SALT FOR BEEF CATTLE

Required for Optimum Nutrition

Feed represents about 70% of the total cost of beef production. Numerous studies have shown that sodium chloride supplementation is an essential part of a balanced diet required for efficient beef production. If diets are deficient in salt, the producer risks significant economic loss long before outward deficiency symptoms appear. For example, in a Kansas State trial, calves were wintered on silage plus one pound of a soybean meal pellet daily.Those calves that were self-fed salt gained 1.26 pounds daily; while those not receiving any salt only gained half as much 0.65 pounds per day. Calves fed salt consumed 28.5 pounds and those without salt 26.1 pounds of feed daily, so that the amount of feed required per unit of gain was almost doubled when salt was absent.

In another Kansas study, steers fed salt gained 65 pounds more than those without supplemental salt over a 327-day period. In a 1971 trial, steers on full feed consumed about 5 cents (20 cents in 2000 dollars) worth of extra feed, but gained approximately 50 pounds more than steers not receiving salt.

A salt deficiency can also cause cattle to choose an imbalanced diet in order to get additional sodium or chloride. For example, Harbers et al.  reported that when feedlot heifers were fed whole shelled corn and supplement separately, cattle without any supplemental salt consumed 1.15 pounds more protein supplement per day compared to those receiving free-choice salt. The supplement contained 0.26% sodium compared to the 0.01% sodium in the corn. Since the supplement was the most costly ingredient in the diet, costs of gain increased significantly due to a lack of salt.

A 1973 Australian report showed that salt supplementation significantly increased the gains of lactating beef cows and their calves while grazing native pastures.

In the examples discussed above, significant improvements in performance and reductions in the costs of production occurred with salt supplementation. It is important to note that these improvements were obtained prior to any deficiency symptoms.

Deficiency Symptoms

Usually the first sign of a salt deficiency in beef cattle is a craving or abnormal appetite for salt. Cattle may lick various objects such as rocks, wood, soil and the sweat of other animals. Sometimes, no other visible symptoms occur for months. Then appetite begins to decline, the animal subsequently develops an unthrifty appearance with a rough hair coat. This is followed by a rapid loss of body weight and a reduction in milk yield. Eventually, a sudden death will follow a prolonged salt deficiency.

Salt in Grazing Distribution

Because cattle have a very strong appetite for salt, it can be used as a management tool as well as a source of nutrient. For example, salt blocks or salt stations can be used to increase the carrying capacity on range by causing more even grazing. This procedure causes animals to go to lightly used forage areas that have less succulent or less palatable forage and to less accessible areas in rough or wooded terrain or farther from water or shade. This method was successfully used with salt-protein supplement mixtures by the USDA Woodward, Oklahoma Station, where salt-protein mixtures placed up to three miles from water helped distribute grazing over the range. Other scientists have also placed salt blocks in less frequently utilized forage areas to increase forage use. When salt was placed approximately 1.5 - 2.5 miles from water, range utilization was improved by increasing grazing 12% on the under-utilized area and reducing grazing 10% on the over-utilized area closest to the water. In many mountainous or inaccessible areas, salt blocks or complete mineral blocks that include salt are dropped by plane to get minerals to the animals and help distribute grazing (60).

Salt as an Intake Regulator

The 1996 Beef NRC states, “high concentrations of salt have been use to regulate feed intake”.  However, the use of salt to control the intake of protein and energy supplements on pasture is not a new concept. Recent research and changing economics in the beef industry have caused a resurgence of interest in this topic.

With the increased selling price of feeder cattle, the economics of supplementing protein and energy to grazing cattle has become much more favorable. With feed costs at approximately 50 cents per pound of gain, and selling price in excess of 75 cents per pound, the profit potential for feeding supplements on grass is obvious.

In addition, there are always those situations where due to drought or over stocking, supplemental feed on pasture is needed to extend the carrying capacity of the range. When feed supplies are short, it is impossible to achieve uniform intakes with hand-fed supplements because dominant animals often get much more than their portion while timid animals may get none. In all these situations, opportunities exist to use salt to control the intake of a self-fed supplement without the large investments in facilities and labor required to hand-feed a limited amount of supplement on grass.

Numerous research studies over the past 40 years have demonstrated the efficacy of using salt to control intake and support performance equal to hand-feeding. Meyer et al.  fed a diet containing approximately 50% forage and 50% concentrate with or without 9.3% added salt to finishing steers. At the end of the 84-day feeding period, average daily gain, feed efficiency and dressing percentage were nearly identical for both groups. Steers fed the high salt diet consumed 7.0 gallons more water per day and tended to have heavier kidneys per unit of carcass weight. These researchers did demonstrate that because of the increased water intake, digestive tract fill will be increased for several hours after a meal. However, if cattle are fed normal salt intakes, differences in gut fill are eliminated in a short time as indicated by the equal dressing percents for steers on both treatments.

