Effect of yeast fermented cassava pulp (FCP) on nutrient digestibility and nitrogen balance of post-weaning pigs

Hieu Le Huu and Terdsak Khammeng

Department of Animal Science, Faculty of Agriculture, Khon Kaen University
terdha@kku.ac.th

Abstract

The objective of this study was to investigate the effects of yeast fermented cassava pulp (FCP) in diets of post-weaning pigs on nutrient digestibility, the relationship between apparent digestibility and dietary FCP level, and nitrogen retention. A total of 15 entire male pigs with average initial body weight of 5.98±0.15 kg (Landrace x Landrace x Large White) were used in this study. They were housed in individual cages and allocated to five treatments in three blocks according to randomized complete block design. The treatments were five diets as FCP-0, FCP-3, FCP-6, FCP-9 and FCP-12 which contained 0, 3, 6, 9 and 12% FCP, respectively.

The proximate analysis showed that FCP used for experiment contained 13.4%, 17.1% and 2.11% of crude protein, crude fiber and crude fat respectively and 4208 kcal of gross energy. The apparent digestibility of dry matter, organic matter, crude protein, crude fiber and gross energy did not differ among treatments but ether extract digestibility was improved if more than 3% of FCP was included in the diets. Dietary FCP had no effect on nitrogen retention but urinary nitrogen tended (p=0.11) to be reduced when FCP included was included in the diet.   It may be concluded that FCP can be provided in post-weaning diets up to 12% without any detrimental effects on nutrient digestibility and nitrogen retention. 

Key words: fermentation, protein enrichment, weaned pigs

Introduction

Thailand is the leader of exported cassava starch in the world with the yield approximate 4 million tonnes per year and continues to increase as cassava starch production increases in the future (Khempaka et al 2009; Thongkratok et al 2010). Cassava pulp is the by-product of cassava starch production and it accounts for around 15-18% of the original processed root weight (Ali et al 2011). In Thailand, at least 1 million tonnes of pulp is generated annually (Khempaka et al 2009). If cassava pulp is not treated, it could have negative effects on the environment such as putrefaction, odor and polluted water (Ali et al 2011).

Cassava pulp which contains about 70% of the starch content can be used as feedstuff for animal (Khampa et al 2011; Thongkratok et al 2010). Kosoom et al (2009b) reported that cassava pulp can be used in diets of nursery pigs up to 15% without negative effects on growth performance of piglets. The study of Khempaka et al (2009) reported that dried cassava pulp can be incorporated in broiler diets up to 8%, however, higher level of included cassava pulp decreased growth performance and nutrient digestibility.

The major limitations of incorporating cassava pulp in animal feeds are low protein content, deficiency of essential amino acids and high crude fiber (Chauynarong et al 2009; Kosoom et al 2009b). Therefore, nutritive value of cassava pulp would be better if this by product is enriched through fermentation process prior to inclusion into animal diets (Kaewwongsa et al 2011; Oboh et al 2002; Thongkratok et al 2010).

Yeast fermented cassava pulp (FCP) is the product that is produced through fermentation by using yeast (Saccharomyces cerevisiae) (Khampa et al 2011). Although FCP could be included in the diet of animals as a low cost protein source to reduce the feed cost, the application of using FCP in the diet of pigs has not been investigated yet. Therefore, the objective of this study was to evaluate the inclusion level of FCP in the diets on nutrient digestibility and nitrogen retention of post-weaning pigs.

Materials and methods

Location

The experiment was carried out at the pig farm belonging to Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand from July to October 2013. The experimental protocols used in these studies were approved by the Committee of Department of Animal Science, Khon Kaen University.

Experimental design and housing

Animals

A total of 15 weaned entire male pigs (Landrace x Landrace x Large White) were allocated to 5 dietary treatments in a randomized complete block design. There were 3 blocks with a block as a replicate. The pigs (average initial weight of 5.98±0.15 kg) were individually housed in 0.6 m x 0.25 m x 0.5 m steel metabolism cages in an open house (Photo 1).

Photo 1: The metabolism cages to measure digestibility and N retention

Diets and feeding

FCP used in the experiment was obtained from the Faculty of Agricultural Technology, Rajabhat Maha Sarakham University, Thailand. Nutritive values of FCP were proximately analysed before formulating diets and are presented in Table 1. The diets were based on maize meal, soybean meal, fish meal, palm oil and FCP (Table 2). Five diets were formulated by using FCP at levels of 0, 3, 6, 9 or 12% in the diets: FCP-0, FCP-3), FCP-6, FCP-9 and FCP-12, respectively. The protein level and metabolizable energy (ME) of diets were maintained at the same level by adjusting the amount of fish meal and palm oil and met requirement of weaning pigs according to NRC (1998). The diets were mixed every 7 days and put into plastic bag in order to maintain the quality of the feed and avoid mould.

