According to FAO statistics the largest contributors to greenhouse gas emissions in agriculture in 2012 were:
o Animals ruminants (mainly cattle) with 40% CH4
o Ruminants faeces on the ground with 16% of N2O
o Synthetic fertilizers by 13%
o Management of animal by 7% N2O
According to FAO, while transport and industry that emit 84% of greenhouse gases in 2012 and the plan to reduce 60% in 2050, livestock emitting 16% of greenhouse will increase its emissions to 40% in by the year 2015. For this reason, livestock farming needs special attention on climate change.
It is believed that carbohydrates used as feed to cattle produce less methane than forage diets. The effects are clear with 90% concentrate produce 2-3% CH4.
Wheat needed to concentrate can be used directly as human food as need a high amount of flour to feed the cows. Or can be used for chickens that produce less CH4. According the study, the amount of concentrate can be reduced without reducing production or CH4 growth through increased forage quality which does not affect the rumen microbial populations. (Nitrogen, carbohydrate, lipid studies, Pekka Huhtanen)
According to a metastudy between cows rumen ammonia and urea milk, urea in milk unit are lower compared with the manipulation of the diet version. Rumen ammonia and urea milk are positively associated with dietary digestion.
Other studies show that low CH4 production per unit are a conseguence of the increase of production, but the liberation of nitrogen per unit increases and this depends on the amount of conversion of nitrogen in N2O. In this way, greenhouse gases may not change but N2O emissions will increase.
Also, reducing ruminal degradibile protein may reduce the efficiency of nitrogen microbial synthesis leading to overall benefit of reducing protein ruminal degradibile less than expected.
General conclusions
o Potential reduction of CH4 from animal nutrition is limited.
o Increase of concentrates has increased cost and health problems while the wheat can be used directly as food for man.
o Increased protein supplements may reduce CH4 per unit product but increases the release of N and increasing the cost of food.
