Effect of different techniques for fermenting liquid feed on performance and Enterobacteria counts of grower and finisher pigs

Nguyen Nhut Xuan Dung¹, Pham Quang  Minh² , Luu Huu Manh³, Vo Minh Goi¹ and Brian Ogle⁴

1 Department of Animal Sciences, Agricultural College, Cantho University

nnxdung@ctu.edu.vn

2 Cataco Company, Cantho, Province

3 Department of Veterinary Medicine, Agricultural College, Cantho University

4 Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences

Abstract

A study was conducted to observe the effects of feeding growing-finishing diets as dry feed (BS: basal diet), as non-fermented liquid feed (NFLF), with fermented broken rice soaked for 12h and 24h (FLFBR_12h and FLFBR_24h), and as a fermented compound diet, soaked for 12 h and 24h (FLFBS_12h FLFBS_24h) on the performance of pigs from growing to slaughter, and also on Enterobacteria and Coliform counts in feeds and faeces of pigs. Thirty weaned Yorkshire pigs (23.0 ± 1 kg) were allocated according to a randomized complete block design with five replicates. The trial lasted for 90 days. The live weight gains of pigs fed FLFBR_24h were significantly higher than for the BS diet (P=0.04) and those of the other diets were slightly improved (NS). Feed conversion ratio was similar among diets (P>0.05). Enterobacteria counts in the feeds and faeces for diets FLFBR_12h,FLFBR_24h,FLFBS_12h and FLFBS_24h were significantly lower than those in diets BS and NFLF. Coliforms were totally absent in FLFBR_12h, FLFBR_24h, FLFBS_12h and FLFBS_24h. Feed cost of the treated diets was lower than of the BS diet. The study showed that non-fermented feed or fermented liquid feed improved live weight gain, and significantly reduced the numbers of Enterobacteria and coliforms in feeds and faeces.

Key words: Coliform, Enterobacteria counts, fermented liquid feed, live weight gain, pigs

Introduction

Distinctions between fermented liquid feed (FLF) and non-fermented liquid feed (NFLF) have been defined by Canibe and Jensen (2003). FLF is a mixture of feed and water made immediately before feeding and NFLF is a mixture of feed and water stored in a container at a certain temperature and for a certain period of time to ferment before it is fed to the animals. FLF feed is characterized by high levels of lactic acid bacteria (LAB), low pH and low Enterobacteria counts (Jensen and Mikkelsen 1998; Canibe et al 2001; Lawlor et al 2002). According to Mikkelsen and Jensen (1998), FLF and acidified liquid feed may improve pig performance because the pH of the feed is usually 4.0 to 4.5, as the dominant microflora that develops in liquid feed is the LAB, which will help eliminate deleterious microbes from the digestive tract. Our preliminary study (Nguyen Nhut Xuan Dung et al 2005) showed that there was an increased live weight gain, feed conversion efficiency and nutrient digestibility in pigs fed FLF during the growing period compared to  those fed dry feed, and that it was  similar to NFLF.

Duration of soaking and substrates used for fermentation are also important. Choct et al (2004) demonstrated that steeping time increases live weight gain and improves feed conversion ratio of pigs. Therefore, the hypothesis is that with an appropriate soaking duration and substrate, with starchy feeds such as broken rice or a compound feed as basal diet, it is possible to increase the performance and intake of pigs and reduce Enterobacteria counts, which also provide conditions to optimize the performance and feed intake. The low pH and high lactic acid content of fermented feed may inhibit Enterobacteria in the feed and hence eliminate them at the start of the food chain, thus improving the pig health.

The aim of the study was to measure the performance, feed intake and Enterobacteria counts in the feeds and faeces of pigs fed dry, non-fermented and fermented feed at different fermentation times.

Materials and methods

Animals

30 weaned pigs at a live weight of approximately 23 kg were individually penned and given the experimental diets for a period of 90 days.

Fermented liquid broken rice and basal diet

For the diets FLFBR_12h and FLFBR_24h, inocula were prepared by soaking broken rice according to Nguyen Nhut Xuan Dung et al (2005). Inocula and broken rice were soaked with water at a ratio of 1:2 in a container for 12 h (FLFBR_12h) and 24 h (FLFBR_12h), and immediately before feeding the remaining feed allowance was mixed and water added to keep a ratio of 1:2. For the diets FLFBS_{12h and} FLFBS_24h, the feed allowance was mixed with water at the same ratio as in FLFBR_{12h and} FLFBR_24h and soaked for 12 h and 24h, respectively.

