2006, Vol 1 No 1, Article 3

Role of Anabolic Steroids in Meat Industry-

Residual Effect and Safety Aspect

Khurshid Ahmad Shah
BVSc & AH, MVSc (Livestock Production & Management)

Department of Animal Husbandry, Kashmir, India

INTRODUCTION

Animal growth is a complex interaction of genetic makeup, environment, nutritional and the hormonal influences. The quest for regulating the overall growth of farm animals has long evoked the interest of many a workers. With the advancement in scientific techniques and manipulation of the endocrine status of animals by administrative of exogenous compounds, this quest has seen a sort of a culmination through the use of anabolic steroids (testosterone, Estrogen and progesterone).

In 1984 A. A. Berthold, a German scientist, isolated for the first time the hormone testosterone from the male gonads and a few year later another hormone estrogen was isolated from the female gonads. Both these hormones are steroid in nature and exert genital effect (Development of secondary sexual characters) and extra genital/anabolic effect (retention of nitrogen, calcium and phosphorus ). The nitrogen retaining effect of these hormones was reported for the first time by Kochakian and Murlin (1935) in a study on castrated dogs who were injected with androgen containing extract obtained from urine of a normal man.
Prolonged use of these hormones produced sexual dimorphism in food animal. This shortcoming led to search of a product with least genital and maximum anabolic effect and consequently in 1940 a Powerful protein sparing /synthesizing agent with least genital effect was developed and named as anabolic steroid.
rom time immemorial man had tried to exercise his control over the sex ratio and manifold theories & false beliefs had been practiced.

Anabolic steroids are derivatives of cholesterol and including

1. Natural Steroids: Mainly oestradiol, testosterone and progesterone.

2. Synthetic Artificial Steroids: include trenbolone, ethynyl estradiol, methyl testosterone, chlormadinone acetate, malengestrol acetate medroxy progesterone, nortertosterone (Nandrolone) etc.

3. Non-Steriod Compounds: these include diethyl stilbestrol, hexestrol, dienestrol, zeranol.

A significant improvement in feed conversion efficiency and body weight gain has been achieved in different food animals following administration of anabolic by various workers all over the globe (Table I).
In Australia alone, anabolic steroids were used on 45% of nation’s eligible cattle and claimed to provide a net benefits to the industry of over 60 million dollars a year (AVCA 1986). In spite of tremendous beneficial effects, the use of anabolic agents in food animals was not much appreciated by the European scientific community because the question of residues in edible tissues of food animals following treatment remained an important consideration in assessment of health risk to consumers.
The main objective of this article is to bring together major facts based on scientific evidences and opinions in an attempt to clarify some issues regarding residual problem of anabolic steroids and safety to consumers.

MODE OF ACTION

Anabolic steroids play a pivotal role in bone growth basal metabolism muscular development, calcium retention etc. (Guyton1976) They are believed to act directly at the cellular level in muscle tissue through specific receptors to regulate protein synthesis and degradation (Scott, 1978 and Peter, 1985) and indirectly by activating higher centers to stimulate release of anabolic hormones viz growth hormone, insulin (Wagner et al, 1978 and Peter, 1985) and prolactin (Heiztman 1979, Schan 1985)
Little doses of progesterone also activate higher centers to stimulate release of anabolic hormone. Moreover, continuous administration of progesterone in beef heifers prevents ovulation but allows follicular growth. The estrogen released from these follicles exerts anabolic effect which results in body weight gain (Hafez 1991)
The increase in secretion of growth hormone following the administration of anabolic steroids also results in increase in plasma glucose concentration. The combination of increased growth hormone and insulin in the muscle cell probably increase protein accretion (Trenkle 1970). The net effect of each anabolic is to improve the rate at which nitrogen is retained by animals inside the muscle cells i.e. production of more protein. Apparently the increase in N-retention occurs without altering the absorption or metabolisms in alimentary tract (Chan. et. al 1975). The Gross effect of these products are increase in rate of feed in take, daily weight gains, feed conversion efficiency and (proportion of ) lean meat in carcass. Owing to increase in feed intake, the percentage increase in efficiency is approximately half that of the increase in growth rate (Sawyer and Barker 1988)

