Trade-offs of approaches to mitigate N-excretion by dairy farms Jan Dijkstra Animal Nutrition Group, Wageningen University, The Netherlands Innovative and practical management approaches to reduce nitrogen excretion by ruminants
Key role of ruminants in human food production Ruminants convert human inedible plant resources into high quality human edible food Return on human edible protein input > 1 Source Country Dairy Baldwin (1984) USA 1.8 CAST (1999) Kenya South Korea 14.3 Dijkstra et al. (2013) Netherlands 3.4 Return: output human edible products / human edible input feed
Risks surplus of N in dairy production Ammonia small particles (PM 2.5 ) lung problems acidification soil fertility and tree vitality problems Nitrate pollution of drinking water health risk eutrophication algae growth, toxins Nitrous oxide greenhouse gas climate change Urinary N far more vulnerable to evaporative/leaching losses than faecal N 3
Trade-offs of dietary N mitigation approaches Various dietary strategies to reduce N excretion in faeces and urine exist Affect feed value, intake, digestibility, production Focus on N may have implications for other pollutants methane; minerals; etc 4
This presentation Evaluate implications of dietary measures to reduce N losses on methane production of dairy cattle N mitigation options Methane mitigation options Consequences N mitigation options for methane production 5
N in faeces (g/d) N in urine (g/d) N intake is principal driver of N excretion Reduce dietary N input N faeces = 10 9 + 0.28 0.023 N intake N urine = 20 20 + 0.38 0.039 N intake N intake (g/d) N intake (g/d) dairy cattle (n = 470) Kebreab et al. (2010) 6
Milk N efficiency Ratio of milk N to N intake adjusted for study N intake is principal driver of N excretion Reduce dietary N input N efficiency = 0.39 0.048 0.00466 0.00145 N content Y = 0.39 (SE, 0.048) -0.00466 (SE, 0.00145) X 0.30 0.25 0.20 0.15 20 25 30 35 40 45 Nitrogen concentration in diet, gn/kg DM Dietary N content (g/kg DM) dairy cattle (n = 470) Kebreab et al. (2010)
Energy flow (MJ/d) Improved feed efficiency at higher production levels # k g m i l k / k g fe e d 400 M i l k 300 He a t i n c re m e n t m i l k p ro d u c ti o n Fa e c e s, u ri n e, g a s M a i n te n a n c e 200 100 0 0 0 3,000 6,000 9,000 12,000 Milk production (kg/year) Dijkstra et al. (2013)
Energy flow (MJ/d) Improved feed efficiency at higher production levels 400 # k g m i l k / k g fe e d M i l k 1.53 300 He a t i n c re m e n t m i l k p ro d u c ti o n Fa e c e s, u ri n e, g a s M a i n te n a n c e 1.17 1.40 200 0.78 0 100 0 0 3,000 6,000 9,000 12,000 Milk production (kg/year) Dijkstra et al. (2013)
Milk production (kg F PCM/cow/yr) N efficiency Production level and N efficiency Improve utilization of dietary N to milk protein 9000 0.30 0.25 8000 0.20 7000 Milk production 0.15 6000 N efficiency 0.10 1990 1995 2000 2005 2010 Year dairy cattle, Netherlands Bannink et al. (2011)
Dietary N concentration (g/kg DM) Feed efficiency (kg FPCM/kg DM) Production level and N efficiency Improve utilization of dietary N to milk protein 32 1.30 Reduced N in excreta 1.25 28 70% due to lowering dietary N content 1.20 30% due to improved feed efficiency 1.15 24 N content diet 1.10 feed efficiency 1.05 20 1990 1995 2000 2005 2010 Year dairy cattle, Netherlands Bannink et al. (2011)
Energy supply reduces urinary N losses Faecal N excretion: no effect of ME intake Urine N (g/d): 20 + 0.38 N-intake 48 + 0.56 N-intake -71.4 ME-intake dairy cattle (n = 470) Kebreab et al. (2010)
This presentation Evaluate implications of dietary measures to reduce N losses on methane production of dairy cattle N mitigation options dietary N supply dietary energy supply production level Methane mitigation options Consequences N mitigation options for methane production 13
Milk production (kg F PCM/cow/yr) Methane production (g CH 4 /kg FPCM) Production level and methane emission Methane estimated with Tier 3 method 9000 18 Reduced methane production 17 15% due to lower CH 4 per kg feed 8000 85% due to improved feed efficiency 16 7000 Milk production 15 6000 CH 4 production 14 1990 1995 2000 2005 2010 Year dairy cattle, Netherlands Bannink et al. (2011)
Production of methane degradation PLANT MATERIAL GLUCOSE Shift from fermentation to digestion (starch, protein, fat) ACETATE BUTYRATE PROPIONATE +4 +2 2 HYDROGEN CO 2 Shift from acetate or METHANE butyrate to propionate
