Effects of a Solid-State Fermented Phytase on Phosphorus and
Nutrient Digestibility of Growing Pigs Fed Barley-Soybean Meal Based Diets
Story in Brief
A total of 24 barrows were utilized in a 21-d digestibility study to determine the effects of the addition of a solid-state fermented phytase complex (Allzyme SSF; Alltech, Inc) to low available P, barley-soybean meal diets on P and nutrient digestibility. The basal diet, which consisted of barley and soybean meal, was adequate in all nutrients except available P. This diet contained .42% total P (.11% avail. P), provided by barley and soybean meal. Diets 2, 3, and 4 were the basal plus SSF to provide 250, 500, and 1,000 phytase units (PU)/kg, respectively. All diets contained .77% digestible lysine and a Ca:total P ratio of 1.2:1. Pigs were housed individually. Experimental diets were fed at three times maintenance energy requirement with unlimited access to water. Feces, urine, and orts were collected to estimate nutrients digestibility and P excretion. The addition of SSF phytase complex increased average daily gain and gain:feed ratio. Digestibility of phosphorus, dry matter, organic matter, ash, gross energy, and nitrogen increased with the addition of the enzymatic complex (SSF phytase complex). Compared with the basal diet, digestibility of phosphorus for pigs fed 1,000 PU/kg increased by 39%. These results indicate the addition of SSF phytase complex to low P barley-soybean meal diets improved nutrient digestibility of growing pigs with a dramatic decrease in P excretion.
Keywords: Pigs, Phytase, Digestibility
Introduction
Phytate (myoinositol 1,2,3,4,5,6
hexa, dihydrogen phosphate) is the major form of P in cereal grains and oilseed
meals (Reddy et al., 1982).
Approximately 70% of the P in cereal grains and oilseed protein
supplements is organically bound in the form of phytate, which reduces phosphorus
availability to pigs (Kornegay 1996; NRC 1998).
Pigs cannot utilize phytate due to the lack of endogenous phytase that
hydrolyzes phytic P (Peeler 1972).
Improving phytate utilization can reduce the need for inorganic P
addition in feed, resulting in reduced P excretion in manure. Addition of
microbial phytase to the diet improves P utilization and decreases excretion
(O’Quinn et al., 1997). Recently,
solid-state fermentation (SSF) has been used to produce microbial phytase. The
phytase produced by this system also contains other enzymes (α-amylase,
β-glucanse, protease, xylanase, and cellulase (Filer, 2001), that may
improve carbohydrate and protein digestibility.
Previous reports from our lab (Park
et al., 2003ab) reported that the addition of SSF phytase to low P,
corn-soybean based diets improved P utilization, growth performance, and bone
traits. However, other nutrients were
not affected by the addition of the SSF phytase up to 1,000 PU/kg. Because nutrient digestibility is relatively
high in corn-soybean meal diets, the potential to improve digestibility of
energy, protein, and dry matter is minimal.
On the other hand, barley is known to have a lower feeding value for
swine as compared with corn. Thus, there
is greater potential to improve nutrient digestibility in barley based
diets. Therefore, the objectives of this
study were to determine the effects of the addition of a solid-state fermented phytase complex to low P,
barley-soybean meal diets on growth performance, nutrient excretion and
digestibility of growing pigs.
Material and Methods
Twenty-four crossbred barrows with an average BW of 11.0 lb were used in a 21-d study to investigate the effects of addition of SSF phytase complex (Allzyme SSF; Alltech, Inc) on growth performance and nutrient digestibility of growing pigs fed barley-soybean meal-based diets. Pigs were blocked by initial body weight and randomly allotted to one of four dietary treatments in a randomized complete block design. There were six replications per treatment.
The experimental diets (Table 1) were fed in meal form. The basal diet, consisting mainly of barley
and soybean meal, was adequate in all nutrients, except available P. This diet contained .42% total P (.11% avail.
P), all of which was provided by barley and soybean meal. Diets 2, 3, and 4 were the basal plus SSF
phytase to provide 250, 500, and 1,000 phytase units (PU)/kg,
respectively. All diets contained .77%
digestible lysine and a Ca:total P ratio of 1.2:1.
