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Physiological Comparison of Some Serum Biochemistry between Lactating and Non-Lactating Dairy Cows in Selected Dairy Farms of Dhaka District of Bangladesh

The present study was carried out to investigate the physiological comparison of some serum biochemistry between lactating and non-lactating dairy cows in selected dairy farms of Dhaka district of Bangladesh. The aim of the current study was to evaluate the serum parameters like glucose, total protein, total cholesterol, calcium and phosphorus concentration and these parameters were measured by the serum analyzer for lactating (n=50) and non-lactating (n=50) dairy cattle which were selected from various selected dairy farms of Dhaka district. The results (mean ± standard deviation) of the study showed that among the serum biochemical parameters total protein (84.2±1.18 gm/l) and total cholesterol (156.36± 3.41 mg/dl) level in non-lactating cows were higher than the value of lactating cows as (80.14±2.31 gm/l) and (138.21± 1.21 mg/dl). On the other hand, serum glucose, calcium and phosphorus level in lactating cows (68.12± 2.34 mg/dl), (12.06±3.21 mg/dl) and (8.30±0.20 mg/dl) respectively were found higher than the non-lactating cows (60.32 ±1.42 mg/dl), (10.48±5.60 mg/dl) and (6.31 ±0.12 mg/dl). In case of parity-wise biochemical parameters were insignificant variation was found. It may be concluded that biochemical parameters variation present between lactating cow and non-lactating cow is important for interpretation of laboratory data and also for physiological diagnosis.


INTRODUCTION
Blood biochemical attributes are important indicators of the metabolic activity in lactating animals (Karapehlivan et al., 2007). During lactation, secretary cells of mammary gland utilize 80% of the blood circulating metabolites for milk synthesis, depending on the speed of infiltration of precursors of milk compounds (i.e. free amino acids, glucose and fatty acids). All animals require minerals such as calcium (Ca), magnesium (Mg) and phosphorus (P) for growth, reproduction and lactation which often affect specific requirements and serve as catalytic components of enzymes or regulate several mechanism involved just in pregnancy and lactation (Tanritanir et al., 2009 andSamardzija et al., 2011). Especially at the beginning of lactation, mobilization of Ca from bone and increased absorption from the gastrointestinal tract are required to re-establish homeostasis which have to react to a tremendous increase in demand for Ca (Liesegang, 2008 andLohrenz et al., 2010). Milk, the outcome of various biochemical activities in mammary secretary cell is composed of fat, protein, carbohydrates, enzymes, vitamins and various minerals. The composition of milk is influenced by various factors, i.e., stage of lactation, lactation number, breed, feeding pattern, environmental and diseased condition of the udder (Brinez et al., 2003). The fat, protein and urea contents of milk vary according to stage of lactation. Fat content is high immediately after calving but soon begins to fall and continues to do so for 10 to 12 weeks, after which it tends to rise again until the end of the lactation (Chilliard et al., 2003(Chilliard et al., , 2007. Approximately, 400 to 500 liters of blood circulate through mammary gland to produce one liter of milk (Fernandez and Hoeffler, 1998). There is a 2 to 6 folds increase in blood flow in the mammary gland starting 2 to 3 days prepartum. During lactation, the mammary gland secretory cells utilize 80% of the blood metabolites for milk synthesis depending on the infiltration of precursors of milk components like amino acids, glucose and fatty acids (Piccione et al., 2009). Hence, blood biochemical parameters including total protein, triglycerides, free fatty acids and urea are important indicators of the metabolic activity in lactating animals (Karapehlivan et al., 2007). Since the milk yield and composition varies across the length of lactation stage, it is, therefore, imperative, to study haemato-biochemical constituents during different stages i.e. early, mid and late stage of lactation. Although some variation has also been observed in the hematological parameters between breeds of farm animals (Tambuwal et al., 2002), in this regard, it may be difficult to formulate a universal blood

Experimental population:
The experimental population was 100 cross bred (HF × Local) healthy cows. In the farms, cows were in different age and production status, from which 50 lactating and 50 non lactating (dry) cows were selected based on parturition record for the first time, but not exceed for more than three times. Cows were further grouped into three categories on the basis of calving history (parity) of which parity-1 (n=35), parity-2 (n=35) and parity-3 (n=30). Some of the dry cows were pregnant, but they were not grouped further. All animals were fed both roughage and concentrates. Normal feeding habits of animals were observed during the research activities. All animals involved in this study were clinically healthy and to ensure this clinical history was reviewed with the farm manager through the examination of physical condition.

Sample collection and processing:
All blood samples were collected between 10 am to 12 pm in order to standardize time. Blood samples were taken from jugular vein puncture with proper aseptic measures. About 5 ml of blood was collected and kept in the vacationer tube without anticoagulant. The samples were transported to the Physiology laboratory under the Department of Veterinary and Animal Sciences at Gono University, Savar, Dhaka, Bangladesh for analysis. After coagulation, coagulated blood was centrifuged in 3000 RPM for 15 minutes. Serum was transferred to the Eppendorf tube by using micropipette. The obtained serum samples were stored in -20 0 C for biochemical test in glucose, total protein, total cholesterol, calcium and phosphorus of blood serum were determined according to the biochemical analyzer manual (Humalyzer 3000, Germany R).

