The nutrition of farm animals

Front matter

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Preface

The manner in which the subject of the nutrition of farm animals is presented to the student will naturally differ according to the ultimate end in view. If the prime purpose is to impart practical skill in the feeding of live stock, the study of the principles of nutrition is likely to be regarded as preliminary and to partake of the nature of an information course, and chief stress will be laid upon familiarity with the results of experience, particularly as related to the business aspects of the subject, and to the acquisition of practical skill.

But while by no means disposed to minimize the significance of this aspect of the subject, the writer is nevertheless convinced that for the students of our agricultural colleges a somewhat different procedure is desirable. He believes that greater emphasis than they sometimes receive may wisely be laid upon the chemical and physiological laws which underlie the practice of feeding, both on account of their intrinsic importance and because the subject may thus be made a real collegiate discipline which shall contribute to the training as well as to the information of the student.

Accordingly, the present volume attempts to deal primarily with the natural laws governing the nutrition of farm animals, as distinguished from the broader field of animal husbandry, and only secondarily with the specific details of practice. It seeks to avoid so far as may be mere dogmatic statements, and, although not attempting complete citation of literature even upon important points, to present the experimental evidence with sufficient fullness to indicate something of the limitations of present knowledge and of trie* opportunities for further investigation. Its aim is to discuss the fundamental principles upon which successful stock feeding is consciously or unconsciously based in the firm persuasion of the truth so pithily expressed almost half a century ago by the father of agricultural science in the United States, Professor Samuel William

V i PREFACE

Johnson, that, "Other qualifications being equal, the more advanced and complete the theory of which the farmer is the master, the more successful must be his farming. The more he knows, the more he can do. The more deeply, comprehensively, and clearly he can think, the more economically and advantageously can he work," and that "A true theory is the surest guide to a successful practice."

In short, the book is intended for the student rather than directly for the farmer and assumes a certain degree of preliminary training on the part of the reader, including an elementary knowledge of chemistry and physics.

The author is under obligations to The Honorable Secretary of Agriculture, for permission to reproduce, in Chapter XVIII, a part of Bulletin No. 459 of the United States Department of Agriculture ; to the Macmillan Company for the similar use in Chapter XV of material from Bailey's " Cyclopedia of American Agriculture"; and to Messrs. Henry and Morrison for permission to base the tables of the net energy values of feeding stuffs contained in the Appendix upon their extensive compilations in the fifteenth edition of " Feeds and Feeding." He is likewise indebted to the following publishers for the use of the cuts named :

The Carnegie Institution of Washington, Figure 24.

The F. A. Davis Company, Figure 17.

The W. B. Saunders Company, Figures 1,5, and 14.

State College, Pa., May, 191 7.

CHAPTER II The Composition of Animals and of Feeding Stuffs

§ 1. The cell

§ 2. Animal tissues and organs

§ 3. The composition of the animal as a whole . § 4. The composition of feeding stuffs .

3 7 16 24 36 39

42 42

45 61 66

Chapter V

§ 1. General conception § 2. Enzyms as agents in metabolism . § 3. The metabolism of the carbohydrates § 4. The metabolism of the simple proteins § 5. The metabolism of the nucleoproteins § 6. The metabolism of the fats . § 7. Metabolism of ash ingredients § 8. Functions of the nutrients

144 144 148

152 160 168 171 178 182

Chapter VI

The Balance of Nutrition . § 1. General conception § 2. Methods of investigation § 3. The balance of matter . § 4. The balance of energy . § 5. Significance of results .

192 192 194 202 216 241

Chapter VII

§ 1. The protein katabolism in fasting

§2.

§3-

The energy katabolism in fasting .

Conditions affecting the fasting katabolism

251 256

CONTENTS ix

Chapter VIII Page

§ 1. Net energy values for maintenance 271

§ 2. Maintenance requirements of farm animals . . . .280 § 3. Factors affecting the maintenance requirement . . . 304 § 4. The relation of the maintenance requirement to external

temperature 308

Chapter XIII

§ 1. The physiology of milk production

§ 2. The animal as a factor in milk production .

§ 3. The influence of environment on milk production

§ 4. The utilization of feed in milk production

§5. Feeding. for milk production .

424 424 428 444

459 459

478 488 500

X CONTENTS

Chapter XVIII 630 630

634 667 678

§ 1. Feeding standards 689

§ 2. Feed requirements 691

§ 3. Method of computation 697

CONTENTS

XI

Estimated Protein and Energy Requirements of Farm Animals

Table I.

Table II.

Table III.

Table IV.

Table V.

Table VI.

Maintenance requirements of cattle and horses, per day and head

Maintenance requirements of sheep and swine, per day and head

Requirements for fattening with no considerable growth — all species — in addition to the maintenance requirement ....

Requirements for growth with no considerable fattening

Requirements for milk production ....

Requirements for work production by the horse

Average Dry Matter, Digestible Protein and Net Energy Values of Feeding Stuffs per ioo Pounds

Table VII. Values per ioo pounds for ruminants Table VIII. Values per ioo pounds for the horse Table IX. Values per ioo pounds for swine .... Table X. Mineral elements of feeding stuffs — per ioo pounds of dry substance

PAGE

711 711

REFERENCES

The full-face numbers in parenthesis in the body of the text refer to the numbered paragraphs and not to pages.

