Optimal decisions in organic steer production a model including winter feed level, grazing strategy and slaughtering policy Bea Nielsen, LIFE / NOR-FEED A/S Advanced Herd Management, september 2007
Who am I? M.Sc. agriculture + Ph.D. June 2003 Organic beef production Feeding trials Questionnaire Registration of production results on-farm Model Since 2003/2004 employed at Nor-Feed A/S as R&D Manager Natural additives to production animals
Outline Organic steer production: background Decisions to be taken by the farmer Steer model: Model structure Presentation of the model Model conditions Results Criterion of optimality: per steer or per time unit? Price changes Perspectives
Dairy breed bull calves in organic beef production: Many organic dairy farms in DK milk is the primary income low number of organic bull calves reach the organic beef market what happens to the bull calves? Background Typical conventional production of bull calves in DK intensive production of young bulls / calves (about 1 year old) not suitable on organic farms What happens to the bull calves on the organic farms? why is it interesting to investigate? export of bull calves can be an ethical problem to organic farming bull calves are an unused resource on organic farms
What happens to the dairy bull calves? Results from a farm survey 6% 20% sold to conventional farms killed 8% 66% reared on farm of origin sold to organic farms
Why organic steer production? European organic standards 60% roughage (kg DM /animal / day) 150 days on pasture Production of young bulls or calves Steers castrated bulls calm temperament reduced gain intensive feeding is not necessary
Steer production Weight, kg 600 500 400 300 200 100 0 900 g/d 600 g/d Summer 1.1 1.5 1.11 1.5 1.11 1.1 Summer 614 kg 900 g/d 600 g/d 600 g/d Months 602 kg intensive extensive
Decisions to be taken Which pasture? marginal grass (low quality and gain) clover grass (high quality and gain) Feeding level in winter? low feeding level result in compensatory growth on pasture When should fattening start? Slaughter weight?
The steer model 4-level hierarchical Markov process with decisions defined at three levels child level 1: grazing strategy (marginal grass or clover grass), feed level in winter (high and low) child level 2: time for beginning of fattening (19-27 months) child level 3: time of slaughter (19-30 months)
Model structure: Action space Founder Proces Child level 1 Child level 2 Child level 3 Dummy Summer: Marginal grass or clover grass Winter: Continue or start fattening or slaughter Keep or slaughter High or low feeding level
Model structure Founder Proces Child level 1 Child level 2 Child level 3 Time horizon Infinite Finite Finite Finite Stage length Life span of the steer grazing / winter season stage1: until 19 months 1 month stage2-6: 1 month State space Birt month Live weight Live weight gain Live weight gain
The steer model: Founder process process tree state space: birth month, 12 levels
Child level 1 stages of child level 1: stable and grazing periods
Child level 1 stable period action space: low and high grazing period state space: 7 weight levels low and high previous winter feeding action space
Child level 2 2 grazing period clover grazing is chosen child level 2 is defined - age of 19 months is reached at 19 months (August) fattening can start stage length action space
Child level 3 action child level 2: start fattening 4 stages in child level 3 (19-22 months) 3 states (weight gains) action: keep and replace
Parameters
Model conditions
Model conditions Growth on clover grass pastures following low winter feeding steers born January
Simulation: Gain per steer
Optimal strategy in the second grazing period (child level 1) according to month of birth and LW. Permanent pasture following high feed level Clover pastures following low feed level
Optimal strategies for all seasons (child level 1) for steers born in August.
Optimal strategy in the second grazing period (child level 1) according to previous winter feed level, examples of month of birth and LW at the beginning of the period. Month of birth Previous winter feed level LW at the beginning of the period, kg Optimal pasture decision January Irrespective Irrespective Ryegrass/clover March Irrespective Irrespective 240-360 230 Ryegrass/clover Permanent May Irrespective Irrespective 220-240 250-330 Permanent Ryegrass/clover July High High 350-410 420-610 Permanent Ryegrass/clover Low Irrespective Ryegrass/clover September High High 330-400 410-590 Permanent Ryegrass/clover Low Irrespective Ryegrass/clover November High High 310-400 410-470 Permanent Ryegrass/clover Low 310-470 Ryegrass/clover
Optimal strategies at child level 2 are shown for steers born in January in the third stable period with low feeding level.
Optimal strategies at child level 3 steers born in January in the third stable period at low feeding level, a LW of 470 kg at the beginning of the third stable period and with the beginning of fattening in January at an age of 24 months.
