Effect of vaccination on some biochemical parameters in broiler chickens

The present study was conducted to evaluate the effect of vaccination against Newcastle disease, infectious bronchitis and infectious bursal disease on some biochemical parameters in serum of broiler chickens. Two hundred and fifty Ross 1-day old unsexed broiler chicks were divided into two groups (unvaccinated and vaccinated), blood samples were obtained from each group weekly until 8 weeks old. The results revealed significant differences in values of some biochemical parameters according to various ages of chickens within either unvaccinated or vaccinated groups, the effect of different ages on parameters was more clearly observed in vaccinated group. It was also revealed from this study that vaccination had no effect on levels of glucose, total protein, total lipids cholesterol, triglycerides, high density lipoprotein-cholesterol (HDL-c) and low density lipoprotein-cholesterol (LDL-c) and the activity of alanine aminotransferase (ALT). Vaccinated chickens showed a significant reduction in the level of albumin, albumin/globulin ratio and alkaline phosphatase (ALP) activity accompanied with an elevation in the level of globulin and activities of aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) compared with their values in non vaccinated chickens. These data suggest the interference of age and vaccination in broiler chickens on some biochemical parameters.


Introduction
The primary purpose of all poultry vaccination is to induce protective immune response that could prevent or reduce the economic lost caused by viral infection and diseases (1). Serum biochemical parameters may provide valuable information for evaluation of health status of birds and reflect many metabolic alterations of organs and tissues (2). Several factors may have an influence on biochemical parameters in the chicken's serum including feed additives (3), drugs(4), environmental temperature (5) and poultry diseases (6). Newcastle disease (ND), infectious bronchitis (IB) and infectious bursal disease (IBD) remains the major viral poultry diseases affecting domestic and wild birds with high mortality rate induction (7,8), a little attention has been given to the role of vaccination on biochemical changes in the serum of chickens. A significant changes in the serum levels of total protein, triglycerides and albumin following vaccination was recently reported (9).
Our trial was conducted to evaluate the effect of vaccination against ND, IB and IBD on some serum biochemical parameters in broiler chickens including changes in the activities of several enzymes as alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) in addition to the levels of glucose, total lipids, cholesterol, triglycerides, HDL-c, LDL-c, VLDL-c, total proteins, albumin and globulin.

Chickens
A total of 250 ROSS 1-day -old broiler chicks were randomly divided into two groups (control and vaccinated). These chicks were reared in cages and housed in a separate rooms of the animal house research division in the College of Veterinary Medicine, University of Mosul. The birds were allowed ad libitum access to food and water and maintained with recommended ambient temperature and other environmental conditions to 8 weeks of age.

Vaccine and vaccination
The chickens of the second group were vaccinated according to Jordan et al (10), vaccination program was designed as day 1 with spray IB vaccine (H120), day 7 with drinking IBD vaccine (Gumbol), day 10 with drinking ND vaccine (B1), day 13 with drinking IBD vaccine (IBDL), day 15 with drinking IB vaccine (H120), day 22 with drinking ND vaccine (B1), day 35 with spray ND vaccine (Lasota).

Blood sampling and serum collection
On day 7 and at weekly intervals until 56 day old, labeled blood samples (number of birds and date) were taken from jugular vein using 1 ml syringes, kept in room temperature until clotted, and were centrifuged at 1,000 g for 15 minutes, Serum specimens obtained were frozen and stored at -20 C° until the time of analysis.

Estimation of biochemical parameters
Serum LDH, total cholesterol and triglycerides levels were estimated by the colorimetric method using diagnostic kit (Biolabo, France). AST and ALP activities and albumin level were measured by the colorimetric kit (Biomerieux, France). ALT activity was measured using colorimetric kit (Spinorect, spain). Glucose level was measured using colorimetric kit (Biocan, Diagnostic, Gmbh, Burbach, Germany).
HDL-c concentration was estimated colorimetrically using diagnostic kit (Biomaghreb, Tunisia). Total protein and total lipids levels were measured according to (11) and (12), respectively.

Statistical analysis
Data were expressed as mean ± SE, the data were analysed by (ANOVA). Significant treatment differences were assessed using Duncan's multiple range test. Differences in the means between the two groups were examined with students' t test. P<0.05 was considered as statistically significant (13).

