Effect of restricted replacement of soybean meal with different levels of defatted apricot kernel meal on growth performance, carcass traits and blood constituents of broiler chickens

Introduction

Chicken production has improved dramatically over the last few decades, and this increase has affected practically every area of poultry production, including nutrition and genetic selections. Nutrition is important in poultry production because it has a direct impact on performance and production economics. Feed formulation is an application of nutrition in which nutritional knowledge is used to meet the nutritional needs of at least 60% of the total production expenses in bird production, (Oruseibio and Wariboko 2000) [35] . Thus, further improvements in the feed formulation process would maximize performance and profitability in poultry production, and one way to improve feed formulation is to reduce nutrient variability. Significant nutrient variability can result in under-feeding or over-feeding of essential nutrients, resulting in decreased bird performance, increased input costs, and increased environmental pollution. A possible strategy to optimize the feed formulation is to account for the essential and non-essential amino acid requirements in feed, particularly in low protein diets. Poultry meat and eggs contribute around 10% of all meat and eggs produced globally each year. Poultry, by providing meat and eggs, continues to be an important and inexpensive source of animal nutrition for many populations, including Egypt.; and the meat nutrients, quality depends largely on the composition of poultry feed. Energy sources are the most important and, in most cases, contains any harmful preservatives, which speeds up their growth that can easily be transferred from birds to humans, (Afolayan et al 2002) [3] . This recurring problem has pushed the research for options to reduce mycotoxins like zearalenone (ZEN), (Adeyemi 2005) [2] . Until recently, many published studies on bird feeding have concentrated on seed and feeder preferences, (Johnson et al 2014) [19] . Feed formulation can also be enhanced by precisely determining the maximum safe level of feed ingredients. Potential feed ingredients and novel cultivars may contain limiting characteristics (e.g. anti-nutritional factor, fibre, amino acid profiles, etc.) These chemicals are assessed in feeding trials that involve giving increasing quantities of the test ingredients and eventually assessing the response, such as growth, (Baurhoo et al 2011) [9] . Egypt was formerly known to be having an active boom in poultry production, but is now facing the difficulty of rising poultry production costs caused by high chicken feed costs, as well as fungal development and mycotoxin generation in poultry feeds during processing. Mycotoxins contamination of agricultural commodities and derivatives has sparked global concern due to the serious health risks they pose to humans, poultry, and livestock in general (Hussein and Brasel 2001) [17] . Domestic wastes are one among the major sources of the municipal solid wastes which are presently not exploited, but dumped at landfills which is provoking environmental threat. Thus, domestic waste or agricultural waste in general from food processing industries, markets, roadside vendors and even from our kitchens can be exploited for the production of fortified feeds, which can be used in feeding poultry birds, cattle, fishes, rabbits, pet animals and pigs as they are highly nutritious and cost effective than the conventional (commercial) feeds. They are also good sources of minerals such as Ca, P, Mn, K, Mg, and Zn. These can further be used in the pharmaceutical process industries for the production of drugs, as these processed by-products are also rich sources of dietary fibre, which has several benefits of health. Apricot (Prunus armeniaca L.), because it is a good source of nutrients, is one of the most familiar crops worldwide (Baytop, 1999) [10] . The kernel is also reported to have high antioxidant and antimicrobial activities (Yigit et al., 2009) [44] . The protein content of apricot kernels ranges from 14.1 to 45.3% (Alpaslan and Hayta, 2006) [4] . A study found that apricot kernel proteins contain 84.7% albumin, 7.65% globulin, 1.17% prolamin, and 3.54% glutelin, (Abd-El-Aal et al., 1986) [1] . Nutritive value of proteins Essential amino acids in apricot kernel constitute 32-34% of the total amino acids (Femenia et al., 1995) [15] . The major essential amino acids (mmol/100 g meal) are arginine (21.7-30.5) and leucine (16.2-21.6), and the predominant nonessential amino acid is glutamic (49.9-68.0) (Kamel and Kakuda, 1992) [21] . The kernels contain thiamine, riboflavin, niacin, vitamin C, atocopherol, and d-tocopherol (Slover et al., 1983) [41] . The mineral content ranges of apricot kernel (mg/100 g dry matter) are as follows: Na, 35.2-36.8; K, 473-570; Ca, 1.8-2.4; Mg, 113-290; Fe, 2.14-2.82; and Zn, 2. 33-3. 15 (Alpaslan and Hayta, 2006) [4] . Amygdalin (known as laetrile or vitamin B17) is commonly found in the kernels of almonds, apricots, cherries, peaches, and apples. The amount of cyanogenic glycosides in plants varies with plant species and environmental effects. Amygdalin contains a cyanide group between a glycoside and a benzene ring that can be released after hydrolysis (Cho et al., 2006) [12] . The amygdalin content of apricot and bitter almond kernels (Prunus armeniaca L.) has been reported to be approximately 3 or 4% by weight (Niels, 1996) [29] . Apricot kernels contain approximately 20-80 mmol/g of amygdalin, and it is very high (5.5 g/100 g) in bitter apricot cultivars and not detected in sweeter ones. On average, an apricot kernel contains approximately 0.5 mg of cyanide (Femenia et al., 1995) [15] . Hydrolysis of cyanide can be catalyzed by either endogenous enzymes contained within the kernels or exogenous b-glucosidase released from bacteria within the gastrointestinal tract or from ingested foods inside the intestine. Cyanogenic glycosides are nontoxic but can release free hydrogen cyanide (Cho et al., 2006) [12] . The hydrogen cyanide content is 8.9 -11.7 mg/100 g in bitter cultivars and 200 mg/100 g in the wild cultivars (Baytop, 1999) [10] . Therefore, the objective of the current study to determine the effect of using different levels of DAKM, as a partial replacement for SBM in commercial broiler diets, on performance, digestibility, carcass traits and blood metabolites of Cobb-400 broilers.

