The effect of fermented coconut dregs with the addition of inorganic selenium on feed digestibility, growth performance and carcass traits of broiler chickens

B Sundu, U Hatta, S Mozin and A Adjis

Animal Husbandry Department, University of Tadulako, Palu, Indonesia
b_sundu@yahoo.com

Abstract

A study was carried out to determine the effects of Saccharomyces cerevisiae-fermented coconut dregs (SCFCD) with the addition of selenium on growth performance, feed intake, dry matter digestibility, selenium digestibility, dry matter faeces, meat selenium, drip loss, cooking loss and meat pH of broiler chickens. A finely ground coconut dregs was autoclaved for 20 minutes at 20 psi. The autoclaved substrate was added with or without sodium selenite (source of selenium) and distilled water to meet 80% moisture content. The substrate was incubated with Saccharomyces cerevisiae at room temperature. After 120 hours, the incubated substrate was harvested and oven-dried at 50°C for 48 hours. An in-vivo study was conducted by using 140 day-old-chicks and the birds were kept for 6 weeks. The broilers were fed 5 different experimental diets ad-libitum throughout the study. The experimental diets were control basal diet without coconut dregs, (T-1), basal diet + 2% coconut dregs (T-2), basal diet + 2% SCFCD (T-3). Basal diet + 0.4 ppm selenium derived from commercial organic selenium (T-4) and basal diet + 0.4 ppm selenium from SCFCD (T-5). The study used a completely randomized design with 5 treatment diets and 4 replications. Supplementation of diet with 2% coconut dregs (T-2) produced higher FCR, lower carcass percentage and digestible dry matter intake. Birds fed 2% coconut dregs was lighter than those of birds fed the 2% fermented coconut dregs (T-3). Body weight gain, FCR, fecal dry matter, dry matter digestibility, digestible dry matter intake and carcass percentage were improved by about 5.3, 5.4, 14.5, 12.1 and 14.8% respectively due to fermentation of coconut dregs (T-3 vs T-2). Supplementation of diets with selenium (T-4 and T-5) produced more selenium in the breast muscle and lower drip and cooking losses than the birds fed the Selenium-unsupplemented diets (T-1, T-2 and T-3). In conclusions, fermentation of coconut dregs could improve body weight gain, FCR, carcass percentage, faecal dry matter, dry matter digestibility and digestible dry matter intake. Addition of selenium in the diets could improve meat selenium, decreased the percentages of drip and cooking losses.

Keywords: coconut by-products, fermentation, poultry, Saccharomyces cerevisiae, sodium selenite

Introduction

The world’s coconut production in 2017 was 60.8 million tonnes and Indonesia was the largest coconut producer, contributing 31.2% of global coconut (FAO 2017). The kerenel or meat is the most valuable part of this nut, being 28% of the coconut. Production of coconut oil from the meat of the nut in Indonesia is through the dry and wet processes, generating copra cake and coconut dregs respectively. These two by-products are produced in the rural areas where the majority of people rely their income on the agricultural sector. Although these by-products were abundantly available in Indonesia, their uses were strictly limited just for animal feed. The utilisation of coconut by-products in poultry diets negatively affected the feeding value of the broiler diets due to the presence of mannose-based polysaccharides (Sundu et al 2012). Physical and enzymatical attempts to improve the nutritive value of these by-products come up with limited success.

Selenium has been acknowledged to be a pivotal trace mineral to improve human and animal health due to the significant role of glutathione peroxidase as an antioxidant. This antioxidant needs selenium as a primary component (Surai 2006). Several diseases, such as muscular dystrophy, myopathies of gizzard and mortality, have attacked chickens when their diets were low in selenium (Nesheim and Scott 1958; Walter and Jensen 1963). Formulating a sufficient selenium diet to maintain the health status of birds is not an easy task as most of the feedstuffs are low in selenium concentration (NRC 1994). The use of selenium-enriched feed additives in poultry diet may not be applicable to the farmer in the rural areas as the products are hard to find and costly. Therefore, finding a way that is compatible with the rural atmosphere could benefit the rural community.

