Poultry Reproductive Physiology

Two studies investigated the effect of a thermo-tolerant E.coli-derived phytase (QuantumTM) on performance and bone parameters of broilers fed diets varying in content of available phosphorus (AP), metabolizable energy (ME) and total lysine (TLYS). A 48-day floor pen trial used 80 pens of 16 male broilers fed corn/soya/meat-bone meal based diets formulated to commercial averages (AS) or below. A four phase positive control (PC) diet was fed with .91, .82, .76, .69% calcium (CA) and .45, .39, .34, .30% AP, and two negative control (NC) diets were formulated to contain less AP(.09% or .12%), ME(26 or 45kcal/kg) and TLYS(.01 or .03%), respectively for each phase. 250, 500 or 1000 U phytase/kg diet were supplemented to each NC resulting in 10 treatments. At day 40 and 48, the initial reduction in AP, ME and TLYS did not affect performance, but further nutrient removal reduced performance compared to the PC. Supplementing all NC diets with at least 250U/kg phytase improved performance to equal or better than the PC. Lowering AP significantly reduced 48 day femur ash, but this was restored to equal or better than the PC on adding phytase. A second 50-day floor pen trial using 88 pens of 16 male broilers was conducted to determine the impact of phytase on growth, bone ash and breast yield in corn/soya/meat-bone meal based diets varying in ME. As above, a four phase PC diet was fed and three NC diets were formulated to contain less AP(.12%) and TLYS(.01%) and ME lowered by 30, 45 and 60kcal/kg, respectively. 500 or 1000 U phytase/kg of diet were supplemented to the three NC diets resulting in 8 treatments. At day 40 and 50, reducing the amount of dietary AP, ME and TLYS resulted in significantly poorer BWT and cFCR, but further reduction in ME did not result in additional losses in performance. Adding 500 U/kg and 1000U/kg phytase to the NC equilibrated performance with that of the PC for the 45 and 60kcal reduced diet respectively. In these studies. EC phytase was able to return NC performance to that of the commercial PC, although the level of phytase needed would depend on the reduction in dietary nutrient levels.