Phosphorus Requirements of Growing Pigs and Effect of Steam Pelleting on Phosphorus Availability

Inconsistencies in the estimated phosphorus requirements of growing pigs have come to light in recent years due to environmental constraints being imposed on the livestock production sector. Values of a net requirement estimated by the ARC (1981) extend from 4.6 g/day for 25kg liveweight to 5.2 g/day for 45kg pigs, but current literature suggesting that the actual requirement may be lower (eg Jongbloed and Everts, 1991) calls for a revision of previous recommendations.Around two thirds of the total phosphorus in cereals exists in the form of insoluble phytates which must be degraded before the phosphorus can be absorbed in the intestine. Under experimental conditions, the use of phytase in pig diets has demonstrated consistent improvements in phosphorus digestibility. The enzyme hydrolyses phytate by stepwise removal of orthophosphates, which become available for absorption in the gut. Although quantification of phytase/phosphorus substitution is as yet undetermined, digestibility results so far indicate that if used correctly the enzyme could largely replace inorganic phosphates, particularly in regions where soil phosphate levels are of concern.

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Interactions of phosphorus content and phytase inclusion in diets for growing pigs: Digestibility and P utilisation

Proceedings of the British Society of Animal Science ◽

10.1017/s1752756200003227 ◽

1999 ◽

Vol 1999 ◽

pp. 167-167

Author(s):

K.J. McCracken ◽

V.E. Beattie ◽

R.N. Weatherup ◽

R. W. Henry ◽

S. Smyth

Keyword(s):

Bone Strength ◽

Phosphorus Content ◽

Growing Pigs ◽

Available P ◽

Weaned Pigs ◽

P Content ◽

Phosphorus Requirements ◽

Utilisation Data ◽

The Impact

There is considerable literature on phosphorus requirements of pigs and on the use of phytase to improve phosphorus digestibility and reduce P excretion. However, much of this has been concentrated on weaned pigs (eg Beers and Jongbloed, 1992), the finishing stage (eg Russoet al, 1995) or the diets used were synthetic (eg Ketarenet al, 1993). The available P requirement for pigs between 20-50 kg was estimated at 3 g/kg by ARC (1981) but the NRC (1998) estimate is 2.3 g/kg. This paper reports digestibility and P utilisation data on 40 kg pigs using the grower diets employed in a study on the impact of commercially feasible reductions in dietary P content and of phytase inclusion on growth and bone strength (Weatherupet al, 1999).

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Physiological roles for aerenchyma in phosphorus-stressed roots

Functional Plant Biology ◽

10.1071/fp03046 ◽

2003 ◽

Vol 30 (5) ◽

pp. 493 ◽

Cited By ~ 137

Author(s):

Mingshou Fan ◽

Jinming Zhu ◽

Christina Richards ◽

Kathleen M. Brown ◽

Jonathan P. Lynch

Keyword(s):

Root Respiration ◽

Phosphorus Availability ◽

Phosphorus Concentration ◽

Metabolic Efficiency ◽

Aerenchyma Formation ◽

Cross Sectional ◽

Low Phosphorus ◽

Isolated Roots ◽

Soil Exploration ◽

Phosphorus Requirements

Low phosphorus availability induces the formation of cortical aerenchyma in roots. The adaptive significance of this response is unknown. We hypothesized that aerenchyma may be helpful to low-phosphorus plants by reducing root respiratory and phosphorus requirements, thereby increasing the metabolic efficiency of soil exploration. To test this hypothesis we investigated aerenchyma formation, root respiration and tissue phosphorus concentration in maize and common bean genotypes in response to phosphorus availability and ethylene treatments. Genotypes differed substantially in their ability to form aerenchyma in response to low phosphorus. Aerenchyma formation was disproportionately correlated with reduced root respiration; roots with 30% cross-sectional area as aerenchyma had 70% less respiration than roots without aerenchyma. Aerenchyma formation was also proportionally correlated with reduced root phosphorus concentration. Variation in aerenchyma formation was correlated with root respiration and phosphorus concentration, regardless of whether such variation was caused genetically or by ethylene or phosphorus treatments. Results with isolated roots were confirmed by measurement of whole root respiration of intact maize plants. Our results support the hypothesis that aerenchyma formation reduces the respiratory and phosphorus requirements of soil exploration by roots, and thus, represents a useful adaptation to low phosphorus availability.

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Improvement of phosphorus availability by microbial phytase in broilers and pigs

British Journal Of Nutrition ◽

10.1079/bjn19900052 ◽

1990 ◽

Vol 64 (2) ◽

pp. 525-540 ◽

Cited By ~ 465

Author(s):

P. C. M. Simons ◽

H. A. J. Versteegh ◽

A. W. Jongbloed ◽

P. A. Kemme ◽

P. Slump ◽

...

Keyword(s):

Phosphorus Availability ◽

Soya Bean ◽

Growing Pigs ◽

Feed Conversion ◽

Microbial Phytase ◽

Bean Meal ◽

Soya Bean Meal ◽

Plant Sources ◽

Better Than

Techniques have been developed to produce microbial phytase for addition to diets for simple-stomached animals, with the aim to improve phosphorus availability from phytate-P in plant sources. The activity of the crude microbial phytase showed pH optima at pH 5.5 and 2.5. The enzyme was able to degrade phytate in vitro in soya-bean meal, maize and a liquid compound feed for pigs. When microbial phytase was added to low-P diets for broilers the availability of P increased to over 60% and the amount of P in the droppings decreased by 50%. The growth rate and feed conversion ratio on the low-P diets containing microbial phytase were comparable to or even better than those obtained on control diets. Addition of microbial phytase to diets for growing pigs increased the apparent absorbability of P by 24%. The amount of P in the faeces was 35% lower.

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