Increased feeding value of agricultural by-products through fermentation has been found in copra meal (Hatta et al 2014), rice bran (Mozin et al 2019), palm kernel meal (Alshelmani et al 2016) and soybean meal (Mukherjee et al 2016). The ability of microorganisms to bioconvert fibrous and inorganic substances into readily digestible and organic compounds respectively are the two mechanisms executed by microbes (Sukaryana et al 2010). The bioconversion of non-protein nitrogen (urea) into microbial protein in the gut of ruminants (Preston and Leng 1987) is just an example of microbes capacity. The same mechanism might be used to bioconvert inorganic selenium into safer and organic form through fermentation. Saccharomyces cerevisiae was mainly used for the production of organic selenium (Demirci et al 1999). Bioconversion mechanism was through replacement of Sulphur with Selenium to produce seleno-methionine (Esmaeili et al 2012). Accordingly, a study was conducted to determine the effect of fermented coconut dregs with or without the addition of sodium selenite as a source of selenium on feed digestibility, growth performance and carcass traits of broiler chickens.

Material and methods

Fermentation of coconut dregs

Coconut dregs were collected daily from local markets. The coconut dregs were oven-dried for three days at 60°C. The dried coconut dregs were ground to 1-2 mm size and used as a solid substrate for fermentation. A complete preparation of Saccharomyces cerevisiae was purchased from the Microbiology Laboratory, Science Faculty, Tadulako University. A method of solid-state fermentation by Jacob and Prema (2006) was used in this study. The finely ground coconut dregs were autoclaved for 20 minutes at 20 psi. The autoclaved coconut dregs were cooled to room temperature and mixed with or without 0.1% inorganic sodium selenite. The mixed substrates were added with distilled water to reach 80% moisture prior to incubation. The substrates of coconut dregs were incubated with 0.1% Saccharomyces cerevisiae (equivalent to 346 CFU/g) and put the substrates in the 2-kg plastic bags for 5 days. The incubated coconut dregs were collected and oven-dried for 48 hours at 50°C. The dried fermented coconut dregs were stored for proximate analysis (AOAC 1990) and used as a feed additive. Animals and diets The study used a total of 140 – day old unsexed broiler Cobb-chicks. All the protocols used in this study were approved by the committee of animal ethic at the Faculty of Animal Husbandry and Fisheries, University of Tadulako, Palu, Indonesia. The day-old broiler chicks were kept in 5 brooder pens for a week. Vaccination against New Castle Diseases by ocular instillation was done at day 3 using Vaksimune®ND B1 to control the spread of the diseases. The chicks were then placed into 20 pens for 5 weeks at day 7. The broilers were fed basal starter diet during the first three weeks and grower diets from days 21 to 42. The basal diets as presented in Table 1 were formulated by using a software of UFFF package (Pesti et al 1986). The experimental diets used in this study can be seen in Table 2 and drinking water was available at all times. A drinker and a feeder were put in each pen. The experimental feed in the feeder was topped up at 07.00 am and 4.00 pm. The drinker, pens and surroundings were kept clean throughout the study.

Parameters measured

A number of parameters observed were: body weight gain, feed intake, feed conversion ratio, carcass, breast muscle percentage, dry matter feces, dry matter digestibility, digestible dry matter intake, selenium digestibility, meat selenium, drip loss, cooking loss and meat pH. Two broilers from each pen were randomly assigned and transferred into metabolic pens for digestibility study for a week from days 35 to 42. A plastic tray was individually placed underneath each metabolic pen. Faecal discharges were collected for three consecutive days from days 38 to 41. The faeces were collected at 08.00 am after discarding any contaminated materials. Feathers, feed particles and other contamination were removed from faeces by hand-picking prior to weighing. The faecal samples were oven-dried for three days at 50°C to measure dry matter and selenium content. The feed and faecal samples from each replicate cage were pooled and oven-dried. The ground samples were analysed for meat selenium according to the method of Almeida et al (2015). Analysis of this mineral was conducted by using an Atomic Absorption Spectrometry. The digestibilities of dry matter and selenium were determined based on the total faeces collection method.

