Hormone-dependent sex differences in growth rate have been known for a long time. It has also been known that growth rate and FCE (feed conversion efficiency) are higher in intact males than in castrates. It was natural, then, that the availability of hormones (हार्मोन्स) and other natural or synthetic substances displaying hormonal activity led to experiments aiming at their use to increase production.
Beginning in the mid-1950s, DES (diethylstilbestrol) and hexoestrol were administered to cattle increasingly in the US and the UK respectively, either as feed additives or as implants, and other types of substances also gradually became available. In general, such treatment has resulted in 10–15% increases in daily gains, similar improvements in FCE and improvement of carcass quality (increased lean/fat ratio). Thus there has been a substantial reduction in the amount of energy required per unit weight of protein produced, and the economic implications of this have been great.
While the use of hormonally active substances in animal production rose, opposition to their use also increased, because of the theoretical possibility that residues in edible tissues might endanger consumers. There are factors leading to the ban on DES in the US, first imposed in 1973, Several reports confirm that DES endangers the health of animals and man when repeatedly used in large doses.
However, as regards risks due to the presence of residues in meat produced according to regulations, no documented deleterious effects have ever been reported in man, either from DES or any other substance with hormonal activity.
A distinction should be made between the hormones as such, for which the metabolism in the body is relatively well known, and synthetic or other substances for whose metabolic inactivation the body may not possess the enzymes necessary. When natural hormones are used in animal production, claims of zero-tolerance residue levels are not meaningful, since these compounds occur in detectable and highly variable concentrations in body fluids as well as in the tissues of all animals, treated or not.
For other substances with hormonal activity the situation is different. However, when residue levels are extremely low, it seems reasonable to weigh the potential risks against the undisputed positive effects some of these compounds have in animal protein production.
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NB-IN INDIA THERE IS NO PRACTICE TO USE HORMONES TO INCREASE PRODUCTIVITY IN FARM ANIMALS.
Hormones are chemical messengers produced and released by endocrine glands, transported through body fluids to act on specific target organs or tissues of the animal body. These chemicals are essential for communication between tissues and organs to regulate several important biological functions like metabolism, growth and development, production and reproduction, stress responses including behavioral activities of animals.
Any defect in hormonal level either excess or deficiency, may lead to disease and hamper the normal physiology of animals. Now a day after advancement of knowledge about hormonal functions apart from their applications as a drug for disease treatment, they are also used for faster growth, better production and reproduction purposes.
The production of meat is controlled by hormones. Growth hormones control the extent of growth, muscle and fat production, feed consumption and milk production.
Treating animals with specific combinations and doses of hormones can make a carcass more valuable, as muscle growth can be increased and fat is reduced. Most importantly, hormone-treated animals are cheaper to rear as they need less feed to maintain muscle. Overall the increase in productivity from using hormones is 5-20%.
The most widely-used treatments are combinations of sex hormones (androgens and estrogens) for use in beef cattle, growth hormones for milk production in cattle and growth in pigs and adrenal hormones (beta-agonists) which increase muscle in pigs and cattle.
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Sex hormones are released via a plastic pellet implanted behind the ear, while growth hormones are given by injection. Beta-agonists are included in animal feed and absorbed in the intestine.
However inappropriate or indiscriminate use of hormones and antibiotics for enhancing productivity can be very dangerous for both animal and human life. Excess or inappropriate use of these chemicals can make animals infertile or very susceptible to other diseases. Not only this but also it may lead to deposition of hormonal or antibiotic residues in meat (residual effect) and their secretion in milk or other animal products which are ultimately used for human consumption.
As animal products like milk, meat, and eggs are used by human for regular consumption so unknowingly human also consume these hormones and antibiotics along with them. This may lead to many diseases like cancer, infertility or predisposes human susceptible to other diseases. So these hormones and antibiotics must be applied very judiciously following the proper guidance of veterinary doctors.
Not only this after administration of these products, before final consumption, the animal must be given minimum withdrawal time (time before which administration of drugs must stop) as per guidelines, which is generally 7days for milk and 45 days for meat.
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All government guidelines must be known by farmers and entrepreneurs regarding this and must be followed strictly in public interest. Similarly, during the purchase of animal feeds, buyer must ensure information regarding hormone supplementation in the feed and take appropriate action according to law.
For example, hormone supplementation as drug or growth promoter must be stopped 45 days prior to the culling of food animals which are reared for meat purpose. This 45 days withdrawal period helps the animal to remove hormonal residues from its body. Similarly, a minimum of 7 days withdrawal period must be given to milk-producing animals before using such animal kinds of milk for human consumption.
MECHANISM OF ACTION OF HORMONES:-
No reliable explanation of how the growth-promoting hormones act has yet been furnished. Some observations indicate an indirect influence through changes in the balance of endogenous hormones. Thus there have been reports of DES and TBA increasing the levels of growth hormone and/or of insulin in plasma; these hormones are known to stimulate amino acid transport across the cell membrane. However, others have found no such effect.
