Nutritional Requirements of Goats
Goats should be provided unlimited access to fresh, clean, nonstagnant sources of freely accessible water. Goats are among the most efficient of domestic animals in their use of water; however, only ~10% of body water loss may prove fatal. They appear to be less subject to high temperature stress than other species of domestic livestock. In addition to a lesser need for body water evaporation to maintain comfort in hot climates, goats can conserve body losses of water by decreasing losses in urine and feces. Factors affecting water intake in goats include lactation, environmental temperature, water content of forage consumed, amount of exercise, stage of production (growth, maintenance, lactation, etc), and salt and mineral content of the diet. Goats grazing lush pastures may consume much lower quantities of water than those feeding on dry hay. Still, it is imperative to allow free access to water for all goats regardless of age, breed, purpose, stage of life cycle, or environment.
Energy limitations may result from inadequate feed intake or from poor diet quality; excessive water content of the feedstuffs also may become a limiting factor. Energy requirements are affected by age, body size, body condition, stage of production (growth, maintenance, pregnancy, and lactation), and concurrent medical conditions (eg, parasitism, dental disease, arthritis). Energy requirements also may be affected by the environment, hair growth, activity, and relationship with other nutrients in the diet. Increased temperature, humidity, sunshine, and wind velocity may decrease energy requirements. Shearing mohair from Angora goats and pashmina from Cashmere goats decreases insulation and results in increased energy needs (at least in colder environments).
Goats exhibit a wide range of grazing activity, ranging from light activity for goats under intensive management, through moderate activity on semiarid land, to high activity for goats grazing on sparsely vegetated grassland and on mountainous pastures that necessitate long-distance travel daily.
The best assessment of energy intake adequacy in goats is proper body condition or fat covering the loin, brisket, inner thigh, and ribs. Using herd/individual medical record systems, a standardized body condition score (1–5, with 1 being extremely thin, to 5 being extremely obese) should be used to monitor body fat changes and make less subjective decisions with respect to longterm dietary energy adequacy. If animals are parasite- and disease-free, yet underconditioned, then they are usually being fed an energy-deficient diet; the reverse is true for obese animals. The energy values required for growth and lactation are very comparable to the numbers used for sheep and cattle, respectively. Therefore, sheep nutrition principles from an energy standpoint will probably suffice when dealing with all classes of goats, except for lactating dairy goats.
Protein is required for most normal functions of the body, including maintenance, growth, reproduction, lactation, and hair production. Protein deficiencies in the diet deplete stores in the blood, liver, and muscles and predispose animals to a variety of serious and even fatal ailments. Feed intake and dietary digestibility are reduced if dietary crude protein is <6%, further compounding an energy-protein deficiency; thus, for maintenance of mature, healthy animals, the diet should have a minimum of 7% crude protein. Dietary crude protein requirements are higher for growth, gestation, and lactation.
Most forages contain adequate amounts of dietary protein for maintenance, but lactating, growing, sick, or debilitated animals may require diets fortified with legumes or protein supplements (eg, soybean meal, cottonseed meal, etc). Feeding adequate to slightly greater amounts of protein than required appears to aid in the control (both resistance and resilience) of internal nematode parasites.
Requirements for minerals have not been established definitively for goats at either maintenance or production levels. Research has been conducted with goats in mineral metabolism studies, especially with calcium and phosphorus. In general, these data support assumptions that several mineral requirements for goats are similar to those for sheep. (For detailed nutrient requirements for goats, refer to the most current Nutrient Requirements of Small Ruminants, published by the National Research Council; www.nap.edu.) Feeding to meet the goat’s needs will maximize its production, reproduction, and immune system. The addition of specific minerals (phosphorus for dry winter forages, selenium in deficient areas, etc) to salt (NaCl), preferably in granular form and offered free choice, helps prevent most mineral deficiencies and improves performance.
