Post by Joann on May 19, 2006 8:33:20 GMT -5
Significance of protein in dairy ration
Dairy rations all provide calories and this is important. However, the protein content of dairy feed is the key factor and it is for this reason that the feed is named according to its percent protein.
When you feed your cow what you are really feeding is the captive population of bacteria which inhabit the rumen. It is upon the activity of these microorganisms that she depends for digestible food. A cow is not a vegetarian. Indeed nothing is, apart from bacteria themselves. These alone are able to dismantle cellulose and with the addition of nitrogen (and other nutrients) restructure it into complete protein, or “animal protein” containing the full spectrum of amino acids necessary to growth and reproduction. Bacteria use the resulting protein to form their own structures. A ruminant relies upon this soup of living and dead microorganisms as her source of complete protein, not on plant protein present in grain.
All protein, complete or otherwise, contains nitrogen. Rumen bacteria obtain their nitrogen by dismantling plant protein consumed by the cow. They do not simply “add on” missing amino acids to plant proteins. They create all new animal protein.
Milk contains complete protein. In producing milk, the cow is passing along complete protein originally synthesized by bacteria. If there is insufficient nitrogen in her grazing, the cow must “milk off her back” which means giving up some of her own muscle protein to provide this constituent in milk, or she must produce less milk. By feeding grain we provide extra nitrogen thus supporting milk production. The carbohydrate calories in grain provide energy for the metabolic work involved.
The amount of nitrogen in feed limits how much protein can be produced in the rumen.
Here is an introductory statement from my book, Keeping a Family Cow:
Amazing cow magic that most people don’t know about
“A young fellow wantin’ a start in life just needs three things: a piece of land, a cow and a wife. And he don’t strictly need that last.” That’s an old saying that used to annoy me. Now that I’m an old lady with a cow but no spouse I am prepared to concede at least the validity of the underlying premise.
An over-arching truth about the cow is that she drives the domestic or small farm economy. By living on a constantly renewing resource, grass, she is able to support not just herself and her calf, but your pig and your chickens (neither of which can live on grass) and still provide milk for the house. The reverse is never true. No pigs or chickens or any other non grazing animals can live on grass or support another animal. And the cow does it on a free resource made of water and sunshine. Through her sovereign ability to convert grass, which otherwise has no value, to milk and meat, which does have value, the cow produces wealth. She thus vaults the domestic or farm economy into a self sustaining mode. Even with the most exacting sweated labor in the orchard or garden, you can’t grow plants that will support reproduction in pigs or chickens or any other non-grazing species including humans; the best you can do is fatten them. This key fact about cows should never be forgotten. (End of quote)
Lots of other amazing things go on in the rumen, especially the fermentation of cellulose to produce acetic, propionic and butyric acid. This is further discussed in Keeping a Family Cow. I thought today a look at the primary source of protein might be of interest.
If as family cow owners we choose to avoid soy, a big nitrogen source, we must look to the protein levels in pasture and hay and consider whether we wish to feed grain. Dairies often use non grain nitrogen supplements such as urea.
Joann