CHAPTER 6
Feeds & Feeding
Humankind has historically fostered and relied upon livestock grazing for a substantial portion of its livelihood because it is the only process capable of converting the energy in grassland vegetation into an energy source directly consumable by humans. Biochemical constraints determine that herbivores function as “energy brokers” between solar energy captured by plants in the photosynthetic process and its subsequent use by humans. The inability of humans to directly derive caloric value from the 19 billion metric tons of vegetation produced annually in tropical and temperate grasslands and savannas provides the ultimate justification for evaluating grazing as an ecological process.
— R. K. Heitschmidt and J. W. Stuth (ed.),
Grazing Management: An Ecological Perspective
THE SINGLE MOST IMPORTANT FUNCTION a farmer or rancher serves in the lives of his or her animals is providing for their nutritional needs. As Dr. Bruce Haynes, DVM, says in Keeping Livestock Healthy, “It goes without saying that a well-fed animal is more likely to be a healthy animal.”
Water
Water is the major constituent that makes up all living organisms. At birth, water may account for 75 percent of the total body weight of a calf, but at two years a finished steer’s body will only be 45 percent water by weight. Water provides structure to cells, it allows nutrients to be transported and broken down, it flushes toxins from the body, and it moderates the body’s temperature. An animal could live without any food for a couple of weeks, but keep it from an adequate supply of water on a very hot day and it can succumb to heat stroke after only a few hours. Even during the winter, three waterless days can result in an animal’s death. Water must be available every day!
Keeping Water Clean
One of the biggest challenges in the water department is keeping it clean. No animal wants to drink water that has been contaminated by manure or urine; yet if I had a dollar for every time we had to drain and clean a tank with manure or urine in it, I’d be a heck of a lot wealthier! Even if your water system is automatic, check your tank every day: The water should be clean, and there should be plenty of it. If you’re going away, have a neighbor — preferably one who also keeps livestock — check the water.
The best tanks for small critters such as sheep or goats, or for just a couple of bigger critters, are probably the newer rubber pans. We use one that’s about 25 gallons (95 L) in capacity. They can be set up to run with an automatic valve, so you don’t have to keep refilling them, but if they become fouled they’re quick and easy to dump and rinse. These tanks are great in freezing climates, because they can just be tipped upside down and stepped on — the ice simply pops out, even if the pan was frozen solid.
If you have a large herd of bigger animals, you’ll need a larger stock tank, but again get the smallest one you can get by with so it will be easy to drain and clean. There are a number of brands out now that are made of rubber or hard plastic, so they won’t rust out on you. If you do live in a severe freezing climate, the hard plastic units will break if they freeze solid, though some are designed to work with an external heater. Try to steer clear of the style of electric stock-tank heaters that are suspended in the water; these are expensive to run, and if an animal chews through the cord it creates a major hazard for both animals and people. Consider these alternatives for freezing climates:
1. Run a small trickle of water continuously — though this tends to make a major ice monster by the end of the winter.
2. Fill water tanks once a day during the coldest part of winter with just the amount of water that meets the animals’ needs. The goal is for them to have all the water they need but to drink the tank almost dry each day. We successfully used this technique, filling the tank first thing every morning; our animals learned to come up and get a couple of good, long drinks as the tank was filling. With our size tank and our stock, we learned to leave the tank about half full after everybody got their first drink, so by late afternoon the tank was empty again.
3. Splurge on one of the newer insulated water-tank systems. Even in central Minnesota, where temperatures fall below 30°F ( 34°C) for weeks at a time (our record was 49°F, or 45°C), on the thermometer), these units have a good reputation.
Galvanized tanks are readily available and come in a wide variety of sizes and styles, but they do tend to rust out. In Minnesota, our water was quite corrosive; galvanized tanks rusted after five years.
Pigs create their own problems with almost any water system. They love nothing more than to dump their water or roll in it; they get their water dirty almost as quickly as you clean it. We used one of the same rubber pans that I mentioned earlier for our pigs, but we set it inside a large steel container so that they couldn’t tip it quite as easily. Some farmers set up water fountains for their pigs; others pour a concrete pad and tank (Figure 6.1). Poured-concrete tanks can work for any type of livestock, but if you do pour a tank and pad, make sure to roughen up the pad surface so it won’t be slippery for hooved animals. Provide a way to drain the tank for cleaning — or you may be manning the bucket brigade more often than you’d like.
Composition of Feeds
Most livestock species are herbivores, so plants are their exclusive source of nutrition under natural conditions (though some commercial feed supplements may contain animal by-products, such as blood meal, dried whey, or meat and bonemeal). Pigs and poultry are an exception to the rule — like humans, they’re omnivores, and at least a portion of their natural diet is composed of animal matter (which includes insects!).
Whether the source is a plant or an animal, there are certain basic properties that all feedstuffs share. They are made up of three major components: water, organic matter, and mineral matter or ash. If you took a sample of feed and ran it through a laboratory test to differentiate the three, you would weigh the initial sample, then bake it at 120 to 150°F (49 to 66°C). This first step would drive off the water, and the difference between the initial weight and the dried weight would give you the weight of the water. The amount of sample remaining would be the dry matter, and it is composed of both organic matter and mineral matter. The next step would be to burn this remaining sample at a very high temperature, which destroys the organic matter. When the sample is weighed a final time, the remaining amount is equal to the mineral matter, or ash.