Calcium requirements are generally met under grazing conditions with either Angora or meat-type goats, but levels should be checked in high-producing dairy goats because a deficiency can lead to reduced milk production. Adequate levels of calcium for lactating goats are necessary to prevent parturient paresis (milk fever). In browsing or grain-fed goats, the addition of a calcium supplement (dicalcium phosphate, limestone, etc) to the feed or to a salt or trace mineral–salt mixture usually meets calcium requirements. Legumes (eg, clover, alfalfa, kudzu) are also good sources of calcium.
Phosphorus deficiency results in slowed growth, unthrifty appearance, and occasionally a depraved appetite. Goats can maintain milk production on phosphorus-deficient diets for several weeks by using phosphorus from body reserves, but during long periods of phosphorus deficiency, milk production was shown to decline by 60%. The calcium:phosphorus ratio should be maintained between 1:1 and 2:1, preferably 1.2–1.5:1 in goats because of their predisposition for urinary calculi. Phosphorus deficiency in grazing goats is more likely than a calcium deficiency. In cases of struvite calculi, the ratio should be maintained at 2:1.
Magnesium deficiency is associated with hypomagnesemic tetany (grass tetany), but ordinarily this condition is less common in grazing goats than it is in cattle. Goats do have marginal ability to compensate for low magnesium by decreasing the amount of magnesium they excrete. Both urinary excretion and milk production are reduced in a magnesium deficiency.
Salt (NaCl) is usually recognized as a necessary dietary component but is often forgotten. Goats may consume more salt than is required when it is offered ad lib; this does not present a nutritional problem but may depress feed and water intakes in some arid areas where salt content of the drinking water is quite high. Salt formulations are used as carriers for trace minerals, because goats have a clear drive for sodium intake.
Potassium has an important role in metabolism. However, forages generally are quite rich in potassium, so a deficiency in grazing goats is extremely rare. Marginal potassium intake is seen only in heavily lactating does fed diets composed predominately of cereal grains. Excessive potassium intake (particularly in late gestation) may be associated with hypocalcemia in dairy goats. If hypocalcemia is a herd problem, attention should be paid to reducing or monitoring potassium-rich feedstuffs (eg, alfalfa).
Iron deficiency is seldom seen in mature grazing goats. Such deficiency might be seen in young kids because of their minimal stores at birth, plus the low iron content of the dam’s milk. This is more commonly seen in kids fed in complete confinement and heavily parasitized animals. Iron deficiency can be prevented by access to pasture or a good quality trace mineral salt containing iron. In severe cases, and for kids reared in confinement, iron dextran injections at 2- to 3-wk intervals (150 mg, IM) for the first few months may be curative. In the cases of mixed iron/selenium deficiencies, caution should be used when injecting iron dextrans until the selenium deficiency is also corrected.
Iodine deficiency in the soil, and in the crops produced thereon, is seen in some areas of the USA. Therefore, iodine should be provided in stabilized salt. Conditional iodine deficiency may develop with normal to marginal iodine intake in goats consuming goitrogenous plants. Marked deficiency of iodine results in an enlarged thyroid; poor growth; small, weak kids at birth; and poor reproductive ability.
Zinc deficiency results in parakeratosis, stiffness of joints, smaller testicles, and lowered libido. A minimal level of 10 ppm of zinc in the diet, or a trace mineral salt mixture of 0.5%–2% zinc, prevents deficiencies. Excessive dietary calcium (alfalfa) may increase the likelihood of zinc deficiency in goats.
Copper deficiency may result in microcytic anemia, poor production, lighter or faded hair color, poor fiber quality, infertility, poor health and slowed growth, some forms of metabolic bone disease, diarrhea, and possibly a greater susceptibility to internal parasites. Copper deficiency in a diet may be caused by inadequate copper intake, a lowered copper-molybdenum ratio, or excessive dietary sulfur. Goats appear to be much more resistant to copper toxicity than sheep.
Selenium deficiency in the diet is usually associated with nutritional muscular dystrophy, retained placentas and metritis, poor growth, weak or premature kids, and mastitis.
Recommendations for vitamin requirements of goats are even more sparse than for mineral requirements. At best, almost all vitamin recommendations for goats must be based on those for sheep (see Nutrition: Sheep).