Put Genetic Diversity At The Core To Avoid Economic Loss

Genetic diversity is something a successful dairy cattle breeder really should consider when planning the next generation of dairy cows. It is no secret that inbreeding - the mating of related animals - is an invisible, costly and growing hazard for dairy farmers all around the world.

In a well-coordinated and planned breeding programme, a large number of sires of sons with different pedigrees used in the breeding programme play an essential role in avoiding inbreeding. So, asking which is your top bull? is by no means a silly question. At VikingGenetics we have set a clear goal of the number of sire of sons with different pedigrees to use every year to guarantee genetic diversity and, at the same time, enable genetic gains and a sustainable breeding programme.

In countries with a high production of milk and a vigorous dairy industry such as the United States, the very best bull would be the hero of the market. The study “Effects of Inbreeding on Production and Survival in Jerseys” by J. R. Thompson, estimates that the level of inbreeding in the United States dairy population is increasing and many factors have contributed to this rise. “The main factor is that the AI (Artificial Insemination) industry has significantly reduced the effective number of males in the population, and relationships between males have increased over time.” According to this research, by focusing on the very best top bulls, the different AI companies have compromised genetic diversity and increased the level of inbreeding.

Peter Larson, Breeding Manager for VikingJersey, explains that a high merit bull can be sold by many different AI companies where there is “tough” competition and all of them tend to use the same genetics by using the same bulls or the same high merit dams. “There are several American based companies running a Jersey programme and all of them use the top bulls as sires of sons, to breed the next generation of bulls and cows,” he says. “The use of sires of sons is not coordinated and the risk of inbreeding is increasing. Money and test capacity could be spent more wisely by focusing on breeding outcross lines, instead of main stream bulls,” Larson adds.

To ensure a healthy breeding programme, the only solution would be for AI companies in the US to agree on a voluntary basis to compromise on the use of bulls. The Nordic countries, Denmark, Sweden and Finland, have a National breeding programme for Holstein, Jersey and RDC (Red Dairy Cattle), managed by VikingGenetics. In the case of VikingJersey, approximately 40 bulls are selected to be part of the yearly breeding programme; and no more than three sons will come from the same sire.

“At VikingGenetics we use new bulls from 20 different sires of sons or family lines every year,” Larson says. What is more, sires only stay on the active marketing list until such time the managers of the breeding programme decides the sire has contributed enough to the gene pool in the population (normally for only 6-9 months).

Keeping a close eye on the number of sires of sons is not the only strict control VikingGenetics uses to design the breeding programme. Saija Tenhunen, breeding specialist at VikingGenetics explains that there is a high-quality support programme that focuses on population management to avoid inbreeding.

“We also offer our own breeding tool VikMate, which enables us to control inbreeding and genetic gain at herd level. If mating plans are created in VikMate, we can limit the increase of inbreeding in a herd and find the most suitable sires based on the traits of interest. As such, we focus on controlling the problems caused by inbreeding at both population level and herd level,” she says.

With closer relationships between animals in a population, the risk of genetic defects increases.

“When undesirable recessive genes appear in the homozygous state, the condition is often fatal. Such fatality may occur very early in embryonic development and look like a failed conception to a dairy producer. If the genes are semi-lethal, and the individual does survive, it may be totally unprofitable,” Bennet G. Cassell, Extension Dairy Scientist, of the Virginia Tech states in studies about Inbreeding.

Accordingly, genetic diversity is an important consideration when dairymen select genetics to improve their cattle, especially when the level of inbreeding is rather high. Complete pedigree information dating four or five generations back is needed to manage inbreeding well, Cassell argues.

Choose outcross bulls

Where to find outcross bulls with a good ranking has become an open question for more and more dairymen, especially among Jersey breeders in the US.

In each breeding population, the most successful pedigrees will become influential. Offering outcross bulls of high merit to the global markets comes with the added bonus that they are easier for any dairyman to select and use. This is an advantage that VikingJersey’s breeding manager emphasises when talking about the Nordic offer. “We have a better chance of finding an outcross bull among all the family lines we have in our VikingJersey breeding programme,” Larson says. “All females are registered and 95% are pure Jersey while all bulls are minimum 99.5% pure. VikingJersey bulls are measured for any increase in inbreeding per generation and we are under 1% per generation - the limit recommended by the Food and Agriculture Organization of the United Nations (FAO).

“Inbreeding levels would most likely drop quite a lot when using Danish bulls in the US,” Tenhunen adds.

“We can lower inbreeding at herd levels when combining DK and US lines together. When we minimise inbreeding in a herd there is less loss of production and greater survivability,” she says.