As we understand more about the physiological processes in the food producing animals, we become capable of manipulating these animals to increase their productivity. As new technology develops in agriculture, new industries also develop. The artificial insemination (AI) industry is a classic example. This industry is the result of a quick application of science to agriculture. The primary reason for artificial insemination, and hence this industry, is to speed up the rate of genetic improvement. This is accomplished by greatly increasing the selection differential, wherein one highly selected sire is mated with thousands of females.
Although the commercial use of artificial insemination is recent (1937), the sequence of events leading to todays industry traces back to the 17th century. It was in 1677 that Leeuwenhoek saw spermatozoa through the newly discovered microscope and in 1780 when Spallanzani in Italy discovered that a dog could be impregnated with the cellular portion of semen. He also observed that the spermatozoa could be inactivated by cooling and reactivated later. About 1900, Professor Ivanov was hired by the Russian throne to develop AI for horses. He was an ambitious man and by 1933 he had developed methods for collecting semen and inseminating horses, cattle, sheep and swine. Most of these early inseminations were with sheep and horses. A Dane by the name of Sorenson, who had studied in Russia, returned to Denmark and established the first AI cooperative in 1933.
E.J. Perry, an extension dairyman from New Jersey, was in Denmark at this time. He returned in 1937 and hired a Dane by the name of Larson to help establish the first AI cooperative in the United States. Research with cattle AI had been in progress in the U.S. and by 1939 seven AI cooperatives had developed. The number of AI organizations increased rapidly, as did the number of cows inseminated, the number of breedings obtained from each male, and the conception rate. As competition between organizations developed and costs increased, the small cooperatives consolidated, resulting in the large cooperatives and companies that exist today.
Approximately 60% of the dairy cows in the U.S. are artificially inseminated. This is well below the use of AI in European dairy areas such as Denmark, Holland and England where over 90% are artificially inseminated. The two largest AI organizations are not cooperatives but privately owned companies with nation and worldwide semen distribution. The largest of these, American Breeders Service Global, sells approximately 3.5 million breeding services per year. The second largest is Select Sires.
Although methods for collecting semen and insemination have been available for many years, it is likely that the commercial industry would have developed as rapidly without certain significant research discoveries: 1) the development of semen extenders which would protect sperm cells against temperature shock and thereby allow cold storage, 2) the realization that bull semen could be extended to breed large numbers of cows from each ejaculate and 3) the discovery of methods for frozen storage of bull spermatozoa. In 1939, Drs. Phillips and Lardy at the University of Wisconsin discovered that egg yolk would protect sperm cells from temperature shock upon cooling. The protection was due to phospholipids and lipoproteins in the egg yolk. Extenders combining egg yolk with phosphate, citrate and bicarbonate buffers were soon developed and they form the base for extenders in use today. Heated milk was also found to be a satisfactory semen extender and provides temperature shock protection.
Spermatozoa were some of the first cells frozen; they were successfully frozen in England in 1949. Dr. Polge and co-workers discovered that glycerol in the extender media would protect fowl and bull spermatozoa from damage during freezing. Early freezing and storage was accomplished with dry ice and alcohol at a temperature of -79º C. Later, liquid nitrogen was used as a coolant because its -196º C temperature provided longer and safer storage conditions.
It is generally considered that cattle producers use AI in their herds because 1) it offers service to genetically superior sires, 2) it allows the maintenance of a herd closed to new animals and thus provides disease protection, 3) a dangerous bull need not be kept on the farm and 4) organized breeding management and record services are provided. In swine AI is often used to decrease the cost of maintaining males at the production unit. In turkey's AI is used because mating can not occur naturally.
The methods are feasible but the use of artificial insemination is lower in species other than cattle either for economic reasons or for horses the registry of offspring is restricted. Changes in industry structure often drive changes in the use of AI however. For example in the swine industry the growth of large farm units in the 1990's led to the adaptation of AI to reduce expenses of maintaining males. In horses the change in the Quarter Horse Association to allow the registration of foal from AI with cooled and shipped semen has increased the use of AI.