Producers understand that in order to have a successful cow/calf operation the first thing that must happen is to get the cow bred. Number two, obviously, is for that bred cow to deliver a live calf with as few complications as possible. The third step in this process is for that cow to provide adequate milk and nutrition for that calf to grow and develop to weaning. But providing milk is only a simple component in understanding calf nutrition. New and growing calves are complex creatures and go through many changes in a very short period of time. This article will focus on providing an understanding of calf nutrition and providing some insights and guidelines to insure these young animals get off to the best start possible.
From the Beginning…
Much of what we know about the nutrition needs of very young cattle comes from the dairy industry. The main reason for this is due to the fact that the calves stay on the cow for such a short period of time; two to three days at the most in the majority of situations.
At birth and during the first few weeks of life, the rumen, reticulum, and omasum are undeveloped. You will recall that the rumen, or first stomach in a cow is very large and the primary compartment in the digestive system of bovines. At birth this is not the case. In contrast to the mature cow, the abomasums, or last compartment (the true stomach) is the largest compartment of the of the 4-compartment system in the calf. At this stage of life, the rumen is non-functional and many forages and feeds commonly and easily digested by the adult cannot be used by the calf. During nursing or feeding from a bucket, milk bypasses the rumen through a structure known as the esophageal groove and passes directly into the abomasum. Reflex muscular action closes the groove to form a tube-like structure which prevents milk from entering the rumen. In some cases, however, when milk is consumed very rapidly, some may overflow into the rumen.
As long as the calf remains on milk, the rumen remains undeveloped. “Inoculation” of the calf's rumen begins at birth as the cow licks the calf; especially around it's muzzle and introduces many of the bacterial species which colonize the young animal's rumen. It is further inoculated when calves begin consuming grain and forage. Through these activities a microbial population becomes established in the rumen and reticulum. End products of the microbial fermentation process (largely the various organic acids) are responsible for the development of the rumen. This occurs as early as three weeks of age with most management programs. If grain feeding with or without forage is started during the first few weeks of life, such as in dairy calves, the rumen will become larger and more heavily developed, and will begin functioning like the adult's when the calf is about three months of age.
The calf enters the world without disease resistance. In essence it is a clean slate. Up to six months of immunity is provided by “first-milk” colostrum, if it is consumed right away. The new calf's intestinal tract is highly efficient at absorbing immunoglobulins (antibodies) within the first four hours, but this ability declines rapidly. Understand that immunoglobulins are large protein molecules and as the calf ages, it's ability to absorb these large proteins decreases to the point where more mature animals are, i.e. able to absorb only individual amino acids or limited groups of two or possibly three amino acids (dipeptides or tripeptides).
It's best if the calf can consume two to four quarts of first-milk colostrum within the first two hours even if it has to be force fed since this will greatly stimulate it's immune response. In addition to delivering antibodies, colostrum gives the calf a massive charge of nutrition, which enhances the chance of survival. Note Table 1 below which compares colostrum with whole milk. Ideally, every calf should receive colostrum for the first three days of life.
Feeding the Cow Feeds the Calf
While the intake of the colostrum and then whole milk as produced from the cow are the foundation of the calf's nutrition system, the nutrient availability is largely related to the nutrient available to the cow. This is true even before the calf is born. Access to adequate levels of dry matter, protein and energy are critical to maintenance of proper body condition and delivery of nutrients to the unborn calf and then after it is delivered. While there is some opportunity to modify milk components (i.e. protein and fat levels in the milk itself, fat being a major energy source for growing calves) a primary objective is providing appropriate levels of nutrients to the cow to promote production of optimal volumes of milk.
One thing that the producer has to remember – we've discussed this before – that nutrients consumed by the cow are prioritized. In other words, as nutrients are consumed they are provided to the animal's various systems based on their importance to survival of the animal. This primarily becomes an issue when adequate levels of given nutrients, be they protein, energy, minerals, etc. are not adequate to meet all the animal's needs. It is well known that if one or more of the various nutrients are in short supply, the first system from which allocation is pulled is reproduction. The second is milk production. This simply means that a cow that is being shorted nutrients will not produce the level of milk that she might otherwise be capable of since nutrients are being directed to the systems that are directly involved in the cow's survival and milk production is not one of these.
Thus, in order to maximize the calf's growth, the cow must produce as much milk as possible, subsequently her nutrient needs must be met during this stage of the calf's life, i.e. from birth through weaning. Tables 2-4 below illustrate some of the nutrient levels required for cows of various body sizes to produce average levels of milk. These tables were adapted from the 1996 National Research Council's
Nutrient Requirements for Beef Cattle.
As you can see there is a distinct difference between the requirements for cows of different body sizes. There are also differences based on milking level (i.e. heavy milkers vs. average milkers, vs. light milkers) as well as age (heifers vs. cows) and breed (Angus vs. Simmental, vs. Brangus, etc.) but that's a topic for a different series of articles. The main point here is that in order for the new and growing calves to develop normally or optimally they must be provided with adequate nutrients and at least for the first few months the majority of this is delivered through milk.
In many cases, in order to reach a calf's genetic potential it may be necessary to provide a supplemental feed of some type via a creep feeder. Some research has shown this can be achieved by creep “grazing,” especially when the calf is older and has started grazing on it's own to a certain degree. This is especially useful in fall born calves that can be creeped on winter pastures that are lush and succulent (wheat, oats, ryegrass, etc.). In other circumstances to achieve this it must be done by provision of a supplemental feed of some type. While this does add expense, as long as the level of gain and the added value (increased lbs. times market price) produced exceeds the cost it may be a good investment. This can result in heavier calves at weaning, calves which wean in a less stressful position since they are accustomed to eating feed and in the situation with heifers, may ultimately result in an earlier breeding and subsequent calving. The producer has to carefully evaluate the cost/benefit ratio in order to make this decision.
Producing a calf crop each year is more that just calving out cows and waiting for weaning time. To produce efficient, profitable calves, the producer has to understand where the nutrients come from and how they may affect growth and performance. Then he can take the necessary steps to enhance growth and performance.
Dr. Steve Blezinger is a nutritional and management consultant with an office in Sulphur Springs Texas. He can be reached at Route 4 Box 89 Sulphur Springs, TX 75482, by phone at (903) 885-7992 or by e-mail at firstname.lastname@example.org.