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In poultry production systems, feed cost represents up to 70% of the total cost of production (Martínez et al. 2020). On the other hand, the cost of raw materials used in the formulation has risen due to increasing demand for biofuels and the global economic crisis, mainly in developing countries, which have directly influenced on profitability of poultry industry (Hejdysz et al. 2020). Therefore, it is urgent to find low-cost alternative feedstuffs to replace conventional feed resources, like corn and soybean meals for poultry birds with the aim of ensuring animals that produce quality food for consumers and achieving significant economic benefits (Valdivié et al. 2020).
In developing countries where corn and soybean meal are scarce, agricultural byproducts can be affordable for using as feed material (Gkarane et al. 2020). Palm kernel meal (PKM) (Elaeis guineensis Jacq) has been identified as one of the most demanded alternative feed ingredients by poultry producers (Abdollahi 2016). Generally, PKM has an average crude protein, crude fat and metabolizable energy (ME) contents from 120 to 160 g/kg, 40 to 90 g/kg and 1816 to 2653 kcal/kg, respectively (Ramachandran et al. 2007 and FEDNA 2010). Although PKM is a good energy source for poultry, it is deficient in essential amino acids, such as lysine, methionine, and tryptophan (Sulabo et al. 2013). On the other hand, a high crude fibre content (140 to 350 g/kg) could limit the use of PKM as the main protein source in poultry feed (FEDNA 2010 and Son et al. 2014).
The use of PKM in broiler diets has been widely studied with or without supplementation of enzymes, synthetic amino acids, and fishmeal (Sulabo et al. 2013, Abdollahi 2016; Chen et al. 2018). However, the optimum level of inclusion of PKM in broiler chicken rations has not been completely elaborated because of difference in the commercial line of chickens used, environmental aspects and characteristics of the PKM used such as the origin, oil extraction process and nutrient composition (Jang et al. 2013 and Huang et al. 2018).
Due to its chemical composition, PKM has been classified as a protein source for animal feed. In this study, it is hypothesized that an adequate inclusion of PKM in broiler diets replacing corn meal and imported soybean meal in isoproteic and isoenergetic diets could satisfy the nutritional requirements of poultry birds without affecting the bioproductive indicators and the edible portion yields with a positive economic balance. The objective of this research was to determine the growth performance, carcass traits and economic response of Cobb 500® male broiler upon feeding of palm kernel with traditional feed.
Materials and Methods
Location. The experiment was approved by the Animal Care and Use Committee of Technology Transfer Research Center. The experiment was carried out at the Poultry Experimental Unit “San Marcos”, Pichincha province, Pedro Vicente Maldonado Canton, Ecuador. The experimental location is 1600 m above sea level, has a humid subtropical climate with an average annual temperature between 24 to 28 0C and mean annual rainfall of 2800 mm.
Birds and diets. In this study, 120 one-day-old Cobb 500® male broiler chickens, average weight of 40.10 g (SD 0.28 a were randomly distributed to four dietary treatments and fed the rations for a period of 47 days in four phases (starter, 0 to 8 days; grower, 9 to 18 days; finisher 1, 19 to 28 days and finisher 2, 29 to 47 days). There were 30 chickens per treatment with three repetitions and 10 birds per repetition. The four isoproteic and isoenergetic diets were formulated according to Rostagno (2005) for broiler Cobb 500® with different levels of the PKM, with a control diet (T0) and other diets contain 100 g/kg (T1), 200 g/kg (T2) and 300 g/kg (T3) of PKM (table 1). The experimental diets were formulated according to research by Vieira et al. (2008), Sulabo et al. (2013) and Modesto et al. (2020). The metabolizable energy of palm kernel meal (9.19 MJ/kg) reported by Vargas and Zumbado (2003) was taken into account.
