What could be easier than throwing a salt block off the back of a truck for each group of grazing cattle in a cow herd? Or filling a part of a mineral compartment with loose salt? Then coming back in a week or so and putting out salt in one of these ways, again? It is also inexpensive to feed salt to cattle, and they seem to eat what they need to satisfy their appetite. The only danger of feeding salt is cutting your hand, like I once did when loading salt blocks onto the back of a truck.
Once placed, cattle licking salt blocks or eating loose salt (both of which contain about 39 per cent sodium and 61 per cent chlorine) are not really seeking to meet their National Research Council (NRC) requirement for sodium and chlorine. Rather, they are satisfying an intuitive dietary craving, which if not satisfied will lead to an eating disorder called pica, where cattle will eat dirt or wood to satisfy their need for salt (also observed in some other mineral deficiencies).
The NRC dictates the dietary sodium level contained in salt (chlorine requirements are not established) for beef cattle should be at least 0.06-0.08 per cent of diet (dmi basis) for growing calves and older replacement animals and about 0.1 per cent of diet (dmi basis) for mature beef cows. For example, grazing mature beef cows 15 kg of forage per day calculates into providing about 40 grams of salt (15 x 0.1 per cent, divided by 39 per cent x 1,000 = 38.5 grams) per cow per day to meet these basic sodium requirements.
As a beef nutritionist, I believe that beef cattle usually need much more salt during periods of heightened activity (such as calving or lactation) or under stressful conditions such as heat stress in the summer. So, I feel that the optimum requirement for salt for many cattle is closer to 50 grams per head per day.
Grazing cattle, like people, have been shown to consume more salt than they actually need to cover off these recommendations and for the most part, without serious consequences. That’s because salt (sodium) is not stored to any appreciable amount in the body compared to other essential minerals such as calcium/phosphorus (bones) or copper (liver). Sodium eaten by the cow is instead absorbed into the blood, filtered out by the kidneys (hormone-controlled) and returned to the blood as required by the cow’s tissues. As long as there is a good water source available, this unseen biological process works for the most part when simple white 20-kg salt blocks are placed onto pasture.
I find it interesting that white salt blocks (containing only sodium chloride) are virtually non-existent on the Prairies, yet blue salt blocks (99 per cent sodium chloride, 120 mg/kg cobalt, and 180 mg/kg iodine and ultramarine-blue dye) are the most common block/loose salt for beef cattle on pasture. This dietary salt anomaly goes back nearly a century ago, when cattle nutritionists of the time discovered that cobalt and iodine were virtually non-existent in Prairie grasses. They formulated salt with these essential elements and the practice stuck until today.
In a similar fashion, brown salt blocks fortified with trace-minerals, such as copper, manganese, zinc and selenium are popular with many beef producers, but I am not a fan of this practice. First, they do not contain essential macrominerals such as phosphorus or magnesium, which are often deficient on most of our northern pastures or drought-stricken pastures during the late summer. Nor do they contain vitamins A and E, which are at best diluted in lush pastures or nonexistent in most mature grass.
Instead, I would prefer to provide a well-balanced summer mineral to beef cattle that goes along with feeding block/loose salt on pasture. It would be one that contains essential macrominerals to compliment the nutrient profile of most pastures. It would also contain adequate levels of essential trace minerals (in both inorganic or chelated forms) as well as high levels of vitamins A, D and E.
A friend runs about 300-Angus-cross beef cow herd on mixed legume-grass pasture. He says he believes in providing good mineral-vitamin nutrition, but his cows will not eat significant loose mineral on pasture. In his case, he feeds trace-mineralized salt blocks during the spring and summer on pasture to at least meet some essential trace-mineral requirements. Then he returns to my 2:1 mineral-vitamin feeding program fed at three to four ounces per head per day, once the cows are brought home to drylot in fall and winter.
Regardless of whether beef producers are feeding blue or brown salt blocks (loose salt included), it seems that opinions vary as to the placement of salt blocks on pasture. Some producers provide salt close to water, where other minerals/vitamins are placed. Other producers say that salt should not be placed close to water because it is already an area of high animal traffic, which tends to concentrate animal pressure on certain areas of pasture and salt should be used as a management tool to evenly distribute animal stockings.
As a tie-breaker, I like to see salt fed along with loose mineral-vitamins provided near waterers. I believe salt and water for cattle go hand-in-hand, especially during times of heat stress and drought, which is quite common on the western Prairies. Fortunately, everybody should agree grazing beef cattle need salt. I have yet to meet a beef producer that will not spend the few dollars to feed salt whether in block or loose form to their cattle on pasture. I hope I never will.