Mineral Balance Studies on Poultry

Abstract

SINGULARLY few records of mineral balance studies on poultry have appeared in the literature. The difficulty of separating faecal excrement from urinary excrement has probably been responsible for this. At the same time such studies may yield information, even if the separation of faeces and urine is not carried out.Hainan (i) conducted balance experiments on two pullets over a period of 14 weeks; he found that storage of calcium, phosphorus and nitrogen occurs during only a short period before laying; the extra demands of the bird for these constituents during egg laying is met by increased retention from the food. He further concluded that an excessive calcium intake may lead to a depletion of phosphorus reserves, and he considered egg production to be associated with increased phosphorus catabolism, the phosphorus lost in this way exceeding that voided in the eggs.Russell and McDonald (2) carried out somewhat similar experiments on the calcium and phosphorus balance of pullets receiving either calcium carbonate or calcium citrate. Eight pullets were placed on a weekly balance for 5 weeks. The authors concluded that'' negative or very slightly positive balances and a lowered excretion of calcium in the droppings during egg production are excellent evidence that the laying pullet can utilise calcium from calcium citrate as well as from the carbonate for egg production." The balances, in other words, did not indicate any difference in the utilisation of calcium from either source. Russell and McDonald also noted that "in general during egg production more phosphorus is excreted in the droppings than during non-production, and more than is necessary to form tricalcium phosphate with the excretory calcium."The experiments described below were begun in 1929 with a view to securing information on the changes in calcium and phosphorus metabolism which accompany the onset of egg production.

Observations on the Mineral Metabolism of Pullets

“…The level of calcium excretion during the laying period was of the order of 0-25 gm. CaO per diem, in agreement with previous observations (3).…”

“…The figures for Hainan's other pullet lead to much the same result. The CaO/P 2 O 5 ratio of Hainan's ration (Ca0/P 2 0 5 = 1-33) did not diverge so very widely from that of tricalcium phosphate (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18); it is obvious that if CaO and P 2 O 5 were being retained in a ratio not greatly different, then the ratio in the droppings was bound to be almost the same. When viewed from the standpoint expressed here, Hainan's data cannot be regarded as necessarily establishing that calcium and phosphorus were being excreted together by his pullets as tricalcium phosphate.…”

“…Distilled water was freely supplied to the birds. The method of feeding was the same as that previously employed (3), and amounted to feeding ad libitum. For reasons which have been fully discussed by H. H. Mitchell (4), it is probably more desirable in this type of experiment to keep the food consumption as constant as possible.…”

“…The droppings were collected daily, dried, ground, weighed, and bottled in airtight bottles. The birds were irradiated with a quartz-mercury vapour lamp every other day as in a previous experiment (3). PEEPAEATION In the preparation of ration S, the salt was first of all incorporated with a portion of the maize meal, and then mixed through the main bulk.…”

Development of secondary bone in the domestic laying hen

“…These changes were first observed in the blood of pigeons by Riddle and Reinhart (1926), who observed a rise in the level of blood calcium from 9.3 milligrams/lOO milliliters in the non-reproductive female to a value greater than 20 milligrams/lOO milliliters at the time of ovulation. Common (1932) conducted balance experiments on pullets entering their production cycles. He observed that approximately ten days prior to the onset of production there was a large increase in the quantities of calcium and phosphorus retained from the diet.…”