title: Methodology affects measures of phosphorus availability in growing broilers: Effects of calcium feeding strategy and dietary adaptation period length on true ileal phosphorus digestibility and predicted endogenous phosphorus losses1.
abstract: An experiment was conducted to determine the effects of Ca feeding strategy and dietary adaptation period length (DAPL) on the apparent ileal P digestibility (AIPD) and apparent ileal myo-inositol 1,2,3,4,5,6 hexakis dihydrogen phosphate (IP6) hydrolysis (AIIP6H) of corn titration diets. Nine hundred sixty Ross × Ross 708 male broiler chicks were placed into 80 battery cages. Broilers received a common starter diet until 18 d of age and then were fed one of 10 experimental treatments from 19 to 21 d of age. Nine diets were formulated to evaluate 5 corn inclusion concentrations (15, 30, 45, 60, or 75%) and 2 Ca feeding strategies (fixed at 0.35% or 1.4:1 Ca:P) after 3 DAPL (zero, 24, and 48 h). As a control for DAPL, one treatment group received the common starter diet for the duration of the experiment. Broilers consuming the control diet had higher (P < 0.001) BW gain and feed intake than broilers fed the corn titration diets. Apparent ileal P digestibility of the control diet was affected (P = 0.038) by DAPL. For diets formulated with a 1.4:1 Ca:P ratio, negative linear effects (P < 0.05) on AIPD and AIIP6H were observed with increasing corn. Conversely, for diets formulated with 0.35% Ca, positive linear effects (P < 0.05) were measured for AIPD after a 48 DAPL while no linear or quadratic effects (P > 0.05) were measured for AIPD or AIIP6H for other DAPL. Broilers fed diets formulated with 1.4:1 Ca:P had variable (P < 0.05) true ileal P digestibility (TIPD; 32.2, 15.1, and 35.4%) and negative endogenous P losses (EPL; -190, -499, and -262 mg/kg DM intake) for zero, 24, and 48 h DAPL, respectively. Conversely, TIPD values (41.2, 39.1, and 47.3%) were similar (P > 0.05) and EPL were positive (102, 197, and 154 mg/kg DM intake), regardless of DAPL, for broilers fed diets formulated with 0.35% Ca. These data demonstrated that formulating diets with a 1.4:1 Ca:P ratio affected AIPD of the titration diets, shifting the regression line and predicted negative EPL and an underestimation of TIPD.
authors: Department of Poultry Science, Auburn University, Auburn, AL 36849.
authors: K R
authors: KR
authors: Perryman
authors: AB Vista Feed Ingredients, Marlborough, Wiltshire, SN8 4AN, United Kingdom.
authors: H V
authors: HV
authors: Masey O'Neill
authors: AB Vista Feed Ingredients, Marlborough, Wiltshire, SN8 4AN, United Kingdom.
authors: M R
authors: MR
authors: Bedford
authors: Department of Poultry Science, Auburn University, Auburn, AL 36849.
authors: W A
authors: WA
authors: Dozier
mesh_terms: D000064:Acclimatization; D000821:Animal Feed / Q000032:analysis; D000822:Animal Husbandry / Q000379:methods*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002136:Calcium, Dietary / Q000378:metabolism*; D002645:Chickens / Q000254:growth & development / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D004063:Digestion; D006868:Hydrolysis; D007082:Ileum / Q000378:metabolism*; D008297:Male; D016226:Phosphorus, Dietary / Q000378:metabolism*; D010833:Phytic Acid / Q000378:metabolism; D011897:Random Allocation; D003313:Zea mays / Q000737:chemistry
chemical_list: D002136:Calcium, Dietary; D016226:Phosphorus, Dietary; D010833:Phytic Acid
keywords: broilers; calcium; digestibility; phosphorus; regression