Notes for the Poultry Farmer

New Zealand Journal of Agriculture, Volume 64, Issue 4, 15 April 1942, Page 279

Notes for the Poultry Farmer

The Theory and Practice of Poultry Feeding

By

F. C. BOBBY.

Superintendent of Poultry Husbandry, ... ... , 7 Wellington.

(Continued from the March issue.)

IN the March issue of the “Journal” food essentials or food ingredients, such as proteins, carbohydrates, etc., were described in detail. This information may now be used to assess the relative values of poultry foods and their suitability for blending together into mashes for feeding to birds of all - ages. It 'is a common practice to set out in a “Food Composition” table the amount of food ingredients of any given poultry food, these amounts being expressed in percentage form. It will also be observed when studying “Food Composition” tables that two sets of percentage figures are quoted, namely (a) Total per cent, of food ingredients. (b) Per cent, digestible food ingredients. This requires an explanation, although it is obvious what is intended by total food ingredients. Of these, total food ingredients, however, it has been found by scientific ( investigation that only a proportion are digested by animals or poultry. The amount digested varies with individual foodstuffs and with different classes of livestock. Speaking generally, the figures given, in tables for digestible food, ingredients have been obtained with heavy farm stock and not with poultry. Nevertheless, those figures are useful to poultrykeepers, although admittedly not entirely accurate for birds. That portion of any food ingredient which is not digestible (the difference between the total per cent, and the digestible per cent, figures) is passed out of a bird’s or animal’s body as a waste product. For this reason, it. is usual to take the “digestible figures” when making calculations for assessing the value of a poultry food or ration. The following, analyses of pollard and wheatmeal will illustrate the point made above:—

The difference between the total per cent, and digestible per cent, of the food ingredients in the two examples quoted is not great, but wider differences are found, particularly in the instance of meat-meals, where a 72 per cent, total protein gives only a 64 per cent, digestible protein. A brief study of the figures for pollard and wheatmeal reveals the fact that the latter contains appreciably more carbohydrates than the former, a point to be considered when substituting wheatmeal in place of pollard. Wheat-meal may fatten where pollard will not, especially in the instance of breeding hens. A further point to bear in mind is that these figures refer to an average sample of any given food, whereas

there will be some variations in composition between different consignments purchased from time to time. In point of fact, however, average figures of composition are valuable, and should be understood by the modern poultrykeeper. Obviously, poultrykeepers will not wish to memorise the compositions of the poultry foods in common use, and for this reason a table is now included to which reference may be made at any time. ' It will be observed that in addition to the per cent, of digestible food ingredients there are a further two sets of figures. Those in brackets a'djacent to the digestible fibre represent the total crude fibre, while a fifth column has been included, the per cent, of ash or minerals. The figures for total fibre-content are valuable information, as it is known that fibre cannot be readily digested by poultry, and when in excess may actually be harmful.

Thus, where there is a high fibrecontent, the feeding value of a food is lowered for poultry. This is the reason for stating that a poor sample of oats (that is, a high proportion of husk to groat or grain) "has a poor feeding value for birds and is consequently an uneconomical food to feed. Figures for mineral-content have been included, as they act as guide when determining how much additional mineral mixture should be added to any given combination of meals when blending a mash. . Note the difference in mineralcontent between meals such as wheatmeal - (ground wheat), maize-meal (ground maize), bran, and lucernemeal. It will be noted that no reference is made to the vitamin-content of these foods, but it will be recollected that vitamins are existent in such minute quantities that it is impossible to measure them by ordinary standards. The next step is to consider what points are of importance when compounding a mash and how the food analysis table can be used. Points of importance may be enumerated as follows: — (1) The proportion (or ratio) of protein to carbohydrates and oil present in a ration. (2) The mineral and vitamin-content according to the class of stock to be fed.

(3) The physical condition of a mash its bulkiness. ■ _ (4) Palatability. (5) Cost. ■ . It may be stated here that (5) cost cannot be discussed under present conditions, as prices and supplies available of the various foods vary according to district. For obvious reasons, price has to be considered by the poultrykeeper, but it is as well to remember that the cheapest foods to- buy may not necessarily be the most economical to use. This fact is too often overlooked, and must be discussed in greater detail later. (1) Ratio of Protein to Carbohydrates and Oils The ratio of protein to carbohydrates and fats is usually referred to as the “Nutritive Ratio,” and serves as a rough check upon the suitability of a mash for poultry. It has been used as such for a number of years by poultrykeepers, who commonly refer to it as obtaining “a balanced ration or mash” that is, a desirable balance between the protein present and the other essential food ingredients. Quite definitely, however, the “Nutritive Ratio” affords only a rough check, as today science has made it possible to ascertain the actual amount of digestible protein required by a bird, having

