Farmers are sometimes hesitant to ask questions to researchers on farmer’s days and researchers sometimes assume farmers understand certain principles, such as the interpretation and application of BLUP Estimated breeding values (EBV’s) as a selection tool. This miscommunication may lead to fewer breeders applying the breeding values for selection purposes in their own herds. If the majority of breeders within a breed share, similar breeding objectives it will also enable the breed to improve on important traits included in these objectives.
A stud farmer once asked the question that “how is it possible to have positive and negative BLUP breeding values for animals”. Breeders are more familiar with the traditional indexes and it is in theory possible for a farmer to do the calculation of indexes by himself. Farmers in general are practical people and want to understand the working of a tool first, before using it. Hence, the motivation for this brief explanation in the difference between the calculations of a traditional index versus the breeding values.
Calculation of the wean index versus the breeding value:
A well-defined breeding season which are not longer than three months will ensure a weaner calf crop where the youngest and the oldest calf does not differ more the three months in age. But,, to standardize the age to 205 days enables the comparison of growth ability between calves of the same breed, farm, season and sex. This is a contemporary group as the environment was the same for the group.
The weight gain from birth to wean is calculated and multiplied by 205 days.
- Weight gain = (Wean weight – Birth weight)
- 205 day adjusted weight = ((weight gain/age in days) x 205 days) + birth weight
- Wean Index = (205 day adjusted weight/Average 205 day of Group) x 100
For example if the adjusted weight of a weaner calf was 220 kg and the average of the group was 250 kg, the wean index calculation:
220kg/250kg x 100 % = 88%
This indicates the calf’s weaning weight was 12% lower than the average of the group.
The heritability of the trait is also included in the calculation because the breeding value is only the genetic part of the trait.
For example: (Weight – Average Group Weight) x 0.30 (heritability of trait)
220kg-250kg x 0.30 = – 9 kg
The animal in the example received a negative breeding value because the animal’s own performance was worse than the average of the group. The complete pedigree of the breed is also included in the BLUP analyses and the performance of all the animals related to this animal, in their respective contemporary groups, forms part in the calculation of the breeding value for this animal.
Photo 1: The auction catalogue is a challenging document, especially for commercial buyers and the Agricultural Research Council offer a course specifically on the interpretation of the catalogue.
Traits of economic importance should be included in breeding objectives. To make improvement possible on these traits will need a combination of good management as well as genetic selection. Improvement on traits such as fertility and growth are of utmost importance for the commercial beef producer to increase income per calf crop.
Breeding values make it possible to select breeding material based on genetic potential and for traits not always possible to see with the naked eye. Breeding values on maternal potential (milk production) of a bull’s daughters, fertility (scrotum circumference) and birth direct (to avoid calving problems) make it possible to breed replacement heifers with a more balanced approach, which include several traits of economic importance.
Frans Jordaan can be contacted at, Fransj@arc.agric.za or Tel. 012 672 9085