ILLUSTRATIONS

FIG.

i. Different types of cells composing the body

2. One end of a muscle fiber .

3. Part of a muscle fiber . . . . .

4. Fat cells in muscles ......

5. Scheme of a fat cell

6-8. Successive stages in the formation of adipose tissue

9. Sheep's stomach '

10. Stomach and duodenum of horse ....

11. Stomach of hog .......

12. Intestines of cattle

13. Ccecum of horse . . . . .

14. Section of villi

15. Steer in digestion stall

16. Blood corpuscles

17. Diagram of mammalian heart ....

18. Scheme of circulation of blood ....

19. Relation of cells to blood vessels and lymphatics

20. Main lymphatic trunks

21. Alveoli of lung

22. Section of two alveoli

23. Diagrammatic scheme of metabolism .

24. Scheme of closed-circuit respiration apparatus .

25. Original Regnault-Reiset apparatus

26. Regnault-Reiset apparatus as used by Zuntz

27. Scheme of Pettenkofer respiration apparatus

28. Pettenkofer respiration apparatus, explanatory sketch

29. The Mockern respiration apparatus

30. Horse equipped for experiments with Zuntz apparatus

31. Lavoisier's ice calorimeter .....

32. Section of bomb calorimeter .... ^^. The Zuntz tread power dynamometer .

34. Dulong's water calorimeter

35. The respiration calorimeter at The Pennsylvania State

36. Rubner's calorimeter

37. The marbling of meat ......

38. Rate of gain of protein per 1000 pounds live weight

xiii

College

PAGE

213 214

215 222 224 226

237 238

239 356 379

XIV

ILLUSTRATIONS

39." Rate of gain of energy per 1000 pounds live weight

40. Lobule of milk gland .

41. Alveoli of milk gland .

42. Structure of milk gland

43. Partial section of wheat grain

44. Partial section of oat grain .

45. Partial section of maize kernel

398 462

463 463 582

584 588

INTRODUCTION

The problems of nutrition concern the farmer both directly and indirectly — indirectly because his function in society is to furnish the materials for the nutrition of man ; directly, because an essential part of that function consists in the economical conversion of vegetable into animal products by means of farm animals. Particularly is this true regarding the inedible products of the farm. It is a well-recognized fact that only the smaller portion of the solar energy or of the proteins which are stored up in the farmer's crops is directly available for man's use. Even in distinctively food crops, such as wheat, for example, more than two-thirds of the energy which they contain may be unavailable for human nutrition, while the grasses and legumes, so important in all systems of agriculture, are of no direct value as food for man. The essential function of the animal in a permanent system of agriculture is the conversion of as large a proportion as possible of these inedible products into forms whose matter and energy can be utilized by the human body. It is true that animal products contribute largely to our supply of clothing and also that, as a motor, the work animal plays an important part in agriculture and industry. In both respects, however, substitution is possible to a greater or less extent. Vegetable fibers may to a degree replace animal fibers in our textiles, while inanimate motors seem destined to fill an increasing role in power production in all its aspects. But for the conversion of the by-products of the farm and factory into human food, there is as yet no suggestion of an agency which can take the place of the animal body.

With the growth of the non-agricultural population it is increasingly important that this function of conserving the food supply through the utilization of inedible soil products shall be performed with a maximum of efficiency. This requires, on the one hand, as intimate a knowledge as possible of the fundamental laws governing the nutrition of farm animals, so that

XV xvi INTRODUCTION

the transformation may be effected with the least possible waste, and, on the other hand, the ability so to apply these laws as to secure the greatest economic return, since it must never be forgotten that the criterion of success in agriculture is not a maximum production but a maximum profit. It is with the former portion of this complex problem that the present work attempts primarily to deal.

Without entering into the controversy between the vitalist and the mechanist, the nutrition of the animal, whatever its guiding principle, may be regarded as a physico-chemical process, including the entire complex of reactions by which the crude materials of the feed are converted into substances suited to maintain the activities of the body cells or capable of being built up into living structures. In other words, the study of nutrition is a study of the chemistry and physics of the changes through which the crude products of the soil yield animal tissues or secretions on the one hand and excretory products on the other.

The earlier investigators dealt with the food as a supply of matter, dividing it into inorganic and organic constituents and distinguishing among the latter between the nitrogenous and non-nitrogenous substances. In other words, they studied the problems of nutrition substantially as problems of biological chemistry. Rubner's fundamental investigations went far to shift the emphasis to the physical side of the problem. It has come to be clearly recognized that the animal body is essentially a transformer of energy — a mechanism for the conversion of the chemical energy of its feed into motion energy while more or less incidentally a reserve of energy-containing material may be stored up which can be utilized for human food. It is this capacity of the animal body to store up in itself or in its secretions a part of the matter and energy of the feed it consumes which gives the animal its economic significance as a conserver of the food supply. Its value in this respect depends upon the proportion of its feed which it is able thus to set aside — i.e. upon the balance between the income and outgo of matter and of energy — and it is from this point of view that the present volume undertakes to present the nutrition of farm animals. From this standpoint, the subject naturally falls into four principal divisions.

INTRODUCTION xv j{

First, since nutrition involves chemical changes by which feed substances are converted into body substances, there is required some knowledge of the chemical compounds concerned and of their occurrence and proportions in plants and animals.

Second, the conversion of feed substances into body substances is a function of the living organism and it becomes necessary, therefore, to learn something of the processes by which the body effects these changes or, in other words, to study the physiology of nutrition.

Third, in order to apply the principles of the chemistry and physiology of nutrition to the practical problems arising in the feeding of farm animals it is requisite to determine quantitatively the amounts of matter and of energy which are required by different species of animals for their support and for the production of meat, milk or work.

Fourth, to supply the feed requirements as thus ascertained in the most economical manner demands a knowledge of the available feed resources, both as to the nature and quantity of nutriment which they contain and as to the proportion of this nutriment which can be utilized by the body.

Accordingly, the general subject of the nutrition of farm animals is treated of under four general heads, viz. : —