Bulls fed DES (10 mg/day) over two years had significantly higher plasma testosterone levels than controls; those levels are positively correlated with growth. Recent experiments indicate that DES reduces the rate of muscle catabolism in steers.
As regards the anabolic androgens, evidence exists indicating competition with glucocorticoids for receptor sites on the muscle cell membrane. Since glucocorticoids have a catabolic effect on tissues, their displacement from muscle cells would reduce catabolism. TBA alone, and even more when combined with oestradiol-17β, causes a marked decrease in the concentration of total thyroxin in plasma of steers.
In another study, combined oestradiol-17β-progesterone implants (20 + 200 mg) in steers caused a uniform but a slight increase in thyroxine-binding capacity. The significance of these findings is not yet clear.
Hormone applications may be profitable for farmers when used judicially and scientifically. Following are the applications of hormones which can help farmers to enhance productivity from animal farming.
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Induction of lactation:-
In field condition, it has been observed that some animals in a heard remain in reproductive problems like anestrum or repeat breeding for so long period that they ultimately become dry animals and uneconomical for the farmers. Farmers have to feed them for a long time without any production benefit along with treatment cost which reduces overall profitability.
Such animals after hormonal correction can be induced artificially to lactate, even though they have not given birth to a new calf. This can render animals more profitable and animal husbandry sustainable for farmers. The application is more important in buffaloes because there is the tendency of long anestrum period in these animals because of several factors including seasonal effect. It must be kept in mind that help of expert veterinarian must be taken to artificially induce the lactation.
Normal estrogen and progesterone level in these animals should also be checked before starting hormonal treatment along with proper feeding. But all animals may not respond equally and positively to yield the desired result.
In cattle, with the administration of estradiol 17-β and progesterone @0.1 and 0.25, mg Kg body weight/day/animal respectively divided into two parts and administrated twice daily for 7 days, additionally 2 mg reserpine twice daily from 9 to 12 days may start milking on 10th days. This can provide up to 50-80% of peak milk yield of animals. Simultaneously chance of estrous is also seemed to be not affected. Second induction of lactation may be possible only by short administration period for 3 days only and average milk yield may be up to 3 to 9 kg/ day depending upon diet, breed, and response of an animal to treatment.
Buffalo and its heifer having reproductive problems can also be induced artificially to lactate. Administration of estradiol 17-β and progesterone @0.1 and 0.25 mg Kg body weight/day/animal subcutaneously, divided into two parts and administrated twice daily for 7 days may start lactation after 14-20 days and can yield milk up to 700 kg in 200 days lactation period.
Different combinations which can be used for this purpose is given in Table.1. However, it must be noted that animals must be treated by expert veterinary doctors for this purpose along with a supply of balanced nutrition as per expected yield. Initially, milk will be slightly yellow which become normal in next one week. First-week milk should be discarded.
Oxytocin Injection for milk let-down:-
Oxytocin can induce milk let-down by contraction of smooth muscles of the udder if is in the proper physiological state. But the use of this drug is restricted as per law neither by nor on the order of a licensed veterinarian due to health hazard by its residual effect in milk. However, it can be used in conditions like to precipitate labor and induce normal parturition, for postpartum evacuation of uterine debris, for postoperative contraction of the uterus after cesarean section and control uterine hemorrhage etc. in consultation of a veterinary clinician. It should not be used to treat dystocia due to the abnormal presentation of the fetus until correction is made.
Hormones can be used as a growth promoter in animals reared for meat purpose. Before administration of these hormones, farmers must know local rule and regulations along with the rule of the country where it is intended for export if any.
These growth promoters can be administered as an implant or given in feed as a supplement. The hormones 17β-estradiol, progesterone, testosterone, zeranol, trenbolone and melengestrol acetate (MGA) promote growth in cattle/ buffaloes. These compounds must be given with extra care and farmer not willing to use such compounds must ensure that concentrate they are buying is free from such hormone supplementations.
When given in excess, these hormones have adverse developmental, neurobiological, genotoxic and carcinogenic effects on people who consume them, either via the parent compound or via metabolites. Implants of 20-30 mg estradiol-17β and its combination with other hormones like progesterone can lead to nearly 10-25% extra body weight gain in the calf.
Similarly, the lean/fat ratio in male castrated and female pig carcasses may be increased by the use of estrogen/androgen combinations. There is a list of combinations of hormones given in table 2 used for animal growth.
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The estrous synchronization means making all mature female animals to come in estrus at a time by application of hormone or another method. This may also be helpful to treat anestrous animals to let them come in heat. Apart from this, it may also produce a more successful response by animals to artificial induction of lactation. Estrus is the time when animal become receptive to male so that successful pregnancy happen.
This is more commonly practiced in cattle and buffaloes but can also be used in sheep and goat. Estrous synchronization may be done by administration of hormone PGF2-alpha alone or along with other hormones like gonadotrophin-releasing hormone (GnRH) or progesterone. GnRH is sometimes also replaced by estrogen. The selection to choose combinations depends upon the physiological condition of animal and cost-effectiveness of the treatment.
