VALUES OF SELECTED BIOCHEMICAL PARAMETERS OF COWS’ BLOOD DURING THEIR DRYING-OFF AND THE BEGINNING OF LACTATION

Robert Kupczyński, Bożena Chudoba-Drozdowska

ABSTRACT

The research aimed at determing the values of selected hematological and biochemical parameters of cows’ blood characterized by acid-base equilibrium during their drying-off and the beginning of lactation. Acid-base equilibrium (RKZ) parameters and the level of hematological parameters were determined, and in plasma the following were determined: total protein and its fractions, glucose, macro-elements: Ca, inorganic P, Mg, Na, K and Cl as well as the following enzyme activity: AspAT, AlAT, AP and GGTP. All analyses were conducted three times: 4 weeks before delivery, one week and 4 weeks after delivery. The obtained results indicate that the drying-off period and the beginning of lactation do not influence the level of acid-base equilibrium parameters and hematological parameters, however they do influence enzyme activity, particularly AP and GGTP, which increased during the beginning of the lactation period. The status of acid-base equilibrium, glucose and total protein content in blood plasma of cows may c

Key words: cows, acid-base equilibrium, metabolic profile, hematological and biochemical blood parameters.

INTRODUCTION

The increase of yield in herds of diary cows is usually a result of genetic progress, improvement of feeding quality and maintenance conditions [23, 31, 38, 39]. Mistakes in animals feeding may cause metabolic disorders, which, especially in case of high yielding cows, constitute serious hazard to their health state, fertility and milking yield [22, 30, 31, 32]. These ailments are usually present in a subclinical form and their highest frequency occurs during perinatal period and at the beginning of lactation. Their occurrence in high-in-calf cows is significant since in case of metabolic disorders placenta does not constitute a full protective barrier for fetus and, as a result, the calves are born weak, with low body mass, morphologic and functional changes of liver and often with diarrhea symptoms [3, 14, 18, 29, 40]. This kind of influence is described as alimentary toxicosis of maternal origin [29].

The diagnosis of this type of ailments is based on the whole set of diagnostic tests, including - as their important element - a determination of hematological and biochemical blood parameters constituting the metabolic profile. Diagnostic-preventive programs also include laboratory analyses of rumen contents, milk and urine as well as the analysis of feeding doses, and determination of parameters related to fertility [39]. Classic diagnostic methods include such programs as the test of metabolic profile according to Payne et al. [30], the check-up of physiologic state and purposeful therapy according to Sommer [37] or the diagnostic program of disorders in herds of cows according to Rutkowiak [31]. They serve for the detection of even subtle deviations from standard of the parameters in question, which allows for eliminating the hazard to animals’ health before the appearance of clinical symptoms, reproduction disorders and decrease of milking yield [31]. Reference values characteristic of specific cattle population should be adopted for the interpretation of metaphylactic tests results. Physiologic standards usually oscilate in a great range of values, and for this reason the comparison between them is of lesser diagnostic value, particularly in the course of disorders of a subclinical character.

This research aimed at determining the values of selected hematological and biochemical parameters of cows’ blood characterized by acid-base equilibrium during their drying-off and the beginning of lactation.

MATERIAL AND METHODS

The research was conducted on a dairy cow farm with 230 individuals. Considering their physiological state, 30 clinically healthy cows with acid-base equilibrium proved during monitoring tests were chosen for the research. These were animals of cb x hf breed, 4-6 years of age and similar body mass. They were kept in the same environmental conditions in alcoval system. Their feeding was based on whole-year mono-diet rules and PMR system of fodder giving. Feeding doses for cows on this farm were constructed according to the actual alimentary value of fodders, on the basis of chemical composition and recalculations, in accordance with the feeding system of ruminants INRA’88 [20]. The composition of feeding doses on the day of research beginning and completing were presented in Table 1.

One month before delivery (series I) the cows included in the research were subject to clinical evaluation and evaluation of their condition (BCS – body condition scoring) and classified on average at 3,5 points. Blood was taken in the morning from all animals from tail artery (arteria coccygea mediana), each time in the morning hours, in order to determine the level of acid-base equilibrium parameters (RKZ). After drawing, blood was cooled to the temperature of approx. 4 up to 6°C and transported to the laboratory. Within 2 to 4 hours from drawing, acid-base equilibrium was evaluated with Astrup method and the use of CORNING-464 apparatus, during which the following gasometric parameters were determined: pH, oxygen (pO₂) and carbon dioxide (pCO₂) pressure, current concentration of bicarbonates (HCO₃^–), base excess (BE), total content of carbon dioxide (CO₂T), percentage of hemoglobin saturation with oxygen (sO₂) and t he ratio of non-respiratory and respiratory component (HCO₃^–/pCO₂) was calculated.

