Big cows, small cows, and feed efficiency
Published in Dairy Star June 28, 2014
The U.S. dairy farmers in cooperation with many different partners in the dairy industry have made great improvements in milk production and overall efficiency of producing milk. Efficiency is defined as output/input or in this case, pounds of milk per pound of dry matter intake. Feed efficiency is one aspect of overall improvement in the efficiency of production. In the last 50 years, dairy feed efficiency in the U.S. has doubled. Yet we have not directly selected for a trait defined as feed efficiency.
A dry cow eats about 25 pounds of dry matter per day but produces no milk. Her efficiency for milk production is 0. If a cow milks 50 pounds per day and eats 50 pounds of dry matter per day, her efficiency is 1.0. A high producing cow may eat 60 pounds of dry matter but produce 120 pounds of milk per day for an efficiency of 2.0. A common herd efficiency value is typically around 1.5 to 1.7. So, what does this number mean? How do you use this information?
At the recent Four-State Dairy Nutrition and Management Conference in Dubuque, Iowa, Dr. Mike VandeHaar from Michigan State University reported on a major project on feed efficiency funded by the USDA that involves faculty from several land grant universities. They have studied many of the factors of feed efficiency and ways to improve it. One major component of feed efficiency is how much of the consumed feed is used just to maintain the cow and how much ultimately goes to producing milk, growth or gestation. The more milk or pounds of milk fat and protein that is produced, the more efficient the cow is because she is spreading the maintenance over more pounds. This is called the dilution of maintenance. Once the cow has eaten enough to maintain herself, every additional mouthful of feed can go to milk production. This is one reason we emphasize pushing up feed, having fresh feed and other feeding management factors.
What are some other factors that improve feed efficiency? As mentioned above, all aspects of feeding management can improve feed efficiency. Forage quality and the improvements we have made in cutting/harvesting management may have had the biggest impact. We know overly mature forage will be higher in neutral detergent fiber (NDF), which can limit intake, and will be lower in NDF digestibility, which will keep the rumen full longer. We continue to develop corn hybrids for silage which are better in forage quality and grain digestibility as well, corn grain is processed to increase starch digestibility, and by-products and fat are added to the ration. All of these factors have increased the energy density of diets and increased intakes to well beyond maintenance. Some cows are now consuming energy at 4 times maintenance with herd averages over 30,000 pounds per cow per year. We also have developed more sophisticated ration balancing software.
Another critical component to feed efficiency is days in milk for the milking herd. Getting cows pregnant is very critical to maintaining efficiency of the lactating herd. We know that cows early in lactation produce more milk than cows later in lactation. A herd that is under 150 days in milk is much more efficient than one at 225 days in milk. Keeping the pregnancy rate over 20%, with a goal of 25%, not only keeps down days in milk but allows for more culling of unproductive cows. We also can avoid non-productive cow days from long dry periods and heifers freshening over 23 to 24 months of age.
Can we breed for improved feed efficiency? Yes, but it is very complicated to select for this trait. However, without actually selecting for feed efficiency, we have made tremendous improvements in the last 50 years. Most of that time, we were selecting for milk production. If we look at breeding more profitable cows, the Net Merit and TPI indexes give us a balanced approach for picking sires. In the future, feed efficiency may become part of the index.
Mature cow size is a trait that is often discussed. Are smaller cows more efficient than big cows? Again, it depends on milk production and feed intake. Small cows can be very efficient, but so can larger cows. However, a higher milk production, or more specifically higher production of pounds of components, is needed from the larger cow that eats more. It may be more important to select a size of cow that fits your system and facilities. Then select for cows that are more profitable.
Will genomics help determine bulls and cows that are more feed efficient? It would seem logical that there are genes that can influence traits such as dry matter intake. But we already can identify traits for milk production, body capacity, daughter pregnancy rate, longer productive life and many others. We will continue to breed for higher producing cows that last longer and are more profitable. By doing so, we will continue to improve feed efficiency as well.