Environmental Engineering Reference
In-Depth Information
mously. Further, based on such studies, the use of
selected brands of wheat bran as a source of phy-
tase in broiler feeding has been recommended.
Supplementation of phytase in low nonphytate
P diets improved growth performance, relative
retention of nutrients and minerals in blood and
bone of broilers (Singh et al.
2003
). Selle et al.
(
2003
) demonstrated the feasibility of reduc-
ing protein, amino acids, energy and P levels in
broiler diets with an appropriate level of phytase
supplementation to formulate least-cost rations.
The contents of crude ash, Ca, P, Mg and Zn were
adversely affected by lowering nonphytate P lev-
els in the diet of broiler chickens, but partially re-
covered by enzyme supplementation from
A. fic-
cum
(Paik et al.
2000
). Further, supplementation
of diets for growing-finishing pigs had improved
growth performance and nutrient availability
with 33 % reduction in manure P (Hong et al.
2001
; Abioye et al.
2010
). In addition to this,
Forsberg et al. (
2013
) reported the development
of transgenic pigs producing phytase in salivary
glands to reduce the impact of P on the environ-
ment and pigs' faecal P. In another study, Rosu
et al. (
2012
), reported that phytase supplementa-
tion of combined fodder recipes (NC) composed
of corn/soybean for laying hens do not require
the addition of fodder phosphates in food. Excess
of P supplements excreted over nutritional needs
of laying hens at the national level is 313.43 t per
year which is equal to 68.95 t monocalcic phos-
phate which is unjustified wasted.
Different studies have used different phytase
doses in actuality (500-12,500 U phytase/kg) and
reported a reduction in P excretion. These studies
concluded that the maximum effective concen-
tration of phytase yet remains unknown. These
studies should be considered while planning phy-
tase addition for management of P excretion and
its pollution management. According to Golovan
et al. (
2001
), addition of 250-1000 U phytase/kg
diet can fully replace P supplementation in poul-
try feed. Also, its supplementation significantly
increased serum concentrations of Ca, P, Mg, Zn,
Fe and Cu. Harper et al. (
1997
) and Oryschak
et al. (
2002
) observed a 27-28 % reduction in P
excretion when phytase was supplemented to the
diets of growing-finishing pigs while Lei et al.
(
1993
) reported a larger reduction of 35-45 %
for weanling pigs. However, Angel et al. (
2005
)
found no statistical difference in total P excre-
tion in pigs that were fed diets supplemented
with 515 U phytase/kg accompanied by 0.1 %
unit reduction in available P. Further reduction
of 0.2 % units in available P at the same level of
phytase inclusion reduced poultry litter P con-
centration (Angel et al.
2005
). Thus, there is a
need to investigate the effect of further reduc-
tion in dietary available P on the forms of P in
the manure. Supplementation of diet with higher
levels of phytase has been considered as a good
replacement for inorganic P addition in pig diets.
Rosen (
2002
) reported that microbial phytase at
2500 U phytase/kg of low P diet could triple the
improvement in feed efficiency of broiler chicks
compared to the industry level of 634 U phytase/
kg of diet. Veum et al. (
2006
) supplemented low
P diet fed to growing pigs by up to 12,500 U phy-
tase/kg and observed improved apparent absorp-
tion of P, Ca and Mg. According to a study by
Aiboye et al. (
2010
), phytase enzyme can wholly
substitute for inorganic P in pig diet when added
at high levels (2000 U/kg).
Phytase has also been used in combination
with other enzymes to improve growth perfor-
mance and nutrient digestibility in pigs fed corn/
soybean meal based diets (Shim et al.
2004
).
Addition of phytase in isolation or in combina-
tion with xylanase replacing 0.08 % dietary inor-
ganic P increased body weight and feed utilisa-
tion efficiency of broilers fed with wheat-based
diets and decreased overall mortality (Peng et al.
2003
). Simultaneous addition of phytase and car-
bohydrases improved feed efficiency ratio, nutri-
ent digestibility and nutritional value of soybean
meal, rape seed meal and cotton seed meal by im-
proving amino acid digestibilities in growing pigs
(Shim et al.
2003
). Phytase and xylanase were re-
ported to have a synergistic effect for enhancing
amino acid digestibility in broilers, which was
attributed to their complementary modes of ac-
tion (Selle et al.
2003
). However, combination of
phytase and glucanase had no positive effects on
laying performance of Leghorn hens and excre-
tion of nitrogen and P (Jacob et al.
2000
).
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