regard to its age, weight, and rate of production, if in lay. This introduces far more complicated methods of calculating the efficiency of a mash, and, although more accurate, these methods are beyond the scope of these particular articles. Most poultrykeepers realise that there is a definite limit to which protein may be added to a mash with safety, but many do not realise that if the starchy ingredients (carbohydrates) are allowed to get out of proportion, excess fat may be the result. A knowledge of the ratio between the proteins and the carbohydrates and fats is therefore of interest and value. The method or formula for obtaining this ratio is expressed as follows: — Nutritive Ratio = (Digestible fat X 2-1) + (digestible carbohydrates) Digestible ■ protein The following is a simple explanation of the above: — (a) Take the figure for fat from the analysis table and multiply it by 2| or 2.25. Fat digested by a bird will produce two and a quarter times as much heat and energy as carbohydrates (starch), and thus in the calculation above the figure for fat is multiplied by 2.25 to bring both figures to a common basis (that is, fats and carbohydrates).

(b) To fat multiplied by 2.25 add the figure for carbohydrates. For animals, it is usual to add also the figure for digestible fibre, but for poultry. this is hardly advisable, as birds are not able to digest fibre to any appreciable extent. (c) Having obtained the sum total of the fat and carbohydrates, divide this figure by the amount of digestible protein, working to the first decimal place. Note: The per cent, figures in the analysis table represent the weight of, say, protein in 100 units (pounds) of the food in question. To find the amount of protein in a food in a mash, divide the table figure by 100 and multiply by the number of pounds of that food. A study of the following example will show how a Nutritive Ratio is obtained: —

Protein. Oil. Carbohydrates. Pollard 36 lb (36 X .13) = 4.68 (36 X .035) = 1.26 (36 X .48) = 17.28 Bran 12 lb■ (12 X .11) 1.32 (12 X .032) = .38 (12 X .40) = 4.8 Meat-meal 4lb (4 X .11) = 1.68 (4 X .105) = .42 Minerals , 2lb .... 54 lb. ' 7.68 2.06 22.08

Thus N.R. = (2.06 X 2.25) + 22.08 7.68 = 4.68 + 22.08 7.68 = 3.4

Therefore, the Nutritive Ratio is said to be 1 to 3.4, or 1 part protein to 3.4 parts carbohydrates and fat. Now, for laying birds the ratio should be between 1 to 4 and 1 to 4|, thus indicating that this mash is too rich in protein. However, the mash would be fed with an equal amount of grain daily, and this must be taken into consideration. Mash 54 lb. ' 7.68 Wheat 54 Ib. .. (54 X .095) = 5.3 108 lb. • , 12.81 .Thus Nutritive Ratio == (2.7 X 2.25) + 56.37 12.81 = 4.8 or 1 to 4.8 The ratio is now much wider, and is, in fact, a little too wide, meaning that the mash could have a further J lb. of meat-meal added to it with advantage. This can be demonstrated another way. The complete ration of 108 lb. contains 12.81 lb. of digestible protein, giving a percentage of approximately lit digestible protein, whereas a laying mash should contain between 14 per cent, and 15 per cent, digestible protein. It is of interest to note that the mash selected is the one so commonly used in the Dominion, namely, 2 parts pollard, 1 part bran, and Taper cent, meat-meal. Poultrykeepers who are not inclined to make use of the formula described are reminded that the Department is prepared to check their poultry rations for them. It is essential, however, that the amounts of meals used in their mash and the grain fed should be supplied in terms of “by weight, in pounds,” and not by measure.

(2 Mineral and Vitamin-content It has already been stated that poultrykeepers are concerned only with vitamin A and vitamin D rich foods, and these only under certain conditions. Further reference to these vitamins will be made under Part 3. Good quality poultry foods contain a sufficient supply of all other vitamins necessary to poultry. As they are present in such minute quantities, no calculations are necessary or possible when compounding a ration. It is customary today to add 2 per cent, of a mineral mixture to the average laying mash, and this, together with the minerals in the meals and grain, normally supplies the bird with an amount in excess of the total requirements. This small excess is not

harmful to the bird, and is a safeguard against any shortage when a bird is in heavy production. Once again it may be stated that complicated mineral mixtures containing a multitude of different mineral ingredients are unnecessary for healthy birds receiving a normal mash mixture of good quality food. (3) Bulk and Poultry Mashes For the purpose of these articles, the bulk of a poultry food or mash can be 2.06 22.08 (54 X .012) = .64 (54 X .635) = 34.29 2.70 ' 56.37 referred to only in a general manner. Although fully appreciated by the dairy and pig farmer, it is not given sufficient consideration on the average by poultrykeepers. It is obvious that there is a limit to the bulk of food which a bird can contain or eat. Thus, if a laying mash is unduly coarse or bulky, the bird may apparently eat its fill, but the actual weight of a food ingredient consumed (that is, such as protein) may be well below what is required for egg production. On the other hand, a very fine mash may easily cause trouble, particularly with young chickens fed on dry mash, when the fine starchy meals will often clog on their beaks. Furthermore, a fine, dusty, dry mash may affect birds by getting into their breathing organs and causing irritation. For those interested and who/have a 100 cubic centimetres glass measuring cylinder, any laying mash of which 1 oz. measures more than 70 cubic centimetres when shaken down in the cylinder is too bulky for high egg production. This is assuming that the