600 500 400 300 200 100 0 Net return, DKK/steer MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Months of birth JAN FEB Net return relative to minimum net return, DKK/steer
Optimal slaughter weight, kg 600 500 400 300 200 100 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Months of birth Optimal slaughter weight, kg
Conclusions child level 1 low feeding level in winter permanent pastures the 1. grazing season clover pastures for steers with high liveweight child level 2 only few steers should be fattened child level 3
Is the hierarchic Markov proces useful to describe the given problem? organic steer production has well defined phases decisions are linked to these phases well suited for the state and action spaces of the multi-level hierarchic Markoc proces a big model (474,000 state combinations), but the hierarchic structure makes it possible
Optimal criterion Per steer Per time unit Replacement with a new steer Net return per produced steers is maximised Net return per year is maximised
The effect of optimal criterion on optimal strategy child level 1 grazing period Per steer criterion, low previous winter feed level Per steer criterion, high previous winter feed level 350 300 250 200 150 100 50 0 January February March April May June July August September October November December Month of birth Permanent Ryegrass 350 300 250 200 150 100 50 0 Live weight at start of season, kg January February March April May June July August September October November December Live weight at start of season, kg Month of birth Ryegrass Permanent Per time unit criterion, low previous winter feed level Per time unit criterion, high previous winter feed level 350 300 250 200 150 100 50 0 January February March April May June July August September October November December Month of birth Permanent Ryegrass 350 300 250 200 150 100 50 0 Ryegrass Permanent Live weight at start of season, kg January February March April May June July August September October November December Live weight at start of season, kg Month of birth
The effect of optimal criterion on optimal strategy child level 2 third stable period Feeding level Age, months Optimal strategy per time unit Optimal strategy per steer Third Stable period Low feeding level 22 23-24 < 480 kg and > 540 kg Slaughter 480-540 Start finishing < 450 kg and 550 kg Slaughter 450-549 kg Continue as usual Continue as usual 25 < 650 Continue as usual 650 kg Slaughter 26 < 750 kg Continue as usual 750 Slaughter 27 < 760 kg Continue as usual 760 Start finishing < 690 kg Continue as usual 690 Start finishing
Net return per steer, when optimised per time unit or per produced steer Simulation: steers born in different months Net return per steer/dkk Optimised per time unit 4500 Optimised per produced steer 4000 3500 3000 2500 2000 1500 1000 500 0 Jan Feb March Apr May June July Aug Sep Oct Nov Dec Months of birth
Slaughter weight and age at slaughter, when steers are produced under optimal conditions Simulation: steers born in different months Slaughter weight when steers are produced under optimal strategies, kg 700 600 500 400 300 200 100 0 30 25 20 15 10 5 0 Jan Feb March Apr May June July Aug Sep Oct Nov Dec Optimised per produced steer Optimised per time unit Age at slaughter, months (optimized per steer) Age at slaughter, months (optimised per time unit) Months of birth
Sensitivity analysis What happens to the key figures (i.e net return) if the conditions change Feed prices i.e. finishing period in winter: 1.4 DKK/SFU 0.2 (the same as winter (high feeding level) and + 20%) Beef prices i.e. class 3 (P+): 17 DKK/kg +/- 5 and 10 DKK Probabilistic Markov chain simulations were run under the calculated optimal strategy: per time unit Simulations are used to calculate technical and economic key figures characterizing the optimal policy.
The effect of changes in feed prices (summer) on optimal strategies per time unit at child level 1 for steers born in January. Ryegrass pasture - 0.3 DKK (same price as marginal pasture) Ryegrass pasture + 0.5 DKK Marginal pasture - 0.35 DKK Marginal pasture + 0.3 DKK First grazing period Ryegrass Permanent Permanent Ryegrass Second grazing period Ryegrass Both ryegrass and permanent Permanent especially after high feed level in winter and light steers (< 270 kg) Both ryegrass and permanent Permanent especially after high feed level in winter Ryegrass Third grazing period Ryegrass Ryegrass Ryegrass Ryegrass
The effect of changes in feed prices (winter) on optimal strategies per time unit at child level 1 for steers born in January Feed prices winter low - 0.5 DKK Feed prices winter low + 0.5 DKK Feed prices winter high - 0.5 DKK Feed prices winter high + 0.5 DKK Second winter period No changes compared to standard price Low feeding intensity Steers born in January and February: high feed level Only high feeding level for steers born from Jan. to May and also some steers born in June and July. Others low feeding level All steers should be fed at low feeding intensity Third winter period No changes compared to standard price More feeding at high feed level compared to standard prices (all steers born from Febr-May) High feeding intensity is optimal for many steers (all steers born from Febr. to May) and half of the steers born the other months Low feeding intensity
Effect of price variations on net return Net return per steer, DKK 6000 5000 4000 3000 2000 1000 0 Standard prices minus plus minus plus plus minus plus minus plus minus plus minus minus plus 300 250 200 150 100 50 0 Net return per time unit, DKK Meat Prices Premiums winter, high feed winter, low feed marginal grazing clover grazing fattening Feed prices optimised per steer optimised per steer optimised per time unit optimised per time unit
The effect of price variations on live weight at slaughter Live weight at slaughter, kg 700 600 500 400 300 200 100 0 Standard prices minus plus minus plus plus minus plus minus plus minus optimised per steer optimised per time plus minus minus plus Meat Prices Premiums w inter, high feed w inter, low feed level marginal grazing clover grazing fattening Feed prices
Conclusions: criterion of optimality In general the optimal strategy only changes slightly depending on the criterion (net returns per steer versus per time unit). An optimization per time unit in some cases favours a more intensive production based on high feeding level in winter and finishing of steers as well as earlier slaughtering compared to an optimization per steer.
Conclusions: Simulations of key figures Finishing of steers seemed not to be an optimal strategy from an economic point of view and price changes in feed, beef and premiums did not favour finishing of steers. Most important factors with effect on net return: Beef prices prices for ryegrass/white clover pasture Prices for low feeding level
Article in farmer newspaper Organic Farming
Article in farmer newspaper Organic Farming
Perspectives optimal strategies for an overall organic steer production data from specific farms can be included and optimal strategies can be simulated on farm and animal level data on single animal level might be introduced in steer production effects of price changes can be determined quite easy with simulations not time consuming the effect of fattening of dairy bred steers should be revised