EFFICACY OF ANABOLIC STEROIDS

The Magnitude of growth response following administration of Anabolic agent is dependent upon various factors. Females tend to grow better with a compound having some androgenic properties. Entire males gain more with an estrogenic compound alone or in combination with androgen. Where as castrated ones tend to grow faster in presence of smaller amountt of estrogenic activity.( Hieztman 1983, Shah and Shrivastava, 2002 and Lamming, 1986)
Younger and lighter animals responds less than older and heavier ones (Wal et al , 1975 and Sammons 1980), yearlings are the most responsive class of cattle (Perry et al, 1970 and Hodge et al, 1983)
The increasing dose (the number of implants) does not increase growth promoting response because animals capacity to respond is limited and once this capacity is attained any subsequent response in progressively diminished. (Summons, 1980 and Roche & Davis, 1983)
Animals kept on ordinary glazing condition respond less than feedlots due to variability in level of nutrition, however the timing of implantation in relation to the animals cycle of pasture particularly the “flush” of feed is an important consideration which may affect magnitude and duration of response achieved (Sammon, 1980 and Hodge et al, 1983)

RESIDUE IN EDIBLE TISSUES

The anabolic agents residue in meat arises from three sources

1. Residue emanating from the animals own endocrine system.

2. Residue derived from natural anabolic agent administered to living animal.

3. Residue emanating from xenobiotic anabolic agents administered to living animal.

Meat may contain residue of drugs or their metabolites at very low concentration (PPM/PPB/PPT). The concentrations vary widely with the nature and origin of samples (animal species, tissue, biological fluid, excrete)
The concentration of anabolic agent remains highest in plasma following implantation and comes to basal level in 6 to 19 weeks. The residue concentrations tend to be highest in liver, kidney and subcutaneous fat and the least in muscles (Heitzman, 1977 and Macvanish & Galbrath 1988 and 1993).

SAFETY TO CONSUMERS

The natural steroids (testosterone, progesterone and estrogen) when used over a prolonged period at extremely high doses are believed to be carcinogenic particularly in animals/women having a hereditary susceptibility to mammary cancers. There is insufficient proof that trenbolone, zeranol and malengesterol acetate are not carcinogenic at such dose levels (Roe 1974). The question which arises is whether the residues in animal products are at a concentration which would be carcinogenic to the consumers. This is highly unlikely in the case of the naturally occurring steroids and extensive testing on xenobiotic agents revealed that these compounds are not mutagenic, carcinogenic or genotoxic (Lamming 1986).

Taking into consideration the human and animal endocrinology and metabolism of these hormones, firstly these hormones are present naturally in man and animals in concentrations which are manifold higher than the possible intake from eating meat of implanted animals. Each day a non-pregnant woman produces 5400 times and an adult man 13500 times the amount of estrogen found in 500g of steak form an implanted steer. Like wise one hen’s egg (50-60gms) contains about 2800 times the amount of estrogen found in 200 gms of steak from an implanted steer ( Gallrainth, 1981 and Rubens & Vermeular, 1983). Therefore the hormone ingested in meat from a correctly implanted steer is negligible, when compared to concentration of hormones in different food stuffs (Table 2 and 3) due to endogenous hormone production. It is believed that such minute amounts of hormones consumed would not interact with endocrine mechanism. Mankind has been consuming meat and animal products from lactating, pregnant or entire animals for thousands of years and these are therefore natural constituent of food of animal origin and their consumption has been well tolerated.
These anabolic agents have low oral activity and are rapidly metabolized and excreted by entero-hepatic system (Hoffman, 1981; Karey et al, 1983 and Rico & Burgotsacaz, 1983). This even the negligible amounts consumed in meat are further diluted before entering the circulation.

Further safe guards may be provided by adopting following measures:
a) The site of implantation and implanting of anabolic agent in non-edible part, ear etc which could be discarded.
b) Designated withdrawal period.
c) Exploring possibilities of altering postnatal growth by prenatal exposure of animal to anabolic steroids for example implanting pregnant ewes at 40-60 day of gestation with trenbolone (Dehenn et al, 1990).
d) Instead of skin implanting which exhibit slow release and biodegradability, injectable anabolic agents be considered. Nandrabone injection has proved to be very successful in promoting growth in kids and calves (Shah and Shrivastava, 2002; Shaheen et al, 2002 and Dhurbajoti, 1994)
e) Anabolic agents may preferable be tried in kids because goats produces more lean meat and lack tendency to deposit subcutaneous fat particularly over the lion region (Agnihotri 1993).
f) The natural steroids exert 300 to 800 times more response than synthetic ones and are excreted more rapidly (Sawyer and Barker, 1988). Their use in low doses may thus nullify the residual effect in meat animals. A significant increase in body weight has been achieved by administrative of bovine follicle fluid (sources of natural estrogen) in kids (Shah and Shrivastava, 2002).
 

TABLE 1

Table 2

 Estimates of effective estrogen intake for various food portions

Adapted from Sawyer and Barker, 1988

Table 3

Residue level of anabolic steroids (ng/g) in tissues of treated and untreated cattle /steer

Adapted from Macvanish and Gylbraith, 1993 and Sawyer & Barker, 1988