Stock lacks Rarely Needed

New Zealand Journal of Agriculture, Volume 74, Issue 1, 15 January 1947, Page 15

Stock lacks Rarely Needed

TOPDRESSING A BETTER REMEDY FOR MINERAL DEFICIENCIES

By

I. J. CUNNINGHAM,

Animal Research Station, Wallaceville.

IN recent years a great deal of emphasis has been placed on the importance of minerals in the fodder of domestic stock. From writings in technical journals and in popular papers the stock farmer has learned that minerals are necessary for proper development of the skeleton, for the formation of digestive juices, for the building of blood and milk, and for many other processes of vital significance to the health and productivity of animals. All that is true. It is also true, and often left unsaid, that there is a limit to animals’ need for mineralsthat when the fodder contains sufficient, the addition of more minerals can achieve no useful purpose. In the widespread use of mineral supplements for cattle and sheep in New Zealand the amount of minerals already supplied in the pasture has been left unconsidered. There has been no pause to determine whether pasture supplies enough; it has been accepted as an article of faith that more minerals MUST be an advantage, and more have been offered in the übiquitous lick box. No pause has been made, even, to calculate whether the mineral supplements offered and eaten increase in any significant way the total minerals eaten in the pasture. ,

IN this article these points are considered in turn: First, the daily amount of minerals required by stock; next, the quantities in the pasture; and, finally, the additional supply provided by the usual mineral supplement. The most common supplement is a phosphatic lick, and it will therefore be most profitable to begin with a study of the virtues of such a supplement to a diet of pasture. Daily Need of Phosphate The daily requirement of phosphate varies with a number of factors. Age has an important influence, as the young growing animal obviously needs relatively more minerals than the adult; pregnancy implies the need of the foetus as well as of the adult; lactation imposes the additional requirement of the minerals contained in the milk. Species, too, has a considerable bearing on requirements. The discussion can be simplified by confining it in the first instance to cattle, and by considering growing animals, adult dry stock, and adult lactating animals separately. The best basis on which to estimate requirements for growth is a comparison with milk, as this foodstuff is specially designed by nature for the very young. Table I, adapted from Orr’s “Minerals in Pastures,” compares the minerals in a normal good pasture with those in milk, the content in each

being calculated for the amount of the foodstuff which supplies the same amount of energy food value—calories. The table shows clearly that good pasture closely approximates milk in its mineral content and that the quantities of minerals and the balance between them are almost identical in the two foods. Pasture is not, of course, expected to replace milk in the very early period of growth, but it is the main source of food when the animal is growing nearer the weaning stage. At that time the requirement for minerals might be expected to alter. Archibald and Bennett in America have studied the amount of phosphoric acid needed for growth in dairy heifers up to the age of 3 years. They found that heifers made normal growth on diets which supplied: In the first year 4.1 grammes of phosphoric acid (P0 8 ) per 1001 b. live weight;

In the second year 3.9 grammes; In the third year 2.8 grammes. (28.4 grammes equal loz.) Calculated as a percentage of the rations fed, to give a ready comparison with pasture composition, these figures represented 0.46, 0.50, and 0.40 per cent, of phosphoric acid (P 0 in the three years.

Cows' Requirements

The requirement of dry adult cattle has been most thoroughly investigated in comprehensive experimental work carried out in South Africa by Theiler and Green. They showed that SO 1 grammes of phosphoric acid daily (about loz.) is sufficient to meet all the needs of a dry cow going through a normal pregnancy. Such a cow would eat at least 201 b. dry weight of fodder daily, and to meet her needs of phosphoric acid the fodder would therefore have to contain 0.33 per cent, of phosphoric acid.