Table 1 Diet formulation, nutritional composition, and cost of the experimental diets (as-fed basis)
| Ingredients (g/kg) | Experimental diets | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Starter (0 to 21 days) | Grower (22 to 35 days) | Finisher (36 to 47 days) | ||||||||||
| T0 | T1 | T2 | T3 | T0 | T1 | T2 | T3 | T0 | T1 | T2 | T3 | |
| Palm kernel meal | 0.00 | 100.00 | 200.00 | 300.00 | 0.00 | 100.00 | 200.00 | 300.00 | 0.00 | 100.00 | 200.00 | 300.00 |
| Corn meal | 531.40 | 426.23 | 320.24 | 215.78 | 535.11 | 432.46 | 329.98 | 228.64 | 565.79 | 461.88 | 355.22 | 248.77 |
| Soybean cake meal | 402.44 | 383.31 | 364.60 | 345.00 | 380.00 | 358.80 | 336.93 | 320.00 | 350.00 | 329.80 | 312.00 | 294.00 |
| Premixture1 | 5.00 | 5.00 | 5.00 | 5.00 | 5.00 | 5.00 | 5.00 | 3.00 | 5.00 | 5.00 | 5.00 | 5.00 |
| Salt | 5.00 | 5.00 | 5.00 | 5.00 | 5.00 | 5.00 | 5.00 | 3.00 | 5.00 | 5.00 | 5.00 | 5.00 |
| Soybean oil | 24.30 | 49.00 | 74.00 | 98.50 | 45.70 | 70.00 | 94.60 | 117.30 | 48.10 | 72.60 | 97.50 | 122.40 |
| Choline chloride | 0.70 | 0.70 | 0.70 | 0.70 | 0.70 | 0.70 | 0.70 | 0.70 | 0.70 | 0.70 | 0.70 | 0.70 |
| DL-Methionine | 2.26 | 2.36 | 2.46 | 2.52 | 1.90 | 1.97 | 2.12 | 2.14 | 1.51 | 1.58 | 1.66 | 1.75 |
| L-Lysine HCL | 0.00 | 0.50 | 0.90 | 1.30 | 0.00 | 0.47 | 0.97 | 1.32 | 0.00 | 0.45 | 0.84 | 1.24 |
| Calcium carbonate | 10.10 | 9.70 | 9.30 | 8.80 | 7.70 | 7.10 | 6.60 | 6.20 | 5.50 | 5.10 | 4.60 | 4.20 |
| Dicalcium phosphate | 18.80 | 18.20 | 17.80 | 17.40 | 18.89 | 18.50 | 18.10 | 17.70 | 18.40 | 17.89 | 17.48 | 16.94 |
| Cost (kg/t) | 0.558 | 0.526 | 0.494 | 0.461 | 0.563 | 0.530 | 0.498 | 0.457 | 0.561 | 0.529 | 0.497 | 0.465 |
| Crude protein | 210.00 | 210.00 | 210.00 | 210.00 | 200.00 | 200.00 | 200.00 | 200.00 | 190.0 | 190.0 | 190.0 | 190.0 |
| Methionine | 5.50 | 5.50 | 5.50 | 5.50 | 5.00 | 5.00 | 5.00 | 5.00 | 4.50 | 4.50 | 4.50 | 4.50 |
| Lysine | 11.90 | 11.90 | 11.90 | 11.90 | 11.29 | 11.29 | 11.29 | 11.29 | 10.57 | 10.57 | 10.57 | 10.57 |
| Crude fibre | 35.09 | 49.13 | 63.16 | 77.20 | 34.26 | 48.29 | 62.31 | 76.57 | 34.01 | 48.05 | 62.09 | 76.14 |
| Crude fat | 66.60 | 91.52 | 116.71 | 141.46 | 87.18 | 111.76 | 136.63 | 159.85 | 90.09 | 114.84 | 139.93 | 165.03 |
| Metabolizable energy (MJ/kg) | 12.55 | 12.55 | 12.55 | 12.55 | 13.18 | 13.18 | 13.18 | 13.18 | 13.39 | 13.39 | 13.39 | 13.39 |
| Calcium | 10.00 | 10.00 | 10.00 | 10.00 | 9.00 | 9.00 | 9.00 | 9.00 | 8.00 | 8.00 | 8.00 | 8.00 |
| Available phosphorus | 4.01 | 4.01 | 4.01 | 4.01 | 4.00 | 4.00 | 4.00 | 4.00 | 3.90 | 3.90 | 3.90 | 3.90 |
