This work was performed at the University of Selcuk.
Serum Amyloid A and Haptoglobin Concentrations and Liver Fat Percentage in Lactating Dairy Cows with Abomasal Displacement
Version of Record online: 4 JAN 2010
Copyright © 2010 by the American College of Veterinary Internal Medicine
Journal of Veterinary Internal Medicine
Volume 24, Issue 1, pages 213–219, January/February 2010
How to Cite
Guzelbektes, H., Sen, I., Ok, M., Constable, P.D., Boydak, M. and Coskun, A. (2010), Serum Amyloid A and Haptoglobin Concentrations and Liver Fat Percentage in Lactating Dairy Cows with Abomasal Displacement. Journal of Veterinary Internal Medicine, 24: 213–219. doi: 10.1111/j.1939-1676.2009.0444.x
- Issue online: 4 JAN 2010
- Version of Record online: 4 JAN 2010
- Submitted May 26, 2009; Revised August 5, 2009; Accepted October 20, 2009.
- Abomasal displacement;
- Serum amyloid A
Background: There has been increased interest in measuring the serum concentration of acute phase reactants such as serum amyloid A [SAA] and haptoglobin [haptoglobin] in periparturient cattle in order to provide a method for detecting the presence of inflammation or bacterial infection.
Objectives: To determine whether [SAA] and [haptoglobin] are increased in cows with displaced abomasum as compared with healthy dairy cows.
Animals: Fifty-four adult dairy cows in early lactation that had left displaced abomasum (LDA, n = 34), right displaced abomasum or abomasal volvulus (RDA/AV, n = 11), or were healthy on physical examination (control, n = 9).
Materials and Methods: Inflammatory diseases or bacterial infections such as mastitis, metritis, or pneumonia were not clinically apparent in any animal. Jugular venous blood was obtained from all cows and analyzed. Liver samples were obtained by biopsy in cattle with abomasal displacement.
Results: [SAA] and [haptoglobin] concentrations were increased in cows with LDA or RDA/AV as compared with healthy controls. Cows with displaced abomasum had mild to moderate hepatic lipidosis, based on liver fat percentages of 9.3 ± 5.3% (mean ± SD, LDA) and 10.8 ± 7.7% (RDA/AV). [SAA] and [haptoglobin] were most strongly associated with liver fat percentage, rs=+0.55 (P < .0001) and rs=+0.42 (P= .0041), respectively.
Conclusions and Clinical Importance: An increase in [SAA] or [haptoglobin] in postparturient dairy cows with LDA or RDA/AV is not specific for inflammation or bacterial infection. An increase in [SAA] or [haptoglobin] may indicate the presence of hepatic lipidosis in cattle with abomasal displacement.
serum aspartate aminotransferase
γ glutamyl transferase
left displaced abomasums
right displaced abomasums
serum amyloid A
Left displaced abomasum (LDA), right displaced abomasum (RDA), and abomasal volvulus (AV) are common abdominal diseases of lactating dairy cows characterized by varying degrees of abomasal distension and displacement.1 Impaired abomasal motility and increased accumulation of gas are considered prerequisites for development of LDA,2 RDA, and AV.3 Many cows with LDA suffer from concurrent diseases such as hepatic lipidosis and inflammatory disorders or bacterial infections such as mastitis, metritis, retained placenta, and pneumonia3,4 that result in decreased appetite and nutritional stress. Concurrent disease is less frequent in cows with AV,3 and is presumed to be less frequent in cows with RDA. However, in cows with AV, the presence of a hemorrhagic, strangulating obstruction of the abomasum, duodenum, and possibly omasum (omasal-abomasal volvulus) or reticulum (reticulo-omasal-abomasal volvulus) and increased luminal pressure leads to ischemia and therefore may result in necrosis of the abomasum, peritonitis, and inflammation.3,5–7
Acute phase proteins are plasma proteins, the concentrations of which increase when animals are subjected to external stressors such as transportation and solitary housing8,9 or internal stimuli such as inflammation, bacterial infection, and surgical trauma.10 Acute phase proteins have been categorized as positive or negative depending on whether their concentration increases (positive) or decreases (negative) in response to an external or internal stimulus.1 Serum amyloid A (SAA), haptoglobin, and fibrinogen are important positive acute phase proteins in cattle10,11 and are produced by the liver in response to endogenous release of glucocorticoids and proinflammatory cytokines.12,13 Important negative acute phase proteins in cattle include albumin, transferrin, and paraoxonase.10,14
