Abstract:
Proc. Aust. Soc. Anim. Prod. (1978) 12: 125 EFFECTS OF PHOSPHORUS SUPPLEMENTS ADDED TO DRINKING WATER OF SHEEP J.T.B. MILTON* and J.H. TERNOUTH* Liveweight losses in sheep and cattle have been recorded where phosphorus (P) was provided by P supplements dissolved in drinking water (McMeniman and Little, 1974; Playne, 1974). Possible reasons for these effects may have been reduced food and water intakes. This experiment was conducted to determine whether P supplements dissolved in drinking water could influence food and water intake. In this study three P supplements were dissolved in drinking water and offered to 16 wethers for 10 days followed by'a 6 -day recovery period using a 4 x 4 latin square design. The supplements, which were dissolved in 2.14 1 of water, were: 26.4g 'Black' H3P04; 16.3g Mono-ammonium phosphate (M.A.P.) and 17.7g Mono-sodium phosphate (M.S.P.). For all sheep the daily diet offered was 1609 lucerne (0.2%P) + 40g Gluten (O.3%P) + ad lib Barley straw (O.OS%P). The effect of these supplements upon food, . water and total P intake, live weight and plasma inorganic phosphorus (Pi) of the sheep is reported. TABLE 1: Mean daily feed, water and total P intake, plasma inorganic P and weight change of sheep during and after supplementation. There was a significant (P < 0.05) reduction in barley straw, water intake and live weight of the sheep with the 'black' H3P04 and M.A.P. , supplements. However, with M.S.P. there was a reduction in food intake without any effect upon water intake and live weight. On removal of the 'black' H3P04 and M.A.P. supplements the sheep regained their original weight,' although it is possible that this weight gain was due to an increased water intake. Pi values increased with all supplements, however with 'black' H3P04 daily P intake was 43% lower than that with M.S.P. although Pi values were similar. This anomaly may indicate an increased absorption~of supplemental P when provided in the acid form or may reflect the extent of dehydration resulting from the 'severe reduction in water intake. As the Pi values were within the normal range it is unlikely that P toxicity per se was the cause of the reduced food and water intakes. These results suggest that the reduction in food intake'and live weight recorded with 'black' H3P04 and M.A.P. can in part be ascribed to . a reduced water intake, if so, the effect of M.S.P. may be acting through a different mechanism. It is possible that the reduction in water intake with 'black' H PO4 and M.A.P. may be associated with taste effects. The extent to whit 2 this and metabolic disturbances contribute to the adverse effects is currently being investigated. MCMENIMAN, N-P. and LITTLE, D.A. (1974). Aust. J. exp. Agric. Anim. Husb. 14:316. PLAYNE, M.J.71974). Proc. Aust. Soc. Anim. Prod. 1O:lll. *Dept. of Animal Production, University of Queensland, St. Lucia, Q., 4067. 125.