Pat Hoffman, Vita Plus – Real World Sources of Variance in Heifer Performance
Article written by Macy Sarbacker
You’ve got a wobbly-legged, newborn heifer calf. She’s still wet and you’re drying her off. What do you know about the kind of cow she’s going to be? Are all calves born with the potential to become great dairy cows? What is the balance between heifer management practices, calf diseases, genetics and future milk production?
Though we can’t answer all of these questions, Pat Hoffman, dairy technical specialist with Vita Plus, took a stab at explaining the real world sources of variance in heifer performance that we see daily on dairy operations. He posed several questions to Vita Plus Calf Summit attendees to highlight these sources.
Shouldn’t all dairy heifers have high genetic potential because we have used A.I. breeding for so long?
Though genetic improvement is taking place and most would guess that genetic variance for milk production among dairy heifers has narrowed due to long-term use of A.I. breeding, two heifers from the same bull and cow can have vastly different milk production potential. Just as siblings from the same mother and father typically have all different heights, weights, hair color, etc. Fortunately, we now have the technology of genomic testing that can be used to give us insight to predict the future milk production of a dairy heifer.
Is the age at first calving one of the most important dairy heifer management benchmarks in regard to lifetime milk production?
In the past, age at first calving seemed to be one of the most important factors in determining lifetime milk production. But according to new research, producers should not continue to push to calve dairy heifers before 24 to 25 months because there does not seem to be a first lactation or lifetime milk production benefit, but there is increased raising cost in association with calving in heifers early. Additionally, calving dairy heifers at less than 22 to 24 months does not seem to give up much significant economic benefit nor does it alter lifetime days in milk or lifetime milk yield. The bottom line is that, the earlier a heifer calves, the earlier she leaves the herd.
How do calf and heifer diseases, such as scours, coccidiosis, crypto and pneumonia, affect future milk production?
In a recent study at Virginia Tech, these common calf diseases decreased growth rates of heifers and increased age at first calving, but the milk production variance was difficult to define. In this particular study, single cases of calf respiratory or digestive diseases did not have a major impact on future milk production. Other studies that have been reported have shown mixed results and findings, not conclusive with the above findings. Hoffman said the takeaway message is that it is very difficult to exclusively measure milk yield losses in reference to common calf and heifer diseases.
So how exactly do we know the answers to all of our questions?
The truth is that we don’t, Hoffman said. The variance that we see in our dairy heifers is certainly caused by something. Whether its genetics, environment, or calf and heifer diseases – or a combination of them all – we still can’t be 100 percent sure.
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