There has been increased interest in measuring the serum concentrations of acute phase reactants in cattle to provide a method for the early detection of inflammation or bacterial infection. We hypothesized that the concentrations of 2 positive acute phase reactants ([SAA], [haptoglobin]) in serum would be increased, and the concentration of a negative acute phase reaction [albumin] in serum would be decreased in cows with displaced abomasum as compared with healthy dairy cows. The basis for our hypothesis was the high likelihood of nutritional stress in cattle with LDA, RDA, or AV, and the presence of peritonitis in some cattle with AV. We confined our investigation to cattle that did not have clinical evidence of inflammation or bacterial infection to minimize the confounding effect of clinical disease on the acute phase response.
Materials and Methods
The institutional ethical committee approved this prospective study. Forty-two Brown Swiss-Holstein-Friesian cross cows with LDA and 16 Brown Swiss-Holstein-Friesian cross cows with RDA or AV in the 1st 3 weeks of lactation were admitted to the Teaching Hospital for surgery. Cows were 3–8 years of age and had mean daily milk yields of 30 kg for cows with LDA, 23 kg for cows with RDA, and 25 kg for cows with AV before LDA, RDA, or AV was diagnosed. Routine physical examination, including simultaneous auscultation and percussion of the abdomen, ballottement of the abdomen for a splashing sound indicating the presence of an air-fluid interface in a large viscus, and palpation per rectum were performed on each cow.15 Inflammatory conditions or bacterial infections, such as mastitis, metritis, and pneumonia, were detected clinically in 8 cattle with LDA and in 5 cattle with RDA or AV during the study period. Data for these cattle were excluded from the study reported here.
Nine clinically healthy postparturient Brown Swiss-Holstein-Friesian cross cows from a local dairy farm were used as a healthy reference group. These cows were 3–8 years of age, in the 1st 2–3 weeks of lactation, and were reported by the owner to have a daily milk yield ranging from 25 to 30 kg on twice daily milking.
Blood samples were collected from the jugular vein immediately before surgery in cows with displaced abomasum as well as from healthy cattle. Cows were handled gently to minimize stress before bleeding. An aliquot of blood was placed into glass tubes for determination of [SAA], [haptoglobin], and [albumin] concentrations and serum biochemical analysis; the tubes were centrifuged after clotting and the serum harvested and stored at −20°C until analyzed. A 2nd aliquot of blood was placed into a plastic tube containing EDTA for routine hematologic examination.
Liver biopsy samples were obtained preoperatively in cows with LDA percutaneously through the right 11th to 12th intercostal space.16 Liver biopsy samples were obtained intraoperatively in cows with RDA or AV after the abomasum had been repositioned. Liver biopsy samples were not obtained from healthy cattle.
A right flank laparotomy under regional analgesia was performed on cows with a presumptive clinical diagnosis of LDA, RDA, or AV, and the diagnosis was confirmed during surgery using established criteria.5,7,15 RDA was not differentiated from AV in some cattle and therefore this group was combined as an RDA/AV group for comparison purposes, but, the majority of cattle in this group had AV. A right flank omentopexy was performed as described17 after the abomasum had been returned to its normal position in the abdomen. Cows were hospitalized for 1 day after surgery and then discharged. Clinical outcome was determined at least 2 weeks after surgery by telephone communication with the owner.
