Biodiversity Data Journal :
Research Article
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Corresponding author: Ivanka Lazarova (i_asenova_lazarova@abv.bg)
Academic editor: Emilian Stoynov
Received: 09 Mar 2023 | Accepted: 20 Apr 2023 | Published: 15 May 2023
© 2023 Tzvetan Chaprazov, Rusko Petrov, Dobri Yarkov, Yana Andonova, Ivanka Lazarova
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Chaprazov T, Petrov R, Yarkov D, Andonova Y, Lazarova I (2023) Basic blood biochemical parameters of wild common ravens (Corvus corax). Biodiversity Data Journal 11: e103271. https://doi.org/10.3897/BDJ.11.e103271
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Baseline haematological and biochemical blood parameters in healthy wild birds are key to managing wild populations and to saving critically ill individuals. This knowledge is crucial for the care, rehabilitation and the release of birds after treatment in wildlife rescue centres. Plasma levels provide valuable information for the evaluation of the physical condition of animals. The objective of this study was to obtain reference values of some basic biochemical blood parameters of wild common ravens (Corvus corax). Between 2020 and 2023, we took blood samples from the wild population of common ravens in Bulgaria (n = 36). We determined the values of 18 parameters - alanine transaminase (ALT, U/I), albumin (g/l), alkaline phosphatase (ALP, U/I), amylase (U/I), aspartate transaminase (AST, U/I), calcium (mmol/l), chloride (mmol/l), cholesterol (mmol/l), creatine kinase (CK, U/I), creatinine (μmol/l), blood glucose (mmol/l), lactate dehydrogenase (LDH, U/I), magnesium (mmol/l), phosphorus (mmol/l), total bilirubin (μmol/l), total protein (g/l), triglycerides (TG, mmol/l) and uric acid (μmol/l). We made a comparative analysis including the regions in which the groups were sampled and the time of year. Most of the presented results were comparable to published values of other species from the Corvidae family and some were higher (ALP, amylase, AST, CK, total protein and uric acid levels). Most of these could be explained by the capture- and handling stress. This is the first report in official literary sources presenting some basic biochemical blood parameters of healthy wild common ravens in Bulgaria. The results may be of use to scientists, veterinarians and other researchers in rescue and rehabilitation centres and they can provide the basis for further studies with regards to animal welfare and health assessment of the species.
wild bird health, ravens, blood biochemistry, rehabilitation centre
The common raven (Corvus corax) is the largest bird of the Crow family (Corvidae) (
Changing habitats negatively affect the population (
The goal of this research was to determine the baseline blood biochemical indexes for wild common ravens in Bulgaria in helping to preserve their populations in nature. This information could be used as a complementary tool for veterinary medicine in wildlife rehabilitation centres.
The research was carried out on 36 wild ravens in the Republic of Bulgaria in the period 2020-2023. The birds were captured individually with respect to humane measures aimed at stress reduction when working with wild birds. The ravens were caught in adaptation aviaries for griffon vultures (Gyps fulvus) and cinereous vultures (Aegypius monachus), part of projects funded by the EU LIFE Programme with aim of restocking and reintroduction of those species in the country. The project “Recovery of the Populations of Large European Vultures In Bulgaria” LIFE08 NAT/BG/000278 was implemented by Green Balkans - Stara Zagora NGO in partnership with the Fund for Wild Flora and Fauna (FWFF, Bulgaria) and the Bird of Prey Protection Society (BPPS, Bulgaria), during which 210 griffon vultures were released between 2010 and 2015. During 2015-2022, Green Balkans - Stara Zagora NGO together with FWFF, The Vulture Conservation Foundation (VCF, Netherlands), Junta de Extremadura (Spain) and EuroNatur (Germany) conducted project “Bright Future for Black Vulture in Bulgaria” LIFE14 NAT/BG/649, aiming for the recovery of the cinereous vulture in Bulgaria.
All common ravens were examined upon blood collection by a veterinary physician from the Wildlife Rehabilitation and Breeding Centre - Green Balkans, part of Green Balkans - Stara Zagora NGO. The birds were determined to be clinically healthy. Surfaces were disinfected with Desclean solution. We disinfected the area and collected 1.5 ml of whole blood from either the left or right basilic vein (Vena cutanea ulnaris superficialis) of all specimens tested. We immediately placed the blood into collection tubes containing lithium heparin. We used 3 ml syringes with 23G needles. We transported the samples to a laboratory, where they were processed within 4 hrs of collection using a BS-120 (Mindray, China) biochemical analyser.
