Supplementation of phytase on diet improves the apparent ileal digestibility of amino acids and P in growing piglets

Jie Pan et al.

Abstract

The present study evaluated the effect of dietary phytase supplementation on the performance, apparent ileal digestibility (AID) of amino acids (AA) and P of growing piglets. A total of 32 growing piglets with a mean body weight (18.36±1.39 kg) were divided into 4 groups randomly: positive control group (A) is basal diet without phytase; negative control group (B) is similar to A except that available P was reduced by 0.18%, and two experiment groups C and D with 500 and 1000 U/kg phytase (5000 U/g), respectively, in B group diet. All piglets were fed for 30 days and then killed for sample collection. Consequently, no significant difference was observed on average daily gain (ADG) and ratio of feed to gain (F/G) in all groups, but ADG was 3.5% higher in D group compared with positive control group. Supplementing of phytase increased the AID of methionine, threonine, isoleucine, histidine and lysine (P<0.05). For D group, the AID of P was increased 24% (P<0.001) and the amount of P excreted was decreased by 17.9% (P<0.05) compared with A group. Dietary supplementation of phytase improved P digestion and utilization in growing piglets under the condition of the present study.

In corn-soybean meal-based diet of swine husbandry, about 60 to 90% of P commonly occurs as phytate P, which is one of the main antinutritional factors for swine growth  ¹ . Since the structure characters of phytate and chelating with other dietary nutrients, phytate P cannot be used directly in swine intestine  ^2-4 . Phytase is a phosphatase enzyme, produced by microbes survived in the gut of ruminant animals, which catalyzes the hydrolysis of phytic acid and releases the bound nutrients for utilization  ^6-8 . The phytase in diet and piglet organism are not sufficient for gastric efficiency of phosphorus utilization  ^{9, 10} . Therefore, dietary supplementation of phytase in pig industry is an effective approach for improving the digestibility of P and other nutrients  ¹¹ .

Even though phytase has been found in animals, plants, fungi and bacteria  ^12-14 , it is mostly collected from transgenic microbes and produced from genetically modified yeast on a large commercial scale recently  ^{15, 16} . Some studies were made for the supplementation of phytase to diets for pigs, but conclusions lack of consistency  ^{17, 18} . Some studies showed improvements on the apparent ileal digestibility (AID) of crude protein (CP) and amino acids (AA), but others have no effect on both characters  ¹⁹ . This phenomenon may due to the diet composition inconsistency and the swine basic mechanism response.

Our study was designed to evaluate the effects of commercial phytase which produced by KDN Biotech Company on theperformance, feed utilization and AID of growing piglets.

Sample collection and biochemical analysis: Individial BW of pig was measured at the beginning and end of experiment for calculation of average daily gain (ADG)  ²¹ . The pen feed disappearance were determined weekly, in order to calculate average daily feed intake (ADFI) and ratio of feed to gain (F/G). At the final week of experiment, one pig was selected at random from each block, fed in the metabolic cage. Feces were collected using total feces collection method and frozen at -28°C for analysis ²². AID of AA and P analyses were measured according to procedures outlined by Fang et al.  ²³ and Jones and Gilligan  ²⁴ . P excretion was determined based on the method of Omogbenigun et al. ²⁶ .

Statistical analysis: Data were subjected to one-way analysis of variance (ANOVA) and means were separated by Duncan's multiple range test using SPSS 13.0.

Results

Evaluation of phytase supplementation on the performance of growing pigs: In our study, no significant difference was observed on average daily gain (ADG) and ratio of feed to gain (F/G) in all groups, but F/G was 2.84% and 2.2% lower in C and D group compared with positive control group, respectively (Table 2).

Apparent ileal digestibilities of amino acids: Table 3 shows the apparent ileal digestibilities (AID) of amino acids (AA) in different supplementation of phytase in low P basal diet. It is obvious that supplementing of phytase increased AID of methionine, threonine, isoleucine, histidine and lysine (P<0.05). For C group, the AID of methionine was 10.83%, 11.29% higher compared with A and B groups, respectively (P<0.01); as to the AID of threonine, phytase supplementation in D group also increased the value by 11.23% and 13.34% compared to A and B control groups, respectively

(P<0.01). Meanwhile, the AID of isoleucine, histidine and lysine in D group was increased by 5.72%, 4.27% and 6.08% severally compared with A group (P<0.05). The AID of other amino acids was not changed significantly, but some had the tendency of improvement.

Evaluation of phytase supplementation on the AID of P and Pexcretion of growing pigs: The evaluation of phytase on the AIPof P and P excretion are presented in Table 4. For C group, theAID of P was increased 24% (P<0.001) compared with A group. As to the amount of P excretion, it was decreased in D group by 17.9% (P<0.05) compared with A group.

Discussion

In our study, we investigated the effect of dietary supplementation of phytase on the performance and the AID of amino acids and P in growing pigs. Both 500 and 1000 U/kg phytase supplementation can decrease the F/G of growing pigs, but the ADG has no significant difference among 4 groups. Previous studies have demonstrated that the supplementation of phytase will improve the performance. Adding phytase in diet increased the ADG and improved the phosphorus utilization  ^{27, 28} . Lower P concentration in diet will inhibit the appetite of animals  ²² . Phytase improved the utilization of phytate P in feedstuffs and other nutrients, which were binding to phytate in digest process and therefore improved the digestibility of proteins, AA, fat and crude fibre  ^{29, 30} . The AID of P was significantly increased in current experiment, especially in 500 U/kg phytase supplementation group  ³¹ . P excretion in 1000 U/kg showed an obvious decrease compared with two control groups  ³² . Other studies also revealed potential environmental benefits through a 30 to 40% reduction in P excretion ³³ . For P excretion, it depends on levels of phytase in the diet; in weanling pigs, P digestibility was increased from 30 to 190% ³¹ .

Apparent ileal AA digestibility was affected by the amount of phytase supplementation in diet. In this study, adding of phytase increased the AID of AA significantly. The AID of threonine, isoleucine, histidine and lysine were higher in 1000 U/kg group than in control groups. AID of methionine was higher in 500 U/kg supplementation. Zhang et al.  ⁶ showed that 500 U/kg phytase supplementation was not enough for enhancing AID of AA  ³² . Furthermore, 1200 U/kg phytase supplementation significantly increased the AID of crude protein and some AAs, such as lys, try and thr  ³³ . However, some reports pointed out that phytase supplementation does not consistently improve the AID of AA, some AA response factors would have a possible effect on AID of AA in phytase supplemented pigs  ³⁴ . Therefore, it can be seen that the efficiency of phytase on swine AID of AA depends on the activity of phytase and types of AA  ^{35, 36} .

In conclusion, the results of this study clearly showed that dietary phytase supplementation significantly increased the AID of P and AA, as well as decreased the P excretion. These findings provide more important evidence for the phytase application in swine industry and how to use it more efficiency.

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Article made possible through the contribution of Jie Pan et al.