Materials and Methods

Preparation of defatted apricot kernel meal

Firstly seeds by-product was collected from Faragla Manufacture, New Borg El-Arab Alexandria -Egypt. Seeds were removed from the fruits and the seeds, the outer shell was washed with water to remove the remaining fruit pulp and sun-dried for 3 weeks, then the outer shell of the seeds was cracked manually and the apricot kernels were cooked to approximately 60 °C. The kernel is then squeezed to remove any liquids, then toasted and subsequently cooled. Then the kernel meal was stored in bags until added to poultry feed. The experimental work was carried out in Borg El Arab station, Animal Production Research Institute, and Agricultural Research Cent from January to March 2022. A total of 300 unsexed one-day-old Cobb-400 (45.8±0.39) chicks were randomly distributed into four dietary treatments replicated five times in such a way that each had 15 birds. Treatments included 0, 25, 35, and 45% SBM were replaced with deffated apricot kernel meal (DAKM) in starter (1-21 days) and grower (22-42 days) diets fed to chicks for 42 days. The composition of experimental diets is shown in Table 1. Experimental diets were formulated according to NRC guidelines NRC (1994) [31] and the proximate analyses of the starter and grower diets were calculated as shown in Table 2. The total chick's weight of each pen was established to be equal and the feeder was separately allocated at each pen. Feed and water were provided ad-libitum. All birds were kept under the same management, hygienic and environmental conditions. The chicks were vaccinated against the common broiler diseases, according to the conventional program used for broilers. Live body weight and feed consumption were recorded at weekly intervals throughout the experimental period. Daily weight gain, feed conversion ratio and economic efficiency were calculated. Economic Efficiency (EE) and Relative Economic Efficiency (REE) were calculated according to input-output analysis data. Besides Performance Index (PI) was calculated according to North (1981) [30] . A digestibility trial was undertaken at the end week of the experimental period (6 weeks of age), 10 chicks were randomly selected from each group; birds were housed individually in metabolism cages. The experimental diets were offered daily and fresh water was provided all the time. Feed consumption was accurately determined. Faeces were collected for 5 days a collection period, then the faeces was dried at 60 °C for 24 h. All collected faeces for each bird were mixed, and then representative faeces samples were ground for chemical analysis. Chemical analysis of different diets and faeces was determined according to AOAC (2012) [6] .

