The effects of phytase on phosphorus(P)digestibility are well established.However,there are few studies that report P balance,particularly when phytase is used in diets that have adequate or deficient P.The main objec...The effects of phytase on phosphorus(P)digestibility are well established.However,there are few studies that report P balance,particularly when phytase is used in diets that have adequate or deficient P.The main objective of the study was to determine the effect of dietary P levels and exogenous phytase on P balance in growing pigs.The first part of the experiment was a 14-d metabolism study conducted with 80 barrows(initial body weight 18.5±0.5 kg)with a 2 x 5 factorial arrangement of treatments and main effects of available P(0.13%available P,low P[Low-P]diet;0.35%available P,adequate P[Adeq-P]diet)and phytase(0,250,500,2,500,and 12,500 U/kg).A portion of the pigs(n=24)fed the Low-P diet,with0,500,2,500,12,500 U/kg phytase,and those fed the Adeq-P diet,with 0 and 12,500 U/kg phytase,remained on test diets for another 4 d,and tissues were collected for determination of bone characteristics and tissue P concentration.There was a P×phytase interaction for P retention that was accounted for by a lack of re sponse to phytase in pigs fed the Adeq-P diet.Retention of P was greater with incremental levels of phytase in pigs fed Low-P diets as compared to those fed Adeq-P diets(P level x phytase,P<0.01),but calcium(Ca)retention was greater in pigs fed Adeq-P diets(P level x phytase P<0.01).Apparent total tract digestibility(ATTD)of P was improved by phytase(P<0.001)and was greater in pigs fed Adeq-P diets as compared to those fed Low-P diets(P=0.006).Metatarsal bone ash(quadratic,P=0.01)and strength(linear,P=0.03)was increased by phytase addition to the Low-P diets.There were no phytase or dietary P effects on P concentrations of the heart,kidney,liver,muscle,and spleen.These results suggest that as compared to the effects in an Adeq-P diet,adding phytase to a Low-P diet was more effective at reducing the P and Ca excretion and restoring average daily gain(ADG).The P released by phytase is absorbed and contributes to improved bone growth,greater rates of tissue accretion,and increased body weight,but does not change tissue P concentrations.There is,however,a threshold for P retention,beyond which it is excreted in the urine.展开更多
基金Partial funding for this research is from Zymetrics,Golden Valley,MN,USA.
文摘The effects of phytase on phosphorus(P)digestibility are well established.However,there are few studies that report P balance,particularly when phytase is used in diets that have adequate or deficient P.The main objective of the study was to determine the effect of dietary P levels and exogenous phytase on P balance in growing pigs.The first part of the experiment was a 14-d metabolism study conducted with 80 barrows(initial body weight 18.5±0.5 kg)with a 2 x 5 factorial arrangement of treatments and main effects of available P(0.13%available P,low P[Low-P]diet;0.35%available P,adequate P[Adeq-P]diet)and phytase(0,250,500,2,500,and 12,500 U/kg).A portion of the pigs(n=24)fed the Low-P diet,with0,500,2,500,12,500 U/kg phytase,and those fed the Adeq-P diet,with 0 and 12,500 U/kg phytase,remained on test diets for another 4 d,and tissues were collected for determination of bone characteristics and tissue P concentration.There was a P×phytase interaction for P retention that was accounted for by a lack of re sponse to phytase in pigs fed the Adeq-P diet.Retention of P was greater with incremental levels of phytase in pigs fed Low-P diets as compared to those fed Adeq-P diets(P level x phytase,P<0.01),but calcium(Ca)retention was greater in pigs fed Adeq-P diets(P level x phytase P<0.01).Apparent total tract digestibility(ATTD)of P was improved by phytase(P<0.001)and was greater in pigs fed Adeq-P diets as compared to those fed Low-P diets(P=0.006).Metatarsal bone ash(quadratic,P=0.01)and strength(linear,P=0.03)was increased by phytase addition to the Low-P diets.There were no phytase or dietary P effects on P concentrations of the heart,kidney,liver,muscle,and spleen.These results suggest that as compared to the effects in an Adeq-P diet,adding phytase to a Low-P diet was more effective at reducing the P and Ca excretion and restoring average daily gain(ADG).The P released by phytase is absorbed and contributes to improved bone growth,greater rates of tissue accretion,and increased body weight,but does not change tissue P concentrations.There is,however,a threshold for P retention,beyond which it is excreted in the urine.
