Salt for Poultry

Salt deficiency results in lower feed consumption, loss of weight, lower egg production, occasionally a loss in egg size and slower growth in broilers (79, 80, 81, 203). Sodium chloride deficiency can also increase the bird’s susceptibility to disease by suppressing the immune system. Recent work by Pimentel and Cook showed that Hubbard broiler chicks fed diets containing less than 0.14% sodium or 0.17% chloride had depressed immunity to sheep red blood cells as compared to chicks fed higher levels of sodium and chloride (203).

Diet ingredients used today in poultry feeding are deficient in sodium and chloride, so salt must be added for optimum performance. Mississippi data indicate that the body stores of sodium reserves in hens are negligible and last only about a week. Salt is not self-fed to poultry, so their needs must be met by an adequate level in the diet. Salt deficiencies will occur occasionally in commercial practice, as was found in Colorado (80). This could be due to situations where not enough salt is fed or salt requirements are higher than normal due to heat or other causes.

Rapid changes in the physiology of the small intestine occur in layers on a sodium deficient diet (227). After three weeks on a low-sodium diet the microvillus surface area more than doubled due to an increase in the number and size of epithelial cells. Greater density of open sodium channels also increased the net sodium transport. These observations demonstrate the physiological importance the laying hen puts on absorbing adequate sodium.

Recent research with broilers has shown that sodium and chloride concentrations recommended by the 1984 NRC publication for poultry was below the requirement for maximum growth using a corn-soy diet (202). These data suggests that the sodium requirement for broilers is 0.5% for the first week decreasing to 0.3% by three weeks of age. The higher sodium and chloride requirement is probably due to the faster growing strains of broilers being used today, the higher energy diets being fed, and the fact that sodium and chloride in drinking water was not taken into account in initial estimates of the requirement.

Mississippi studies showed that two different types of salt (rock salt and evaporated salt) produced essentially equal growth responses and feed utilization in chicks when the particle size was equal (45, 46). Salt with a particle or crystal size range between U.S. Bureau of Standards Number 18 to Number 25 sieve sizes (0.0394 to 0.0278 inch openings) achieved maximum growth rate. Salt of a size range either larger or smaller than Number 16 through Number 30 sieve sizes (0.0469 to 0.0234 inch openings) supported a lower growth rate.

Excessive levels of salt are toxic to poultry, but there is considerable variation in the levels considered toxic by various investigators. Younger birds seem more susceptible than older birds to salt toxicity. The feeds in the diet as well as the level of certain nutrients can influence toxicity levels. Chicks also exhibit individual differences in tolerance for excess salt. Poultry on high-salt diets increase their consumption of water almost in proportion to the excess salt (127).

Illinois work showed that chickens may be raised from 9 to 21 weeks of age on diets containing as high as 8% salt with no apparent detrimental effect on their condition (32). Maryland studies showed that baby chicks fed 8% or more salt experienced retarded growth (33). Canadian data from a more recent experiment showed that increased mortality occurred when 3% or more salt was added to the diets of chicks reared from hatching to 9 weeks of age (34). On the other hand, a Cornell study showed no effect of 4% salt in the diet on mortality of chicks to 8 weeks of age (40).

Table 7 shows data on the percent water in tissues of the chicks in the Canadian study (34). It is interesting that skin was the tissue most affected by an increase in water content as the salt level increased.

Table 7. Water Content of Some Tissues Affected by the Salt Content of the Diet (34)

Percent Salt		Percent	Water
Added to Diet	Skin	Liver	Heart Muscle	Leg Muscle
½	50.0	72.2	75.7	76.1
3	63.6	72.2	75.1	77.5
5	59.0	73.4	78.5	78.0
7	76.9	72.4	78.6	73.5
9	82.9	73.7	82.5	77.8

Turkeys are more susceptible to salt toxicity than chickens. Connecticut workers reported that turkey poults readily tolerate levels of salt up to 2% if the diet is otherwise relatively free of salt (35). James reported that 2% salt in turkey poult diets increased mortality rate (36). However, mortality did not occur with a level of 1% salt added to the same diet.

A Canadian study showed that turkey poults fed up to 1.5% salt and 1.5% sodium did not exhibit signs of round heart disease (82). The study did not verify field recommendations to reduce salt intake, because round heart disease could be due to high salt intake.

