Feeding dairy cattle isn’t as simple as following your nutritionist’s formula. That formula only works if the feed ingredients contain the nutrients expected, the ration is mixed properly, and the cows are eating everything, as prescribed.
All along the way from harvest to rumen, many variables are introduced. That’s why Cornell Cooperative Extension Dairy Specialists and Cornell PRO-DAIRY teamed up to present a two-day Feeder School, held at various locations across the state this fall.
In Central New York, the first session was held at Walnut Ridge Dairy, LLC, in Lansing. Walnut Ridge Dairy has 1,500 cows in the milking herd. The herd produces over 90 lbs. of milk per cow, with 3.6 percent milk fat and just over 3.0 percent protein. Their somatic cell count averages about 180,000. Milking is done four times per day, in their relatively new rotary parlor.
Feeders from almost a dozen dairy farms attended the class. With herds ranging in size from 150 to 4,000 cows, the group’s diversity was representative of the range in size of commercial dairy farms in the state.
Feeders may not be privy to a lot of the information that could assist them in better understanding the impact their job has on herd health and productivity, Betsy Hicks, Dairy Specialist for South Central New York, said. While a dairy has many moving parts, communication between them — owner, herdsperson, field crop crew, nutritionist — is essential for optimal cow nutrition and productivity.
Feeders may not see the forage reports, and may not be familiar with rumen digestion, cow energy needs, the importance of dry matter, and the basics of cow nutrition. Connecting the dots on these topics, and educating feeders on the impact their jobs have on the dairy’s bottom line, is the purpose of these classes.
To insure quality, feed ingredients must be handled with care all throughout the supply chain. Hicks described the “art and science” of feeding cows, with the bunk face being the canvas upon which feeders work. But before feed ingredients are pulled from the bunk, they first have to be harvested and stored properly. Afterwards, they must be mixed, feed, and consumed correctly to make the science work.
Silage and nutrition
“Harvest (it) at the right time. Put it up the right way,” Hicks said. “You’ve got one shot to put feed up.”
Dry matter (DM) is the light-weight, concentrated form of feed ingredients after water is removed. DM is used when formulating cow diets, and provides the nutrients the cow needs. As-fed weights include the feed and its moisture. To calculate DM, feed samples must be dried. Feeders can calculate the dry matter percentage in forage samples, using simple mathematical equations. Forage samples are first properly dried using a Koster meter, a microwave or vortex dryer.
In the bunk, DM should be recalculated whenever any type of forage change occurs. Optimally, DM would be calculated on a daily basis, for best nutrition. If the bunk gets wet, when changing to a new bunk, or moving to a new cutting in the bunk are all times when the DM content should be rechecked.
Improperly packed bunker silos can damage nutrient availability. If feed is too wet when packed, or if rain gets into the bunk pile, there can be pockets of moisture, impacting proper fermentation. The excess moisture prevents the pH from getting low enough for proper fermentation to occur. Wet silage also causes extra ammonia to form in the rumen. If there aren’t enough sugars or starch to capture this nutrient, then it is wasted, escaping the cow as urea. Proteins become damaged if the temperature in ensiled forages reaches more than 120 degrees. The cows can’t digest the damaged protein, and nutrition will be compromised.
If the pH of the bunk is above 4.5, undesirable Clostridial, or secondary, fermentation can occur. The clostridia bacteria grow in anaerobic conditions, and the pH level needed for this growth to occur varies to some degree depending on the DM content of the feed.
Cows require carbohydrates and protein from their feed, along with minerals, fats and vitamins. Protein is broken down into rumen bypass proteins — the amino acids — and rumen degradeable proteins, which feed the microbes essential to cow digestion. Carbohydrates are broken down into starch, sugar, and fiber. Fiber serves as the energy source for the cow.
A cow requires energy “just to be a cow,” Hicks said. About 20 percent of their energy intake is used to maintain their status, and another 20-25 percent is for growing, reproducing and making milk. Much of the energy is lost to bodily processes, and passes out of the cow in manure, urine, heat and gases.
If crops are harvested too mature, the lignin content increases, making the cell wall too hard to digest. Inside the cell wall, the nutrients needed by the cow can’t be accessed as readily, meaning the cow isn’t getting the energy or nutrients it should from that feed.
The cow rumen is a 40-50 gallon fermentation chamber, where microbes — bacteria, protozoa and fungi — transform crude proteins, and they themselves serve as a protein source later in the digestive tract. The rumen is also where fiber is broken down by microbes, given enough time.
“It takes time for rumen passage,” Jerry Bertoldo, Dairy Specialist with the Northwest New York Ag Team, said. “If we don’t feed the cows right, the rumen isn’t happy.”
The rumen is in constant movement. It has a pH of about 6.0 to 6.6, and remains at a constant temperature. It is an anaerobic environment, and depends upon the right feed mixture to function effectively. The microbes require a consistent diet, and they like to work slowly.
“The level of carbohydrates versus nitrogen and the rate they go in” matters to rumen digestion, Bertoldo said. “Cows and their bugs really like to be bored. Same thing all of the time.”
The rumen mat is crucial to proper and efficient rumen digestion. As cows chew their cud, they are digesting large feed particles until they are small enough to fall through the rumen mat, and are ready to be moved out of the rumen.
Chewing cud increase the amount of saliva produced, which acts as a buffering agent against acidity. The rumen mat requires effective, large particles of fiber to form. Feed ingredients such as distiller grains, corn meal or cracked corn are too small, and migrate to the bottom of the rumen. A good rumen mat will help these ingredients to be more effectively digested.
Knowing what various feed ingredients provide in the diet can assist feeders in better understanding the role of proper ration determination and proper feed mixing, the importance of feed — and water — availability, and the correlation between cow health and proper.
“I think primary take home lesson for the feeders would be to get them to understand how important their role on the dairy is and how everything they do can impact so many other areas on the dairy,” Hicks said of the Feeder School program.