After many decades of housed dairying some US dairy farmers a moving back to grazing cows on pasture, Mike Lamborn reports.

Many years ago, grazed pasture was a major forage source for United States dairy cows. However, in the late 1950s, dairy farmers began moving toward confinement systems.

Cheap, highly available commodity feeds, a desire for more cows and higher per-cow production drove dairy farmers across the US to house or dry-lot their cows. In turn, valuable, fertile pasture was transitioned into high-quality forage production with the lion’s share going into corn and alfalfa for silage.

Recent figures show that in the last 10 years, the number of dairy farms in the US has decreased by 40%-plus, herd size has increased by 60% and average milk production per cow has increased by almost 25 to nearly 23,000 pounds per cow. In New Zealand numbers, that equates to 842kg milksolids/cow.

There are some rare exceptions, but for the most part, US graziers’ herds range in size from a handful of cows to about 1200 at the high end. Grazing platform size and logistical distance from the milking parlour are the biggest barriers to large-scale grazing.

Most grazing dairies in the US are what we call hybrid operations (extreme system 5 in NZ). This basically means they are set up to feed proportionate amounts of grain ration in the parlour or a total mixed ration (TMR) on a feed lane or pad.

That said, there is a growing ‘clique’ of dairymen who graze their cows simply because they are passionate about it and believe in it. Some graze in an attempt to reduce rising input costs. Some do it as a way to deal with the extreme volatility of the market, which is difficult for small producers to manage. Others are taking advantage of high-value milk markets such as organic and 100%-grass-produced. Whatever the reason, it is safe to say pasture-based dairying is alive and well in the US.

Most grazing dairies in the US are what we call hybrid operations (extreme system 5 in NZ). This basically means they are set up to feed proportionate amounts of grain ration in the parlour or a total mixed ration (TMR) on a feed lane or pad.

The amount fed is dependent on pasture/forage quantity and quality. The extremes of the US climate play a huge role here too. The high summer temperatures (32C-plus) in the southeast and parts of the mideast are the No. 1 cause of reduced drymatter intake (DMI) of grazed pasture. Consequently, the US dairyman can maintain total DMI and production levels by balancing the daily intake with an amount of feed concentrates.

As is the case in NZ, well-managed spring pasture is always the most nutritious and carries the highest total digestible nutrients (TDN). Because of this, dairy graziers in the north tend to calve most of the herd just ahead of the spring to capitalise on high TDN pasture (perennial ryegrass, clover, tall fescue and cocksfoot).

While total seasonality is extremely rare in the US, calving for the onset of high-quality pasture does lean towards graziers being somewhat seasonal.

In the southern parts of the southeast, seasonality is a must to capture high- quality cool season annual pastures that are drilled into dormant perennial Bermuda grass. Because of the south’s moderate winters, calving takes place in the fall (autumn) and the grazing onset of cool season pastures (annual ryegrass, winter wheat, oats, cereal rye, barley and annual clovers) can be as early as the middle of December.

While various varieties of perennial Bermuda grass in the south and southeast provide the bulk of annual dry matter grown per acre, winter annuals provide dairymen with high volumes of quality grazable pasture to capitalize on optimum grazing weather and forage growth.

Winter annual pasture growth rates are maintained by strategic applications of nitrogen fertiliser. The rule of thumb is about 50 units of nitrogen per acre with two to three applications from emergence through to the onset of new bermudagrass growth.

The most popular product used is ammonium nitrate because it tends to have less volatilisation than urea. Sulphate of ammonia is seen as having too slow a response rate. Good operators in the southern region can get 300-plus grazing days in a season.

In summary, grazed pasture represents the cheapest source of TDN for dairy cows. Management of dairy cows and pasture is a major challenge, given the variation in pasture/forage growth and grazing conditions during the grazing season.

Providing adequate available pasture that has a dense sward will maximize the intake/bite and maximize pasture intake and low-cost milk production. Allocation of the correct amount of area and pasture to achieve maximum intake is an important decision that the US grazier must make each day.