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It is known that feeding represents up to 70% of production costs in poultry industry (Mahammad et al. 2019). In Central America and the Caribbean, egg production depends on corn and soybean imports, as fundamental raw materials in the ration of laying hens. Due to the global pandemic of COVID-19, which led to the restriction of the importation of these inputs, and the high competitiveness in poultry industry, prices for acquiring food ingredients (corn and soy) and feed intended for laying hens (USDA 2020) have substantially increased, which makes it impossible to produce eggs with economic profitability for many companies.
Currently, poultry industry is considering new alternatives for feeding animals. It is about finding local resources, available throughout the year, with affordable prices for farmers, that do not affect the genetic potential of animals, and that generate tangible economic gains (Valdivie et al. 2020). Honduras is the third largest producer and exporter of palm oil in Latin America, and the eighth worldwide, only surpassed by Ecuador and Colombia. According to SAG (2018), the country currently has 190 thousand hectares sown with oil palm, with a production of 2.4 million tons of fruit and 480 thousand tons of crude oil.
Palm kernel meal, which is the by-product resulting from oil extraction of the fruit, could be an effective food alternative for poultry industry. Its chemical composition is highly variable and depends on the oil extraction method, palm kernel species and the amount of shell that remains in the meal (Pérez et al. 1999). This food by-product contains between 13 and 18% crude protein and between 18 and 28% crude fiber (Botello et al. 2020).
According to Sundu et al. (2006), palm kernel meal does not contain aflatoxins or toxic antinutritional components. However, its high crude fiber content limits its use in monogastric animals (especially birds), although, at suitable inclusion levels, it favors animal productivity. According to Yusrizal et al. (2013), the inclusion of 30% improves the competitive exclusion and intestinal health of laying hens. Chong et al. (2008) pointed out that the use of 25% palm kernel meal with exogenous enzymes did not decrease feed conversion and egg production. Alvarenga and Amador (2020) demonstrated that the dietary use of 20% of palm kernel meal, without the use of multienzyme compounds, maintained laying intensity and egg quality of laying hens.
Genetic companies recommend that it is profitable to use laying hens with a laying intensity greater or equal to 70%, at 100 weeks of age (Hendrix-Genetics 2018). However, many poultry companies, due to the cost of layer replacement and the technological flow to keep eggs in the market, maintain the animals in production for more than 100 weeks, in order to achieve economic profitability in this productive stage. Given this situation, it is advisable to partially replace imported foods, such as corn and soybean, with others that are available at low prices, with appropriate protein, energy and fiber content.
Based on these conditions, the objective of this study was to evaluate the effect of the inclusion of palm kernel meal on productivity improvement, egg quality and economic feasibility of old laying hens (100 to 120 weeks of age).
Materials and Methods
Experimental location. The study was carried out at the poultry research and teaching center of Zamorano Pan-American Agricultural School, Zamorano, located 32 km Southeast of Tegucigalpa, in San Antonio de Oriente municipality, Francisco Morazán department, Honduras. This facility is located at an altitude of 800 m a.s.l., with an average annual temperature of 26 °C and precipitation of 1,100 mm per year.
Animals, experimental design and treatments. A total of 240 old 100-week-old laying hens, of Dekalb White® genetic line, were used. They were distributed according to a completely randomized design for 20 weeks, with two treatments, four repetitions per treatment and 30 animals per repetition. Treatments consisted on a control diet, and one with the inclusion of 20% of palm kernel meal. The results of Alvarenga and Amador (2020) were considered to select the inclusion level of palm kernel meal that was used in the experiment.
Palm kernel meal had a chemical composition of 16.11% crude protein, 24.77% crude fiber, 0.27% Ca, 0.16% available P, 0.24% digestible lysine, 0.32% digestible methionine + cystine, and 0.26% digestible threonine, according to analysis in a NIR equipment, AMINONIR® brand (Germany), with a calibration equation: agPALM07_54058_v6. Diets were formulated according to the nutritional requirements described in the manual of genetic line used (table 1) and a value of 1,125 kcal of ME / kg was used for palm kernel meal, as reported by FEDNA (2015).