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Table 1. Composition of experimental diets, as fed basis |
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|
|
Dietary treatments |
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|
Total P, % |
.47 |
.47 |
.47 |
.47 |
|
Available P, % |
.11 |
.11 |
.11 |
.11 |
|
Phytase, PTU/kg |
0 |
250 |
500 |
1,000 |
|
Barley |
76.51 |
76.51 |
76.51 |
76.51 |
|
Soybean meal |
21.57 |
21.57 |
21.57 |
21.57 |
|
Corn Starch |
.10 |
.08 |
.05 |
- |
|
Limestone |
1.07 |
1.07 |
1.07 |
1.07 |
|
Sodium chloride |
.25 |
.25 |
.25 |
.25 |
|
Vitamin premix a |
.15 |
.15 |
.15 |
.15 |
|
Trace mineral premixa |
.15 |
.15 |
.15 |
.15 |
|
Antibiotic b |
.20 |
.20 |
.20 |
.20 |
|
SSF Phytase c |
- |
.025 |
.05 |
.10 |
|
Calculated analysis |
|
|
|
|
|
ME, kcal/kg |
2,960 |
2,959 |
2,958 |
2,956 |
|
Lysine, % (App. Dig.) |
.77 |
.77 |
.77 |
.77 |
|
Ca, % |
.50 |
.50 |
.50 |
.50 |
|
Total P, % |
.42 |
.42 |
.42 |
.42 |
|
Available P, %d |
.11 |
.11 |
.11 |
.11 |
|
Ca:Total P |
1.2:1 |
1.2:1 |
1.2:1 |
1.2:1 |
|
Added phytase activity, PTU/kg of diet |
0 |
250 |
500 |
1,000 |
|
a Provided the following per kg of diet: 5,506 IU of vitamin A, 551 IU of vitamin D, 33 IU of vitamin E, 3.6 mg of vitamin K (as menadione), 221 mg of biotin, 137 mg of choline, 33.04 mg of niacin, 24.78 mg of panthothenic acid (as d-pantothenate), 5.51 mg of riboflavin, 27.55 mg of vitamin B12, 1.66 mg of folacin, 100 mg of Zn, 2 mg of Mn, 100 mg of Fe, 10 mg of Cu, .30 mg of I, and .30 mg of Se b Provided 55 mg of chlortetracycline per kilogram of diet c Solid-state fermented phytase complex (Allzyme® SSF; Alltech, Inc) contains 1,000 PU/g of product d Analyzed total P were .44, .44, .44, and .43, respectively |
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Pigs were housed individually in metabolic chambers in an environmentally-controlled room. The chambers were specially designed for the total, but separate collection of feces, urine, and wasted feed. Experimental diets were fed at three times maintenance energy requirements with unlimited access to water. During a 7-d collection period (d 14 to 21), feces, urine, and wasted feed were collected to estimate nutrient digestibility and P excretion. The pigs were weighed weekly to estimate ADG and gain:feed ratio. Feed intake was determined by the NRC equation (NRC, 1998).
Data were analyzed as a randomized complete block design using procedures described by Steel et al. (1997), with initial BW as the blocking criterion. The model included the effects of block (rep), treatment, and block x treatment (error). The effects of phytase supplementation were tested for linearity and curvilinearity using orthogonal polynomial contrasts. For the four levels of phytase, polynomial coefficients for unequally spaced treatments were generated using the ORPAL matrix function of the IML procedure of SAS. In addition, a nonorthogonal contrast was used for comparisons between diets containing SSF phytase and control diet. In all cases, pig served as the experimental unit.
Results and Discussion
The addition of SSF phytase complex increased (linear,
P<.05) ADG and gain:feed ratio (Table
2). Compared with the basal diet, pigs
fed 1,000 PU/kg had 19 and 26% greater ADG and gain:feed, respectively. Feed intake was not affected (P>.10) by
dietary treatment.
|
Table 2. Effects of SSF phytase complex on growth performancea |
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|
|
Dietary treatments |
|
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|
Total P, % |
.47 |
.47 |
.47 |
.47 |
|
|
Available P, % |
.11 |
.11 |
.11 |
.11 |
|
|
Phytase, PTU/kg |
0 |
250 |
500 |
1,000 |
SE |
|
ADG, lb b |
1.22 |
1.21 |
1.41 |
1.46 |
.07 |
|
ADFI, lb |
2.88 |
2.67 |
2.83 |
2.61 |
.09 |
|
Feed/gain, bc |
2.63 |
2.31 |
2.22 |
2.10 |
.03 |
|
a Least squares means for 6 pigs/trt b Linear effect of SSF phytase (P<.05) c None vs SSF Phytase (P<.05) |
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During the 7-d collection period, feed intake increased with
increasing (linear, P<.01) levels of SSF phytase complex. Total phosphorus intake (Table 3) was
linearly increased (P<.01) with SSF phytase levels due to the higher feed
intake. Daily fecal phosphorus excretion
was decreased (linear, P<.01) by 16.8% with SSF phytase, resulting in
increased phosphorus digestibility. Pigs
fed 1,000 PU/kg had approximately 63% greater phosphorus digestibility compared
with that of pigs fed the diet without SSF phytase. Also, ash digestibility was increased
(linear, P<.01) by the addition of SSF phytase. Pigs fed the diet supplemented with 1,000
PU/kg SSF phytase complex had much greater ash digestibility (63.8%) compared
with pigs fed the diet without SSF phytase complex (51.9%).
