The Time Sequence of Adaptive Changes to Dietary Phosphorus Deficiency in the Chick

Abstract

Ten-day old chicks were divided into 6 groups which were fed a low phosphorus (P) diet for periods of 0, 0.5, 1, 3, 7 or 11 days before killing at 3 weeks old. Labelled calcium (47Ca) was injected intraperitoneally into some birds 18 hours before killing. A marked fall in growth rate, plasma phosphorus level, plasma growth hormone level and renal 24-hydroxylase activity levels had occurred by 12 hours after the experimental diet had started. After one day on the diet, the rate of duodenal Ca absorption had risen and continued to rise up to the 11th day. During this period, the renal 25-hydroxyvitamin D-1-hydroxylase activity rose slightly while the 24-hydroxylase activity rose towards the control level. At 24 hours, the 47Ca level in the bone was markedly lower than in the control group and remained low. It was concluded that the first adaptive response of the chick to dietary P insufficiency was to suppress growth. Subsequent adaptive responses were to increase the rate of Ca and P absorption from the gut and mobilisation from the bone but despite these measures, the growth rate only recovered slightly and the plasma P level continued to fall.

The effects of dietary levels of inorganic phosphorus, calcium and cholecalciferol on the digestibility of phytate-P by the chick

“…In the present study the negative effects of a high-phytate, low-inorganic P diet were overcome by the independent but synergistic effect of lowering dietary Ca and simultaneously raising the intake of cholecalciferol. The first dietary manipulation in the present study, that of lowering inorganic P from 4.5 to 2.6 g/kg, led to a predictable hypophosphataemia and a hypercalcaemia, to abnormalities in growth and skeletal development and to the marked rise in circulating levels of 1,25-(OH),D, previously recorded on lowering dietary P (Sommerville et al 1985). To this low-P diet two other modifications were made, singly and then together.…”

Phosphorus utilization in finishing broiler chickens: Effects of dietary calcium and microbial phytase

“…At low dietary Ca concentrations, Ca intake for tibia ash gain (g/g) was reduced, indicating more effective use of Ca for bone mineralization. This improved efficiency could result from increased intestinal absorption of Ca (Sommerville et al, 1985;Blahos et al, 1987;Hurwitz, 1996;Shirley et al, 2003) under control of 1,25-dihydroxycholecalciferol (Christakos et al, 2011) whose synthesis is upregulated under Ca deficiency (Sommerville et al, 1985;Blahos et al, 1987;Shafey, 1993;Hurwitz, 1996). Phosphorus absorption may also be improved through the activation of sodium phosphate (Na-phosphate) cotransporter IIb, characterized in the chick intestine (Yan et al, 2007), which has been reported to be under the control of the active metabolite of vitamin D (Han et al, 2009b).…”