ESSENTIALS OF ANIMAL BREEDING. 



GEORGE M. ROMMEL, 

 Chief, Animal Husbandry Division, 



CONTENTS. 



Basic facts about heredity 



The science of breeding 



The unit of life 



The beginnings of life 



The gestation period 



Incubation period in birds. 



Determination of sex 



Fecundity 



Prepotency Mendel's law. 



The art of breeding 



Selection 



Inbreeding 



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 4 

 4 

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 8 



10 

 10 

 10 

 11 

 17 

 17 

 20 



The art of breeding Continued. 



Outcrossing 



Pure breeding 



The value of a pedigree 



Livestock improvement 



Grading up 



Crossbreeding 



Some incorrect ideas of heredity 



Telegony 



Maternal impressions 



Conclusions... 



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 31 

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 36 



BASIC FACTS ABOUT HEREDITY. 



IN DEALING with the subject of heredity we must recognize 

 clearly the following facts: First, animal and plant forms, as a 

 rule, have developed gradually and very slowly, by very small 

 changes ; in short, by the process known as evolution. Second, what- 

 ever an animal has, so far as its inheritance is concerned, it gets from 

 its parents they get theirs from their parents, and so on clear back 

 to the beginning; nothing was imposed from the outside. For the 

 present, accept this fact without question. We shall try to make it 

 clear later. Third, a very clear distinction should be drawn between 

 the effects of inheritance and the effects of food and environment. 



Every one who is at all familiar with domestic animals knows what 

 a wonderful effect the food an animal eats has on its development, 

 especially when it is young. It is also known that the younger an 

 animal is the more readily it is influenced by its food. Now, from the 

 very first moment that a young animal begins to develop, from the 

 very instant that growth begins with the fertilization of the egg 

 cell, it receives food from some source or it dies. When it is 

 only a single cell it is being fed. If a young animal after birth is 



NOTE. In the preparation of this article, the writer received material assistance 

 from officers of the Bureau of Animal Industry, especially Messrs. F. R. Marshall (now 

 secretary of the National Wool Growers' Association), Sewall Wright, 'Dr. John E. 

 Mohler, and Mr. D. S. Burch. He is also greatly indebted to Mr. Dewitt C. Wing, of 

 Chicago, who made many helpful suggestions. 



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