Inbreeding

Holsteins are under strong selection pressure, which result in impressive genetic progress. At the same time the genetic diversity is decreasing. An increase in the inbreeding rate per year is observed, it’s increase in recent years is associated with the introduction of genomic selection. This phenomenon has negative consequences because it leads to an increased occurrence of mating (highly) related individuals. The more closely related individuals are, the more likely are to pass genes to their offspring from their common ancestor. The level of inbreeding manifested as inbreeding depression reduces the health, productivity and vitality of animals.

Inbreeding is defined as mating of the related individuals. Inbred is a measure of the individual’s homozygosity level so inherited genes by the individual from its father and mother from the common ancestor of both parents.

The other parameter is expected future inbreeding which is defined as the expected inbreeding level of future offspring, as a consequence of meetings the reproductively active bulls with available cows and heifers.

Centre for Genetics estimates:

  • the level of inbreeding for females and bulls,
  • completeness of pedigrees and
  • expected future inbreeding of offspring for each bull classified as active,
  • increase in inbreeding of Polish Holstein-Friesian population.
  • Analyses are performed weekly to include as soon as possible newly registered individuals.

    The average inbreeding level of the Polish Holstein-Friesian cows in 2019 was 4.8% and it was 0.85% higher than the expected future inbreeding of offspring prognosed in 2019 (Figure 1). Which means that breeding decisions related to the selection of animals for mating cause an increase inbreeding greater than at random selection. The expected future inbreeding describes the relationship of bulls with the population of reproductively active cows and heifers.

    The level of inbreeding in Polish Holstein-Friesian cows

    The level of inbreeding in Polish Holstein-Friesian cows

    An important indicator is not only the inbreeding level, but its increase. Figure 2 shows the average increase in inbreeding in a given birth year of cows. The increase in inbreeding in 2019 compared to 2018 was + 0.3% higher. In the last 10 years a steady increase in inbreeding can be observed.

    Increase in inbreeding rate in Polish Holstein-Friesian cows

    Increase in inbreeding rate in Polish Holstein-Friesian cows