~ guest blog post by Robin Rastani, Ph.D
This is the response that I frequently get from family members and fellow travelers in airports, when they ask about my work. Many people still think that dairy cows consume grass and grass alone. They have that idyllic image of black and white cows out in a green pasture next to a red barn. While some cows can sustain many of their needs on grass alone, they are usually the non-lactating cows (i.e., cows that aren’t producing milk). A lactating dairy cow has a high metabolism, and is very similar to a marathon runner or high performance athlete.
A modern dairy cow consuming grass alone would be equivalent to a marathon runner or Olympic athlete consuming only lettuce with a few sprigs of broccoli. In the old days, everyone had a couple cows, and they only needed to make enough milk for their family. The modern dairy cow now makes about 10 gallons of milk every day. On grass alone, a modern average producing lactating dairy cow would eventually lose tremendous amounts of weight and be unhealthy. As a dairy cow nutritionist, I make sure cows have all the needed nutrients to perform and remain healthy while producing healthy nutritious milk.
A typical dairy cow’s diet consists of around about 50% forage and 50% grains. Most of the forages are plant material that is fed as hay or fermented forage, known as silage. This allows farmers to feed grass, legume and corn-based forages year round. The most common concentrates fed are corn and soybeans, along with by-product feeds like whole cottonseeds, citrus pulp, almond hulls or soy hulls. Cows enjoy variety in their diets, and having a mix of both forage and concentrates allows this. Just like with human nutrition, we must provide the correct amounts and balance of nutrients.
Cows are different from humans in that:
- Cows have a four compartment stomach with a large fermentation vat. This fermentation vat is known as the rumen. In the rumen, bacteria help to digest the feed. This allows cows to obtain nutrition from feedstuffs that contain cellulose and fibrous material that humans and other animals cannot. This is one reason why cows can consume many by-product feeds.
- Cows are limited in the selection of feed that is offered to them. Nutritionists formulate their diet, and it’s offered to them in one mixed up casserole, called a total mixed ration or TMR. However, cows can be picky, and they will try to sort through the feed offered to them. Just like humans, they prefer some feedstuffs to others.
- Cows also have the ability to ruminate. They eat their meals rather quickly, and then while resting they will further digest the feed that was consumed. They regurgitate a ball of feed, known as a cud, and then they chew on that cud. This allows them to break up the feed into smaller particles. It also produces saliva, which helps to keep the material in the rumen from becoming too acidic and cause indigestion.
As a cow nutritionist, I do have some advantages that I’m sure dietitians would appreciate. I can check diets based on records of what’s been consumed, chemically analyze that diet, and modify it accordingly… and my clients (the cows) will usually accept my recommendations. Frankly, cows eat better diets than humans!
There are many similarities and a few key differences between the nutritional demands of a cow and a human, as you can see. Cow nutritionists have a common goal with human dietitians – providing a healthy, balanced diet within a budget for our clients.
If you’re a farmer or agricultural professional, this knowledge may see mundane or commonplace. However, to many of your neighbors and consumers of your products, it is new and intriguing to them. How can you explain the science of food production to them?
Robin R. Rastani, Ph.D., is a Dairy Technical Manager for NOVUS International, Inc. She works with dairy producers and nutritionists to provide optimal nutrition for dairy cows to ensure the cows are healthy and produce a great product for consumers. Feel free to follow her on Twitter (@cownutritionist).