Optimal management of relplacement heifers in a beef herd: A model - - PowerPoint PPT Presentation
Optimal management of relplacement heifers in a beef herd: A model for simultaneous optimization of rearing and breeding decisions A.H. Stygar, A.R. Kristensen, J. Makulska Katarina Nielsen Dominiak Ph.D. student Department of Large Animal
A.H. Stygar, A.R. Kristensen, J. Makulska
Katarina Nielsen Dominiak Ph.D. student Department of Large Animal Sciences
Optimal management of relplacement heifers in a beef herd: A model for simultaneous optimization of rearing and breeding decisions
05/10/2016 AQMHM 2016 Markov 2
Decisions Strategy
Long term planning
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Founder level 0 Child level 1 Child level 2
Successful conception Birth Total heifer rearing period Preweaning period – 10 stages 30,5 30,5 30,5 30,5 30,5 30,5 30,5 30,5 30,5 Birth 9 mo Weaning Puberty 1-10 mo Reproductive period – 32 cycles 21 21 21 21 21 21 Days Days
Multi Level Hierarchic Markov Process - MLHMP
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Founder level 0
Successful conception Birth Total heifer rearing period
Multi Level Hierarchic Markov Process - MLHMP One state variable: Birth month Indoor season: November – April Outdoor season: May – October Decision: Feeding level until puberty defined by Average Daily Gain (ADG) Information: Month of age-depending stages in child levels, feeding costs, breeding costs
05/10/2016 AQMHM 2016 Markov 5
Child level 1
Preweaning period 10 stages 30,5 30,5 30,5 30,5 30,5 30,5 30,5 30,5 30,5 Birth 9 mo Days
Multi Level Hierarchic Markov Process - MLHMP 10 stages: Months suckling at cow (1-9) Stage length: 30,5 days State variable: Body weight (BW) in classes of 10 kg Decisions for each stage: Wean or continue suckling period Strategies: If weaned; ADG in reproductive period is chosen 400 g, 600 g, or 800 g
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Weaning Puberty 1-10 mo Reproductive period – 32 cycles 21 21 21 21 21 21 Days
Child level 2 Multi Level Hierarchic Markov Process - MLHMP 33 Stages: 1 ‘weaned’ + 32 reproduction stages Reproduction stages Length: 21 days each State variables: BW class and reproductive status Decisions:
Weaned stage Length: 1-10 months State variable: BW class Decision: ‘Continue feeding’
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Feed costs 70-80 %
Calf reared
(ADG 800 g)
(ADG 1000 g)
(ADG 800 g)
(ADG 1000 g)
(ADG 1000 g) Heifer in reproductive period
(ADG 400 g)
(ADG 600 g)
(ADG 800 g)
(ADG 400 g)
(ADG 600 g)
(ADG 800 g)
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Non - feed costs 20-30 %
Breeding costs Buying pregnant heifer Slaughter price
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All costs are related to the birth month
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Revenue PFP: Predicted Future Productivity Data from 2.758 heifers used to estimate PFP Relationship between PFP and Age BW Season of conception Costs are influenced by season Age and BW at conception are significant predictors of PFP
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Net return – making a decision = expected reward = cost of calf by mother = feed cost = stage = preweaning state = reproductive state Optimal strategy Weaning Breeding Replacing
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Highest Lowest Average EUR 339.3 EUR 267.9 Birth month May August Weaning age 9 months 9 months Weaning month February May ADG (pre puberty) 800 g 800 g 810 g ADG (reproductive) 800 g 400 g 810 g Age (conception) 12.8 months 18 months 13.2 months BW (conception) 54.2 %
61 %
55.6 %
Results – net return Baseline
05/10/2016 AQMHM 2016 Markov 13
Historical data 1991 - 2008
Short and high growth rate Conception summer time
Longer and slower growth rate Conception winter time