Last update: August 18, 2011 07:47:25 AM E-mail Print

 

ANABOLIC STEROIDS AND GROWTH

 

P R KING, J J OLIVIER AND J DIEDERICKS

GROOTFONTEIN COLLEGE OF AGRICULTURE, MIDDELBURG EC

 

What are anabolic steroids?

The reproduction functions of the male is regulated by various hormones. The term Androgens refers to the male sex hormones secreted by the testis and the adrenal gland. The Androgens all belong to a group of organic compounds known as steroids. Steroid hormones are synthesized in specific body tissue through complex biochemical reactions using cholestral as precursor. By far the greatest quantity of androgens are however secreted by the testis. Although several male sex hormones have been isolated from the testis, testosterone is so much more abundant and potent than the others that one can consider it to be the single significant hormone responsible for the male hormonal effects caused by the testis. The adrenal gland also secretes at least five different androgens but under normal conditions the secretion is very low and is not able to maintain the action of testosterone in castrated male animals. The ovaries and adrenal gland of the female also produce androgens but not in quantities sufficient to exhibit the effects of these hormones as in males.

 

Function of androgens

Androgens are essential for the norma1 development of the male. In general, testosterone is responsible for the distinguishing characteristics  of the mascu1ine body.  From birth till puberty essentially no testosterone is produced but thereafter the production increases rapidly. High levels of testosterone persists throughout most of the remainder of life, dwindling rapidly at old age. Under the influence of testosterone the penis, scrotum, and testis enlarge many-fold. The secondary sexual organs namely the seminal vesicles, prostate gland and the Cowper glands are also dependant on testosterone for maturation and sustentation.

 

Relationship between growth and androgens

As early as 1935 it was demonstrated that testosterones has a nitrogen-retaining property thus when testosterone is injected subcutaneously it decreases the secretion of nitrogen from the body.  On further investigation it was found that this was caused by an increase in the production of proteins mainly in muscle sells.  An abundance of scientific papers demonstrating the positive effect on growth and feed conversion caused by the administering of androgens in sheep and cattle is available.  Androgens however only stimulates the growth of animals when the protein intake is adequate.  This growth-promoting phenomenon is known as the anabolic function of testosterone.  Since the discovery of the anabolic function of androgens a search has been conducted  for synthetic steroids that would produce the anabolic effects characteristic of testosterone without producing the androgenic or secondary sex-stimulating effects equally characteristic of testosterone.  Many synthetic steroids with favorable anabolic characteristics have been synthesized up to date but all have a more or lesser androgenic capacity.

 

Effect of artificial anabolic steroids on breeding animals.

When androgens are administered to intact male animals to enhance growth a stimulating effect is found on the secondary sexual organs.  These organs respond by increasing in weight.  At the same time however the secretion of testosterone by the testis is inhibited.  This leads to a decrease in testicular size, accompanied by decreased spermatogenesis.  Although libido is not affected by anabolic steroids there is a marked decline in quality, particularly in sperm number per ejaculate, and in semen volume.  Because of the negative effects on the sexual development of rams it is not advisable to administer androgen to animals which will be used in future breeding programs.

 

The detrimental effect  of using artificial anabolic steroids on breeding and selection

All production traits are regulated by hormones.  The production of hormones on the other hand is controlled by genes and is therefore subject to the genetic make-up of that specific animal.  Genes are transmitted from generation to generation and form the basis for selection.  When selecting for growth rate, animals with “favorable” genes for this trait are selected, and a good chance exists that that these genes will be transmitted to their progeny.  When androgens are administered to growing animals on a high plane of nutrition it leads to an artificial increase in body size.  Obviously this increase in body size is not representative of the animals’ genetic make-up and therefore its offspring will not benefit from it.  If some stud breeders make use of anabolic steroids while others do not the ram buyer can not be sure whether the size of the ram is genetically based or the result of artificial hormone manipulation and consequently this malpractice may lead to suspicion among ram buyers which could have a detrimental effect on the whole stud industry.

 

Published

Merino newsletter December