By Vet Emma Stuart
Cows have a bad reputation when it comes to climate change but a relatively new approach to measuring the impact of global greenhouse gas emissions (termed GWP*) suggests this might be an unfair school of thought.
Unlike carbon dioxide, methane is a short-lived greenhouse gas with a half-life of about a decade, which means that provided our ruminant population remains stable or even reduces in size, the methane cows are producing today is simply replacing what was produced 10-20 years ago. Interestingly, if we can reduce methane emissions from our cows, we could potentially induce a cooling effect because of methane’s impact on global temperatures.
So how can this be achieved in practice? Feed efficiency, or the amount of feed required to produce milk or meat, is one of the main drivers of on-farm emissions and should be your top priority. Many factors influence feed efficiency, including diet quality, breeding and husbandry, but animal health and fertility are also key.
Mastitis, lameness and infectious diseases affect intakes, productivity and overall efficiency as feed nutrients are directed towards the immune system instead of milk production. This will increase emissions per unit of milk output as methane production must be spread out over a lower daily yield. Poor fertility can also negatively impact your carbon footprint, underlying the importance of routine vet visits and fertility monitoring or benchmarking. As the lactation progresses, the efficiency with which cows convert feed into milk declines significantly, meaning herds with extended calving intervals and large numbers of cows in late lactation have a poorer feed conversion ratio. Moreover, these cows are at increased risk of being dried off too fat, leaving them more susceptible to metabolic conditions such as ketosis and fatty liver in the subsequent lactation. This will again impact productivity and feed efficiency, resulting in a vicious cycle of high emissions per unit of output.
Climate change is a complex issue with no simple solutions, but understanding what drives methane emissions on your farm can help equip you to do your part, while improving profitability through reduced costs and increased productivity.