Dr McConochie set the scene by challenging the thinking around how accurate we really are at estimating mature bodyweights. Historically producers have used cull weights to estimate the herds typical mature weight however, this is fundamentally flawed as those animals selected for culling are outliers from the herd. They have been selected to be culled for various reasons, but they all have one thing in common – that cow is no longer considered productive in that dairy system. Dr McConchie said, “Estimating a cows mature body weight by eye is impossible, just as it is to estimate the body composition of fat to muscle ratio”. Getting accurate bodyweights at different stages of lactation is crucial to accurate rationing of those cows due to the impact body weight has on nutrient demand.
Building Muscle for Lactation Success
Dr. McConochie challenged attendees to rethink how they assess mature body weight and muscle development in their herds.
We need to consider age of first service in replacement heifers. “When should we be breeding our heifers? Are they grown well enough? Are they too fat or too thin and have they built enough muscle?” These factors should be all considered before deciding what age we look to breed our heifers.
“A heifer’s ability to build muscle during growth directly impacts her milk production potential in the first lactation,” Dr. McConochie explained. Heifers with insufficient muscle reserves are more prone to social bullying, reduced feed access, and lower milk yields. Additionally, muscle tissue serves as a critical energy reserve during early lactation, supporting milk production when energy demands are highest.
Currently it is difficult to differentiate on-farm between fat and muscle in our animals and, just like bodyweight, it’s impossible to do by eye. Dr. McConochie encouraged producers to consider innovative methods, such as muscle depth ultrasound scanning, to assess muscle reserves. Research from Purdue University has shown that cows with greater muscle reserves prepartum mobilise more muscle during early lactation, resulting in higher milk yields. This underscores the importance of providing heifers with balanced diets that include adequate concentrates and high-quality protein to support muscle growth.
Practical Takeaways for Producers
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Feed the Rumen First: Prioritise rumen health by supplying essential nutrients like BCVFA through Zinpro IsoFerm. This supports fibre-digesting bacteria, enhances protein and energy utilization, and improves overall cow performance.
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Focus on Muscle Development: Ensure heifers receive balanced diets with sufficient protein and energy to build muscle reserves. This sets the foundation for higher milk yields and better health in the first lactation.
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Measure, Don’t Guess: Regularly weigh cows and consider advanced tools like muscle depth scanning to accurately assess body weight and muscle reserves. This data is crucial for precise rationing and optimizing performance.
By adopting a “Rumen First” approach and prioritising muscle tissue deposition in heifers, producers can unlock the full potential of their herds. These strategies not only improve milk production but also enhance cow welfare and long-term profitability.