Cattle grazing on semi-natural pastures : animal behaviour and nutrition, vegetation characteristics and environmental aspects

Sammanfattning: The knowledge of the grazing behaviour of cattle on Swedish semi-natural pastures and how this relates to the nutritional quality and quantity of the vegetation is low. In a situation where farming is being intensified both nationally and globally, it is important to gain more information about semi-natural pastures and how to utilise this resource properly. The aims of this thesis was to: (1) examine the grazing, resting and fouling behaviour of cattle on grazing areas mainly dominated by semi-natural vegetation which also includes portions of grassland affected by fertilisation; (2) determine the nutrient content and seasonal herbage production of different vegetation types within semi-natural pastures; (3) determine the in vivo digestibility of forages from different vegetation types in heterogeneous semi-natural grasslands; (4) study the division of nitrogen between faeces and urine and the enteric methane production from cattle fed these same forages. One field and one indoor study were carried out. The field study covered three grazing seasons and included measurements of both cattle behaviour and of the nutritional properties of semi-natural pasture vegetation. Cattle preferred to graze, rest, urinate and defecate on previously fertilised areas. The vegetation in these areas was characterised by a high energy and crude protein content and a high seasonal herbage production. The indoor study measured in vivo digestibility, methane production and the division of nitrogen between urine and faeces of different forages from semi-natural grasslands fed to non-lactating cows and heifers. Forage digestibilities were lower than what is commonly reported for cultivated forages. Digestibilities did not differ between treatments, with the exception of a lower digestibility in the heifer group when fed of vegetation harvested on shore meadows compared with vegetation from naturalised cultivated grasslands. Methane production did not differ among forages. In conclusion, cattle prefer to graze in previously fertilised areas, but other vegetation types were also utilised by the animals. Furthermore, in vivo digestibility of semi-natural pasture vegetation was similar to in vitro values obtained with the standard Swedish method for estimating the energy value of forages.

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