In each trial, pigs were assigned to dietary treatments and fed ad libitum for 7 days in individual pens. They were then placed in circular metabolism cages for a 3-d adaptation and 5-d collection period. The daily feed allowances were based on body weight at the beginning of the adaptation period, by the formula of (body weight)^0.9 x 5% (Moser et al 1982). Slight adjustments of this formula helped keep daily energy intakes consistent for all pigs. The daily allowance was divided in two equal parts and fed at 8.00 and 17.00 h. Water was available at all times through a drinking nipple.

Sample collection

The amounts of supplied feed and feed refusals were recorded every day in all periods. The total fecal collections were made daily and frozen at -20⁰C for later analysis. To collect urine, 20 ml of H₂SO₄ 10% was put in the containers that were placed under the metabolism cages. The collected urine was weighed and 10% of the daily urine volume was stored at -20⁰C. The procedures were done according to the methods described by Moser et al (1982). At the end of the experiment, feces and urine were thawed and mixed. After thawing, fecal samples of each pig were separated into two parts: one part was dried in the oven at 105ºC overnight to determine dry matter; the other part was dried at 60ºC for 72 h and ground through a 1 mm screen for proximate analysis.

Chemical analyses

FCP, experimental diets and feces were analyzed for parameterss including: dry matter (DM), crude protein (CP), crude fiber (CF), ether extract (EE), ash, calcium, phosphorus by proximate analysis. Gross energy content of FCP, diets and feces were determined by adiabatic oxygen bomb calorimeter. The urinary nitrogen was also analyzed for N.

Statistical analysis

The collected data were subjected to analysis of variance according to randomized complete block design (RCBD) using ANOVA procedure of SAS (version 9.0) software. The model used was:

Y_{ij =} m + Ti + Pj + eij   where  

Y = Dependent variable

m = overall mean

Ti = treatment effect

Pj = block effect

eij = random error

Results and Discussion

Characteristics of FCP

The FCP used in the study had low dry matter of 30.4%. This was higher than in the report of Tonsing et al (2008) that cassava pulp had only 10.4% DM. FCP contained 13.4% crude protein which was higher than the levels of 2.36% and 3.1% reported by Tonsing et al (2008) and Ali et al (2011) in fresh cassava pulp.  Chumpawadee and Soychuta (2009) reported that crude protein of cassava pulp increased from 2.52% (non fermented) to 16.8% (natural fermented) and 17.6% (induced microorganism fermented). Crude fiber of FCP was 17.1% which was lower than the level of 20.1% in cassava pulp reported by Ali et al (2011), but still a high level. High crude fiber can affect voluntary dietary intake as well as nutrient digestibility of young pig (Kyriazakis and Emmans 1995). The differences in crude protein and crude fiber of FCP in this study and previous studies could have been due to the source of cassava pulp. When it comes to energy content, this study clarified that gross energy of FCP was 4208 kcal/kg DM, which was similar to the value of 4178 kcal/kg DM of cassava pulp reported by Tonsing et al (2008). Kosoom et al (2009) found that the metabolizable energy (ME) of cassava pulp was 2461 and 2571 kcal/kg in young and growing pigs, respectively. Suksombat et al (2007) reported that ME of cassava chip and cassava pulp were 2.40 and 2.33 Mcal/kg respectively, which were lower than for ground maize (2.89 Mcal/kg) and soybean meal (3.13 Mcal/kg). Based on the crude protein and gross energy of FCP, it could be used as a feedstuff for pigs and as substitute for other raw materials, such as maize, broken rice or cassava, as these are more expensive.

The method for fermenting cassava pulp by yeast is developed from

Step 1:

Weighing of yeast  20 g + sugar  20 g + distilled water 100 ml into flask, then mixed and incubated at room temperature for 1 hour. (A)

 Step 2:

Preparation of medium by weighing 20 g of molasses directly into a blender vessel flushed with O₂, add distilled water 100 ml and urea 30 g then pour solution and incubate at room temperature for 10 minutes. (B)

 Step 3:

Remove yeast media solution in a flask from (A) into a medium (B) and continue flush O₂ for at least 60 minutes.

