They say that New York is the “City That Never Sleeps” but having grown up there, I assure you there are some quiet neighborhoods that tuck in for the night. Las Vegas on the other hand seems to have the lights on all the time. I just returned from a four-day jaunt to Sin City for the USA 7s Invitational, an international rugby tournament held under the lights at UNLV’s Sam Boyd Stadium. It was a weekend of great rugby, old friends and the complete upheaval of my inner clock. We’ve been home for over a week and I still can’t seem to get my sleep/wake cycle back in order. The casinos in Vegas are notorious for confusing the senses to keep you awake and feeding money into the slots for hours at a time. With gaming floors that are lit up 24/7 and restaurants that serve Budweiser and buttermilk pancakes all day, its no wonder we never know what time it really is (and when in Vegas, do you really care?). This constant bombardment of photons on my retinas designed to increase the House’s take was a timely reminder of another way we can use lights to alter physiologic cycles to produce a desired end result.
People can give birth anytime of year, with little variation in number of births from month to month but naturally, horses typically foal in the spring and summer
. Ever wonder why that is? Its nature’s way of ensuring that foals are born when the conditions are most favorable; warm weather and ample pasture for grazing. But we all know someone who has had a foal in the winter months, and in some breeds its advantageous to have your foals born in the early months of the year. So how do we get around Mother Nature? To get the best answer I went to an expert. Dr. Lauren Greene VMD DACT of McGee Equine Clinic
in Townsend, MA. Dr. Greene is a veterinarian who specializes in reproduction (aka: making babies). Boarded by the American College of Theriogenology, in addition to veterinary school, she completed a two-year residency at the University of Pennsylvania, New Bolton Center’s Georgia and Philip Hofmann Research Center for Animal Reproduction. When asked about the mare’s reproductive cycle and how it changes with the seasons, here’s what she had to say:
Dr. Lauren Greene and a patient.
“Unlike human women who have menstrual cycles and are sexually receptive throughout that cycle, horse and many other animals have periods of receptivity known as estrus. The estrous cycle follows a pattern with periods of estrus, also known as heat, interspersed with periods known as diestrus, where mares are not receptive to the advances of stallions.
Horses are seasonally polyestrus long day breeders. This means that there are certain times of the year when they are not having these heat cycles. Normally horses cycle during days of long daylight and are reproductively quiet (anestrus) during days of short daylight-fall and winter. The majority of horses will enter an anovulatory season (with no distinct heat cycles present) during the fall when natural daylight decreases. This is known as the fall transition. Conversely, during periods of lengthening daylight (naturally in the spring) horses will begin cycling again- known as the vernal (or spring) transition. In natural conditions this ensures the foals will be born during the spring and summer months.
Daylight it believed to be one of the key factors in determining cyclicity in horses. It is widely believed that the retinas of the eyes transmit light information to the pineal gland within the brain, which responds to darkness by releasing melatonin. Melatonin then acts on other parts of the brain (hypothalamus and pituitary) to down regulate the ovarian activity.”
If melatonin sounds familiar, it’s because it gets a lot of press when we talk about sleep aids in people. Melatonin is a natural hormone that help regulates our sleep/wake cycles by making us feel less alert and sleeping when it gets dark outside, our body’s way of telling us to go to bed. Too much light leads to low levels of melatonin and sleep problems. Pills containing melatonin have even been prescribed to treat insomnia. But we’re talking about mares here." “In Indiana, most mares kept under natural conditions will cycle from roughly April through October. Unfortunately many breed registries such as the Jockey Club and the US Trotting Association set January 1st as the official birthday for all foals regardless of their actual birth date. Because of this many breeders try to have their foals born as close to January 1st as possible.”
This date is set to make it easier to calculate a horse’s age when it comes to racing, where horses only race against other horses of the same age. So a foal born on January 1st 2012 and a foal born on December 31st 2012 are technically the same age and would have to race in the same group as 2 and 3 year olds, but the first foal is nearly 12 months more mature, bigger, stronger and faster. In horse years this makes a huge difference!
“Because of this, and the fact that mares are pregnant for an average of 340 days, the breeding season for many farms starts on February 15th. Again, remembering that naturally many mares will normally start cycling in April there is a bit of a discrepancy here.”
So, how do humans affect this natural pattern?
"It has been established that by altering the amount of light that mares are exposed to, we can mimic the naturally occurring transition periods. By adding additional hours of light a mare is exposed to, we can trick her body into thinking that the daylight length is increasing, thereby stimulating her to start cycling before she would naturally.