1Addition per kg of starter diet: Mn, 100 mg; I, 1 mg; Fe, 40 mg; Zn, 100 mg; Se, 0.15 mg; Cu, 10 mg; vitamin A, 15,000 IU; vitamin D3, 5000 UI; vitamin E, 75 mg; vitamin K3, 4 mg; vitamin B1, 3 mg; vitamin B2, 8 mg; vitamin B6, 5 mg; vitamin B12, 0.016 mg; biotin, 0.2 mg; folic acid, 2 mg; nicotic acid, 60 mg; pantothenic acid, 18 mg; choline, 1800 mg. Addition per kg of grower diet: Mn, 100 mg; I, 1 mg; Fe, 40 mg; Zn, 100 mg; Se, 0.15 mg; Cu, 10 mg; vitamin A, 12,000 IU; vitamin D3, 5000 UI; vitamin E, 50 mg; vitamin K3, 3 mg; vitamin B1, 2 mg; vitamin B2, 6 mg; vitamin B6, 4 mg; vitamin B12, 0.016 mg; biotin, 0.2 mg; folic acid, 1.75 mg; nicotic acid, 60 mg; pantothenic acid, 18 mg; choline, 1600 mg. Addition per kg of finisher diet: Mn, 100 mg; I, 1 mg; Fe, 40 mg; Zn, 100 mg; Se, 0.15 mg; Cu, 10 mg; vitamin A ,12,000 IU; vitamin D3, 5000 UI; vitamin E, 50 mg; vitamin K3, 2 mg; vitamin B1, 2 mg; vitamin B2, 5 mg; vitamin B6, 3 mg; vitamin B12, 0.011 mg; biotin, 0.05 mg; folic acid, 1.5 mg; nicotic acid, 35 mg; pantothenic acid, 18 mg; choline, 1600 mg.
Experimental conditions. Birds were raised in floor pens on wood shavings with a stocking density of 10 birds/m2. Feed and water were offered ad libitum, in tube feeders and nipple drinkers, respectively. During the first three weeks, supplemental heat was provided by use of an electric heater. A lighting system with 12 hours of artificial light provided by a 60-watt electric bulb and 12 hours of natural light was used. In the hatchery, birds were vaccinated against fowl pox, infectious bronchitis, Newcastle disease and infectious bursal disease. No medication was added to the feed, nor therapeutic drugs were used during the experimental period.
Performance parameters. Body weight and feed intake of birds in each pen were determined on day 47. Feed conversion ratio was calculated as the amount of feed intake to gain one kg body weight. Livability was determined as the difference between the initial number of birds and recorded mortality. To determine the intake of nutrients and metabolizable energy, the accumulated feed intake and the nutritional contributions of the experimental diets were taken into account (Modesto et al., 2020).
Carcass traits. At day 47, 10 birds per treatment was sacrificed by bleeding of the jugular vein after six hours of feed fasting (water was offered ad libitum) to collect samples. Carcass traits were determined by weighing the birds before slaughter. After which carcass, breast, leg, total viscera and abdominal fat were weighed (Martínez et al. 2019). The relative weight of the edible portions was calculated by the formula: Relative weight = (Absolute weight x 100)/final body weight.
Chemical analyses. Dry matter (DM), crude protein (CP), crude fat, crude fibre (CF) and nitrogen-free extract contents were determined by AOAC (2006). Calcium (Ca), magnesium (Mg) and potassium (K) contents were determined by atomic absorption with a GBC Scientific Equipment XplorAA Dual, Australia, 2014, whereas phosphorus (P) and sulfur (S) contents were determined by visible spectrophotometry-colorimetry using a Spectronics-USA spectrophotometer, model Genesys, USA, 2006, range: 325 to 1100 nm. All chemical analyses were performed by triplicate.
