Research Article - (2013) Volume 3, Issue 1
1Department of Clinical Science, Faculty of Veterinary Medicine, Tabriz Branch, Islamic Azad University, Tabriz, Iran
2Department of Veterinary Medicine, Faculty of Veterinary Medicine, Tabriz Branch, Islamic Azad University, Tabriz, Iran
Fatty liver syndrome (Hepatic lipidosis) or fat cow syndrome is a major metabolic disorder in many dairy cattle's in early period of lactation. The aim of this study was to evaluating fatty liver syndrome in dairy cattle in Tabriz by measurement of NEFA, LDH and BHBA serum values. In this inspection, age, body condition score and Pregnancy status of animals was investigated. Simultaneous inspection of animals, attempting to obtain blood samples of 10 ml of jugular vein was done by venoject. Blood samples taken near the ice and sent to the laboratory and after serum preparation were freezing inside the micro tube. At the time of testing, sera were defrosted and NEFA levels in serum by Randox kit and Auto analyzer were measured. In this study, levels of LDH and BHBA were measured by Pars test kits and by spectrophotometric method. Results showed that based on pearson's Correlation index there is a direct correlation between NEFA and LDH and BHBA serum values. This index indicates a direct effect of NEFA on LDH and BHBA serum values. Thus, with elevating of NEFA serum values, the LDH and BHBA values also increased.
fatty liver, dairy cattle, NEFA, LDH, BHBA
Fatty liver syndrome (Hepatic lipidosis) or fat cow syndrome is a major metabolic disorder in many dairy cattle's in early period of lactation [1,2] and it's combined with decrease in health and reproduction rate of livestock [3,4]. Fatty liver syndrome was documented in forties (decade 1940) but there were few researches about it until midseventies. In early 70 and 80 decades, this syndrome was reported around parturition widely and it was recorded in many countries [1,2]. When this disorder is severe, milk production and appetite of cow, both are decreased. So effective prevention of fatty liver can save millions of dollars every year and prevent from decrease in milk production [5]. Incidence of Fatty liver in dairy cattle is mainly in first four weeks after parturition [6], when more than 50% of cows show different degrees of Triacylglycerol (TAG) accumulation in their livers [4,7]. One of the reasons is that daily nutrition of cow is not sufficient and it can't meet increasing need of energy in cattle that is producing milk. In this condition, none Esterified fatty acid (NEFA) is released from adipose tissue, often more than it's needed, and extra amount is transferred to liver, especially in fat cows [8]. Fatty liver occurs when liver harvesting of lipids is more than their Oxidation and secretion by the liver and it is with high plasma concentrations of NEFA that is resulted from high adipose tissue [5,6]. Extra fat is stored in liver as TAG and results in decrease of metabolic function of liver [5]. Liver is classified to three types, according to fat level: normal liver, liver with average fat and liver with very high fat [5,6]. The latter type is categorized to Non-encephalopathic fatty liver [9] and hepatic encephalopathy [5,6]. Unbalanced or insufficient nutrition, overweight and high concentration of estrogen are involved in etiology of fatty liver [3]. The disorder can be accompanied with high rate of dystocia, infectious and inflammatory disease, long interval between parturitions and reduction of milk and longevity average [3]. Forasmuch as even slight fatty liver is dual with decrease in health and reproduction status of cow, prevention of its occurrence with supplying enough food and creating an isolated place at preparation period for parturition can reduce decline rate of producing milk and it would be the most efficient therapeutic procedure among the other methods [10]. However this prevention is not enough for fat cows or the ones that are not feed well, the cows that have problem during parturition or had twins, the cows that have metabolic or infectious disease and the ones that have developed severe energy imbalance because of producing high amount of milk immediately after parturition [10]. Assuming existence of about 9 million dairy cattle all over the America, annual charges of fatty liver in this country is estimated more than 60 million dollars [9]. If there are more studies about molecular changes and relationship between the disease and immunity function, better remedies and more efficient ways to prevent fatty liver can be presented [11]. In our country, because of industrial methods that speed for nurture and maintenance of dairy cattle, and because of producing more milk, more nutrition is considered; occurrence of this syndrome is most likely. According to these conditions, providing exact diagnose of this syndrome and estimate it's incidence rate and finally how to prevent it in our country is a necessity and this case made us do the first study about this disease in Tabriz. It's possible that origin of many diseases happening around parturition could be fatty liver incidence in this region's dairy cattle.
This research is descriptive – analytical. In this quest, during frequently visits from dairy cattle farms of Tabriz, according to statistics of dairy cattle in Tabriz area, the inspection of 120 Holstein cows were done. In this inspection, age, body condition score and Pregnancy status of animals was investigated [12]. In next stage, according achieved results; Cows were divided into 3 groups; cows of group 1 were pregnant, cows of group 2 were those that less than 1 month has been last from their calving and cows of group 3 were those that more than 1 month has been last from their calving. Simultaneous inspection of animals, attempting to obtain blood samples of 10 ml of jugular vein was done by venoject. Blood samples taken near the ice and sent to the laboratory and after serum preparation were freezing inside the micro tube. At the time of testing, sera were defrosted and NEFA levels in serum by Randox kit and Auto analyzer were measured. In this study, levels of LDH and BHBA were measured by Pars test kits and by spectrophotometric method. In this study to analyzing and comparison of data were used of ANOVA test and to evaluate the relationship between the variables together, correlation test was used.