On day 42, two chicks were randomly selected from each pen, fasted for 16 h before slaughtering, weighed and manually slaughtered. Carcass weight (Dressing, breast, thigh, abdominal fat, liver, heart, empty gizzard and other total edible parts) were calculated as a percentage of live body weight. Chemical analysis of meat was done according to AOAC (2012) [6] and the values were expressed on a DM basis. Blood samples were collected from sacrificed birds in clean, sterile tubes and then were immediately centrifuged at 3000 rpm for 15 min and stored at -20°C until use. Total Protein (TP), albumin (ALB), globulin (GLB) (TP-ALB), urea, cholesterol, HDL, LDL, vLDL and triglyceride concentrations were determined by spectrophotometer (Spectronic 21 DUSA) using commercial diagnostic kits (Combination, Pasteur Lap.). Statistical analysis Data on feed intake, live body weight, feed conversion, nutrient digestibility, carcass data, and blood constituents were subjected to one-way analysis of variance using SPSS (2008) [42] . Duncan's multiple range test (Duncan 1955) [14] was used to separate means when the dietary treatment effect was significant, according to the following model:

Results and Discussion

Growth performance

Performance evaluation of the birds fed varying levels of DAKM substitute instead of SBM at different ages are presented in Table 3 indicating that LBW of (DAKM-25) fed groups were inferior to (DAKM-35 and DAKM-45) fed ones when measured at week 3 and 6 of age, but insignificant differences were observed between (DAKM0) and (DAKM-25) at week 3 of age. It is noted that when SBM was partially replaced with DAKM at 35 and 45% levels, LBW significantly decreased at weeks 3 and 6 of age. A similar trend of BWG of chicks fed graded levels of DAKM had highly significant (p=0.001) differences in the entire experimental period. As DAKM level increased 35 and 45% substituted instead of SBM, BWG significantly decreased by 1-3, 3-6 and 1-6 weeks. While BWG of broilers in (DAKM-25) group was better than those in the (DAKM0) group by 2.66, 4.50 and 3.74% in 1-3, 3-6 and 1-6 weeks, respectively. Feed intake (DAKM0) and (DAKM-25) groups were increased (p=0.05) than those (DAKM-35) and (DAKM-45) groups in starter, grower and the entire experimental period. It is observed that when the DAKM level increased, the amounts of feed intake significantly decreased (p=0.0001). The feed conversion ratio was better (p=0.005) in (DAKM-25) group followed by the (DAKM0) group than that of the (DAKM-35 and DAKM-45) groups, both in the growth period and in the entire experimental periods (p=0.001). These results are similar to the findings of Boubekeur et al. (2021) [11] who reported that the addition of 30% apricot kernel cake by-products for quail diets did not have adverse effects on the growth performance. Also, Omer et al. (2020) [34] and Mennani et al (2017) [28] found no adverse effects of apricot seed kernel or apricot kernel meal on growing rabbit's performance even at levels as high as 4.5% or 30%, respectively. The lower LBW in (DAKM-35) and (DAKM-45) groups during the experimental periods were since the Apricot kernel contained cyanogenic glycosides. Arbouche et al. (2012) [7] demonstrated that apricot kernel from the Rosaceae family, containing cyanogenic glycosides, impairs the broiler performance. Cyanogenic glycosides are converted to hydrogen cyanide in the intestinal epithelium and deteriorate growth performance and nutrient digestibility in broiler chickens (Rodríguez et al., 2001; Senica et al., 2016) [38, 40] . However, LBW of broilers fed on a diet containing 25% DAKM was better than those fed a basal diet by 2.35 and 3.61% respectively, at weeks 3 and 6 of age. The comparable results between the (DAKM-0) and (DAKM-25) groups reflect the ability of these chicks to adequately handle and tolerate anti-nutritional factors at this level. Kalia et al (2017) [20] and Dragovic-Uzelac et al (2007) [13] reported that an increase in body weight back to the presence of bioactive molecules (carotenoids, catechins, neochlorogenic acid, caffeic acid) in P. armeniaca extract chicken diet which can stimulate increased digestion and metabolism of nutrients causing higher efficiency in the utilization of feed which results in enhanced growth in chickens. Kalia et al (2017) [20] mention to that addition Prunus armeniaca seed extract at different levels (100, 150, 200, 300, 400, and 800 mg/kg body weight) of chicken in drinking water resulted an increased (P = 0.036) in body weight as compared with the control group. Chicks fed 25% DAKM had the best FCR values during the periods 1-3, 3-6 and 1-6 weeks of age by about 1.10, 1.67 and 1.44 compared with a control group which recorded 1.13, 1.82 and 1.54, respectively, at the same periods. However, chicks fed (DAKM-35) and (DAKM-45) groups had the worst values of FCR compared to the control group. Whereas, Kalia et al. (2017) [20] concluded that adding Prunus armeniaca seed extract at different levels (100, 150, 200, 300, 400, and 800 mg/kg body weight) of chicken in drinking water enhanced feed conversion ratio (FCR) values at 300 and 400 mg/kg body weight significantly (P = 0.024). A high level of DAKM 35 and 45%, which replaced instead of SBM in the diet had a high concentration of tannins which depress digestion and the feed intake. This may explain the poor chicks' performance in (DAKM-35) and (DAKM-45) fed groups. Apricot kernel contains anti-nutritional components: linatin, cyanogenic glycosides, phytones, trypsin inhibitors, lignans, and saponins (Hamid and Kumar, 2017; Westbrook and Cherian 2019) [16,43] . These factors can limit the potential of these seeds to be used in poultry production to a certain extent. Such doubts were raised by Ryhänen et al. (2007) [39] and Pekel et al. (2009) [37] . They reported a negative effect of oilseeds in poultry diets on production effects, especially when used in high doses. They noted impaired feed conversion and decreased feed intake during the starter period. However, saponins can reduce intestinal motility (Klita et al., 1996) [23] , inhibit gastric emptying (Yoshikawa et al., 2001) [45] and decrease the growth rate (Makkar and Becker, 1996) [26] . They also lower digestion rate (Killeen et al., 1998) [22] , depress mucosal enzyme activity in the lower intestine (Olli et al., 1994) [33] and inhibit the absorption of vitamins A and E in chicks (Jenkins and Atwal, 1994) [18] .

