Effect of breed of cattle and season on diet selection and defoliation of competitive plant species in semi-natural grasslands A. Hessle*, J. Wissman†, J. Bertilsson‡ and E. Burstedt§ *Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Skara, Sweden, †Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden, ‡County Administration Board of Va ¨stra Go ¨taland, Skara, Sweden, and §Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Uppsala, Sweden Abstract To maintain biodiversity in semi-natural grasslands, the choice of breed of livestock and season of grazing can be important. The objective was to determine the effects of breed and season on the composition of plant fragments in the faeces of cattle grazing a heterogeneous semi- natural grassland. Twelve heifers of the traditional Swedish Va ¨neko breed (live weight 309 kg) and twelve heifers of the Charolais breed (live weight 431 kg) were allocated to three pastures per breed. Faeces samples were collected in spring, summer and autumn for micro-histological examination of plant fragments. On the same occasion, defoliation of four competitive plant species was recorded. Faecal plant fragments mainly consisted of grasses but also herbs, whereas Cyperaceae, despite their abundance on the pastures, only com- posed a small proportion of fragments. Season affected the composition of plant fragments in the faeces, with a higher proportion of Cyperaceae and herbs in spring than later in the grazing period (P <0Æ001), and the heifers ingesting more grasses and woody plants in autumn. In spite of a clear difference in live weight between the two breeds, no effects of breed on the composition of plant fragments in faeces were observed, although Va ¨ neko heifers defoliated more Filipendula ulmaria in spring than the Charolais heifers (P <0Æ01). In addition, defoliation of Alnus glutinosa increased later in the grazing period (P <0Æ05), especially for the Va ¨ neko heifers, indicating control of pernicious brush- wood by grazing may be more effective in autumn. Keywords: biodiversity, cattle, diet composition, defo- liation, grazing management, semi-natural grasslands Introduction The semi-natural grasslands of northern Europe have a wide diversity of plant and animal species of which a number are under threat of loss (Smart et al., 2000; Bernes, 2001; Luoto et al., 2003). The largest threat to grassland diversity is from the cessation of grazing. In areas where a decrease in the grazing of grasslands is forecasted, there is a need to develop strategies of grazing management that maintain the biodiversity of semi-natural grasslands. In addition to factors, such as live weight and previous grazing experience, breed of livestock has often been suggested as a tool for obtaining specific grazing effects (Rook et al., 2004; Van Wagoner et al., 2006). Historically in Europe, forests and marginal grasslands with nutrient-poor vegetation were gener- ally used for grazing (Myrdal, 1998). Therefore, it is possible that certain adaptive foraging traits in livestock may differ between traditional breeds developed in nutrient-poor environments and breeds developed in more fertile environments and under intensive produc- tion systems (Sæther and Vangen, 2001; Rook et al., 2004). A less selective diet is synonymous with an increased proportion of plant species generally avoided for defoliation. Plant species avoided in grasslands, such as a number of species of rough grasses, Cyperaceae and brushwood species, are often competitive and this may lead to a reduction in the biodiversity in species-rich grasslands. Therefore, defoliation of competitive species is desirable when managing semi-natural grasslands. Using specific types of livestock may be one way to control their spread (Steinheim et al., 2005; Sæther et al., 2006; Scimone et al., 2007). Previous studies have also demonstrated that cattle grazing can be more Correspondence to: A. Hessle, Department of Animal Envi- ronment and Health, Swedish University of Agricultural Sciences, PO Box 234, 532 23 SE Skara, Sweden. E-mail: anna.hessle@hmh.slu.se Received 15 June 2007; revised 1 November 2007 Ó 2008 The Authors Journal Compilation Ó 2008 Blackwell Publishing Ltd. Grass and Forage Science, 63, 86–93 86