Livestock sustainability is a complex issue that encompasses many different factors. One of the key considerations is the size, system, and species of the animals being raised. The size of a farm or operation can have a significant impact on sustainability, as larger operations may have more resources and technology at their disposal to implement sustainable practices.

Systems of farming also play a role in sustainability. For example, grass-fed beef production is often considered more sustainable than feedlot beef production, as it allows the animals to graze on pasture and reduces the need for grain-based feed. Similarly, free-range poultry production is often considered more sustainable than factory farming, as it allows the birds to have more space and access to the outdoors.

The species of animal being raised also plays a role in sustainability. For example, ruminants such as cattle and sheep are known to have a larger carbon footprint than monogastrics such as pigs and chickens. However, this does not necessarily mean that ruminant production is inherently unsustainable, as sustainable practices such as regenerative agriculture can be implemented to reduce the environmental impact.

In conclusion, the size, system, and species of livestock farming are important factors to consider when evaluating the sustainability of an operation. It is important to note that no one size fits all and sustainable practices vary according to the context. It is important to consider the whole farm systems and evaluate the trade-offs, opportunities and challenges of different practices and choices.