An Illinois study showed that pheasants can tolerate 5% salt in the diet without any harmful effects (37).

Care should be taken with levels of salt added to poultry diets. The margin between a safe level and a harmful level is not great under some conditions. In addition, excess salt can increase fecal moisture levels which can be a management problem in most housing units. Cornell research suggests that 2.5 g salt/liter of drinking water increased water intakes by 15%, but did not visually alter the texture of the excreta (290)

In summary, it seems that the addition of one percent salt, probably the highest level to add to any poultry diet, is safe and will cause no toxic effects even with very young birds.

Controlling salt in water is more important than in feed. Levels of 0.4%, 0.9%, 1.2% and 2.0% salt in drinking water have shown harmful effects with poultry. Doll and co-workers reported no clinical evidence of toxicity with levels of 0.25% (2,500 ppm) sodium chloride in drinking water for chicks (38). A Canadian study showed that chicks can tolerate water containing as much as 0.5% salt even when the feeds contained 0.5% added sodium chloride (44). Clearly, water containing high salt levels should not be used for poultry. Based on current evidence, a level of 2,500 ppm salt in the water probably would not cause toxic effects (127), but may increase egg shell defects (290).

1984 NRC recommendations are for 0.15% sodium in all diets for chickens, ducks, pheasants, bobwhite quail and Japanese quail, while turkey poults start out at 0.17% and decrease to 0.12% sodium (141). The chloride requirement for these same species ranges from 0.12% to 0.15%. However, recent Georgia data show that optimal concentration of both sodium and chloride is 0.4% for broilers up to three weeks of age (202). Depending on the sodium and chloride in the basal ingredients, this would require approximately 0.9% salt. Canadian workers found the addition of 1% salt to a mash diet for chicks to be optimum for growth and superior to a group with 0.5% salt added (34). In a Wisconsin study with corn, wheat bran, standard wheat middling, dried skim milk and meat scraps, researchers concluded after a number of trials that the addition of 0.5% salt to the diet will meet the salt requirements of either growing chicks or laying hens (39).

Florida studies (204) have shown that feeding a corn-soy diet without added salt to Leghorn or broiler breeder hens causes an immediate drop in feed consumption and body weight with egg production dropping to near zero in 21 days.

A Cornell study with chicks up to eight weeks of age showed the minimum salt requirement to be 0.65% of the diet (40). An Illinois study with purified diets found the sodium requirement of the chick, up to 4 weeks of age, to be 0.11% on one diet and 0.20% on another (41). This is the equivalent of 0.28% to 0.50% sodium chloride in the diet.

Summers and co-workers in 1967 demonstrated that a chloride deficiency condition can exist on a practical corn-soybean meal diet in which the sodium chloride has been removed and sodium is provided from a source other than sodium chloride (42). The study was conducted with chicks up to three weeks of age. The study suggested that the requirement for chloride lies somewhere between 0.073% and 0.22% of the total diet.

A Nebraska study (43) showed that a level of 0.15% to 0.2% sodium in the diet was required for turkeys up to four weeks of age for maximum gain and feed efficiency. It also found that a level of 0.4% sodium chloride was required in a corn-soybean meal diet containing no ingredients of animal origin. The scientists also reported an interaction between sodium and potassium and suggested an optimum ration of about 2 to 2.5 parts potassium to one part sodium in young turkey diets.

An Illinois study showed that under practical conditions, the sodium requirement of both pheasants and quail was approximately 0.085%, and chloride requirement was between 0.048% and 0.11% of the diet (37). The addition of 0.15% salt to the diets satisfied both the pheasant and quail sodium and chloride requirements. The 1984 National Research Council poultry publication recommends a sodium level of 0.15% and a chloride level of 0.11% of the diet (equivalent to 0.21% salt) for pheasants and quail (141).

Mississippi studies have shown that the sodium requirements of cage hens are approximately twice that of hens kept on floor (47, 48). Floor hens recycle some sodium from their droppings, a fact to take into consideration in adding salt to diets of hens in cages.

The level of salt used in chicken, turkey, duck, goose, pheasant and quail diets will vary from 0.25% to 0.5%. The kind of diet fed, the stage of the life cycle, the environmental conditions encountered, the level of productivity and other factors will influence the total level of NaCl to use in the diet.