A linear programming model to optimize diets in environmental policy scenarios Moraes, L.E. et al. (2012) Katarina Nielsen Dominiak Department of Large Animal Sciences
Department of Large Animal Sciences Introduction Global food demands increase -> more animal products will be produced Carbohydrate fermentation (from forage) in dairy cattle produces CH 4 Protein, starch and minerals in feed can lead to excretion of N and minerals if fed at higher levels than animal requirements 72% of total emitted CH 4 in Brazil was from enteric fermentation (1994) K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Introduction Greenhouse gas (GHG), NO 3 -, and minerals contaminate the environment Policies and legislations formulated to limit environmental impacts of livestock production - Clean Water Act (US EPA 2003) - Manure applied to crops and pastures at levels the plants can extract (Nitrate,Phosporous) - Kyoto Protocol reduces GHG to level of 1990 - Carbon markets in Europe (and the States) K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Problem Mandatory carbon (CH 4 ) emission policies might be the future Two policies are discussed: - Limit the quantity of CH 4 emitted - Require emission taxes A precise diet formulation and balance will meet BOTH animal nutritient requirements AND decrease environmental impacts of animal agriculture K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Aim Reduce CH 4 emission and excretion of N and minerals Optimal diet cost and feed selection Joint optimization of costs and emisions+excretions Linear programming: A method to achieve best outcome given certain constraints Constraints are represented by linear relationships K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Three scenarios – three models BASEM: Cheapest possible feed – No GHG policies (baseline) Decision variables: Constraints: Available feed Nutrient requirements and their costs Defined feed limits Fibre proportions TAXM: Effect of tax on diet costs and composition, emission and excresion Computes optimal feed input mix that balances off tax savings for lower emissions REDM: Feed costs vs emission and excresion if forced to reduce CH 4 emission Decision variables like BASM but with the extra constraint K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Assumptions � � � � � K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Assumptions � � � � �� � � � � �� kg/kg DM $/kg DM � � � � �� Locally collected K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Prediction of emission and manure production How much is emitted? ~55 MJ/kg CH � Feed composition – absorbstion � Excrete composition K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Objective functions BASEM and REDM j = feed x = amount of feed (kg of DM) c = cost of feed K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Objective functions TAXM j = feed x = amount of feed (kg of DM) c = cost of feed CH � e = expected emission (tonnes) p = tax price per tonne K.N. Dominiak, AQMHM 2015
Constraints Other Limits, 1 Diet. Feet Limits Nutrient req . DMI Diet. Barley Limits Other Limits, 2 Diet. Forage Proportions Methane Restrictions Dias 12
Department of Large Animal Sciences Nutrient requirement constraints Amount Requirement 7 x 14 = 98 equations Nutrient content j = feed a = cow category (7 kinds) i = nutrient (14 kinds) K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Dietary feed limits constraints �� = � �� � � �� ∙ � � �� ��� 7 x 10 = 70 equations j = feed a = cow category (7 kinds) l = limit (for 10 kinds of j ) K.N. Dominiak, AQMHM 2015
Methane Restriction constraints (REDM) Total feed Max. (all cows, all feed) Emission Methane reduction (%) 1 - CH � BASEM emission emission predictions Dias 15
Department of Large Animal Sciences Results TAXM CH � Cost of reducing emission through the diet > tax costs Therefore: CH � No differences in emission between BASEM and TAXM K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Shadow prices Sensitivity analysis ‘What is the cost of reducing 1 tonne of CH 4 emission?’ Extremely sensitive to feed prices – further analysis required K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Results REDM 5% 19,1% 48,5% CH � emission reduced but diet costs increased K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Results – trade offs in diet formulas Because forage = NDF (lignin, cellulose, hemicellulose) And grain/soy = ME (protein, starch, minerals) The model results in a trade off between the two types But at what consequences? K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Results – trade offs in diet formulas Consequences of CH 4 reduction Feed ME NDF N+min ex Corn silage Low High Low Soy silage High Low High Grain High Low High Cereal High Low High Soybean meal High Low High Total reduction in DMI K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences Discussion Animals vs Human in competition for feed ressources ‘N + mineral excresions follows same pattern as intake’ - results in conflicting environmental interests CH 4 vs NO 3 Should mineral diets be based on excresion levels? K.N. Dominiak, AQMHM 2015
Department of Large Animal Sciences What about the cow? Consequences of CH 4 reduction Feed ME NDF N+min ex Corn Low High Low silage Soy silage High Low High Grain High Low High Cereal High Low High Soybean High Low High meal Total reduction in DMI K.N. Dominiak, AQMHM 2015
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