Effects of dietary fat level on laying hens fed various concentrations of calcium

Calcium Nutrition of Broilers: Current Perspectives and Challenges

Calcium (Ca) plays an essential role in poultry nutrition as 99% of Ca is located in birds' skeletal system. However, oversupply of Ca rather than deficiency of Ca is the current concern in commercial broiler diets. Calcium is an inexpensive dietary nutrient due to the cheap and abundant availability of limestone, the major Ca source; therefore, little attention was given to the oversupply of Ca in the past. The recent shift in the use of digestible P in broiler feed formulations has necessitated a closer look at digestible Ca, as Ca and P are interrelated in their absorption and postabsorptive utilisation. In this context, data on ileal digestibility of Ca and P in ingredients has been determined. Preliminary data on the digestible Ca and digestible P requirements for the different growth stages of broilers have also recently become available. The present review focusses on these recent advances in Ca nutrition. In addition, aspects of homeostatic control mechanisms, different Ca sources and factors influencing Ca digestibility in poultry are covered.

Effect of dietary calcium levels near the time of sexual maturity on water intake and excreta moisture content

Three trials were conducted to investigate the effect of dietary calcium on water balance of leghorn pullets. Trial 1 involved introduction of a 4% calcium layer diet at 112, 123, 134, or 144 days of age. Introducing the layer diet early had an early but transitory effect on water intake (P less than .05) and absolute quantity of excreta moisture, although the pattern of percentage excreta moisture was not clearly defined. In a second trial, birds were moved to laying cages at 105 days, with diet change from 1 to 4% calcium occurring at 112 or 142 days. When the layer diet was offered at 112 days, percentage excreta moisture was higher from 113 to 142 days, although no difference was seen after this time. In a final experiment, introduction of a 4% calcium layer diet at either 112 or 133 days of age resulted in higher percentage excreta moisture at four measurement periods to 245 days of age, although this effect was significant only at 147 days (P less than .05). These results suggest there is a transitory effect of dietary calcium on water intake and excreta moisture content. This affect may be of concern within controlled environment buildings and with certain manure-handling systems. In commercial situations, such dietary changes are often confounded with increased dietary protein concentration, another factor known to influence water balance in pullets.