The quality of blood obtained from supplemented and challenged group especially on the haematology and blood chemistry assays indicated that the liver enzymes aspertate aminotransaminase (AST) and γ-glytamyltransaminase (γGT) were significantly elevated among supplemented and challenged group, an observation indicative of tissues damage [13
]. Creatinine kinase (CRK) was also observed to be elevated in supplemented group which also indicate some sort of muscle damage, CRK has value in distinguishing muscle from liver damage [19
], though, CRK is very insensitive and is a relatively poor diagnostic test in birds. However, Transaminases are the most commonly used indicators of cellular necrosis and increase in serum concentration may indicate liver malfunction [20
]. They occupy a central position in amino acid metabolism; the elevation observed in this study could have a consequential effect on the amino acid metabolism in the birds, it may indicate some sort of injury to the organs like liver, heart, kidney, and brain, such injury may cause leakage of enzymes from damaged organs to the blood stream, the concentration of these enzymes predict the severity of damage.
The significant low values of AST, γGT, AKP and Ab in the affected broilers indicate adverse health condition. The role of liver in the detoxification and regulating of body temperature cannot be over emphasized. AST, γGT and AKP are enzymes used in the assessment of liver functions. AST and ALT are been used to determine hepatocellular integrity, the lower value observed in AST activity in the NSC group may be an indication that viral challenge alone has no effect on hepatocellular integrity and for the same reason values of AKP and ϒGT observed in NSC group brings up the thought that NDV challenge has no adverse effect on the billiary system. TP, Albumin and globulin, AKP, γGT and AST level was observed to be high in SC group and when compared with those of the control groups is in agreement with the report of [21
], who stated that serum AKP could be influenced by physiological status (Pregnancy) and disease of animals. It has also been noted that lower AKP level could be linked to dietary zinc deficiencies [19
]. Similar trend was observed by Alletor and Futuga [22
] on the activities of AKP in blood of rats injected with legume anti nutrients. It appears that both viral challenged and Aloe vera
supplementation has a synergistic effect on the synthetic capability of the liver, similarly, the production of γGT, AKP and AST by the liver or other organs. A phenomenon in which both Albumin and enzymes are elevated in plasma may not be unconnected to the effect of the supplementation on the liver alone; it may also be due to other organs that produce AST, AKP and ϒGT such as the heart, bone marrow and pancreases. More so, The increase in AKP observed in SNC group as against the NSNC group shows that AV has a positive effect on the synthetic function of the liver while it has an adverse effect on the AKP producing tissues. The fact that it did not do the same to γGT and AST could be due to the fact that AV may have no adverse effect on the liver in the absence of NDV challenge.
Our finding suggest that oral intake of Aloe vera
modulated leucocytes proliferation of the supplemented broilers and enhanced the cell differentiation in favour of the lymphocyte as shown in the blood smear. An increasing practice among ornithologists is the use of blood smears to assess immune function of birds by counting the numbers and proportions of white blood cells (leukocytes) on blood smears, a leukocyte profile (or differential) can be obtained for the individual, giving insight into its immune function at the time of sampling [23
]. Our finding shows that there was a significant reduction in total leucocytes count among the challenged broiler chickens and the effect of which was more on supplemented birds, which indicate that the extracts administered to the individual broilers impacted their immunity by regulating the total leucocytes count. This finding is consistent with Davis et al., who showed that stressful events such as disease could induce a significant decrease in white blood cell count in peripheral blood of birds [23
]. Research with poultry has also shown that overall white blood cell numbers decrease within 1 h after stressful events [24
]. It is probable that the significant lower leukocyte count (leucopenia) of birds on A. vera
supplement is an indication that the birds were immunologically challenged. The reduced number of total WBC (leucocytosis) and increase in lymphocytes (lymphocytosis) in SC group is a characteristic of viral infection [25
]. The reduced leukocyte counts of birds could also be a physiological adjustment presented against negative antigenic effect associated with the viral challenge.
The total white blood cell recorded in the present study was slightly below the values reported by [26
] for broiler finishers fed control diets. Differential leucocytes counts were used as indicators of stress response and sensitive biomarkers crucial to immune functions [27
]. It has however been reported that bacterial and viral diseases affect the number of white corpuscles and the ratio between the different types of white corpuscles and the percentages of the various types in healthy animals vary slightly but are greatly modified in sick animals [28
]. Since corticosterone (stress hormone) level increase in wild birds within minutes of capture in response to stress [30
], the corticosterone hormone released in response to stress may indirectly act to reduce the number of leucocytes in the peripheral blood stream in exotic disease condition of NDV infection. However, further research into avian immune systems would be needful to verify this.
The H/L ratio has been increasingly used by ornithologists to monitor immune function, as it appears to increase with disease [23
], injury [31
], and urbanization [32
]. The relationship between increase in H/L ratio and lower immunoglobulin level is more difficult to interpret. It might be possible that birds with higher in H/L ratios are more responsive to the challenge because of circulating number of lymphocyte and their involvement in antibody production-an essential factor in humoral immunity, than those with lower H/L ratio, which ought to translate to healthier living by counteract the exotic effects of the challenge. The decrease in H/L ratio in the present study is at variance with the report of Davis et al. [23
]; this phenomenon may be peculiar to Newcastle disease virus infection.
The haemogram of test birds slightly varied with supplementation, it has been documented that diets affect blood profile of animal [33
]. The haemoglobin concentration (Hb) and packed cell volume (PCV) recorded in in this study was within the Hb (9.10 g/dl) and PCV (30.90%) of the control group of finisher broilers administered with oral Telferia occidentalis leaf extract as reported by Alabi et al. [26
] which indicate that AV extracts affected the haemotopioses of the birds.
Plasma cells in the blood films which ordinarily should be absent on peripheral blood smear but may be seen with bacteria or viral infections, drug and other allergic responses, immunization and systemic lupus erythromatosus and in patients with multiple myeloma. The finding of plasma cells on the blood smears of broiler chickens supplemented with AV of different concentrations and challenged with NDV suggest that there was active viral infection. Plasma cell production increases as activated B-cells differentiate [37
]. Surge in plasma cell production is followed by gradual decrease and sustained levels of circulating antibodies. For instance, plasma cells will likely secrete IgG3 antibodies, if they matured in the presence of the cytokine-interferon-γ. Since B cell maturation also involves somatic hypermutation (a process completed before differentiation into a plasma cell), these antibodies frequently have a very high affinity for their antigen. Plasma cells can only produce a single kind of antibody in a single class of immunoglobulin. In other words, every B cell is specific to a single antigen, but each cell can produce several thousand matching antibodies per second [38