“Research over a number of years has indicated that, economically the optimum age at first calving is between 23 and 25 months of age.” The Dairy Site
Making decisions based on economics when you are dealing with a biological function like pregnancy is short-sighted (IMHO). I think that’s particularly true when you’re talking about breeding age in a house cow. A dairy cow that is well cared-for can produce well into her teens. In commercial dairies, most cows have only two or three lactations because they are culled around age five or six. I suspect beef cows can also live and produce that long, but you aren’t likely to find much information on that subject because in today’s industrial farming system the cows are usually culled well before that. The assumption is that if you just give them enough food and get them to the right body weight before breeding, everything will be hunky-dory. Hmmm – I’ve seen plenty of teenagers who are the same size as adults. Does that mean they think and act like adults (insert loud laughter here)? Of course not, because their brains, organs and hormonal systems haven’t reached maturity yet. Why are cows different?
The accepted advice from the “experts” is that you should breed a heifer when she reaches puberty, which is usually around 12 to 14 months of age. That means that a heifer bred at 12 months will calve at 21 months – just shy of two years old. So the expectation is that this heifer should be able to continue growing (she’s probably only between 55% and 65% of her adult weight at breeding age) while providing enough nutrition to her calf in utero and then lactate for at least six months while also maintaining her own body condition. She will then have to handle the stress of birth, lactation and the resumption of her normal ovulation cycles in order to rebreed in a timely fashion. At about the same time she delivers her calf, she will be losing her two-year-old teeth, which makes it harder for her to graze in even a lush pasture.
Now, in humans, for whom there is no “economic benefit,” any GP or OB will tell you that women who have babies too early are more likely to have complications and that babies born small tend to have life-long health issues. Having seen that first-hand in my clinical practice, I have always opted to wait until a heifer is closer to two years old before breeding. Younger cows are more likely to have fertility problems after calving and produce less milk. Their calves are smaller and lighter than those of heifers bred when they are older. Despite the fact that their calves are smaller than average, in my experience those are the calves you have to pull.
Yes, it’s more expensive to feed a heifer a few more months before breeding. But in the long run, it’s better for her growth, better for her first and future calves and better for her overall health and longevity. Biological processes can’t – or rather, shouldn’t – be hurried.