Treatments and design

The study included 6 treatments

1. Basal diet (BS): fed dry

2. NFLF: non-fermented liquid basal diet (water added immediately before feeding, feed:water ratio of 1:2)

3. FLFBR_12h: fermented broken rice (feed allowance soaked for 12h before feeding, feed:water ratio of 1:2)

4. FLFBR_24h: fermented broken rice (feed allowance soaked for 24h before feeding, feed:water ratio of 1:2)

5. FLFBS_12h: fermented basal diet (feed allowance soaked for 12h before feeding, feed:water ratio of 1:2)

6. FLFBS_12h: fermented basal diet (feed allowance soaked for 24h before feeding, feed:water ratio of 1:2)

All diets were formulated to contain 17 and 15% CP in DM for the growing and finishing periods, respectively (Tables 1 and 2).The experimental diets were allocated according to a complete block design with 5 replicates and 1 pig per replicate.

Feeds and diets       

The feed ingredients, their composition and diet formulations are presented in Tables 1 and 2

Laboratory analysis

Prior to analysis, feed samples were ground through a 1-mm screen using a laboratory hammer mill. Analyses of feed samples were performed following procedures of the Association of Official Analytical Chemists (AOAC 1984) in duplicate. Acid detergent fiber (ADF) was determined according to AOAC (1984). Neutral detergent fiber (NDF) was analysed according to Van Soest et al (1991) as modified by Chai and Udén (1998). Gross energy (GE) was determined by using an adiabatic bomb calorimeter. Feed pH was taken and measured each morning after mixing with the other diet ingredients. Fermented broken rice remaining in the container after replenishment and mixing with new broken rice was measured for pH. The pH meter used (digital pH meter 831, Japan) was calibrated daily using buffers of pH 4.01 and 6.86.

Faecal samples were aseptically and directly collected at the end of the study, from the rectum and placed into wide-mouthed sterile bottles. For isolation and identification of Enterobacteria counts one gram of feed sample and digesta were weighed, serially diluted, and 100 ml aliquots were plated on MacConkey agar (Merck 1.05465). Enterobacteria were counted after 24-h incubation (37°C). Coliforms were enumerated on Violet Red Bile Agar (VRBA; Oxoid Ltd.) following 24 h of incubation at 30^oC

At the end of the trial, back fat thickness was measured with an ultrasound device (Renco Lean-meater), detected between the 10^th and 12^th rib. The formula used for the adjustment was:

FAT READING x FACTOR

Where: FACTOR = 1.275 + ((.0033*(WEIGHT)) - (.0000605*(WEIGHT)²))

Management

At the beginning, the pigs were fed two times daily (at 09:00 h and 15:00 h) and offered the diets close to ad libitum feeding, then 4 times a day (7:00, 10:00, 13:00 and 17:00h). Data on feed intake was collected daily and live weights of individual pigs were recorded monthly. Daily dry matter intake (DMI) and average daily gain (ADG) were recorded for individual pigs and feed conversion ratio was calculated as DMI divided by ADG.

Statistical analysis

The effects of dietary treatment on daily gain, feed conversion ratio and digestibility were analyzed using the GLM model (Minitab version 13.2, Ryan 2000):

The model was: Y_ij = µ + D_i +B_j + e_ij

Where Y_ij is the dependent variable, µ is the overall mean; D_i is the effect of diet, i = 1, 2, 3, 4, 5; B_j is the effect of block, j = 1, 2...5; e_ij represents random error. When there was an overall effect of diet, differences between means were compared by Tukey's least significant difference method, declared at P < 0.05.    

Results and discussion

Effect of fermented liquid feed on growth performance and feed conversion ratio

The effect of liquid and fermented liquid feed on performance and feed conversion ratio of grower-finisher pigs is presented in Table 3. Daily gain and feed conversion efficiency (FCR) were not affected by treatment (P>0.05) in the growing and finishing periods, but overall the pigs fed diets NFLF and FLF were heavier than those given dry feed (P=0.04), while feed conversion ratio (FCR) was not affected by treatment (P=0.22).

