Evaluating feed components for formulation of pre-starter diets for broiler chickens
Garcia, Arturo Ricardo
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Broiler chicks during the first week posthatch possess limited digestive capabilities that increase as they age. A series of experiments was conducted to evaluate the main components of the feed in order to formulate pre-starter diets for broiler chicks. To evaluate the carbohydrate fraction, some studies were conducted in which corn, sorghum or pearl millet-based diets were fed to young broilers for the first 14 days posthatch. Pearl millet proved to be an excellent ingredient for inclusion in pre-starter diets. To evaluate the quality of protein sources, amino acid (AA) digestibility was determined in grains and protein concentrates used in poultry feeding by two different methods (chick ileal digestibility vs cecectomized rooster) and at two different ages (7 vs 21 days of age). Chicks at 7 d of age had the lowest AA digestibilities, whereas the greatest AA digestibility coefficients were obtained from adult roosters. Due to their limited digestive capabilities, young chicks might have different AA requirements than adult birds. To address this, a series of studies was conducted to determine whether the digestible lysine and sulfur AA requirements change from the first 7 to 21 days of age. There was no indication of drastic changes in the digestible lysine and sulfur AA requirements during this period. Phosphorus (P) is a major nutrient in chicken diets, and inorganic phosphates are usually added to the feed to fulfill the chick’s P requirement. First, foot ash was further refined as a technique to quantify bone mineralization in chicks. Upon completion of these studies, foot ash was used as a response to evaluate inorganic phosphates for their inclusion in pre-starter diets. Defluorinated tricalcium phosphate (DFP) and dicalcium phosphate (DCP) are widely used as inorganic P sources for broiler diets. However, P bioavailability of DFP is known to be lower than that of DCP. To evaluate if such difference in bioavailability would be exaggerated during the first week posthatch, two studies were conducted. The bioavailability of DTP was not dramatically reduced during the first 7 days of age, thus indicating that DFP is a satisfactory P source for pre-starter diets.