Ruminant advanced conception

CLEM.Resources.RuminantAdvancedConception

Enhances the standard conception calculations used.

The probability of a breeding female conceiving when mated is a critical aspect of modelling herd dynamics and the CLEM model offers a range of methods to calculate conception (see Ruminant conception).

This component is added below a Ruminant type component in the Resources section to provide the calculation of conception rates for the Ruminant type. Rather than a single calculation of annual conception rate as defined by Ruminant conception curve parameters, this component allows the model to calculate conception rates based on the age of the mother if this is first mating (<12 months old, 12-24 months old, or >= 24 months old) and whether this is the 2nd or 3rd+ offspring mating.

Only females found suitable for mating (see Ruminant conception) are considered in this calculation. Therefore some breeders (pregnant, underweight or too old for controlled mating) are not included in this conception rate and it will be different to the final herd conception and following birth rates.

The following parameters are associated with this component.

Four values are required for each parameter and provided as a comma separated list of values (e.g. 1,2,3,4).

The values are provided in the following order

  • Less than 12 month old female and first mating
  • At least 24 month old female and first mating
  • 2nd offspring mating
  • greater than 2nd offspring mating.

The coefficient for the calculation of conception rate

The intercept for the calculation of conception rate

The asymptote for the calculation of conception rate

This provides the maximum conception rate possible when uncontrolled breeding is used.

The following equation is used to calculate the conception rate in any month for a female breeder given her current weight and the parameters above based on the mating group she is identified in (i) from the age and number of previous offspring/matings.

Conception rate = ConceptionRateAsymptotei / (1 + eConceptionRateCoefficienti * Weight / StandardReferenceWeight + ConceptionRateIntercepti)

This is designed as an annual conception rate applied to a single mating event. In order to account for multiple matings the conception rate estimated needs to be reduced to represent the expected conception amongst the herd after all mating has been performed for the year. As it is difficult to determine the number of months mating from within the simulation, this correction needs to be undertaken by the user.

See also