An integral part of any breeding herd is the development of replacement heifers and bulls. This is especially true in the purebred industry since this is the primary product sold. Development of quality replacement cattle requires a great deal of management and planning. Selection of animals to keep and to cull is step one. Step two requires implementation of an appropriate nutritional program. This can take a number of different forms and will depend on the animal, the manager and the available forage base. Assuming adequate forage is available (pasture, hay, silage) for desired growth of heifers or bulls it becomes necessary to supplement at least some nutrients. If adequate forage is not available, considerable more nutrient and dry matter must be delivered through the feeding program.
Another issue that should be considered is that of feeding management. Many producers, both purebred and commercial, are very limited on time and labor resources to handle feeding or supplementation of their cattle. In most cases, developing bulls and heifers require a more intensive level of management and a greater time commitment than the cow herd alone. For this reason, many producers are choosing to adopt a self-feeding program of some type which does not require a daily handling of feed or supplement for these cattle. If this is the case the choice of the appropriate program becomes a major factor. This article will attempt to address development of replacement breeding animals through the use of self-feeding technologies from the very simple to the more complex. We'll begin by discussing factors that affect intake and intake control. Subsequently we'll look at applying these concepts to self-feeding programs for developing bulls and heifers. Finally, it will provide some fairly simple, effective, self-feeding rations.
Self-feeding and Intake Factors
Since man started feeding animals he has struggled to understand what controls or affects their intake of feed and forages. Cattle are particularly complex creatures when we consider what affects their appetite and drive to consume more or less of the materials that provide for their nutrient intake. Over the years research and practice has revealed a great deal about what drives feed and forage intake in pasture cattle and those in the feedlot.
Producer Motivations
In most situations, what motivates a producer to attempt to control intake in some fashion is the need to provide appropriate levels of nutrients in a cost effective and/or labor saving manner. Additionally, in the case of lactating dairy cows and in most cases, feedlot cattle, the desire is to maximize feed intake, particularly dry matter intake. This is under the assumption that the more feed going in will result in more product produced whether it be milk or meat. As economics has become the predominant force in virtually all cattle operations we sometimes find that maximizing feed intake is not always the most beneficial. Recent research in the feedyard has shown in some situations that feeding at a rate slightly below full feed (referred to as “ad libitum”) can improve gains and feed efficiency and can help control some of the erratic ups and downs we see when we try to keep intake at 100 percent.
In other situations a producer has a desire to control at least a portion of what the animal eats. An example of this is intake of supplements such as protein and energy supplements or mineral supplements while cattle are on pasture. In most cases this requirement is based on a need to insure accurate levels of nutrients delivered, control supplementation costs or the availability of labor. Many times this actually becomes a function of a number of these factors, primarily the need to save labor, thus self-feeding becomes under consideration but there is a need to control intake so cattle don't eat more supplement than they should and either create digestive problems for themselves or end up driving up supplementation costs due to excessive intake. This is especially true of developing breeding animals where the producer wants adequate but not excessive growth, especially in heifers.
Feed Intake Basics
To accurately discuss self-feeding we have to make a number of observations and understand some things:
1) An animal begins to eat when it is hungry.
2) It stops eating because it is satiated (full, satisfied).
3) Meal: The amount of food consumed in a limited period of time. Different species will consume varying numbers of meals per day. This may vary depending on environment management and other issues. For example: Chickens will consume about 31 meals per day, Sheep 14, cows 18, pigs 9.
4) Ration: the amount of food offered within a given time period, usually 24 hours.
5) Voluntary Intake: The total amount eaten during a given period of time, usually 24 hours.
6) Palatability: the overall sensory impression the animal receives from the food.
7) Dry matter intake: The amount of dry matter consumed in a given period of time, usually 24 hours. Dry matter is the amount of dry material (not containing water) in a given ration, forage, etc. In cattle, because of consumption of high moisture materials such as grass or silage the difference between as fed intake and dry matter intake can be substantial.
8) As fed: This refers to feed as normally fed to animals. It may range from 0-100 percent dry matter.
Once a ration is formulated to meet the nutrient requirements of a given animal or group of animals, the next challenge is to assure that the animal consumes an optimal amount of the ration in question. Both under-consumption and over-consumption of feed provide challenges to the producer and the nutritionist. For example, there is a need to decrease intake in overly fat animals (i.e. cattle with condition scores of 8+), increasing voluntary intake in cattle in less than optimal condition (BCS < 4) or in newly calved cows with high milk production capacities and finally, increasing intake in sick and anorexic animals. As noted above, in growing replacement breeding animals, male and female, there is a need to prevent excessive weight gain since this can inhibit the initial breeding process or create bulls that are excessively large
Regardless of the class of cattle (bulls, heifers, cows, etc.), systems that drive feed intake are exceedingly complex. While we won't spend a lot of time on the physiological aspect, a brief description of the system functions include a combination of stretch receptors and chemoreceptors appear to send signals to the brain via autonomic nervous system, metabolites (glucose amino acids, fatty acids), and hormones (insulin, glucagon, cholecystokinin, steroid hormones.
