VETERINARSKI ARHIV 68 (1), 1-9, 1998

Clinical experimental studies on acute rumen acidosis
in buffaloes (Bubalus bubalis L.).
IV. Influence of acidosis on blood, rumen liquid
and urine electrolytes

Yordan Nikolov*

Faculty of Veterinary Medicine, Stara Zagora, Bulgaria

* Contact address:
Prof. Dr. Yordan Nikolov,
Department of Internal Diseases and Clinical Toxicology, Faculty of Veterinary Medicine, Trachia University, 6000 Stara Zagora, Bulgaria,
Phone: 359 42 531 00; Fax: 359 42 741 25

ISSN 0372-5480
Printed in Croatia

NIKOLOV, Y.: Clinical experimental studies on acute rumen acidosis in buffaloes (Bubalus bubalis L.). IV. Influence of acidosis on blood, rumen liquid and urine electrolytes. Vet. arhiv 68, 1-9, 1998.

ABSTRACT

Experiments were carried out on buffalo-calves (Bubalus bubalis L.) in order to follow changes in body electrolytes. Blood, rumen liquid and urine were sampled for determination of dynamics of changes in total calcium, inorganic phosphate, magnesium, potassium, sodium, pH and urine specific gravity at hours -48, -24, and 0 before treatment, and at hours 2, 4, 6, 8, 24, 48, and 72 after treatment, respectively, with a single dose of beet molasses, 20 ml/kg body mass through an oesophagial tube immediately after the morning feed. Each litre of molasses contained 540 g saccharose. A decrease in rumen liquid, urine and blood pH was found, while inorganic phosphate concentrations were elevated in all liquids sampled; those of total calcium and magnesium were increased only in rumen liquid; sodium was elevated in blood but decreased in rumen liquid; potassium was decreased in both blood and rumen liquid. Urine specific gravity was increased.

Key words: buffalo-calves, Bubalus bubalis L., rumen acidosis, pH, blood, urine, rumen liquid, electrolytes

Introduction

Feeding ruminants with diets containing large amounts of easily digestible carbohydrates (beet, molasses, concentrates) was shown to result in metabolic disorders of forestomachs with impaired motor, secretory, chemical and microbiological functions (NIKOLOV and KUNEV, 1993; NIKOLOV and KUNEV, 1993a; NIKOLOV, 1996, 1996a). Fermentation products are lactic acid, histamine and other toxic elements (HUBER, 1971; NIKOLOV, 1995; NIKOLOV, 1996). Decreased rumen pH increased osmotic pressure inside the rumen and created the prerequisites for transport of liquids from circulation to rumen (HUBER, 1971; NIKOLOV and KUNEV, 1993; NIKOLOV and KUNEV, 1993a; NIKOLOV, 1995). This exchange of liquids inside the animal organism resulted in changes in concentrations of electrolytes in blood, urine and rumen liquid.

This motivated a study on those changes in order to complete our knowledge of the pathogenesis of lactic acidosis.

Materials and methods

Studies were performed on 10 buffalo-calves (Bubalus bubalis L.), divided into two groups: experimental (6) and control (4). Groups were of equal mean body mass (140 kg), age (4 months) and breed. Housing and feeding were also uniform. Before the study began the daily ration of all buffalo calves comprised 1.5 kg concentrate (forage for fattening of calves), 3 kg hay and 10 kg maize silage, split into two feeds (morning and evening), and with water ad libitum.

Acute ruminal acidosis was provoked with the per os administration of a single dose of beet molasses, 20 ml/kg body mass, through a gastric tube immediately after the morning feeding. Each litre of molasses contained 540 g saccharose. Blood, ruminal content and urine samples were obtained at hours -48, -24 and 0 before treatment, and at hours 2, 4, 6, 8, 12, 24, 48 and 72 after treatment, with a single dose of molasses for animals in the experimental group. Blood, rumen liquor and urine samples were subsequently drawn from each animal at various intervals and were analysed for various constituents as described below.

The pH of rumen liquor was determined with a pH-meter AP-17 (Hungary), blood pH by blood gas analyser ABL-3 (Radiometer, Denmark). The pH of urine was recorded using "HEPTAPHAN" pH paper strips of narrow range (Lachema, Czech Republic).