Salt, as high as 30% of the supplement, has been used to restrict supplement intake to 1.9 pounds per day. This high level of salt was required because the Pangola grass pastures were of poor quality containing only 5.5% crude protein. Steers fed the salt-limited supplement gained 1.04, while steers hand-fed the same amount of supplement, minus the salt, gained 1.12 pounds per day. In this study there was no difference in blood sodium, hemoglobin or hematocrit due to high salt intakes. Feeding regimes used in this trial did not affect dressing percentage, rib-eye area or carcass grade when the cattle were slaughtered directly off grass.

More recently, Harvey et al. compared the efficacy of using salt to limit supplement intake in hay and corn silage based diets in two different years. Soybean meal based supplements were used containing approximately 28% salt, with an intake of about 1.1 pound of soybean meal per day. This high level of salt did result in considerable variation in individual intakes of supplement and somewhat reduced gain on the corn silage based diet during year one of the study. However, performance was nearly identical for steers fed the two hay diets during the first year and on both the corn silage and hay diets during the second year.

In this trial, rumen parameters were monitored to determine how salt may affect rumen fermentation. One could theorize that increased consumption of water associated with salt intake may increase rate of passage of undigested residue from the rumen resulting in increased intake. In this study, rumen liquid dilution rates were increased from 6.3% to 10.4% per hour on the corn silage diet and from 7.8% to 9.1% per hour on the fescue hay diet due to salt intake. However, solid dilution rate was not affected which explains why there was no difference in forage intake. Previous studies  showed that cows fed alfalfa hay based diets containing 10.75% salt did not reduce cellulose digestibility compared to cows fed the same diet without salt. Similarly, Chicco et al. showed that cellulose and protein digestibility were not affected by using salt to control intake.

Salt additions to the diet can change the rumen fermentation pattern. Rogers et al. infused 500 or 1,000 grams of salt per day into the rumen of Holstein steers fed high roughage or high concentrate diets. These levels of salt infusion are equal to 5.2% and 9.5% of diet dry matter, respectively. With the high concentrate diet, molar percent acetate in rumen fluid increased and molar percent propionate decreased due to salt infusion. Acetate:propionate ratio was not changed on the high roughage diet. These data suggest that with steers fed high concentrate diets, some starch or soluble carbohydrates are flushed out of the rumen due to increased liquid dilution rate, resulting in a fermentation higher in acetate. These changes in rumen fermentation could be beneficial to lactating dairy cows by helping to increase butterfat in milk, but would have little impact on performance of grazing cattle.

While the "science" of using salt to regulate intake has been adequately researched, the "art" of using this technology is still developing. The following is a list of pertinent considerations to keep in mind as one develops a system to use self-fed, salt-limiting mixtures for cattle and sheep.

First, the proportion of salt in the self-fed mixture may vary anywhere from 5% to 40%. To determine how much salt is needed, you first need to know the desired amount of supplement intake. If you want to restrict intake to 1 to 2 pounds per day, as high as 30% to 40% salt may be required with mature range cows. Yearling cattle grazing high quality forage may require only 5% salt initially to limit intake to a pound per day. However, as cattle grow and the grass gets more mature and less plentiful, 20% to 30% salt may be required to maintain desired levels of intake. California researchers found that 8% to 10% salt was required to limit concentrate intake to 1% of body weight for yearling steers grazing lush, irrigated pastures.

From these data, it is obvious that factors other than desired intake also affect the concentration of salt required. These include such factors as age and weight of the animals, in that older animals require more salt to obtain the same level of restriction. As quality and quantity of the forage decreases more salt will be required. As animals become accustomed to the salt mixture, it may be necessary to increase the proportion of salt. The finer the grind of the salt being used, the less is required to obtain the same restriction. As salinity of drinking water increases less salt is required. As weather becomes more severe, more salt is required because animals are less prone to graze.

When used to control intake, salt mixes are most effective when fed in meal form. Pelleting feeds prevents the salt from inhibiting intake as rapidly and can result in overeating. Similarly, if animals are very hungry, it is recommended to hand-feed the salt mixture for a week before allowing free-choice access. During severe feed restriction, some animals may over consume if they are not adjusted to the salt mixture gradually.

A clean, plentiful water supply is a must when using salt to control intake. Water requirements can easily increase by 50% to 100% when using this system. During severe cold or blizzard, when stock tanks or ponds may freeze and animals tend to increase their intake of the salt mixture, adequate water is required to prevent the risk of salt toxicity. However, it is best not to place the salt mixture next to the water supply as it can restrict grazing distribution on the range.

