Injection of nutrients in eggs during incubation is a novel technique that is gaining ground in experimental circles as a means of enhancing chick quality at hatching and in broiler life performance. However, not all attempts are crowned with success. Such an example is a recent study in the U.S., where a novel form of vitamin D was injected in ovo at day 18 in anticipation of higher bone mineralization at hatching and (or) day 21 of life.
Vitamin D is involved in calcium metabolism, and previous research has shown enhanced bone strength (mineralization) from feeding higher levels of vitamin D supplements. Nevertheless, in this case, in ovo injection of a vitamin D metabolite did not affect bone quality at hatching (perhaps because the chick could not find the extra calcium and minerals in the constrained place of an egg). The same lack of response was observed later in life, perhaps because this vitamin D metabolite was not enough to sustain high blood levels after hatching -- vitamin D metabolites are not stored at any appreciable amounts.
Apparently, a different approach is needed; perhaps a combination of vitamin D and certain minerals that could be used in ovo, or higher dosages in ovo along with a lipid source to allow for sufficient accumulation in (enhanced) fatty tissues for use later in life.