Salt & Animal Health

This month's issue of Physiological and Biochemical Zoology (you all do read that, dont' you?) carries an important story of enduring signficance about how curtailed dietary intake compromises the immune systems of deer mice. Researchers Lynn Martin et al of The Ohio State University report that cutting back just 30% of dietary intake "reduces secondary antibody responses in deer mice (Peromyscus maniculatus), functionally representing a cost of immune memory." Ohio State's been doing some good work in nutrition recently.

The results are another recurring reminder of this lesson long-taught and repeatedly-reminded: there are very real physiological costs in terms of unintended consequences in reducing "normal" dietary intakes. It's been more than 20 years, for example, since Dr. Mark Cook of the University of Wisconsin published results that curtailing salt intake in chickens impaired their immune system function. That's before most of the world woke up to the AIDS catastrophe.

Posted by Dick Hanneman at 03:48 AM | Permalink

In a strikingly clear and comprehensive manner, the paper entitled “Central Regulation of sodium appetite,” by Joel Geerling and Arthur Loewy of the Department of Anatomy and Neurobiology, Washington University School of Medicine in St Louis, MO, elaborates the mechanisms responsible for our appetite for salt. The physiological apparatus we have evolved over the eons to maintain a fully operational cardiovascular system is largely dependant upon maintaining both a balance and sufficient quantities of the two nutrients most essential to life, water and salt. This fundamental system is can be found in fish, reptiles and all mammals. Life depend on it.

In order for us to survive, our circulatory system must have an adequate volume of blood that is under sufficient pressure to supply all our tissues with the nutrients they need and to remove all the toxic byproducts of metabolism. It is a finely tuned balance of water and salt that allows this to happen. Any amount of water or salt that is consumed in excess of our needs is quickly eliminated through our kidneys. However, an equally important issue is ensuring that we have ingested enough water and salt to make up for any losses we experience. This is where the incredible mechanism controlling the thirst for water and the appetite for salt comes in.

This latest publication shows that this multi-factorial system is so robust and includes so many failsafe mechanisms that it continues to fully function even after large sections of its system are shut down. Employing a complex cascade of physiological functions from powerful hormones, such as aldosterone, to pressure sensitive receptors in the brain, this water thirst and salt appetite mechanism moderates our behavior so that we are driven to quickly replenish the volume and ionic balance of our blood, so that it is pressurized sufficiently for our heart to circulate it through our bodies. When fluids and electrolytes are lost, such as with sweating, physical exertion, diarrhea or other circumstances, we immediately get a water thirst signal. So we drink water to make up the loss. After a delay, our salt appetite kicks in to ensure that the ion levels are replaced. If we don’t respond on time to the salt appetite, we die – a situation which was described in an earlier article where a young woman died in a water-holding contest.

It has been repeatedly suggested that policies must be developed to reduce the amount of salt in processed foods. In fact, some countries already have or are in the process of considering policies to effect this. Will these policies be effective? What indication is there that people who are provided with a lower-salt food supply will actually reduce their intake of salt? Based upon this latest publication on salt appetite, individuals faced with foods that are mandated to be low in salt may make up for this in other ways. They may eat considerably more food in order to get more salt or they may simply pick up the salt shaker and add more voluntarily.

The recent publication by Shapiro, Boaz, Matas, Fux, and Shargorodsky as described in a recent article legitimately brings up the question of minimum levels of salt intake. Based upon their data, we can justifiably ask whether the current recommended daily values are prudent. Should the 2,300mg daily upper limit for sodium be reconsidered? Should the Institute of Medicine recommended daily adequate intake of 1,500mg sodium be reconsidered?

Our thirst for water is a basic mechanism we have evolved in our fight for survival. So is our appetite for salt. It is time we realize that the two mechanisms are interdependent and basic to our survival. Any policies promulgated to regulate our consumption of salt must bear this in mind and be based on the most rigorous science. If not, harm will be done.

Posted by Mort Satin at 04:08 PM | Permalink

Larry Berger's article in Salt and Trace Minerals newsletter, extolling the economic virtues of using salt to promote rotational grazing, was just reprinted in the American Cowman. Recycling par excellence.

Posted by Dick Hanneman at 10:45 AM | Permalink

In a world of competing imperatives, it is difficult to satisfy everyone. However, Dr. Larry Berger describes a management system that is doing just that. He believes that the weight-gain efficiencies of grain-based feed lots and the ecological and agronomic benefits of natural grazing don’t have to be mutually exclusive approaches. The ideas behind these feeding system can be combined into a management feeding approach that takes the best of each. It’s called rotational grazing and is described in detail in Larry Berger’s article, “Salt and Rotational Grazing,” which appears in the July, 2007 edition of the Angus Journal.

Rotational or management-intensive grazing, can increase beef production per acre by 30% when compared to traditional grazing. All it takes is good, hands-on management and a bit of common sense technique. Rotational grazing requires the division of large pastures to several smaller paddocks which are grazed in short (2-4 day) intervals before moving the cattle on to the next paddock. When 10 or more paddocks are involved, grazing cycle repeats itself at roughly 30-day intervals.

