The effect of intravenous administration of phosphate in sheep.

Abstract

Proc. Aust. Soc. Anim. Prod. (1978) 12: 126 THE EFFECT OF INTRAVENOUS ADMINISTRATION OF PHOSPHATE IN SHEEP K.M. TOWNS*, F. VAN DEN BOOM* and H. STUBBE* Salivary secretion of phosphorus (P) is a major factor influencing P homeostasis in sheep, but it is not certain whether this high endogenous secretion allows more efficient utilization of P. A single high dose of P (3.4g) given rapidly was quantitatively recovered from the faeces in the subsequent 4 days (Clark et al. 1973). In order to simulate natural conditions more closely, asmaller amount of P (l.Sg/d) has been infused continuously over an ll-day period. The effect of the infused P on P turnover was examined using conventional balance techniques. Four sheep were given a ration of 700 g/d 1:l lucerne and oaten chaff for 2 weeks prior to and during the experimental periods. The ration contained 1.08 g/d P and 4.01 g/d Ca. Plasma P levels in 3 sheep rose from 4.2 to 13 mg/100 ml on the first day of infusion, but stabilized after one day at 5.8 mg/100 ml until the infusion was stopped, when the value immediately returned to 4.2 mg/100 ml. In the fourth animal, the plasma P was originally 4.9 mg/100 ml but rose to 63 mg/100 ml on the first day of infusion and .then fell sharply, stabilizing at 7.7 mg/100 mlafter 3 days. Values for faecal and urinary excretion of P are shown in table 1. TABLE 1: Faecal and urinary excretion of P and balance data (mg/d) for four sheep prior to and during intravenous P infusion (mean f SEM, n = 7). Assuming that 10 l/d of saliva is secreted and that the concentration of P in saliva is directly related to and about 10 times greater than the concentration in plasma (Tomas, Moir and Somers 1967), the amount 0f.P presented for absorption in sheep 1, 2 & 3 in the first period would be .5.28 g/d and the amount during the infusion period would be 6.88 g/d. In order to obtain the observed recoveries in the faeces we must assume that the true absorption of P in the first period is 81% and in the second 66%. Alternatively, if there was no change in the true absorption of P, daily excretion in the saliva would have to increase to 11.2 g/d to explain the amount of P recovered in the faeces. CLARK, R.C., BUDTZ-OLSEN, O-E., CROSS, R-B., FINNAMORE, P. and BAUERT, P.A. (1973). Aust. J. agric. Res. == 24:913. TOMAS, F.M., MOIR, R.J. and SOMERS, M. (1967). Aust. J. agric. Res. 18:635. == ----me----.----- e--- * School of Agriculture, La Trobe University, Bundoora, Victoria. 126. 3083