4.1. Broiler meat quality characteristics and Proximate analysis
Color is one of the main indicators of the quality of most feeds (Smith et al., 2002). The L* value is the main parameter that determines poultry meat color. It is an important meat quality trait as it affects consumer acceptability of meat (Adeyemi et al., 2016). The meat color in the current experiment is within the normal range (46 < L* < 53) of breast and thigh meat color reported by Zhang and Barbut (2005). However, Abdulla et al. (2017) reported higher L (lightness), a (redness) and b (yellowness) values of breast muscles from Cobb 500 chickens supplemented with probiotic containing Bacillus subtilis during the rearing period, compared to control birds. The possible reason for the high b* yellowness color in the current experiment for TP and EM-TP could be due to the presence of bio-active compounds in turmeric feed additive, which could alter muscle pigmentation (Ruby, 1995). Additionally, the study of Faria et al. (2009) indicated that the ingestion of a larger amount of feed rich in carotenoids by growing chickens provides a greater intensity of yellow color in the meat, resulting in a higher b* value. A similar study result by Kanani et al. (2017) indicated that turmeric and cinnamon powders elevated the water-holding capacity and pH.
The similar pH values among the treatments in the current study, indicates that they were closer to neutral, resulting in similar lightness (L*) and redness (a*) values for all treatment groups. This could be because experimental birds did not experience transportation stress and were subjected to the same pre-slaughter management circumstances as commercial broiler production (Souza et al., 2011). These factors may have contributed to the pH levels being similar among the treatments in this study.
Effective microorganisms, TP, and their combination did not affect mean breast and thigh cooing loss. Cooking loss is a measurement of how much water is lost during cooking due to shrinkage. The pH and lipid content of the tested muscle can affect cooking loss readings (Souza, 2004). The finding indicates that additives used in the current experiment can be used since they do not have any effect on cooking loss.
Warner-Bratzler Shear Force (WBSF) is one of the most commonly used instruments in estimating meat tenderness and texture quality of poultry meat, whereby the higher WBSF values are associated with less tender poultry meat (Zhuang et al., 2008). Therefore, the less tender meat for both breast and thigh meat observed in the CTL group agrees with the results observed by Zhang et al. (2005), who investigated the effects of Saccharomyces cerevisiae cell components on meat quality of male broilers. The shear forces determined in cooked breast and thigh muscle in experimental groups was lower as compared with the control in the current experiment. Contrary to the current result Peter et al. (2015) indicated that higher shear force value of breast and thigh muscle was observed in probiotic supplemented than the other group. This difference might be due to the effectiveness of a probiotic application which may depend on many factors (Patterson and Burkholder, 2003), such as species composition and viability, administration level, application method, frequency of application, overall diet, bird age, overall farm hygiene, and environmental stress factors (Zhou et al., 2010).
The lower crude fat percentage of the thigh and breast meat in those fed additives in the current study agreed with the finding of Pietras (2001) who reported that crude fat and total cholesterol content tended to decrease in the meat of chickens given probiotics (Lactobacillus acidophilus and Streptococcus faecium). Addition of turmeric at a rate of 3 g/kg feed reduced the meat fat content and increased the carcass quality of broilers (Al-Sultan, 2003, Samarasinghe et al. 2003, Emadi and Kermanshahi, 2006). The probable reason for fat and cholesterol content reduction could be due to the presence of polyunsaturated fatty acids and the antioxidant content of turmeric.
4.2. Sensory evaluation of broilers breast meat
The results of sensory evaluation in the current experiment revealed that feeding of effective microorganisms and turmeric did not affect color, flavor, or smell in chicken meat which is in agreement with the study of AL-Sultan (2003) who reported that turmeric did not induce any abnormal flavor, color, or smell in broilers breast meat. According to Liu et al. (2012), probiotic supplementation to a chick’s diet resulted in a higher degree of satisfaction in flavor pleasantness scores for the consumer compared with the control.
4.3. Effect of effective microorganisms and turmeric feed additives on hematological and biochemical indices
Hematological and serum biochemical parameters are useful indicators of the physiological responses of animals to the diet they are consuming (Madubuike and Ekenyem, 2006). In the current study, EM, TP and EM-TP supplementation had a similar effect on blood hematological traits, which were found to be within the normal ranges (RBC: 2.5–3.5 x106 µl, PCV: 22–35%, Hb: 7–13 g/dl, WBC: 12–30 x 103µl, MCV: 90–140 fL, MCH: 33–47 pg/cell and MCHC: 26–35 g/dl) for healthy broiler chickens (Wakenel, 2010). Moreover, Ibrahim (2012) reported that probiotic supplementation did not affect blood hematological traits. The current findings are consistent with those of Emadi et al. (2007), who found that adding turmeric to broiler hematocrit levels at days had no significant effect.