A lactating cow needs extra phosphoric acid, and the quantity secreted in each gallon of milk is 10 grammes. A cow yielding 3 gallons of milk daily would, therefore, require 30 grammes of phosphoric acid for the milk. Adding to that the 30 grammes she would have needed if she were dry, the total requirement for a cow giving 3 gallons of milk a day is 60 grammes (about 20z.) of phosphoric acid. The averagesized New Zealand cow would have to eat 251 b. of dry pasture to obtain the materials to make that milk; 0.53 per, cent, in the food gives her the necessary intake of phosphoric acid. The calculation of 0.33 per cent of phosphoric acid in pasture for a dry pregnant cow and 0.53 per cent, for milk production must be further modified, because not all the phosphoric acid in the food can be absorbed into the body from the digestive tract. At least 75 per cent, of that in green grass is absorbed, so if the figures are increased by one-third they will represent the minimum quantities necessary for dry cows and milking cows. That means that a dry cow should have 0.4 per cent, of phosphoric acid in her fodder and a milking cow 0.7 per cent.

The third line shows the composition of the pasture expressed in the conventional manner as a percentage in dried pasture.

The requirement for phosphoric acid in the diet of cattle can be summarised as follows: For growth and for non-milking, empty, or pregnant cows a pasture containing 0.5 per cent, of phosphoric acid supplies more than enough of this mineral; for high milk production the pasture should contain 9.7 per cent. Supplies from Pasture How far does New Zealand pasture meet these specifications? A few typical figures for phosphoric acid content of pastures, taken from many published by B. C. Aston and his colleagues, are shown in table II below. All these pastures clearly meet the requirements laid down for phosphoric acid for catlte. They are the good pastures of the Dominion, and those on which it is profitable and desirable to carry ’milking cows. Certainly no justification exists for feeding phosphatic supplements to cows on such pastures. The value of mineral supplements can be examined in another way by calculating the quantities of minerals provided by mineral licks and comparing them with the intake from pasture. That has been done in table 111. The composition of the lick has been assumed to be half bone flour and half agricultural salt, and consumption of this lick would be, on an average, soz. a head a week. The pasture has been assumed to contain 0.8 per cent, of phosphoric acid, 1 per cent, of lime, 0.28 per cent, of soda, and 1 per cent, of chloride, which is the approximate composition of a normal good pasture. The daily consumption of pasture has been taken as 251 b. of dry matter.

It is obvious that the contribution made by the lick is insignificant, though the lick used in the example contains as much phosphoric acid as it is feasible to incorporate. Many licks contain much less phosphate. It is evident, too, that good pasture is an adequate source of minerals and that there is no justification for attempting to add more to the ration. Poorer Pastures In New Zealand there are areas, where pasture improvement and pasture quality are limited by low fertility and low available supplies of phosphate in the soil. On such areas the phosphate content of the pastures is below the level of 0.7 per cent, of phosphoric acid needed for milking cows. It. is rare and undesirable for milking cows to be run on such pasture, where the feeding quality would be insufficient to support a profitable level of milk production. Limitation of production in such cases would be caused primarily by the low feeding value of the pastureits low available protein and carbohydrates and its low digestibilityand not by low mineral supplies. The addition of minerals to such a pasture does not increase the amount of protein or of other constituents like carbohydrate which the animal can obtain from the grass. In the past, cases of phosphorusdeficiency disease have been reported in milking cattle on such unimproved lands. ’ The disease occurred in Taranaki and Wairarapa districts, and symptoms were relieved, by feeding bone meal. Only in, such cases, where a deficiency is actually recognised, are mineral supplements justified. Even then, however, treatment by licks is obviously only a tem-

porary expedient and a grossly uneconomic one, as topdressing with superphosphate would increase the phosphate content of the pasture and relieve symptoms of the deficiency, and at the same time greatly improve the carrying capacity and productivity of the area.

There is no necessity to go exhaustively into requirements and supply of other minerals such as lime, magnesia, potash, and chloride, as it can be shown similarly that they are provided in good pasture in quantities adequate for all the needs of even heavily ing cows.

