To stay competitive, organic dairies and other graziers should produce high-quality forages, maximize what their cows are taking from pasture and supplement with grain, says Brad Heins, Extension specialist in organic dairy management at the University of Minnesota (U of M).

“Inadequate supplementation can limit milk production in grazing milk cows,” he says. “Forages alone will not support maximum milk production.” He recommends 5-6 lbs/cow/day of grain.

For each pound of grain fed, producers should expect 4-5 lbs/cow/day of milk produced, he adds. “Of course, economics will drive supplementation levels and what is supplemented.”

Grain makes cows better able to absorb crude protein from pasture, because it and the silage in a total mixed ration (TMR) can slow the passage of forages through the rumen. Corn, a fermentable carbohydrate, also increases microbial growth in the rumen, which results in more energy for the cow to produce milk, he says.

Even so, grain-supplemented cows were less profitable than those fed only pasture because of higher feed costs, shows a 2012 U of M West Central Research and Outreach Center study. Cows were fed diets of 100% organic pasture, low grain (6 lbs organic corn plus about 46 lbs corn silage, haylage and mineral in a TMR) and high grain (12 lbs organic corn in a TMR).

Those consuming 100% pasture had an income-over-feed cost of $3.61/cow/day compared to 38¢/cow/day for cows fed the high-grain diet and $2.20 for those on the low-grain ration.

When supplements make economic sense, corn is usually the first choice. But Heins also suggests alternatives:

  •  Barley, which has 95% of the energy of corn and high fiber,
  •  Oats, offering 90% of the energy of barley and higher fiber,
  •  Wheat, which has high protein and energy similar to that of corn,
  •  Peas, high in protein and with a similar energy level as wheat.

When switching to grass-only diets, producers should monitor milk production, protein level, manure (for undigested particles) and body condition, he says. Heins recommends that all producers balance their rations to meet requirements for energy, rumen degradable protein and microbial protein in order to avoid high milk urea nitrogen (MUN), which can lead to health and fertility issues.

New graziers shouldn’t try pasture-only diets because they require highly skilled pasture management. Producers who do opt for them should gradually increase pasture intake and decrease supplementation to allow pastures, animals and management to adjust. Once on 100% pasture, cows may produce excess ammonia that can cause a drop of 3-6 lbs/cow/day of milk and affect reproduction, he warns. Producers may also need 50% more pasture to provide well-managed, high-quality forages.

Pasture-based dairy cows do yield less milk, but that’s because of reduced dry matter intake (DMI), not forage quality, Heins says. He urges producers to think of inputs in terms of cost per hundredweight of milk: “One pound of extra pasture DMI equals 2 lbs more milk.”

But the amount of pasture dry matter available depends on plant height, density and diversity. Dry matter consumed will be affected by whether cows were bred to be good grazers, the amount of energy needed for milk production, the size of the animals and their digestive tracts, and overall grazing behavior.

“To get the most DMI from pasture, producers should have excellent soil fertility as well as diverse species in pastures,” Heins says. “No single species has all the value. Diversity is key.” Before choosing species, consider their total yield (for example, tall fescue), yield distribution (orchardgrass), forage quality (perennial ryegrass, meadow fescue) palatability (timothy), grazing tolerance (alfalfa, bromegrass), persistence (bluegrass) and ease of establishment (red and white clover).

Paddocks should be rested adequately between grazings, and cows should graze eight to nine hours and consume three to five major meals each day. Traditional milking times aren’t optimal for grazing herds, because cows would graze two to three hours at dawn and four to five hours around dusk, Heins says.

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