The benefits are self evident, but we’ll list them anyway. First of all there is increased beef production per acre, then more uniform grazing which prevents bare spots, then the animal waste is more evenly distributed across the paddock and finally, the improved nutrient recycling increases forage production, which brings us back to increased beef production per acre. Pretty nifty, isn’t it?

But it doesn’t stop there, because cattle that graze lush forages have an increased appetite for salt. In fact, they will usually consume twice as much salt as those fed high cost, high-concentrate diets and salt is an excellent carrier of essential micronutrients as well as ionophores such as monensin. Feeding studies report that self-feeding a salt-monensin-supplement gave the same daily gain as hand-feeding the monensin supplement without salt. Salt, the most reliable intake regulator can be made even better when combined with monensin leading to increased beef production. But, it doesn’t stop there either.

A deeper knowledge of cattle and their grazing habits prompted the use of salt feeders as management tools to accomplish other objectives aside from meeting the cattle’s nutritional requirements. For instance, fly populations are a major challenge to grazing animals. The Noble Foundation found that combining the salt feeder and cattle rub in the same tool, was one of the most effective ways to control flies. Recent research show that weight gains were increased 27 lb. per head for weaned calves and by an average of 17% in yearling grazing cattle when flies were controlled.

To sum up, rational hands-on grazing management, using salt and rotational grazing leads to increased beef production per acre – or did we say that before?

You can read Larry Berger’s latest Salt and Trace Minerals Newsletter, “Factors Affecting the Trace Mineral Status of Feeder Calves,” along with a full library of practical nutrition and feeding papers at the Salt Institute salt and trace minerals in animal nutrition

Posted by Mort Satin at 03:27 PM | Permalink

Western Australia has more than 2.5 million acres of severely-affected saline soil and has instituted a vigorous program to make better use of this land. While other countries, including the United States, don’t have the problem to the same degree, increasingly saline soils will be a growing problem in the future and we would all do well to closely follow the developments in Australia.

Common saltbush is a grayish-white shrub that grows to be about 2 to 3 feet tall. The common saltbush is often mistaken for "sagebrush" although it is actually related to the "tumbleweed", or Russian thistle. It gets its name from the salty deposits on its leaves. When the saltbush takes up water from salty, alkaline soils, it removes and deposits the excess salt in bladders on its leaves. This keeps the salt away from the plant cells and also attracts moisture in the air for the plant to absorb. When the leaves are eaten or fall off, the extra salt is removed from the plant.

Common saltbush is sometimes called "cattle spinach". It is very important as a browse plant for cattle and sheep because it is a great source of minerals, especially salt, which they need. As described in this week’s edition of Australian Food News, Dianne Mayberry, a PhD student from the Cooperative Research Centre for Plant-based Management of Dryland Salinity has thrown her energies into making digestion of saltbush by sheep more efficient so that it can provide far greater commercial value.

This idea may be worthwhile considering in remediation of some roadside soils routinely impacted by saline runoff.

Posted by Mort Satin at 10:43 AM | Permalink

A number of years ago, I was involved with a micro-encapsulation research program related to increased wool grow in sheep. The idea was to micro-encapsulate methionine so that it could survive the conditions in the front end of the rumen and be incorporated into the digestion taking place in the abomasum (the fourth compartment of the stomach of a ruminant). When digested at that point, methionine was shown to contribute to a significant increase in wool production.

The latest research reports coming out from down under indicates that such a costly and complex system may not be necessary to increase wool production.

The May 14, 2007 issue of the AllAboutFeed Newsletter indicates that increased dietary salt can increase wool growth across a range of sheep diets. These results suggest that increasing salt in the feed ration may be a viable strategy to increase wool production efficiency.

In trials carried out over 2 months, 18 month old Merino wethers were individually penned and offered one of l6 different diets. The feeds were formulated with four levels of added sodium chloride (nil, 7%, 14%, and 21%) and four levels of organic matter digestibility (55%, 62%, 69%, and 76%). Treatment feeds were offered ad libidum for seven weeks and at maintenance during the final week. Researchers found that clean wool growth, corrected for digestible organic matter intake, increased by 16%, 18% and 27% as added sodium chloride was increased by 7%, 14% and 2l% respectively. On the other hand, liveweight gain was reduced from increasing dietary sodium chloride, mostly as a result of reduced feed intake at the higher salt levels.

While higher levels of dietary salt may be favourable for wool production efficiency, the decrease in the feed intake of sheep needs careful management for commercial livestock production.

Now, if the same mechanism worked for hair, we might have a highly palatable cure for baldness.

Posted by Mort Satin at 11:58 AM | Permalink

U.S. salt producers sell more salt for animal nutrition than for human nutrition. Those sales will likely be bolstered by the record 10.9 million cattle now in U.S. feedlots, according to the U.S. Department of Agriculture -- more than a million more than a year earlier.

Posted by Dick Hanneman at 05:04 PM | Permalink