Pasture Management on Organic Dairy Farms: Foraging Behavior and Diet Selection

Introduction

It is commonly believed that modern dairy cows have been fed in confinement for so long they possess little if any ability to evaluate the nutritional adequacy of their own diets. However, this view has little merit. It is important to recognize that modern confinement-based feeding strategies have only been in existence about 50 years. Herbivores, which include dairy cows, have been using their senses of sight, smell, touch, taste, and postingestive feedback mechanisms to locate, discriminate, and select diets for millions of years. It is, therefore, not likely that dairy cows have lost this ability in the few short years humans have been feeding them in confinement. In fact, because all foods are a combination of nutrients and toxins (and even nutrients become toxic when eaten in excess), if we were successful in eliminating the cow’s ability to evaluate foods, she would likely not live long enough to reach her first lactation.

What is Behavior?

Behavior is anything an organism does that we can measure. It can be fairly simple—such as a reflexive response to a single stimulus, i.e., things like the knee jerk response, eye blinking, or jumping at the sound of a loud noise—or it can encompass more complex activities, such as foraging and diet selection. Researchers argued for years which complex behaviors were more important—genetic inheritance or learning through environmental experience. However, today we know that behavior of individual animals is a unique combination of both. Modern dairy cows behave the way they do partly because of their evolutionary histories, their unique genetic endowments, and the result of social and individual learning that takes place throughout their lifetime.

Mechanisms Controlling Diet Selection and Foraging Behavior

Animals eat what they eat because of the interactions of two interrelated systems. One system is called the "cognitive" or “voluntary” system. This system uses the senses of sight, smell, touch, and taste along with information learned from mothers, other members of the herd or flock, and past trial and error encounters to determine what to eat or not to eat. Experiences early in life and guided by mothers are extremely important in determining what any animal will chose to eat, even years later. If mom eats it and baby watches, chances are baby will eat what mom eats.

The other system at work is called the "affective" or "involuntary" system. This is a subconscious process that operates without any effort on the part of the animal and links the taste of a food with the food’s postingestive (which means after it is eaten) consequences relative to the requirements of the animal.

Postingestive feedback is essentially an information system that operates within animals at the subconscious level. This system utilizes chemical, osmotic, and mechanical receptors within the gut to evaluate the unique chemical content of each food ingested relative to the particular animal’s nutrient requirements. This information is fed back to the brain where decisions about the food are made. Simplistically, if an animal eats a particular food and, shortly after feels sick, discomfort, or in some other way “not good,” the taste of this food will be paired with the discomfort and the animal will likely shy away from or become averted to consuming this food. On the other hand, if a food is consumed and the animal feels satiated, i.e., no ill effects or feels “good,” the animal will generally pair the flavor of this food with the feeling of satiety and thus develop a preference for the food.

Take Home Message

While the voluntary and involuntary systems function as two separate systems, they are integrated through the senses of sight, smell, taste, and postingestive feedback. Animals use the involuntary system to evaluate the postingestive consequences of consuming a food, and the voluntary system to change their behavior toward the food depending on whether the postingestive feedback was positive or negative. Through this interactive exchange of information, animals constantly monitor the foods they consume and alter their diets in response to their own ever-changing nutritional requirements, changes in the foods they eat, and variations in the foraging environment.

As we continue to look for ways to improve milk production from pastured dairy cows, it is important to recognize that dairy cows are not the machines they are often made out to be. Machines do not care what a food looks, smells, tastes, or feels like. Cows do. When dairy cows express their concerns, it is usually as a decrease in intake and a loss in milk production. Thus, we need to pay better attention to what our cows are telling us about our management and the foods we feed to them. Behavior is a function of its consequences, and the more we accommodate the needs of our cows, rather than dictate what they are going to get, the more contented and productive they will be.

Also in This Series

This article is part of a series discussing pasture management on organic dairy farms. For more information, see the following articles.

• Pasture Management on Organic Dairy Farms: Keys to Grazing Success
• Pasture Management on Organic Dairy Farms: Overview of Types of Grazing Systems and Methods
• Pasture Management on Organic Dairy Farms: Designing the Grazing System
• Pasture Management on Organic Dairy Farms: Managing for Pasture Plant Health
• Pasture Management on Organic Dairy Farms: Transitioning to a Grazing System
• Pasture Management on Organic Dairy Farms: Calculating Paddock Sizes, Dry Matter Intake (DMI), and Acreage Needed
• Pasture Management on Organic Dairy Farms: Pasture Pitfalls
• Pasture Management on Organic Dairy Farms: Assessing Pasture Quality and Productivity

References and Citations

• Emmick, D., K. Hoffman, and R. Declue. 2000. Prescribed grazing and feeding management for lactating dairy cows. USDA Natural Resources Conservation Service, Syracuse, NY.
• Emmick, D. 2012. Managing pasture as a crop: A guide to good grazing. University of Vermont Extension. Available online at: http://blog.uvm.edu/cvcrops/files/2012/10/Managing-Pasture-as-a-Crop.pdf (verified 7 Feb 2013).

Additional Resources

• Behavioral Education for Human, Animal, Vegetation, and Ecosystem Management (BEHAVE) [Online]. Utah State University. Available at: www.behave.net (verified 5 Sept 2012).