Massey135":sbjnlall said:
Then why is the f1 preferred over the mongrel?
Because a F1 cross is more consistent than a A+B+C cross; a A+B+C+D cross is yet a little less consistant, and more consistent than a mongrel.
Less consistent; not less heterosis.
An animal with a purebred sire and a purebred grandsire e.t.c will still show a great deal of consistency. 50% of its genes are from the first breed (A), 25% from the second breed (B), 12,5% from (C), and so on. It does not mean that much even to consistency, if there are three or four breeds in the mix, as long as no crossbred bulls are used.
Putting a crossbred bull on a crossbred cow makes a mongrel. All bets are off.
Colour wise, for example; a pure hereford bull gives some white to the face of all calves, while a hereford cross only gives it to some of his offspring.
If one wants to use a crossbred bull, and need consistency, the cows must be purebred. In this scenario there is no advantage in a threeway cross compared to a twoway cross, because there is no maternal heterosis with purebred cows.