PhD Plans




Youngstock rearing is important for future heifer replacement.  The main objective of a dairy farm is to have lower first calving age thus, lower cost of rearing a youngstock.  In order to do the estimation of youngstock rearing cost, diseases effect must be taken into account.  Furthermore, there is a relationship between growth with puberty time and milk production.  Based from literatures, the rearing cost was also dependent on the calf birth month.  Consequently, all of the important aspect that can affect milk production must be considered during the rearing period to have an optimized cost.


Although youngstock rearing is important, farmer underestimates the cost of rearing a youngstock.  Furthermore, the interdependent relationship and variation between diseases, growth and reproduction makes it difficult for the farmer to evaluate the dairy calf enterprise viability, to manage the replacement enterprise optimally and finally to meet the sufficient amount of heifer replacement for the dairy enterprise.  Moreover, veterinarians find it difficult to advice a cost effective treatment and better healthcare protocol based from the economic point of view. 


Thus modeling is useful to get an insight in youngstock rearing.  Economic optimization of youngstock rearing is an important tool for the farmer to assess the viability of the calf enterprise and finally to decide whether to keep or to cull a calf. 


Research background


There has been no attempt to estimate youngstock rearing costs from birth that includes variation especially modeling the disease incidence.  However, there have been a few models that estimate the heifer rearing costs. 



Economic research in this area


In this study, the farm was divided into three enterprises; Calf, heifer replacement and dairy.  Heifer replacement enterprise links the calf enterprise with dairy enterprise.  Calf enterprise focused on diseases prevention, while heifer replacement focused on successful pregnancy at optimal age and dairy enterprise was focusing on maximum milk production.  This research is not going to include genetic improvement in a calf. 

In order to include all the main objectives, there must be an interdependent relationship between the enterprises which is the birth month and the growth function.  The model is in chapter 1.  


Finally calf enterprise objective were focused in chapter 2, and being extended to replacement enterprise in chapter 3 that focused on farm management, growth and reproduction.  The model should be validated and was focused in chapter 4.  Finally in chapter 5, based from all of the previous findings, the model should support the decision of a farmer to keep or to cull a newborn and/ or a sick calf.





  1. To calculate the cost of rearing a youngstock that include variation
  2. To help veterinarians recommending the most cost effective healthcare protocol.
  3. To determine the cost of abortion in replacement heifer.
  4. The research will also focus on validating the model
  5. To do optimization in calf rearing cost that took into account variations and enable the farmer to make decision either to keep or to cull a calf


Chapter 1


Estimating youngstock rearing costs in The Netherlands using Monte Carlo simulation


Literature review



  1. To calculate the cost of rearing a youngstock that include variations



  1. Monte Carlo simulation


Materials and method

  1. Inputs about disease, growth and reproduction.  Thus inputs for heifer rearing in The Netherlands were based from Monique papers while diseases inputs were based from Europe literatures and expert opinions.  Model the disease, growth, feed, reproduction and possibly milk production.
  1. Model the economic from healthcare cost, feed cost and reproductive cost.
  2. Morbidity cost and mortality cost must be differentiated in different objectives as mortality loss requires more complex assumption.


Expected result

  1. The costs
  2. The total cost at each month a calf was born
  3. The important variable that influence the total cost
  4. Important calf diseases from the economic point of view


Advantage of the model

Able to resolve uncertainty


Additional comments about the model

Compensatory weight mechanism needed

Weight loss of the diseases

No genetic influence was taken into account

There’s grey area of the diseases which need a lot of assumption






Chapter 2



Herd health program in youngstock rearing by optimizing diseases costs


Literature review

By knowing how much is the losses from the diseases, the study is now focusing on disease prevention to avoid the occurrence of disease loss (McInerny, J, 1996).   The aim is to find the best prevention management strategy.


There are a few studies mentioning about the cost effectiveness of treatment and control of parasitic and calf diseases (Berge et al., 2009; Guichon et al., 2000; Barret D.C., 2000).  However, there are no specific recommendation and guidelines from the economic point of view.  Furthermore, as calf diseases can be control and treated, the most common concern is related to the over use of antiparasitic drugs and antibiotic resistance.  By recommending the best strategy to prevent calf diseases, it can reduce unnecessary cost of disease treatment and control the use of the drugs.



  1. To recommend the most cost effective youngstock healthcare protocol



  1. Cost effectiveness analysis



  1. Inputs about types of drugs used in calf disease prevention
  2. Inputs about management for calf disease prevention
  3. Effects towards the calf when prevention measures were taken eg weight gain
  4. Provide strategy measures, and evaluate the cost and effectiveness of the drug and management measures or the combinations


Expected result

The most cost effective herd health program


Advantage of the model

Usage of different drugs

Optimize costs by preventive measures


Chapter 3



The heifer replacement strategies


Literature review

Farms in The Netherlands are consists of intensive, average and extensive farm.  This needs to be addressed in calculationg the costs of calf rearing because each farm need different approach in managing the youngstock rearing.  Furthermore, the reproduction success is important for replacement heifer. 




  1. To determine the cost of perinatal abortion, dystocia
  2. To evaluate the benefit of different reproduction strategies



  1. Inputs for abortion and dystocia in different farm management
  2. Cost benefit analysis in different farm management
  3. Monte Carlo





Expected result

The break even line for cost and benefit for each farm management


Advantage of the model


Chapter 4



Validation of the model


Literature review



To validate the calf rearing model



By taking sample from The Netherlands. 


Chapter 5

Literature review


Economic optimization of youngstock rearing

Keep or cull, to know is it worth keeping a newborn calf or a sick animal or just cull the animal.  It is a viability of the youngstock enterprise.



To keep or to cull a sick calf



  1. Dynamic programming




Expected result

1.  Keep or cull the calf, sick calf


Advantage of the model


Research plan


PhD Schedule







Literature review





Model building/ Input finding





Summer holiday





Model validation










Winter Holiday













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3                   4








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