Calcium and phosphorus requirements for maximized growth in modern market poults

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The Ohio State University

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Calcium and phosphorus are important macrominerals in the diets of market turkeys. However, using excessive amounts of these minerals is expensive and results in nutrient loading in the environment. Little research has been done since 1994 to examine the requirements of these minerals in young poults. Other research in chickens has suggested that we are feeding excessive amounts due to a failure to recognize that high concentrations of calcium and phosphorus depress dissociation of calcium phosphates in the digestive tract. A Ca:NPP (non-phytate phosphorus) ratio of 2.25:1 is probably more correct. This experiment was designed to examine this phenomenon in turkeys. The first trial identified the minimum phosphorus requirement in a diet with a calcium concentration of 1.2%. NPP treatments ranged from 0.37% to 0.61%. In the second trial dietary calcium was 1.0%, and NPP ranged from 0.32 to 0.55%. Female poults were raised from 1-21 days of age. The birds were then weighed, and the tibia was removed and ashed. These are the methods for determining the optimal phosphorus concentration. Statistical analyses of these data, including Least Significant Differences, indicated that for 1.2% Ca, there is an increase in all factors measured (body weight, feed intake, weight of tibia, %ash in tibia, and mg ash/100g body weight) until somewhere between 0.49% NPP and 0.55%NPP. With 1.0% Ca, the same trend was noticed upon completion of statistical analysis, placing the optima between 0.38%NPP and 0.44%NPP. It appears that turkeys may grow faster when fed 1.00%Ca than with 1.2% Ca, but the bone ash is decreased. This difference is expected to be significant. These data suggest that a Ca:NPP ratio of slightly above 2.0 is probably most correct when feeding a 1.2%Ca diet, but should be closer to 2.25 in a 1.0%Ca diet. The results indicate that by decreasing Ca concentrations, we can also decrease NPP concentrations, reducing feed costs and lowering phosphorus emissions in manure.


2nd prize at 2013 CFAES Forum--Animal Nutrition Division


animal nutrition, turkey growth, phosphorus, poultry