NEFA serum value
Based on table 1 and ANOVA test results, NEFA serum value in group 1 was 844.87±104.07, in group 2 was 715.55±151.59, and in group 3 was 686.62±143.50 that there is significant difference (P<0.001) between groups.
Table 1: Mean serum NEFA in Holstein dairy cows based on pregnancy status
BHBA serum value
Based on table 2 and ANOVA test results, BHBA serum value in group 1 was 8.25±1.57, in group 2 was 6.45±1.24, and in group 3 was 6.78±1.44 that there is significant difference (P<0.001) between groups.
Table 2: Mean serum BHBA in Holstein dairy cows based on pregnancy status
LDH serum value
Based on table 3 and ANOVA test results, LDH serum value in group 1 was 874.87±255.59, in group 2 was 764.62±215.84, and in group 3 was 779.32±197.60 that there is no significant difference (P>0.05) between groups.
Table 3: Mean serum LDH in Holstein dairy cows based on pregnancy status
Relationship between NEFA and BHBA
Based on table 4 and pearson's Correlation index revealed that there is a direct correlation between NEFA and BHBA serum values so that correlation index was r=0.680. This index indicates a direct effect of NEFA on BHBA serum values. Thus, with elevating of NEFA serum values, the BHBA values also increased.
Table 4: correlation index between NEFA and BHBA serum values
Relationship between NEFA and LDH
Based on table 5 and pearson's Correlation index revealed that there is a direct correlation between NEFA and LDH serum values so that correlation index was r= 0.617. This index indicates a direct effect of NEFA on LDH serum values. Thus, with elevating of NEFA serum values, the LDH values also increased.
Table 5: correlation index between NEFA and LDH serum values
Dairy cows during the transition period (3 wk before and 3 wk after parturition) are at high risk for different metabolic disorders, including fatty liver [5]. Prevalence of fatty liver in dairy cows can be as high as 50% [7]. Consequences of fatty liver include decreased reproductive success [7] and suppressed immune functions [13]. Fatty liver usually does not develop alone and can be associated with other periparturient diseases such as ketosis, retained fetal membranes, endometritis, displaced abomasum, mastitis, and milk fever [14,15]. Fatty liver commonly is believed to be a prerequisite for development of ketosis [6,14,16]. Prevention of ketosis and other metabolic disorders is very important, because these disorders cause substantial economic losses to dairy farmers [9,17]. Transition dairy cows are in negative energy balance, because they cannot meet nutrient requirements for maintenance, fetal growth, and milk production from feed consumption [18,19]. At the onset of lactation, the mammary gland has greatly increased demands for glucose, which is used primarily for lactose biosynthesis, and acetate, which is used for milk fat synthesis. To meet nutrient and energy requirements, cows repartition glucose and mobilize fatty acids from adipose tissue, which result in elevated blood concentrations of NEFA [5,6,18]. Excess blood NEFA are taken up by the liver and metabolized in different ways. Nonesterified fatty acids can be oxidized completely to carbon dioxide or incompletely to ketone bodies, esterified into triacylglycerol (TAG) for storage in the liver, or secreted into blood as a part of very low density lipoproteins. When rates of NEFA esterification for storage as TAG exceed the rates of NEFA disposal, fatty liver can develop. Exact causes of fatty liver are unknown; however, any factor that causes increased lipid mobilization from adipose tissue might be responsible.
For awareness of fatty liver syndrome, blood biochemical parameters can be used or we can measure TAG and total fat of hepatic cell. Some researchers inspect fatty liver based on TAB or hepatic fat percent [10]. Raid (1980) divided livers in 4 levels depending on severity of fat accumulation in it: Normal, slight, average and severe [20]. Nowadays general opinion is that a high percent of mature cows show signs of slight or severe fatty liver around parturition [5,21]. Almost near parturition NEFA increases in blood and moves to liver, and can cause ketosis, abomasums displacement, metritis and fatty liver after parturition [5,22,23]. In a normal situation and positive energy balance, NEFA value is about 200 meq/lit in blood. This value increases since 3 weeks is parturition and reaches to 300 meq/lit in the last week. In the last days before parturition, it reaches to 800 -1200mcq/lit. After parturition these acids should wane immediately and if it remains more than 700meq/lit after 7 days, represents negative energy balance and probability of fatty liver incidence. 3 weeks after parturition the amount of these acids should return to normal level (200meq/lit) [22]. Also the results of this study have conformity with Grummer results that showed three is most lipid aggregation in liver in first 4 weeks after parturition [6]. There was a research in Netherlands about 71 dairy cattle before parturition that showed 5 percent of liver is occupied with TAG [24]. Also in a slaughterhouse research in Tehran, aggregation of TAG more than 10% in liver in last month of pregnancy was reported. These researchers had not measured NEFA values. In this study, TAG aggregation in liver in last month of pregnancy had occupied more than 5% of liver cells and amount of NEFA was more than 900meq/lit being nonspecific and some other reasons. Slight and Mild forms of fatty liver con destroy hepatocytes and disturb liver function without making any changes in activity of hepatic specific enzymes found in serum. Measurement of liver enzymes in serum is useful for evaluating fatty liver disease but with certain restrictions such as is being nonspecific. Mild and moderate forms of fatty liver with damaged hepatocytes can cause liver and no specific changes in liver enzymes in serum, liver dysfunction to establish [25,26].
