It is remarkable that over the years milk yield per cow per day continues to increase in comparison to a slower rate of increase in dry matter intake. Cows are just fascinating; the efficiency of ruminal fermentation and digestibility of the dietary components are key factors in improving the efficiency of feed we use in modern diets.
Today’s primary feeding system is the total mixed ration (TMR); let’s not forget pasture systems and new management techniques for it. Major improvements have occurred in the use of protein, carbohydrates and fats in mix diets.
Although advancements have been made in feeding practices to minimize the risk of metabolic diseases, the dry and close-up period continues to present some of the greatest challenges in animal health on most dairy farms.
In reference to the efficiency of the dairy cow, many studies have provided important information on improving feed efficiency and animal health. Better feed quality, increased overall diet digestibility, alternative feed ingredients, new technologies and improved efficiency of ruminal fermentation is the forward approach to today’s dairy nutrition.
It is safe to add to that statement that dairy nutrition is changing and moving forward faster than ever. If we understand all the nutritional interactions, management tools, new technologies and our own constraints, we can actually make better decisions towards better animal health and performance.
The rumen
The largest of the cow’s four stomachs is the rumen; this is a large fermentation vat that contains more than 500 different microbes including yeast, protozoa and bacteria. We depend largely on those rumen microbes and their health to properly utilize all feed ingredients and nutrients offered in the diet.
The rumen also has papillae or finger-like structures for increased absorption of nutrients. Within the rumen we find three characteristic layers that separate nutrients and gases: a gas layer (top), a fiber mat layer (middle) and a fluid layer (bottom), all influencing ruminal health.
The rumen is not just in charge of digestion of cellulose from plants; it also produces volatile fatty acids (acetic, propionic, butyric) for energy, makes protein from non-protein sources like nitrogen and builds up peptides or amino acid sequences. It also recycles feedstuffs through regurgitation (belching up of long fiber particles) for re-mastication (chewing), re-salivation and recycling. Finally, it produces methane and carbon dioxide as a byproduct from fermentation and digestion.
How much do cows eat? What affects intake?
To answer that question we first need to understand feed intake and the major factors that affect total intake. Bodyweight and milk production affect intake greatly, while other factors like milk components (protein, lactose, fat), heat stress, growth, type and quality of fiber offered, among others, can create large intake variations over time.
On average a cow will eat 2 percent of her bodyweight in terms of dry matter. To that number we need to add about one-third of her daily milk production in terms of dry matter. Milk components can increase feed intake slightly, so we can add a couple of pounds of dry matter for milk solids as a good measurement.
This formula demonstrates what a cow will eat.
1. Cow’s bodyweight × 2% = 1400 lbs × 2% = 28 lbs (Dry matter).
2. Milk production/3 = 90 lbs/3 = 30 lbs (Dry matter).
3. Plus 2 lbs (Dry matter) for milk components, if needed.
Leaving us with the total of 58 to 60 pounds of dry matter.
High fiber, poor management, inadequate feed delivery, not pushing feeds closer to animals throughout the day and heat stress can reduce intake by 30 percent or more.
Why do we use dry matter intake when evaluating diets?
Dry matter is the total moisture-free content of the feedstuff sample. Because moisture dilutes the concentration of nutrients but does not have a major influence on intake (aside from severe deprivation), it is important to always balance and evaluate rations on a dry-matter basis.
What is dairy efficiency and how do we reach true efficiency?
This information will take us now to the concept of milk efficiency. The percentage of dry matter offered that is converted to milk is represented as feed efficiency.
For example, if a cow eats 55 pounds of dry matter per day and gives 88 pounds of milk per day, her efficiency is 1.6; our goal is to reach at least 1.4 efficiency. In other words, for every pound of dry matter consumed, she is producing at least 1.4 lbs of milk.
Forages have been studied more extensively than any other type of feed. Cereal and grains continue to be the primary contributors of starch to diets, very important in meeting the energy needs of dairy cattle. Quality forage, especially early-harvested corn silage, can reduce ration cost and improve cow health.
Feeding byproducts allows for new feedstuffs to be used in diets that would be otherwise thrown away in landfills. Many of these byproducts provide a considerable amount of protein, non-forage fiber, fat and minerals to diets.
Good management of rations and understanding feed ingredients can help overcome problems like:
• Poor forages
• Long days in milk
• Heat stress
• Limited bunk space
• Lack of forage/feed testing
• Inadequate feed delivery
• Sometimes even poor cow comfort
Finally, we have to monitor feed intake and TMR compliance; what is commonly found on most dairy farms is a combination of five different diets – the proper ration created by a trained nutritionist, the ration mixed, the ration offered, the ration consumed and, finally, the ration digested.
As a personal opinion, if we can improve and get as close as possible on the first three “rations,” we will improve efficiency, and we will be really close to achieving the expected results.
Do dry matter determination frequently and lab analysis of your TMR mix at least monthly. If we can increase dry matter intake by 2 lbs, this will equal up to 5 to 6 lbs of milk. This is easily achieved if we push feed closer to cows as many times as possible throughout the day and especially at night.
If we deliver fresh feed at least twice a day once cows are back from the parlor and keep fresh clean water available for all cows, as mentioned in prior editions, we can be more efficient, and we will increase dry matter intake. EL
Fabian Bernal
Dairy Manager Adviser, Alltech Inc.
fbernal@alltech.com