We compared the values of the following 18 biochemical parameters - alanine transaminase (ALT, U/I), albumin (g/l), alkaline phosphatase (ALP, U/I), amylase (U/I), aspartate transaminase (AST, U/I), calcium (mmol/l), chloride (mmol/l), cholesterol (mmol/l), creatine kinase (CK, U/I), creatinine (μmol/l), blood glucose (mmol/l), lactate dehydrogenase (LDH, U/I), magnesium (mmol/l), phosphorus (mmol/l), total bilirubin (μmol/l), total protein (g/l), triglycerides (TG, mmol/l) and uric acid (μmol/l). A comparative analysis was made between the indicators of the birds in their different habitats, which were conditionally divided into two areas. The Southeast region includes Sinite kamani NP (n = 23) and Stara Zagora (n = 1), Northwest includes Vrachanski Balkan NP (n = 8), Troyan (n = 1) and Sofia (n = 3). A comparison between the biochemical parameters of the birds was also made with regards to the months in which the blood samples were obtained. The winter-spring season includes the months from February to May, the summer-autumn - from June to September. Results of all the determinations were presented as Means ± Standard Error with the minimum and maximum values. Significant difference was accepted at the probability level of p < 0.05. The study parameters were further analysed using one-way analysis of variance (ANOVA), provided in SPSS Statistics (SPSS-Inc., 2019, Chicago, USA).
We determined the mean blood biochemistry values of wild common ravens in Bulgaria (Table
Average values of some blood biochemical parameters of common ravens in Bulgaria.
Serum biochemistry parameters |
Mean ± Standard Error (n = 36) |
Minimum and maximum values |
AST U/I |
459.89 ± 21.27 |
171.00-674.00 |
ALT U/I |
85.75 ± 7.12 |
38.00-251.00 |
ALP U/I |
333.64 ± 60.46 |
18.00-1567.00 |
LDH U/I |
1035.78 ± 62.13 |
324.000-1757.00 |
CK U/I |
897.81 ± 106.08 |
114.00-2511.00 |
Cholesterol mmol/l |
5.02 ± 0.18 |
3.25-7.37 |
TG mmol/l |
1.17 ± 0.05 |
0.67-2.02 |
Chloride mmol/l |
115.11 ± 0.90 |
98.00-127.00 |
Amylase U/I |
1513.92 ± 72.23 |
957.00-2732.00 |
Calcium mmol/l |
2.17 ± 0.04 |
1.45-2.60 |
Phosphorus mmol/l |
1.79 ± 0.30 |
0.39-6.97 |
Magnesium mmol/l |
1.04 ± 0.04 |
0.66-1.45 |
Total protein g/l |
44.30 ± 0.83 |
32.20-53.80 |
Albumin g/l |
16.47 ± 0.35 |
8.60-21.60 |
Glucose mmol/l |
16.41 ± 0.43 |
9.43-20.53 |
Total bilirubin μmol/l |
12.23 ± 0.88 |
8.00-36.20 |
Creatinine μmol/l |
39.58 ± 0.70 |
29.00-49.00 |
Uric acid μmol/l |
672.85 ± 56.63 |
9.60-1625.00 |
Average values of some blood biochemical parameters of common ravens in Bulgaria and statistically significant values (in bold) between the areas where the samples were taken.
Serum biochemistry parameters |
Area |
N |
Mean |
F |
Sig. |
AST U/I |
Southeast |
24 |
506.54 |
12.89 |
0.00 |
Northwest |
12 |
366.58 |
|||
ALT U/I |
Southeast |
24 |
94.63 |
3.31 |
0.08 |
Northwest |
12 |
68.00 |
|||
ALP U/I |
Southeast |
24 |
143.75 |
43.92 |
0.00 |
Northwest |
12 |
713.42 |
|||
LDH U/I |
Southeast |
24 |
926.54 |
7.29 |
0.01 |
Northwest |
12 |
1254.25 |
|||
CK U/I |
Southeast |
24 |
1083.92 |
7.26 |
0.01 |
Northwest |
12 |
525.58 |
|||
Cholesterol mmol/l |
Southeast |
24 |
4.64 |
11.53 |
0.00 |
Northwest |
12 |
5.79 |
|||
TG mmol/l |
Southeast |
24 |
1.14 |
0.72 |
0.40 |
Northwest |
12 |
1.23 |
|||
Chloride mmol/l |
Southeast |
24 |
117.17 |
14.30 |
0.00 |
Northwest |
12 |
111.00 |
|||
Amylase U/I |
Southeast |
24 |
1371.33 |
9.74 |
0.00 |
Northwest |
12 |
1799.08 |
|||
Calcium mmol/l |
Southeast |
24 |
2.14 |
0.62 |
0.44 |
Northwest |
12 |
2.22 |
|||
Phosphorus mmol/l |
Southeast |
24 |
0.79 |
60.71 |
0.00 |
Northwest |
12 |
3.81 |
|||
Magnesium mmol/l |
Southeast |
24 |
0.93 |
29.27 |
0.00 |
Northwest |
12 |
1.25 |
|||
Total protein g/l |
Southeast |
24 |
44.14 |
0.07 |
0.79 |
Northwest |
12 |
44.63 |
|||
Albumin g/l |
Southeast |
24 |
16.16 |
1.59 |
0.22 |
Northwest |
12 |
17.08 |
|||
Glucose mmol/l |
Southeast |
24 |
16.88 |
2.43 |
0.13 |
Northwest |
12 |
15.47 |
|||
Total bilirubin μmol/l |
Southeast |
24 |
12.35 |
0.04 |
0.85 |
Northwest |
12 |
11.99 |
|||
Creatinine μmol/l |
Southeast |
24 |
39.63 |
0.01 |
0.93 |
Northwest |
12 |
39.50 |
|||
Uric acid μmol/l |
Southeast |
24 |
671.29 |
0.00 |
0.97 |
Northwest |
12 |
675.97 |
Average values of some blood biochemical parameters of common ravens in Bulgaria and statistically significant values (in bold) with regards to the season of sample collection.