Table 1 Ingredients and nutritional contributions of laying hens (100 to 120 weeks)
| Ingredients, % | Control diet, without palm kernel | Diet with palm kernel meal |
|---|---|---|
| Corn meal | 62.70 | 37.50 |
| Soybean meal | 24.63 | 21.40 |
| Palm kernel meal | 0.00 | 20.0 |
| Choline chloride | 0.05 | 0.05 |
| African palm oil | 0.30 | 8.55 |
| Mineral and vitamin premix1 | 0.20 | 0.20 |
| Salt | 0.35 | 0.35 |
| Monocalcium phosphate | 1.67 | 1.70 |
| Fine calcium carbonate | 4.30 | 4.24 |
| Thick calcium carbonate | 5.25 | 5.18 |
| Mycofix plus 5.0® | 0.12 | 0.12 |
| DL-methionine | 0.25 | 0.37 |
| L-lysine | 0.10 | 0.22 |
| L-threonine | 0.08 | 0.12 |
| Proximal composition (%) | ||
| ME, kcal/kg | 2,700 | 2,700 |
| Crude protein | 17.00 | 17.00 |
| Crude fiber | 2.83 | 6.21 |
| Neutral detergent fiber | 8.19 | 18.39 |
| Available P | 0.49 | 0.49 |
| Ca | 4.20 | 4.20 |
| Lysine | 0.82 | 0.82 |
| Methionine + Cystine | 0.75 | 0.75 |
| Threonine | 0.60 | 0.60 |
1Mineral and vitamin premix: vitamin A, 1,000 IU/kg; vitamin D3, 2,000 IU/kg; vitamin E, 30 IU/kg; vitamin K3, 2,0 mg/kg; vitamin B1, 1,0 mg/kg; vitamin B2, 6,0 mg/kg; vitamin B6, 3,5 mg/kg; vitamin B12, 18 mg/kg; niacin, 60 mg/kg; pantothenic acid, 10 mg/kg; biotin, 10 mg/kg; folic acid, 0,75 mg/kg; choline, 250 mg/kg; iron, 50 mg/kg; copper, 10 mg/kg; zinc, 70 mg/kg; manganese, 70 mg/kg; selenium, 0,30 mg/kg; iodine, 1,0 mg/kg
Experimental conditions. Each repetition consisted of a pen of 5.92 m2 (1.6 m wide × 3.7 m long), with 30 hens per pen and a bed of chopped corn rachis, at a rate of 5.07 animals/m2. The animals received 110 g/bird/day of feed in hanging cone feeders and the water was offered ad libitum in automatic drinking troughs. An amount of 16 hours of light were provided every day and no therapeutic veterinary care was used during the experimental stage.
Productive performance. To determine egg weight, 50 eggs were collected weekly per each treatment, between 8:30 a.m. and 9:30 a.m. Eggs were weighed on an OHAUS® digital technical balance (New Jersey, USA), with a precision of ± 0.1 g. Mortality was determined according to dead birds divided by the animals that started the experiment. Food intake was determined three times a week, according to the offer and reject method. For laying intensity, total production of eggs/week/treatment was considered. One housed egg/day/bird was assumed to be 100%. Mass conversion was calculated using the formula:
Egg external and internal quality. At weeks 110 and 120, 50 eggs were collected per each experimental treatment. All eggs were collected at the same time and transferred to the laboratory of the research and teaching center of Zamorano Pan-American Agricultural School. Egg quality was analyzed on the same day of collection using an automatic TSS EggQuality analyzer (York, England) and Eggware v4x program.
Eggshell resistance (middle pole) to rupture was measured with a QC-SPA® resistance analyzer (York, England). For shell thickness (middle pole), a QC-SPA® micrometer screw (York, England) was used, with ± 0.001 mm precision.
