Introduction

Palm kernel cake (PKC) is a by-product result from producing palm oil from oil palm (Elaeis guineensis Jacq) and is a one of the potential feed ingredients in broiler rations. In Sri Lanka, oil palm cultivation expands to a total extent of 7780 ha at present and annual production is nearly 2500 -3000 Mt. Most of the palm oil produced in Sri Lanka is exported, but PKC is not utilized and it is a potential feed ingredient in animal feeding (Kumara, 2014). Palm kernel cake has the ability to supply both energy and protein needs of the animals, but most of the scientists consider PKC as a medium grade protein source and good energy source (Boateng et al., 2008). It is more suited to incorporate in ruminant diets due to high fiber content (Sundu et al., 2006) and its’ use in monogastric diets is limited. However, PKC is used in poultry rations in most of the countries in the world (Szebiotko, 1981). Among different alternatives, PKC which has the ability to supply both energy and protein needs can be used to minimize the cost of production of Sri Lankan broiler industry. However, inclusion quantities of PKC as feed ingredient in to broiler feed rations are not clearly evaluated yet. Therefore, the aim of this study was to evaluate the potential use and suitability of PKC as a feed ingredient in broiler rations and to find out the optimum level of inclusion into broiler rations.

Materials and Methods

Experimental Animals, Design and Management

The study was conducted at Veterinary Research Institute (VRI) Gannoruwa, Peradeniya, Sri Lanka. Three hundred Cobb 500, day old broiler chicks were randomly allotted into five treatments incorporating, PKC at levels of 0%, 5%, 10%, 15% and 20%. Each of the treatment was replicated four times, with fifteen birds per replicate in a Completely Randomized Design (CRD).

Day old chicks were introduced to pre-heated brooder pens and brooded up to the second week. Electrical bulbs (100W) and paddy husks were used as heat source and litter material, respectively. Just after chicks were introduced to brooder pens, glucose and vitamin (Chick tonic) were supplied with drinking water and vitamin supplement was continued for first seven days.

Feed Preparation and Feeding

Five experimental diets were formulated using different ingredients including PKC according to the NRC (1994) recommendations for starter and finisher rations (Table 1). Ingredients were weighted separately and macro and micro ingredients were mixed well. Then, oil was incorporated in to the mixture. Treatment diets were mixed weekly and stored properly until feeding. Feeds and water were made available to the birds ad libitum. Broiler starter and finisher rations were fed from d 1 – d 21 and d 22- d 42, respectively.

Analysis of Feed Samples

Feed samples (100 g) were collected randomly after the mixing of feeds. Those samples were grinded and stored in plastic bottles until analyzed. The proximate composition of the experimental diets and PKC were determined according to the procedures of the Association of Official Analytical Chemists (AOAC, 2005).

Table 1: Ingredient Proportions of the Experimental Diets

Slaughtering of Birds

At the end of the study period, five chicks were randomly selected from each pen and each chick was weighted. Birds were sacrificed and hanged until bleeding was completed. Then, carcasses were scalded, defeathered and eviscerated and each carcass was weighed. The intestinal contents were collected into a tube and mixed well with a small spatula. Then the digests were transferred into micro centrifuge tubes and centrifuged at 6500 ppm for 5 min. The clear supernatant (0.5 mL) was transferred into the cup of the viscometer and viscosity was measured at 30°C by using a digital viscometer (Brookfield; model: DV II, UK). Prior to measure the samples, viscometer was calibrated and checked the calibration using 0.5 mL distilled water (should read as 1 cP).

Data Collection and Analysis

Amount of feed allocated per pen, refusals and body weights were measured weekly throughout the study period. Feed intake, weight gain, feed conversion ratio (FCR) and dressing percentage of the birds were calculated. Observed data were analyzed using one way Analysis of Variance (ANOVA) procedure of Statistical Software for Data Analysis (ver. 9.0) (SAS, 2002) to evaluate the best incorporation level of PKC. Mean separation was done by Tukey’s Studentized Range Test (TSRT) and statistical significance was declared at P < 0.05.

Result and Discussion

Proximate Composition of Palm Kernel Cake

According to Olomu (1995) and Sundu et al. (2006), crud protein content of PKC range between 14 – 21% and the PKC used in our study stayed in the range (14.6%). However, crude protein content of PKC can be vary with the processing method. Results indicated that used PKC had comparatively higher amount of crude fiber (17.4%) and reported crude fiber content by Olomu (1995) was 12.29% whereas it was less than the values reported (21 – 23%) by Sundu et al.(2006). They showed that crude fiber content of PKC can be vary with the type of palm kernel used, method of separating shell from the kernel and the amount of shell left in the kernel before use and observed variation in crude fiber content may be related to above factors. Crude fat, ash and dry matter contents of used PKC were reported as 17.4%, 4.5% and 91.1% respectively and not varied much from the values reported by Sundu et al. (2006).

