FARMER'S CYCLOPEDIA OF LIVE STOCK 



shell are formed, and further develop- 

 ment within the egg ceases until the egg 

 is incubated by natural or artificial heat. 

 In mammals likewise the egg is ferti- 

 lized at the surface of the ovary or in 

 the oviduct after which it passes into 

 the uterus. ;Here it becomes attached, 

 surrounded with membranes and under- 

 goes its development. The necessary 

 sustenance for the developing bird is 

 furnished in the large yolk and white of 

 the egg. In mammals the nutriment for 

 the fetus comes directly from the blood 

 of the motber through the uterine walls, 

 and by means of an interlacing network 

 of maternal and fetal blood vessels. 



The duration of pregnancy r gesta- 

 tion is four weeks in the hare, eight 

 weeks in the cat, nine weeks in the dog, 

 XI weeks in the sow 21 weeks in the 

 sheep, 22 weeks in the goat, 41 weeks 

 in the cow, 47 weeks in the mare, 12 

 months in the ass. 



The number of young born by mam- 

 mals has been considerably increased by 

 domestication, breeding and selection. 

 The tendency to produce twins in the 

 case of sheep and large litters in the 

 case of the sow is hereditary as is also 

 the tendency to come into heat at fre- 

 quent intervals. The mare comes into 

 heat about 10 or 12 days after parturi- 

 tion and the cow after 20 days. In gen- 

 eral the number of young born at one 

 time varies with the size of the species 

 and the length of the period of preg- 

 nancy. The number of young is great- 

 est in small mammals and those with a 

 short period of gestation. 



Barrenness or sterility y?\\\ be dis- 

 cussed in the chapter on animal diseases. 

 BREEDING FARM ANIMALS 



In breeding farm animals the purpose 

 is not merely to increase the number of 

 individual animals and thus perpetu- 

 ate the race, but also to improve the 

 quality of the individual. Intelligent 

 breeding is done with some definite ob- 

 ject in view. The breeder has a pur- 

 pose in mind and wishes to obtain an- 

 imals which conform to some standard 

 in respect to size, weight, form, color, 

 proportion of parts, quality of meat, pro- 

 ductiveness of milk, wool, mohair or 

 other products, speed, action, disposition, 

 fertility, early breeding habits, vigor, 

 constitution, ability to transmit good 

 characters to offspring, and numberless 

 other points which may be considered 

 the legitimate aims of breeders. Some 

 matters recorded in the literature of this 

 field of study are of too theoretical or 



controversial nature to suit the purposes 

 of the present volume. An intelligent 

 discussion of the subject, however, is im- 

 possible without considering the impor- 

 tant basis of theory upon which practi- 

 cal breeding proceeds. To be sure these 

 theories, in so far as they have any real 

 value, are themselves based on actual 

 practice or experiments in breeding. The 

 results of practice and experiments, for- 

 mulated more or less wisely into hypoth- 

 eses or theories, serve to guide breeders 

 in subsequent experiments which in turn 

 may substantiate or discredit the theo- 

 retical propositions thus far maintained 

 by breeders. 



Artificial selection—Breeding is es- 

 sentially a process of artificial evolution 

 in which man attempts to regulate 

 and develop natural tendencies in a 

 definite direction. In natural evolu- 

 tion the fit and the unfit live together 

 and interbreed, at least so long as the 

 unfit are able to exist. Progress in any 

 given direction is therefore slow, being 

 greatly retarded by the intermixing of 

 incongruous tendencies. In the origi- 

 nation and improvement of breeds of 

 live stock, on the other hand, artificial 

 selection is rigidly enforced and only 

 those animals which show the desired 

 characters in the highest degree are 

 used for breeding purposes. In this way 

 undesirable tendencies are eliminated 

 and the process of evolution greatly 

 hastened. 



Heredity — I n general the young of 

 animals resemble their parents more or 

 less closely. In the language of the 

 breeder like produces like. This ten- 

 dency on the part of offspring to resem- 

 ble their parents is called heredity and 

 is necessarily an important factor in 

 all breeding work. But if offspring 

 were exactly like their parents that 

 would be the end of the matter and 

 there would be neither a science nor 

 an art of breeding. Fortunately as a mat- 

 ter of fact no two animals are exactly 

 alike. If a number of sheep, hogs, cattle 

 or other farm stock of the the same breed 

 and closest relationship be examined, 

 they will be found to show differences 

 in form, size, color, disposition, etc. This 

 tendency of animals to differ from one 

 another and from their parents is called 

 variation and is the corner stone of the 

 whole science and art of breeding. 



Variation — Darwin in his "Origin of 

 Species" and "Plants and Animals 

 under Domestication" recorded an enor- 

 mous number of facts regarding the de- 

 tails of variation in domesticated ani- 



