One of the main aim of Intermizoo and the Italian selection is to improve health and fitness of the Holstein population, also through the use of genetics tools. The latest scientific findings allow to explain why in the past well defined mating plans led to high risk of abortion: researches found out that some specific HAPLOTYPES in the bovine species affect fertility. These are particular combinations of alleles that are inherit together, called Holstein Haplotypes (HH), and cause 25% chance of abortion during the first three months of pregnancy.
Through carefully-studied mating plans, the aim of the Italian selection is to avoid the spread of these genetic disorders in the Holstein population.
WHAT ARE HALPOTYPES?
In genetic, a haplotype is a particular combination of alleles that are inherited together from a single parent. For long time, haplotypes have been investigated because their diversity is a measure of the uniqueness genetic inheritance of a given population, such as the coat colour and polledness. However, haplotypes can also transmit different genetic disorders.
In the bovine species, particularly referring to the Holstein population, haplotypes can cause abortion during the first three months of pregnancy. Fortunately, abortion occurs only if embryos have two copies of unfavorable haplotype (homozygosis) inherited from both heterozygous parents. If the mating of two carrier parents occurs, there is 25 % probability of homozygous embryo, condition which is incompatible with life.
In the Holstein breed, Haplotypes were first discovered in 2011 by the well-know genetist, called VanRaden. Researchers starting to doubt when well-defining bloodlines started recording lower fertility. Some years later, thanks to the modern discoveries in genetics and bioinformatics, researchers detected the presence of specific sequences in the bovine DNA that are lethal for the embyo.
HOW MANY HAPLOTYPES AFFECT FERTILITY?
In the past 10 years, 7 different haplotypes has been discovered and certainly future researches will uncover more haplotypes. Each of them, cause abortion in the 25% of the progeny, if heterozygous parents are matched.
It is good to point out that the presence of a specific haplotype does not interact with haplotypes of different classes: for instance, matching HH1 sire and HH2 dam, do not cause probability of lethal condition for the embryo.
WHICH ARE THE CONSEQUENCES FOR THE DAIRY FARM?
A loss of fertility due to haplotypes has direct consequences in the management costs of the herd, due to the increase of calving interval (CI) and the decrease of the conception rate (CR).
HOW TO MANAGE HAPLOTYPES THROUGH SELECTION PLANS?
Starting from 2014, different genomic tests are commercially available, both for bulls and cows. The provided information are used for optimize the mating plans and avoid the diffusion of fertility disease in the Holstein population.
In few foreign countries, these information are already published. Starting from December 2020 this will also happen for Italy.
However, for some years now, Intermizoo avoids the selection of Haplotype carrier bulls for its own bull programme, and develops specific mating plans where needed. This strategy avoids the diffusion of genetic diseases in the Holstein population.
Moreover, starting from the genetic evaluation of December 2020, Intermizoo publishes the haplotype information on each bull sheet. It is important to highlight that carrier bulls shoul be use with mating plans, not completely eliminate from selection.
Intermizoo HH free bulls (HHF) are identified both on the Intermizoo website and in the Intermizoo sire catalogue by the new icon, and HHs are listed right down the name of each bull.
