Hormone implants for chickens

Yesterday we made the decision to have a hormone implanted into Spot. This decision was made because she had very thin, wrinkly shelled eggs that no amount of calcium supplementation was able to fix. Spot ran the risk of having an egg break inside of her during laying, which could lead to a fatal infection.  I had heard of a hormone implant that would stop her from laying eggs, which would allow her body to recover (she has pretty much laid non stop for about 2.5 years). With a vet examining her eggs and confirming that she would benefit with the implant, we went ahead.

I had posed this question on the Chicken Instagram community and received a lot of questions about it. So I thought I would share what I have learned and the vet's comments.

What is Suprelorin?
Suprelorin is the trade name given to the hormone implant. Proud to say that this implant is an Australian invention! Manufactured by Peptech Animal Health in NSW, the patent was granted in 2002. Looking through the patent, the implant comprises of 2-15% of hormone, supplemented with 0.5-3.5% lecithin and 89-94% stearin. From what I gather, lecithin acts as an emulsifier, allowing better distribution of the hormone and may assist in release of hormone into the surrounding tissue. Stearin is a solid fat that has a melting temp of about 55C and makes up the bulk of the implant and allows it to be formed into a rod shape as it is extruded.

In it's final packaging, the hormone "rods" are preloaded into syringe applicators. All that has to be done is to remove the protective cap from the applicator and inject the implant under the skin. The preferred location is in between the shoulder blades. Once implanted, the hormone is slowly released into the surrounding tissue.

Suprelorin is available in Australia and Europe, but is only available in the USA for use legally in ferrets  and in exotic animals (as a research trial). This is a prescription only medication.

How does it work?
So this is going to get sciency (dredging up memory of IVF course at Uni)
The active ingredient in Suprelorin is deslorelin acetate. This is a synthetic peptide that is extremely similar to gonadotrophin-releasing hormone (GnRH). GnRH naturally occurs in the body and controls the release of two important gonadotrophins, luteinising hormone (LH) and follicle stimulating hormone (FSH) from the pituitary gland, two tiny glands that sit in the middle of your brain! GnRH binds to these receptors allowing for the release of LH and FSH. These two hormones are released into the body where they in turn can control the expression of testosterone and estrogen. See my funky diagram below, like it?
 

So basically, GnRH activates two hormones that further activate testosterone and estrogen.
The testosterone make the roosters behave in a rooster way and the estrogen allows for egg laying to occur.

The question would be, why would you insert more GnRH? Wouldn't that cause more testosterone and increase egg laying?

That would be true if GnRH is released in pulses. Normally, we release GnRH in waves. In females, the waves increase just before ovulation and in males the waves are rather consistent, but for both, GnRH increase and decrease all the time.

The implant is different in that this hormone is released all the time, there is no high or low levels of it. When this happens, the GnRH receptors actually stop the release of LH and FSH and in turn, stops the generation of testosterone and estrogen. This in turn, stops ovulation, or egg formation. For the first few days, there will actually be a spike in testosterone or estrogen levels, but the receptors desensitise after that and stop.


What is it used for?
This implant was originally designed for use in male dogs to reduce aggression. However, it has been trialed in several different animals, including; rats, cats, several birds, opossums, otters, lions and cheetahs.

Although it cannot be used on domestic animals in the US (besides ferrets), Zoos in the US are using it to control reproduction in their animals. In some cases, they use the implant for a short time to actually stimulate reproduction!

For chickens, it is mainly used in hens, especially commercial egg layers that have been bred to lay constantly till their body wears out and cannot handle egg laying any longer. These hens often do not moult and continue to lay with no rest period for their little bodies. Providing the implant to them stops egg production and allows them to recover calcium levels and their reproductive tracts to rest and heal.

I have done a bit of web research and have seen this implant used in some roosters, mainly to prevent them crowing. From what I understand though, this may be a bit of a hit and miss. The younger the rooster is implanted, the less likely they are to start crowing. Although they may not develop the magnificent tail feathers that roosters have and may end up looking more like a hen! It may however, be useful in roosters that are aggressive. This may tone down the amount of testosterone and the urge for them to mate with every single hen. It has been done successfully with male turkeys, but haven't seen a proper study with roosters.

How long does it last?
This is partially dependent on the size of the implant used. It comes in two doses, 4.7mg and 9.4mg. Technically the larger dose lasts longer, for approximately 10 months. But there can also be environmental factors that can prevent the implant from working. For some hens, the urge to lay eggs is so great, that the receptor does not shut down, but will still release LH and FSH. This may be linked with daylight and spring "fever". Mostly it seems to work quite well and the lesser dose lasts for approximately 6 months.


For hens, it becomes clear when it stops working. They start laying eggs again!

The chickens can be implanted again if the need arises. The original implant will break up but does not actually break down and dissolve away.

What are the side effects?
It is only day 2 for us with the implant, and so far no side effects with Spot. She did still lay an egg, but we were told that it may take a few days for the implant to work. I think it may take about a week for it to work as the implant would most likely stimulate egg laying for a while before the receptors down regulate (stop working). Plus the patent for the implant showed that this was the case!.

Others have said that the surge in hormones can make their chicken moody (PMS!!) but others have said that their chickens have more energy (since egg laying is an energy intensive exercise!). It has been used in dogs for several years now with no significant reported side effects.

I'll keep this section updated with what I observe with Spot over the coming weeks and I'll note anything significant.