Self feeders should protect salt mixtures from wind and rain and be portable. Usually about 20% of the animals should be able to eat from the feeder at one time. By knowing initial volume and weight of the salt mixture placed in the feeder, and marking the level of feed in the feeder every few days, one can calculate the amount being consumed per head per day. This will allow salt concentrations in future batches to be adjusted without having to let feeders become empty before intake per head can be determined. If it is important to keep intake at a constant level, self feeders should be filled every two to three weeks to allow for adjustments in salt concentrations. It is not uncommon to adjust salt concentrations 4 to 7 times to maintain desired intake over a normal grazing season.

Recent research  has shown that the number of adjustments in salt concentration required to maintain the desired intake can be cut in half when monensin is included in the salt mixture. Monensin, marketed as Rumensin, is cleared as a feed additive to increase daily gain of grazing cattle. Another advantage of including monensin is that it allows the use of a salt concentration that reduces the animal to animal variation in intake. In the studies reported by Muller,  self-feeding a salt-monensin-supplement gave the same improvement in daily gain (0.2 pounds per day) as hand feeding the monensin supplement without salt. These data show that salt, an already proven intake regulator, can be made even better when combined with monensin. Although less data are available with lasalocid, a Georgia study showed that lasalocid fed in a free-choice salt and mineral mix increased the gains of replacement heifers, cows and calves. Using salt as an intake regulator of self-fed supplements on grass is one management tool that can increase the profit of many cattle producers.

Effects of High Salt Intake

Cattle can tolerate high salt intakes if adequate water is supplied. For example, in an Arizona study  two pounds of salt were placed directly into the rumen through a fistula. When given free access to water no toxicity symptoms developed. When the salt was mixed with three gallons of water and no other water offered, salt toxicity symptoms began in 8 to 12 hours. Symptoms observed were anxiety and hypersensitivity, followed by loss of coordination and finally collapse. Rumen contractions increased in rate and intensity. When the excess salt was flushed from the rumen, the cow recovered rapidly.

In Texas studies, cows were fed as much as 2.99 pounds of salt per day for 22 days without harmful effects. High salt intakes had no detrimental effect upon the reproductive performance of the cows. Total chloride excretion of the "high-salt" cows was 11.5 times that of the controls, with 98.3% of the chloride intake excreted in the urine. Histological studies showed no kidney damage. The cows fed the high salt levels consumed considerably more water and excreted a much greater volume of urine than cows receiving only a normal salt allowance.

An Arizona study showed that the maximum salt (NaCl) concentration in the urine was 2.3% . Seawater has 2.6% NaCl. Consequently, for each pound of salt absorbed, the animal must produce about five gallons of urine to eliminate it . This is why plenty of water is needed when cows are fed high levels of salt.

A 1976 Purdue study showed that cattle offered ground corn mixed with 10% salt consumed an average of 1.4 pounds of salt daily with no harmful effects.

Hereford steers were fed high grain diets containing 0.5%, 3%, 5% or 7% NaCl for 126 days. Growth and feed efficiency were not affected by the level of NaCl, although feed intakes, organic matter intakes and carcass weights were reduced at the 7% level as compared to the 0.5% salt level .

Although high salt intakes are safe for cattle, a question often asked is whether it affects the utilization of other minerals. To answer this question, USDA conducted a study involving 700-pound steers fed a pelleted diet containing 1%, 2%, 4% and 8% salt). The study was designed to determine what the effect of high levels of sodium chloride (salt) would have on the retention of calcium, phosphorus, magnesium, sodium, potassium, chloride and water in beef cattle. The results were as follows:

1. Calcium - Calcium retention was increased significantly by each increase in the dietary salt up to the 4% level. Decreased fecal loss of calcium was responsible for this effect. There was no difference between the calcium retention on the 4% or 8% salt levels.

2. Phosphorus - Phosphorus retention was higher when 2% or 4% salt was fed than for 1% or 8% salt. The decreased fecal phosphorus excretion appeared to be primarily responsible for the difference in retention at the 2% and 4% salt levels, but this was offset on the 8% level by the increased loss of phosphorus in the urine.

3. Magnesium - Magnesium retention was not affected significantly by the salt level. Similar to the excretion of calcium and phosphorus, the majority of the magnesium excreted was in the feces.

4. Potassium - There tended to be less potassium retention on the higher levels of salt. The urine accounted for the majority of the potassium excreted. There was considerable variation between treatments, which made it difficult to analyze the data and show significant differences at the four salt levels used.

5. Sodium - The amount of sodium retained was higher for the 4% and 8% salt levels, but the percentage of sodium consumed that was retained was not significantly different among the four levels of salt. Urine sodium tended to increase with increasing level of dietary salt. The majority of the sodium and chloride is excreted in the urine.

