Model structure: Preliminary plan

 MODELLING A CALF LIFE

Model spreadsheet in a file will consist of’:


1)Model overview; The model overview will show the prediction for a calf. 

   It is consists of;


   a) Stage of the calf

       Description:

  • There will be 33 stages based on 3 weeks interval in each stage. 
  • The stage started from time the calf is born until it become a heifer that have
    its first calving. Every calf stage will have different event in calf diseases, nutrition and management. 
  • From stage 1 to stage 5, it is define as calf.  From stage 6 to 32, it is then define as heifer.  
  • Stage to start for artificial insemination was decided at stage 21 (age 15 months), by takng into account other model rules.  Stage for first calving was decided at stage 33 (age 24 months) without taking into account perinatal mortality. 


   b) States of the calf

       Description

  • States of the calf is based on calf and heifer diseases which is important in The Netherlands dairy calf/heifer, (as well as affect growth, estrus detection and pregnancy rate of the animal?).  
  • States of the calf are healthy, Calf scours, Bovine Respiratory Disease, Parasitic gastroenteritis, Bovine lungworm, cull and death. 
  • The states are based on probability morbidity and mortality from literature.  The state is predicted from state transition matrix which is probability of being in each state at different stage.


   c) Weight of the calf

  • Weight of the calf is determine in kilograms (kg)
  • Weight is based on (normal distribution/math formula)? of The Netherlands newborn dairy calf.
  • Additional weight gain for different age/stage is based on …(normal dist?, mathematical formula?)
  • Reduced weight gain from different calf and heifer diseases is based on literature?.
  • Weight at 330kg is the weight to start insemination taking into account other model rules.


   d) Estrus detection

  • Estrus detection marks the time for Artificial insemination.
  • For each time estrus is detected in the heifer, it is assumed that artificial insemination is done.
  • The artificial insemination will result in pregnancy or not pregnancy by returning to estrus in 60 days.  


   e) Pregnancy
rate

  • Pregnancy rate used conception rate as the probability of a heifer is pregnant or not pregnant
  • Since perinatal mortality is not taken into account in this model, a pregnant heifer is assumed to have successful pregnancy until calving.
  • The heifer which do not pregnant after artificial insemination will return to estrus after 60 days


2) Morbidity and mortality transition matrix  

  • Mortality and morbidity rate are based on calf age.
  • Mortality rate is define as number of calf died in particular stage/ calf at risk?
  • Morbidity is define as number of calf sick at particular/ calf at risk?
  • Transition matrix consists of 7 states which are healthy, calf scours, Bovine Respiratory Disease, Parasitic gastroenteritis, Bovine lungworm, cull and death.
  • Healthy states is the states defined as not being sick or 1-morbidity rate.
  • Calf scours states is the states for infectious gastroenteritis caused by bacteria, virus and parasite.  Other clinical signs under this state include septicaemia, enteritis and diarrhoea.  
  • Bovine respiratory disease is the state defined by respiratory syndrome caused by bacteria, virus and mycoplasma. 
  • Parasitic gastroenteritis is a state defined by disease caused from the nematode genera Trichostrongylus, Ostertagia (including Teladorsagia, Cooperia and Nematodirus).
  • Bovine lungworm is a state defined by disease caused from the nematode Dictyocaulus viviparus.
  • Cull state is defined by the action taken by the farmer to get rid of the calf/heifer outside of the farm.  It can be meant as slaughter or sell.
  • Death state is defined as a condition of a calf of being not alive in the farm.

3)Reproductive probability
There are 2 important parameters, estrus detection and pregnancy rate.

estrus detection rate

  • Estrus detection rate is taken from cow estrus detection rate
  • It is assumed that each time estrus is detected, artificial insemination is done
  • The age of doing artificial insemination is 15 months
  • (Estrus detection rate will be different if it was detected earlier than 15 months, detected second, third and etc time after first artificial insemination and for being in other than healthy state)

Pregnancy rate

  • Pregnancy rate is based on conception rate
  • Pregnancy only occur or not occur after artificial insemination.
  • (Pregnancy rate will be different if happen in second, third etc time and for being in other than healthy state)

4)Weight

  • weight is presented in kilograms (kg)
  • normal weight have normal distribution
  • weight is affected by disease state
  • diseased weight is based on literature?
  • weight for optimum reproduction is at 330kg?
  • weight gain during pregnancy different?
  • Precalving optimal weight is 500kg to 660kg?

5)Model rules
Basic Important Rules;

If calf with stage 15,status 1 have 330kg weight, there will be risk discrete
estrus and risk discrete pregnancy.
If calf have stage other than 15, no estrus detection=no AI, and no pregnancy.
If calf have stage 15, status 1 and weight <330kg, no AI(estrus) and no
pregnancy
If calf have stage 15, status other than 1, weight 330kg, reduced estrus
detection (Risk discrete) and reduce pregnancy rate (risk discrete).
If calf is pregnant, it is assume to be pregnant until calving.


NOTES;

  


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