Egg internal quality and albumen height were determined using a QHC® height analyzer (York, England), with ± 0.01 mm precision. Haugh units were calculated with the formula HU = 100 * log (H + 1.7W0.37 + 7.6), where HU is Haugh unit, H is albumin height and W is egg weight. Yolk color was evaluated using a CCC® electronic colorimeter (York, England), which considers the Roche scale of 15 colors.
Economic feasibility. To determine the cost of food consumed and the cost to produce an egg, the economic-mathematical method with grouping and comparison techniques was used. For the application of this method and its techniques, ingredient cost sheets, invoices, reception reports and economic analyzes of the feed factory and the research and teaching center of Zamorano Pan-American Agricultural School were used.
Statistical analysis. Data was analyzed by t-Student test for two independent samples. In addition, yolk color was determined by the non-parametric U-Mann Whitney test. P <0.05 values were taken to indicate significant differences. SPSS 23.0.1.2014 program (SPSS Inc., Chicago, IL, USA) was used for statistical analyzes. In addition, dirty eggs were determined by comparison of proportions, using COMPRAPRO 1.0® program (Font et al. 2007).
Results and Discussion
Table 2 shows the effect of the inclusion of palm kernel meal (20%) on productivity of old laying hens (100 to 120 weeks). The use of palm kernel meal increased (P <0.05) laying intensity and feed intake and reduced mass conversion and the percentage of dirty eggs. However, live weight, egg weight and mortality (0% data not shown) did not change due to the effect of experimental treatments (P> 0.05).
Table 2 Effect of the inclusion of palm kernel meal on productivity of old laying hens (100-120 weeks)
| Productive indicators | Experimental diets | SE± | P Value | |
|---|---|---|---|---|
| Control | Palm kernel meal | |||
| Laying intensity, % | 66.17 | 71.36 | 0.929 | 0.001 |
| Food intake, g/bird/d | 103.12 | 108.41 | 0.529 | 0.001 |
| Egg weight, g | 63.74 | 63.33 | 0.297 | 0.334 |
| Mass conversion, kg/kg | 2.45 | 2.40 | 0.012 | 0.015 |
| Liveweight, g | 1,731.15 | 1732.87 | 0.582 | 0.809 |
| Dirty eggs, % | 3.73 | 1.53 | 0.085 | 0.001 |
One of the objectives of this study was to verify whether the use of 20% palm kernel meal could increase laying intensity by more than 70%, to justify the rearing of these laying hens at the age of decrepitude. Clearly, the use of this feed by-product promoted laying intensity by 5.19%, without causing deaths (100% viability) in laying hens. This confirms the criteria of Sundu et al. (2006), who report that this product does not have toxic secondary metabolites that cause mortality. Apparently, this food has chemical benefits, capable of improving intestinal health and increasing the productivity of laying hens.
According to Yusrizal et al. (2013), the use of palm kernel meal (30%) improved the count of Lactobacillus spp. and reduced the growth of Escherichia coli and cecal pH, which favored the ileal digestibility of protein and the reduction of NH3 in the excreta of laying hens. According to Rodríguez et al. (2018), non-starch polysaccharides in the diet can positively influence on growth of lactic acid bacteria, since many of these indigestible compounds have prebiotic functions. Cadillo et al. (2019) stated that palm kernel meal has a high content of β-glucans, and that the use of this raw material (20 to 25%) in the feeding of birds improves the immune activity and intestinal health of these animals. Khan et al. (2020) recommended the use of β-glucans in animals to increase the production of short-chain fatty acids in the ceca, the genetic expression of binding proteins, and immunological homeostasis. It is possible that the use of this by-product (palm kernel meal) in diets of old laying hens had a prebiotic effect, capable of modifying cecal intestinal microflora and benefiting intestinal health. However, other studies are needed to confirm this hypothesis.
