Lush pasture is not all good

After a winter of snow, mud, feed supplements, and moving bales in subzero weather, opening the gate to spring pastures is a welcome transition for both cattleman and cow.

Early spring pasture growth is the equivalent of rocket fuel for grazing livestock; in fact, said Travis Meteer at January’s Driftless Region Beef Conference in Dubuque, Iowa, it’s so good in quality that nutritional problems can arise. The University of Illinois beef specialist outlined three feeding challenges associated with initial spring pasture growth.

Low dry matter

“Wet, washy grass can frequently be below 25 percent dry matter," Meteer said. “This makes it hard for the cow to consume enough dry matter to meet energy demands.”

Meteer explained that grass containing 80 percent water requires that a 1,400-pound, lactating beef cow with average milk production consume 138 pounds of fresh grass to meet energy requirements. A high-milking cow would require additional consumption.

“In most cases, the cow fills up her rumen between 100 and 125 pounds,” noted Meteer. “Physical fill of the rumen can be a limiter on performance when grazing washy, high-moisture grass.”

High protein

The second challenge posed by grazing lush grass is the high protein content coupled with moderate energy value. If energy content is limiting, excess protein is converted to ammonia, which enters the blood stream and eventually is converted to urea by the liver. It is then excreted in the urine.

Though different opinions exist, Meteer explained that excess protein has been associated with reduced reproductive efficiency. An overload of ammonia in the blood can also reduce the capacity of red blood cells to provide oxygen to cells.

“I have seen cattle panting after being on lush, green grass for a few days,” Meteer related. “It wasn’t a heat-stress issue but rather a situation where there was too much ammonia and not enough system oxygen.”

Low fiber

A third issue with early spring forage is a lack of fiber. Meteer explained that immature forage results in high passage rates and an “unsatisfied cow.”

Mitigation strategies

“Solutions to the short-term problems inherent with early spring pasture grass are numerous,” Meteer said. “The key is to provide a balanced ration, which lush pastures typically are not.”

The beef specialist suggested the following strategies to mitigate the nutritional issues associated with immature spring forage:

· Delay pasture turnout to let forage mature longer.

· Supply dry, baled forage that is low to moderate in protein. This raises ration dry matter content and helps slow rumen passage.

· Supplement grains at less than 0.5 percent of body weight to ensure adequate energy.