Antioxidant activity and blood biochemistry parameters are essential indicators of health and nutrient metabolism in an organism's body (Lokesh et al., 2012). All the serum biochemical parameters were within the normal range (AST = 70–220 U/L, ALP = 568–8831 U/L, ALT = 19–50 U/L, Total protein = 2.5–4.5 g/dl, Uric acid = 1.9–12.5 mg/dl, Total Cholesterol = 87–192 mg/dl, Triglycerides = 45.7–172 mg/dl, Albumin = 1.17–2.74 g/dl, Glucose = 200–500 mg/dl, LDL = 80–120 mg/dl, HDL = 35–86 mg/dl, Globulin = 0.5–1.8 g/dl, Creatinine = 0.55–0.95 mg/dl) (Clinical diagnostic division, 1990; Meluzzi et al., 1992; Lumeij, 1997; Thrall, 2007) in the current experiment. The finding in the current study agrees with those of Yazhini et al. (2018), Siadati et al. (2017), and Iqramu et al. (2017), who reported that supplementing poultry with probiotics reduced serum total cholesterol levels. Following probiotic administration to broilers, the reduction of cholesterol and fat content in the breast and thigh meat was observed (Hossain et al., 2012). Lactic acid bacteria are also a probiotic which reduces the cholesterol level by assimilating endogenous or exogenous originated cholesterol in the intestinal tract (Gilliland,1989), reducing or inhibiting the expression levels of Niemann-Pick C1-like 1a protein, expressed on the surface of enterocytes, which reduces the cholesterol absorption (Huang and Zheng 2010). On the other hand, Shirisha et al. (2017) observed no significant difference in total cholesterol levels between probiotic-supplemented and control birds.
The lower low-density lipoprotein concentration in the treatments with additives in the current experiment concur with the findings of Kalavathy et al. (2010) who reported that probiotic supplementation decreased serum low-density lipoprotein level and but had no significant effect on serum high density lipoprotein level in broiler chickens. Consistent with the current finding Ashayerizadeh et al. (2011) reported that supplementation of probiotics did not affect serum high-density lipoprotein concentration. Supplementation of probiotic bacteria to broiler chicken altered the lipoprotein metabolism of birds favorably with a more pronounced reduction in the total cholesterol and low density lipoprotein cholesterol concentration. Moreover, Kermanshahi and Rasi (2006) reported that turmeric rhizome at 0.05–0.2% levels decreased low-density lipoprotein in layer breed. Probably the reason that the lower result of low density lipoprotien in TP treatment could be due to turmeric effect in the regulation of alkaline phosphatase (Upadrasta and Madempudi, 2016; Khalesi, 2014) and lactate dehydrogenase in the broiler chickens’ blood (Kermanshahi and Rasi, 2006). Hosseini-Vashan et al. (2012) reported significant reductions in the activities of alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase enzymes in broiler chickens fed 0.4% and 0.8% turmeric powder under heat stress. In contrast to the current study, Kumari et al. (2007) and Mehala & Moorthy (2008) reported that the activity of some liver enzymes, such as alkaline phosphatase and low density lipoprotien, and glucose concentrations did not change with the dietary inclusion of turmeric powder in all the treated broiler chicken groups. The variation with the current study might be due to the dose effect of turmeric.
Regarding the concentration of triglycerides, the present study agrees with the findings of Al-Saad et al. (2014), Kalavathy et al. (2010), Ashayerizadeh et al. (2014), Abeer et al. (2015) and Iqramu et al. (2017), who reported a significant decrease in serum triglycerides level in broiler chickens fed probiotic as an additive. Similarly, the finding of Nouzarian et al. (2011) reported that triglyceride concentration of the serum was markedly reduced by turmeric powder inclusion in the diet in comparison with the control diet. This phenomenon may be due to the lowering hepatic lipogenesis effect of turmeric powder, because triglycerides are produced in the liver by hepatic lipogenesis and are secreted into the plasma (Lanza-Jacoby, 1986; Herzberg and Rogerson, 1988).
4.4. Antibacterial effects of effective microorganism and turmeric
Reduction in the total coliform count and E. coli bacteria indicated that there was variation among the treatment which is supported by the idea of EMROSA (2006) which revealed that EM is self-sterilizing (pH between 3.4 to 3.7); therefore, pathogens cannot survive in EM. The volatile fatty acids produced by probiotic bacteria are lipophilic penetrating the bacterial cell wall and producing H+ ions, which in turn destroy the internal physiology of the bacterial cell (Kuruti et al., 2017). It can be concluded that the use of probiotics as an additive affects the balance of caecal volatile fatty acids, which in turn exert an antimicrobial effect in poultry. Similarly, the finding of Deniz et al. (2011) indicated that dietary probiotic supplementation has markedly raised the bacillus population in the caecum while the enterococci and coliform populations were significantly reduced compared to the non-supplemented control. Fuller (1977) also, found that host-specific Lactobacillus strains were able to decrease E. coli in the crop and small intestine.
The study of Fitoni et al. (2013) indicated that turmeric with a curcumin active compound could inhibit the growth of coliform bacteria with a total of 108 cfu colonies compared with treatment without turmeric that contained more than 300 cfu of coliform bacteria. The curcumin antibacterial mechanism was that these particles entered the bacteria cell walls by completely damaging the cell walls so that it resulting in cell death (Bhawana et al., 2011).