[SAA] concentrations were determined by sandwich ELISA.a The manufacturer of this assay reported a limit of detection in bovine serum of 0.3 mg/L and a reference range of 9–150 mg/L. Cutpoints for [SAA] of > 9 mg/L18 or > 600 mg/L19 have been recommended to identify an acute phase response in cattle. Estimated values for sensitivity and specificity (versus clinical examination as the gold standard) for a cutpoint of >600 mg/L are 0.79 and 0.60, respectively.19
Serum [haptoglobin] concentrations were determined by sandwich ELISAb that has been used previously in cattle.11 The manufacturer of this assay reported a limit of detection in bovine serum of 0.25 mg/L. Cutpoints for serum [haptoglobin] of >150 mg/L19 or >500 mg/L20 have been recommended to identify an acute phase response in postparturient dairy cows, and >670 mg/L was recommended to identify cattle with traumatic reticuloperitonitis.11 Estimated values for sensitivity and specificity (versus clinical examination as the gold standard) for a cutpoint of serum [haptoglobin] of >150 mg/L are 0.83 and 0.58, respectively.19
Serum aspartate aminotransferase (AST) and γ glutamyl transferase (GGT) activities, as well as serum glucose, total bilirubin, cholesterol, and [albumin] concentrations, were measured with an automatic analyzer.c Hematologic analysis was performed with an automated hematology cell counter.d
Liver biopsy samples were placed in Baker's formal-Ca solution and fixed in paraffin for at least 16 hours. Sections (12 μm) were cut from each fixed liver sample and stained with oil Red O and Sudan Black B. The sections were examined under light microscopy as described21,22 and the percentage volume of visible fat in hepatic parenchymal cells estimated by a stereological point counting method. The extent of fat infiltration of the liver was categorized as mild (<10%, <10 μm2/100 μm2), moderate (10–20%, 10–20 μm2/100 μm2), and severe (>20%, >20 μm2/100 μm2) on the basis of the percentage volume of visible fat.23
Cows with clinical evidence of inflammation or bacterial infection were not included in the statistical analysis to minimize the confounding effect of clinical disease on the acute phase response. Data were expressed as mean and standard deviation (normally distributed variables) or geometric mean and 95% confidence interval for the geometric mean (variables with skewed distributions). The level of statistical significance was P < .05. One-way analysis of variance was used to compare mean values among cows in groups C, LDA, and RDA/AV; Tukey's studentized range test was used for posthoc comparisons when indicated by a significant F-test for a group. The 95% confidence interval for the estimated percentage of cows with moderate to severe hepatic lipidosis was calculated by a software program.e
For cows with displaced abomasum, Spearman's correlation coefficients (rs) were calculated to explore the association between [SAA], [haptoglobin], and [albumin] concentration with other study variables, including hematologic factors (numbers of erythrocytes, leukocytes, and platelets; packed cell volume and hemoglobin concentration) and serum biochemical factors (AST and GGT activities, glucose, total bilirubin, cholesterol, urea, creatinine, total protein, and globulin concentrations), rectal temperature, and liver fat percentage. Forward stepwise linear regression was used to explore linear associations between [SAA], [haptoglobin], and [albumin] and serum biochemical and hematologic factors for cows with displaced abomasum. A P < .20 for entry and P < .05 for remaining in the model were used for the stepwise regression procedure. A statistical software programf was used for all statistical analyses.
