Just chiming in re the egg yolk.
I have been doing the weston A price diet myself (all whole traditional foods). The recommendation for the yolk is that i MUST come from a chicken that grazer on pasture. You know a good yolk when it's orange (not yellow). The egg is boiled for 3 mins so that the enzymes are still intact and able to be digested. the whites are discarded.
A baby's gut is actually better equipped to supply enzymes for digestion of fats and proteins rather than carbohydrates (they only have one carbohydrate enzyme which is lactase to digest lactose).
If the yolk comes from a properly raised chicken (roaming the grass, eating bugs) it will contain loads of good cholesterol and omega 3 long fatty acid chains that are also in mother's milk. It's great for brain development. It also contains a high level of choline, another critical nutrient for brain development.
Also, the salt must be pure, unrefined sea salt or celtic salt (only use a tiny pinch). It's full of a variety of trace mineral. Salt is necessary to activate the formation of glial cells in the brain, cells that make connections and help us think faster.
Plain white table salt is of no use and can be dangerous because it's lacking in minerals.
The suggestions of many pediatricians to introduce rice cereal, in my opinion, is far more dangerous than egg yolk. A baby's digestion is not equipped to handle cereals before the age of one. Many say hold off until age two.
There have been various studies done on the feeding of pasture egg yokes. One study published in the June 2002 issue of the American Journal of Clinical Nutrition compared the nutritional effects of feeding weaning infants 6-12 months of age regular egg yolks, enriched egg yolks, and an otherwise normal diet. The researchers found that both breastfed and formula-fed infants who consumed the egg yolks had improved iron levels when compared with the infants who did not.
http://www.westonaprice.org/childrens-health/nourishing-a-growing-babySo, although many doctors give varying degrees of advice, i guess everyone has to do their own research and find out what they agree with and what they're comfortable with. I've been studying nutrition for a long time and have seen the benefits of eating the traditional, organic, whole, from the farm foods our great grandparents grew up on. I am healthier than ever and i got pregnant quickly after 3 months of changing my diet. and my pregnancy and delivery were both super easy!
The Weston A. Price foundation is a good place to start if anyone's interested. Or Sally Fallon's "Nourishing Traditions."
But that's just one mama's opinion! Like i said, everyone has to find what they're comfortable with and what they believe is best for them and their family.