Results
The results obtained (Table 1) revealed that the activities of AST, ALT and LDH were increased at the fifth week old in vaccinated chickens. A significant increase in AST activity at seventh week old was only seen in non vaccinated chickens. Activity of ALP in the serum tend to be deceased with age from the third week in both vaccinated and non vaccinated chickens (Table 1). Vaccination produced an elevation of LDH and a reduction of ALP activities from the first week till the end of the experiment, while activity of AST in vaccinated group was increased at fifth week in vaccinated group compared with value obtained from non vaccinated group. Table (2) revealed that the total cholesterol was increased at the eighth week old only in vaccinated chickens. Serum levels of triglycerides was decreased at the sixth and eighth week old in both vaccinated and non vaccinated chickens, respectively. This table also showed an increase in serum level of glucose at the eighth week old in both vaccinated and non vaccinated chickens. Comparison of levels of cholesterol, total lipids, triglycerides and glucose for vaccinated chickens with their levels of corresponding parameters for non vaccinated chickens were not significantly differed. Results of Table (3) showed that values of HDL-c, LDL-c and VLDL-c were not affected by age and vaccination. From Table (4) it was observed that levels of total protein and albumin in the serum tend to be increased gradually by age from the second week in both vaccinated and non vaccinated chickens. An elevation in the level of globulin accompanied with a significant reduction in the level of albumin and albumin/globulin ratio were observed in vaccinated chickens in comparison with their levels in the non vaccinated chickens (Table 4).   Values are expressed as mean±SE, Different letters in the same column refers to the significant differences at level P≤0.05, *Significant differences from non vaccinated data at P<0.05.

Discussion
A little work only had been done for influence of vaccination on blood analysis and utilization of biochemical profile in avian medicine.
Data obtained from this study revealed that serum ALP activity in non vaccinated and vaccinated chickens was extremely high in the first week then decreased gradually by age. These findings come in agreement with those reported by (14).These changes correspond with the growth and may be attributed to differences in bone formation or to physical role in general metabolic activity (15). The main cause for serum ALP reduction is damage of intestine (16). The predominant ALP isoenzyme in plasma originates in the gut (17). Appearance of abnormal amounts of certain enzymes of intercellular origin in the blood reflect damage to an organ or tissue (18). Liver is rich in some enzymes as ALT, AST and LDH and it's damage often results in releasing these enzymes to the blood (19). In the present study, serum ALT activity was not affected by age in both vaccinated and non vaccinated chickens. Vaccination also showed no significant change in serum ALT activity. This observation was in contrast to previous study (14) who demonstrated that the activity of serum ALT was higher in vaccinated chickens at the first two weeks of age. Vaccination was accompanied with a rise in the AST activity. This result was in agreement with the finding of (14) who found that serum AST activity was increased following vaccination with ND vaccine, this indicated some damage to an organ or tissue, or may be due to heart infarction and acute kidney disease (20). Serum LDH activity was unchanged in chickens of non vaccinated group by age. This observation was in contrast to previous study (21) who indicated that serum LDH activity in chickens was decreased by age. The elevation of serum LDH activity postvaccination seems to be agree with that reported by (14) who demonstrated that this finding may be due to damage effect of the vaccine on tissues or organs which lead to the rise in it's level in the serum. This increasing may be also result from brain and nervous system damage resulting in paralysis and muscular atrophy and consequence metabolic changes (22). According to the age husbandry periods the elevation of both cholesterol and glucose levels and the reduction in level of triglycerides at the eighth week of age was in agreement with previous reports (23)(24)(25).Vaccination in the present work did not cause any significant changes in the levels of total lipids, cholesterol and glucose. These findings come in agreement with those reported by (26) for total lipids and (25) for cholesterol and (9) for glucose. Unchange in the level of cholesterol in the vaccinated chickens of the present work may reflect the intact liver function as it was postulated from the unalteration in the activity of ALT in the present study. Unchange in level of triglycerides was not confirmed by other study (9) who found a significant increase in serum triglycerides in chickens postvaccination. Levels of both glucose and triglycerides may be correlated. It has been found that elevation of glucose concentration could induce 50% reduction in oxidation of fatty acids and this followed by an increase in serum level of triglycerides (27). Intact liver functions may be the cause of unalteration in the concentrations of HDL-c,LDL-c and VLDL-c in the present work. Liver damage thought to be the result in alteration of above parameters (28). This work has also shown that the level of albumin was significantly reduced in vaccinated chickens when compared with the non vaccinated group. This finding was in agreement to (14). Reduction of serum albumin may be due to traumatic injury to kidney and urinary system (29), or may be due to tissue damage of kidney causing loss of large amount of albumin (18). This view may be supported by (30) who reported that vaccination with IB vaccine caused traumatic injury to kidney. Data also reported that serum globulin was increased post vaccination. Similar observation was recorded by (6) using IBD vaccine. This effect may be due to stimulation of the immune system in the birds (31). Values are expressed as mean±SE, Different letters in the same column refers to the significant differences at level P<0.05.  Values are expressed as mean±SE, Different letters in the same column refers to the significant differences at level P<0.05, *Significant differences from non vaccinated data at P<0.05.
It is concluded from this study, that vaccination have an effect on some biochemical parameters in serum of broiler chickens. Significant age related differences have also been found for these parameters in both non vaccinated and vaccinated groups.