Statistical analysis was completed using data from 34 cows with LDA and 11 cows with RDA or AV that did not have evidence of other clinical disease. Cows with abomasal displacement had fair to moderate appetites, decreased rumen contraction frequency, and decreased milk production. Rectal temperature was similar for cows in all 3 groups (Table 1). Five cows with RDA/AV were treated with IV fluids postoperatively based on their degree of dehydration and acid-base abnormalities. Clinical condition improved after surgical correction of the abomasal displacement, and all cows were discharged from the hospital and were alive at least 2 weeks after discharge.
|Parameters||Control||LDA||RDA/AV||Probability of F-Test for Group|
|(n = 9)||(n = 34)||(n = 11)|
|Rectal temperature (°C)||38.2 ± 0.2||38.3 ± 0.4||38.3 ± 0.2||0.68|
|Liver fat (%)||ND||9.3 ± 5.3||10.8 ± 7.7||0.47|
|Acute phase proteins|
|Amyloid A (μg/mL)||12 (3 to 43)a||55 (13 to 227)b||90 (46 to 177)b||< 0.0001|
|Haptoglobin (μg/mL)||36 (14 to 92)a||70 (22 to 229)b||88 (37 to 208)b||0.0021|
|Haptoglobin : Amyloid A||3.2 (0.5 to 21.4)a||1.3 (0.3 to 5.8)b||1.0 (0.5 to 1.8)b||0.0022|
|Albumin (g/dL)||3.98 ± 0.36||3.58 ± 0.73||3.50 ± 0.31||0.18|
|Serum biochemical analysis|
|Total protein (g/dL)||6.69 ± 0.46||6.90 ± 0.89||6.46 ± 0.58||0.25|
|Globulin (g/dL)||2.71 ± 0.76||3.33 ± 1.34||2.96 ± 0.73||0.31|
|Urea (mg/dL)||10 (4 to 23)a||12 (5 to 29)a||20 (6 to 61)b||0.0031|
|Creatinine (mg/dL)||0.92 ± 0.20||1.09 ± 0.25||1.19 ± 0.36||0.091|
|Glucose (mg/dL)||51 (32 to 83)a||80 (45 to 189)b||144 (46 to 452)c||< 0.0001|
|Cholesterol (mg/dL)||168 ± 40a||121 ± 35b||120 ± 31b||0.0027|
|Total bilirubin (mg/dL)||0.25 (0.13 to 0.48)a||0.53 (0.12 to 2.31)b||0.55 (0.31 to 0.97)b||0.0077|
|AST (U/L)||67 (36 to 122)||108 (31 to 375)||104 (42 to 258)||0.074|
|GGT (U/L)||29 (12 to 68)a||59 (18 to 198)b||50 (27 to 94)b||0.0045|
|Leukocytes (cells/μL)||8,166 (6,531 to 10,210)||8,204 (4,625 to 14,552)||9,550 (5,054 to 18,045)||0.29|
|Platelets (103 cells/μL)||313 ± 95||315 ± 81||378 ± 103||0.12|
|Erythrocytes (106 cells/μL)||7.1 ± 0.5a||6.9 ± 1.3a||8.1 ± 1.3b||0.019|
|Hemoglobin (mg/dL)||10.6 ± 1.1||10.7 ± 1.6||11.8 ± 2.1||0.12|
|Packed cell volume (vol %)||31.4 ± 3.4||32.1 ± 4.8||33.4 ± 5.7||0.63|
Liver Fat Percentages
Liver fat percentages were similar for cows in the LDA and RDA/AV groups (Table 1). Eleven of 34 (32%; 95% confidence interval for estimated proportion, 16–48%) cows with LDA and 3 of 11 (27%; 95% confidence interval for estimated proportion, 1–53%) cows with AV/RDA had liver fat percentages exceeding 10% indicating the presence of moderate to severe hepatic lipidosis; all 14 of these cows received ancillary treatment for hepatic lipidosis.
Acute Phase Reactants
[SAA] and [haptoglobin] were increased, and the ratio of [haptoglobin] to [SAA] was decreased, in cows with LDA or RDA/AV compared with controls (Table 1). In contrast, [albumin] was similar in all 3 groups. None of the cows with LDA or RDA/AV had [SAA] > 600 mg/L (Fig 1). None of the cows with LDA or RDA/AV had [haptoglobin] > 500 mg/L (Fig 2), and only 3 cows (7%) with LDA or RDA/AV had [haptoglobin] > 150 mg/L.