Economic Efficiency

The final body weight, length of the growing period and feeding cost are generally among the most important factors involved in the achievement of maximum efficiency values of meat production. The EE of the different formulated diets as affected by different treatments is shown in Table 4. [27] who found that economic efficiency values were increased when SBM was partially replaced with food industry byproducts and wastes by about 20 g kgG 1 in pre-starter, 50 g kgG 1 in starter and finisher in the diets. Also, The utilization or incorporation of at least 20% domestic waste in poultry feed can help reduce the cost of livestock production as well as the burden and dangers posed by the disposal and poor management of domestic waste in the environment, while also reducing the act of artificial growth substances added to commercial poultry feed.

Nutrient digestibility

Data of digestion coefficients are presented in Table 5. Broilers in the (DAKM-25) group recorded the highest CP digestibility (p=0.0001), but the (DAKM-0) and (DAKM-25) groups recorded the lowest EE digestibility (P=0.05) compared to the other groups. Apparent OM, CF and NFE digestibility showed no significant difference between (DAKM-0) and (DAKM-25) groups, while OM, CF and NFE in (DAKM-0) and (DAKM-25) groups surpassed those (DAKM-35) and (DAKM-45) groups. a, , b, c andd: Means in the same row with different superscript are significantly different (P<0.05), OM: Organic matter, CP: Crude protein, EE: Ether extract, CF: Crude fiber, NFE: Nitrogen free extract The improvement of digestibility percentages for most nutrients is associated with the increase of BW and BWG results (Table 3) and the improvement of feed utilization which improves the FCR (Table 3) for the broilers fed on (DAKM-25). Omer et al (2020) [34] demonstrated that the addition of different levels (0.75, 1.5, 3, and 4.5) of apricot seed kernel (ASK) in a rabbit's diet did not significantly affect nutrient digestibility and nutritive values except for EE, which was realised when ASK 3 percent, with the corresponding value of EE digestibility of (81.54 percent). Apricot kernel meal contain other anti-nutritional substances, such as cyanogenic glycosides, which can exert a negative effect on nutrient digestion, (Konieczka et al 2017 and Amerah et al 2015) [24,5] . Saponins have long been known to inhibit the absorption and utilization of minerals by animals. Saponins decrease protein quality by reducing digestibility and palatability (Ogunbode et al., 2014) [32] . Saponins were recognized as antinutrient constituents, due to their adverse effects such as growth impairment and reduced food intake due to the bitterness and throat-irritating activity of saponins. In addition, saponins were found to reduce the bioavailability of nutrients and decrease enzyme activity and it affects protein digestibility by inhibiting various digestive enzymes such as trypsin and chymotrypsin (Liener, 1974) [25] .