Minerals for Sheep

The question of minerals for sheep is similar to that for cattle, but the requirement is lower because the product harvested is lower in mineral content. The phosphoric acid requirement of a young growing sheep is about 3.5 grammes a day, which would be supplied in good pasture containing 0.5 per cent, of phosphoric acid. The requirement of a ewe producing about 3 pints of milk a day is, 84 grammes daily, which would be provided in good pasture containing 0.6 per cent, of phosphoric acid. These calculations have been made with due regard to the amount of food eaten and to the fact that some of the phosphoric acid in the fodder may not be absorbed into the body from the digestive tract On poorer pastures with lower phosphate content, growth or milk production could not be maintained at the same level as on good pasture. But lack of phosphorus is not the limiting factor; it is the poor quality of the pasture, its low digestibility, and its low content of proteins and carbohydrates. Workers in South Australia have shown that phosphate supplements for sheep run on areas extremely deficient in phosphorus do not cause any improvement in rate of growth or wool production. When parts of the same * area were topdressed with superphosphate, however, the growth of the sheep did improve in direct relationship to the improvement in quality of pasture. The conclusion reached was that there was no justification for the use of phosphatic licks for sheep, even in districts where low soil phosphate and low rainfall produced a herbage very low in phosphate. That ( conclusion is equally valid in New Zealand, where there are no areas as deficient in phosphate as that on which the South Australian workwas done. In table IV the amount of extra minerals supplied to a ewe by a lick is shown, as was done for a cow in table TIT. The same composition of lick and

SIGH

pasture is assumed, and the consumption of lick is taken as 2oz. a week and the pasture consumption as 41b. of dry matter daily.

Arguments for Licks Why is there such strong and widespread adherence to the ‘use of licks? The first reason is probably that farmers can see the mineral matter of a lick and know that when stock eat licks they are eating minerals. It is forgotten that every 1001 b. of pasture dry matter contains at least 61b. of soluble mineral matter, and that therefore a cow would eat in its pasture about . 101 b. of soluble minerals each weekvery much more than the 6oz. she takes as a lick. And even if farmers mix their own licks, the cost is about £l2 10s. a ton—a lot of money to pay for something that is already present in abundance in the daily feed of stock. Other persistent arguments in favour of the use of licks are:— ■ . 1. High-producing stock require the extra minerals. Stock can produce highly only on highly-improved pasture in which the phosphate and lime are adequate. The contribution of the lick in such cases has been shown to be negligible. 2. Soil minerals are steadily depleted by milk production.— lo,ooolb. of milk contains 201 b. of phosphoric acid. Even if that is produced in 1 acre, the phosphoric acid is returned in lcwt. of superphosphate. On i butterfat farms the phosphoric acid is not taken away but is redistributed by grazing pigs. 3. The fact that stock will eat licks indicates that they require them. lt is a common misconception that animals can determine their own food requirements and that, if given free choice, they would select a perfect diet. That view is largely an interpretation of observations that some improperly-fed animals develop a depraved appetite and .will chew stones, sticks, old carcasses, bones, etc. Of all the objects chewed, bones are remembered best by observers, and the fact that they are chewed is taken as an indication of deficiency of bone-forming elements in the diet, and as proof that the animals know this and know that these elements are present in bones. The fact is that animals which develop depraved appetite will chew almost anything, and the object chewed may be wholly unrelated to the deficiency which caused the depraved appetite. A few examples show that animals cannot be relied on to make a correct

selection of diet: During outbreaks of facial eczema sheep will not eat good, safe hay but prefer the young, lush pasture which will cause facial eczema; cattle will eat ragwort until poisoned by it; they will eat many toxic plants, of which ngaio is an example, and be killed by doing so; they will chew old battery plates, or lick paint pots or painted buildings, and die of lead poisoning.