Cost-benefit analysis. To determine the cost of experimental diets, the prices of PKM (0.11 USD/kg), corn meal (0.50 USD/kg), soybean meal (0.60 g/kg), vitamins and trace minerals premix (4.75 USD/kg), salt (0.20 USD/kg), plant oil (0.80 USD/kg), choline chloride (2.57 USD/kg), DL-methionine (1.24 USD/kg), L-lysine HCL (2.57 USD/kg), calcium carbonate (0.02 USD/kg) and dicalcium phosphate (0.08 USD/kg) were taken into account at the time of the trial. For the cost-benefit calculation, the economic-mathematical method was used with techniques of grouping, comparison and calculation of magnitudes (Modesto et al. 2020). For the calculation of the feed cost per kg of live weight, carcass, breast and leg, the average diet cost in the different phases of production (starter, grower, finisher 1 and finisher 2) were used.
Statistical analysis. Results of PKM nutritional composition were expressed as descriptive statistics (X, SD). Data obtained from growth performance, carcass trait and cost benefit analyses were subjected to analysis of variance (ANOVA) according to a completely randomized design (three repetitions per treatment). Duncan (1955) multiple range test was used to determine differences between means. SPSS statistical program, version 23 (2014) was used.
Results and Discussion
Table 2 shows the chemical composition of PKM, which varies in relation to other studies due to the origin of the raw material (Adli et al. 2020, da Silva et al. 2020 and Purnama et al. 2020), extraction process mechanical or chemical oil (Boateng et al. 2020 and Purnama et al. 2020), variety and age of palms, latitude, altitude, precipitation, topography, texture, soil structure, solar radiation, photoperiod, temperature, soil fertility, among other factors (Qureshi et al. 2019, Bhagya et al. 2020 and Rakesh et al. 2020). The PKM showed a crude protein of 167.9 g/ kg, favorable as a source of vegetable protein for broiler chickens (Sugiharto et al. 2019, Wickramasuriya et al. 2019 and Vatanparast et al. 2020), although the levels of crude fiber should be noted of 201.1 g/kg that could affect the digestibility of nutrients (Oladokun et al. 2016, Goh et al. 2020) and the growth of these birds (Abdollahi et al. 2019 y Saadatmand et al. 2019).
Table 2 Chemical composition of palm kernel meal (as-dry basis)
| Chemical composition (g/kg) | Mean | Standard deviation |
|---|---|---|
| Dry matter | 915.0 | 0.52 |
| Crude protein | 167.9 | 0.15 |
| Crude fat | 73.30 | 0.23 |
| Crude fibre | 201.10 | 0.18 |
| Ashes | 102.80 | 0.31 |
| Nitrogen-free extract | 454.90 | 0.56 |
| Calcium | 3.80 | 0.23 |
| Phosphorus | 5.10 | 0.15 |
| Magnesium | 3.10 | 0.13 |
| Potassium | 8.20 | 0.19 |
| Sulfur | 1.70 | 0.01 |
PKM: TYSAISA Plant, Agricultural Extractor Río Manso EXA S.A, Km 51 Santo Domingo, La Concordia, Quininde, Ecuador.
PKM was progressively included (100, 200 and 300 g kg) in isoprotein and isoenergetic diets for the nutrition of Cobb 500® broiler chickens (table 2). It was possible to partially replace corn and soybean meal, with a high contribution of CF and GF as PKM increased, although the contributions of methionine, lysine, calcium and available phosphorus were supplied for this species according to Rostagno (2005).
