Fresh cows must meet high standards. After calving, they are expected to reach peak milk yields quickly and conceive another calf within 85 days. It's a formidable challenge and a cow's ability to meet it grows with good nutritional management during the six-week transition period. Cows entering this transition period – from three weeks before calving through three weeks after calving – are at a critical stage.
"Changes occurring during this time place enormous physiological demands on the cow," says Jerry Olson, DVM, technical services consultant for Pharmacia Animal Health. "Management and feeding practices in the last three weeks of the dry period profoundly affect disease incidence in the early fresh period."
Olson advises dairy producers to use four main feeding strategies during the transition period, to head off diseases and infections post-calving.
1. Prevent decreased concentration of calcium in the blood or serum (milk fever). Milk fever and subclinical hypocalcemia puts cows at greater risk for several diseases following calving that can reduce the chances of conceiving and result in greater risk of culling or even death. Adjustments in the close-up dry-cow ration that will help prevent milk fever include:
a) conducting forage analysis to determine sodium, potassium, chloride and sulfur content;
b) using low-potassium forages;
c) formulating transition rations with the lowest practical dietary cation-anion difference;
d) avoiding buffers; and e) using either anionic salts or commercial concentrates treated with hydrochloric acid at the advice of your herd nutritionist and veterinarian.
2. Avoid severe negative energy balance immediately after calving. Increasing the energy density of the ration to compensate for reduction in dry-matter intake is crucial. Otherwise, cows can enter a state of severe negative energy balance, leading to excessive fat breakdown that's detrimental to liver function, causing ketosis or fatty liver syndrome. Encourage higher dry-matter intake by offering highly palatable feeds and avoiding cow overcrowding.
3. Prepare the rumen for high-concentrate diets that will be fed following calving. Abrupt switches to high-energy lactating diets can lead to ruminal acidosis. Adapting the rumen microflora to a high-starch diet requires three to four weeks. Because of this adjustment period, grains should be introduced during the final three weeks of the dry period.
4. Minimize decreased immune function associated with calving. Changes associated with calving can suppress the cow's immune system. After calving, blood serum levels of vitamin E drop 47 percent; retinol levels decline 38 percent; and zinc drops 67 percent from baseline levels before calving.
5. Supplementing additional vitamin E, vitamin A, copper, zinc and selenium can help maintain immune function. Negative energy balance also has a strong immunosuppressive effect.
Because management systems and disease profiles vary on a herd basis, ask your herd nutritionist and veterinarian for specific recommendations for your transition cow nutrition program.