Influence of phytase supplementation to rice bran - based diets on the digestibility and phosphorus excretion in growing pigs

N T Long, T T B Ngoc and L T H Thao

National Institute of Animal Science, Vietnam
longniah@gmail.com

Abstract

The study was conducted to determine the effect of phytase and carbohydrase supplementation to diets based on rice bran on the digestibility of dietary components and phosphorus excretion of growing pigs. The basal diet was composed of maize meal, fish meal, soybean meal and rice bran, in which rice bran was considered as feed rich in fibre and phosphorus. The basal diet was calculated to meet requirement of growing pigs according to NRC (1998). Four diets including a basal diet (diet I), a basal diet supplemented with phytase (diet II), a basal diet supplemented with carbohydrate enzyme (diet III), and a basal diet supplemented with phytase plus carbohydrate enzyme (diet IV). Four castrated male pigs (Landrace x Yorkshire) with the initial body weight of 33 ± 1 kg  were designed according to a 4x4 Latin square. The experimental period lasted 12 days, the first 7 days for adaptation to the diet and last 5 days for fecal and urine collection.

The results show that the diets had no impact on the feed intake (P>0.05). There were significant differences in the digestibility of DM, OM, CF, NDF and P among diets (P<0.05), exception of CP digestibility (P>0.05). The diets supplemented phytase had higher P retention and lower total P excretion than the diets without phytase supplementation (P>0.05). The enzyme supplementation to diets (diet II, III and IV) had lower N excretion than diet without enzyme supplementation (P<0.05). The N retention was different significantly among the diets (P<0.05), with the highest value for the diet supplemented both phytase and carborhydrase enzyme. In conclusion, enzyme supplementation to the diets improved the digestibility of dietary components and P and N retention.

Keywords: pigs, phytase, carbohydrase enzyme, phosphorus, digestibility   

Introduction

In general, cereals ordinarily used in swine feeds have adequate contents of total phosphorus: 0.20-0.84% for maize, 0.24-0.77% for full fat soybean, 0.84-1.65% for rice bran (Chinh et al 2001). In addition, abundant in many feed ingredients of plant origin, phytate is one of the most important anti-nutritional factors for non-ruminant animals. However, the limited ability of pigs to use phytate-P poses a problem. This relates to the ability of phytate to form complexes with other dietary nutrients, such as minerals, proteins, free AA, and starch (Selle et al 2000). Phytase catalyzes the removal of orthophosphate groups from phytate (Maga 1982), allowing the bound nutrients to be released for utilization. The activity of intrinsic phytase in diets for pigs and activity of endogenous phytase in the digestive tract are not sufficient for efficient hydrolysis of phytate (Pointillart et al 1987; Cromwell et al 1993). Therefore, when rations are formulated for these animals, it is necessary to add inorganic phosphorus to meet their nutritional requirements, leading to increase environmental pollution and diet costs.

The supplementation of phytase to swine diets can improve the digestibility and retention of P in pigs (Simons et al 1990; Lei et al 1993a, b) and also improved the apparent ileal digestibilities (AID) of CP and some of the AA (Mroz et al 1994; Kemme et al 1999). As a consequence, phytase can reduce phosphorus, nitrogen and sulfur excretion, decreasing environmental pollution. A report focused on reducing or eliminating the inorganic phosphorus sources in swine feeds formulated with corn and soybean bran have been found that phosphorus excretion in the feces can be reduced by about 50% with the use of phytase (Cromwell et al 1995). The optimum supplementation rate appears to be 500FTU/kg diet, although a maximum response can be achieved at 1000FTU/kg diet (Canh 1995).  Recently, Wenk et al (1993) investigated the effects of the use of carbohydrate and phytase in a combination with pig, and found that both had a more or less pronounced effect on the digestibility of organic matter, energy, and N as well as P and zinc. However, they could not find any favorable effect of a combination of carbohydrate with the phytase concerning growth performance and digestibility of the nutrients. The objective of this study is to evaluate the digestibility of dietary components and phosphorus excretion of growing pigs given diets based on rice bran with phytase supplementation.

Materials and methods

Location and climate of the study site

The study was carried out at the Station of Animal Feed Trial (SAFT) belonging to National Institute of Animal Sciences. 

Experimental feeds

The basal diet was based on maize meal, fish meal, soybean meal, soybean oil, rice bran, in which rice bran was considered as feed rich in fibre and phosphorus (Table 1). The basal diet were calculated to contain metabolizable energy, crude protein and essential amino acids to meet requirements of growing pigs according to NRC (1998), and was offered in mash form (Table 2). Four diets including a basal diet (CTL), a basal diet supplemented with phytase (PHY), a basal diet supplemented with carbohydrase enzyme (CAR), a basal diet supplemented with phytase plus carbohydrase enzyme (PHY-CAR). The phytase and carbohydrase enzyme were supplied by BIOMIN Vietnam.
 

Experimental design

Four castrated male pigs (Landrace x Yorkshire) at around 2.5 months of age were arranged according to 4 x 4 Latin squares. All the pigs were vaccinated against pasteurellosis and hog cholera, and be kept individually in metabolism cages and given free access to drinking water through nipple drinkers. The metabolism cages were placed indoors, with maximum temperatures ranging from 25^oC to 33^oC

The experiment was included three periods. Each period was last 12 days, of which 7 days was for adaptation and 5 days for fecal collection. The pigs were fed ad libitum in the adaptation periods and then in the collection periods were restricted to 80% of the mean intake in the previous adaptation period. During both adaptation and collection, the feed was given in equal amounts twice per day at 8:00 and 16:00 hours and in the adaptation periods, remaining feed was removed and weighed and fresh feed was added. Feces and urine were collected twice daily after each meal. Ten percent of the total feces and urine were sampled at each collection time and stored in a refrigerator at 4^oC. At the end of each collection period, samples of feces and urine were pooled and taken for analysis. 