Table 3 shows the growth performance of broilers feed with an increasing levels of palm kernel meal (PKM). Throughout the experimental period, the viability did not affect by dietary treatments (100%), which indicates that PKM is not toxic or lethal antinutritional factor in current research. This observation is supported by other studies using high levels of PKM (Sulabo et al. 2013 and Abdollahi 2016). In addition, the inclusion with 100 g/kg (T1) was not statistically different from T0 (P˃0.05), although T2 and T3 did show a lower result in the growth indicators and daily feed intake per bird (P <0.05), although the intake of fiber and fat was different in all the experimental treatments (P <0.05). There is no significant effect of T1 treatment on feed intake, nutrient intakes, feed conversion ratio and final live weight of the birds compared with control, whereas crude fibre and crude fat intake progressively increased with PKM (table 3). However, T2 treatment with PKM in the diet at 200 g/kg increased (P < 0.05) feed intake and feed conversion ratio but had no effect on the final live weight of birds. On the other hand, T3 treatment increased feed intake and feed conversion ratio and reduced the final live weight of the birds.
Table 3 Live performance of Cobb-500® broilers fed different palm kernel meal levels
| Items | Inclusion of PKM (g/kg) | SEM± | P-value | |||
|---|---|---|---|---|---|---|
| T0 | T1 | T2 | T3 | |||
| Feed intake (g/bird/day) | 139.75b | 143.74ab | 145.15a | 145.79a | 1.307 | 0.044 |
| Feed conversion ratio (kg/kg) | 2.08b | 2.15b | 2.30a | 2.41a | 0.041 | 0.002 |
| Final live weight (g) | 2778.67a | 2760.00a | 2604.20ab | 2495.57b | 31.743 | 0.035 |
| Dry matter intake (g/bird/day) | 129.59b | 133.28ab | 134.27a | 134.99a | 1.206 | 0.050 |
| Metabolizable energy intake (kcal/bird/day) | 435.03b | 447.46ab | 451.83a | 453.85a | 4.068 | 0.044 |
| Crude protein intake (g/bird/day) | 27.41b | 28.19ab | 28.47a | 28.59a | 0.51 | 0.044 |
| Methionine intake (g/bird/day) | 0.67b | 0.69ab | 0.69ab | 0.70a | 0.006 | 0.044 |
| Lysine intake (g/bird/day) | 1.54b | 1.58ab | 1.59a | 1.60a | 0.014 | 0.044 |
| Calcium intake (g/bird/day) | 1.20b | 1.24ab | 1.25a | 1.26a | 0.011 | 0.045 |
| Available phosphorus (g/bird/day) | 0.64b | 0.66ab | 0.66a | 0.67a | 0.006 | 0.046 |
| Crude fibre intake (g/bird/day) | 4.74d | 6.97c | 9.15b | 11.32a | 0.058 | <0.001 |
| Crude fat intake (g/bird/day) | 13.93d | 15.59c | 16.99b | 18.34a | 0.138 | <0.001 |
a,b,c,dMeans followed by different letters in each row as significantly different at P < 0.05 (Duncan 1955)
It has been observed a negative effect on body weight gain and feed conversion as the inclusion level of PKM was increased in the feed intake (table 3). However, 100 g/kg of PKM in the feed intake resulted in similar body weight gain and feed conversion as the control group, with a good intake of essential amino acids and of crude fiber lower than the inclusion of 20 and 30% in the diet (table 3), which maintained the normal biological cycle of these birds. Apparently, the current study showed that this level of PKM inclusion was appropriate for use in all stages of broiler production.
The dilution of energy by dietary fibre (Savón et al. 2007) could increase the voluntary feed intake observed in diets with 200 and 300 g/kg of PKM. This increase in food intake due to the high content of dietary fiber has previously been observed to compensate for the loss of endogenous nutrients (Savón et al. 2007 and Rodríguez et al. 2020). Likewise, Rogel et al. (1987) found that a higher voluntary feed intake of chickens was associated with an increase in insoluble fiber in the diet, which is necessary to compensate for the reduction in the absorption of nutrients in the intestinal lumen and the restriction of the mobility of the minerals. Also, a higher inclusion of PKM (up to 300 g/kg) resulted in more use of soybean oil in the diets (table 2) necessary to balance the ME requirements in the diets (Latshaw 2008, Lefevre et al. 2012 and Martínez et al. 2015).
