Effectiveness of Extra-Dietary Calcium Supplements in Improving Egg Shell Quality and the Influence of Added Phosphorus

MOST eggs are laid between 9 a.m. and 1 p.m. each day with an average approximating 11 o’clock. Ovulation of the successive egg usually occurs in 15 to 75 minutes and is followed by its normal sojourn through the infundibulum, magnum and isthmus before it reaches the uterus. Thus, if oviposition occurs at a time approximating the average then shell formation per se will not commence until after 4 p.m. that afternoon. Assuming the bird is on a 14 hour lighting schedule then less than half of the 20 or so hours used in shell building is available for direct use of the consumed calcium. It has been shown that the hen consumes a proportionately larger amount of the day’s feed when the ovum is in the magnum than when it is in the uterus (Morris and Taylor, 1968). If the sole source of calcium is from the diet then…