Determination of the effects of breed and milk yield on carbon footprint in dairy cattle production

The purpose of this study was to compare Holstein and Simmental dairy farms having 100 lactating cows and different milk yields in terms of carbon footprint. For this purpose, using the same feeds, rations were prepared according to NRC norms, assuming that the Holstein yielded 20, 25, 30, and 35 kg milk per day, and the Simmental yielded 15, 20, 25, and 30 kg milk per day. It was assumed that there would be 20 dry cows in the farms and Holstein and Simmental cows would weigh 550 and 650 kg, respectively. 500 kg live weight was considered as one animal unit (AU) and for each breed, AU was calculated. When converting methane and nitrous oxide to carbon dioxide equivalents, the IPCC (2021) values of 27.2 and 273 were used. The carbon dioxide emissions per AU in the farm were the sum of emissions stemming from feed, enteric fermentation, methane from manure, CO2 from manure, N2O from manure, N2O from the barn, and anthropogenic sources. Holstein milk was standardized according to 3.62% fat and 3.11% protein, and Simmental milk was standardized according to 4.04% fat and 3.47% protein, and the amount of fat and protein corrected milk (FPCM) was found. Later the total live weight gain produced excluding cows was divided by FPCM to find the beef-to-milk ratio. In Holstein and Simmental farms, 81.75 and 75.75 % of the total greenhouse gas emissions were allocated to milk, and 18.25 and 24.25% to meat, respectively. Emissions stemming from enteric fermentation and feed had the highest share in total emissions, respectively. The average carbon footprint of 1 kg FPCM milk for Holstein cow yielding 20, 25, 30, 35 kg/d was 1.04 CO2-eq, whereas the average carbon footprint of 1 kg FPCM milk for Simmental cow yielding 15, 20, 25, 30 kg/d was 1.25 CO2-eq. It was found that as milk yield increased, the carbon footprint for 1 kg of FPCM and meat decreased. This shows the importance of breed and milk yield in reducing the carbon footprint in dairy cattle production.