Cocoa pod husk with enzyme supplementation is a potential feed ingredient in broiler diets

T N Nortey, I Ewusi, L A Kpogo^§, E O K Oddoye¹ and A Naazie²

Department of Animal Science, College of Agriculture and Consumer Sciences, University of Ghana, P. O. Box LG 226 Legon, Accra. Accra.
tnortey@ug.edu.gh
¹ Cocoa Research Institute of Ghana, P. O. Box TF 8, New Tafo-Akim.
² Livestock and Poultry Research Centre, University of Ghana, P. O. Box LG 38, Legon
^§ Present address: Maridav Ghana Ltd, PMB KA 144, Airport, Accra-Ghana.

Abstract

The aim of the trial was to evaluate the performance of broilers fed diets containing varying levels of cocoa pod husk. The diets were supplemented with either phytase, an enzyme cocktail or both. Three hundred and sixty Cobb broiler day-old chicks were randomly assigned to 12 experimental treatments, replicated three times in a Completely Randomized Design (CRD). The diets had three levels of CPH inclusion; 0%, 5% and 7.5% (starter), and 0%, 7% and 10% (finisher) and these were further sub-divided into four. Each portion was treated with, i) no enzyme, ii) phytase (200g per ton of complete feed) only, iii) a commercial enzymes cocktail (250g per ton of complete feed) only and iv) a combination of both enzymes. At the end of the trial on day 57, six birds per treatment were used for carcass analysis.

There were no significant differences (P>0.05) among the treatment diets for any of the production parameters studied. Dressing percentages for birds on 0, 7 and 10% CPH, and without enzymes were 72.9, 65.0 and 61.2% respectively and these were lower (P<0.05) than that for birds on diets supplemented with a combination of phytase plus an enzyme cocktail (73.2, 73.2 and 69.8% respectively). The dressing percentage of birds fed on enzyme treated diets was better (P<0.05) than that for birds fed on diets without added enzymes (72.03 vs 66.36% respectively). Cocoa pod husk plus exogenous enzymes can effectively be used as an ingredient in broilers diets without adversely affecting performance or cost of production.

Keywords: broilers, carcass characteristics, cocoa pod husk, enzymes, performance

Introduction

Feeding animals under intensive conditions is expensive and accounts for 65-70% of the total cost of animal production (Dozier III et al 2008). This makes animal proteins like, meat, eggs and milk expensive. Competition between man and livestock for some foodstuffs/feed ingredients, particularly energy sources results in high costs of feed ingredients. As a result alternatives like local agro industrial by-products and farm residues are increasingly being used as sources of energy for monogastric animals such as pigs and poultry (Teguia et al, 2004). One such by product is cocoa pod husk. It is a major by-product of cocoa farming, (Alemawor et al 2009) and forms over 70% (w/w) of the whole matured fruit of cocoa. It is highly fibrous and contains significant amounts of cell wall components such as lignin (14%) non-starch polysaccharides (NSP), mainly hemicelluloses (11%), cellulose (35%) and pectin (6%) (Alemawor et al 2009). Monogastrics do not produce enzymes that degrade these cell wall components (Li et al 1996), and the presence of these undigested polysaccharides in the gastro-intestinal track can result in an increase in digesta viscosity or and increase/decrease in digesta passage time. This can cause inefficient nutrient absorption and/or a reduction in feed intake with resultant adverse effects on growth and productivity.

Supplementing high fibre diets with fibre-degrading enzymes can reduce the diets’ negative effects on monogastrics’ performance. The positive effects of fibre-degrading enzymes are more pronounced in diets containing higher levels of NSP like barley, compared to diets which have less fibrous ingredients like maize (Nortey et al 2008).

Approximately two-thirds of the phosphorous in plant feedstuffs is present as phytate phosphorous (Adeola et al 2004). Phytate phosphorous can ionically bind minerals and proteins and in the process make them unavailable (Selle et al 2000). Phytate phosphorous is also poorly digested by monogastrics including pigs and poultry because they do not secrete phytase, the enzyme which is responsible for hydrolysing phytate. Even if they do, monogastrics possess phytase in very small quantities (Golovan et al 2001). In addition to improving phosphorous availability, phytase improves the availability of amino acids (Nortey et al 2007). Hence for monogastric diets which are based mainly on plant sources, it is important to add exogenous phytase to improve phosphorous utilization (Bedford and Schulze 1998; Nortey et al 2007).

In most West African countries including Ghana, Nigeria and Cote d’Ivoire, the use of exogenous enzymes, particularly phytase by the larger feed mills is not uncommon . This partly addresses the issue of phytate unavailability. However, equally important is the fact that increasingly, many farmers and feed mills are relying on non-conventional/highly fibrous feedstuffs which contain high levels of NSP. The lack of routine addition of exogenous fibre-degrading enzymes and phytase to such feeds, can result in poor nutrient utilization, and ultimately large amounts of undigested nutrients being excreted into the environment.

