Impact Assessment of Dairy Cow Diets on Greenhouse Nitrogen Emissions

Abstract

The livestock sector represents a significant source of gaseous emissions that contribute to global warming. Although the primary gases emitted are carbon dioxide and methane, nitrogen compounds are being studied with increasing relevance due to their prolonged atmospheric presence and direct warming potential, as well as the damage they cause to the environment and living beings. In livestock, the major impact of these compounds is associated with excreta, which are directly related to the feeding of ruminants. This research compared two similar dairy production systems over five consecutive days, both using Holstein cows but with differences in the composition of the diets provided. Various components in urine, feces, and milk were evaluated, revealing similarities and some variations not only within the same herd but also between them. In both groups, the results for the nutritional indicator Milk Urea Nitrogen (MUN) were above optimal values (24.06 mg/dl and 25.49 mg/dl), indicating an excess of protein in the diet and consequent reproductive problems in the animals. Additionally, a nitrogen balance was conducted, showing different values between the two herds, which could suggest some interference of the diets with the urine excretion marker. In conclusion, adequate and balanced nutrition is crucial to prevent excess protein in the diet, which can affect both the health and reproduction of ruminants as well as the environment.