Figure 6.1. Concrete stock tanks can be used where a permanent water installation is desirable.
(Redrawn from Guy Lockwood, Raising and Caring for Animals: A Handbook of Animal Husbandry and Veterinary Care. New York: Charles Scribner & Sons, 1977, p. 37.)
TERMINOLOGY
Balanced ration. A ration that provides all the nutrients, in the proper proportions (including energy, fiber, protein, vitamins, and minerals), for the animal’s needs based on its age and its level of work.
Concentrate. The grain or grains being fed as part of the ration.
Dry matter. The mass of the ration or feedstuff if the water is “baked off.” For example, a sample of mixed meadow hay might contain 85 percent dry matter, so your 60 pound (27.2 kg) bale of hay would actually weigh 51 pounds (23.1 kg) on a dry-matter basis (0.85 x 60 pounds).
Energy. The part of the ration that is made up of sugars, fats and fatty acids, and starches used by the body for muscle and nerve activity, growth, fattening, and milk secretion.
Feedstuff. Any food intended for livestock consumption.
Fiber. The part of the ration that comes from cellulose and hemicellulose in plant matter; it is broken down in ruminants and horses to create additional sugars and fatty acids.
Forage or roughage. The hay or pasture portion of the ration.
Protein. The portion of the ration that contains amino acids, which are required by the body for cell formation, development, and maintenance, especially for muscle and blood cells.
Ration. The combination of foods in a specific diet, for a specific animal or class of animals, at any given time. Includes everythi
ng the animal is receiving.
Supplements. The vitamins, minerals, or protein being added to the ration.
Total digestible nutrients (TDN). TDN is the portion of the ration that the animal actually is able to take advantage of. Feed reports, feed tags, and feed charts report the TDN of the feedstuff. If the TDN on the previous sample of hay was tested as 60 percent on a dry-matter basis, the bale would contain 30.6 pounds (13.9 kg) of digestible nutrients (0.6 x 51 pounds).
The organic matter can be grouped into four parts: the carbohydrates; the fats and fatty substances; the proteins or nitrogenous compounds; and the vitamins and minerals. All organic matter is principally made up of carbon, hydrogen, and oxygen, though other elements may be present (Figure 6.2).
Carbohydrates
Carbohydrates form about three-fourths of the dry matter in plants, so they are the most significant component of feed. The carbohydrate group can be broken down into sugars, starches, and fiber; the proportion of each varies according to the plant’s age, environmental factors, and the type of plant.
The carbohydrates contain atoms of carbon (C) attached to molecules of water (H2O). For example, a simple sugar molecule would contain six carbon atoms and six molecules of water (C6H12O6). Starches are composed of groups of sugar molecules strung together. All animals easily digest both sugars and starches, so they provide a relatively high feed value. On the other hand, the fiber component is made up primarily of lignins and cellulose. The lignins are completely indigestible, and the cellulose, which accounts for about 50 percent of the organic carbon on earth, requires bacterial fermentation to break it down into usable sugars and starches. All animals are able to ferment a small amount of cellulose in their intestines, but only the ruminants, such as cattle and sheep, are able to convert the bulk of the cellulose in their diet to usable sugars and starches. A more detailed discussion on digestion by different species follows this section.
Fats and Fatty Substances
Like carbohydrates, fats and fatty substances are made up of carbon (C), hydrogen (H), and oxygen (O); however, the proportions of carbon and hydrogen are much greater than that of oxygen in a fat. For example, a common fat in plants is olein; its chemical formula is C57H104O6, meaning that there are 57 carbon atoms, 104 hydrogen atoms, and 6 oxygen atoms in each molecule of olein. Despite our current fear of fat, it is an essential nutrient for all animals (especially young animals), including humans. Fat provides more than twice the energy than a carbohydrate provides, and it helps an animal maintain its body condition and temperature.
Proteins
Proteins are essential for the development of all cell walls. They’re also critical in forming muscles, internal organs, blood cells, hair, horns, and bones. In most animals, protein accounts for 15 to 20 percent of the animal’s weight (Table 6.1).
Unlike simple sugars, which may contain as few as 20 atoms, each molecule of protein is made up of thousands of atoms. In nature, as in construction, it’s often easier to build a complex structure by using substructures, such as building blocks or prefabricated roof trusses. In the case of proteins, the building blocks nature has developed to simplify construction are called amino acids. There are many thousands of amino acids, but only about twenty are critical for protein construction. Words are built by varying the combinations of the twenty-six letters of the alphabet, and similarly, proteins are built by varying the combinations of these twenty amino acids. As with fiber, the ruminants have a real edge when it comes to using all the amino acids and proteins that are in their diets.