It was hypothesized that CPH together with exogenous enzymes can effectively be used as a feed ingredient in diets for broilers without adversely affecting performance and carcass characteristics. The objectives of this study therefore were to determine the effect of exogenous enzyme supplementation in diets with added (CPH) on average daily feed intake (ADFI), average daily gain (ADG), feed conversion efficiency (FCE), final body weight (FBW), carcass and gastro-intestinal characteristics.

Materials and Methods

The trial was carried out at the Livestock and Poultry Research Centre (LIPREC), School of Agriculture, College of Basic and Applied Sciences (CBAS) of the University of Ghana (UG). A full list of abbreviations used in this manuscript and their full meanings are provided at the end in “Appendix Table 1”.

Processing of cocoa pod husk

Cocoa pod husk was obtained from the Cocoa Research Institute, Ghana and were chopped into slices (average size of 2 cm) and pre-dried in the sun for about 24 hours to reduce moisture to about 80%. The pre-dried slices were passed through a combination mincer and pelleting machine to produce pellets. The pellets were dried for a further 48 – 72 hours to produce dried pellets of 10-12mm in diameter with about 10% moisture.

Experimental diets

Twelve experimental diets were formulated to contain 0%, 5% and 7.5% (starter), and 0%, 7.5% and 10% (finisher) CPH, respectively. For each level of CPH inclusion, the diets were further divided into four parts. Parts one, two, three and four were treated with, i) no enzyme, ii) phytase alone (300g/ton of complete feed), iii) a commercial enzyme cocktail alone (250g/ton of complete feed), and iv) a combination of both phytase and the cocktail enzyme, respectively. The microbial phytase used was ZY Phytase 5000© (Lohmann Animal Health, Germany). This was added at a rate of 200g/tonne of finished feed to diets that required phytase. The final phytase activity in the feed was 250FTU/kg. (One FTU [Phytase Unit] is the quantity of enzyme which liberates one micromole of inorganic phosphate per minute from sodium phytate at pH = 5.5 and 37°C). The enzyme cocktail used was Enziver (Pfizer) and contains phytase, amylase, protease, cellulose, xylanase, β-glucanase and pectinase. It was added at a rate of 250g per ton of finished feed. The set-up of the starter and finisher diets used showing CPH levels and combination of enzymes (T1 – T12) are shown schematically in Tables 1a and 1b, respectively. The composition of the diets are shown in Tables 3 and 4, and were based on NRC (1994) nutrient requirements of poultry.

Experimental birds and design

The animal protocol used followed principles recommended by the Institutional Animal Care and Use Committee of the Noguchi Memorial Institute for Medical Research, University of Ghana. Three hundred and sixty day-old broiler chicks were randomly assigned to the twelve (12) experimental diets in a Completely Randomised Design (CRD) with three (3) replicates per treatment. There were 30 birds in each treatment and 10 birds per replicate. Each replicate group of broilers was brooded for three weeks and then housed in deep litter pens measuring 2m x 2m x 2m. The birds were individually weighed at the start of the experiment and subsequently on a weekly basis. Birds in each replicate were given a known amount of feed and water on a daily basis. Feed leftover was weighed the next day prior to the day’s feeding in order to determine feed disappearance. The leftover feed was then discarded and fresh feed provided. Standard routine vaccination protocols were strictly adhered to. The birds were fed with the experimental starter diet for 28d after which they were switched onto the finisher diet. The whole trial lasted 56d; performance and feeding records were recorded and summarized on a weekly basis. These included average daily feed intake (ADFI), average daily gain (ADG), feed conversion efficiency (FCE) and final body weight (FBW).

Carcass analysis

At 18:00 hrs on day 57 of the trial, three birds from each replicate were randomly selected and tagged for carcass analysis. The birds were starved for 12hrs and at 06:00hrs on day 58, they were weighed. Subsequently they were slaughtered by jugular venipuncture (Osei et al 2010). They were de-feathered after scalding in boiling water and immediately transferred into a cold room where they were stored overnight at -4°C. The next day, the whole chilled carcasses were weighed. Weights of some internal organs (including liver, full and empty intestines, and gizzard) were taken. Abdominal fat which had solidified following the overnight chilling was carefully separated and the weight recorded.

Chemical analysis

Samples of all the major feed ingredients were ground to pass through a 1mm sieve in a hammer mill (Retsch SM100, F. Kurt Retsch GmgH & Co. KG). Samples for analysis were weighed using a top loading balance (ADAM AAA 250LE) with a sensitivity of 0.001g. Dry matter was determined using AOAC method (method: 930.15; AOAC, 1995). Crude protein was determined according to method 942.05 (AOAC 1995). Crude fat was analyzed by the soxhlet method (method: 920.39; AOAC 1995). Ash was determined after ashing in a muffle furnace at 6000C (method 965.17; AOAC 1995).

