Reducing Greenhouse Gas Emissions in Dairy Cow Breeding Units through Ration Management with Emphasis on the Life Cycle Assessment Approach

Background: Global warming and the role of greenhouse gases in its creation are among the important topics investigated in many domestic and foreign studies.Livestock activities are among the factors that cause these gases.Therefore, to reduce the emission of greenhouse gases, necessary measures should be taken in livestock units.In this regard, in the present study, the optimal ration of dairy cows was determined with an emphasis on reducing greenhouse gas emissions in the form of a life cycle assessment.For this, the optimal ration was first determined with the economic goal of reducing costs, and then the ration was determined aiming at reducing greenhouse gas emissions in different scenarios of cost increase (5-25%) compared to the optimal economic state.To determine the optimal ration in this research, Holstein dairy cows with a weight of 600 kg and an average production of 30 kg of milk per day were considered in one of the large dairy cattle breeding units in Mazandaran province.In the present study, the amount of greenhouse gas emissions caused by animal feed was calculated in the form of the life cycle, the effects of both not burning plant residues and reducing the use of chemical fertilizers were investigated on the amount of greenhouse gas emissions in dairy cattle breeding units.Methods: The required data were collected from the sample dairy cattle breeding unit, the Agricultural Jihad of Mazandaran Province, the FAO website, the NRC book, and some other information sources.The used model includes the ration cost minimization model and the greenhouse gas emission minimization model in the form of life cycle assessment.GAMS software was used to calculate the results. Results:The results indicate that to minimize the cost of providing ration, sugar beet pulp at an amount of 15.83 kg per day is replaced by materials such as corn silage, wheat bran, wheat straw, and barley constitute the most part, respectively, with values of 7.91, 7.91, and 7.72 kg per day.On the other hand, it is necessary to limit the consumption of corn, fish meal, and soybean meal in the diet.The emission of greenhouse gases in this case is about 41.19 kg eq CO2.The total cost is also equal to 396,480 Rials, which is reduced by 26% compared to the basic state.The results of determining the optimal ration aiming at reducing greenhouse gas emissions indicate that sugar beet pulp, corn silage, wheat bran, and wheat straw with values of 15. 67, 9.17, 7.84, and 7.84 kg per day, respectively, have the highest share in the scenario of a 5% increase in ration costs obtained in the previous method.In this situation, greenhouse gas emissions will decrease to a greater extent (around 7.7%) with a 5% increase in ration costs.If the cost of the total ration is increased by 25%, the emission of greenhouse gases will decrease by 25.68%.In this case, the largest portion of the ration will be sugar beet pulp, corn silage, and wheat bran with the values of 15.66, 15.71, and 6.37 kg per day, respectively.Overall, based on the results, materials such as corn silage, sugar beet pulp, and wheat bran have a higher share than the other materials by reducing greenhouse gas emissions in different cost scenarios.Soybean and cornmeal are also among the ingredients that are reduced in the diet to further reduce greenhouse gases.Based on the results obtained in all scenarios of cost increase, methane from rumen fermentation, energy consumption, manure management, and then soil management respectively have the most contribution to greenhouse gas emissions.Examining other scenarios of this research also indicates that not burning plant residues, which is now approved as a government policy, reduces