That animals cannot be relied on to recognise deficiency in the diet and how to cure it is shown by the fact that many will not eat easily accessible licks containing cobalt, though they may be afflicted by cobalt deficiency almost to the point of death. 4. Salt in particular is liked by stock and must be essential.—Extra Salt is necessary in some diets which do not contain enough and for animals in hot climates or under conditions of extra heavy work to replace, salt lost in the sweat. As shown in table 111, however, good pasture contains sufficient salt even for heavily-milking cows.

5. Licks are favoured in many overseas Concentrates are frequently employed there and many are abnormal in mineral content. For example, bran contains 2.5 per cent, of phosphoric acid and 0.1, per cent. of lime; obviously extra lime is necessary to give a proper balance.

Cobalt, lodine, and Copper

So far consideration has been confined to the old-fashioned salt-bone flour licks, which may be called nonspecific licks because they are not employed for any specific purpose other than to obtain a general increase in mineral intake. There are in New Zealand certain areas where specific mineral deficiencies occur, and on these areas specific licks are profitably employed in certain circumstances. The only known deficiencies in New Zealand are of cobalt, iodine, and copper.

Cobalt deficiency occurs on pumice areas of the North Island, chiefly those derived from the Taupo and Kaharoa ash showers, but also from the Mairoa shower. In the South Island the deficient areas are the granite soils of Nelson, the pakihi soils, and Morton Mains soils. ,

lodine deficiency occurs in parts of Manawatu, in areas of the Buller Valley (Westland), parts of Marlborough, in river valleys of Southland and Otago, and particularly in the Lakes District of Central Otago.

Copper deficiency occurs on practically all of the peat lands of New Zealand, particularly the areas in the region of Hamilton, the Hauraki

Plains, Te Puke, Whakatane, Hawke’? Bay, Shannon, Lake Ellesmere, anc Southland.

lodised salt licks have been used in New Zealand to control symptoms of iodine deficiency. Such licks are, O’ course, useful only where an iodint deficiency is known to exist. Then appears .to be no alternative to th« use of licks /in such cases, as top dressing with iodides is not practice able.

On cobalt- and copper-deficient areas the provision of regular supplies ci these minerals. to the stock is essen - tial to maintain them in health. Th* best method is to increase the mineracontent of. the pasture by applicatioi of cobalt or of copper in topdressing.. That is satisfactorily accomplished b? annual topdressing with soz. of cob alsulphate or 51b. of copper sulphate an acre where appropriated

: ' Most of the ! cobalt-deficient area?’ must bp topdressed with superphos - phate to obtain an economic produc - tion of pasture. Cobalt sulphate is in corporated in superphosphate at fertiliser works, and the mixture can be applied for the same expenditure of labour as an application of superphosphate alone. Where cobaltised superphosphate is used annually m deficiency of cobalt exists.

Similarly, copperised superphosphate can now be bought and it is the mos satisfactory method of controlling copper deficiency on areas which re quire superphosphate. However, som< of the peat land does not require super phosphate, and in such cases topdress ing does involve extra labour in mix ing copper sulphate with lime before spreading it or in distributing coppei sulphate alone.

Where the topography of the country is unsuited to topdressing or where its present carrying capacity or potentialities for development do not warrant the

expenditure of topdressing, licks provide the next method of choice. But even oh rough and inaccessible country aerial , topdressing may be the solution.. A successful experiment has already been carried out with copper sulphate, and experiments with cobalt are projected.

Disadvantages of Licks

Licks can be regarded as definite!* a second choice to topdressing, but on* which must be taken in certain cir - cumstances. They have certain .disadvantages:—