Serum biochemistry parameters |
Season |
N |
Mean |
F |
Sig. |
AST U/I |
winter-spring |
24 |
520.58 |
29.59 |
0.00 |
summer-autumn |
12 |
338.50 |
|||
ALT U/I |
winter-spring |
24 |
92.79 |
2.01 |
0.17 |
summer-autumn |
12 |
71.67 |
|||
ALP U/I |
winter-spring |
24 |
169.75 |
24.61 |
0.00 |
summer-autumn |
12 |
661.42 |
|||
LDH U/I |
winter-spring |
24 |
975.83 |
1.91 |
0.18 |
summer-autumn |
12 |
1155.67 |
|||
CK U/I |
winter-spring |
24 |
1159.17 |
18.06 |
0.00 |
summer-autumn |
12 |
375.08 |
|||
Cholesterol mmol/l |
winter-spring |
24 |
4.66 |
9.92 |
0.00 |
summer-autumn |
12 |
5.74 |
|||
TG mmol/l |
winter-spring |
24 |
1.11 |
2.41 |
0.13 |
summer-autumn |
12 |
1.28 |
|||
Chloride mmol/l |
winter-spring |
24 |
116.50 |
5.31 |
0.03 |
summer-autumn |
12 |
112.33 |
|||
Amylase U/I |
winter-spring |
24 |
1372.17 |
9.59 |
0.00 |
summer-autumn |
12 |
1797.42 |
|||
Calcium mmol/l |
winter-spring |
24 |
2.15 |
0.13 |
0.72 |
summer-autumn |
12 |
2.19 |
|||
Phosphorus mmol/l |
winter-spring |
24 |
0.81 |
54.01 |
0.00 |
summer-autumn |
12 |
3.76 |
|||
Magnesium mmol/l |
winter-spring |
24 |
0.93 |
26.08 |
0.00 |
summer-autumn |
12 |
1.24 |
|||
Total protein g/l |
winter-spring |
24 |
44.35 |
0.01 |
0.94 |
summer-autumn |
12 |
44.21 |
|||
Albumin g/l |
winter-spring |
24 |
16.35 |
0.23 |
0.63 |
summer-autumn |
12 |
16.71 |
|||
Glucose mmol/l |
winter-spring |
24 |
16.82 |
1.78 |
0.19 |
summer-autumn |
12 |
15.60 |
|||
Total bilirubin μmol/l |
winter-spring |
24 |
11.39 |
1.86 |
0.18 |
summer-autumn |
12 |
13.91 |
|||
Creatinine μmol/l |
winter-spring |
24 |
39.42 |
0.11 |
0.74 |
summer-autumn |
12 |
39.92 |
|||
Uric acid μmol/l |
winter-spring |
24 |
696.29 |
0.34 |
0.57 |
summer-autumn |
12 |
625.97 |
Conservation of endangered bird species can be refined by expanding the knowledge regarding morbidity and mortality of this group of animals (
From the investigated blood parameters, the following belong to the group of liver indicators - albumin, ALP, ALT, AST, LDH, total bilirubin and total protein. The liver transaminases AST and ALT change their plasma concentrations according to the functional state of the liver (
This is the first report on some basic biochemical blood parameters of healthy, wild common ravens in Bulgaria. The results provide an opportunity to expand further on the study, as well as to monitor and conserve the species populations. Most of the results obtained were similar to those published for other members of the Corvidae family, but there were also differences that may be explained by the capture- and handling stress, although others could be species-specific or the result of the different diet of the birds at a regional or national level. These results can be useful for the treatment and protection of the species in rescue and rehabilitation centres in the country and in Europe.
The study is conducted as part of research project “Comparative study of some basic blood biochemical parameters in captive-bred bearded vultures, griffon vultures, cinereous vultures, Egyptian vultures and common ravens in Bulgaria”, funded by Trakia University (Bulgaria). The authors express gratitude to Denitsa Petkova, Hristo Peshev, Ivelin Ivanov, Simeon Marin and Stefka Dimitrova for the assistance provided during the sample collection.