Step 4:

After at least 60 minutes, transfer yeast media solution 50 ml mix with cassava pulp 100 g and then cover by plastic bag for a minimum at least 10 days before feeding to animals.

Nutrient digestibility

There were no differences in feed intake, dry matter intake, fecal output and fecal dry matter output among treatments as the level of FCP increased (Table 3). This indicated that the appetite of pigs was not affected when FCP was incorporated in the diet up to 12%. Dietary FCP did not affect the apparent digestibility of dry matter, organic matter, crude protein and gross energy.  Lizardo and Aumaître (2001) stated that six to twelve percent of beet pulp in piglet diets did not affect total tract digestibility of energy and nitrogen. However, Bui Huy Nhu Phuc et al (1995) who studied using cassava leaf meal as substitute for soybean meal in cassava root diets for growing pigs reported that the nutrient digestibility decreased in cassava leaf meal diets. Regarding to crude fiber, the data illustrated that digestibility of crude fiber tended to increase as level of FCP increased (p=0.15). The result implied that the inclusion of FCP had a positive effect on the digestion of dietary fiber. This result was supported by previous studies which showed that the fiber digestibility was improved when total dietary fiber increased and fiber sources were fermented (Zhang et al 2013; Ziemer et al 2012). Du Thanh Hang et al (2009) reported that pigs fed cassava root meal and rice bran with inclusion of cassava leaves had higher digestibility of ether extract than diet including sweet potato vein, duckweed or stylo foliage. In agreement with former research, this study showed that there was higher in digestibility of ether extract in FCP-6, FCP-9 and FCP-12 compared with FCP-0 and FCP-3; digestibility of ether extract did not differ between FCP-3 and control diet FCP-0. The better digestibility could be attributed to increased short-chain fatty acid production and absorption in pigs fed with the high fermented fiber diet (Ziemer et al 2012) while the effect of FCP was not seen at small level (3%) (Figures 1 and 2).

Figure 1: Relationship between level of FCP in diet and apparent digestibility of crude fiber

Figure 2: Relationship between level of FCP in diet and apparent digestibility of ether extract

Nitrogen balance

The data show no effect of the level of FCP on digestibility of nitrogen or on nitrogen retention. Chhay Ty et al (2003) reported that diets based on ensiled cassava leaves had no effect on both nitrogen digestibility and nitrogen retention of growing pigs. In this study, the range of values for retained nitrogen (6.84 to 8.16 g/day) were higher than that in the report of Chhay Ty et al (2003) (range of 4.4 to 5.4 g/day) although nitrogen intake on the ensiled cassava leaf diet (13 to 14.7 g/day) were higher than present diets (12.4 to 13.9 g/day). The data are in agreement with Lizardo and Aumaître (2001) who reported that total tract digestibility of N was not affected when six to twelve percent of beet pulp in piglet diet was used. In addition, a previous study indicated that dietary fermentable fiber did not affect nitrogen retention and reduced urinary urea excretion (Zervas and Zijlstra 2001). In the present study, fecal nitrogen was not different among treatments but urinary nitrogen tended to be reduce as FCP added to the diets. The ammonia emission inside and outside the farm will be reduced with lower urinary nitrogen excretion (Zervas and Zijlstra 2001). The results of this study can contribute a strategy to farm management in reducing nitrogen excretion by diet management.

Conclusions

• Inclusion of FCP in the diets did not have negative impacts on nutrient digestibility and nitrogen retention of post-weaning pigs.

  
  

• Digestibility of ether extract was improved when FCP included in the diets while digestibility of fiber trended to increase.

  
  

• It is recommended that FCP can be incorporated in diets of post-weaning pigs up to 12%.

Acknowledgments

The authors are very grateful to Department of Animal Science, Faculty of Agriculture, Khon Kaen University for supporting the equipment and facilities for this research. The authors would like to express his deepest and sincere gratitude to Assistant Professor Dr. Sittisak Khampa, Faculty of Agricultural Technology, Rajabhat Maha Sarakham University for his kindness, advices during this study was carried out. The authors also would like to express their gratitude to Miss. Nguyen Thi Lan Anh and Mr. Ratchasak Thomasaroch, Master students, Department of Animal Science, Faculty of Agriculture, Khon Kaen University for their help during the experiment.

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Received 9 June 2014; Accepted 21 July 2014; Published 1 August 2014

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