Measurements and analyses 

Urine samples were analyzed for total nitrogen and phosphorus in fresh form. Feed and faces were dried at 60^oC for 48 h and ground to pass through a 1-mm sieve before analysis. The samples were analyzed ash, CP (N x 6.25), phosphorus according to standard AOAC (1990) methods. Neutral detergent fiber (NDF) was analyzed using method of Goering and Van Soest (1991). 

Statistical analysis

Statistical analyses were performed using the GLM procedure of SAS (1998). Data were analyzed using the model Y_ijk=μ+T_i+A_j+P_k+ε_ijk where Y_ijk, observation from animal,  j, receiving diet I, in period k; μ, the overall mean; T_i, effect of diets; A_j, the effect of animal (j = 1, 2, 3 and 4); P_k, the effect of period (k = 1, 2, 3 and 4); and ε_ij, the residual effect. Difference between treatment means were determined by Duncan’s New Multiple Range Test (DMRT) (Steel and Torrie, 1980) with P<0.05 were accepted as representing statistically significant differences.

Results and discussion

Feed intake and nutrient digestibility

In general, supplementation of phytase and carbohydrase enzyme did not affect on daily DM and nutrient intake (P>0.05) (Table 3). Regarding fecal characteristics, DM concentration in diets II was higher than that in the diets I, III and IV (P<0.05) due to the lower level of fecal fibre, which has a low water holding capacity (Eastwood 1973; Serena et al 2008). The fecal P concentration in the diets II and IV was lower than in the diet I and III, which supported that the diets supplemented phytase decreased the fecal P concentration.

As shown in table 3, the digestibility of CP was not different among diets (P>0.05). As was suggested by Liao et al (2005) phytase supplementation to diets for growing pigs did not improve the digestibility of CP and amino acids. Adeola and Sands (2003) theorized that the formation of ternary complexes of phytase and protein during intestinal passage may have a negative effect on protease activity and on the digestibility of CP.

Pig fed the diets supplemented cabohydrase or a combination of phytase and cabohydrase enzyme had a positive effects on the digestibility of DM, OM, CF, NDF and P (P<0.05). The positive effects may have been due to disruption of intact cell walls and release of entrapped nutrients or due to the changes in the physical properties of non-starch polysaccharides, such as viscosity and water holding capacity, and/or changes in the composition and content of bacteria in the small and large intestine (Jensen et al 1998; O’Connell et al 2005). The current results are in agreement with studies by Ngoc et al (2011) and Len et al (2009). However, other studies (Jensen et al 1998; Högberg and Lindberg 2004) have reported no effect of enzyme supplementation (β-glucanase) on the digestibility of dietary components in pigs fed cereal-based diets. However, in the current study, the digestibility of DM, CF and NDF was not enhanced when pig fed diet with phytase addition (P>0.05), except for digestibility of OM and P (P<0.05) (Table 3). A study by Woyengo et al (2008) showed that phytase at 250 FTU/kg increased the digestibility of P by 51% at 20 kg of body weight or by 54% at 60 kg of body weight.

Phosphorus and Nitrogen balance

Table 4 shows that the daily excretion of fecal N and P or urinary N, in contrast to the daily excretion of urinary P (P>0.05), were influenced by the diets (P<0.05). Fecal daily phosphorus excretion was higher for the diets II and IV than for diets I and III, which is suggested that pigs fed diets with phytase supplementation, decreased fecal P excretion. The daily fecal N excretion was decreased when pigs fed diet with a combination enzyme addition, this can be due to the amount of fecal excretion was reduced. Moreover, the decrease in fecal N excretion was most likely associated with increased bacterial protein output (Canh et al 1998) because of the fermentation of dietary fiber components when diet supplemented a combination enzyme. 

The retention of phosphorus increased (P<0.05) for the pigs fed diets with phytase supplementation (Table 4). Some researchers showed that diets supplemented phytase can reduce phosphorus excretion and increase P retention (Kornegay et al 1996, Perney et al 1993, Emiola et al 2009). Cromwell et al (1993) reported that fecal phosphorus excretion of pigs was reduced 34-54%, by adding phytase in maize-soyabean meal diets. Another study pointed out that the combination of phytase and xylanase was improved retention of P (Olukosi et al 2007). However, in the present study individual phytase supplementation did not effect on N retetion, which was in line with earlier studies (Valaja et al 1998, Walz and Pallauf 2003, Johnston et al 2004). In contrast, some reports showed a positive effect of phytase supplementation both on N digestibility and N retention (Ketaren et al 1993, Mroz et al 1994, Sands et al 2001). The increase in P digestibility may have reduced limitation of P status on protein deposition, thereby reducing urinary N excretion.

Nitrogen retetion was enhanced when pigs fed diets with carbonhydrase or a combination of phytase and carbonhydrase enzyme (P<0.05). This can be explained that daily total N excretion was dcreased by supplementation of carbonhydrase or a combination of phytase and carbonhydrase enzyme.

Conclusions

• Enzyme supplementation to the diets improved the digestibility of dietary components and P and N retention. The digestibility of DM, CF and NDF was not significantly affected by phytase addition individually. The greatest significant reduction in fecal P and N was observed when combination of phytase and cabohydrase enzyme was added to diet. Furthermore, the digestibility of nutrition was the highest in diet with phytase and cabohydrase enzyme combination.

Acknowledgments

The authors would like to express their gratitude to the MEKARN project financed by the SIDA-SAREC for providing the opportunity and the budget to do the research, Thanks are also given to the National Institute of Animal Sciences (NIAS) for providing infrastructure support and laboratory assistance.

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