Preferences of sheep grazing down conterminal monocultures of Lolium perenne–Festuca arundinacea: Test of an energy intake rate maximisation hypothesis using the short-term double weighing technique Sophie Prache * , Julio Cesar Damasceno 1 Unite ´ de Recherches sur les Herbivores, INRA Clermont-Ferrand/Theix, 63122 St Gene `s Champanelle, France Accepted 4 August 2005 Available online 6 October 2005 Abstract We tested an energy intake rate maximisation hypothesis to predict preferences. In experiment 1, five groups of INRA401 dry ewes (G1–G5) grazed down conterminal mono- cultures of Lolium perenne (L)–Festuca arundinacea (F), 0.50:0.50 by area, at a stocking rate of 92 ewes ha À1 . Both plant species were 220-mm high at the beginning of grazing. Time spent grazing either L or F was measured daily from dawn to dusk in groups G1, G2, G4 and G5, composed of six ewes, using automated cameras. In experiment 2, intake-rate from L and F was measured over two periods (P1 and P2) on a group of 8 dry INRA401 ewes (G3), using the short-term double weighing technique. The four ewes that grazed L in P1 grazed F in P2 and vice versa. Sward height at the beginning of grazing was 220-mm high for both plant species in P1, and 195 and 156mm for L and F, respectively, in P2. Time spent grazing either L or F was measured during P2. During the first 5 days of the grazing down, ewes spent on average 71% of their grazing time on L. A marked switch to F occurred on day 6 on average. Thereafter, there was no more preference for www.elsevier.com/locate/applanim Applied Animal Behaviour Science 97 (2006) 206–220 * Corresponding author. Tel.: +33 4 73 62 40 63; fax: +33 4 73 62 41 18. E-mail address: prache@clermont.inra.fr (S. Prache). 1 Present address: Departamento de Zootecnia, Universidade Estadual de Maringa, Avenida Colombo, 5790 Maringa, Parana, Brazil. 0168-1591/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2005.08.002