Commercial beef production has relied on crossbreeding for more than 50 years to improve survivial, fertility, growth and disease resistance.
The effects of heterosis are the opposite of the effect of inbreeding depression. At each location of the pairs of chromosomes the two genes are much less likely to be identical with crossbreeding than with same-breed matings. Therefore, genetic recessives of both major and minor consequence are not expresses. Reasearch indicates that heterosis is greatest for traits related to vitality, fertility, health and survival.
Heterosis is not everything - the additive breed effect are important in crossbreeding as well as in all breeding. The heterosis will be an extra benefit on top of the parent average. So one critical point is to always use the best bulls from breeds that suits your conditions. A crossbreeding program needs to be well planned and organized to produce benefits. The breeds you pick must be unrelated, competitive and have a efficient breed improvement program - and remember to use the best buss for the best results.
Why Three Breeds?
Capturing and sustaining heterosis is a key part to a efficient cross breeding program. Once you have gotten used to the extra bonus of heterosis you do not want it to drop below 75%. For 2-breed crisscrossing the extent of heterosis drops to 50% in the second generation - levelling off at 67%. A system of 4 breeds results in a high heterosis on average - 93% but it is very hard to find 4 competitive, unrealted breeds for most production systems. A 3-breed rotation is the optimum and results in average heterosis of 86%.
To make your crossbreeding system as easy as possible colour tagging is a good option. You simply use 3 different colour ear tages on the calves. Calves sired by Holstein get, for example, a blue tage. Calves sired by a Danish Red get a red tag tag and the calves sired by your third breed (for example Jersey or Montbeliarde) get a yellow tag. When you see a blue tag you know that the animal will be inseminated with Danish Red semen, etc. When you have your 3-breed crossbred you just begin the circle once again by imseminating with Holstein.