Other authors have recommended the use of exogenous enzymes, such as β-glucanases, cellulases, proteases and β-mannanases, when using high levels (> 25%) of palm kernel meal in diets for layers (Cadillo et al. 2019), which are greater than those used (20%) in this study (table 1). Ngouana et al. (2020) also reported that the use of palm kernel meal with exogenous enzymes improved digestibility of crude fiber and reduced food viscosity in the digestive tract, which caused greater contributions of energy, proteins, amino acids, phosphorus and calcium in diets destined for birds in full laying peak (Rodríguez et al. 2018). Apparently, older layers with lower nutritional requirements, and fed with 20% of palm kernel meal, do not require the use of exogenous enzymes, considering the positive productive results shown in table 2.
Tan et al. (2013) found that palm kernel meal has an in vitro antimicrobial effect against some pathogenic Bacillus species, due to the high content of peptides related to soluble lauric acid. Chen et al. (2020) observed that the use of peptides, as functional additives in diets of laying hens, had a positive influence on productivity and diversity of the intestinal microbiota.
Although results are not conclusive, in this experiment, it seems that low molecular weight peptides in palm kernel meal could have contributed to the improvement of egg production, feed intake and mass conversion (table 2).
A possible improvement in intestinal health demands a greater intake of nutrients for egg formation (Martínez et al. 2012), as occurred in laying hens fed 20% palm kernel meal, whose feed intake increased by 5.13% (table 2). In addition, the highest inclusion of African palm oil in the diet, with the purpose of correcting the metabolizable energy deficit due to partial substitution of corn meal, could favor palatability and the reduction of feed dust. Studies of Samsudin et al. (2016) reported an increase of feed intake with greater inclusion of palm oil, when up to 35% of palm kernel meal was used.
Although food intake increased with palm kernel meal, egg weight did not improve (table 2). According to Nuraini et al. (2019), balanced intake of proteins, methionine, linoleic acid and minerals such as calcium and phosphorus influenced on egg weight. It should be noted that, in the formulation of isoaminoacidic diets (table 1), digestible amino acids were considered, with emphasis on sulfur, which are the ones that most influence egg weight (Reda et al. 2020). In addition, layers had a similar liveweight (table 2), which is another determining factor in this indicator (Valdivié et al. 2020). Cuello et al. (2017) also indicated that the ingested nutrients favor egg production regarding egg weight, as an instinct to perpetuate the species, as occurred in this experiment. Similar results reported Sundu et al. (2006), Cadillo et al. (2019) and Alvarenga and Amador (2020), when they used palm kernel meal up to 25% in diets for laying hens.
Another interesting result is that the diet with palm kernel meal reduced dirty eggs in laying hens (table 2). Although various factors affect these unfit eggs, nutritional factors are considered as defining. It is known that ingredients that increase diet viscosity provoke feces with a pasty texture, which stains the cloaca and dirties the eggs (Cadillo et al. 2019). Such effects are associated with feed with high content of non-starch polysaccharides. Apparently, the use of high contents of vegetable oil (8.55%) in diets with palm kernel meal (table 1) reduced passage speed of digesta and, in turn, the viscosity of food in the gastrointestinal tract, according to Martínez et al. (2015). These results are similar to those dictated by the genetic line for 100-week-old laying hens (Hendrix-Genetics 2018). This food ingredient has the nutritional qualities to be used in diets of laying hens up to 120 weeks old.
Table 3 shows the effect of the inclusion of palm kernel meal on the external and internal quality of the egg of laying hens (100 to 120 weeks). At week 110, palm kernel meal significantly increased yolk pigmentation (P <0.05), although the other external and internal quality indicators did not change due to the effect of experimental treatments (P> 0.05). Also, in week 120, this alternative food modified rupture resistance, yolk color and shell thickness. No significant differences (P> 0.05) were found in egg weight, albumen height and Haugh unit.
