Dr. Darrell Emmick shared his experience with animal foraging behavior and explained how to train livestock to eat weeds. This talk was part of a workshop called “From We-Feeders to Weed-Eaters: Controlling Weeds through Animal Grazing” hosted by Watson Farm in Jamestown, RI. A three-year Sustainable Agriculture Research & Education (SARE) “Grass-fed All Year Long” grant awarded to UConn, UMass and URI funded the workshop. Dr. Emmick also spoke at two similar workshops in Litchfield, CT and South Deerfield, MA. Joining him were experts from each state speaking on weeds and forage.
Animal Foraging Behavior
According to Dr. Emmick, animals learn what to eat through the interactions of two interrelated systems: affective and cognitive. The affective system operates without any conscious thought on the part of the animal using feedback from osmotic, chemical, and mechanical receptors within the gut to evaluate the chemical and nutritional composition of foods eaten relative to the animal’s nutritional requirements. This is “Post ingestive feedback”. If they feel good or energized after eating a certain food, they will eat it again. If they feel uncomfortable, bloated or sick afterwards, they are not likely to eat that food or plant again. The cognitive system uses information gained through the senses of sight, smell, touch, and taste as well as social learning – like Life cereal’s “Hey Mikey” commercial. Generally, babies eats what they see their moms eat. Animals also learn from other adventurous animals in their group.
Plant Nutrition vs. Toxins
Food is something eaten or drunk that meets our nutritional needs. A toxin is something that can make an animal sick. In small doses, toxins can act as a medicine. In large doses, toxins can kill. Dangerous or tolerated doses vary with animal age and health.
Healthy young plants grown in ideal conditions typically contain lower concentrations of toxins– alkaloids, terpenes, phenolics and glycosides– relative to nutrients such as protein, carbohydrates, lipids, nucleic acids. This often changes for the same plants growing in less than ideal conditions. Cool-season plants grown on hot dry southern slopes are most nutritious and least toxic during spring and fall.
Plant nutrients vary with time of day. Plants are typically less nutritious in the morning than at the end of the day. Photosynthesis – the creation of carbohydrates in plants – stops when the sun goes down. Plants use stored carbohydrates overnight.
Legumes always have more nutrition than grass, even in the morning. Most animals start their day with legumes like Dr. Emmick’s favorite forage, white clover. Animals switch over to grass or other forage when their “conditioned taste aversion” kicks in. He explained this works just like our own ability to stop eating fresh baked cookies right out of the oven (eventually). After a certain amount of a particular food, our bodies tell us it is time to add something new (like a glass of milk with the next cookie) or for a different food altogether. This “conditioned taste aversion” prevents animals from eating the same food all day, every day which helps balance nutrition and toxin intake.
Animals use protein and energy to process, eliminate or neutralize toxins in their digestive systems. When processing large levels of toxins, they produce less milk or put on less growth than with a diversified diet.
Almost all forage plants contain some level of toxin along with their beneficial nutrition. Plants develop lower nutritional quality and higher or dangerous levels of toxins when subject to herbivory (pest or livestock browsing) or stressed plants growing in harsh climates, extreme summer heat, poor soils or excessive shade.
Some toxins neutralize each other during digestion. The order plants or toxins are eaten matters to digestion, explained Dr. Emmick. Tall fescue contains alkaloids which upset rumen function and intake. Birdsfoot trefoil is high in tannins. If an animal eats tall fescue first, its intake will drop if later provided birdsfoot trefoil. If an animal eats birdsfoot trefoil first, intake will remain high when provided with tall fescue. The tannins in trefoil bind with the alkaloids and reduce their influence. There are many plant-herbivore interactions: nutrient-nutrient, nutrient-toxin and toxin-toxin interactions which are just now being discovered.