Statistical analysis:
Obtained laboratory data was stored in Microsoft Excell-2010 and imported to the software STAT/IC-13.0 for analysis. Descriptive statistical analysis was done to measure the mean, SEM, 95% confidence interval (CI) and p value of different parameters. The arithmetic means (±SE) serum biochemical parameters in different groups were calculated. In all cases the level of significance was determined at p<0.05).

RESULTS AND DISCUSSION
Findings for serum glucose, calcium and phosphorus level were within the reference range and their variations were insignificant (Table 1). Total protein levels in both lactating and dry cow were higher than the reference value, but the variation was insignificant between the lactating and dry group of cows. Serum cholesterol level was found lower in both groups than the standard value and variation between the groups was highly significant. The glucose level in lactating cows (68.12± 2.34 mg/dl) was higher than the non-lactating cows (60.32 ±1.42 mg/dl) that differ insignificantly. Peterson et al., (1981) reported that glucose was higher in dry cows (69.8±3.7 mg/dl) than lactating cows (65.2±1.7 mg/dl). The blood glucose level is regarded as one of the indicators of energy status in the cow. The blood glucose level was higher in lactating cows this may be due to high energy diet feeding during lactation period and also for taking the extra amount of feed than the requirement of animal for milk production and maintenances. Other research by Cozziet al., (2011) in Holstein dairy cows reviled 58±0.40 mg/dl. In a yearlong study of five upazilla namely Savar, Damray, Tongi, Shakhipur and Gazipur sadar of Bangladesh serum glucose level was found (69.21±2.31 mg/dl) in indigenous cattle (Hasan et al., 2013). Total protein in serum in lactating and non-lactating cows were (80.14±2.31 gm/l) and (84.2±1.18 gm/l) respectively. The results of the current study were similar with Peterson et al., (1981) where total protein levels were reported to be higher in non-lactating cows (90.23±0.23 gm/l) than lactating cows (70.73±0.09 gm/l). Conversely, the total serum protein in lactation period (60.32±0.60 gm/l) was slightly higher than the dry period (60.17±0.89 gm/l) reported by Giuseppe et al., (2012). Serum total protein value in mixed race of Austrian Bălţat with Red Holstein and Red Holstein metis was found (80.50±0.70 gm/l) (Mateiet al., 2010). Again, 49.08±8.16 g/l value was found from twenty pregnant Freizian cows in Saudi Arabia (Al-Mujalli, 2008). In another study, the value of total protein in Holstein dairy cows was mentioned 82±6.10 g/l by Cozziet al., (2011). Manzooret al., (2008) stated that, biochemical parameter of blood serum was higher in non-lactating cow than in lactating cows. There is a general modification in animals in serum proteins with advancing age and in the very old cows (Kaneko et al., 1997). Total cholesterol in non-lactating cows (156.36± 3.41 mg/dl) was higher than the lactating cows (138.21± 1.21 mg/dl) with significant variation. Similarly Peterson et al., (1981) reported that total cholesterol was higher in dry cows (130.97±0.14 mg/dl) than lactating (120.87±0.06 mg/dl). In contrast total cholesterol value was found higher in lactating than non-lactating cows (Giuseppe et al., 2012). Serum total cholesterol parameter in mixed race with Austrian Blatt with Red Holstein and Red Holstein metis was found (138.50±0.20 mg/dl) (Mateiet al., 2010). In another study the overall mean value of total cholesterol was found (145.13±6.33 mg/dl) from twenty pregnant Friesian cows in Saudi Arabia (Al-Mujalli, 2008). In addition total cholesterol reference value (137±2.50 mg/dl) was reported by Cozziet al., (2011) in the Holstein dairy cows. Higher fat rich feed intake is responsible for higher cholesterol concentration in blood serum. Lower serum total cholesterol level in lactating cow is related to higher milk production of animal and depletion of cholesterol for maintaining milk production. The concentration of total cholesterol was influenced not only by the physiological condition of the animal, but also by nutrition (Kaneko et al., 1997). According to parity, total protein level were found elevated than the reference value and the insignificant variation were shown among the different parity where lowest value was found in the third parity followed by first and second parity. On the other hand alike serum protein the serum cholesterol level was found lower in all three parities in which lowest value was found in parity two followed by parity three and parity one even though there variations were insignificant. However the serum glucose level was found in decreasing trend with insignificant variation in relation to parity proceed. Serum calcium and phosphorus level were followed almost similar trends and found higher at second parity (Table 2). Within parity 1 serum total protein, total cholesterol and phosphorus level were higher in the non-lactating cows than the lactating whereas in parity 2 cholesterol and glucose level was higher in non-lactating cows. Conversely, in the case of third parity total protein, glucose, calcium and phosphorus level were found higher in lactating cows in comparison to the non-lactating cows. Overall variation within the parity were insignificant (p>0.05) ( Table 3).