Apart from that the following parameters were determined:

• hematological parameters: hematocrit (Ht), hemoglobin concentration (Hb), red and white blood cell count – with generally accepted methods, and erythrocyte parameters, i.e. mean red blood cell capacity (MCV), mean content of hemoglobin in the blood cell (MCH) and mean concentration of hemoglobin in the blood cell (MCHC) were calculated;

• biochemical parameters of blood plasma: total protein (Bc) with buret method and its fractions with agar-gel electrophoresis in CORMAY DIAGNOSTICS chamber with reading of fraction in DS.-2 (CORMAY) densitometer, glucose with enzymatic method using Analco reagents;

• activity of blood plasma enzymes: aspartate aminotransferase (AspAT) and alanine aminotransferase (AlAT) by kinetic method with NADH and tris buffer, alkaline phosphatase (AP) by kinetic method with p-nitrophenylphosphate and diethylamine buffer (DEA) and g-glutamyltranspeptidase (GGT) by kinetic method with g-glutamyl-p-nitroanilide and glycide aminoacetic acid. The activity of all enzymes was determined at 37°C using bioMerieux reagents;

• macro-element content in blood plasma: Ca, inorganic P and magnesium by calorimetric method with UV-VIS (bioMerieux) spectrophotometer and ALPHA Diagnostics reagents as well as Na, K and Cl using ion-selective electrodes (ISE) and EasyEyte apparatus.

All blood analyses were conducted again during the following periods: postnatal, i.e. about 7 days after delivery (series II) and 4 weeks after delivery (series III).

Also, production parameters were analyzed and milking yield (improved one and FCM yield) was evaluated during lactation preceding the research as well as during next lactation.

The results were subject to statistic analysis with Statgraphics ver. 5.0 statistic program considering mean standard deviations and significance of differences between the research series with Duncan test.

RESULTS AND DISCUSSION

On the first day of research, i.e. 4 weeks before delivery was due, acid-base equilibrium or slight alkalosis, which are characteristic of the adult ruminants, were found in the examined cows [13, 18, 42]. Mean values of partial carbon dioxide (pCO₂) were 5.33 kPa, concentration of bicarbonates (HCO₃^–) – 26.3 mmol/l while base excess (BE) was 2.3 mmol/l, which resulted in blood pH of 7.443 and the ratio of non-respiratory and respiratory component (HCO₃^–/pCO₂) of 22.22. The acid-base equilibrium continued to remain during series II of the research, that is one week after delivery. Statistically highly significant increase of pCO₂ was found up to 5.92 kPa with accompanying compensative increase of HCO₃^– up to 28.7 mmol/l and BE up to 4.3 mmol/l, which in consequence gave a normative ration of HCO₃^–/pCO₂ and blood pH of 7.436. In series III of the research partic ular gasometric parameters reached a result close to series I, resulting from the decrease of pCO₂ (to 5.36 kPa) and increase of non-respiratory component as well as HCO₃^– concentration and BE (Table 2). The relatively high stability of RKZ system parameters probably resulted from the fodder used in PMR system and the choice of components of feeding dose based on their actual alimentary value. The advantages of INRA’88 feeding system, especially in case of high-yielding cows have already been found, among others by Strzetelski [38].

Our own research confirmed the fact noted by other authors [3, 6, 13, 18] that adult clinically healthy cows retain acid-base equilibrium or slight alkalosis, which to a great extent results from the kind of consumed fodder as well as individual characteristics.

The values of hematological parameters in cows in our own research fluctuated slightly without showing any apparent relation to the physiologic state of the animals or level of RKZ parameters (Table 3). During particular examination series they were within the range of normative values [26, 42].

Hematological tests of cattle are used as the so-called screening examination or in order to establish initial diagnosis, therefore they are often taken into account in diagnostic profiles [5]. In specialist literature one can encounter tests suggesting that red and white blood cell count as well as hemoglobin concentration do not show great seasonal differences, and do not depend on the cows’ physiologic state [7, 33]. Other examinations [21] indicate that during the last period of pregnancy such parameters as hematocrit value and erythrocyte count decrease physiologically while increasing after delivery. Kuleta et al. [22] proved other relationships finding a downward tendency of hematological parameter values in cows during the period of 2 weeks before up to 2 months after delivery. These variations, however, do not hinder the clinical evaluation of test results since they remain within the limits adopted as normative ones [5, 26, 42].

