I bet it's something that the chickens are eating or being fed. Eating - they could be eating bitter greens. Being fed - they could be being fed bitter fabricated vitamins. Eggs will take on the taste of what you feed the chickens. Lately I've been feeding my chickens cayenne pepper and as soon as the garlic from the garden is ripe I want to add garlic - sort of to get the taste of huevos rancheros with only egg yolks
But really - the chickens LOVE these herbs and they're really good for them. Chickens that have stopped laying have been started up again with cayenne.
I've analyzed some of the best organic soy free chicken foods and in all of them most of the ingredients come from vitamins. If the feed is old or stale or bugs have been in the feed - that could do it too.
My chickens' egg yolks are almost sweet - but I feed them mostly insects and raw meat and sprouted organic seeds - they eat an all raw diet. No other fillers. It's not the grains that would make the egg yolks bitter. Corn is the main ingredient in most feeds - (except if there the protein comes from soy - which is really bad for chickens) and corn won't make a chicken's egg taste bitter. Regular chicken food is highly heated so the ingredients can go rancid. That might be it too.
If you got your eggs from the same farmer feeding the same thing the two possibilities are: 1. If free ranging some new bitter green is what they had to forage on. 2. There was something wrong with the feed this time.
