Three of the calves are male. What are the odd of that?
Pretty danged good odds, if you are using gender selected semen. Gender sorted semen will produce 85% to 95% of the gender asked for.
Lots of tech available for breeding cows these days. Frozen embryo implantation is another. You take one super good cow and give her fertility drugs so she produces a half dozen eggs or more, which you breed with semen selected from a super high quality bull.
The embryos are flushed from the uterus with what is basically a garden hose and caught. Then you freeze the embryos and ship them anywhere in the country, or you use them to impregnate lesser quality cows in your own herd.
Of course Gilbert's old Gramps and Pops might still just turn a bull out with the cows and take their chances.