Ruminant conception by condition

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).

The individual based herd approach used by CLEM allows us to consider the likelihood of any breeding female conceiving on any mating occasion. We assume that the likelihood of conceiving is related to the condition of the female (see Ruminant conception by condition). CLEM currently uses a simple for of this approach where we use the individual's current weight divided by the nominal weight (see Grow ruminants) as an index of condition. A minimum condition cut-off is provided below which conception does not occur. This method means that mating can occur all year round (natural mating, given males and females are located together) and mating will only be successful when the females reach a set body condition. This approach provides the functionality to limit breeding as body condition declines seasonally based on forage quality and quantity and females recover after birth and the energy demands of lactation. Further functionality provided in the model can limit the number of females that can be serviced in a month (see Breed ruminants). Future version of this approach can improve the condition calculation or probability of conceiving based upon condition.

The following parameters are associated with this component.

Condition index below which no conception

The index of condition (current weight divided by normalised weight) below which conception does NOT occur.

Maximum probability of conceiving

This sets an upper limit on the probability of conceiving given the condition test has been met. You can use this to determine a conception failure rate such as the failure rate for artificial insemination.

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