Greetings everyone, I apologize for the long delay between these last two articles, but now that I’ve caught up on my research field and lab work, I can complete this two-part series. From July 29th – 30th the USDA Forage Research Center held the “Getting More From Forages” conference in Madison, Wisconsin explaining their current research efforts to account for ration variability on dairy farms and to improve forage crops and their management to meet the demands of the diverse range of dairy farms. Day 1 focused on animal related management and Day 2 focused on crop related management. This article focuses one of the more applied of the crop management presentations.

Targeted Plant Modifications: Pasture forages

Incorporating and Managing Superior Forages in Grazing-Based Dairy Systems: Geoffrey Brink

Geoff Brink of the USDA Forage Research Center began his discussion of pasture forages for dairy herds, by briefing describing what has happened to dairy industry in the last forty years. Back in 1960’s many farmers had unmanaged, open pastures while feeding mostly silage to their cows. This model of a dairy farm has changed dramatically on many acres across the US. Some farmers have decided to take advantage of the economies of scale by greatly increasing their herd size, land base, and reinvesting in bigger buildings and machinery. Most of these operations have eliminated pasture as a feeding strategy. At the other end of the spectrum are the farmers who, in some parts of the world, can rely completely on grazing to meet the feed requirements for their dairy herds year round. Dairy farmers in the US who wanted to rely more heavily on grazing looked to New Zealand and the United Kingdom for a system to put in place on their farms. A mixture of ryegrass and white clover works very well in these countries, but when the dairymen in the states tried this system they could not rely on this pasture mix for year-round forage.

Geoff Brink’s research focuses on quantifying how some of the other cool season grass species fit into grazing dairies. Figure 1 below is shows clearly the issue that most dairy man encounter when relying on cool season grasses in the Midwest.

Authors note: The difference in DM would be less between spring, summer, and fall in the Northeast as the rainfall is higher and temperature lower in the summer, but the overall trend still is true for cool season grasses.

For southern grazers—warm season grasses will be your main type of grass and you will see the most DM growth in the summer months, see Figure 2.

Figure 2. Complementary growth patterns of cool- and warm-season grasses

Graph from University of Arkansas: Forage Management Guide

As you can see from Figure 1 the amount of grass available from a pure stand of a cool season grass changes throughout the growing season—a bumper crop in the spring, much less during the dog days of summer, and some more during the fall. These differences are due to the different growth patterns of the plants throughout the growing season. Many farmers have tried to grow warm season grasses in a mixture with cool season grasses to solve this problem (Figure 2). However local climate and/or management choices can limit the potential of this system in some situations.

Besides the yield differences in cool season grasses, forage quality also changes throughout the growing season, which where Geoff’s research comes into the picture. He examined how stem weight, leaf weight, NDF, NDFD, and CP changes throughout the growing season in several cool season grasses: smooth bromegrass, reed canarygrass, meadow fescue, timothy, quackgrass, tall fescue, and orchardgrass. These grasses are listed in decreasing order of winter-hardiness, a very important consideration for farmers with long, cold winters. He conducted small plot research with all of the above grasses and a separate grazing trial with dairy heifers grazing pure stands of meadow fescue, quackgrass, reed canarygrass, and orchardgrass. An overview of the general trend Mr. Brink found in his small plot research is shown by Figure 3 below.

Figure 3: Changes in Nutritive Value of Cool Season Grasses

These differences are easily explained by reviewing how a cool season grass grows. Stems tend to grow quicker in the spring and make up larger percentage of the pasture sward than the leaves if the pasture is not grazed or harvested by the appropriate growth stage. The reason that the neutral detergent fiber digestibility (NDFD) and crude protein (CP) are falling rapidly from the beginning of May to the start of June, while the neutral detergent fiber (NDF) is quickly rising is because the cool season grasses have entered their reproductive cycle and are heading out. This is why timing of first pass of grazing and the first cutting of a mixing of grass-alfalfa silage is so important. When the grasses are in the boot stage of growth (seed head just visible out of the top of the stem) in the spring they need to be grazed/cut soon before their quality declines. An even better strategy for grazers would to start grazing during stem elongation so if the grass really starts growing they can stay ahead of it in all their pastures. It’s also worth considering just harvesting a pasture or two for hay or silage for the first crop, storing it, and then feeding it during the “summer slump” when the pastures aren’t as productive.

The NDF, NDFD, and CP don’t change much the rest of the summer because the grasses stay in the vegetative growth stage for a longer period of time. However the quality of all grasses will still decline as the grasses move the stem elongation stage, into the boot stage, and even further in the reproductive phases of growth. Furthermore the quality of the leaves later in the summer is lower than the leaves earlier in the spring. Geoff Brink demonstrated this during the grazing trial and is shown by Figure 4 below.

Figure 4: Digestibility of Grass During a Grazing Season

Authors note: Grazing Period 1 = Spring, 2 = Summer, 3 = Fall. These measurements were taken from heifers on pasture and not a lab analysis.

All the four grass species had low digestibility in the Summer and Fall compared to the spring. Again this is expected given the weather patterns of the Midwest and the life cycle of cool season grasses.

From his small plot work Geoff concluded that tall fescue would be the best choice because of its high yield and reasonable quality. However some growers with very harsh winters ( i.e. Northern MN and WI and western MN and some parts of IA) may want to consider more winter hardy grass. From the grazing trial Geoff recommended planting meadow fescue because of its high digestibility, good yield, and high palatability. Geoff’s complete presentation can be found by click on this link or the title in italics.

To view all of the presentations from the “Getting More From Forages” conference click the link below.

USDA Dairy Forage Research Center Presentations

If you would like see an article on a certain topic make a comment below or send an email to bverbeten@gmail.com. The next series of articles will be focusing on managing the fertility of hay fields.