TY  - JOUR
T1  - Effects of Dietary Supplementation on Phosphorus Metabolism in Sheep
AU - , Dorinha M.S.S. Vitti AU - , Ermias Kebreab AU - , Jo?o B. Lopes AU - , Adibe L.Abdalla AU - , James France 
JO  - Journal of Animal and Veterinary Advances
VL  - 4
IS  - 3
SP  - 349
EP  - 355
PY  - 2005
DA  - 2001/08/19
SN  - 1680-5593
DO  - javaa.2005.349.355
UR  - https://makhillpublications.co/view-article.php?doi=javaa.2005.349.355
KW  - 
AB  - Phosphorus (P) metabolism in sheep was studied using 98 Suffolk sheep, which were given various levels of P supplementation in their diet and administered a single dose of isotopic 32P in their blood. About 62% of P intake was excreted in faeces. Endogenous loss in faeces ranged from 8.6 to 84.0 mg P/kg body weight (BW) daily and was linearly related to P intake. Minimum endogenous faecal P loss was estimated at 8.63 mg/kg BW/day. Dietary P absorption was positively and linearly related to P intake at all intake levels, but the efficiency of absorption decreased at higher intakes. This suggests that P absorption involves not only a passive mechanism but also an active process, possibly due to homeostatic control. Taking an average 63% absorption efficiency, requirement of dietary P for maintenance was calculated to be 28.3 mg/kg BW/day. For a 35-kg sheep, this is equivalent to 0.99 g P/day to replace endogenous P losses fed at maintenance. Non linear relationships of salivary P with absorbed, endogenous feacal P and dry matter intake were established, suggesting that regulation of P secretion in saliva could be by active and passive mechanisms. Urinary loss of P was low, even at high levels of P intake. The paper demonstrates the relevance of understanding P metabolism and the need to estimate P requirements for ruminants accurately, in order to optimise production but avoid excessive P outputs to the environment.
ER  -