Carcass traits

Carcass traits of birds for different groups are shown in Table 6. Generally, the group fed on (DAKM 0) showed significantly (p=0.05) the highest dressing, breast and thigh percentages followed by (DAKM-25) while (DAKM-45) had the lowest percentages. Dressing, breast and thigh percentages were significant (p=0.05, 0.001 and 0.001) increased for the broiler fed on (DAKM-25) as compared to those fed on (DAKM-35 and DAKM-45), respectively. While the percentage weight of the heart was nearly similar for the different groups. However, DAKM led to a significant (p=0.004 and 0.005) increase in liver and abdominal fat percentage weight as presented in (DAKM-35) and (DAKM-45), respectively. [11] who reported that the use of high levels of apricot kernel cake in quail feeding resulted the highest (74.4%, p=0.02) with an optimum meat protein level (30.6%, p=0.024) and the lowest fat content (2.26%, p=0.001) in carcass yield compared with the control group. Apricot seed kernel at different levels (0.75, 1.5, 3 and 4.5) had no effect on both digestive tract and head weights of rabbits, while giblets and carcass weights were increased (P<0.05) compared to the control rabbits-diet, (Omer et al 2020) [34] . Whereas, Arbouche et al (2021) [8] found that the incorporation of detoxified apricot kernel meal (DAKM) in substitution of soybean meal for up to 60% in a rabbit diet has not affected slaughter parameters or carcass characteristics (p>0.05). On the other hand, replacing SBM with graded levels of DAKM 25, 35 and 45%, significantly (P<0.05) decreased relative thigh and gizzard weights compared to the control diet. Liver relative weight was significantly increased in those groups fed on (DAKM-35 and DAKM-45). There were significant differences (p=0.05 and 0.02) in the contents of moisture, protein, ether extract and ash among the different groups, respectively. Results indicated that replacing SBM with 25% DAKM in the diet significantly (p=0.01, 0.002 and 0.05) decreased moisture, ether extract and ash contents in the breast and thigh meat compared to those fed on control and 35 and 45% DAKM, respectively. Ether extract and ash contents of meat were significantly (p=0.05) increased as increasing the levels of DAKM in the diet. The high protein content in the breast and thigh meat was recorded for broilers fed on DAKM 0 and 25% DAKM, however, groups fed on 35 and 45% DAKM had the lowest protein content. Omer et al (2020) [34] found that rabbits-diet contained apricot seed kernel (ASK) with level 0.75, 1.5, and 3% were significantly (P<0.05) increased crude protein content of best 9 th , 10 th , and 11 th ribs. Meanwhile, ASK-diet (0.75, 1.5, and 3%) significantly (P<0.05) decreased ether extract content of best 9 th , 10 th , and 11 th ribs.

Blood parameters

The concentrations of total protein, albumin and globulin in blood serum decreased significantly (p=0.05, 0.005 and 0.002), respectively, while serum urea concentration, non significantly (p=0.091) affected with DAKM diets for the different groups (Table 7). However, serum triglycerides, LDL and vLDL concentrations decreased significantly (p=0.001, 0.003 and 0.006) for the group fed on (DAKM) followed by the group fed on (DAKM-25), while (DAKM-45) had the lowest concentrations. Of blood parameters, cholesterol was not significantly affected by experimental treatments. Kalia et al. (2017) [20] revealed that plasma cholesterol and Plasma triglyceride were considerably lower (P<0.05) in chicken drinking water using 200 mg of Prunus armeniaca seed extract when compared with the control group. Apricot seed kernel in rabbits diets had no significant effect on total protein, albumin, ALT, total cholesterol, triglycerides, urea, and creatinine. Meanwhile, rabbits received a diet containing 4.5% Apricot seed kernel significant (P<0.05) increased total globulins and AST contents, (Omer et al 2020) [34] . Blood serum proteins are a significant indicator of the health condition and production features of the organism because of their numerous roles in physiology. Among the numerous factors that influence the concentration of serum proteins, feeding plays an important role in physiology. However, replacing soybean meal with graded levels of DAKM 35 and 45%, significantly (p=0.05, 0.005 and 0.002) decreased the blood serum total protein, albumin and globulin with high per cent replacement of SBM compared with the control diet and DAKM-25, respectively. The described changes are related to the most important physiological role of blood proteins; e.g., as a source of amino acids for the synthesis of tissue proteins. As well as, Prunus armeniaca seed extract increased (P<0.05) the level of plasma total protein, albumin, and globulin in the broiler -diet as compared to control group, (Kalia et al 2017) [20] .

Conclusion

The addition of the defatted apricot kernel meal as a partial replacement for soybean meal as a protein source in poultry diets may be a useful economic strategy for decreasing feed costs. The results of this study suggest that defatted apricot kernel meal can be fed to chicks at levels up to 25% replacement of the soybean meal without negative effects on growth performance, economic efficiency, carcass traits and blood parameters.

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