When you go to dairy weaner sales, and see the variation in size of calves that have been "reared" by sincere folk presumably trying to do a good job, you wonder how they got it so wrong. They must not realise the importance of good rearing. It is important because:
- The theory says that growth follows an S-shaped curve, and each stage on it affects the next one along. So birth weight strongly affects weaning weight, which then affects weight at puberty, which then affects weight at maturity.
- As puberty is controlled more by weight than age, well-reared calves will reach puberty earlier. This is vitally important for farmers rearing females that they want to mate as yearlings.
- Well-reared heifers get pregnant easier and earlier, and these go on to be more fertile and productive cows over their lifetime.
- Well-reared calves for meat production (bulls, steers, and heifers) will reach slaughter weights earlier than poor-grown calves and return more profit in a shorter time.
There is just no point or profit in rearing poor calves. You put the same work into them as you do good ones - so make sure you make a success and get some return out of calf rearing.
This is a bit of theory that says that when animals have had their early growth slowed or stopped for a while when the feeding level is restored to normal, they will then catch up to where they would have been before. They are supposed to "compensate" for their period of starvation. In practice, they don’t do any such thing. They may try to but rarely achieve it.
All that happens is they may improve a bit, but they just continue to grow up their previous lower growth curve. They get to their target weight eventually so do catch up - BUT they need extra time and consequently extra feed because they have been on the farm that much longer.
So stopping or slowing growth in young calves is a disaster from all points of view. It has permanent long-term effects on their production. It has also locked up capital for longer and slowed the rate of return.
Buying little miserable calves at weaner sales that the auctioneer says, "only need a good feed and time to eat it" - is utter rubbish. They will never get over their poor rearing and you’ll get to know them well as they’ll be on the farm for much longer than well-reared calves.