Statistical analysis

All the data were analysed using the Generalised Linear Model procedure of the Statistical Analysis Systems Institute (SAS 2008). Significant differences among means were separated using the Student Newman-Kuels (SNK) Test.

A priori, it was decided to compare the following contrasts which were of particular interest, using orthogonal contrasts:

• All diets without enzymes versus all diets with both phytase plus cocktail
• All diets without enzymes versus all diets with only a cocktail
• All diets without enzymes versus all diets with only phytase
• All diets with only phytase versus all diets with only a cocktail
• All diets with phytase alone versus all diets with both phytase plus a cocktail
• All diets with only a cocktail versus all diets with both phytase and a cocktail

Results

Table 1 shows the chemical composition of CPH. The diets used in the experiment, showing CPH levels and combination of enzymes (T1 – T12) are shown schematically in Table 2.

The compositions of the broiler and finisher diets, with their respective calculated nutrient values are shown in Tables 3 and 4.

Production parameters

There were no differences among the experimental diets for any of the production parameters studied (ADFI, ADG, FCE and FBW; Table 5). For diets with 0 (T1-T4), 5 - 7.5 (T5-T8) and 7.5 – 10% (T9-T12) CPH inclusion, ADFI ranged from 99.1 – 100.3, 96.6 – 100.7 and 99.1 – 108.3 g/day, respectively. Similarly FBW for these diets ranged from 2.07 – 2.17, 1.85 – 2.24 and 1.81 – 2.23 kg, respectively. On the average, ADG for birds fed the three levels of CPH inclusion were 41.1, 41.3 and 41.5g/d respectively, while FCE averaged 0.38 overall. As the inclusion level of CPH increased, the cost per kg (Ghana Cedi: GH₵) of diet reduced despite the addition of exogenous enzymes. However, the cost to produce one kg live weight was not different among the treatments. A. priori contrasts to compare diets of specific interest indicated no differences in the treatments for all the production parameters studied, (Table 6).

Carcass characteristics

Results of carcass characteristics are shown in Table 7. With the exception of liver, empty intestinal and fat weights, all other carcass parameters (dressing percentage, carcass, gizzard and full intestinal weights) showed differences among treatments. Birds on T5, T6, T9 and T10 recorded the lowest carcass weights, ranging from 1.15 to 1.35kg while birds on T4 (0% CPH) and with both phytase and a cocktail, recorded the highest carcass weights (1.76kg). Carcass weights of birds on all the other treatments were not different from either the heaviest or the lightest birds. With the exception of T1 to T4 where no CPH was included in the diets, birds on treatments with CPH showed decreasing gizzards weights when enzymes were added. Thus at the 5 – 7.5% CPH inclusion levels, gizzards of birds fed no enzyme, phytase alone, enzyme cocktail alone, and phytase plus enzyme cocktail decreased in weight from 71.23 to 57.71g. Similarly, at the 7.5 - 10%.

Generally, birds on higher levels of CPH (7.5 -10%: T9, T10, T11 and T12) had heavier full intestinal weights ranging from 135.2 to 168.6g, compared to birds on diets with lower levels of CPH.

A priori orthogonal contrasts between treatments of specific interests showed differences for dressing percentage, carcass, gizzard and full intestinal weights (Table 8). For carcass weights, the average weight of all birds fed on only a cocktail enzyme was 1.48kg and this was lower than birds fed a combination of both a cocktail and phytase + cocktail (1.61kg). Dressing percentage of all birds fed diets containing no enzyme was 66.1% and this was lower than birds fed a diet with a combination of phytase + cocktail (72.1%). Also dressing percentage of birds fed on phytase alone (69.4%) or a cocktail alone (69.4%) was lower than dressing percentage of birds fed a combination of cocktail and phytase + cocktail.

When no enzyme was added to the diets, full intestinal weight was 137.8g and this was heavier than full intestinal weight of birds that had both phytase + cocktail enzymes added to the diets (125.23g). Adding phytase also resulted in lower full intestinal weights compared to when no enzyme at all was added (131.63 vs. 137.77g). Birds on diets with a combination of both phytase + cocktail had a full intestinal weight of 125.23g which was lighter than birds fed on diets with only phytase (131.63g), or diets with only enzyme cocktail (140.0g).

Discussion

None of the production parameters measured (ADFI, ADG, FCE, FBW, and cost per kg of live weight gain) was influenced by the treatments. This suggests that at the current levels of inclusion, neither cocoa pod husk nor enzymes affected these traits.

