Impacts of Livestock Preference and Frequency of Grazing on Production and Nutritive Value of Pastures in Chile

Cattle are selective grazers since they only consume some plants or some parts of a plant from the pasture and avoid others. Grazing preference is affected by characteristics of the pasture such as the botanical composition, pasture surface height, herbage mass, phenological stage, digestibility, fibre content, protein and ash content. Three studies were conducted in southern Chile to determine how: 1) grazing preferences of dairy cattle was influenced by pasture mixtures and fertilisation; 2) grazing selectivity was related to tiller features; and 3) grazing leaf-stage influenced pasture quantity and quality. For the first study, fertilised pastures had higher herbage mass, pasture height, Bromus valdivianus, metabolisable energy and crude protein content and had lower fibre content. Grazing time (GT) and bite number (BN) were positively related to metabolisable energy, crude protein content, pre-grazing herbage mass and pasture surface height, explained by the contribution of Lolium perenne and B. valdivianus. For the second study, selective grazing was enhanced by pasture heterogeneity and tiller volume may have favoured grazing probability at a similar nutritive value. For the third study, pastures grazed at a 2.5 leaf-stage yielded a higher herbage mass than those grazed at 1.5 leaf-stage, while increasing leaf-stage decreased pasture quality. Integration of the information on grazing preference and selectivity, and grazing frequency will help to refine grazing management for southern Chile