This hormonal treatment is also beneficial for herd management, as estrous synchronization of all animals in a herd can reduce the management expenses, helps to plan offsprings in a better way, and reduces the medical and other associated costs. For example, if a farmer has 20 animals in his herd and 14 are open, then synchronization of estrus will help to come to all animals in heat at a time.
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This will lead to insemination of all animal on nearly same day and reduce the doctor visit cost, similarly when they become pregnant then management of feeding and other care like immunisation etc. will be easy, and this also will reduce cost in terms of drug wastage, feed procurement, doctor visiting cost, manpower rationalisation, cost associated with birth of calf etc.
This reduction of cost ultimately will lead to increase in profitability from animal husbandry practices. Further, farmers can also time the season or month of calving as per their convenience. Another benefit is that cow nutrition can also be improved by grouping cows according to the stage of gestation and feeding each group accordingly and nearly all calves will be of same age and weight, so their management will also be easy.
There are several protocols for estrous synchronization like prostaglandin used alone in cattle during the late stage of the luteal phase (11 to 15 day of the estrous cycle), the success rate is higher than those injected in the early part (6 to 9 day) of the luteal phase.
However, it must be kept in mind that if the protocol is for a heifer, it must have gained 50-60% of adult body weight, while in case of the cow the body condition must be very healthy and should have 50 days Post-Partum period or have shown anestrum for more than 50 days. Controlled internal drug release (CIDR) technique can also be used for this purpose.
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In this technique, progesterone or related hormone is implanted near the ear or in the vagina of the animal. In general CIDR®-PG protocol is recommended in heifers in contrast to the Select Synch+ CIDR®protocol in cows, however, it depends on animal condition so doctor itself have to decide it.
Select Synch+ CIDR®protocol, GnRH is given on day 0 and then day 7 of CIDR followed by administration of PG on the 7th day. Then heat is detected and artificial insemination (AI) is done between 7th to 13th day. While in CIDR®-PG, only 7 day CIDR implant followed by administration of PG on the 7th day is recommended. Then heat is detected and AI is done between 7th to 13th day.
To understand the benefit in simple words, normally animal shows 3 cycles in nearly 66 days so we can get only 3 chances of service for the animal while if we apply estrus synchronization we can get minimum 4 chances to AI the animal.
Apart from, another hormone-like growth hormone is used for enhancing milk production in other countries like the USA but presently is not allowed in our country.
Table 1. Use of hormonal combinations for induction of lactation
|estradiol 17-b and progesterone @ 0.1 and 0.25 mg/ Kg body weight/ day / animals subcutaneously, divided into two parts and administered twice for 7 days followed by 25 mg hydrocortisone acetate on 19 to 21 day|
21 day onward
Table 2. Hormonally-active substances used in animal production
Main use – Animals
|DES(diethylstilbestrol)||10–20 mg/day||feed additive||steers, heifers|
|DES||oil solution||veal calves|
|Hexoestrol||12–60 mg||implant||steers, sheep, calves|
|Zeranol||12–36 mg||implant||steers, sheep||Ralgro|
|Melengestrol acetate||0.25–0.50 mg/day||feed supplement||heifers||MGA® 100/200 Premixes; MGA® 500 Liquid Premix|
|TBA||300 mg||implant||heifers, culled cows||Finaplix|
|DES + Methyl-testosterone||feed additive||swine||Maxymin|
|Oestradiol-17β benzoate +|
|Oestradiol-17β benzoate +|
Table 3. Currently available implants, active ingredients, and concentrations.
|Trade Name||Active Ingredient||Concentration (mg)||Marketer|
|Component E-C||estradiol benzoate|
|Component E-S||estradiol benzoate|
|Component E-H||estradiol benzoate|
|Finaplix-S||TBA||140||Intervet (Hoechst Roussel)|
|Finaplix-H||TBA||200||Intervet (Hoechst Roussel)|
|Intervet (Hoechst Roussel)|
|Intervet (Hoechst Roussel)|
|Intervet (Hoechst Roussel)|
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So in conclusion apart from treatment of diseases, hormones can be applied to obtain better profit by farmers and entrepreneurs. Judicial application of these chemicals under surveillance of veterinary doctor can enhance the profitability of farmer without side effect on animal and human health.
Although the government does not encourage the use of these drugs as a feed additive, it had been seen that some of the large entrepreneurs and feed mills are using it as a feed supplement to gain profit. So the government must make and implement law strictly to prevent the misuse of such drugs by these rich people.
If the government is really serious on the issue then it must amend the law to make mandatory discloser for all commercial feed manufacturers that their feeds are free from hormone, antibiotics or if they have added then in which product and in what amount. Otherwise, this will be a discriminating step to allow profit to the big entrepreneurs whereas the small and marginal farmers will be the sufferer and may not be able to sustain in the highly competitive market.