Ingestive behaviour and performances of dairy ewes part-time grazing Mediterranean forages

Part-time grazing,i.e. restricted time access to pasture, is widespread but its effects on ingestive behaviour and performance of dairy ewes are still overlooked. The objectives of this thesis were: i) reviewing the literature focused on the effects of part-time grazing on ingestive behaviour and performance of ruminants and horses; ii) assessing the effects of different time restrictions on the above variables in milked ewes grazingLolium multiflorumLam (experiment 1) andTrifolium alexandrinumL (experiment 2); and iii) modelling the results of the above experiments for predicting herbge intake. The review showed that part-time grazing of pastures by ruminants results in compensatory behaviours such as higher intake rate and grazing intensity and lower energy expenditures, which often bring about mild to nil performance losses as compared with time-unrestricted grazers. Horese are less able in this compensation than ruminants. The experiments on dairy ews compared 2, 4, and 6 h/d time access to pasture. Their results confirmed the general trend of ingestive behaviour, showing that giving access to a moderate quality Italian ryegrass for less than 6 h/d decreased intake and milk yield of ewes in mid lactation, whereas for berseem clover access could be as short as 4 h/d without any loss of intake and performance. The modelling of the data based on both stepwise and partial least square regressions provided good performance in validation and satisfactory sensitivity.