Extension by Tyler Gardner and Scott LakeWritten by Saige
By Tyler Gardner, UW Animal and Range Science major and Scott Lake, UW Livestock Extension Specialist
Many operations manage their heifers and mature cows together over the winter. Reasons vary, including convenience and lack of facilities to separate them into multiple management groups. However, the nutritional demands of growing heifers and that of mature cows are dramatically different.
Heifers that have been weaned in the fall and being kept over as replacements are in a critical growth stage of their life. They are dealing with the stress of foraging and finding feed on their own for the first time. Physiologically, heifers must reach a threshold weight and condition before they will reach puberty and begin to cycle. To reach this threshold prior to breeding, heifers need to be managed to achieve an acceptable level of growth. Mature cows on the other hand have recently been weaned, eliminating the energetic drain of lactation. They are pregnant, but during the first two trimesters of pregnancy the added nutrient demands of the fetus are low. Therefore, their nutritional demands are at their lowest point of the year and they do not need the quality of nutrients that the growing heifer and recently weaned two-year-olds require.
For example, the growing heifer (between 550 and 700 pounds) needs approximately a diet containing 1.3 to 1.5 pounds per day of protein (10 percent), 9.5 to 10.5 pounds per day of TDN (65 to 70 percent), and consume between 13.5 to 15.5 pounds per day of dry matter intake. A mature dry cow (1,200 pounds) in the middle third of gestation requires about 21 pounds of total dry matter intake, with about 1.5 pounds per day (seven percent) of that in the form of protein and about 10 pounds per day of TDN (50 percent).
At first glance, the total pounds of nutrients required for heifers and cows appear similar, which is true. However, it is important to notice the total dry matter intake that a heifer can consume is much less than that of a cow, so the heifer diet needs to be much more energetically dense, or a much higher quality feed. It’s also important to remember that, as a cow reaches the third trimester of pregnancy, her nutritional demands increase. Other factors such as extreme cold or wet weather will also increase nutrient requirements for both heifers and cows.
In addition to differences in quality of feed offered to heifers or cows, the heifer has a harder time competing with cows for food. Often times when heifers and cows are managed together, the cows get more than they need, while they push aside the heifers, who are getting short changed on the grocery side.
Another management tip is to try to sort heifers and cows into similar size/condition types. For many operations, this may not be practical due to facility restraints. However, there is research that demonstrates feeding larger heifers together and smaller heifers together will result in a decrease in the total amount of feed fed during a period, while increasing their performance (weight gain and increased conception rate). The reasoning is that cattle are usually fed to a pen average in terms of requirements. The smaller the variation in a group of cattle, the more precisely the requirements can be met.
This type of strategy helps eliminate the top end of the cattle from getting too heavy, while allowing the smaller cattle more of an opportunity to grow. The same approach can be taken for cows. There are always the lower ends of cattle (in terms of condition, not productivity) due to a variety of reasons (heavy milk, late calving, etc.) that need to add some condition during the winter. If these cows are separated from those that are in better condition, they can be fed a higher quality feed to increase condition without wasting unnecessary feed to the remaining herd.
Although extra pastures or pens to feed animals are often a limiting factor, separating heifers and cows can result in increased performance and feed savings. Similarly, sorting larger and smaller heifers and thinner cows can increase performance and feed savings, as well.