The variable most highly correlated with [SAA] was liver fat percentage (rs= 0.55, P <.0001; Fig 1). The variable most highly correlated with [haptoglobin] was liver fat percentage (rs= 0.42, P= .0041; Fig 2). Stepwise multivariable regression indicated that [SAA] was positively associated with liver fat percentage (P < .0001, incremental R2= 0.32), erythrocyte count (106 cells/μl; P= .0011; incremental R2= 0.15), and [haptoglobin] (incremental R2= 0.05), such that [SAA] =−24.3 + 2.26 × (liver fat percentage) + 8.3 × (erythrocyte count) + 0.18 × [haptoglobin] (R2= 0.53). In other words, [SAA] in cattle with abomasal displacement and no clinical evidence of bacterial infection was primarily associated with the liver fat percentage. Stepwise multivariable regression indicated that [haptoglobin] was positively associated with [SAA] (P < .0001, incremental R2= 0.22) and negatively associated with the serum urea concentration ([urea]; incremental R2= 0.08) such that: [haptoglobin] = 59.0 + 0.64 × [SAA]−1.2 × [urea], R2= 0.30. In other words, [haptoglobin] in cattle with abomasal displacement and no clinical evidence of bacterial infection was primarily associated with [SAA].
Serum Biochemical and Hematologic Analyses
Serum total protein, globulin, and creatinine concentrations were similar for all 3 groups, but serum urea concentration was increased in cows with RDA/AV (Table 1).
Serum total bilirubin concentration was increased, and serum cholesterol concentration decreased, in cows with LDA or RDA/AV compared with controls (Table 1). Serum AST activity was similar in all 3 groups, whereas serum GGT activity was increased in LDA cows, but not in RDA/AV cows, compared with controls. Serum glucose concentration was highest in cows with RDA/AV, intermediate in cows with LDA, and lowest in control cows.
Blood erythrocyte count was higher in cows with RDA/AV than LDA, but both groups were similar to controls (Table 1). Blood leukocyte count, platelet count, hemoglobin concentration, and packed cell volume were similar in all 3 groups.
The 1st main finding of the study reported here was that an increase in [SAA] or [haptoglobin] in postparturient dairy cows with LDA or RDA/AV is not specific for inflammation or bacterial infection. The 2nd main finding was that a mild to moderate increase in [SAA] or [haptoglobin] may indicate the presence of hepatic lipidosis in cattle with abomasal displacement.
SAA is an apolipoprotein that is rapidly synthesized and released by bovine hepatocytes in response to inflammation or bacterial infection.24,25 The specific role of SAA in the inflammatory response is incompletely understood but amyloid A is believed to have immune-related functions including clearance of plasma endotoxin and high density lipoproteins.24,26 The 3–5-fold increase in [SAA] in cows with displaced abomasum, compared with healthy lactating cows, was similar in magnitude to that reported previously in cows with traumatic reticuloperitonitis, mastitis, metritis, pododermatitis, renal amyloidosis,11,27 and postsurgical abdominal infection.28
A potential confounding factor for the interpretation of [SAA] in cattle with displaced abomasum is that [SAA] normally increases at calving.8,19,25,26,29,30 Increased [SAA] therefore is not specific for inflammation or bacterial infection in the postparturient dairy cow,19,31 and inflammation did not appear to be the cause for the increase in [SAA] in the cows in the study reported here because white blood cell counts, platelet counts, and rectal temperature were similar for all 3 groups, and clinical evidence of an infectious process was not identified in any cow. Moreover, the results of forward stepwise regression indicated that [SAA] was primarily associated with liver fat percentage instead of other indicators of inflammation, such as leukocyte count and [haptoglobin] and [albumin]. Our results are consistent with those of a preliminary experimental study in 8 periparturient dairy cows that identified a positive association between liver fat content and [SAA].29 Our results also suggest that determination of [SAA] in periparturient dairy cattle may have clinical utility as a predictor of liver fat percentage in cattle without evidence of bacterial infection, in that the incremental R2 value of 0.32 for the relationship between [SAA] and liver fat percentage was similar to that reported when a multivariable model containing serum nonesterified fatty acid, glucose, and urea concentrations (but not [SAA]) was applied to dairy cattle at a similar stage of lactation (R2= 0.33).32
