The Roving Rototiller

Thursday, June 2, 2011


When you've got more eggs you want to hatch than broody hens willing to sit on them, it's inevitable:  you will buy an incubator, and try your hand at setting the things artificially.  During a long dry spell recently, when none of my previously-reliable hens was going broody and "special eggs" were piling up on the counter, I too fell prey to the temptation to Do Things Myself.  I researched models, read through reviews, checked the Backyard Chickens Forum (try it, it's fun), and finally settled on one by Brower.  And so began another chapter in my book of Learning Experiences.

It's a good incubator.  I firmly believe that.  However, it and I are just not getting along.

That first round, I set a total of thirty-four eggs.  Six failed to develop, which was not too terrible a fertility rate, really:  twenty-eight out of thirty-four is just over eighty-two percent fertility, and even a broody hen can be happy with that.  The incubator whirred along, its heating light flickering on and off as needed, thermometer reading a steady 99.5 degrees F and hygrometer holding between 50 and 55%.  The automatic turner trundled, gradually shifting the eggs to and fro.  Candling at day 10 showed good development in all of the eggs, including movement.  To every appearance, everything was going along just fine.  Day 18 arrived, and I hiked the humidity, detached the turner arm, and settled down expectantly.  Day 21 dawned, the day of hatch . . . and nothing happened.

Day 22.  Nothing.  Growing edgy, I candled again.  To my dismay, ten more eggs were dead at varying points of development.  Of the rest, eight showed movement, five were fully developed, three were highly suspicious, and two--surprise!--had pipped internally.  I put the live ones back in the incubator and kept my hands firmly to myself.

The next day, two eggs hatched.  The chicks showed evidence of delayed development, but were vigorous enough.  Over the next three days, we got a slow but fairly steady hatch of four more eggs.  And that was it.  The rest were dead.  At day 30 I gave up, candled the lot, satisfied myself that they had died, and threw in the towel.

So what went wrong?  I'm putting the pieces together.  These eggs were from hens that had given us a good hatch rate before under broodies, so the problem wasn't in the eggs themselves.  Delayed hatch means delayed development, and that means that the incubator ran at too cool an average temperature the whole time.  But if a low setting was the only problem, we should have had a lot more hatch:  delayed, yes, but hatch.  The second big clue is the occurrence of scattered egg deaths at varying stages of middle to late development.  While even the best hatch will always have a few late quitters, ours were a huge percentage of the batch.  That's evidence of temperature fluctuations in excess of what the embryos could handle.  I did see temperature jumps and drops during incubation, and once or twice grew desperate enough to alter the setting.  Since the thermometers were proven inaccurate, what were the real numbers?  Did I screw things up by opening the unit too often or messing with the dial?  Why did the temperatures change anyway?

To try to answer these questions, I bought a Brinsea Spot Check, which is a digital thermometer with a probe designed to be put inside the incubator and provide a fairly accurate reading on temperatures.  It disagreed firmly with the other thermometers, reading nearly a degree and a half lower.  Based on the performance of the hatch, I am inclined to believe it.  I did some more reading and decided that another part of the problem was the cool temperatures in the house.  This incubator performs best at a room temp of 70 to 85 degrees F, and our house has been in the sixties, which could have caused it to lose too much heat.  With the help of an insulating blanket, though, the unit is rated down to 55 degrees.  We also had a heat wave and a cold snap during incubation, both of which affected the room temperature and caused it to range between 58 and 75 degrees.  That can't have helped at all, but the incubator is already in the room least affected by outdoor temperatures.  Short of putting it in the coat closet, I can't protect it further from changes in room temperature.  For now I think I'll hold off on that coat closet.

I accept that an incubator can't hold a temp at bang on the target, 24 hours a day; there is going to be some amount of temperature flux during even optimal operation.  I just wish I knew what the safe temperature range was, but that is probably something I will have to learn as I go.  The incubator is clean, disinfected, and ready to go again, now wearing a cute little insulating jacket made of a double layer of bubble wrap, and containing a small bag of water to act as a heat sink to smooth out changes in temperature.  I am collecting data points like crazy, checking temps several times a day and watching them rise and fall at unexpected times.  I am starting to think that the incubator has warm and cool spots, despite the manufacturer's best efforts.  I am also starting to think that I should have stuck with the broody hens.  You can't check their temperature twenty times a day--they bite.

So the days roll on, the incubator running empty on the kitchen table, as I search for the setting that will provide a happy middle ground and, barring unforeseen weather weirdness, get us a better hatch.  I sure hope I find it soon, because the eggs can only wait so long.  At the end of this week, I will have to cross my fingers and try again.

1 comment:

  1. A hen wouldn't keep them at a constant temperature. Some are near the edge of the nest, and she leaves it sometimes. The max would be her body temp, but the mins and duration would vary. Complications ensue!