Table 3 Effect of the inclusion of palm kernel meal on egg quality of old laying hens (100-120 weeks)
| Egg quality | Experimental diets | SE± | P value | |
|---|---|---|---|---|
| Control | Palm kernel meal | |||
| Week 110 | ||||
| Egg weight, g | 61.34 | 62.14 | 0.932 | 0.545 |
| Albumin height, mm | 8.34 | 8.78 | 0.213 | 0.178 |
| Haugh unit | 90.21 | 92.22 | 1.184 | 0.236 |
| Rupture resistance, kg/cm2 | 4377.5 | 4358.8 | 5.165 | 0.100 |
| Shell thickness, mm | 0.30 | 0.27 | 0.007 | 0.080 |
| Yolk color |
3.00 (0.484) |
4.00 (0.802) |
<0.001 | |
| Week 120 | ||||
| Egg weight, g | 62.25 | 64.31 | 1.175 | 0.224 |
| Albumin height, mm | 9.84 | 10.13 | 0.344 | 0.550 |
| Haugh unit | 97.65 | 98.5 | 1.598 | 0.710 |
| Rupture resistance, kg/cm2 | 3850.75 | 4272.25 | 33.948 | 0.006 |
| Shell thickness, mm | 0.32 | 0.35 | 0.008 | 0.004 |
| Yolk color |
3.00 (0.500) |
4.00 (0.516) |
0.007 | |
( )= standard deviation
The results of albumen height show that the inclusion of 20% of palm kernel meal with a high crude fiber content (24.77%) did not probably decrease the absorption of amino acids like lysine, methionine and threonine, essential for the synthesis of protein from the albumen (albumien, ovomucin, ovomucoid, conalbumin and lysozymes), since this portion of the egg is made up of water and proteins (Secci et al. 2020). It has been found that a deficiency of methionine and lysine, mainly, reduces albumen weight and decreases concentration of all free amino acids (Whitehead 1995). These results agree with those obtained by Adrizal et al. (2011), who found no significant effect on albumen height when including 15 and 30% palm kernel meal in diets for laying hens. Alvarenga and Amador (2020) indicated that the inclusion of 10, 15 and 20% of palm kernel meal, with and without enzymes, did not modify albumen height in the eggs of laying hens. However, Afolabi et al. (2012) reported that inclusion levels between 20 and 50% of palm kernel meal decreased albumen height, with respect to reports of these authors in the control diet and the inclusion of 10% of palm kernel meal. Due to the partial substitution of soybean meal (3.23%) for palm kernel meal, to obtain an isoaminoacidic diet, it is necessary to increase the synthetic amino acids by 0.12, 0.12 and 0.04% of DL-methionine, L-lysine and L-threonine, respectively.
Haugh unit is a standard method for checking internal quality and egg freshness (Iqbal et al. 2017). It is determined by considering egg weight and albumen height. These indicators did not have notable changes (P> 0.05) when 20% of palm kernel meal was used in the diet, which did not statistically modify the HU (P> 0.05) either. Both experimental treatments showed optimal values of UH (≥ 90) (table 2). Hisasaga et al. (2020) stated that values between 90 and 100 of HU indicate eggs of excellent quality. Other studies with palm kernel meal in diets for laying hens did not show changes in this indicator of internal egg quality (Adrizal et al. 2011 and Alvarenga and Amador 2020).
Regarding yolk color, the inclusion of 20% palm kernel meal in the feeding of old laying hens significantly increased (P <0.05) yolk color intensity in both evaluated weeks (110 to 120). Despite the fact that corn meal is rich in zeaxanthins and was partially replaced in 25.2% (table 1) by palm kernel meal, this did not cause a decrease of yolk color (table 3). On the contrary, the use of high contents of African palm oil, as an energy corrector rich in xanthophylls (Afolabi et al. 2012), increased yolk color (1) according to Roche scale. The yellow color of the yolk has been related to xanthophyll content of diets. Thus, the higher the level of palm oil in the diet, the greater the intensity of yellow pigment in yolk, and the higher the yolk color score (Titcomb et al. 2019).
Shell quality includes thickness and resistance, and both indicators decrease with the age of birds, due to a decrease of calcium metabolism that causes its lower incorporation in the form of calcite in shell formation (Wistedt et al. 2019). This study showed that palm kernel meal, included in 20% in the diet of old laying hens, increased rupture resistance (P <0.05) (week 110 and 120) and shell thickness (week 120), perhaps due to better intestinal health and calcium absorption. Ding et al. (2018) found that the greater proliferation of cecal lactic acid bacteria increased the incorporation of calcium in the medullary bone and in the egg shell.