mash is properly balanced for food ingredients in the first place. Soaked wheat feeding is a further excellent example where . the bulk is greatly increased by water and the actual consumption of dry wheat by weight reduced. For this reason, care should ■be taken when using this system of feeding to see that the birds are consuming sufficient to maintain body weight. If not, then additional dry corn should be given. (4) Palatability It is assumed after close observation that poultry have only a very limited sense of smell and tastethe two senses normally associated with determining the palatability of food. Although this is the case, it is also recognised that birds have definite likes and dislikes as far as feeding is concerned, and in this connection the senses of sight and touch play a definite part. Any mash which may cause discomfort will be neglected or refused" IBIIBIIBIIB!IBIIBIIBIIBIIBIIB1IBIIBIIBI1BIIBIIBIIBIIBIIBIIBIIBIIBIIBIIBIIBIIE

■iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiniuiiiiiiiiiiiiiiiiti in time. As an illustration of this, a badly-made wet mash which is “tacky” or “sticky” may be cited. Furthermore, the presence of an excess of irritating fibre, such as may be met with in some lucerne-meals, will appreciably lower the palatability of a mash. In practice, the only sure way of judging the palatability of a mash is by trial with careful observation. . A detailed description of the theory of feeding has now been completed. The next article, which will appear in the May issue of the “Journal, deals with the practical issues of feeding, •and will include a discussion on systems of feeding as well as typical present-day rations for all classes of poultry.

Cost of Producing a Dozen Market Eggs. ■ 1 ADETAILED report upon the cost of production of market eggs during the season 1940-41 has now been prepared by the Senior Investigational Officer, Department of Agriculture. For reasons connected with the present shortage of paper, this report has not been published in the “Journal,” but the report will apear in full in the March issue of the “New Zealand Poultry World.” Readers are therefore strongly urged to obtain a copy of the “ N.Z. Poultry World” for March, as this report is of particular interest and value to all poultrykeepers. Copies may be obtained from the Secretary, N.Z. Poultry Board, A.M.P. Buildings, Wellington, price 9d., post free, or 7/6 post free for an annual subscription. • ' '

TOTAL INGREDIENTS. (Protein ■Soluble Oil Fibre , Pollard. .. . . 16% carbohydrates 56% ... '■ . . 44% • • : • • 6 % .. Wheat-meal. 12% 69% 2% 2% ; DIGESTIBLE INGREDIENTS. .1 Pollard. Pollard. Wheat-meal. Wheat-meal. .Protein . . 13% 94% (Soluble carbohydrates 50% ■ 65 % (including (including :L„ fibre) fibre) fibre) fibre) Oil . r .. 34% 14%

T . .. , Protein. Per Cent. Digestible Pood Ingredients. Ash. Oil. Carbohydrates. -Pibre. . .. Wheat dr wheat-meal Protein. .. 9.5 Per Cent. Digestible Pood Ingredients. Ash. 1’25 1.75 Oil. 1.25 63.5 ‘ Carbohydrates. 63.5 1.0 (2) Pibre. 1.0 1.75 (2) Maize or maize-meal 7.5 2.75 63.75 0.75 . (2) (2) 1.25 1.25 Barley or barley-meal .. 7.25 1.25 . 61.0 2.5 (4.5) (4.5) 2.5 2.5 Oats or ground oats 7.5 4.0 45.0 . 2.5 (10.0) (10.0) 3.0 3.0 Pollard . . . . . . . . 13.0 3.5 48.0 2.0 (6.0) (6.0) 3.75 3.75 Bran . . . . . . 11.75 3.25 40.75 3.5 (9.5) (9.5) 5.75 5.75 ‘Lucerne-meal . . . . ■ . . 15.5 • — ' 31.5 8.0 . (16.0) > (16.0) 11.0 11.0 Meat-meal (60% protein) . . 42.0 10.5 — • ——— ■ 19.0 19.0 Copra-meal . . . . . . 17.0 5.0 30.0 4.0 (6.5) (6.5) 5.0 5.0 Dried skim-milk . . . . 31.0 j 0.25 49.0 — 8.0

COMPOSITION OF POULTRY FOODS.