Inorganic phosphorous in rumen liquor, blood (serum) and urine samples was analysed using the methods (FISKE and SUBBAROW, 1925; CARACACHOV, 1980). Total calcium concentration in blood (serum) and rumen liquor was estimated using the methods (WEBSTER, 1962; IBRICHIMOV and LALOV, 1987). Magnesium in blood (serum) and rumen fluid was analysed as described by HENRY et al. (1974) and IBRICHIMOV and LALOV (1987). Sodium and potassium contents of the serum and rumen liquor were estimated with a flame photometer. Specific gravity of urine was determined by weighing a known quantity of urine and comparing its weight with the same volume of water. The qualitative examination of urine was carried out as described by COLES (1967) and CARACACHOV (1980). All results were statistically processed using the Student-Fisher test.

Results

It was determined that ruminal pH decreased as early as hour 4 after treatment (6.1 ± 0.1), followed by changes in blood and urine pH (Fig. 1). The latter were the lowest at hours 8 and 24 (5.0 ± 0.3 for ruminal liquid, 7.24 ± 0.04 for blood and 6.20 ± 0.4 for urine, respectively). They returned to initial values at hour 72. Inorganic phosphate (Fig. 2) was increased as early as the 2^nd post treatment hour (3.8 ± 0.1 mmol/l in blood; 5.19 ± 0.5 mmol/l in rumen liquor; 4.88 ± 0.6 mmol/l in urine). The highest values were observed post treatment at hour 24 for blood and rumen phosphates (6,62 ± 0.5 mmol/l and 7.13 ± 0.44 mmol/l, respectively) and at hour 48 for urine phosphates - 10.39 ± 1.1 mmol/l. This parameter did not return to its initial values in blood until about the 72^nd hour.

Changes in sodium concentrations (Fig. 3) showed a diverse pattern in the different liquids. Blood sodium was increased from the beginning up until hour 8 (177 ± 10 mmol/l) but aftwerwards decreased. Rumen sodium content decreased in the latter hours of the experiment (110 ± 9 mmol/l at post treatment at hour 72).

Fig. 1. Changes in pH levels of blood, rumen liquor and urine of buffalo calves with acute lactic acidosis (20 ml/kg body mass molasses)

Fig. 2. Changes in inorganic phosphorus levels in blood, rumen liquor and urine of buffalo calves with acute lactic acidosis (20 ml/kg body mass molasses)

Blood potassium was the lowest between post treatment at hours 8 and 24 (3.32±0.1 mmol/l) (Fig. 4). In rumen liquor it also decreased at hour 48 (13.5 ± 1.3 mmol/l). Blood and rumen fluid total calcium and magnesium concentrations varied - blood levels decreased, while rumen liquor levels increased (Figs. 5 and 6). Urine specific gravity (Table 1) increased from an initial value of 1.035 ± 0.1 to 1.068 ± 0.2 at the end of the study.

Fig. 3. Changes in sodium levels in blood and rumen liquor of buffalo calves with acute lactic acidosis (20 ml/kg body mass molasses)

Fig. 4. Changes in potassium levels in blood and rumen liquor of buffalo calves with acute lactic acidosis (20 ml/kg body mass molasses)

Fig. 5. Changes in calcium levels in blood and rumen liquor of buffalo calves with acute lactic acidosis (20 ml/kg body mass molasses)

Fig. 6. Changes in magnesium levels in blood and rumen liquor of buffalo calves with acute lactic acidosis (20 ml/kg body mass molasses)

Table 1. Changes in urine specific gravity levels (± SD) of buffalo calves with acute lactic acidosis (20 ml/kg body mass molasses)