At the end of the study, sixteen birds per treatment (i.e four birds per replicate cage) were randomly selected for meat selenium analysis. The selected broiler chickens were slaughtered by cervical dislocation. The slaughtered birds were dressed by removing the skin and feathers, neck, shank, digestive tract and organs. Breast muscle from each bird was weighed and divided into two parts for measurement of selenium and meat quality. For selenium measurement, the samples were oven-dried at 50°C for 3 days. The dried breast muscle of broiler was weighed and then finely ground for analysis of selenium.

Measurements of meat quality were drip loss, cooking loss and pH. Drip loss was measured by obtaining 50 g breast muscle. The muscle samples were placed in air-tight plastic bags for 48 h at 4°C. The exudate produced during storage was discarded and the muscle was reweighed. The drip loss was calculated as a percentage of weight muscle loss. Cooking loss was measured by placing the meat in plastic bags and then cooked in boiling water at 100°C for 20 minutes. The cooked meat was allowed to cool at room temperature for 30 minutes. The meat was weighed to determine the cooking loss. The pH of the breast muscle was determined immediately after deboning.

Experimental design and Statistical analysis

A Completely Randomized Design with 5 treatment diets and 4 replicate cages (Steel and Torrie 1980) were applied in this trial. Analysis of variance was adopted to determine the effects of experimental diets on parameters measured by using Minitab 16 statistical program (Pesti et al 1986). Any differences identified in the analysis of variance was further tested with Tukey test using the statistical software of Minitab.

Results

Results of nutrients profile of coconut dregs and fermented coconut dregs by Saccharomyces cerevisiae are presented in Table 3. Data on growth performance and carcass percentage are shown in Table 4. Results of feed digestibility, dry matter faeces, meat selenium and meat quality are presented in Tables 5 and 6.

Discussion

Effects of fermentation on nutrient profiles

Fermentation technology has successfully been used to improve the feeding value of the agricultural by-products such as palm kernel cake, rice bran (Sukaryana et al 2010) and copra meal (Hatta et al 2014). These current findings add up the consistency of the positive effect of fermentation on nutrients profile of the feedstuffs. The increased protein content of coconut dregs by 58% due to fermentation by Saccharomyces cerevisiae was found in this current study and the increase was even bigger when the substrate was added with 0.1% sodium selenite prior to fermentation. The increase in protein due to fermentation is hard to elaborate. Two possible mechanisms can be proposed. First, this might be just a matter of reduction in total biomass of coconut dregs. A 48% reduction in crude fibre content of Saccharomyces cerevisiae – fermented coconut dregs could be the reason for an increased protein of the substrate. It is mathematically that when a fraction of nutrient goes down in percentage, another fraction of nutrient increases to meet the overall 100% of the total fractions. Second, Saccharomyces cerevisiae might have the capability to absorb external Nitrogen from the air and bioconvert it into yeast protein that could increase the total protein of the coconut dregs. A study conducted by Aruna et al (2017) supported these current findings. The authors found a 6.6% increase in Yam peel protein when it was fermented by Saccharomyces cerevisiae. The above speculation of the capacity and effectivity of this yeast to bioconvert elemental or inorganic nitrogen into protein yeast needs to be proved through a further and deeper study.

Since the selenium content of sodium selenite is 45,7%, the addition of 0.1% sodium selenite into the coconut dregs prior to fermentation could logically increase selenium content of the substrate to about 457 ppm. Fermentation by Saccharomyces cerevisiae only produced 415 ppm selenium in the substrate. It was about 10% (42 ppm) of the selenium added into the substrate lost during fermentation. This might indicate that sodium selenite was metabolized by the yeast through methylation of selenite. This process could generate a waste product of hydrogen selenite and released it into the air. A very strong smell produced by the yeast throughout the fermentation process in this current study might be an indication of the production of hydrogen selenite. Addition of sodium selenite in the substrate could further increase the protein content of the coconut dregs from 9.0 to 12.8%. The reason of the increase in protein content is unclear. It is possible that the concentration of the sodium selenite used in this present study was at the proper level to increase the growth and population of this microorganism. As the yeast grew, they could use sodium selenite and bioconvert it into Seleno-amino acids. Demirci et al (1999) found that yeast Saccharomyces cerevisiae could generate up to 3000 µg seleno-methionine from 1 g Selenium.