There was no effect of fermenting duration (12h vs 24h) on live weight gain among pigs. However pigs given diets FLFBR_24h and FLFBS_24h tended to have higher live weight gain than those in FLFBR_12h and FLFBR_12h (0.715 kg/day vs 0.598 kg/day and 0.643 kg/day vs 0.628 kg/day, respectively).

There was no effect of starch source (broken rice vs compound feed) on live weight gain among pigs, although FLFBR_24h tended to be higher in live weight gain than FLFBS_24h (0.715 kg/day vs 0.643 kg/day, respectively). The pigs fed non-fermented liquid feed had similar daily gain to fermented liquid feeds, and both were higher than for those on dry feed.

Fermented feed and liquid feed had no effect on back fat thickness (P=0.79). Fermented liquid feed has been given to pigs on a small scale in the Mekong delta, where fermented materials used, such as broken rice, are soaked in fresh water overnight or for a certain period before feeding.

Daily gains of pigs fed NFLF and FLF were higher than those of pigs given dry feed, and feed conversion ratio also tended to be improved compared to dry feed, results that were similar to values in a review of Scholten et al (1999). However, Jensen and Mikkelsen (1998) concluded that pigs given fermented liquid feed had improved feed efficiency compared to dry feed, whereas effects on growth rate were less consistent. The daily gain of pigs fed fermented broken rice was somewhat higher than in the fermented basal diet, which was similar to a report of Canibe and Jensen (2007), who found that piglets fed fermented liquid cereal grain feed had higher daily gain as compared to a fermented compound feed, although the difference was not significant. They also found a higher in density of yeast and higher concentration of alcohol in the gastro-intestinal tract as compared to a fermented compound feed. Live weight gain of pigs fed NFLF was significantly higher than for the dry feed and slightly higher than in pigs fed FLFBR_12h FLFBS_12h and FLFBS_24h, and a similar result was found in the studies of Moran (2001) and Canibe and Jensen (2003).

Feed conversion ratio of pigs fed the dry feed was higher than that of NFLF and FLF, although the difference was not significant. Trough size is also important, as intake depends on trough size, although information for the trough size used in liquid feeding to optimize intake is limited (Scholten et al. 1999).

Enterobacteria and Coliform count

The effects of liquid and fermented liquid feeding on Enterobacteria and Coliforms counts in feeds and faeces of pigs are presented in Table 4 and Figure 1. All fermented diets had lower numbers of Enterobacteria and Coliforms than those in the BS diet. Faeces excreted from the pigs fed fermented broken rice was significantly lower in Enterobacteria counts than in the BS diet, and in NFLF and FLFBS_12h and FLFBS_24h. With the exception of dry and non-fermented liquid feeds, the fermented liquid diets had a clear effect on Coliforms, that were almost absent in faeces (P<0.01).  Coliforms are gram negative bacteria that can not tolerate acidic conditions. This result is in agreement with the conclusion of Demecková et al. (2002), that piglet faeces from sows fed FLF had lower Coliform counts than in piglets from sows fed dry feed.

During the natural fermentation, lactobacilli and yeast are dominant in the feed. At a pH of approximately 4, lactic acid and acetic acid are produced, and these, in combination with the low pH, are responsible for the low number of Gram-negative bacteria (Winsen et al 2000). Numbers of Enterobacteria and Coliforms were high in the faeces of pigs fed dry feed and NFLF. Feeding NFLF tended to result in higher numbers of Enterobacteria than even dry feed, that can be explained by the fact that the fermentation occurs immediately when fresh feed and water are mixed, particularly at high temperatures (average 27^oC), when there is an increased risk of the growth of undesirable bacteria (van der Wolf et al 1999; Canibe and Jensen 2003) 

During fermentation, lactic acid and acetic acid are formed and the pH is reduced (Lawlor et al. 2002), which resulted in reduced Enterobacteria and E. coli counts. 

Figure 1. Effect of dietary treatment on Enterobacteria and Coliform counts in feeds and faeces

Economic return

Although feed conversion ratio was not different among treatments, all fermented feeds reduced feed cost and increased live weight gain, and thus improved the economic return for producers (Table 5).

Conclusions

• Fermented liquid feeds reduce the number of harmful bacteria, improve daily gain and result in higher economic benefits as compared with dry feed, and this simple method can be applied to small-scale farms.

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