Winter feed stores are dwindling and the urge to get cows to grass is escalating. Turning cows out on immature forages too early can have consequences. The biggest challenge is to avoid permanent damage by overgrazing. If forages are overgrazed early, permanent damage of the stand is likely. Delaying turn-out until forages have reached eight inches in height is recommended. Even more important is rotating cows through pastures to maintain four or more inches of stubble height and giving the plants a rest period. In early spring, rotation should occur more frequently to keep up with faster growth and then slow as summer approaches.
Grass tetany is another concern with spring grass. This immature grass is very high in moisture and low in mineral content and dry matter (DM). The main culprit of grass tetany is deficiency of magnesium (Mg), this is why a "high-Mg" mineral is recommended. Start feeding the mineral 2-3 weeks before turnout. Calcium can also play a role in the equation as well, thus a calcium deficiency can also contribute. It is important to feed a high Mg mineral and check that Ca levels are adequate too. After you have the right mineral, they must consume it. If cattle are not consuming mineral at 3-4 oz. per head per day, the feeder should be moved more in line with daily travel and closer to the water source. If this fails to increase consumption, then direct feeding the mineral with a grain or co-product supplement is needed. Results of grass tetany to the cow can be dramatic: stumbling, staggering, muscle twitching and possible death. All within a very short amount of time.
The next problem is meeting nutrient requirements of cows out on spring grass. Because spring grass is lush, high in protein, and high in water content, it becomes hard to supply adequate nutrition. Mature cow size and milk production have increased in the beef cow population. This means that in cases, cows cannot physically eat enough grass to meet dry matter and nutrient requirements. Research at the University of Illinois, shows that cows will rarely consume over 100 lbs. of any feed due to fill and capacity of the rumen. However, a 1400 lb. cow will require 120-150 lbs of spring grass to meet requirement. In some cases when, grass is very immature and wet (<20% DM) the intake would need to be even higher. This means we need to intervene with a mild supplement level.
Producers can supplement cows with a dry feed that supplies ample energy. Protein is not the focus and needs to be limited in the supplement. Some options for supplement would be soyhull pellets, grass hay, cornstalk bales, or corn. A combination of these feedstuffs will provide DM to slow passage rate and energy to balance out the high protein forage. Research conducted at the Orr Beef Research Center showed a 15% improvement in Artificial Insemination conception rates when cows were supplemented on lush, spring forage. Cows calving from Feb. 1st to March 15th will be the best candidates for supplement because their breeding season overlaps the period of the lushest forage.
Low feed reserves may have many producers anxious to bale pastures. Remember, each ton of hay removed has approximately 40 lb of nitrogen, 20 lb of phosphate, and 50 lb of potash. This removal of nutrients for hay can decrease future productivity of the pasture if not replaced. Many times hay is not fed in the location it was removed from, thus nutrients are not replaced. Grazing will allow nearly 90% of the nutrients to remain on that pasture. Consider options to stockpile forage for fall and early winter besides harvesting hay.
Transition cows moving to pasture with a dry, low protein supplement. Match your cow size, milk production, and calving season with your forages. Managing forages correctly this spring can reduce dependency on purchased feeds and bring feed costs down for the remainder of the year. Controlling feed costs is the key to profitability in the cow/calf business. Grazing is the cheapest way to feed a cow, but it's hard to do with no grass.