Observations on the calcium balance of laying hens

Abstract

Two groups of Single Comb White Leghorn pullets, 4 months of age, were fed 1·85 and 2·70% calcium in the diet, respectively, for twelve consecutive periods, each consisting of 4 weeks.Records of egg production and egg weight were kept throughout the entire experiment for each hen. Calcium balance and egg-shell quality studies were conducted with 16 pullets for 5 consecutive days out of each 28-day period.A highly significant difference between the lots favouring the high-calcium birds was found in egg production, shell weight, and calcium retention. There were no significant differences between the lots in percentage calcium retention, food consumption, and body weight. The high-calcium group was shown to retain more calcium from the feed and excrete more calcium through eggs. Calcium retention and percentage calcium retention increased upon commencement of egg production to reach a maximum at the second period of production. Both remained fairly constant thereafter.The hens went into negative balance early in production and returned to positive balance during the later part of the first laying year. The return to positive balance could be explained by an increase in calcium retention and a decrease in egg production. There was no reduction in shell weight, or shell weight per unit surface area during the period covered by this trial.

The egg‐laying response of the domestic hen to variation in dietary calcium

“…They are consistent with most previously published work (Hurwitz and Griminger, 1960;Maclntyre et al, 1963;Gilbert, 1969;Douglas etal, 1972;McCready et al, 1973;Reichmann and Connor, 1977;Roland et al, 1978;Balch, 1979;Husseini, 1979) but are considerably more extensive than those previously available. Also, because a systematic study on a uniform population of birds was carried out using a wide range of diets, it is possible to extrapolate from the results to obtain an estimate of the effect on egg production of diets containing just less than the accepted optimum of about 35 g calcium/kg; this has not been possible previously mainly because many of the reports are contradictory (compare the references given above with those of Petersen et al, 1960;Helbacka, 1961;Combs, 1962;Davidson and Boyne, 1970) and also because the reports are not always comparable since often different dietary calcium concentrations and different birds were used by the different authors.…”

Calcium and reproductive function in the hen

“…The absorption of Ca from the intestinal contents is limited in non-laying hens (Common, 1943;Hurwitz & Griminger, 1960;Taylor & Kirkley, 1967) but with the onset of sexual reproduction the capacity to absorb Ca increases considerably. This change is brought about by the ovarian oestrogens (see Simkiss, 1961;Gilbert, 1967Gilbert, ,1969aDacke, 1979).…”

Calcium-45 uptake by shell gland, oviduct, plasma and eggshell of DDT-dosed ducks and chickens

“…Calcium in dissolved ash of eggshells was determined by titration with EDTA (Hurwitz and Griminger 1960). Calcium in plasma and in dissolved ash of tissues and droppings was determined by atomic absorption spectroscopy.…”