What did my vet say?
As I mentioned before, we took Spot's eggs for her to have a look. The wrinkly and thin shell was apparently a sign of an early uterine infection. Also, the thin shells would have significantly increased her chances of breaking an egg during laying and having a subsequent infection. That type of infection can be difficult to treat. Our vet said Spot at this stage would be a perfect candidate for the implant. The vet also told us that it was often a weigh up between the customer's wishes and if it was worth it for the hen. This was because, the hen was often brought to her with an infection from a broken egg. At that stage, she first has to deal with the infection before the implant can be administered. If the hen does not recover, then the implant would have been a waste for her customers.  But Spot is fit and healthy and we applied the implant before any significant adverse health effects befell her.


How much does it cost?
For my vet, she charged $295 for the larger implant, which included a quick examination and administration of the implant.

I did a quick search, in some vets (administering to dogs) it is about $140 for the small (4.7mg) implant, up to $240 for the larger.  So I guess with the consult, it was about a similar price I suppose.

As a side note, St Louis Zoo in Missouri has them at $30 and $60 respectively, but only for research trials in exotic animals!


I hope this has been informative, I would love to know anyone else's experience with this implant. I also hope that it helps Spot and allows her to have a vacation from that boring business of egg laying. I mean, who wants to be stuck in a nest box when you can be out free ranging?

Update
Spot had her implant on a Tuesday. She laid an egg on Wednesday, but no egg on the Thursday or Friday. I'm assuming the implant has started to work and it took 2 days. I'll note it here that her implant was done on the 17 Oct 2017. Let's see when her next egg will be.

  Day 5 after implant
Spot is acting very moody. She's quiet, not running around as usual and prefers to sleep on the nest box rather than on the perch. Plus she is hanging around Goldilocks, which usually doesn't happen as Goldilocks likes to bully her. Spot is definitely right at the bottom of the pecking order (she was originally) but now she freezes when the Marans come up to her. She's also not avoiding The Boy, normally The Boy will wing dance and she will just hop around to avoid him. Now, she starts screaming if he wing dances her and she doesn't run from him 😕. Poor girl. I suppose having the implant is like having PMS. I'm wondering if she will perk up. She still likes to be the first for food though! That hasn't changed!

  Day 9 after implant
A mini moult from Spot, just a small one, not really noticeable when you look at her, but the evidence is in the presence of white feathers everywhere. And Spot is our only white chicken.


  Day 10 after implant
She's making broody noises and likes to spend time in the nest box. It seems that the hormones are making her think she should be sitting on eggs? I've removed the golf balls in the nest box that she was sitting on, so hopefully it should make it think otherwise about hatching eggs.

  Two weeks after implant
She's still making broody noises, but she's not spending time in the nest box during the day. She runs around outside, but is still subdued and gets picked on by the others (this happened before the implant anyway, so not a big deal). 

  Three weeks after implant
She seems to be full on broody at the moment. She's spending quite a lot of time in the nest box and will sit on any egg she can find. During free range time she will run around for quite a bit, so it seems that she is not quite a determined broody. But this morning, she didn't even want to come out for her breakfast!

One month after implant
Spot has given up on being broody (thank goodness!) but she is still subdued and quiet. At least she joins in with the others during free range time. But I do miss her "me first" attitude, where she had to be the first hen on the scene when there was food, or when I took out the spade, she had to be the first hen to run across the garden to look for the goodies I would dig up. I'm wondering if she will bounce back even more. I'm hoping since she gave up on her broody stint.

Four months after implant
It's February and Spot has been acting more of her usual self since December. She's still quieter than before, but nowhere near as subdued and sulky as when she first got her implant. Her wattles and comb has shrunk, but she's back digging away at the garden, eating heartily and roaming around. She has started to do her usual thing of leaving Buffy's flock to hang with The Boy, but she doesn't seem to like just being by herself any longer (which she used to do quite a lot earlier).I'm glad she's happier.

Update 18 August 2018
The implant has well and truly worn off as we have an egg! No problems with this egg shell, so we will keep her off the hormones for a while. She is much more active off the hormones and not so depressed looking. August in Australia is the last month of Winter, so the days have been getting longer which triggers egg laying in chickens here. For a few weeks, her comb has been getting redder and it flopped over a week or two ago, but her comb is nowhere near as big and floppy as it used it be?

Anyway, we will monitor her egg shell condition and if she shows signs of poor shell formation, it will mean another implant. So the implant for Spot lasted 10 months. I suspect it only lasted about 7 months or so as it coincided with winter, which suppressed her egg laying. But we noticed her being more active and inquisitive the past few months, so I'm glad she had a few months of no egg and being back to normal!

References
Johnson, J (2013) Therapeutic Review: Deslorelin acetate subcutaneous implant, Journal of Exotic Pet Medicine, 22:82-84

Molter, C; Fontenot, D & Terrell, S (2015) Use of Deslorelin acetate implants to mitigate aggression in two adult male domestic turkeys (Meleagris gallopavo) and correlating plasma testosterone concentrations, Journal of Avian Medicine and Surgery, 29(3):224-230

Harrenstein, L; Petritz, O; Asa, C & Rhodes, L (2015) GnRH agonists in avian and exotic patients: Opportunities and Challenges, ExoticsCon 2015 Main Conference Proceedings

US Patent: 6, 337, 318 B1,  Trigg, T; Walsh, J and Schober, P (2002), Sustained GnRH peptide-release formulation


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