Trade-offs of approaches to mitigate N-excretion by dairy farms

Transcription

1 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

2 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

3 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

4 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

5 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

6 N in faeces (g/d) N in urine (g/d) N intake is principal driver of N excretion Reduce dietary N input N faeces = N intake N urine = N intake N intake (g/d) N intake (g/d) dairy cattle (n = 470) Kebreab et al. (2010) 6

7 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 = N content Y = 0.39 (SE, 0.048) (SE, ) X Nitrogen concentration in diet, gn/kg DM Dietary N content (g/kg DM) dairy cattle (n = 470) Kebreab et al. (2010)

8 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 ,000 6,000 9,000 12,000 Milk production (kg/year) Dijkstra et al. (2013)

9 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 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 ,000 6,000 9,000 12,000 Milk production (kg/year) Dijkstra et al. (2013)

10 Milk production (kg F PCM/cow/yr) N efficiency Production level and N efficiency Improve utilization of dietary N to milk protein Milk production N efficiency Year dairy cattle, Netherlands Bannink et al. (2011)

11 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 Reduced N in excreta % due to lowering dietary N content % due to improved feed efficiency N content diet 1.10 feed efficiency Year dairy cattle, Netherlands Bannink et al. (2011)

12 Energy supply reduces urinary N losses Faecal N excretion: no effect of ME intake Urine N (g/d): N-intake N-intake ME-intake dairy cattle (n = 470) Kebreab et al. (2010)

13 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

14 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 Reduced methane production 17 15% due to lower CH 4 per kg feed % due to improved feed efficiency Milk production CH 4 production Year dairy cattle, Netherlands Bannink et al. (2011)

15 Production of methane degradation PLANT MATERIAL GLUCOSE Shift from fermentation to digestion (starch, protein, fat) ACETATE BUTYRATE PROPIONATE HYDROGEN CO 2 Shift from acetate or METHANE butyrate to propionate

16 Methane (mmol/mol VFA) Chemical composition affects methane % % 36% Meta-analysis stoichiometric methane and VFA Bannink et al. (2006) 0 Fibre Starch Sugars Protein

17 Methane (g/kg dig. OM) Methane (g/kg growth) Concentrate level affects methane 40 Maize silage Barley silage Maize Barley Methane (g/kg dig. OM) Methane (g/kg growth) 0 beef heifers; n =16 Beauchemin and McGinn (2005)

18 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

19 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

20 Low protein diet may impair production Diet CP concentration (g/kg DM) Intake (kg DM/d) Milk (kg FPCM/d) N intake (g/d) Milk N output (g/d) Milk N efficiency Feed efficiency Dairy cattle 1 to 150 DIM Law et al. (2009) Reduced feed efficiency likely increases CH 4 per kg milk

21 CH 4 production (mg CH 4 /kg LW/d) N reduction high roughage diets 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)

22 Methane production (g/kg feed DM) Grass N content and methane production Reading Lelystad Wageningen 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)

23 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

24 Methane production (g/kg milk) Negative relation N excretion and methane production y = x r² = N excretion (g/kg milk) Dijkstra et al. (2011)

25 Methane production (g/kg milk) Negative relation N excretion and methane production y = x r² = ,3 0,4 0,5 0,6 0,7 Ratio urinary N : total manure N excretion Dijkstra et al. (2011)

26 Methane production (g/kg milk) Negative relation N excretion and methane production high fertilized, early cut grass N excretion (g/kg milk) Dijkstra et al. (2011)

27 Methane production (g/kg milk) Negative relation N excretion and methane production maize silage diet N excretion (g/kg milk) Dijkstra et al. (2011)

28 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

29 Relative excretion or costs (base = 100%) CH 4 reduction increases N excretion and diet costs 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)

30 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

31 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

32 This presentation has been carried out with financial support from the Commission of the European Communities, FP7, KBB 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