While the number of available bulls has varied over the last ten years, the inbreeding curve for the Prim’Holstein breed continues to evolve. The breeding organization will soon include elements of kinship in the calculation of the ISU.
That inbreeding ? “I check very rarely,” admits Alexandre Gallard, a breeder from Saint-Sigismond (Maine-et-Loire) and used to competitions. “I do not mind sometimes going up to 9% inbreeding when I make my mating choices. “On the website of Prim’Holstein France, the interactive mating plan incorporates an algorithm that calculates the inbreeding rate of the unborn product by going over ten backwards generations average. The breeder enters the mating targets for his breeding and indicates degree of inbreeding maximum he wants, ie percentage of identical genes in the genome, and the algorithm suggests couplings optimally within the set inbreeding limits.
Inbreeding reduces the production potential.
Alexandre Gallard can not go beyond a rate of 7%. For comparison, the degree of relationship between two first cousins is 6.25%. But you still need the tool. “We have so many choice of bulls that the risk is limited, you just do not have to accumulate, ”he says to himself. The chairman of the Maine-et-Loire Prim’Holstein breeders’ union, Florian Vigneron, goes even further: “I know I’m a little against the grain, but I think inbreeding helps the breed move forward. Put the two best tireif they are very strong in a position even though there are risks, this makes it possible to fixation of the genes », Supports the breeder of Saint-André-de-la-Marche (Sèvremoine). In Denmark, the herd has an average of 8% inbreeding.
And yet inbreeding lowers the milk production potential, affects cell levels by several thousand and is also a source of fertility problems.
Closely related bulls
4,666 bulls have just been marketed over the last five years, of which just over 900 are in the current catalog. The days of the star bulls seem to be over, they are over Jocko Besne and their 1.7 million sequins collected. Today’s bulls dose less and have shorter careers. “Globally, however, inbreeding is not declining,” warns Coralie Danchin-Burge, project manager genetic variability at the breeding institute. For this to work, enough bulls must be kept to preserve the next generation.
Every Prim’Holstein cow has 5.8% Shottle or O-Man.
“There are too few of them compared to the world population of Prim’Holstein cows. And above all, they are extremely related. Taurus born in the late 1990s, Shottle and Omantwo “greater ancestors”, for example, have both Elevation and Chief in their genealogy. Result: they have a marginal contribution of 5.8%. This means that any Prim’Holstein cow has 5.8% Shottle or O-Man. “There are only a few ancestors left who are adults, theirs genetic abnormalities will express themselves as they are repeated many times, ”explains Coralie Danchin-Burge.
Moderate genetic progress, degradation of diversity
Since the advent of genomics in 2009, the number of candidates for selection increased and the differences between the generations became smaller. All of this has helped to improve genetic progressbut at the expense of a degradation of genetic diversity, which is characterized by an increase in inbreeding.
That genomic selection allowed a significant increase in annual genetic progress of 71% in Normande. In Prim’Holstein it is only 33 per cent. But above all, Holstein is the only one of the three most important dairy breeds to have seen it loss of genetic diversity speed up. This is what Anna-Charlotte Doublet notes in her doctoral dissertation, which defended in 2020 aboutDevelopment of inbreeding in Prim’Holstein, Normandy and Montbeliarde. The annual inbreeding rate, which measures the increase in inbreeding, is 4.3% over four years in Holstein against 1.7% in Normandy. “There are signals that are starting to flash,” warns Coralie Danchin-Burge. We fear a large effect at sector level. “The inbreeding curve is progressing faster from 2015-2016,” notes the geneticist in vain.
This development does not seem to frighten Pierre-Alexandre Lévèque, research and development project manager at Prim’Holstein France: “Inbreeding increases a little from year to year, that is the very principle of a the racer selection. To reduce it, it is necessary to make crosses. “And then the advantage of Prim’Holstein compared to certain breeds,” is that there are selection schemes in America, Holland, France or New Zealand, and the programs are different, the engineer reassures. But “the race is run by the Americans, where the star system is not dead, with selections that are only worth it in the short term,” nuances Coralie Danchin-Burge.
Inbreeding integrated into the calculation of ISU
OS has another clue to help breeders raise the level of genetic variability: the integration of inbreeding elements in the calculation ofUIS. In other words, we will no longer only manage inbreeding at the mating level, but at the level of selection program and thus the entire population. “We can really have a selection of the most ‘original’ individuals and have control and mastery of inbreeding “, Argues Pierre-Alexandre Lévèque.
“By implementing this principle, we assess that an individual is no longer genetically interesting, not only because it is effective, but also because it is original in relation to the population. We have been working on this for several years, but not all populations are genotyped. We must therefore find the best management system to integrate it into the ISU ”.