I am new to chickens and struggling with this very issue.
In late January this year I got my first chickens. I got 5 hens: 2 Wyandottes, 2 Cream Legbars, and 1 Rhodebar. They were 4 to 6 months old when I got them. The first 3 months I had them were fantastic. They began laying almost right away and once they were all laying we were getting about 28 eggs per week which was great. I enjoy their personalities and taking care of them. They are in a 100 sq. ft pen in my horse barn. I use pine shavings for litter and I pick the pen out daily. It only takes a few minutes and I am used to caring for horses so I keep the chickens in a similar way. Except my chickens don't go outside. I was planning on building an outdoor pen but I started having problems so did not go ahead with that yet.
The problems began about 3 months after we got them. One of the Wyandottes slowed down laying then one of the Cream Legbars slowed down too. Their combs became pale. I looked online for info (I don't have a chicken vet) and read about the possibility of worms and the need to deworm. Although my hens don't go outside, the person I got them from free-ranged them so it was possible they were exposed to worms.
With all the disparate information and opinion online it was hard to ascertain what product to use and how to administer it, so I called my friend who has a lot of chickens. She said that she had never dewormed her chickens and they are fine and she did not recommend "dousing them with chemicals". So I did nothing which I now regret. Then the two hens stopped laying altogether and the Cream Legbar became lethargic. At this point I knew I had to do something. I did some more reading online, and read that injectable cattle ivermectin administered orally by syringe .2 cc per bird would work. I drove to the feedstore and picked some up and we did the lethargic Cream Legbar. She was dead the next morning, so either the worms dying off killed her, or she was about to die anyhow. She was very weak by that point. It was on Sunday and I didn't think about sending for necropsy (another regret).
I did then find a vet who would look at fecal samples from my other chickens and the vet's finding was they were full of roundworm eggs. We tried dosing them with ivermectin by syringe but had trouble always getting them to open their beak and sometimes they would shake their head and send the dose splashing and then what, as you couldn't know how much has actually gone in. By then the first Wyandotte was losing about 10 feathers per day, comb still pale, and the second Wyandotte started losing about 100 feathers per day. I bought Gail Damerow's Chicken Health Handbook and it said I could use the injectable ivermectin dissolved in the drinking water at 4 cc per gallon for 2 days. After doing that the second Wyandotte immediately stopped losing feathers, the combs got red, and everyone seemed brighter and way more active. After two weeks I had the fecals rechecked and there were no eggs. But then three weeks after that she is losing feathers again and the comb is pale. The two Wyandottes are not laying and the other two chickens vary from laying well (6 eggs a week) to OK (3 to 4 a week).
After reading this thread I ordered the 60 ml bottle of Valbazen last night from a US kennel supply and am hoping it will ship to me in Canada. Assuming it does and I can treat them successfully by oral syringe, do I need to repeat in two weeks? Then should I strip out the litter from the pen and completely replace it? I'm guessing it could be full of eggs? If the Valbazen doesn't come I'm not sure what my next step should be.
I wish I knew exactly what to do. Chickens seem SO much more complicated to care for than horses!
