The impact on global warming of greenhouse gas emissions coming from farming is an area of ongoing debate. The most important greenhouse gas in the dairy industry is methane gas from cows. The greenhouse gas effect of cow methane is 34 times bigger than the greenhouse gas effect of CO2.

Estimates vary between sources, but according to FAO^[1], 14.5% of global greenhouse gas emission is related to farming (see Figure 1).

Reports indicate that 58% of cow methane emissions of a dairy farm are coming directly from cow methane, with the remaining 42% of greenhouse gas emissions resulting from farm operations (see Figure 2). Out of the total amount of cow methane production, 28% is the result of methane emission from manure and 72% is coming from enteric cow methane production in the rumen.

This means that enteric cow methane emissions are an important target for reduction of cattle methane emissions from a dairy farm. Pressure from dairy milk processors on farmers to reduce methane emissions is increasing. Targets to reduce enteric cow methane emission are typically in the order of 25%. More and more milk producers want to know how to reduce methane emissions from cattle.

There are feed additives to reduce methane emission with a direct effect on cows methane production. These feed additives to reduce methane influence the rumen fermentation process in such a way that a shift away from cow methane production occurs. The cow eats the same diet and produces the same amount of milk, but the amount of enteric cow methane emissions goes down.

There are feed additives with a direct effect on cow methane production in the rumen that have the ability to reduce cow methane emissions by greater than 25% These feed additives to reduce methane do however not increase milk production. As a result, they increase the cost per liter of milk produced on the farm.

Alternatively, there are feed additives that reduce methane from cows because they increase feed efficiency. The cow will continue eating the same amount of feed, with a fixed production of cow methane, but will produce more milk. As a result, the amount of cow methane produced per kg of milk goes down. This is an indirect effect on emission of methane gas from cows. Feed additives with an indirect effect on cow methane emission have the advantage that they do not increase the cost per liter of milk produced on the farm. In fact, they have the potential to reduce the cost per kg of milk produced, while reducing the emission of methane from cows.

A trial carried out by the Ohio State University^[2] showed that completely replacing sulfates trace minerals with Selko IntelliBond improves fibre digestion of dairy cows (see Figure 3). This has been confirmed in several peer reviewed studies^{[3,4,5,6,7,8]}. Each one point difference in NDF digestibility can increase milk production by 0.25 to 0.3 kg Energy Corrected Milk^[9].

Several trials^[10,11,12] have shown that Selko IntelliBond increases milk production in dairy cows (see Figure 4). With cows eating the same amount of feed and producing the same amount of cow methane, while producing more milk, cow methane production per kg of milk is being reduced. This is an indirect effect of Selko IntelliBond on cow methane emissions of a dairy farm.

All data required to support Selko IntelliBond’s ability to reduce cow methane emissions were compiled in a dossier, which was submitted to Dr. E. Kebreab, Professor at the University of California, Davis. The evaluation focused on the effect of replacing sulfate trace minerals with Selko IntelliBond trace minerals on cattle methane emissions. Professor Kebreab concluded that feeding Selko IntelliBond trace minerals reduces enteric cow methane emission by 1.5-2.0%. This makes Selko IntelliBond the world’s first trace mineral source that has officially been verified for the reduction of cow methane emission per kg of energy corrected milk.

How to reduce methane emissions from cattle with better management?

Cow methane emissions can be reduced by reducing the age at first calving, by increasing the production per lactation, by increasing the number of lactations per cow and by improving the health of the herd. If dairy cows calve at an earlier age, they produce less cow methane up to the moment they start producing milk. Research by the ILVO^[13] showed emission of methane from cows per kg of milk produced is reduced by 3.1% if the age at first calving the dairy herd is reduced by 2 months.

Dairy cows produce a fixed level of cow methane to produce energy for maintenance, regardless of their production level. If the amount of milk production per lactation goes up, the cow methane production for maintenance is “diluted” over more kilograms of milk. Increasing the milk production per day by 3 kg will reduce cow methane emissions per kg of milk produced by up to 8.4%[13]. If the number of lactations per cow goes up, a similar effect occurs; cow methane produced during the rearing phase is “diluted” over more lactations. If next to increasing milk production by 3 kg per day, the culling rate is reduced by 5%, emission of methane gas from cows per kg of milk produced will be reduced by 11.7%^[13].

If dairy cows are not healthy, feed efficiency is being reduced. The immune system of dairy cows uses a lot of energy which as a consequence cannot be used for milk production. It is estimated that 30% of the production potential of dairy cows is wasted because of health issues. This means that healthy dairy cows have lower cow methane emissions per kg of milk produced.

There is a connection between the 4 aforementioned parameters. The age at first calving can be reduced by an intensive rearing programme with high levels of milk feeding during the first 12 weeks of a calf’s life. It has been shown that such a programme also increases the milk production per lactation and the number of lactations per cow^[14], thus resulting in a reduction of cow methane. A good transition management programme for dairy cows will lead to a further increase of milk production per lactation and number of lactations per cow. As most of the health problems of dairy cows are related to poor transition, a good transition programme will also improve health. This will reduce the production of methane from cows on the dairy farm.

Reducing cow methane emission from manure

Next to reducing enteric cow methane emissions with feed additives to reduce methane emissions from cows, there is the option to improve cow methane capture in manure. Cows produce manure and urine separately, but once the 2 are mixed in the manure pit, a chemical reaction starts that results in the production of cow methane from manure. One way to reduce the production of methane gas from cows via their manure is to keep urine and manure as much as possible separated from each other. Next to that, there are feed additives to reduce methane from manure.

How to meet targets for reduction of cow methane emissions

How to reduce methane emissions from cattle while reaching targets that have been established by authorities and milk processors without increasing costs of milk production is certainly challenging. Reduction targets for cow methane emissions can’t be reached by switching to Selko IntelliBond only. However, the use of Selko IntelliBond is a positive, cost-effective step in the right direction. Meeting targets for reduction of methane from cows will require an integrated approach combining improvements in nutrition, cow management, cow comfort, cropping systems and manure management. Taken together these approaches, challenging targets for reduction of cattle methane emissions can be achieved, while preserving the financial well-being of the producer.