Our mean value for [SAA] of healthy dairy cattle in early lactation was similar to that reported for dairy cows in Turkey,27 Finland,33 and Denmark.9 For comparison, mean [SAA] was reported to be lower in similarly aged beef cows of different breeds in France34 but higher in Holstein-Friesian dairy cows in Canada,26 Belgium,19 and Iran.28 The reason for the variation in [SAA] for healthy cattle is not apparent, but interlaboratory variability may impact the clinical utility of using [SAA] > 600 mg/L as a cutpoint for indicating the presence of inflammation or bacterial infection in postparturient cattle. This cutpoint may be too high, based on reported values for [SAA] in cows with infectious diseases28 and experimentally induced Escherichia coli mastitis.33
The approximately 2-fold increase in [haptoglobin] in cows with displaced abomasum, compared with that of healthy lactating cows, was similar in magnitude to that reported previously in cows with LDA and cows with traumatic reticuloperitonitis, mastitis, metritis, pododermatitis, and renal amyloidosis.11,27 Haptoglobin is thought to be a sensitive screening test for the release of endogenous glucocorticoids and proinflammatory cytokines in cattle.35 Our finding that [haptoglobin] was associated with liver fat percentage extends preliminary reports of an association based on small numbers of cattle.36,37 More research is needed to increase our understanding of changes in the concentration and kinetics of [haptoglobin] in cattle with hepatic lipidosis.
A potential confounder for the interpretation of [haptoglobin] in cattle with displaced abomasum is that trauma, and increased plasma cortisol and estradiol concentrations associated with parturition, increase [haptoglobin]29,30,38–40 with a 2-day starvation period augmenting the effect of cortisol.35 Our findings that the relative increase in [haptoglobin] was smaller than that of [SAA], and that [haptoglobin] was most strongly associated with [SAA], suggest that measurement of [SAA] may have greater clinical utility than measurement of [haptoglobin] in cattle with abomasal displacement.
Our finding that [albumin] was not decreased in cattle with abomasal displacement suggests that albumin is not as sensitive an acute phase reactant as is SAA. Moreover, [albumin] is decreased for 2 weeks after calving in lactating dairy cattle, partly as a result of increased plasma volume and decreased albumin synthesis,41,42 further decreasing the clinical utility of [albumin] as an acute phase reactant in postparturient cattle.
Endotoxemia has long been suspected to play a role in the pathogenesis of abomasal displacement43 because cows with LDA may have concurrent inflammatory diseases that are potential sources of endotoxin,3 serum TNF-α activity was increased in dairy cows with LDA,44 and because endotoxemia is associated with abomasal hypomotility.45,46 TNF-α therefore may provide a link among hepatic lipidosis, release of acute phase proteins, and abomasal displacement because endotoxin causes TNF-α to be released, which may result in release of SAA. However, endotoxemia does not occur more often in cows with LDA or AV than in healthy control cows during the postparturient period,7 and adipocytes are an important source of TNF-α.47 A possible mechanism for the results observed in the study reported here is that the negative energy balance in postparturient dairy cows with abomasal displacement causes a rapid mobilization of free fatty acids from adipocytes and release of TNF-α, leading to increased serum nonesterified fatty acid concentration and liver fat percentage,47 and increased hepatic synthesis of SAA. Support for this mechanism is provided by endotoxin infusion studies in heifers. Endotoxin caused an increase in serum TNF-α concentration that preceded an increase in [SAA], with no increase in [haptoglobin].48
