Advancements in dairy reproduction have opened up new possibilities for producers. Now, farmers can make strategic decisions about from which specific cows their replacements could originate. This leads to a fundamental question: Are first-time calf-heifers or mature cows the best source for herd replacement?
To answer this, a team of researchers led by Dhuyvetter et al. analyzed data from 47 dairy herds. This vast data set, containing records of over a hundred thousand Holstein cows, aimed to estimate the effect of dam parity on early milk production (30-75 DIM).
Around 40% of the dairy herd is replaced annually with heifers
To eliminate distracting factors, the research team controlled for numerous variables including days in milk, seasonality, age at first calving, and instances of disease in early lactation, among others. Their findings are intriguing. For primiparous cows, milk yield was highest for those born from first lactation heifers (32.53 kg) and lowest for cows birthed by dams of fifth or greater lactation (31.98 kg). Interestingly, patterns across dam parity were similar in multiparous cows, but the mean values for dam parities 1–3 were not statistically different.
The average milk yield for a first-lactation heifer is 85% of a mature cow
Even though the differences in early milk production are slightly small, this analysis supports previous studies which recommend sourcing replacement heifers from heifers. On the other hand, even though cows in their fourth or greater lactation have shown to have longer lifespans, they don’t appear to be the best source for replacements in the herd.
- First-time calf-heifers produce the highest yield of milk.
- Mature cows, despite having a longer lifespan, may not be the best source of herd replacement.
- The reproduction strategy needs to depend on a wide range of variables, from disease occurrence to seasonality.
Dairy cows have a higher incidence of health problems compared to heifers
In conclusion, the decision of choosing between heifers and mature cows for herd replacement is not an easy one and requires careful consideration. Each comes with its own set of advantages, but according to data, heifers might just have the edge.