"This technique is referred to as “putting a mare under lights.” The length of light is extended to a total of 16 hours by providing artificial light, typically by adding light at the end of the day before dusk. Light must be added for 8-10 weeks for a mare to respond, therefore for a desired start date of February 15th, we must start adding this light December 1st. Mares can be housed individually in lighted stalls with lights on from 4:40pm to 11:30pm, or they can be group housed in a lighted paddock. The amount of light should be a minimum of 10 foot candles, which in normal terms means enough light to comfortably read, which roughly equates to one 100 watt bulb in a 12’x12’ stall.”
So there you have it. The same physiology/technology combo that casinos use to keep us up all night gambling away our life savings can be used to alter the mare’s reproductive cycle, giving us more control over when our foals are born.
Special thanks to Dr. Lauren Greene VMD DACT for her contribution!
If you live in central Massachusetts or southern New Hampshire, McGee Equine Clinic
can assist you with all of your equine veterinary needs including advanced reproduction techniques.
This past Saturday night was the 35th Anniversary Gala for the Philadelphia Women’s Rugby Club
, a team I was proudly a member of from 2002-2006 while living in Philly during vet school. Rugby is a rough sport (yes girls can play too, and yes we play by the same rules as the boys, no helmets, no pads, just knee socks and a mouth guard) and during my time with the Philly Women, in addition to making it to Nationals twice and being named to a few all-star teams, I also dislocated my right shoulder, broke my nose (for the 3rd and 4th time) and had more than one black eye that made my boyfriend afraid to be seen in public with me. Ruggers know about pain, and pain management. And the one thing I was thinking about on Sunday morning, after a long night of reminiscing with old friends, dancing in 4” BCBG metallic blue stilettoes (a far cry from my old brown clogs) and one too many Yeungling lagers (you can’t get it in Indiana) was pain management.
When you look at the Pain Relief aisle of your local Walgreens or CVS, for pills containing the anti-inflammatory drug ibuprofen there are a million and one choices: joint & muscle pain, back pain, childrens’ pain, arthritis pain, menstrual pain, migraine pain and oral pain. And I’ve always wondered; How do the drugs in this ibuprofen pill treat just my back pain? What makes that ibuprofen pill just go to my headache? But when you read the fine print on the label, many of these pill contain the same concentration of the same drug, no magic road map to your pain, its just that they are marketed for certain ailments (and usually the arthritis pills have an easy to open cap and the childrens’ pills have a child-saftey cap). And while we tend to use them interchangeably, most of us understand that ibuprofen is not the same as aspirin, which is not the same as naproxen (Aleve®), making the choice even more confusing. Luckily in the horse world we don’t have so many choice. Pretty much just two dominate the field: phenylbutazone (Bute) and flunixin meglumine (Banamine®).
Their innovative marketing techniques aside, the most misleading part of the previous paragraph is how the section in the pharmacy is labeled: Pain Relief. I think that it is very important to understand how these drugs work and why we prescribe them. Yes, they do relieve pain, but that is a secondary benefit of their main focus: control of inflammation. This is why we call them Non-Steroidal Anti-Inflammatory drugs, or NSAIDs, which include phenylbuazone, flunixin meglumine, firocoxib (Equioxx®), ketoprofen and carprofen (Rimadyl® for our dogs). They are “non-steroidal” because this group does not contain corticosteroids (dexamethasone) which also stop inflammation but also affect the immune system. They are anti-inflammatory because they stop the affects of inflammation by blocking the production of prostaglandins, one of the final products of the inflammatory pathway. Prostaglandins are produced by many tissues in the body as part of normal functions like blood flow to the stomach and colon lining and the kidneys (remember this point, it’ll come up again later).
So are Bute and Banamine® the same? Not exactly… Banamine® has been shown to be more effective in relieving gastrointestinal, soft tissue and systemic inflammation and pain. Think colic, eye pain, sepsis. Bute on the other hand is more commonly used for musculoskeletal inflammation and pain (muscle pain, arthritis, tendon/ligament injury).
So now that you have an idea of which drug to give when, the next questions are: How do I give it? How much? and How often?
Both Bute and Banamine® are prescription medications and should be obtained from your veterinarian to treat a specific problem on a specific horse. That being said, we all know it lives in every medicine chest of every farm out there. Bute comes in an injectable solution that should only be given intravenously (IV) by an experienced person, namely your veterinarian. It is very irritating and if it gets outside of the vein or in the muscle it can cause severe inflammation, necrosis and sloughing of the tissue.
