Macrominerals for sheep and goats
Sheep and goats require both macro and micro (or trace) minerals in their diets. The most important macrominerals are calcium (Ca), phosphorus (P), sodium (Na), and Chloride (Cl). Rations are usually balanced for calcium and phosphorus. Salt (NaCl) is usually either incorporated into the concentrate ration or or provided free choice, often with trace minerals.
Calcium is the most abundent mineral in the body. Ninety-nine percent is found in the skeleton. Calcium supports muscles and protects organs and tissues, including bone marrow. Calcium is required for growth and milk production.
Calcium requirements decrease with age, but increase with growth. Requirements for ewes rise rapidly during late pregnancy to a level equal to that for lactation. For goats, calcium requirements are higher during pregnancy but increase abruptly after kidding.
Prolonged calcium deprivation can manifest itself in a variety of ways depending upon the stage of growth. In young animals, a calcium deficiency usually results in rickets, where osteomalacia and milk fever are common in does and ewes. Rickets can also be caused by a deficiency of phophorus and vitamin D. A calcium to phosphorus ration of <1 may cause urolithiasis.
Forages are generally satisfactory sources of calcium, particularly when they contain leguminous species. Alfalfa containts 3 to 4 times more calcium than grasses and usually more than ruminants need (if it is fed as the main dietary component). Cereals are low in calcium. Although richer in calcium than cereals, vegetable protein sources do not contain adequate calcium when blended with cereals. Milk and milk replacers, of animal origin, are rich in calcium and well-absorbed by young. The calcium in soy based milk replacers is less absorbed.
Calcium is one of the least expensive nutrients. Sources include calcium carbonate, limestone, calcium chloride, dicalcium phosphate, and soft rock.
Calcium is generally not regarded as a toxic element, because excess calcium is excreted in the feces. According to the National Resource Council, the maximum dietary level of calcium is 1.5 percnet.
Phosphorus is the second most abundant mineral in the body and about 80 percent is found in the bones and teeth. The formation of bone is the most important function of phosphorus. Changes in bone structure and composition that result from phosphorus deprivation are the same as calcium.
Cereals are rich in phosphorus, most of which is stored in the seed coat. Vegetable protein sources are richer in phosphorus than cereals. The phosphorus content of forages varies widely and is influenced by the phosphorus status of the soil, stage of plant maturity, and climate. Alfalfa is generally richer in phosphorus than grasses. Grazing animals prefer pasture components that are richer in phosphorus.
Milk is an important source of phosphorus for the young. Colostrum is much richer in phosphorus than the main milk. The amount of phosphorus in bovine milk varies according to processing.
Phosphorus depreviation can result in poor appetite, depraved appetite (pica), reproductive disturbances, abnormalities of bones, depression of milk yield. Livestock generally tolerate excess phosphorus uptakes.
The greatest concern for with phosphorus may be related to the ratio of calcium to phosphorus. However, high phosphorus diets predispose livestock to urinary calculi, but in ruminants, these are only likely to form on diets consisting predominantly of concentrates.
While phosphorus is an essential element in the diet of livestock, it represents the most potential risk fo environmental pollution.
Sodium and chloride (salt)
Sodium and chloride are considered together because of their related metabolism, functions, and requirements in the animal. Sodium and chloride maintain osmotic pressure, regulate acid-base equilibrium, and control water metabolism in the body.
Forages are generally poor in sodium. They are appreciably richer in chloride than sodium, irrespective of species or stage of maturity. Pasture usually provide sufficient chloride for grazing animals, but they can be enriched with fertilization. Most grain and plant protein sources are poor sources of sodium, while root crops, root by-products, and animal products are rich in sodium.
Cereal grains provide more chloride than sodium. Cereal straws contain 3 to 6 fold more chloride than grains. Vegetable protein supplements are consistently low in chloride. Water sources vary widely in the amount of sodium, chloride, and other minerals they contain.
The presense of salt contributes to the palatability of feed. The addition of sodium can also lower feed intake and may be used as a means to restrict intake of supplements. Both sodium and chloride are readily absorbed, but each element can influece the absortion of the other. Most of the sodium that enter the GI tract comes from saliva. Sodium, chloride, and potassium are all lost via skin excretions. Sodium losses increase as temperature and humidity increase. Dietary excesses of chloride are predominatly exreted throught the kidneys.
For thousands of years, it has been known that animals (and people) need salt. Animals will risk graze danger or resort to unsual behavior to obtain it. When salt intake is below its requirements, it will conserve it. Urine output of sodium and chloride will practically halt. A continuous low intake of salt will result in a reduced feed intake. Animals will develop a craving for salt. They will lick dirt, wood, rocks, and other material to try to obtain it. They may consume toxic levels of plants.
According to the National Research Council (NRC), it is common to add 0.5 percent salt to mixed feeds and 1 percent to the concentrate portion of the feed. Grazing livestock should be provided free choice salt.
In flocks where urinary calculi has been a problem, salt can be added to the ration at a rate of 3-4 percent to stimulate water intake, dilute mineral concentration in the urine, and reduce incidence of disease.
Salt can be used to regulate grazing. Placing salt in underutilized areas may cause livestock to graze in those areas. It can also be used to regulate the consumption of supplements. Adding salt to the diet may reduce stress caused by marketing and transport.
Magnesium, Potasium, and Sulfur
Magnesium, potasium, and sulfur are other macrominerals required by sheep and goats.
Although most of the body's magnesium (60-70%) is present in the skeleton, magnesium is second only to potassium in abundance in the soft tissues. However, it is protein bound. Magnesium is associated mostly
Potasium is the major intracelluarl ion in tissues. It It is so abundant in common rations and pastures that nutritionists consider it to be a useful, but non-essential element. Naturally-occuring potasium deficiencies are rare in livestock.
Sulfur is an integral part of the majority of tissue proteins. The functions of sulfur are as diverse as the proteins of which it is part.
Sheep and goats differ from cattle in that hair and wool growth adds significantly to their need for sulfur.
An excess of dietary sulfur can lead to a deficiency in any of several elements, including copper and zinc. HIgh dietary levels of sulfur can also lead to polioencephalomalaica (PEM). Though variable in content, distiller's grains can be high in sulfur.