Water footprints and efficiencies of ruminant animals and products in China over 2008-2017

Over half of global livestock-related water consumption is for ruminants. Securing the increasing demand for ruminant products and their nutritional supply worldwide, especially in developing countries with limited and scarce water resources, poses new challenges. However, the evaluations of water appropriation (i.e., water footprints) and efficiencies of ruminant animals and products in time and space within large developing and populous countries remain unclear. Taking three ruminant animals (beef cattle, cows, and mutton sheep) and their meat and milk products produced within the most populous developing country, China, over the period 2008–2017 as the study case, we estimate and analyse provincial water footprints (WFs) by colours as well as their efficiencies from both perspectives of water and nutrients. The results show that the national average unit WFs decreased across species of ruminant. The northern provinces had higher unit WFs of three ruminants than the southern provinces. The WFs of beef were higher than those of the other ruminant animal products. Feed crops contributed 99% of the consumptive WFs of ruminant production in China. The water use efficiency for growing feed crops of the three ruminants increased in most provinces during the study period, which led to decreased proportion of inefficient WF of three animal products. The nutrition conversion efficiency of some animal products is found to overcome the well-known gaps between the WFs for a unit nutrient from animal products versus crops. For example, although the WF of fat per kilogram of mutton was triple of its ingested feed crops, the fat content can increase by six times when the feed crops were converted to mutton. This study reveals the necessity of evaluating the environmental impact of ruminant products from the dual perspectives of resource utilization efficiency and nutrient conversion efficiency, with a feasible evaluation method.