Although palm kernel diets had the highest contributions of crude fiber and neutral detergent fiber with respect to control diet (table 1), this was not enough to cause an adverse effect on shell quality of these birds. According to Savón et al. (2007), high contents of fibrous compounds in the diets increase the gastrointestinal transit of digesta, which causes the restriction of the mobility of minerals, including calcium, which did not occur in this experiment with old chickens (100 to 120 weeks), taking into account the values of shell thickness and the resistance to egg rupture (table 3). Other studies showed that dietary use of high levels of palm kernels did not affect shell quality in laying hens (Chong et al. 2008 and Onunkwo 2018).
Table 4 shows that the inclusion of 20% palm kernel meal in diets of old laying hens (100 to 120 weeks) reduced the cost of the finished product by 18.14% compared to the conventional diet. Although hens increased food intake (table 2) with palm kernel meal, this experimental group reduced the cost of consumed food by 2.87% and the cost to produce an egg (0.01 USD).
Table 4 Effect of palm kernel meal on cost benefit relation of the egg of old laying hens (110 to 120 weeks)
| Items | Experimental diets | SE± | P value | |
|---|---|---|---|---|
| Control | Palm kernel meal | |||
| Cost of finished food, USD/t | 347.95 | 294.52 | ||
| Cost of consumed food/bird, USD | 5.02 | 4.88 | 0.014 | <0.001 |
| Cost to produce an egg, USD | 0.05 | 0.04 | 0.0001 | <0.001 |
This experiment showed that the inclusion of 20% palm kernel meal in the feeding of old hens, partially replacing corn and soybean meal, benefited the productive indicators (table 2) and egg quality (table 3) and , in turn, indicated a positive cost-benefit relationship associated to egg production and diet cost. In many Latin American countries, palm kernel meal is available all year round and with an affordable purchase price (USD 160/t) compared to corn meal (USD 330/t) and imported soybeans (USD 560/t). Therefore, this alternative ingredient is recommended in diets of laying hens to reduce production costs associated with their feeding, which can represent up to 70% of total production cost (Valdivié et al. 2020).
Dairo and Fasuyi (2008) reported that the inclusion of 25% of palm kernel meal in chicken feed reduced the cost of consumed feed by 7.27%. Likewise, Onunkwo et al. (2018) confirmed that increasing levels of palm kernel meal in laying birds reduced diet costs (8.47%) and the cost for egg production (1.03%). Shakila et al. (2012) indicated that the inclusion of 15% palm kernel meal, with and without enzymes, had the best cost-benefit relationship, associated to a lower diet cost.
Also, in other poultry categories, the use of palm kernel meal has shown tangible economic benefits. Botello et al. (2020), when using 20% of palm kernel meal in diets for broilers, found a decrease in diet cost of 6.08%. Furthermore, Ojewola et al. (2006) recorded a 6.91% reduction in diet cost, when they fed breeders with 25% of palm kernel meal.
These results show that the use of this alternative food promotes economic gains in poultry production, although it will depend on the purchase price of palm kernel meal in different regions, being more feasible in countries that produce African palm oil and palm kernel meal. Internationally, a cost of 0.04 USD to produce an egg is accepted as profitable (Valdivie et al. 2016), similar to what was evidenced in the group with palm kernel meal (table 4). The use of this feed ingredient could justify the keeping of laying hens up to 120 weeks old, with good productivity and economic profitability.
Conclusions
The results of this experiment showed that the inclusion of 20% of palm kernel meal for replacing corn and soybean meal in diets intended for old laying hens (100 to 120 weeks) increased egg production and feed intake and reduced mass conversion and dirty eggs. This ingredient improved yolk pigmentation and egg shell quality. In addition, it represented economic benefits for egg production.