The safer formulations for laypeople to use are the oral forms, powder or paste. Make sure you read the label to know how many grams are in one scoop of powder or one turn of the dial on the paste tubes (its usually 1g). Banamine® also comes in injectable and oral formulations. The injectable form can be given IV (again make sure you have an experienced hand giving the injection) or intramuscularly (IM). I tend to discourage people from giving Banamine® IM because it has been closely associated with Clostridial myositis, a severe and often life threatening bacterial infection in the muscle. You can also give the injectable formulation orally! Yes, draw the same amount from the bottle that you would have giving IV or IM and squirt it in their mouth! It has similar oral bioavailability, which means its absorbed just as well. NB Injectable Banamine® is VERY bitter (trust me, I’ve accidentally gotten some sprayed in my face) and your horses will appreciate it if you mix it with applesauce or molasses before giving it orally. Banamine® also comes in a paste and granules to be given orally.
The label dose of Banamine® is 1.1mg/kg BID which is a fancy way of saying that a 1000lbs horse should get ~500mg (10cc or a 1000bls dose of paste) no more than once, every 12 hours. Bute’s label dose is 4.4-8.8mg/kg BID. Translation: a 1000lbs horse should get between 2 and 4 grams no more than once every 12 hours. It is very important to note that these volumes are based on body weight and are for a ONE THOUSAND POUND horse!!! If your horse weighs more or less than 1,000lbs, then these doses are not right for you! Example, a 500lbs pony is half the weight of a 1,000lbs horse (get out your calculator and check if you don’t believe me, but my mother will tell you I did very well in math as a child), therefore a 500lbs pony should receive HALF the dose of a full sized horse. I know, I know “But human medicine gives every adult the same amount of pills whether you’re a 90lbs gymnast or a 300lbs sumo-wrestler.” This doesn’t make sense to me, and I hope someday an MD will give me a good explanation as to why. And notice how I say “no more than once every 12 hours?” I didn’t say “twice in a day” because to some people that means, once, and then if it doesn’t work, another dose 20min later. And giving your 1000lbs horse 10cc of Banamine® and then another 10cc an hour later is the same as giving them 20cc at once, and you have overdosed your horse.
So why is it that I’m so crazed with appropriate dosing? Because, being an internist, I get to deal with the sickest, most critical cases and I hate seeing ones that could have been prevented. While Bute and Banamine® are wonderful drugs that help us keep our horses comfortable and inflammation free, they are not without side effects. Remember how I said that there were “normal” functions of prostaglandins and how that fact would be important later? Well the time is now. Prostaglandins regulate blood flow to the kidneys and to the lining of the stomach and colon (specifically the Right Dorsal Colon). When NSAIDs are given, they block all prostaglandins, both normal and inflammatory, so you get decreased heat, swelling and pain but you also get decreased blood flow to your kidneys and gut lining. Now in a well-hydrated horse that is getting an appropriate dose for a short period of time, this usually won’t be a problem. If your horse is dehydrated, getting excessive doses or even normal doses but for long periods of time, you will see the harmful side effects. Gastric ulcers, colonic ulcers and renal failure. These can lead to colic, diarrhea, excessive drinking/urination and many other signs associated with NSAID-toxicity. This is a treatable condition but it can become so severe that no amount of treatment can repair the damage.
It’s not that we should never use these medications; we just need to know the appropriate doses and dosing intervals to make their use as safe and effective as possible.
Believe me, Sunday will not be the last time I reach for the ibuprofen (only at the labeled dose and I’ll keep hydrated with plenty of water) but I do so cautiously (and swear to myself I will never run down Walnut St in 4” heels in freezing temperatures again!). And the safest, most cautious way to administer NSAIDs to your horses is to do so under the direction of your veterinarian. Only he or she knows the right type and the right dose of NSAID for your horse based on the specific problem at the time.
Horses loaded up and ready for the long haul!
We all know that air travel often leads to the common cold in people, but can the same thing happen to our horses in the trailer?
Yesterday, as I boarded a plane in Indianapolis for a trip to the East Coast (part work, part play), I realized too late that I had not packed my Airborne. As the doors closed and the cabin pressurized I heard the sounds that give every traveler that sinking feeling; coughs, sniffles and sneezes. I knew that no amount of in-flight complimentary orange juice would help, I was going to get a cold. It happens countless times every day all over the world, passengers, tired and stressed from the airline experience, mixing germs in the ultimate petri dish, a crowed plane.
