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Two experiments were conducted to determine the extent to which performance and egg shell quality might be influenced by dietary calcium level, source and particle size. In the first experiment of 48 weeks duration, Hy-Line 934-E hens were fed five particle sizes of limestone (fine, medium and coarse ground; chick and hen bits) at either 2.5, 3.0 or 3.5% dietary calcium level. Production, feed efficiency and egg weight were not significantly (P < 0.05) affected by treatments. Egg shell breaking strength was significantly (P < 0.05) influenced by calcium level and a trend was evident for increased shell strength with the larger particle sizes. Percent checked and cracked eggs were significantly (P < 0.05) lower for hen bits. No differences were observed for calcium levels. Definite trends for higher specific gravity of eggs with increasing calcium level and larger particles were observed.In the second experiment, which was 52 weeks duration, Babcock B-300 hens were given the following treatments: fine ground limestone (FLS); Cage-Cal, mixture of pullet and hen size limestone (CC); and combinations of 1/4 FLS and 3/4 pullet or hen size oyster shell (POS, HOS) or limestone (PLS or HLS). Egg production rate was not significantly (P < 0.05) affected by dietary treatments. Feed efficiency of hens fed HOS was significantly (P < 0.05) improved over those fed CC or POS. Egg weight was significantly (P < 0.05) greater for hens receiving POS. Egg shell breaking strength was significantly (P < 0.05) greater for CC as compared to PLS or HLS. Percent cracked and checked eggs was reduced with HOS and HLS. Percent soft shelled eggs was greatly reduced with the feeding of HOS. Based on prevailing prices for eggs and feed, HOS proved to be the most economical form of supplemental dietary calcium. ABSTRACTA total of 25, 992 eggs were examined during a three year study to determine the incidence, type, position and area of crack occurring from the time of lay to packing in boxes at the end of the grading line. The incidence of cracks which occurred during laying, gathering and packing ranged from 1.1 to 1.7 percent and during shipping, washing, grading and packing from 4.6 to 14.5 percent. Cracks occurring at the grading station or during shipping were mainly of the pressure type; while shell damage from time of lay until shipping to the grading station resulted largely from an impact of some type. Medium size eggs (1 3/4-2 oz.) had the highest incidence of cracks. The area of the shell affected and the location of the crack differed significantly with respect to the incidence of impact versus pressure type cracks.

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Two studies were conducted to determine the phosphorus requirements of forcemolted Leghorn hens. In the first study, diets containing .8, .6, or .4% total phosphorus and 4% calcium were fed. In the second study diets with levels of .7, .6, .5, or .4% total phosphorus and 3.8% calcium were fed.Decreasing the phosphorus level improved shell quality as measured by specific gravity and shell thickness. However, egg production and egg weight decreased as phosphorus level decreased. Thus, in these studies a total phosphorus level of >.5% and <.7% was required for egg production and egg shell quality in force-molted Leghorn hens. (

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