産卵鶏における糞の内因性リン量とリンの尿中排泄について

Abstract

1. Determination of fecal endogenous phosphorus by using method of dilution analysis of P-32 and measurement of daily urinary phosphorus were made using four colostomized laying WhiteLeghorn hens. The hens were fed all mashed diet containning 0.96 percent of phosphorus and 2.80 percent of calcium.2. The fecal endogenous phosphorus was determined by using following formula:Fecal endogenous P (mg/day)=specific activity of P-32 in feces/specific activity of P-32 in urine ×Total P in feces (mg/day)It was estimated that the fecal endogenous phosphorus which was excreted by a hen a day was 6.47±1.02 (St. Dev.) mg on average. It was only 1.49 percent of the total phosphorus in feces on average. Therefore amount of the fecal endogenous phosphorus of the laying hen had little effect on calculation of true digestibility of phosphorus in the diet.3. Level of urinary phosphorus was exceedingly high on day of egg laying; while amount of urinary phosphorus was 10 percent of the total phosphorus excretion on day of pause, it reached 34 percent on laying day on average.It is inferable urinary phosphorus on laying day is released from bone, simultaneously with calcium which is called for formation of the egg shell. Therefore its amount indicates the degree in which mineral mobilization occurred in the bone for shell formation. The urinary phosphorus level of the hen was estimated to be about 2mg a day when no egg shell formation took place.4. Since almost all urinary phosphorus on laying day is derived from bone, the amount of corresponding bone calcium can be estimated by using Ca: P ratio (2.115) of bone. Assuming that all calcium released from bone with urinary phosphorus on laying day is utilized for shell formation, maximum percentage of shell calcium derived from bone can be estimated. Thus it was estimated that calcium derived from the bone constituted 21.7-46.4 percent of shell calcium in each hen, and 41.2 percent on average. Then diet calcium constituted 54-78 percent, and 59 percent on average of the egg shell calcium under the condition of the present experiment.