The effect of calcium source and separate calcium feeding on the digestibility of calcium and phosphorus on poultry performance and skeletal health

Abstract

Calcium (Ca) and phosphorus (P) are essential minerals for skeletal health and development and for many biological processes in poultry. However, the relationship between Ca and P is complex and multifactorial. Studies presented in this thesis investigated three aspects of the Ca and P relationship, in order to improve growth performance, mineral digestibility and maintain and/or improve skeletal health. The first strategy investigated replacing dietary limestone with a highly soluble calcium source on growth performance, mineral digestibility and skeletal health. The second strategy, investigated how broilers prioritise Ca and P, and which nutrient they are willing to over consume to meet an intake requirement and the effect on performance. The final strategy, investigated if modern poultry still possess a Ca specific appetite and how this can be exploited with separate Ca feeding on performance, skeletal health and egg production. The results of this thesis provide useful and novel information for poultry nutritionists. Chapter 3 and Chapter 4 demonstrated replacing limestone with a highly soluble Ca is possible, provided it is used a lower dietary Ca inclusions and in conjunction with phytase, without negatively effecting bird performance. Chapter 5 demonstrated although dietary nPP is more influential on performance metrics, when fed a diet grossly deficient in nPP broilers are unable or unwilling to increase their feed intake to satisfy their dietary nPP intake target. However, broilers will readily over consume dietary P to defend a dietary Ca intake target. The results of Chapter 6 and Chapter 7 demonstrate that modern poultry do possess a Ca specific appetite, however, it may not be uniformly expressed among birds. In conclusion, overall the research strategies presented in this thesis provide information that can be used to decrease Ca and phytate-P interactions, consequently improving nutrient digestibility and bird performance while decreasing diet costs.