What does jet lag have to do with whelping puppies?

By Carol Beuchat PhD

If you've done much travel by air, you've probably experienced jet lag, that awful feeling of fatigue, disorientation, and brain fog that leaves you feeling like crap just before a job interview or your best friend's wedding. You're hungry at the wrong time, can't sleep, and try to self-medicate with coffee or donuts or chocolate.

You probably know jet lag has something to do with your internal clock being out of phase with the time zone you're in, and that things will be better in few days. (Ugh, just in time for you to fly home to a different time zone).

Jet lag is definitely physiological. Your body expects things to happen at a certain time of day, and your internal (circadian) clock monitors whether it's light or dark outside to keep everything running on time. 

A key player in keeping the parts of your body in sync is a hormone called melatonin. When melatonin levels are high, your body knows it nighttime. Melatonin secretion is suppressed by light, so you know it's daytime when melatonin levels are low. The cycle of light from daytime to nighttime is called your photoperiod.  

This isn't just a clever way for people to keep track of time when they travel. It turns out that all animals and even plants take their cues from the photoperiod to know not just when to sleep and when to wake up, but also when to molt, migrate, hibernate, and all the other things that need to happen at a particular time or season. 

This video from Khan Academy about photoperiods talks about plants, but the basics apply just as well to animals (and dogs, and you), so it's worth watching. Especially pay attention to the effects of light at the wrong time of day, like a blast of light when your body is expecting nighttime. (At about 7 minutes it starts talking about mRNA and gets geeky fast, so you can skip the end.)
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(Khan Academy video: Watch from beginning to about 7 minutes.)

A critical point here is that light at a time when your body is expecting it to be nighttime really messes things up. In essence, that period of light - even very short, very dim light - throws everything out of whack. When your body gets that blast of light, it decides it must be daytime and adjusts the internal clocks to synchronize with that new time. All the things in your body that run by the clock will be messed up until there are several days of a normal photoperiod that your body can sync to.

This blast of light at the wrong time is just like what happens in jet lag. Your internal clock is on the wrong schedule, and the consequences are predictable and not pleasant. This is also why you're not supposed to check your email in the middle of the night; the brightly lit screen of your phone resets your internal clock, leaving you feeling not your very best the next morning.

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What does jet lag have to do with whelping puppies?

Dogs rely on external light cues to keep track of day and night, just like you (and plants) do. If you keep a fairly regular schedule, your dog knows when you will be home from work, when it's time for dinner, and when it's time to get up in the morning.

Dogs tend to go into labor and whelp their puppies in the middle of the night, but not always. For the daytime whelpers, it's likely that they haven't had a reliable photoperiod in the days and weeks coming up to the end of gestation. They whelp during the daytime because their circadian clock isn't synchronized to the real photoperiod.

There are two problems with whelping in the daytime.

First, the bitch's melatonin will be suppressed by light unless she's in a very dark room. The strong uterine contractions needed to expel the puppies depend on the interaction of melatonin with oxytocin. Without melatonin, the uterine contractions aren't strong enough to expel the puppies quickly, the classic case of uterine inertia. (How do you know if your whelping room dark enough?)
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Prolonged whelping times result in oxygen stress in the puppies as the store of oxygen in the placenta and blood of the fetus is depleted. The result is stillbirths and puppies that have had inadequate oxygen (hypoxia) and are born with airways full of fluid because breathing was stimulated while still in the amniotic sac. 

The second problem when melatonin is suppressed in the bitch during whelping is that uterine inertia is likely to result in oxidative stress, when fetal metabolism produces free radicals that can damage tissue and DNA.

​Antioxidants produced by the body and in the diet typically mop up excess free radicals to prevent damage, but the newborn puppy does not produce its own yet and relies on mother's milk to supply what it needs. But melatonin is one of the most effective antioxidants, and its secretion is blocked when the bitch is whelping when there is light. So newborn puppies are likely to have a free radical load and inadequate antioxidants to prevent damage. ​

The result is that newborn puppies that experience hypoxia during birth might suffer tissue and DNA damage as soon as they enter the world. We know a lot about the effects of inadequate oxygen during birth in human infants. These can be severe and also last a lifetime. If inadequate oxygen has similar effects on a puppy during birth, we should expect some serious consequences to the health of a puppy as well. (Consequences to puppies of inadequate oxygen during birth)

While uterine inertia and its consequences for stillbirths and distressed puppies are well-documented in dogs, very little is known about the consequences to health, either short or long term. We should certainly expect to see some of the same disorders in dogs that occur in humans. In fact, several health problems in dogs could very well be a consequence of exposure to hypoxia at birth, but research has focused on identifying genetic associations with little success. Renal dysplasia, seizures, and cancer are three obvious candidates for disorders that are likely linked to perinatal stress. (Key things you should know about whelping that you probably don't)

The point here is that we might think the effects of turning the lights on and off are inconsequential, there could be profound effects on the physiology of a bitch during gestation and whelping, and we might never connect the light scheme with the short and long term health of her puppies.

There are some simple fixes for this. Just like you have a regular "bedtime" for your toddler, after which lights are out, we can establish similar routines for our dogs, especially the breeding females.

We can avoid the suppression of melatonin during whelping with a bit of planning ahead of time to set up the whelping room to be completely dark and invest in a few inexpensive infrared video camera so we can keep an eye on things. In my experience, bitches whelping in total darkness give birth to their puppies quickly, with no stillbirths or even puppies that are distressed. The time between puppies is 10-20 minutes, so even a large litter can be whelped in an hour or two.

Most of us have personal experience with the significant effects of travel that disrupt our circadian timing. We can appreciate how a disrupted schedule might wreck havoc on her physiology of a pregnant bitch as well. To prevent this, we can put our household lights on timers to provide a predictable day and nighttime schedule. We can also provide a very dark room for whelping so melatonin can play its essential role in the control of uterine contractions during whelping.

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To learn more about the important effects of light during pregnancy and whelping, check out ICB's live-lecture course,

"From Breeding to Weaning: The Critical Importance of Light". 
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Also visit our Facebook Group,
ICB Uterine Inertia and Neonatal Mortality in Dogs.

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