Figure 6.2. (A.) Chlorophyll-containing nutrient-rich cells are sandwiched between fibrous surface cells. (B.) The proportion of cell wall to cytoplasm is higher in older plants than in younger plants; in stem tissue than in leaf tissue; and in warm-season grasses than in cool-season grasses.
Table 6.1
COMPOSITION OF THE BODIES OF FARM ANIMALS
Vitamins
Vitamins are organic in nature (they burn off in the laboratory sample with other organic matter), but unlike carbohydrates, fats, and proteins, there is no rhyme or reason to their structure: Each one is unique from the others in its chemical formulation.
Vitamins are required in very small quantities, but deficiencies of vitamins in the diet can result in a wide range of diseases, including rickets, anemia, and muscular dystrophy. At the same time, some vitamins, such as vitamin A, can be toxic if given in too high a quantity. Vitamin D deficiency is common in animals that are reared completely indoors; however, animals that spend at least some time regularly in the sun don’t have this problem, because vitamin D is synthesized by the body when exposed to sunlight.
Minerals
The mineral, or ash, component of feed is what remains after the laboratory fires the feed sample at a high temperature. Like vitamins, most of the minerals aren’t required in very large quantities, but deficiencies cause a wide range of health problems, and toxicity can occur when there are mineral excesses in the diet. The minerals include such elements as sodium, calcium, phosphorus, and selenium.
Mineral deficiencies (or excesses) usually occur where soil mineral imbalances exist. Plants that are grown in a soil that is either too low or too high in any given mineral will reflect the soil imbalance in their tissue. The best way to learn about soil mineral levels on your farm is to have soil and forage samples run (see appendix E, Resources). As an alternative, check with your local County Extension Agent, a reputable feed dealer, or your veterinarian for information on the general status of soil mineralization in your area. They can help you evaluate what types of mineral supplements will be best for your situation (your animals, your soil, and so on).
Mineral supplements are best fed free-choice. Animals are really quite efficient at controlling their intake of mineral supplements in order to meet their own needs. Our approach is to always have a free-choice plain white salt block and a free-choice trace-mineral block available. Another excellent source of vitamins and minerals that we put out is kelp meal. This dried sea plant provides a smorgasbord of vitamins, minerals, and amino acids that all animals seem to love.
Digestion
Some foods, such as sugar water, can be absorbed directly into the bloodstream, but most foods must be broken down into simpler elements and molecules prior to absorption. Digestion is the process by which this breakdown occurs, and it includes mechanical, chemical, and biological steps.
The first step in the process is always mechanical and involves the gathering, tearing, and grinding of food into smaller pieces with the mouth and teeth (or beak). Tearing and grinding food into smaller pieces allows it to pass through the esophagus, or gullet, to the stomach; it also increases the surface area of food particles, so that once they’re in the stomach gastric juices can attack these particles more readily. The gastric juices, which consist of acids and enzymes, are responsible for most of the chemical breakdown of food. Fermentation is the biological process, and it involves the help of beneficial bacteria.
Animals may be classified according to the configuration of their digestive system. There are three major classes (Figure 6.3):
1. The monogastric fermenters, or single-stomached critters (e.g., pigs, poultry, humans).
2. The postgastric fermenters (e.g., horses, rabbits). Postgastric fermenters have only a single stomach, but they have a well-developed cecum — a fermentation chamber that’s located between the small and large intestines. Although all animals have this organ, it is only well developed and highly effective in animals that are classified as postgastric fermenters.
3. The pregastric fermenters, or ruminants (e.g., cattle, sheep, goats). The ruminants have four stomachs, including the rumen, or first stomach, which acts as a large fermentation chamber. There is also a smaller class of pregastric fermenters that are known as pseudoruminants (llamas and alpacas). The pseudoruminants have three stomachs instead of four, but their digestive process is very similar to that of the true ruminants.
When food passes ou
t of the stomach, or stomachs, it enters the intestinal tract. In all the species, digestion continues as the food winds its way through the intestines. The vast majority of the nutrients are actually absorbed into the bloodstream during the trip through the intestines, particularly the small intestine. That portion of an animal’s diet that isn’t absorbed into the bloodstream as a source of nutrients is waste, and is passed out of the body as manure.
Animals with a monogastric digestive system have some disadvantages when it comes to digesting their food: They can only ferment a very small amount of the fiber that’s in their diet, and they can only synthesize a few of the many amino acids that their bodies require. This means that they get very little feed value out of hay or straw — though green grass, when it’s young and vegetative, can provide a good deal of feed value to them. It also means that their diet must have a wider variety of protein sources, including animal proteins, to meet their amino acid needs.
Figure 6.3. Mammals have three distinct stomach systems: the monogastric, the postgastric fermenter, and the pregastric fermenter. (A.) Pigs are monogastric, with a single stomach and a small, underdeveloped cecum. (B.) Horses are postgastric fermenters, with a single stomach and a highly developed cecum, or fermentation organ between the small and large intestines. (C.) The pregastric fermenters, like cattle, have four stomachs and a fairly well-developed cecum. Pregastric fermenters are also called ruminants, after the rumen, one of their four stomachs.
Small-Scale Livestock Farming Page 11