There is no univocal information in the available literature [21, 29, 36] regarding the influence of acid-base equilibrium on the level of hematological parameters. Nicpoń and Jonkisz [29] did not find significant changes of their levels either in cows with acidosis or alkalosis. However, during experimental acidosis the increase of erythrocyte count and hematocrit level were observed, but after its regression a fast decrease of their levels occurred, even in relation to the initial state [12]. Respiratory alkalosis as well as respiratory acidosis result in the increase of leukocyte count in cows’ blood according to Skrzypek et al. [36].

The mean content of glucose in cows’ blood plasma on the day of research beginning was relatively high – 3.40 mmol/l – reaching the upper limits of normal values [26, 42]. Statistically highly significant (pŁ0.01) decrease of its level occurred during the research period (Table 4), but in spite of this the values determined in series II and III of the research still remained within normal range [26, 42]. Many authors [8, 25] noticed similar decrease of glucose level at the beginning of lactation as the one found in our own experiment. Glucose content in blood constitutes the evidence of organism supply with energetic compounds [10, 21, 37], while the energy level in the feeding dose as well as the relation of protein to energy influence its content in blood [28, 33]. A decrease of glucose content in blood occurs in the course of energetic disorders in cows [9, 21], but also during respiratory acidosis [36].

The mean content of total protein in blood plasma of the examined cows during series I of the research was 76.8 g/l, and thus reached the upper limits of values presented as normative ones [26]. During the research period no significant changes in total protein concentration were found apart from its slight decrease in series II. Similar tendencies were observed with regard to particular protein fractions (Table 4), and their levels reached the upper limits of the values presented as normal ones [26, 42].

The total protein content in blood plasma is one of the indications of nitrogen metabolism in the organism, and depends on the protein content in fodder [23, 38], lactation stage [8, 25], age of cows [8] and season of the year [4]. The decrease of total protein level in blood plasma in case of cows after calving may result from the transition of albumins and g-globulins from blood to udder. Similarly as in our research, other authors observed a decrease of total protein content in cows’ blood plasma during this physiologic period [19, 21, 22, 23]. The total protein level in blood plasma may serve as an indirect exponent of the animal’s feeding state [8], however, it shows a considerable individual variation, reaching 10-20 g/l [4].

The mean activity of indicative enzymes, AspAT and AlAT, in cows’ blood plasma on the day of the research beginning remained within the limits of normal values [26, 42], showing upward tendencies during the following research series (Table 5). This increase in case of AspAT was statistically significant (pŁ0.05). The changes of transaminase activity are related to the physiologic state, and their increase was observed e.g. in cows after delivery [2, 19, 22, 25]. As stated by Saba et al. [33], higher levels of AspAT and AlAT in cows after delivery are related to higher metabolic effort caused by lactation, while in cows with a pathologic course of postnatal period they result from damage to the organs of the reproductive system. Nicpoń and Jonkisz [29] found the increase of transaminase levels during acidosis and alkalosis resulting from damage to parenchymatic organs, however, as Lechowski [24] believes, the changes of AlAT activity do not al low for determining the character, extent and reversibility of hepatic changes. The increase of these enzymes activity also accompanies disorders of energetic metabolism [9, 21].

The mean AP activity during series I of the research was relatively high (87.4 I/l) and remained at the upper limits of normal values [26, 42]. During the following research series – i.e. 7 days after delivery – there occurred its statistically significant (pŁ0.05) increase up to 110.6 U/l, and then, during the last series, a decrease of AP activity was observed, to 96.7 U/l. AP activity observed during series II of the research was higher than the one presented by Meyer and Harvey [26] as a normative one. Kwiatkowski et al. [23] found a similar AP activity increase in cows after delivery as in our research, however there are many others who observed a high activity of this enzyme during the drying-off period. Saba and Bis-Wencel [34] are of the opinion that the increasing AP activity results from Ca and P metabolism disorders. AP activity increase also occurs in cows as a result of liver damage in the course of acidosis [24, 29] as well as alkalosis [14, 29]. In case of calves originating from cows with metabolic alkalosis its activity increase proves ossification disorders [29].

