping according to side preference must be done of each individual included in the experiment. The practical implication of these studies is to provide all cows with sufficiently long eating time, preferably by constant access to roughage. |
