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¡¡¡¡The producer's strategy within non-equilibrium systems is to move livestocksequentially across a series of environments _ exploiting optimal periods in each area they use _ Herd management must aim at responding to altemate periods of high and low productivity£¬ with an emphasis on exploiting environmental heterogeneity rather than attempting to manipulate the environment to maximize stability and uniformity £¨Behnke et al. 1993£¬ 14-15£©.¡¡¡¡More recently£¬ new interest is gathering around this dimension£¬ documented in work on pastoral systems in Kazakhstan£¬ where plant "phenology" is found to be the driving force for livestock mobility £¨Alimaev 2003; see also Kerven et al. 2006; Alimaev and Behnke 2007£©.¡¡¡¡Although variations in pasture quality have always been in the spotlight of the "new range ecology" as part of the ecological dynamics£¬ the dimension of transient quality within the life of fodder plants and its relation w:ith feeding selectivity in livestock-known to be pivotal to producers' strategies-has remained a marginal concem. A recent overview of the debate around the adequacy of equilibrium or non-equilibrium models to represent the ecology of the drylands£¬ still appears perfectly comfortable with quantitative notions of "1ivestock numbers' and "grazing pressure"£¬ and with a representation of pastoral mobility as a coping strategy against variability £¨Vetter 2005£©.¡¡¡¡Qualitative difference with regard to livestock has received even more limited attention. By and large£¬ non-equilibrium perspectives looking at livestock systems have focused on population dynamics of grassland and animals£¬ either in relation to management issues £¨Oba et al. 2000; Homewood et al. 2001; Anderies et al. 2002; Uphoff et al. 2006; on Niger£¬ Hiemaux 2000; Schlecht et al. 2000£© or as a consequence of environmental adaptation £¨i.e. different survival rate£© between breeds £¨Bayer and Waters-Bayer 1995; also Bayer 1989£©. Some of the studies in this direction have looked at the links between local breeds and herd-management practices in relation to range ecology£¬ touching upon herders' manipulation of animals' diet £¨Bayer 1990; 1986£©£¬ but without venturing into the analysis of such links in the context of the breeding systems.¡¡¡¡¡­¡­