1. Lick consumption is uneven in *. flock or herd, so the correct quantity of the requisite mineral cannot b«guaranteed each animal. Some do no s take licks at all and some may taketoo much. , Particular care must

exercised in employing copper-con-taining licks for sheep. If the copper content is too high, poisoning can result; poisoning is possible if sheep have access to licks which contain the necessary amount of copper to be effective for cattle. 2. Regular care and considerable expenditure of labour are necessary to ensure that lick boxes are kept full. 3. Weathering causes loss of important ingredients, notably iodine. 4. Expense is higher than is generally believed. Copper sulphate for topdressing 2 acres, each with 51b., costs 3s. 4d. If that area carried only 1 cow, the necessary amount of lick for a year would cost: Home-mixed agricultural salt only -j- copper sulphate .. Is. Bd. Home-mixed bone flour -j--agricultural salt -f- copper sulphate 2s. 3d. Commercial lick at £3O a ton ss. 4d. If the area carried 1 cow to the acre, .as some peat lands do, the costs for lick would be doubled. Labour of providing the lick throughout the year

is at least as great as for topdressing once. Similar considerations apply to cobalt. 5. The provision of licks does not improve the environment of the plant, in contrast to the effect of topdressing. That is not important for cobalt, as plants seem to have exceedingly low requirements, but it is important' for copper, a deficiency of which may seriously hamper the growth and persistency of good pasture species. 6. No advantage can be expected from feeding minerals already adequately supplied in the ration, so a special lick is necessary for each deficiency. The expense of employing a shotgun type of lick which includes all minerals ever reported to be deficient can on no grounds be justified for general use. Summary The mineral needs of farm stock in New Zealand can be more satisfactorily provided by suitable methods of topdressing then by feeding mineral supplements, except in the case of iodine deficiency.

, “Improved” pasture topdressed with superphosphate and lime supplies adequate quantities of phosphate, lime, and salt, and there is no necessity to provide licks containing these minerals, even for milking cows. Unimproved pasture is a poorer source of these minerals, but its limitations as a source of nutrition are primarily caused by the lower content of available organic nutrients, and not by the lower content of minerals. Other major minerals, such as potassium and magnesium, are not discussed, as pasture provides these in ample amounts. Known areas in New Zealand are naturally deficient in some trace minerals, the proved deficiencies being cobalt, iodine, and copper. Cobalt and copper can be most satisfactorily supplied by appropriately topdressing the pastures. If that cannot be done, mineral ’ licks may be employed to supply the missing element. Where it is needed, iodine must be supplied in licks.

Lime (CaO) Phosphoric Acid (P 2 Soda (Na 2 0) Potash (K 2 0) Chloride (Cl) Protein Cow's milk .. 2.38 3.43 0.81 3.21 1.4 52.0 Pasture 3.64 2.75 P-94 • 11.54 3.5 65.0 Pasture % .. 0.98 0.75 0.25 3.1 0.94 17.5

TABLE I Comparison of Milk and Pasture: Minerals per 1000 Calories.

Species of Pasture Origin Manurial treatment Percentage P 2 0 3 in Dried Pasture Red Clover .. Rotorua Unmanured 0.75 White Clover Rotorua Unmanured 0 80 Cocksfoot Rotorua Superphosphate 0.87 Mixed .. Wairoa Superphosphate and lime 1.12 Mixed Canterbury Probably superphosphate 0.94 Mixed Waikato Probably superphosphate 0.77 to 1.45 Mixed .. Poverty Bay Probably superphosphate 0.67 to 1.13

TABLE II Phosphoric Acid in a Random Selection of New Zealand Pastures.

From 6oz. of Lick (grammes) From 1751b. of Pasture (grammes) Required for a 3gallon cow (grammes) Phosphoric acid (P 2 0 5 ) 19 633 420 Lime (CaO) 26 791 224 Chloride (Cl) 122 51 791 122 Sodium (Na) 70 Chloride (Cl) 51 791 Sodium (Na) 34 34 198 198 70

TABLE III Weekly Intake of Minerals Obtained by a Milking Cow from Lick and Pasture.

From 2oz. Lick (grammes) From 28ib. Pasture .(grammes) Phosphoric Acid (P 2 0 5 6 101 Lime (CaO) .. 9 ' 127 Chloride (Cl) .. .. 17 127 Sodium (Na) .. 11 32

TABLE IV Weekly Intake of Minerals Obtained by a Ewe from Lick and Pasture.