LAUSR

A 6-week experiment with broilers was conducted to study the effect of diet supplementation with organic acids on performance, characteristics of the tibia and femur bones, and the calcium, phosphorus and zinc balance. A total of 320, one-day-old, Ross 308 chickens were randomly assigned to 1 of 8 treat - ments. A 2 × 4 factorial arrangement was used, with two dietary levels of calcium and available phosphorus (standard - 9.4/9.2 g Ca/kg and 4.3/4.0 g available P/kg, or reduced - 8.3/8.1 g Ca/kg and 3.7/3.5 g available P/kg, for the starter/finisher feeding phases, respectively), and with diets supplemented with organic acids (none; short chain fatty acids (SCFA), 4.0 g/kg; medium chain fatty acid (MCFA), 2.0 g/kg or SCFA + MCFA, 3.0 + 2.0 g/kg). Broilers fed diets supplemented with SCFA or MCFA displayed a performance similar to those fed the unsupplemented diet (P > 0.05). At 42 days, reducing the dietary levels of Ca and P decreased such bone parameters as tibia yielding load (256 vs. 270 N) and tibia stiffness (171 vs. 184 N/mm), as well as femur breaking strength (342 vs. 369 N), yielding load (233 vs. 250 N), stiffness (164 vs. 174 N/mm), and cortex thickness (1.47 vs. 1.56 mm). The organic acids had no effect on the parameters of the tibias; however, SCFA and SCFA+MCFA increased the yielding load and stiffness of the femurs. The SCFA diet supplementa- tion significantly increased the relative retention of Ca (45.0 vs. 41.1%). There were no significant Ca and P level × organic acids interaction effects on performance parameters, bone quality indices or the Ca, P, and Zn balance. It was thus concluded that SCFA can improve the bone quality and Ca balance in broiler chickens when fed either diets with a standard level of Ca and P, or those with reduced levels of these macrominerals.