Nutritional stress in dairy cattle can be evaluated by determining the serum concentration of nonesterified fatty acids, β-OH butyrate, acetoacetate, cholesterol, and glucose34 and liver fat percentage, with the latter being regarded as the most accurate indicator of nutritional stress.49 Liver fat percentage is increased in cows with abomasal displacement.50 Liver fat percentages in healthy cattle typically are 5%, and are increased to 8% in healthy cows shortly after calving and to 33% in cows with postparturient ketosis.49 The cows with displaced abomasum in the study reported here therefore only had mild to moderate hepative lipidosis. Natural and experimental cases of hepatic lipidosis in dairy cows are characterized by decreased serum concentrations of cholesterol (especially cholesterol esters), phospholipids, and triglycerides an increase in plasma oleic acid concentration (C18:2n-6), and a decrease in linoleic acid concentration (C18:2n-6).31 Low serum cholesterol and triglyceride concentrations are consistently observed in cattle with fatty liver 21,51 and hypocholesterolemia is attributed to impaired hepatic high density lipoprotein secretion because most plasma cholesterol is in the high density lipoprotein fraction.31
A potential confounder for the study reported here was that cows with LDA or RDA/AV were transported to the Teaching Hospital for surgical correction, whereas control cattle were not transported. We believe that this difference minimally affected our results, because 4–6 hours of transportation did not alter [SAA] or [haptoglobin] of 7 lactating Holstein-Friesian cows and 2 Holstein-Friesian heifers when blood samples were obtained 8 hours after the start of transportation.9
In conclusion, results of the study reported here indicate that increased liver fat percentage in lactating dairy cows is associated with an increase in [SAA]. We believe this association provides a possible reason for the normal increase in [SAA] in dairy cows 1-week postpartum.19 A mild to moderate increase in [SAA] or [haptoglobin] in postparturient dairy cows with LDA or RDA/AV is not specific for inflammation or bacterial infection because such an increase may indicate the presence of hepatic lipidosis in cattle with abomasal displacement.
aInvitrogen Immunoassay Kit #KNA0012; Invitrogen Corporation, Carlsbad, CA
bLife Diagnostics Inc, West Chester, PA
cAbbott, C8000 Architect, Chicago, IL
dMedonic CA 350, Medonic, Stockholm, Sweden
eWin Episcope 2.0; http://www.zod.wau.nl/genr/epi.html
fSAS 9.1; SAS Inc, Cary, NC
This study was supported by the University of Selcuk, Scientific Research Project Office.
- 1Disease of abomasum. In: Veterinary Medicine, 10th ed. Philadelphia, PA: WB Saunders; 2007:353–374., , , et al.
- 16Liver biopsies in cattle. Comp Cont Edu Pract Vet 1995;7:327–332.,
- 21Lipid and lipoprotein levels in dairy cows with fattyliver. Tr J Vet Anim Sci 2003;27:295–299., , , et al.
- 22Liver function in cows with retained placenta. Tr J Vet Anim Sci 2005;29:775–778.,
- 23Fatty liver syndrome associated with some postparturient period disease. Selcuk Univ Vet Fak Derg 1988;44:43–52., , , et al.
- 28Evaluation of serum and milk amyloid A in some inflammatory diseases of cattle. Iran J Vet Res 2008;9:222–226., ,
- 29A new understanding of the causes of fatty liver in dairy cows. Adv Dairy Tech 2005;17:97–112.
- 33Acute phase response in two consecutive experimentally induced E. coli intramammary infections in dairy cows. Acta Vet Scand 2008;13:50–68., , , et al.
- 44Serum tumor necrosis factor–alpha activity in dairy cows with abomasal displacement: The potential for anti-cytokine therapy. J Turkish Vet Surgery 2004;10:28–32., , , et al.
- 46Studies on abomasal emptying in cattle. In: Aetiologie, Pathogenese, Diagnostic, Prognoses, Therapie und Prophylaxe der Dislocatio abomasi. Leipzig, Germany: Leipziger Universitätsverlag; 2000:113–126.