Hormones play a key role in an animal’s growth and development, influencing everything from frame size to muscle production and feed efficiency. Growth stimulants and implants are tools that help farmers harness this natural potential, enabling animals to grow faster and convert feed into meat more efficiently. In this Q&A, Dr François de Villiers explains how these products work, the different types available, and how to use them safely and effectively to improve growth, carcass quality, and overall profitability.
Question: What are the benefits of growth stimulants and implants, and how do I use them?
Answer: If the growth potential of a young bull is compared to that of a heifer or a young ox, or the growth of a young ram with that of a young ewe and a wether, it is obvious that the masculine hormone, testosterone, plays an important role in the growth potential of an animal. The condition of a pregnant ewe or cow also improves much more quickly than that of an animal that is not pregnant, because more of the feminine hormone, progesterone, is produced. It is therefore clear that hormones play an extremely important role in growth potential and in the conversion of feed to meat in the animal.
But, as for humans, production of the hormones in animals is delayed until after puberty so that the animal is able to grow big and strong while still with its mother, and does not grow too confident too soon and seek confrontations with bigger animals. The growth rate of an animal intended for slaughter can, however, be accelerated by implanting stimulants at an early stage in its life. By giving an animal specific growth stimulants at specific times, it is possible to allow certain attributes to develop sooner than they otherwise would have, which cause it to become bigger and heavier earlier in its life.
Growth stimulants are not miracle substances that simply make an animal grow faster, but they do enable the conversion of supplementary feed into additional carcass weight to take place extremely efficiently. If a growth stimulant is administered at an early age, certain of the animal’s glands are stimulated to secrete larger quantities of certain hormones. The animal’s bones grow more rapidly, which leads to a larger frame. Its appetite is stimulated so that it eats more and therefore grows more quickly. This, in turn, stimulates the metabolism so that more muscle is produced, more quickly, which improves the slaughtering percentage and ensures that the ingested energy is used for muscle production rather than for producing fat.
Various growth stimulants are available. There are products that are mixed into the feed, which enable rumen bacteria to produce energy for the animal more quickly, or which suppress bacteria that produce harmful products, such as lactic acid, which causes rumen acidosis. When it comes to the growth hormones that are administered in the form of ear implants, there are several important ones we should look at; these are the male and female hormones. The male hormone, testosterone, is the most important for muscle development. This is easy to see if we compare the frame of a large bull with that of a cow.
Trenbolone is an artificial alternative which is a hundred times more powerful than testosterone. It can be incorporated into an ear implant. Because trenbolone is such a powerful stimulant, it is very important to use it correctly and not to give the animal too much. Too high a dose in small animals could result in their inability to produce fat, and in tough meat.
There are two important female hormones. Of lesser importance is progesterone, the hormone that pregnant animals produce in relatively large quantitiess. It helps them to improve condition rapidly and to become fat. This hormone in an implant promotes the economical use of feed, but it is there to improve an animal’s condition rather than to promote its growth.
The most important female hormone is oestrogen. It promotes appetite, raises the metabolic rate and increases growth rate, so it plays an extremely important role in promoting the animal’s average daily gain (ADG).
Synthetic products are available that can be used in ear implants, but overdosing can lead to problems such as rectal prolapse. There is also a natural growth stimulant that is not hormonal, but gives the same results as the growth hormones mentioned here. This stimulant has several interesting properties, which make it a particularly useful aid to the farmer. The main action of this product, which has seranol as its active ingredient, is to stimulate the glands to increase their hormone production.
The first important hormone of which the levels are increased is somatotropin, which is responsible for the growth of bones and muscles, and which results in a bigger, heavier animal. This hormone not only gives a bigger frame, which later results in a larger carcass, but also a larger pelvis, which can help first-time heifers – especially Holsteins – to calve. Because the effect of seranol resembles, in certain respects, that of oestrogen, it also suppresses the development of the testicles in the early stages of the young bull’s development. This process has the effect of castration without putting the animal through the trauma of castration and its consequences. Such animals perform much better in the feedlot, firstly because they are calmer, and secondly, because seranol’s stimulation has already prepared them for faster growth in the feedlot.
When choosing an implant, it is important to know how old the animal is, its gender, how long it will be fattened and when it will be marketed. There is a wide variety of implants on the market. In order to make the correct choice, it is important first to consider the carrier of the active ingredient in the implant, because this determines the length of the period for which the implant will be active. Silicone implants can remain active for a long time. The implant that has a cholesterol carrier can remain active for up to 150 days, but implants that have lactose as a carrier seldom remain active for longer than 100 days. Implants containing a lactose carrier react much faster because they release their stimulants more rapidly. For this reason, if implants having a lactose carrier and high hormone doses are chosen, it is strongly recommended that they be used only for large, heavy animals.
Implants that contain seranol, testosterone, oestrogen and progesterone are usually more suitable for small animals which have to be prepared for the feedlot for a short period.
Weaned calves that are ready to enter the feedlot should receive implants containing trenbolone and oestradiol -17 beta, so that the levels in the animal are high enough for the feedlot. As most cattle are fattened for periods of 100 to 150 days, it is important that implants having a cholesterol carrier be used for this period.
It is also important that small animals should not receive implants having too-high levels. Such animals should rather receive an implant having lower levels until they are ready for the feedlot, and then be reimplanted. Correctly used, growth hormones are a great asset to the farmer and today play an important role in the profitability of feeding animals.
Source: Agricultural Research Council (ARC)
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