The stuff you bought could have been produced on a farm where they just have large numbers of calves. Lots of dairy farmers don't keep the calves their cows produce, but sell them on to those who specialise in growing youngstock. The calves are often sold at auction and dairy farmers will buy heifers ("youngstock") to add to their herd - once the time-consuming stage of looking after them has passed and the animals themselves are nearing sexual maturity and can live outdoors. Cross-bred calves (usually the offspring of a dairy cow and a beef-breed bull) are sold on to the people who produce beef animals, and the bull calves will have been castrated. The pure-bred dairy heifer calves are sold (to dairy farmers) when they reach what's called "bulling" age and the farmer will then most probably use a beef-breed bull for the heifer's first pregnancy. This is because artificial insemination isn't either successful or advisable for what's called "a maiden heifer" - the heifers will "run with the bull" in the fields, nature takes its course, and the resulting calf will be sold for beef production. Subsequent breeding is usually via A.I., when the farmer will chose semen from a bull whose bloodline is that of a proven successful dairy line in terms of milk quality/quantity. Farmers keep records of their cows' lactations and will only keep a pure-bred dairy breed bull calf if it's a really "special" one which they might go on to use to further their own particular "bloodline".
Farming has become so specialised these days - for reasons of economy and efficiency - that it doesn't pay to rear all your own home-bred calves, unless of course you are breeding a particular "line" and want to retain the offspring (heifer calves) for eventual inclusion in the dairy herd itself. Calves will be housed indoors and thus create a fair amount of waste - usually straw-based. People who keep horses nowadays seem to use wood shavings for bedding rather than straw.