Proximate Composition of Treatment Diets

Crude protein content was a higher in starter ration compared to finisher ration (Table 2). Comparatively lower crude fiber contents were observed in control (0% PKC) diet and it was slightly increased with increasing levels of PKC in the treatment diets. Crude fat contents were also increased with increasing PKC levels in both starter and finisher diets. Palm kernel cake is not a common feed ingredient in non-ruminant rations. High fiber content and low metabolizable energy values of PKC limit its utilization as a feed ingredient in poultry rations (Sharmila et al., 2014). However, considering its crude protein content, it can be classified as a medium grade protein source. Later studies indicated monogastric animals such as boilers could tolerate high levels of PKC with proper balancing of other dietary ingredients (Yeong, 1983). Moreover, feeding value of PKC is further reduced by high shell contents under local processing. These factors have limited the inclusion rate of PKC in poultry rations to 20% (Omer et al., 1998).

Table 2: Proximate Composition of Treatment Diets

Effect of Treatments on Weight Gain

There were significant differences (P < 0.05) in weight gains of birds fed with different PKC levels in their diets during the starter and entire study period (Table 3). In both starter and total study period weight gain of birds fed with diet containing 5%, 10% and 15% PKC were significantly higher (P < 0.05) than birds fed with 20% PKC. Increasing levels of PKC result high levels of crude fiber content in diets which reduce the palatability, availability of amino acids and energy (Onwudike, 1986). It may be contribute to reduce the weight gain of birds fed with higher levels of PKC. Also it is reported that PKC contain 30% of -Mannan which is considered as an anti-nutritive factor can cause depression in feed conversion ratio and reduce weight gains by 20-25% in poultry (Omer et al., 1998).

Effect of Treatments on Feed Intake

Feed intake of birds fed with five dietary treatments in starter, finisher and total study periods were significantly different (P < 0.05, Table 3). Feed intake of birds fed with 15% PKC in the diet was significantly higher (P < 0.05) compared to birds fed with 0% PKC in starter, finisher and total study period. Further, both in finisher and total study periods, feed intakes of birds fed with 15% PKC in the diet were significantly higher (P < 0.05) compared to the birds fed with 5% PKC in their diet. Inclusion of palm oil with PCK may increase the palatability and that may be the reason for observed higher intakes, compared to control treatment. However, 20% PKC in the diets may reduce the intake with higher fiber contents.

Effect of Treatments on Feed Conversion Ratio (FCR)

During starter period, FCR of birds fed with diets containing 0% PKC and 5% PKC were significantly lower compared to the FCR of birds fed with diet containing 20% PKC (Table 3).

Table 3: Growth of Broilers Fed with Diets Containing Different Amounts of Palm Kernel Cake

^a,b,c Means within the same row with different superscripts are significantly different (P < 0.05)

Comparatively, birds fed with 20% PKC levels in the ration were shown significant higher (P < 0.05) FCR compared to the birds fed with lower PKC levels during the total study period. The feed conversion ratio of broilers was not significantly affected with the inclusion levels of PKC at 5%, 10% and 15% during the starter period compared to control and results were confirmed the earlier findings of Onwudike (1986). However, Panigrahi and Powell (1991), showed significant reduction in FCR with high levels of PKC in the diets. Further, significant difference of FCR could be noticed among the treatments during finisher stage and the best and poor FCR were noticed in moderate and higher PKC included groups respectively (Shakila et al., 2012).

Effect of Treatments on Dressing Percentage, Total Fat Deposition, Liver Weight and Gut Viscosity

Dressing percentage, total fat deposition liver weight and gut viscosity of the birds fed with different levels of PKC were not significantly different (P > 0.05) among the birds fed with different treatment diets (Table 3). However, numerically the birds fed with 0% PKC in the diet showed less fat deposition compared to birds fed with PKC in their diets and presence of high fat content in PKC may contribute to the fat deposition.

Conclusion

Inclusion of PKC up to 15% in broiler ration improve the feed conversion and weight gains and despite high fiber content, PKC can also be incorporated into broiler ration up to 15% with balancing of all other nutrients.

Suggestion

The quality of PKC can be enhanced to make it more suitable for poultry feeding, and inclusion levels should be exploited in broiler rations.

References

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