The mean GGT activity systematically increased during the whole research period reaching a relatively high value of 35.9 U/l in the last series (Table 5). The increase was statistically significant (pŁ0.01). In spite of these tendencies the values presented as normal ones were not exceeded [26, 42]. GGT activity is characterized by high hepatic specificity, and its increase in blood plasma reflects the degree of this organ steatosis [2]. AP and GGT activity increase in cows found in our research is a proof of metabolism intensification in liver during the postnatal period, with the determined values considerably exceeding a broad range of physiologic fluctuations in case of some animals [26, 42]. GGT activity increase in high yielding cows intensifies during postnatal period and at the peak of lactation [19]. Filar [9] thinks that at GGT activity increase up to the value of over 30 U/l there occurs hepatic structures damage. Higher than two-f old increase of this enzyme activity in cows after delivery indicates a cellular structure damage of hepatocytes according to Bronicki and Dembiński [2]. In case of cows with acidosis the enzyme activity increases [24], which might be the evidence of adipose hepatic degeneration [19, 24].

Calcium and inorganic phosphor levels in cows’ blood plasma quoted by various authors [26, 42] fluctuate within a broad range. In our research the mean content of calcium and inorganic phosphor in case of dried-off cows reached a bottom limit of normative values [26], while their significant decrease was observed one week after delivery (Table 6). These are symptoms of moderate hypocalcemia and hypofosfatemia, which is confirmed by the fact of three cases of cows’ postnatal retention requiring doctor’s intervention. A slight decrease of calcium and inorganic phosphor content in blood plasma of the cows after delivery is considered as a physiological state [25, 42]. During the last series of research we found an increase of the examined macro-elements content in cows’ blood plasma up to the bottom limits of normative values [26, 42].

Hypomagnesemia in high-in-calf cows is related to the risk of postnatal paralysis [16], which confirms the above quoted observations. The mean magnesium concentration in cows’ blood plasma decreased slightly during the research period and remained at the bottom levels regarded as normal ones [26, 42].

The mean values of sodium, potassium and chloride in the animals’ blood plasma also remained within the limits of values recognized as normative ones [26, 42], and did not show any significant changes, apart from the decrease of chloride content during the last research series (table 6). The obtained results are not indicative of the occurrence of electrolyte metabolism disorders in the examined cows.

An optimal level of calcium as well as inorganic phosphor in blood plasma is not equivalent with its proper quantity in the organism or with its content in the feeding dose [1, 17, 32]. These macro-elements, and particularly calcium, are subject to hormonal regulation [1, 10, 17]. An obvious hypocalcemia in cows occurs with postnatal paralysis (paresis puerperalis) [1, 10, 16]; a drop of ionized calcium in blood plasma is attributed an important role in its pathogenesis, while the ionization degree depends to a large extent on acid-base equilibrium [1, 17, 35]. Numerous investigations [11, 16, 35, 41] were devoted to the influence of anion-cation balance in the fodder (DCAB) on RKZ status in cows. It was found that their organism is acidified when absorptive anions prevail in the fodder or it is alkalized when cations prevail. It was also found that feeding doses with an addition of anions (anionic salts) efficiently decrease the risk of postnatal paralysis occurrence [10, 11, 27]. Ionized Ca content increases when DCAB value of the diet decreases [27], while too high quantity of potassium in the fodder promotes the occurrence of postnatal paralysis through its alkalizing effects, and thus a decrease of calcium homeostasis mechanism efficiency [11, 16]. Schneider et al. [35] state that the addition of potassium chloride and sodium chloride as the source of anions has no alkalizing influence, since a high potassium content in the diet is balanced by its excretion with urine.

The mean milking yield during the period preceding the research, recalculated into 305-day lactation and FCM yield were lower (431 kg and 500.1 kg respectively) than during the next lactation, which might have resulted from the age of the examined cows (Fig. 1). Hibner et al.’s [15] research showed that cows of white and black breed reach their maximal milking yield in 3^rd-5^th lactation.

CONCLUSIONS

1. The drying-off period as well as the beginning lactation did not influence acid-base equilibrium and hematological parameters showing no relation to the physiological state of the cows.

2. The formation of acid-base parameters, glucose and total protein content in cows’ blood plasma during the research period indicates a correct energy-protein balance of their feeding dose, while the levels of calcium, inorganic phosphor and magnesium remained at the bottom limits of standards.

3. The mean activity of the examined enzymes depended on the physiologic state of the animals, and was the highest during the beginning of lactation, particularly that of AP and GGTP, indicating subclinical disorders of hepatic function.

4. The levels of RKZ parameters, hematological parameters, glucose, total protein and its fractions as well as Na, K and Cl found in our research can be adopted as reference values for cows with a high milking yield.

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