Study on the effect of fermentation on the crude fibre content of the substrate was done by Hatta et al (2014). The authors found that the use of fungi Trichoderma viride could decrease fibre content of coconut meal by about 24 to 57 % when it was fermented for 5 days. The decreased in crude fibre content of coconut dregs due to fermentation in the present study might indicate that the fungi could utilize crude fibre for their growth as a source of energy. It can be said that once the fungi utilize the fibrous fraction of the substrate, they convert the fibrous fraction into simple carbohydrates. The bioconversion process during fermentation leads to a decrease in fibre content of the substrate and thus total biomass also decreased by about 6.5 to 7.1% in this present study.

Effects of diets on growth performance

The use of coconut dregs in broiler diets has not been practiced due to the fact that this agricultural by-product has not been present in the market. An extra effort to collect this by-product discourages animal farmers to use it in broiler diets. Addition of 2% coconut dregs did not impair the feeding value of the diet when the diet was offered to broiler chickens up to 6 weeks. Supplementation of the diet with 2% fermented coconut dregs with Saccharomyces cerevisiae improved body weight gain, compared to the 2% coconut dregs – fed broilers. The increased body weight gain of birds due to the addition of fermented feedstuffs might be through the production of simple and easily digestible products as a result of the production of enzymes by fungi during fermentation. Bahri et al (2019) stated that when coconut flour was fermented by Aspergillus niger, mannanase enzyme was generated. However, when sodium selenite was added to the coconut dregs prior to fermentation, body weight gain of broiler was not increased to the same level of fermented coconut dregs without selenium addition. Our previous study on the use of feed additive rich in selenium could significantly increase body weight of broiler chickens (Sundu et al 2019). However, these current findings could not detect a significant improvement of growth because of Sel-plex (selenium- rich feed additive) supplementation in the diet.

Feed conversion ratio of birds fed the 2% coconut dregs in the diet was impaired. Diets without coconut dregs and fermentation coconut dregs with or without the addition of organic selenium (Sel-plex) could improve the FCR. Supplementation of diets with sel-plex, coconut dregs and fermented coconut dregs did not improve feed intake. Carcass percentage of broilers fed 2% coconut dregs was 66.8%. Increased carcass percentage was found due to the supplementation of diets with fermented coconut dregs (T-3 and T-5) and sel-plex (T-4). Breast muscle percentage was not affected by the treatment diets.

A previous study on the effect of coconut meal on its digestibility was done by Sundu et al (2006). The authors found that the low digestibility of coconut meal – supplemented diets was partly due to the presence of mannan and cellulose. Those indigestible fibrous fractions were present in coconut meal with high concentration. The inclusion of 2% coconut dregs in the diet (T-2) decreased dry matter digestibility by about 8.8%. However, when the coconut dregs were fermented with Saccharomyces cerevisiae (T-3 and T-5), their 2% inclusion in the diet did not negatively affect dry matter digestibility as found in T-2. The increased digestibility of the coconut dregs-supplemented diet (T-3 and T-5) indicated that the indigestible carbohydrates present in the coconut dregs were broken down to a digestible simple fraction, compared to unfermented coconut dregs (T-2). Sukaryana et al (2010) found that microbes could convert indigestible carbohydrates into simple mono-saccharides. Since the birds fed the 2% coconut dregs-supplemented diet (T-2) had low in feed digestibility, their digestible dry matter intake was also low. Selenium digestibility of the diet, on the other hand, was not affected. Although inorganic selenium such as sodium selenite had low digestibility (Mozin et al 2019), fermentation of the sodium selenite – containing substrate (T-5) could bioconvert this inorganic mineral into seleno-protein (Demirci et al 1999) and those organic products were able to be digested in the digestive tract of broilers. Interestingly, fermentation could improve faecal dry matter. Mechanism of increased faecal dry matter of diets containing fermented coconut dregs might be through the break down of mannan and cellulose as these two poly-saccharides are hydrophilic (Sundu et al 2012).