Other factors which effect intake as related to the animal's physiologic state include:
1) Growth: growing animals eat more as a percent of body weight.
2) Obesity: fat deposition actually decreases intake.
3) Estrus: decreases feed intake.
4) Pregnancy: increase in mid-gestation, decrease in late gestation (due to increased size of uterus). drastic decrease at parturition.
5) Lactation: feed intake in lactating ruminants lags behind nutrient requirements.
6) Disease usually decreases feed intake.
Obviously there are a number of dietary factors which affect these groups again:
1) Energy concentration: As energy content of the diet increases, intake should decrease. This tends to be true in ruminants and monogastrics.
2) Rate of passage/digestibility: Ruminants: grinding poor quality hay will increase intake and decrease digestibility because the feed moves through the GI system faster. The increase in intake is greater than the decrease in digestibility so the animal "digests" more nutrients.
3) Single nutrient appetites: Ca, P, Na, Zn, Thiamin appetites have been suggested.
4) Color, shape, odor, and taste can affect dietary intake.
5) Water intake: decreased water intake leads to decreased feed intake and vice versa.
Finally, environmental factors can have a significant effects:
1) Cold environments: feed intake usually increases to maintain body temperature.
2) Hot environments: feed intake usually decreases, however, it takes work to eliminate body heat.
3) Photoperiod: most animals eat more during light periods.
4) Social factors: cattle tend to eat better in groups as compared to alone.
Basic Management Considerations
As you can see there are many factors which affect feed intake both positively and negatively. In many cases intake can be positively affected by simple good management. This includes keeping plenty of fresh, clean water available. Research has shown repeatedly that the availability of water has a direct effect on feed consumption. When water intake is restricted, feed intake also decreases.
Feeds and forages must be kept clean, fresh and free of mold and contaminants. Remember that cattle have a much more acute sense of smell than man does and can detect very small degrees of spoilage. This is especially true in high moisture feeds such as silage or high moisture grain rations. Ration including steam-flaked grains (corn, milo, wheat, etc.) are also susceptible to more rapid spoilage due to higher moisture contents. Intake can be stimulated by feeding more than once per day if labor is available. The feeding activity will trigger the intake response but also this helps insure that feeds are kept fresh.
Keep feeders and troughs clean and free of manure or feed that has been contaminated by manure or urine. Check feeders and troughs first for old feed (it may be necessary to reduce feeding levels somewhat for a day or two to allow cattle to “catch back up.”) and then any contaminated feed or other materials that should not be in the bunk including rocks, pieces of metal, etc. It's pretty amazing what can make its way into a feed trough.
In summer months when temperatures increase, feed intake typically is reduced. This is largely due to the simple fact that cattle do not like to get out and eat in the hot sun or warm temperatures. For this reason it is important to feed early in the day and/or later in the evening.
When maximum intake is the goal, texture of the ration is important. High levels of very small particles (fines) will reduce intake and in many cases will create a sorting problem where cattle will eat the larger particles but leave the very fine material. This can lead to nutritional imbalances since this fine material can include much of the vitamin and mineral. Use of a molasses product can help stick the finer material to the larger particles. Pelleting all or at least some of the feed ingredients, especially those which would be of a finer grade is also useful.
Intake Reduction or Control
On the other side of this coin are methods by which the producer can control intake or hold it at a predetermined level. A great deal of study has been applied to this concept both academically and commercially. The old stand-by in these self-feeding situations has been the inclusion of high levels of salt. Salt/meal mixes have been used for years and normally will include salt with protein meals (i.e. cottonseed meal, soybean meal or some combination) at a ratio of 1:2, 1:3, 1:4, etc. depending on the desired level of intake. Mature cattle can normally tolerate about one pound of salt per day. The positive side of this is that it is relatively inexpensive and easy to do. An example may be seen in Table 1. It also affords some degree of control. The downsides are more numerous: 1) Salt is variable in the level of control it provides to all cattle, in other words, some individuals can tolerate a lot more than others. 2) It is hard on the equipment. Salt is obviously quite corrosive in metal feeders. 3) It requires a lot of room in the formulation. With 20 to 33 percent inclusion rate in some situations, this takes up a lot of room where another ingredient cannot be placed to provide more protein, energy (from starch, fiber, fat), minerals and vitamins, etc. Because of this other technologies have been developed which are more consistent in a smaller package.
