COMMERCIAL VALUE OF FEEDS

Press, Volume CX, Issue 32209, 30 January 1970, Page 10

COMMERCIAL VALUE OF FEEDS

“There is a little good in all things bad,” we are told and the prolonged drought in Canterbury .and North Otago is no exception.

One of the encouraging featured to emerge out of this most discouraging climate is that, because more farmers have been buying in more feed and expensive feed at that, there has been increased interest shown in the use of feed evaluation systems as an aid in deciding which feed is the “best buy." Farmers are asking: “How can I tell if I should buy oats at 80c a bushel or barley at 95c? Is fodder beet worth buying at $l2 per ton, if hay is $1 a bale?” There is a great deal- of confusion about feed evaluation systenis and how they can be used, so much so that most farmers give up in disgust and rely on their intuition. This is a poor state of affairs in these days of more precise farming practices. There is no reason why everybody should not be quite proficient in the manipulation of these simple figures. Many farmers could have saved considerable money if they used them. Now that the time of year when most feed is being bought and sold is fast approaching, this confusion should be cleared up. One of the main reasons for the misunderstanding about feed evaluation systems is the fact that there are numerous systems available, some old, some new, some simple, some complicated, and some more accurate than others. The one which has in the past been given the most emphasis in New Zealand is the starch equivalent system (S.E.), which is the old British system. This is now rather out of favour, certainly in academic circles both in New Zealand and Britain, mainly because it is a rather difficult concept to fully understand. There are also a number of feed evaluation schemes based on calories (as used in human dietetics), but these are rather more sophisticated than required by the man wanting to know if he should buy ryegrass straw or meadow hay. The system which is simplest to understand and which suits New Zealand because it is fairly accurate for feeds fed mainly to maintain animals is the D.O.M. system (the abbreviation for digestible organic matter). Although digestible organic matter may at first seem a bit of a mouthful, basically it is very simple. Any foodstuff can be broken into two portions: (a) the part which is digested and absorbed by the animal, and (b) the remainder, the waste, which passes through the animal and is of no food value. The useful portion is what is termed the D.0.M., e.g. Feed equals D.O.M. plus faeces. The D.O.M. value for each feed given in the table is the amount of useful food (D.0.M.) contained in 1001 b of the food. From the table.

r*r**+t**a*r+maar**++*r*i the D.O.M. value of wheat is 80. This means if an animal eats 1001 b of wheat it will obtain 801 b of D.O.M. which it can use for various purposes such as maintaining itself, producing milk or growing. The basis for the comparison of foodstuffs is, therefore, how they compare in providing D.O.M. Because D.O.M. values relate to the fresh weight of the food there is no need to even know the dry matter of the food, the D.O.M. value is all bat is required. It is simple now to work out some examples. Example I Question: should I buy oats at 70c a bushel (401 b or barley at 95c a bushel (501 b Answer: 401 b oats would cost 70c. Therefore 1001 b oats would cost $1.75. From the table, oats contain 601 b of D.0.M., so 11b D.O.M. as oats would cost 2.9 c. In the same way 501 b of barley would cost 95c, so 1001 b would cost $1.90. As 1001 b of barley contains 721 b of D.O.M. (again from the table), 11b of D.O.M. as barley would cost 2.6 c, so as lib D.O.M. would cost less as barley than as oats,' I am better to buy barley. Example 2 Question: Is fodder beet worth buying at $l2 a ton if hay costs $1 a bale (601 b Answer: 1001 b of hay would cost $1.66. This is equivalent to 471 b D.0.M., again using the table, and 11b D.O.M. as hay would cost

3.6 c. 1001 b fodder beet would cost 54c and as, from the table, this is equivalent to 121 b D.0.M., 11b D.O.M. as fodder beet would cost 4.5 c. So fodder beet Is too expensive at $l2 per ton. It is possible to work out in this way that if hay is worth $1 a bale fodder beet is only a good buy at less than $9.60 per ton.

Example 3 Question: 1 have been offered $lOO an acre for a crop of swedes yielding 25 tons an acre. Should I accept if the ruling price for hay is 90c per bale? Answer: As 601 b of medium hay is worth 90c 1001 b is worth $1.50. This is equal to 471 b D.0.M., so 1001 b D.O.M. as hay costs $3.19. At $4 a ton 1001 b of swedes is worth 18c, and as this is the equivalent of 91b D.0.M., 1001 b D.0.M., as swedes is worth $2, which is much lower than the $3.19 for 1001 b D.O.M. of hay, so I will not accept the offer. From this it can be calculated that the swedes should be worth about $l6O an acre.

There are numerous examples which could be given to show how these figures can be used to your advantage. The only requirements really are a table of D.O.M. values, a grasp of standard three arithmetic and a few minutes to work it out. To make the job even more simple, column two in the table gives the value of each feed compared to lib barley, so lib barley is equivalent to 61b fodder beet, or 1.71 b poor hay.

You will notice that no mention has yet been made of column three in the table, the digestible crude protein. This is for a good reason: almost all supplementary feeding is to animals which are little more than maintaining their liveweight and at this feeding level the protein content of

the feed is of little consequence.

Only if the entire ration is of the poor-straw type is protein likely to be limiting. These figures are given simply to show that some allowance can be made for the high protein values. For example, you would expect to pay more for average lucerne hay than good meadow hay. even though their D.O.M. values are the same, because of the high protein content of the lucerne hay. Similarly, peas are worth more than wheat because of this. Unless the supplementary feed is for late pregnancy or for young growing stock then protein content is not usually critical and the D.O.M. values are the most important. It must be remembered that the values given to feeds in any feed evaluation system are only a guide to eliminate total guesswork. Nobody is suggesting that every rape crop will have a D.O.M. value of 12 or that barley straw will have a standard D.O.M. of 40. The precise values will depend on the time of year, weathering of the material, deterioration in storage, etc. If you feel sufficiently confident you can of course, make simple adjustments of one or two units to the D.O.M. values to allow for these various modifying factors. This is unimportant. The significant point is that the D.O.M. system is relatively simple to use, and if you use it you can be in a much stronger position in regards to buying feeds at the right price. Feed evaluation is, of course, useful for other purposes but these need not be mentioned here. It is hoped that you will now be able to make more enlightened purchases of your feed supplies and even be less disgusted at the mention of feed evaluation which has too often been stated as the responsibility of “those college men.”

The author of the accompanying article on the evaluation of feed and its use in the purchase of feedstuffs is Mr A. M. Nicol, of the animal science depart- * ment at Lincoln College.