In this sense, T2 and T3 with high contribution and intakes of CF and crude fat (table 2) could affect the live weight and feed conversion. Dietary fiber in this feed ingredient was characterized by indigestible compounds by non-ruminant animals (Daud and Jarvis 1992). Likewise, Savón et al. (2007) and Iyayi et al. (2005) showed that excess fibre reduces nutrient digestibility, energy retention and mineral movement, which affects growth performance. Aya et al. (2013) found that diets containing up to 400 g/kg of PKM reduced the digestibility of DM, CP, crude fat, ash and nitrogen-free extract. These authors justified it to a higher contribution and crude fibre intake.
Results of Mardhati et al. (2011) and Bello et al. (2011), who included PKM up to 200 and 450 g/kg in broiler (Ross 308® and Cobb 500®) diets, respectively, found similar results in the bio-productive indicators. Ezieshi et al. (2008) reported a deterioration of body weight and feed efficiency in a study of broilers with 300 and 325 g/kg of PKM in the starter and finisher diets, therefore these authors recommended that when including PKM at increasing levels in animal diets, it should be supplemented with essential amino acids. However, other studies are needed to corroborate the interaction of biomolecules and fibre contributions in PKM diets (Mardhati et al. 2011).
The use of palm kernel meal on broiler diets did not affect the edible portions yields (%). However, T0 and T1 exerts significant effects on the absolute weight of the carcass, breast, leg, and viscera compared significantly with the T2 and T3 (P < 0.05; table 4). Inclusion of PKM at 100 g/kg in the diet partially replaced corn and the soybean meal, but did not suppress the yield of the edible portions in broiler. This could be because this treatment guaranteed a stable intake of nutrients, especially of amino acids such as lysine and methionine that influences the synthesis of breast in relation to other muscles and in growth of connective tissue, respectively (Berri et al. 2008).
Table 4 Weight and yield of edible parts and total viscera of Cobb-500® broilers fed different levels of palm kernel meal
| Items | Inclusion of PKM (g/kg) | SEM± | P-value | |||
|---|---|---|---|---|---|---|
| T0 | T1 | T2 | T3 | |||
| Carcass weight (g) | 2026.83a | 1991.33ab | 1963.50b | 1891.50c | 12.832 | <0.001 |
| Carcass yield (%) | 73.20 | 73.12 | 72.88 | 71.97 | 0.358 | 0.629 |
| Breast weight (g) | 451.00a | 432.50ab | 421.90b | 399.17c | 4.940 | <0.001 |
| Breast yield (%) | 22.25 | 21.74 | 21.49 | 21.11 | 0.193 | 0.205 |
| Leg weight (g) | 656.50a | 634.00a | 612.50ab | 566.53b | 10.103 | 0.005 |
| Leg yield (%) | 32.39 | 31.87 | 31.19 | 29.98 | 0.458 | 0.287 |
| Total viscera weight (g) | 156.33a | 151.00ab | 148.23b | 140.47c | 1.654 | 0.002 |
| Total viscera yield (%) | 5.65 | 5.54 | 5.50 | 5.34 | 0.052 | 0.216 |
| Abdominal fat (g) | 72.60 | 72.60 | 71.02 | 70.67 | 0.846 | 0.122 |
| Abdominal fat (%) | 2.62 | 2.67 | 2.64 | 2.67 | 0.044 | 0.856 |
a,b,cMeans followed by different letters in each row as significantly different at p<0.05 (Duncan 1955). Carcass is considered here with no viscera, head, or feet. Breast, leg, and total viscera yields are expressed as carcass percentage.