All this thought of impending illness reminded me of one of the reasons for my trip east. The data for the final research project that I performed during my residency was analyzed and all that was left was to write the paper. Yes, I know, 18-months is a very long time to wait, and yes, I had probably forgotten more about the project than I knew in the first place, but sometimes science is slow, or sometimes researchers get busy with other things (moving thousands of miles, new jobs, new companies, puppy raising, wedding planning) and that little project gets forgotten. We had waited too long and this trip home was a perfect opportunity for my co-author and I to lock ourselves in an office and just get it written. The project looked at tracheal mucociliary clearance, a very important factor in the development of transport-associated pleuropneumonia in horses, or “shipping fever.”
You see, humans aren’t the only ones who get sick after travel. Shipping fever is a well-described syndrome in horses, cattle and any other animals that are packed in trailers and sent around the country. Shipping has been shown to increase stress markers, such as cortisol, in animals, which can lead to a decrease in immune function. In horses we recognize that tracheal clearance plays an important roll. The lining of the trachea is covered in microscopic finger-like projections called cilia (from the Latin word for eyelash). These cilia beat synchronously to move tiny particles of dust, debris and bacteria up the trachea, away from the lungs, where it can be coughed up. When we ship horses, we commonly tie them in some fashion so that their head is in an upwardly fixed position. Research done by Dr. Sharanne Raidal of the University of Sydney has shown that this prolonged upward fixation of the head and neck significantly decreases the rate at which particles move out of the trachea and that this leads to a significant increase in the number of bacteria and inflammatory cells found in the trachea and lungs. Combine this with decreased immunity, bits of hay and dust from the hay net being blown around in front of their face, not to mention the pollution of a diesel truck and its no wonder some horses develop pneumonia after shipping. The study I performed, the one I still had to write up, aimed to prove that pre-treatment with clenbuterol, a drug known to increase tracheal clearance, would prevent shipping fever…sadly it did not work as we hoped. It did increase the rate of clearance but this small increase was not enough to combat the barrage of insults that batter the respiratory system during transport.
Millions of finger-like projections called cilia, beat in time to move debris and bacteria up the trachea and away from the lungs. These cilia can be easily damaged by viruses and the stresses of shipping, leading to pneumonia.
So what can be done to protect our equine travelers? Buckets full of OJ at each rest-stop? Giant sized Flinstone’s Vitamins? The solutions may be a bit simpler than that. First things first, don’t ship sick horses. Horses that are already compromised or are recovering from a recent illness are more likely to become sick after shipping. Upper respiratory tract viruses (like the Flu or Rhio virus) can blunt tracheal cilia. This damage can take weeks to a month to heal, leaving that horse even more susceptible. But once you have your healthy horses on the trailer, try to decrease the amount of particles their respiratory tract has to deal with. Ensure the trailer has good ventilation (especially in the winter when we tend to shut up all the windows, a few horses’ body heat in a small space will keep them warm). Debris in the air can be controlled by soaking the hay for 5-10 minutes before hanging the hay nets (soaking any longer can leach out some of the sugars and decrease the nutrient values, which may not be a bad thing if your horse is an “easy keeper”), or ship them without hay at all. It may not be good for their attitude but it can save their lungs. Next, let gravity lend a hand. Another study done by Dr. Raidal showed that the ill effects of the upwardly fixed head position can be negated by allowing the horse to lower its head to the ground several times throughout the trip. So when you stop for gas, remove the breast bar and let your horses have their heads, they may be able to empty out some of those bacteria that have been building up.
Unfortunately no matter how diligent we are, no matter how much OJ we guzzle at the airport, after a long trip some people and some horses will get sick. The best thing we can do for these cases, is recognize the illness and begin treatment as soon as possible. Taking your horses temperature several times a day and monitoring their attitude and appetite closely for the few days after a long trip can help you pick up on the early signs of illness. If you do have concerns about one of your travelers, contact your veterinarian. He or she can do a thorough assessment of your horse and may recommend blood work to look for signs of systemic inflammation. Many times, pneumonia in horses, if treated early, can be resolved quickly without too much time out of the saddle. However, left untreated, bacterial pneumonia can become very severe, require hospitalization and even be life threatening. In fact, studies out of Japan show that shipping fever is one of the leading causes of morbidity and mortality in racehorses.
Don’t let your horse fall victim to this potentially terrible disease. Take precautions before, during and after shipping to keep your friends healthy and ready to go on your next adventure!