Clinical observations
The most common clinical signs observed in the study were, postparturient inappetance (98.3 per cent), reduced milk yield (95.53 per cent) and weight loss (90 per cent). Those common signs were in concurrence with the observations of
Nagarajan (1990). Other signs were dullness, reduced rumen motility, lameness and occasional vague signs of a central nervous system disturbance such as ataxia with an odd stare recorded in the present study were in agreement with
Adewuyi et al., (2005). One of the common clinical signs of weight loss was in concurrence with the observations of
Nagarajan (1990), which was reported to be due to the mobilization of fat store from body reserve, during early lactation to compensate energy requirement, as stated by
Katoh (2002). The nervous sign recorded in the present study was in accordance with
Rehage et al., (1999) who reported about the development of hepatic encephalopathy which was characterized by depressed consciousness, ataxia and coma in severe cases of fatty liver syndrome. The possible reason for the hepatic encephalopathy could be due to the increased levels of toxic metabolic products such as ammonia, uric acid and decreased levels of blood glucose, that occurred in fatty liver syndrome
(Sevinc et al., 2003).
Concurrent diseases
The concurrent diseases recorded in fatty liver syndrome cases were, Ketosis (32.39 per cent), Anaplasmosis (17.80 per cent), Repeat breeder (16.40 per cent), Mastitis (12.67 per cent), Ruminal impaction (5.40 per cent), Abortion (5.40 per cent), Recumbency (4.10 per cent), Metritis (4.10 per cent), Theileriosis (2.70 per cent), Dystocia (1.40 per cent), Retained fetal membrane (1.40 per cent) and Ruminal acidosis (1.40 per cent).
Combination of ketosis and Mastitis (4.1 per cent), ketosis and Anaplasmosis (4.1 per cent), ketosis and Theileriosis (1.4 per cent), Mastitis and Metritis (1.4 per cent), Abortion and Anaplasmosis (1.4 per cent) and Repeat breeder and Anaplasmosis (4.1 per cent) were also recorded along with clinical cases of fatty liver.
The results of the present study were in accordance with the observations of Esposito
et al.,
(2014), who also recorded the above-mentioned diseases to occur concurrently in fatty liver syndrome, which was attributed to the interplay between the immune, endocrine, metabolic systems and diminished immune competence at calving as proposed by
Trevisi et al., (2011).
The occurrence of ketosis to be the major concurrent disease in fatty liver syndrome in the present study was supported by
Brindle et al., (1985) who hypothesized that, the high demand for gluconeogenesis which was prominently increased during early lactation for the synthesis of milk lactose resulted in exhaustion of oxaloacetic acid and diversion of acetyl-CoA towards ketogenesis, resulting in ketosis. While
Top (1995) proposed ketosis as a driving force for the occurrence of fatty liver syndrome through the evidence that lipolysis was not started before the blood glucose concentrations had decreased.
The incidence of infectious diseases in the present study might be attributed to suppression of immune function and increase in concentrations of pro-inflammatory cytokines as reported by
Ametaj et al., (2002) and decreased capacity of leucocyte to migrate into the infected mammay gland or uterus as the reason for non-responsive mastitis in fatty liver syndrome
(Zerbe et al., 2000).
B-mode ultrasonography
Normal study (Control group)
In the present study, liver could be visualized from 12
th intercostal space to 7th intercostal space, which was in accordance with the observations of
Braun (2009). The ultrasonographic patterns of homogenous echogenecity, clear visualization of intrahepatic vessel margins and diaphragm (Plate 1) were in agreement with the observations of
Tharwat et al., (2012) who suggested the homogenous echogenecity to be caused mainly by a series of alternate collagen-water interfaces. The location of various intrahepatic structures and the anatomical proximity of liver margin to various visceral organs, as visualized through different intercostal spaces were also in concurrence with that of
Braun (2009) and
Starke et al., (2010).
There was a good correlation between B-mode ultrasonographic pattern of liver and the histopathological study of liver biopsy sample.
