Sustainability in UK dairy farming is no longer secured by traditional management focused on production of commodities. Society awareness, legislations and competing markets demand farming systems which can deliver multiple attributes such as: clean environment, high biodiversity, picturesque landscapes, good animal welfare and high quality of product and soil. Changes in management and introduction of new animal and plant varieties are likely to be the key elements to improve the sustainability of dairy farming systems. Although the effect of farm management on some attributes of sustainability (e.g. effect of fertiliser rates and timing on environmental losses) has already been studied, the impacts and scope for realising goals of agricultural multifunctionality through genetic changes in either plants or animals are still to be tested. Moreover, there is a need to develop approaches that can integrate these concepts to practical actions and decisions. SIMSDAIRY is a new farm level modelling framework which brings all of this complexity into an operational and scientific modus operandi. This paper provides a brief description of the SIMSDAIRYs structure and an example of how SIMSDAIRY can be used to compare the scope to improve the overall sustainability of a dairy farm by: (i) future system changes aimed at improving genetic characteristics of plant and animal with (ii) current system structural changes aimed at improving nutrient management efficiency. In order to do this comparison management factors and new genetic traits from plants or/and animals, acting singly, or in combination, are evaluated against a baseline dairy farm scenario. Sustainability is measured in terms of targets associated to: (i) Nitrates Directive, (ii) P threshold for eutrophication, (iii) Kyoto Protocol (iv) Gothenburg Protocol, (v) an adequate net farm income for standard living and acceptable standards of (vi) quality of milk, (vii) animal welfare, (viii) level of biodiversity, (ix) landscape aesthetics and (x) soil quality. Results suggest that genetic-based changes offer greater scope than management-based ones to improve sustainability up to an acceptable level. Costs associated to management changes are often too high within current socio-economics circumstances. Optimising N mineral fertiliser rate and timing was the only management-based measure that, while improving most of the environmental and biodiversity indices, resulted in improved economic results. Some genetic-based changes offered substantial scope for improving environmental losses while having economic benefits. However, only those decreasing the CP of the plant and increasing the diet N cow partition into milk seemed to both not result in significant pollution swapping and be achievable in the nearby future.