|
Table 3. Effects of SSF phytase on phosphorus and ash digestibility of pigs fed low P, barley-SBM based diets (DM basis) ab |
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|
|
Dietary treatments |
|
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|
Total P, % |
.47 |
.47 |
.47 |
.47 |
|
|
Available P, % |
.11 |
.11 |
.11 |
.11 |
|
|
Phytase, PTU/kg |
0 |
250 |
500 |
1,000 |
SE |
|
Phosphorus |
|
|
|
|
|
|
Intake, g/d bde |
4.43 |
5.05 |
5.73 |
5.52 |
.22 |
|
Feces, g/d bd |
2.91 |
2.71 |
2.61 |
2.43 |
.09 |
|
Absorbed, g/d bde |
1.53 |
2.35 |
3.12 |
3.09 |
.19 |
|
Digestibility, %
bde |
34.28 |
45.86 |
54.43 |
55.96 |
1.97 |
|
Ash |
|
|
|
|
|
|
Intake, g/d bde |
62.4 |
72.9 |
83.7 |
82.4 |
3.2 |
|
Feces, g/d |
30.0 |
31.1 |
31.0 |
29.8 |
1.0 |
|
Absorbed, g/d
bde |
32.5 |
41.8 |
52.8 |
52.6 |
2.9 |
|
Digestibility, % bde |
51.93 |
56.79 |
62.87 |
63.76 |
1.65 |
|
a Least squares means for 6 pigs/trt b Linear effect of SSF phytase (P < 0.01) c Linear effect of SSF phytase (P < 0.05) d Quadratic effect of SSF phytase (P< 0.05) e None vs SSF phytase (P < 0.05) |
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Dry matter intake (Table 4) was increased (linear, P<.01) by the addition of SSF phytase. Dry matter excretion of pigs fed SSF phytase complex was higher (P<.05) than that of pigs fed control diet due to higher feed intake. However, dry matter digestibility was increased (linear, P<.01) by the addition of SSF phytase complex. When 1,000 PU/kg was added to diet, dry matter digestibility increased by 3.2% compared with the diet without SSF complex.
Organic matter intake (Table 4) increased (quadratic, P<.05) with SSF phytase complex level. Due to the increased organic matter intake, the fecal excretion of organic matter increased (quadratic, P<.01) with SSF phytase. However, digestibility of organic matter increased (linear, P<.01) by the addition of SSF phytase complex. Pigs fed the diet containing SSF phytase complex (1,000 PU/kg) had 2.6% greater organic matter digestibility, compared with pigs fed the control diet.
Digestibility of gross energy and nitrogen (Table 4) were
improved (P<.01) by the addition of SSF phytase complex. Compared with pigs fed the diet without SSF
phytase complex, pigs fed 1,000 PU/kg had 2.6% and 4.1% greater digestibility
of energy and nitrogen, respectively.
Digestible energy was 73.5 kcal/kg greater for the diet containing 1,000
PU/kg compared with control diet (Table 4).
|
Table 4. Effects of SSF phytase on dry matter, organic matter, energy, and nitrogen digestibility of pigs fed low P, barley-SBM based diets (DM basis) ab |
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|
|
Dietary treatments |
|
|||
|
Total P, % |
.47 |
.47 |
.47 |
.47 |
|
|
Available P, % |
.11 |
.11 |
.11 |
.11 |
|
|
Phytase, PTU/kg |
0 |
250 |
500 |
1,000 |
SE |
|
Dry matter |
|
|
|
|
|
|
Intake, g/d bde |
902.9 |
1037.4 |
1150.7 |
1139.5 |
45.7 |
|
Feces, g/d e |
216.6 |
240.4 |
243.1 |
237.6 |
9.2 |
|
Absorbed, g/d
bde |
686.3 |
796.6 |
907.6 |
901.9 |
41.5 |
|
Digestibility, % ce |
75.97 |
76.54 |
78.84 |
79.16 |
.87 |
|
Organic Matter |
|
|
|
|
|
|
Intake, g/d bde |
840.5 |
964.2 |
1066.9 |
1057.1 |
42.4 |
|
Feces, g/d e |
186.6 |
209.4 |
212.1 |
207.8 |
8.3 |
|
Absorbed, g/d
bde |
653.8 |
754.8 |
854.9 |
849.3 |
38.7 |
|
Digestibility, % c |
77.76 |
78.04 |
80.09 |
80.36 |
.83 |
|
Gross Energy |
|
|
|
|
|
|
Intake, kcal/d bde |
3,968.2 |
4,564.6 |
4,982.2 |
4,947.7 |
200.1 |
|
Feces, kcal/d e |
996.3 |
1128.1 |
1138.9 |
1115.5 |
46.1 |
|
Absorbed, kcal/d be |
2971.9 |
3436.4 |
3843.3 |
3832.2 |
179.1 |
|
Digestibility, % b |
74.86 |
75.01 |
77.09 |
77.47 |
.95 |
|
Digestible Energy |
|
|
|
|
|
|
kcal/kg |
3290.1 |
3301.6 |
3337.9 |
3363.6 |
41.5 |
|
Nitrogen |
|
|
|
|
|
|
Intake, g/d bde |
30.38 |
36.40 |
40.24 |
40.60 |
1.6 |
|
Feces, g/d de |
7.86 |
9.50 |
9.40 |
8.88 |
.48 |
|
Absorbed, g/d bde |
22.52 |
26.91 |
30.84 |
31.72 |
1.43 |
|
Digestibility, %
b |
74.07 |
73.69 |
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