What’s new?
During the April 2023 data release, ANAFIBJ has updated the Calving Ease Index. The calculation model used so far (Sire Model*) has been replaced with the Animal Model**. In addition, the data used for the calculation are now much more precise, thanks to the update of the editing process.
In the last years, the genetic programs paid particular attention to the selection of A.I. bulls: this allowed to obtain a population that shows fewer and fewer problems at birth. As a matter of fact, from the first graph it can be seen that the phenotypic trend of difficult births has decreased. As already happened in other countries, the Calving Ease Index will be more compressed due to the smaller differences within the population, as shown in the second graph.
Bulls with a genetic value of 100-102 now have good easy calves. Higher the index, easier the calvings.
*The genetic effect is calculated based on the characteristics of the father: only the transmission of alleles in the male line is analyzed.
** The genetic effect is calculated based on the characteristics of the animal itself: relationships in the female line are also analyzed.
What is the calving ease?
Reducing the incidence of problems during calving is a crucial aspect for dairy cow breeders: less problems at calving means live and vital calves, and cows in the best condition to face a new lactation.
One of the genetic tools that allows to improve this aspect is the improvment of calving ease trait. It is important to underline that Calving Ease Index does not select for smaller calves at birth (which is linked to extreme delicacy of animals in early life) but to reduce the incidence of difficult births.
The genetic effect
The characters related to calving ease undergo two types of genetic effect:
- The direct effect, which is the genetic component of the animal that is born;
- The maternal effect, which is the genetic component of the cow that gives birth.
Therefore, each cow expresses its direct effect once (when it is born) and its maternal effect several times (each time it gives birth).
For this reason, there are two resulting breeding values:
- Sire Calving Ease: the direct effect of the bull (sire of the calf);
- Daughter Calving Ease: the maternal effect or the calving ease of the daughters of the bulls which gave birth.
| Direct Effect | Maternal Effect |
|---|---|
| Sire Calving Ease | Daughter Calving Ease |
Expression of the index
| Genetic Value | Calving Ease |
|---|---|
| <100 | Difficult |
| 100 | Average |
| >100 | Good |
The heritability of this index is around 10%, and it is strongly influenced by environmental factors. The index, like all other management data, is expressed with an average of 100 and a standard deviation of 5. Bulls with values higher than 100 are bulls with more ease to calving (sire calving ease) or as fathers of cows with easy calves (daughter calving ease).