However, T2 and T3 decreased the yield of edible portions that might be related to a high concentration of fibre that suppressed feed conversion and body weight gain of the birds (Riber and Tahamtani 2020). High fibre content in diets decreases digestion and absorption of nutrients, and may inflame the small intestine (Fasuyi 2020) thereby negatively influencing protein deposition in body tissues. Results of the current study are supported by those of Beloshapka et al. (2016), who found significant reductions (P < 0.05) in the absolute weight of the carcass when increasing the fibre levels on broiler diets.
The high variability in the chemical composition of PKM and the many variants for its formulation within the diet directly influences growth performance responses and the carcass traits. Many authors have argued on role of the concentration of fibre in PKM. In this study, negative effects on growth performance responses and the carcass traits were observed when using PKM with 201.1 g/kg of CF at an inclusion level superior to 100 g/kg in the diet. Okeudo et al. (2006) used PKM with lower CF content and indicated that the inclusion of 350 and 300 g/kg of PKM did not negatively affect the relative weight of the organs and the carcass. On the contrary, García et al. (1999) reported that the inclusion of 100 g/kg of PKM with 249.0 g/kg of CF reduced the weight and yield of the carcass and breast.
Table 5 shows that an increase in PKM levels in the broiler diets decreased (P < 0.05) the cost of the feed, the feed cost to produce one kg of live weight, the carcass, breast and leg, with economic utilities. At present, the economic feasibility study is essential when alternative feeds are used in animal diets that substitute imported raw materials such as corn and soybean meals since feed represents the highest portion of the cost of production. For the most part, researchers agree that PKM reduces the feed cost/bird with considerable economic gain, although these gains will be influenced by the cost of other raw materials in each production area (Onwudike 1986).
Table 5 Cost-benefit analysis of Cobb-500® broilers fed different levels of palm kernel meal (47 days)
| Items | Inclusion of PKM (g/kg) | SEM± | P-value | |||
|---|---|---|---|---|---|---|
| T0 | T1 | T2 | T3 | |||
| Cost of feed consumed (USD) | 3.24a | 3.11b | 2.84c | 2.51d | 0.029 | 0.005 |
| Feed cost/kg of live weight (USD) | 1.19a | 1.14ab | 1.11b | 1.02c | 0.022 | <0.001 |
| Utility/control (USD) | - | 0.05 | 0.08 | 0.17 | - | - |
| Feed cost/kg of carcass (USD) | 1.60a | 1.56a | 1.45b | 1.33c | 0.014 | <0.001 |
| Utility/control (USD) | - | 0.04 | 0.15 | 0.27 | - | - |
| Feed cost/kg of breast (USD) | 7.19a | 7.19a | 6.72b | 6.30c | 0.066 | <0.001 |
| Utility/control (USD) | - | 0.00 | 0.47 | 0.89 | - | - |
| Feed cost/kg of leg (USD) | 4.94a | 4.90a | 4.63b | 4.44c | 0.045 | <0.001 |
| Utilily/control (USD) | - | 0.04 | 0.31 | 0.50 | - | - |
a,b,c,dMeans followed by different letters in each row as significantly different at p<0.05 (Duncan 1955)
Thus, PKM can be considered as a strategy of food self-sufficiency. Shakila et al. (2012) used 75 g/kg of PKM in diets for broilers and found a lower feed cost per kg of live weight gain compared to control. Likewise, Onwudike (1986) showed an economic efficiency by decreasing feed cost and cost production using PKM up to 350 g/kg on broiler diets. However, although the T2 and T3 reduced the growth performance and the edible portions (table 3 and 4), the cost reduction (table 2) of these diets caused a higher economic utility as also observed by Okeudo et al. (2006) and Onwudike (1986). This shows that use of this alternative feed promotes economic gains in poultry production.
Conclusions
The results of this experiment showed that the dietary inclusion of up to 100 g/kg of palm kernel in the diet of Cobb 500® male broiler, as a partial substitute for corn and soybean meal, did not negatively affect the growth performance, carcass traits and economic benefit. In addition, the inclusion levels of 300 g/kg of the palm kernel meal had the best cost-benefit analysis.
