Weaning rate

Weaning rate calculations in Dynama+

The Dynama+ program can be set for one of two options as to how the number calves to be weaned is calculated.

The first option calculates new calves by multiplying the nominated weaning rate for a group of females by opening breeders plus purchases minus sales minus spays. In this option, the weaning rate is specified as calves weaned from cows mated and kept. This method is consistent with that used in the Breedcow+ program, and thus must be used if the Dynama+ program is to use data transferred from the Breedcow+ program.

The second option calculates new calves from the breeders on hand at the start of the budget year and assumes that all purchases, sales or spaying are done after calving. This option may be preferred if budgeting is done on a financial year rather than a production year.

These definitions, although mathematically convenient, are at odds with the “true” expression of weaning rate, which is the number of calves weaned divided by total cows mated. To satisfy the requirement for a “true” expression of weaning rate, the ratio of total calves weaned to total females mated is calculated and displayed as an output in the Dynama worksheet. Users need to identify the number of females sold after mating in each year for the figure to be accurate.