Farm Animals, Internal Structure of

the anatomical and histological stucture of the organs and tissues and the biochemical and physiological characteristics of farm animals that are related to their productivity and breeding qualities; a basic part of the study of the constitution of farm animals. The Russian scientists P. N. Kuleshov and E. F. Liskun and such foreign scientists as C. Malsburg, W. Duerst, and C. Kronacher began making comparative studies of farm animals at the turn of the 20th century. The objects of their studies included organs and tissues (mammary gland, heart, lungs, liver, endocrine glands, skeleton, skin, muscular and connective tissue, blood), blood groups, types of individual proteins, higher nervous activity, and metabolism.

Research showed that animals with different types of constitution and productivity differ significantly in many internal characteristics. For example, the mammary gland, digestive organs, respiratory and circulatory systems, thyroid gland, and pituitary body are better developed in dairy cattle than in beef cattle. In dairy cattle, as compared to beef cattle, the outer layers of skin are better developed, the subcutaneous tissue is less developed, the skin has more sweat and sebaceous glands, and the hairs are thicker. Dairy cattle also have fewer erythrocytes and less hemoglobin per unit of blood, but they have more blood and its most important constituents per kg of liveweight. Their blood pressure is lower, respiration and pulse faster, and metabolic rate higher. Comparable differences have been found in other species of farm animals—for example, in running horses versus pacers, in swine bred for lard versus those bred for meat, and in wool sheep versus meat sheep.

The study of the relationships between internal characteristics and productivity and constitution led to a deeper knowledge of the biological basis of productivity; thus, an animal’s productivity could be predicted at an early age, and animals could be evaluated more precisely from their constitution and breed qualities.

Modern studies of the internal structure of farm animals in the USSR and abroad (USA, Great Britain, Federal Republic of Germany, Poland, German Democratic Republic, Czechoslovakia, and Denmark) focus on the relationship between internal characteristics and productivity of animals and on the inheritance of these characteristics. High correlation factors have been found, for example, between the relative amount of blood and plasma (per unit of liveweight) and milk productivity; iodine content of the thyroid hormone thyroxine and milk yield of cows; type of higher nervous activity and milk yield of cows; blood lipid levels and fat content of of milk; parameters of red blood cells and friskiness of horses; serum proteins and early growth of swine; serum alkaline phosphatase and phosphatides and egg production of hens; thyroid activity and growth energy of chicks and piglets; and skin structure and the length and fineness of wool in sheep.

During the 1960’s the USSR, the USA, Great Britain, Denmark, Sweden, Poland, and Czechoslovakia did extensive research on blood groups and hereditary types of blood, milk, and egg proteins, particularly on the nature of their inheritance and the relation to productivity and reproduction in animals. The blood groups and type of individual proteins were found to remain unaltered for life. The accumulation of information on blood groups and types of proteins is an aid in checking data on the origin of animals; distinguishing between identical and fraternal twins; and studying the structure of breeds, their origin and interrelationship (a matter of particular importance for breeds of ancient origin), and the characteristics of interbreed groups—male lines and-yterine families, for example.