6. Chloride - The 4% salt level caused the highest retention of chloride, both in quantity and percentage of that ingested. More chloride was retained at the 8% salt level than at the 1% or 2% salt levels, but the percentage retained was no different at the 2% and 8% salt levels.

7. Water - The amount of water retained was not affected significantly by the dietary salt. The amount of water consumed and urine excreted increased with increasing levels of salt in the diet.

This study indicates that feeding levels of salt much higher than ordinarily used in cattle feeding did not have any harmful effects on the cattle. In fact, in most cases mineral retention increased. The 1984 NRC publication recommends that 10% NaCl in the diet is the maximum tolerable level to use .

Salt Tolerance Levels in Water

In a series of studies at the University of Nevada, it was found that growing heifers could consume, during the winter, water containing 1% (10,000 ppm) NaCl without harmful effect if water was continuously available). Water containing 2% salt (20,000 ppm) was toxic, however, and caused loss of appetite, weight loss and anhydremia (a deficiency of the fluid portion of the blood). Two percent is a high level of salt when one realizes that seawater contains 2.6% salt.

Since cattle on the range often drink infrequently, water with salt was offered only once daily or every two days in some Nevada trials. Heifers refused to drink water with 1% salt when available only once per day or every two days. Subsequent experiments, however, showed that water with a level of 0.5% salt (5,000 ppm) was consumed when offered only once a day. The cattle continued to consume water once daily when the salt level was raised to 0.65%. However, feed consumption decreased under these conditions.

These studies indicate that cattle tolerate more salt in drinking water if it is continually available. This information is of value to those living near the ocean where salt intrusion into water supplies is possible. Work at South Dakota showed 7,000 ppm salt (NaCl) in drinking water was acceptable for beef cattle. A level of 10,000 ppm decreased rate of weight gain but did not cause other effects.

Both the Nevada and South Dakota studies indicate that a level of 7,000 ppm salt (NaCl) might be the top level to allow in drinking water for beef cattle. Other mineral salts in the water must also be taken into consideration. For example, sulfate salts are more harmful than chloride salts. In evaluating water quality, therefore, total dissolved solids in the water must be considered, not just NaCl. In many cases, sodium chloride is blamed for harmful effects actually caused by other mineral salts.

Salt Effect on Rumen Fermentation

Arizona digestion studies with cattle and artificial rumen fermentation experiments showed that the increased salt concentration of the rumen caused by feeding high-salt diets does not decrease rumen microbial activity . Both types of experiments showed that digestible cellulose, as well as digestible gross energy, is not altered by the increased salt consumption. The Arizona results have been confirmed in other research, including an Oklahoma study and a 1971 Venezuelan trial, where digestibility of nutrients was not affected by high salt levels .

In many trials, the addition of salt to diets lacking salt has increased the digestibility of certain nutrients. This was shown in a number of Kansas trials. Thus, it appears that the use of salt at high levels will not hinder digestibility of any nutrients, and it may increase the digestibility of some.

Salt Requirements

The sodium requirement for beef cattle is the primary factor determining how much salt should be fed. Morris  reviewed several papers and concluded that the sodium requirement was approximately 0.08% for growing cattle and 0.10% for lactating cattle. If the sodium was supplied from salt, this would be equivalent to 0.2% and 0.25% salt in the diet, respectively. The sodium requirement is increased with lactation because cows milk contains approximately 630 ppm sodium. The sodium requirement will also be increased when cattle are fed diets that increase fecal water excretion. Fecal water is the major route of sodium loss for cattle fed lush forages. Lush forages are also high in potassium which will tend to increase sodium excretion. This undoubtedly is the major reason that grazing cattle and or cattle fed silages have increase voluntary salt intakes compared to cattle fed high concentrate diets.

Free-choice feeding of salt for grazing cattle is the safe recommendation. Lactating cows grazing lush forage will have a higher sodium loss than other classes of cattle so that free-choice feeding allows them to adjust their intake. Feedlot cattle should receive approximately 0.25% salt to ensure maximum performance. Higher levels of salt may be beneficial in unique situations. For example, feedlot diets containing 0.5% to 1% salt have reduced the incidence of urinary calculi. The salt increases water intake resulting in a more dilute urine that is less conducive to stone formation.

Salt Affects Carcass Value

In today’s beef production system, carcass quality grade is an important factor determining the value of feedlot cattle at slaughter. Research at the University of Minnesota has shown that salt level in the diet can affect marbling score, which is the most important factor determining quality grade. Steers fed a diet devoid of supplemental salt had significantly lower marbling scores than those receiving 12.5 grams of salt daily. In the same trial, steers fed 37.5 grams of salt per day had significantly larger rib eyes than those without salt.

Saved in May 2002 from the site  http://www.saltinstitute.org. and not available anymore. Adapted and illustrated to be posted by Leopoldo Costa.