Ruminant conception curve

CLEM.Resources.RuminantConceptionCurve

Calculation of ruminant conception based on equation of curve.

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. This component will use a single calculation of annual conception rate as defined by parameters supplied. Ruminant advanced conception provides an advanced calculation taking into account the age at first mating and number of offspring.

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.

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

Conception rate = ConceptionRateAsymptote / (1 + eConceptionRateCoefficient * Weight / StandardReferenceWeight + ConceptionRateIntercept)

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.

The calculated conception rate will be multiplied by the probability of conception during lactation (see Ruminant parameters breeding) to provide the final conception rate.

See also