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Math of the Transition Cow 🧮

Our dry cows have been holding well on dry standing feed with loose dry or wet lick, but as they transition to very late gestation and lactation, the maths changes completely:

  • A dry 500kg cow needs at least 60MJ of ME everyday.

  • Frosted standing native pasture has been nutrient leached, and is now testing on average 6 MJME/kgDM, 6% CP & NDF of 70%. Tropicals are testing less again.

  • The high NDFs (measure of structural lignin/carbs) in these dry standing feeds is significantly limiting intakes. An adult cow for example will therefore only be able to eat 9.5kg DM per day using the NDF intake equation instead of at least 14kg if using 2.5% of body weight on readily digestible feed.

  • This equates to 57MJ ME per day. Pretty much maintenance.

  • Proper lick management increases this intake and therefore energy provision 10-20% which has held dry cattle well.

  • But calving cows maintenance energy requirement spikes to at least 90MJ per day (not including further additions for walking & cold).

  • This puts them into approximately 30MJ energy deficit per day. About 1kg of weight loss daily. Or a whole condition score about every 40 days.

  • Cows can loose weight, sometimes that’s their job, but it must be on our terms, and as long as they have the weight to loose. We can’t afford for it to be at the detriment of calf production. Cows in negative energy balance will also milk less and be at increased risk of disease.

  • If cows are going into calving in BCS<3 on natives or tropicals, be super mindful of uncontrolled weight loss, we need to get through until that calf is weanable (at least 120kg), or a spring break!? Enter the need for allocating better temperate pasture or winter crop if its available, or supplementing their energy deficit with hard feed, as some producers have already been doing for some time.

In brief, calving cows will NOT maintain weight on the average dry native and tropical grasses even with lick this year.

If you want help to crunch some numbers, feel welcome to reach out. Here’s praying for some rain!

Frosted native pastures in the district are averaging 6 MJ ME / 6 % CP or LESS.


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