B-mode ultrasonographic pattern in mild fatty liver
Bright pattern, with visibility of intrahepatic vessel walls and visibility of diaphragm were the striking appearances of the B-mode ultrasonogram which correlates with the observations of
Tharwat et al., (2012) and
Besheer et al., (2023). The appearance of bright pattern could be attributed to the lower acoustic impedance of fat droplets, in contrast to the hypoechoic nature of normal liver parenchyma
(Acorda et al., 1994). An earlier sign of deposition of fat droplets only around the intrahepatic vessels, with normal hepatic parenchyma was also recorded (Plate 2), which ranks the B-mode ultrasonography to be a more precise diagnostic tool.
B-mode ultrasonographic pattern in moderate fatty liver
The major pattern of B-mode ultrasonogram recorded in moderate fatty infiltration was heterogenous echogenecity of liver, either with blurred intrahepatic vessel margins or disappearance of minor intrahepatic vessels (Plate 3). The findings in the present study could be correlated to the findings of
Acorda et al., (1994); Braun (2009) and
Tharwat et al., (2012) who jointly opined that, heterogenicity and vascular blurring were due to coarsened liver parenchyma that occur due to infiltration of diffused micro fat droplets to macro-fatty bodies in liver.
B-mode ultrasonographic pattern in severe fatty liver
Deep attenuation was the major B-mode ultrasonographic finding in the present study (Plate 4). The findings of the present study were in agreement with the observations of
Acorda et al., (1994) and
Starke et al., (2010), who opined that deep attenuation to be a distinguished finding in severe fatty liver infiltration. These observations in the present study could be correlated with the panlobular distribution of macrovacuolar changes in hepatocytes, with alteration of the individual cells, as observed in the present study (Plate 5).
Liver biopsy
Buoyancy
In the present study, out of 75 clinical samples more than 88 per cent of samples from each category showed the floating or sinking properties in distilled water or copper sulfate solutions of 1.025 and 1.055 specific gravities when compared to the gold standard, histopathology and those were in agreement with the findings of
Gowri et al., (2013).
Histopathology
The biopsy samples of severe fatty liver cows showed a panlobular distribution of fat droplets indicated by higher percentage of macrovacuoles in the cytoplasm of almost all the hepatocytes altering the shape of hepatocytes and pushing the nucleus towards the periphery, giving an indication of cellular damage (Plate 5). This stage was in correlation with the increased levels of leakage enzymes such as AST. The histopathological findings of the present study were in correlation with the findings of
Bobe et al., (2004).
Spectral doppler study of portal vessel
Spectral doppler wave forms
In the present study, irregular and bizarre wave patterns, with irregular amplitudes and reduction in Vmax were recorded in various degrees of fatty infiltration (Plates 6- 9). Dampening of the wave with reduction in amplitude was the only consistent quality against the severity of fatty infiltration in liver. The change in the wave patterns in fatty liver cases in the present study could be attributed to the accumulation of fat in hepatocytes in fatty liver
(Orrego et al., 1981), loss of elasticity of portal vessel
(Johannsen et al., 1993), due to compression over the vasculature posed by the intra hepatic TAG accumulation
(Erdogmus et al., 2008), that led to the dampened wave forms
(Starke et al., 2011).
Grading of fatty liver based on the wave patterns was not possible as there was overlapping of the wave patterns between mild and moderate groups of fatty liver syndrome.
Spectral doppler derived indices
In the present study, a significant reduction in venous pulsatility index was recorded in clinical cases of fatty liver syndrome (Table 1) with an insignificant reduction in portal vessel blood flow volume (PBFV) which was in accordance with the findings of
Reynolds et al., (2003). The negative correlation recorded in the present study was in concurrence with the findings of
Starke et al., (2011).
The insignificant reduction in blood flow volume in the present study could be attributed to the increase in compensatory pressure as postulated by
Erdogmus et al., (2008).
Sensitivity and specificity of various diagnostic tests
In the present study the sensitivity and specificity of B-mode ultrasonography was found to be closer to histopathology when compared to the sensitivity and specificity of buoyancy and spectral doppler studies (Table 2).
The comparatively reduced sensitivity and specificity of spectral doppler wave in the present study, in comparison to B-mode ultrasonography was due to the non-specific changes in the wave pattern such as irregular amplitudes being shown in mild and moderate cases, insignificant reduction in the maximum velocity between the various clinical groups and lack specific waveform for a particular group as proposed by
Haudum et al., (2011). 
