Dan Lima
(Previously published in Farm and Dairy, December 21, 2017)
Pasture fields, unlike many annual crop fields, are typically comprised of multiple species of grasses, 
legumes, and forbs.
Some might even consider the word “forbs” and “weeds” to be interchangeable. Either way, pasture growth will usually translate to livestock gain when properly managed.
Chemical analysis for weedy forbs like redroot pigweed, lambsquarter, ragweed, dandelion, white cockle, and even immature Jerusalem artichoke have a comparative nutritional value to cool season grasses. Smartweed, shepherd’s purse, and yellow rocket, on the other hand, have very low nutritional value for livestock.
It is not just weeds, but what weeds that are present that will influence pasture quality.
Successful pasture management is linked to understanding how all the different species of forages grow, mature, and respond to grazing.
From the beginning
Let us start with grazing. Livestock will graze what they prefer to eat first and if they are still hungry will settle for what is left over. This is known as palatability.
There is evidence that livestock offspring learn how to graze from their mothers. This is especially important when using small ruminants like goats for clearing brush and unwanted weeds.
However, a plant’s chemicals and textures will influence an animal’s desire to consume that plant. Most grazing animals prefer a smooth texture in forages so they will avoid course, waxy, and thorny forages and forbs, if possible.
Plants can also produce chemicals for preservation that will make them undesirable to herbivores. Tannins are an undesirable chemical to livestock, and the quality of the food or forage rich in tannins is lowered due to its presence. Deer, cattle, and horses, for instance, will avoid grazing high tannin levels present in certain plants and fruits.
Tannins are found in some forages like birdsfoot trefoil and immature fruits.
The tradeoff in forages has always been that yield increases as total digestible nutrients (quality) decreases. This concept holds true for baling hay as well as grazing pastures.
Pairings
A great management strategy is to pair forages that progress to maturity at similar times for a more uniform harvest with high quality and yield. This could also increase animal palatability preference as well.
An example of grass and legume complementation pairing is red clover with timothy grass.
Timothy
Traditional, established varieties of timothy grass will mature later than the traditional potomac variety orchardgrass. Red clover will also transition to flowering (mature) later than white clover. Therefore, pairing a later maturing species of a grass and legume will allow that yield increase without sacrificing too much quality.
Additionally, both timothy and red clover will benefit from a higher cut (greater than 4 inches). The rationale here is that timothy has an apical meristem or growing point that is above the soil line usually between 3-4 inches; once the meristem is cut and removed, growth is terminated.
This property will make timothy better suited for hay production than grazing. Timothy grass will typically transition to reproductive stems in the summer, allowing for a higher quality and more delayed first cutting.
Red clover
Red clover is a determinate legume, meaning that the growing apex will terminate with the formation of a flower. This is important because it is at the transition from vegetative to flowering that quality starts diminishing in legumes as well as grasses.
If red clover is cut too early, the yield and quality potential of the legume is not maximized. These are some reasons why timothy and red clover are traditionally good hay type forages and pair well together.
Other forages
Conversely, the older, more traditional varieties of orchardgrass paired with alfalfa work well because of alfalfa’s increased rate of cutting.
Orchard grass will grow more quickly than timothy and can make for high yield and quality grass-legume mixtures in hay production.
Additionally, orchardgrass will remain vegetative in the summer, allowing for the growth of legumes such as white clover and birdsfoot trefoil to make an excellent companion legume.
Tall fescue and Kentucky bluegrass will also remain vegetative in the summer. These three grasses have their growing points closer to the soil level, making them desirable for grazing as well.
White clover, unlike red clover, has an indeterminate growth point and will continue growing laterally so that frequent cutting will not sacrifice yield. Another benefit of this lateral growth is the ability of white clover to fill in open areas in a pasture.
Breeding progress
A lot of progress has been made in forage breeding, and many varieties that were traditionally selected for seed production are now selected for vegetative growth.
In the previous example of the older potomac type orchardgrass, newer “later heading” varieties have been developed that have led to greater yield and quality orchardgrass forages.
There has also been great progress in the development of novel endophytes in both perennial ryegrass and tall fescue to prevent ryegrass staggers and fescue toxicosis respectively.
The take-home message is that newer seed varieties might be more expensive, but the benefits of using these technologies in agriculture will not only give greater flexibility but will increase the likelihood of a more profitable operation.
These profits can be generated from not only increased forage quality and yields but also potential increased animal health and productivity.
Understanding what you want and what you can obtain from your fields will help prioritize where to bale, graze, or even renovate. Even in terms of weed control, some weeds are more detrimental than other weeds found in a field.
Knowing what forages are present is the key to maximizing productivity, which will translate to profitability.