HOLSTEINS NEED to be managed properly from birth to achieve their genetic potential because it is impossible to make up for lost opportunity later on.
That is the conclusion of SAC researcher Mike Coffey, reporting data comparing the heifer growth in the Langhill herd‘s two lines – one selected for maximum production – Select – and one for average production – Control.
Despite being managed as one group, Select heifers grew at 1kg a day compared with 0.89kg a day for Control heifers.
Select heifers‘ maximum growth rate also occurred earlier in life and they were bigger at first calving.
“But by the end of three lactations, when the animal reaches maturity because it stops building up muscle, there was no difference in liveweight,” added Dr Coffey.
He believes breeding primarily for milk yield has led to heifers which grow faster, but this may have consequences in later productive life.
“Select heifers are also sexually mature earlier and are more willing to lose weight.
“This contributes to the less robust nature of Holstein cows – less healthy, less thrifty and less fertile.”
The result is heifers putting everything into a 10,000kg first lactation, yet failing to perform afterwards.
Heifers not fed to their potential from the start of life alter their own growth curve. The result is odd-looking animals with bones and internal organs not developing at the correct rate, he said.
“This legacy lives with them for the rest of their life and can‘t be undone by feeding rocket fuel in the first lactation. The heifer‘s mammary gland, internal organs, muscle and bone all mature at different rates, so once on a better diet, she lays down fat.
“Lifetime productivity is a combination of not growing too fast or too slow and not losing too much weight. This means feeding the right amount at the right time.”
He believes growth rates up to first calving could be incorporated into an overall breeding index to optimise lifetime performance and fitness.
Such a breeding policy could lead to lower culling rates and fewer heifer replacements needed, although it is not yet possible to calculate the economic impact.