Methane (mmol/mol VFA) Chemical composition affects methane 400 +8% 300 200 100 30% 36% Meta-analysis stoichiometric methane and VFA Bannink et al. (2006) 0 Fibre Starch Sugars Protein
Methane (g/kg dig. OM) Methane (g/kg growth) Concentrate level affects methane 40 Maize silage Barley silage Maize Barley 150 30 100 20 10 50 0 Methane (g/kg dig. OM) Methane (g/kg growth) 0 beef heifers; n =16 Beauchemin and McGinn (2005)
This presentation Evaluate implications of dietary measures to reduce N losses on methane production of dairy cattle N mitigation options Methane mitigation options feed efficiency dietary fibre (bypass) protein/starch/fat Consequences N mitigation options for methane production 18
Feed efficiency Large potential of feed efficiency improvement to reduce excretion of waste in particular methane reduction Dietary N mitigation should not negatively affect feed efficiency
Low protein diet may impair production Diet CP concentration (g/kg DM) 114 144 173 Intake (kg DM/d) 16.5 18.0 18.6 Milk (kg FPCM/d) 25.7 31.0 34.5 N intake (g/d) 300 414 515 Milk N output (g/d) 126 160 179 Milk N efficiency 0.423 0.391 0.350 Feed efficiency 1.56 1.72 1.85 Dairy cattle 1 to 150 DIM Law et al. (2009) Reduced feed efficiency likely increases CH 4 per kg milk
CH 4 production (mg CH 4 /kg LW/d) N reduction high roughage diets 600 500 400 300 200 100 0 Grass 70 kg N/ha Grass 270 kg N/ha Day 1 Day 2 Day 3 Day 4 4-day grazing sheep, tunnels Murray et al. (2001)
Methane production (g/kg feed DM) Grass N content and methane production 30 25 20 15 Reading Lelystad Wageningen 25 30 35 40 45 50 55 Dietary N to OM ratio (g/kg) Respiration chamber technique Grass 68-94% of total diet DM n = 98 cows Closed symbols: observed Open symbols: predicted Tier 3 Bannink et al. (2010)
Simulations Tier 3 model: nutritional strategies Mechanistic model of Bannink et al. (2011) Evaluated 40 different diets Grass silage management high or low fertilised (350 or 150 kg N/ha/yr) early or late cut (3000 or 4500 kg DM/ha) Concentrate level 20% or 40% Part of silage replaced: straw; beet pulp; corn silage; potatoes
Methane production (g/kg milk) Negative relation N excretion and methane production 18 16 14 12 10 y = 18.1-0.243x r² = 0.218 8 8 10 12 14 16 18 N excretion (g/kg milk) Dijkstra et al. (2011)
Methane production (g/kg milk) Negative relation N excretion and methane production 18 16 14 12 10 y = 20.6 10.3x r² = 0.516 8 0,3 0,4 0,5 0,6 0,7 Ratio urinary N : total manure N excretion Dijkstra et al. (2011)
Methane production (g/kg milk) Negative relation N excretion and methane production 18 16 14 12 10 high fertilized, early cut grass 8 8 10 12 14 16 18 N excretion (g/kg milk) Dijkstra et al. (2011)
Methane production (g/kg milk) Negative relation N excretion and methane production 18 16 14 12 10 8 maize silage diet 8 10 12 14 16 18 N excretion (g/kg milk) Dijkstra et al. (2011)
N reduction: trade-off N 2 O and CH 4 Simulations: 1 g of manure-n less results in increase of 0.24 g CH 4 N 2 O emission using IPCC guidelines direct N 2 O from manure management (housing, storage, manure application) Indirect N 2 O related to N leaching and NH 3 emission GWP: CH 4 25; N 2 O 298 Estimated N 2 O reduction 5.8 g CO 2 e Estimated CH 4 rise 6.0 g CO 2 e Lowering farm N surplus may not reduce GHG
Relative excretion or costs (base = 100%) CH 4 reduction increases N excretion and diet costs 150 125 100 75 50 25 N excretion Diet costs 0 CH 4 base CH 4-5% CH 4-10% CH 4-14% Linear programming minimum cost diet model Moraes et al. (2012)
Conclusions: N and CH 4 trade-offs Feed efficiency improvement will reduce both N and CH 4 excretion per unit milk low protein diets may feed efficiency Reduced diet N content may coincide with CH 4 N content concentrate: CH 4 unchanged N content roughage: CH 4 relation urinary N - CH 4 of particular concern focus on reduced N and CH 4 : $$$ large variation: go for win-win Trade-off between N and CH 4 at animal level essential to allow evaluation at whole farm level
Acknowledgements André Bannink and Jennifer Ellis Wageningen University NL Ermias Kebreab University California, Davis USA James France University Guelph Canada Chris Reynolds University Reading UK
This presentation has been carried out with financial support from the Commission of the European Communities, FP7, KBB-2007-1. It does not necessarily reflect its view and in no way anticipates the Commission s future policy in this area. Innovative and practical management approaches to reduce nitrogen excretion by ruminants