The opening years of the twentieth century have witnessed a tremendous advance in the science of nutrition, due in large measure to the discovery of vitamins and their role in the normal life processes. In the field of poultry nutrition, probably the most important event of period has been the discovery that the feeding of cod liver oil would make possible the rearing of chicks in confinement – a contribution which immediately opened up unlimited possibilities, both to the poultry keeper and tot the student of nutrition. Following close on this discovery came the development of the “all-mash” system of feeding, which is now adopted as standard practice, not only for chicks but in many cases for growing pullets and for laying hens. By means of all-mash feeding the poultry keeper can cut his labor costs, improve sanitation, and control feed consumption, while the research worker is enabled to conduct more careful studies with chicks under laboratory conditions.
With the introduction of satisfactory methods of rearing chicks indoors, there has come about a marked change in general feeding management, which threatens to revolutionize the entire poultry industry. Commercial plants are now raising their chicks in large units, closely confined in electrically heated brooders, built like apartment hotels – a system which involves a minimum of floor space, a minimum of labor and better control over the factors which contribute to the welfare of the flock. Many poultry plants also are expanding upwards instead of outwards, and laying-houses may tower to six stories in height, the birds being confined without access to yards throughout their whole life. A still further development of the confinement system of management is to be found in the new method of housing adult birds in “laying batteries” where hundreds may be cared for in a relatively small space, each hen being confined in an individual cage. Trap-nests are done away with, cleaning becomes automatic, and each bird can be observed and her record checked, with the utmost ease and accuracy. Results of such methods show that with good sanitation, careful management and a satisfactory ration, egg production goes up, mortality goes down, vigor and health are maintained and feed costs are reduced.
In the days when poultry keeping was entirely a farmyard proposition, when feeding was based principally on tradition and expediency, and when a touching faith in nature was the keynote of the system, such things as free range, open air, exercise and dust baths were considered the all-important essentials. Some of these, of course, are still highly valuable assets, provided they are not accompanied by soil contamination and other danger, but for modern commercial “egg factories” they prove to be cumbersome, expensive and risky, and are thus being replaced largely by the various artificial substitutes which science has devised. “Natural methods” served admirably for small flocks which were not exposed to the strain of heavy production and the hazards of contagious disease and parasites, but for commercial flocks of today, which must make a profit in the face of strong competition and low prices, factory methods have to be adopted and business principles applied, so as to maintain efficiency and cut production costs.
In the realm of research in poultry nutrition, there have also been dramatic changes since confinement rearing has ben introduced and feeding methods have been simplified. Electrically heated battery brooders make possible the rearing of large numbers of chicks in the laboratory, where heat, light moisture and ventilation are under control; where feed intake can be measured and growth rates recorded; where strictest sanitation can be observed and contagious disease eliminated; and where every pen can be kept under close and continuous observation.
Since these methods of scientific study have been adopted, a great deal of work has been done on the nutritional requirements of poultry in the various stages of their life, in an attempt to solve the many questions which mean so much in the efficient management of a flock. What, for instance, is the best amount of protein to feed at different stages of growth and production? What amounts of mineral should be fed to chicks, to pullets and to layers, in what ratio should they be included and from what sources should they be taken? What are the requirements of the chick and of the hen for the various vitamins, and what feeds supply these in greatest abundance, and with the greatest economy and convenience in feeding? These are similar questions from a large part of the research program in poultry nutrition and the answers as they are found are quickly translated to practical condition, so that reliable feeding standards may eventually be established.
Another phase of the work, which has received a good deal of attention, is the effect of nutrition on the quality of the product, e.g., on the strength of the egg-shell, the colour of the yolk, the consistency of the albumen and the food value of the egg. For instance, the quality as well as the quantity of protein fed to laying hens has been shown to have a definite effect on the amount of protein in the egg, but little or no influence on the chemical composition of the egg proteins. The vitamin content of the feed, however, is definitely reflected in the product, and has a strong influence on the strength and vitality of the embryo. Such foodstuffs as mild, cod liver oil and alfalfa, have been shown to be highly efficient in improving hatchability, and are now recommended as important elements in rations for the breeding flock.
Another feature of recent investigational work in poultry nutrition has been the study of the relation of diet to disease. Many ills, such as various types of leg weakness in chicks, crooked breastbones, some forms of paralysis and some types of respiratory diseases, can now be traced to defects or deficiencies in the ration. Furthermore, it is becoming more and more evident that while active disease does exact a heavy tool of our flocks, the most serious losses are traceable ultimately to low efficiency from malnutrition. Poor nutrition over an extended period may be responsible for retarded growth, and low vitality, and as a consequence, for low production ill-health and low hatchability of the eggs. It may also produce alterations in the chemical composition of the blood and other body fluids, which will lead to a lowering of the defense mechanism against bacterial invasion. Recently there has been submitted some evidence that nutrition may have an effect on immunity, that is, on the power of the antibodies and the white blood cells to combat disease organism. If this should prove to be the case, the composition of thee diet will become an even more important factor in good management that it is conserved today.
Discoveries in the field of nutrition are thus materially affecting the trend of poultry keeping, which is now definitely towards larger flock units, confined to small areas where close control is possible and production costs can be reduced. Emphasis, however, is laid on the importance of sanitation and on complete balance in the ration, to compensate for the natural agencies, which cannot be utilized. The poultry man himself must also advance with the times. He must not only become familiar with the fundamental considerations involved in the practice recommended and keep up-to-date with the newest and best that science has to offer, but he must adopt sound business policies in the management of his enterprise. Only by such means will he be enabled to avoid the pitfalls and embarrassment, which surrounded the industry at the present time, and to maintain the high efficiency which is essential to any profitable undertaking.