Supplementing Cattle – What to Consider
Larry R. Corah, Professor-Emeritus
Kansas State University

Trying to maintain productivity while keeping costs down is an ongoing challenge for the cattle producer.  Since supplemental feed is usually the purchased part of the feed bill, knowing how and when to supplement is very important.
In deciding what and how much to supplement existing feed resources, consideration must be given to key factors.  Unfortunately, tradition is often a key part of the decision … but should it be … is it time to change … are your cows today more productive than 10 years ago … does new scientific data exist that might cheapen the feed bill?

Factors to Consider

1.	Nutritional Needs of the Cow
The first consideration in building a nutrition program is understanding the nutritional requirements of the cow.  These requirements vary depending on whether the cow is lactating or dry, the size of the cow, the level of milk production, and the state of production of the cow.
Table 1 illustrates a cow herd nutrition calendar that starts with calving and ends with the production of the next calf 365 days later.  Although this nutritional calendar appears to be based on an individual cow, it fits an operation for the whole cow herd.  Period 1 begins on the date when the first calf is born.  To ensure that a large percentage of the cows are in the same period and, therefore, can be fed similarly, a short breeding season and subsequent calving season must be utilized.

Table 1.  The 365-Day Beef Cow Year by Periods

Period 1	Period 2	Period 3	Period 4	
80 days
(post-calving)	125 days
(pregnant and lactating)	110 days
(mid-gestation)	50 days
(pre-calving)	

Period 1:
To maintain a yearly calving interval, the cow has approximately 80 days from the time of parturition until rebreeding.  In the case where it is desirable to move late calving cows to an earlier calving date, the cow may have less than 50 days.  Because mature cows typically take from 40 to 80 days to recycle and first calf heifers take from 60 to 100 days, proper nutrition during this period is important.  Thus, Period 1 becomes the most critical period, because the cow is maintaining a peak level of lactation, and the onset of cyclicity and rebreeding must occur.  Nutrition during this period will have a major influence on conception rates.

Period 2:
Once the cow is pregnant, the major nutritional needs are to maintain lactation.  Also, in most production systems, it is advantageous that the cow gain weight during this period, putting on adequate “flesh” for harsh environmental conditions that may wait.  This is particularly true for spring calving cows in northern climates.

Period 3:
This period has the lowest nutritional requirements.  In some environments, this is an ideal time to utilize crop residues, lower quality feeds, or the poorest roughage that is available.  However, it is important that the cow not lose excessive weight during this period unless she enters it in fairly good “body flesh.”  If the cow enters in moderate to slightly below average condition, she should maintain weight and possibly even gain some weight.

Period 4:
This is the period often overlooked in many cattle operations.  It should be kept in mind that during this short period (approximately 50 days), approximately 65 to 80 percent of the fetal growth will occur.  In cases where typical birth weights are 80 to 85 pounds, this means that from 50 to 60 pounds of fetal growth may occur during this time.  Research has shown clearly that improper nutrition during this period will influence calf birth weight, calf vigor, and calf survival.  There is no advantage to reducing the cow’s plane of nutrition to reduce calf size as a means of alleviating calving difficulty.  Poor nutrition during this period will cause a longer postpartum interval, reduce level of milk production, and reduce calf weaning weights.

2.	Nutritional Value of the Forage or Range that is the Primary Feed Source
Supplemental feed is purchased to compliment existing forage being fed or grass being grazed.  Thus, some knowledge of the nutritional value of the roughage is critical to determining what and how much supplement is needed.
Is the roughage short of protein?  If so, what type of protein could or should be used and at what level?  Is energy needed and how can that be supplied most effectively?
Part of the supplementing is knowing when the specific nutrients will have their greatest value.  We also cannot overlook nutrients needed in smaller amounts like phosphorous, trace elements, and vitamins.

3.	Age of Cattle
A good management practice that is used by many cattle producers is to sort cattle by age.  The nutritional requirements are different for young heifers being developed than for mature cows.  When animals are in a growth state, it is important to have adequate energy and protein present in the ration to maintain growth.  In contrast, with mature cows, particularly those that enter the fall in “good” condition, some weight loss can occur during the winter with no adverse effect on productivity.
One of the keys to having a sound reproductive program with cows is the nutritional management of the replacement heifers.  These heifers need to achieve approximately 65 percent of their mature weight by the time they are bred as yearlings.

4.	Cow Size and Milk Production
To develop a more productive cow, many cow/calf producers have emphasized growth and milk production in their selection process.

This has tended to increase cow size and level of milk production.  A 5-pound increase in milk production per cow per day increased the TDN (net energy) requirements by 10 percent and the crude protein requirement by 13-15 percent.
Changes in cow size do not have the same impact on energy requirements that significant changes in milk production do.  Each change of 100 lbs. in cow size changes the maintenance net energy requirements by 6-8 percent.
A common question asked by today’s beef producer is:  “Can we maintain reproductive efficiency in higher producing cows?”  Actually, the question is:  “Will a commercial cattle producer adjust his management program and nutritional philosophies to accommodate the added nutrient demands of a higher producing cow?”  Ample research indicates that normal reproductive performance can be maintained in more productive cows if the additional nutrient needs are met.  The real dilemma facing the commercial cow/calf producer is that the nutritional needs will be increased and, thus, some change in managerial philosophy must occur to accommodate the more productive cow.  In making the decision to have a more productive cow, the producer needs to consider the resources available.  If there is an ample supply of high quality feed, a heavier, larger milking cow can often be maintained.  If the feed supply is limited or if environmental conditions such as drought, which reduces reproductive rates, frequently occur, then maintaining a slightly smaller, somewhat lower producing cow may be the best choice.

5.	Effect of Environmental Stress
In monitoring the nutritional needs of cattle, keeping an eye on the weather is important.  This is true not only during the critical winter months when severe cold is a problem, but also when wet, damp spring weather affects the nutritional requirements of cattle.
For cows with a winter hair coat, the critical winter temperature is around 30ºF.  When the temperature drops below the critical level (this is not the actual temperature, but the wind chill index), there is an increase in the energy requirement.  For each 1ºF drop in critical temperature, there is approximately a one percent increase in the TDN or net energy required.
Another important item that many cow/calf producers often overlook is the effect of weather in the spring on the nutrient requirements of cows.  Cows that have lost weight and are in thin condition are very susceptible to the environmental effects of spring weather.  When cattle, even with a winter hair coat, are wet, the critical temperature increases to around 50ºF.  Thus, during wet spring weather when the temperature is around 30-35ºF, weight loss can occur.  In most cases, these cows are immediately pre- or post-calving and weight loss at this time can have a very detrimental effect not only on milk production and calf performance, but also on how soon the cow will cycle and rebreed.

6.	Specific Area Deficiencies
Items that any practitioner or nutritionist needs to consider in formulating cow diets are specific area deficiencies.
Considerable variation can occur in the quality and composition of forage in a particular region.  It is virtually impossible to formulate diets without having some appreciation of the forage protein, energy, and mineral content and how this changes during the season.  Unfortunately, it is impossible to develop tables that can be used nationwide and, thus, it is imperative that individuals develop nutritional guidelines for their specific areas.