Effect of cocoa pod husk

Generally gut-fill permitting monogastrics, like broilers, will eat to meet their nutrient, principally energy, needs when offered feed ad libitum (Whitney et al 2006; Lan et al 2008). In an experiment to determine the effect of diets containing different levels of cocoa pod husk on broiler performance, Alemawor et al (2010) observed that feeding higher levels of CPH resulted in higher ADFI. This they attributed to a dilution in the energy content of the feed with increasing levels of CPH. Of the three main diets used in this study, those with more CPH had slightly less energy and more fibre. This was because CPH has less energy and more fibre than wheat bran, which it replaced in the diets. It can be speculated that the expected effects of higher fibre levels (higher feed intake due to a dilution effect) were not observed probably because the dilution effect of CPH was not so severe as to cause an increase in ADFI. Average daily feed intake is one of the biggest influences on final body weight and feed conversion efficiency (Ferket and Gernat 2006). The lack of significant differences in FBW and FCE is therefore due to similarities in ADFI.

Effect of enzyme addition

The average P content of the CHP used in the trial was 0.4%. Wheat bran on the other hand has an average P content of 0.9% of which 80% is phytate P. It was not possible to calculate the phytate P content of the CPH used in this trial.

However, if it is assumed that its phytate P content was close to 100%, it can be seen that replacing wheat bran with CPH will result in a phytate P content that will not be worse than the treatments without CPH. Feeding nutrient-restricted diets to pigs resulted in an increase in ADFI (Nortey et al 2013) because of the phenomenon where monogastrics increase their ADFI in an attempt to meet their daily nutrient requirements. In that trial, addition of phytase resulted in a reduction in ADFI, to levels similar to the control diet due to what the authors referred to as an “uplift” in nutrient availability upon enzyme addition. For the current trial any such “uplift” that might have occurred when phytase was added was not sufficient to cause a resultant reduction in ADFI.

The cocktail enzyme used in this trial contained, in addition to phytase, other enzymes like xylanase, cellulase, amylase and β-glucanase. This latter group of enzymes degrade fibre and release energy. Their efficiency is based on viscosity reduction and demasking which refers to the breaking down of water insoluble pentosans found in cell walls (Brufau et al 2006). Inevitably both mechanisms (viscosity-reduction and demasking) result in a release of energy when fibre degrading enzymes are added to monogastric diets. For this trial, any energy that might have been released upon enzyme addition was not high enough to cause a resultant drop in ADFI. The lack of any difference in the cost to produce a kg of live weight among the treatments is a direct result of similar feed intakes and FCE and suggests that CPH could be an alternative to WB, without affecting productivity or cost.

In a priori contrasts, adding either phytase alone, an enzyme cocktail alone, or a combination of both enzymes resulted in a better carcass weight and a better dressing percentage compared to when no enzyme at all was added. This was due directly to lighter full-intestinal weights. These results suggests that addition of enzymes resulted in faster transit times which resulted in less residual feed in the GIT at the time of slaughter. Although in this trial, the type of fibre and digesta transit time were not measured, it can be speculated that the type of fibre was of the type that slowed down transit time. This is evident from the results which indicated that at the time of slaughter, full intestinal weights of birds on diets without enzymes was heavier than that of birds fed diets with enzymes in spite of a 12-h feed withdrawal prior to slaughter.

Treatments with added enzymes resulted in birds with lower gizzard weights compared to treatments without enzymes. This may be because these enzymes, in facilitating a faster rate of intestinal emptying, may be sparing the gizzard some amount of grinding, thus leading to less musculature and hence weight.

Comparing the effect of phytase alone versus that of a cocktail alone indicated that phytase addition was better than a cocktail in reducing full intestinal weights. However when either phytase alone or a cocktail alone were compared to a combination of phytase + cocktail, the latter was better at reducing full intestinal weights than either phytase or a cocktail alone. These results seem to indicate that the nature and type of NSP presented by the local feed ingredients, and particularly CPH may be such that there is a slowing down of intestinal transit time, and that the recommended enzyme application rates may not be adequate to reverse this trend.

Generally an increase in the amount of soluble fibre in the diet results in a lowering of abdominal fat in broilers (Saki et al 2011; Shirzadi et al 2009; Moharrery 2006). This may be because soluble NSP in the GIT can cause a reduction in nutrient, particularly fat absorption. In this trial no differences in abdominal fat content were found among birds on the different treatments. It can be concluded that the type of fibre in CPH, was either non-soluble, or if soluble was not enough to elicit the effect of a reduction in abdominal fat.

Conclusions

• Cocoa pod husk was included in diets for broilers up to a level of 7.5 and 10% (starters and finishers respectively) without affecting production parameters.
  
  
• Exogenous phytase and a combination cocktail enzyme improved the dressing out percentage of broilers fed diets based on cocoa pod husk

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Received 8 March 2015; Accepted 25 March 2015; Published 1 May 2015

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