Briens et al (2013) reported that meat selenium of broilers fed 0.3 ppm sodium selenite was 0.4 ppm. The concentration of meat selenium increased to 1.0 ppm when the birds were offered 0.3 ppm yeast selenium. The authors also found that the concentration of meat selenium was positively correlated with selenium levels in the diets (Briens et al 2013). The birds fed the diet without selenium supplementation (T-1, T-2 and T-3) possessed low meat selenium. A 41% increased in meat selenium due to supplementation of either Sel-plex (T-4) or fermented coconut dregs with additional sodium selenite (T-5) was found in this present study. Since the meat selenium concentration of birds fed the sel-plex diet (T-4) and fermented coconut dregs with the addition of inorganic selenium (T-5) was the same, it seems likely that the sodium selenite (inorganic selenium) used in this study was bioconverted into organic seleno-protein. This is because the only selenium that can be stored in the muscle tissue was in organic form. Mozin et al (2019) found that the addition of selenium in the form of sodium selenite in the diet could not increase meat selenium of broiler chickens. However, the addition of sodium selenite in rice bran before fermentation with Saccharomyces cerevisiae significantly improved meat selenium (Mozin et al 2019). According to Demirci et al (1999), yeast could convert inorganic selenium into seleno-methionine. This is the reason why fermentation of the substrates with additional inorganic selenium by yeast Saccharomyces cerevisiae in this present study and the study of Mozin et al (2019) could improve meat selenium of broilers.

The effect of fermented feedstuffs in poultry diet on meat quality has been studied by a number of workers (Alshelmani et al 2016; Sugiharto et al 2017). The utilization of fermented feedstuffs did not affect the cooking and drip losses of the meat (Alshelmani et al 2016). Water in muscle was mainly located in extracellular space, being 90-95% (Honikel and Hamm 1994). This extracellular water was loosely bound and thus is more easily lost than intramyofibrilliar water and interfacial water. Excessive tissue water loss could downgrade the meat quality and thus has been used as meat quality indicators. Oxidative stress could occur at a postmortem state and lead to tissue damage. The production of glutathione peroxidase due to the presence of selenium in the muscle tissue could prevent oxidative stress, tissue damage (Combs 1981), decreased meat shelf life and increased tissue water loss (Combs and Regenstein 1980). It is for those reasons, supplementation of the coconut dregs diets with selenium (T-4 and T-5) in the present study could lower drip loss and cooking loss, compared to the meat of birds fed the coconut dregs without selenium supplementation. The muscle of birds fed the coconut dregs (T-2) lost more water than others. It is interesting to note the broiler chickens fed the diet supplemented with commercial selenium and the diet supplemented with fermented coconut dregs with selenium addition had an insignificant difference in the cooking loss. It seems likely that the selenium from commercial feed additive (T-4) and fermented coconut dregs with selenium addition possessed the same properties and quality. However, Meat pH was not affected by the experimental diets.

Conclusions

• Fermentation of coconut dregs could improve growth performance, carcass percentage, fecal dry matter, dry matter digestibility and digestible dry matter intake.
  
  
• Supplementation of the diets with selenium could improve meat selenium, decreased the percentages of drip and cooking losses.
  
  
• Addition of fermented coconut dregs with the addition of selenium prior to fermentation produced the same effect as the diets with the addition of commercial selenium feed additive on the improvement of growth performances, feed digestibility and meat quality to the same level of produced lowered drip loss and cooking loss.

Acknowledgement

We are so much indebted to the Ministry of Research, Technology and Higher Education of the Republic of Indonesia for providing financial support enabling us to conduct this research. Support for the research was made by The University of Tadulako, Faculty of Animal Husbandry and Fisheries was made for the research facilities. We owe so much debt to our students, who collected the coconut dregs from the local market, conducted fermentation task, ground feedstuffs, mixed diets, and took care of the birds throughout the study.

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Received 17 September 2019; Accepted 25 September 2019; Published 2 November 2019

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