Nutritional Needs of Cattle
Dairy animals need 16% crude protein. High quality pastures can offer 30% crude protein. Dr Emmick worked with Dr. Provenza in the Department of Wildland Resources at Utah State University studying animal grazing behavior and diet selection. Learn about Dr. Provenza and his team‘s work here. In one study, they learned that dairy cows can self-select the foods with protein levels they need. If you feed them 11% crude protein in the barn, they will select high protein foods (clover) on pasture. If you feed then 21% crude protein inside, they will select low protein foods (grass) afterwards. Don Minto of Watson Farm confirmed that his cows “know” what they need. Minto described using a varied mineral free choice system allowing the animals to self-select their minerals rather than offering one single blend.
While Dr Emmick appreciated the need to analyze forage quality, the results will vary considerably by season, temperature, moisture levels, time of day and life stage of plant. He said, “the cows will figure out what they need.” Computer models recommending feed blends are humans’ attempt to understand the animals’ dietary requirements. While these models offer a reasonable place to start, they are not as accurate as we would hope
Forage and Grasses
Kentucky31 Tall fescue is the main feed for many cattle across the Midwest. It is one of the few cool-season grasses that can survive their hot summers. Unlike most prairie grasses, during hot summers, tall fescue produces toxins including an alkaloid called ergovaline (an ergopeptine). These compounds are vasoconstrictors. Animals eating tall fescue can develop fescue foot where the capillaries in their hooves burst and bleed. Some lose the tips of their ears. Their ability to thermo-regulate can be compromised, thus animals spend extra time in farm ponds trying to stay cool. Plant breeders have developed endophyte-free versions of tall fescue without this alkaloid. Unfortunately, there are still at least two other toxic compounds in tall fescue that affect cattle rumens. Dr. Emmick recommends against including tall fescue in any forage blends. Dairy cows that eat this grass as their primary feed can produce 12-14 pounds less milk per day than those with a more diversified diet.
When forage grows too tall, the fiber or dry matter content increase so much that animals may not want to eat it. Farmers will benefit their animals by mowing or haying tall pastures. The new growth will be more nutritious and more appealing to livestock.
Grazing as Weed Control
For maximum weed control, Dr. Emmick recommended mowing or grazing unwanted pasture weeds when they are forming flowers. Plants use a lot of energy to create those flowers and have less stored energy to regrow. Cool-season weeds are best mowed and grazed during late spring or early summer. Warm season weeds like goldenrod, that flower in late summer, are best mowed and grazed in mid to late summer. Animals will happily eat the new growth after a mid to late summer cut.
Training Livestock to Eat New Plants
Farmers can train their animals to eat new plants and weeds. Dr. Emmick recommends selecting one or more adventurous healthy animals. Harvest young, strong, healthy weeds. Mix a few into a bucket with favorite grains or in the barn with haylage. Dr. Emmick remembered being trained to eat mutton with mint jelly as a child. He recommended drizzling a little molasses over the top of unfamiliar weeds to make them appealing. Each day add a larger portion of the ‘weed’ to the mix. After a week to ten days, bring animas to a pasture with those same weeds. You can lightly spray the weeds with molasses for the first few days. The animals should be ‘trained’ to eat them.
Read how Kathy Voth trained her animals to eat leafy spurge here.
Grass Fed All Year Long
Through a SARE grant, the universities of Connecticut, Massachusetts and Rhode Island, work to increase production of local meat in the region. Learn more here and here.
Dr. Darrell Emmick is the former State Grazing Land Management Specialist with the USDA-Natural Resources Conservation Service in New York State. He can be reached via email at firstname.lastname@example.org or call 607-844-3211
The workshop series was part of a 3-year USDA/NESARE Professional Development Program grant: Grass-fed All Year Long, a joint project among the Universities of CT, MA and RI coordinated by Michael T. Keilty, UCONN Sustainable Agriculture Systems Educator. Other state representatives include Joseph Bonelli, UCONN, Sonia Schloemann, UMASS, Heather Faubert, URI, Kyle Bostrom, UMASS and Jean C. King, UCONN Food Policy Consultant.
For learn more about Watson Farm history, visitor hours and upcoming events, click here, email Don and Heather or call (401) 423-0005. You can visit Watson Farm at 455 North Road in Jamestown, RI.
A similar story ran in the July 29, 2013 Eastern and Western editions of Country Folks and the New England Farm Weekly.