Avoid dairy-cow transition to disaster
Think about transition cow management in terms of all the changes going on in a dairy cow’s body. Going from a pregnant, nonlactating state to being non-pregnant and lactating — her hormones are changing like crazy.
She goes from ravenous hunger to picky eating. Unless well-managed, she’s a recipe for a metabolic meltdown: milk losses, treatment costs, poor reproduction and likely increased cull rates.
The transition period runs from three weeks before calving to three weeks after. During the three weeks before, her intake declines while nutrient demands increase. The most severe drop occurs in the last week before calving, when intake can fall as much as 30%.
• Raging hormone changes make dairy cows candidates for metabolic meltdown.
• The biggest culprit is overfeeding energy, not dry-matter intake.
• Corn silage, hay, minerals, vitamins and protein even her intake.
I believe the key to a successful transition is minimizing the drop in dry-matter intake, especially during that last week. And that’s a challenge because of extreme hormonal changes — and a growing calf that’s displacing her digestive tract.
Overcrowding, inadequate feed-bunk space and poorly formulated and delivered diets can complicate matters. But the biggest culprit in dry cow diets is overfeeding energy.
Avoid this ‘metabolic syndrome’
Dry cows that are overfed energy before calving have what’s known in human nutrition as “metabolic syndrome.” It results from an accumulation of abdominal fat.
Free fatty acids mobilized from the abdominal fat go directly to the liver. Since the liver has limited capacity to export these fatty acids, some of it’s stored as triglyceride. Some is completely oxidized to energy. The rest is incompletely oxidized to ketones.
Issues arise when liver triglyceride content reaches 20% by weight. Liver metabolism becomes sluggish, and further uptake of fatty acids results in ketone production — not good.
Compounding matters, that abdominal fat accumulation leads to insulin resistance. Normally, insulin blocks or slows fat mobilization.
But insulin-resistant cows don’t respond to the insulin. So the floodgates stay open and the mobilized fatty acids continue to swamp her overworked liver.
Overfeeding energy during the dry period adds to the lipid flow and insulin resistance. To complicate matters more, the increased metabolic rates in the liver signal to the brain to shut down intake.
The solution is ...
Cows fed lower-energy diets (0.55 megacalories per pound) during the dry period don’t experience metabolic syndrome or insulin resistance. With a more moderate influx of fatty acids into the liver, the liver able to keep up. And, the lower metabolic rate means there’s no chemical message shutting off hunger signals.
Consistent intake also means a full rumen and happy rumen microbes fermenting feed, growing, reproducing, dying and eventually washing to the small intestine, to provide the cow with a high-quality source of amino acids.
So, what should you feed your dry cows? I start with corn silage.
• Generally, mature Holsteins eat around 25 pounds of dry matter in the far-off dry period. So, my dry-cow diets usually contain 18 to 20 pounds of dry matter from corn silage, and 3 to 5 pounds of good-quality (but lower nutrient-density) dry hay. First cutting hay works well.
• The remainder of the diet is a mineral-vitamin mix, plus soybean meal for rumen-degradable protein or a source of rumen-nondegradable protein (distillers grain or heat-treated soybean meal), as a carrier for the mineral-vitamin mix.
• Fermentation enhancers also work very well in these diets.
We have a one-group dry-cow system, so we don’t have a close-up dry-cow diet. However, research indicates that cows fed a low-energy, far-off diet can be fed a more nutrient-dense, close-up diet, while still gaining the benefits of the low-energy, high-bulk, far-off diet.
Carson and husband Steve partner in Harkdale Farms of Newbury, Vt. She’s also a professor at Vermont Technical College.
EASE BACK ON THE ENERGY: Saving that $7 corn for when cows finish transition helps avoid metabolic syndrome, says Carson, and better converts that energy to milk.
This article published in the May, 2011 edition of AMERICAN AGRICULTURIST.
All rights reserved. Copyright Farm Progress Cos. 2011.