^a=p<0.05; ^b=p<0.01

Discussion

The marked decrease in ruminal pH at the second hour after administration of easily digestible carbohydrates in rumen was attributed to their fast metabolism into volatile fatty acids (acetate, propionate, butyrate etc.) by lactic micro-organisms (HUBER, 1971; NIKOLOV and KUNEV, 1993; NIKOLOV and KUNEV, 1993a; NIKOLOV, 1996; NIKOLOV, 1996a). Part of them were neutralized by the saliva and the buffering capacity of rumen liquid, while a further part was resorbed in the circulation where the organism compensated the acidity via the acid-base balance - this was the reason why blood pH remained relatively stable up until hour 8. Subsequently, a decompensated metabolic acidosis developed up to hour 24, when another restoration of the balance followed (ANGELOV et al., 1995; ANGELOV et al., 1995a). The lacticemia reflected on the renal function via a decrease in urine pH. The decreased volume of urine and its increased density showed that it was concentrated secondary to dehydration and the impaired renal function (STANGASSINGER and GIESECKE, 1978; CHOUDHURI et al., 1980). Ruminal inorganic phosphorous concentrations showed a tendency towards elevation as early as after the 2^nd hour up to hour 24. Acute acidosis in buffaloes was accompanied by increased salivation, necessary for buffering the large amounts of lactate in the rumen. Rich in phosphates, saliva was responsible for the increased rumen inorganic phosphate concentrations (NOKATA et al., 1977). As early as the 2^nd post treatment hour significantly elevated blood inorganic phosphate levels were measured and which continued to increase up until hour 24. As lactate concentrations were the highest during that period (as suggested by blood pH) this increase in inorganic phosphate and sodium levels could be due to an increase in buffering capacity in order to maintain the acid base status of blood (ANGELOV et al., 1995; ANGELOV et al., 1995a). The present study indicated that the release of phosphates in urine in buffaloes with rumen acidosis was ten times greater that in healthy animals. This difference suggested that the renal threshold for phosphates could be even greater (REED et al., 1965; CHOUDHURI et al., 1980).

Sodium and potassium concentrations in rumen liquid did not significantly influence those cations in blood (TELLE and PRESTON, 1971). The decrease in sodium and potassium in the rumen could be explained by the dilution of ruminal content by the flow of fluids in rumen, thereby increasing its osmotic pressure (IVANOV, 1995; NIKOLOV, 1996). In acidotic animals, where salivation is intense, an increased flow of sodium in rumen should be expected (NOKATA et al., 1977). The general decrease in sodium concentrations evidenced that its content in saliva was obscured by the large flow on the part of vascular and extracellular pools.

The increased blood sodium could be caused by renal retention, thus explaining the low quantities in urine. Hydrogen ions were actively secreted from tubular cells in equal proportions to reabsorbed sodium ions (HUBER, 1971; IVANOV, 1995). In response to the increased sodium content, its reabsorption decreased, together with the secretion of hydrogen ions - a probable cause of increased acidity (IVANOV, 1995). The release of lactate contributed to urine pH decrease and for sodium retention (CHOUDHURI et al., 1980; IVANOV, 1995). Blood levels of potassium decreased during the period of the study. This could be attributed to its renal excretion in urine, where its concentrations were elevated as early as the 4^th hour after treatment. Moreover, the potassium ion was substituted by the reabsorbed sodium ion as a result of increased aldosterone activity (CHOUDHURI et al., 1980). The deficiency of potassium resulted in impaired coordination (ataxia) and hind limb paralysis in acidotic animals (TELLE and PRESTON, 1971). The insignificant decrease in blood magnesium was probably due to renal excretion (VAN'T KLOOSTER, 1969; HUBER, 1971; IVANOV, 1995).

Rumen liquor calcium increased during the first 8 hours, as well as magnesium content, up to hour 6 post treatment. The decrease of rumen pH increased the solubility of both calcium and magnesium (VAN'T KLOOSTER, 1969; HUBER, 1971; IVANOV, 1995). Decreased ruminal pH had a similar effect, leading to increased concentrations of those minerals. Their decrease after the 24^th hour was probably due to an increase in the volume of fluids with lower mineral concentration entering the rumen. The decrease in serum calcium at hours 8-24 could be attributed to the increased blood inorganic phosphorus concentrations (VAN'T KLOOSTER, 1969; HUBER, 1971).

Conclusions

The administration of 20 ml/kg body mass molasses in buffalo calves resulted in acute rumen acidosis, with rumen pH changing first, followed by urine pH and finally by blood pH.

Inorganic phosphorous values increased in all studied liquids and those of calcium and magnesium in ruminal content.

Blood sodium concentrations were increased, while in ruminal content it was shown to decrease.

Blood and rumen liquor potassium concentrations decreased.

Lactic acidosis resulted in dehydration with concentration of urine, thereby increasing its specific gravity.

References

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CARACACHOV, K. (1980): Clinical laboratory. Medicina. Sofia.

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COLES, E. M. (1967): Veterinary clinical pathology. W. B. Saundres Company. Philadelphia.

FISKE, C. H., Y. SUBBAROW (1925): The colorometric determination of phosphorus. J. Biol. Chem. 66, 375.

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Received: 16 April 1997
Accepted: 12 January 1998

NIKOLOV, Y.: Pokusna klinicka istrazivanja akutne acidoze buraga u bivola (Bubalus bubalis L.). IV. Utjecaj acidoze na krv, sadrzaj buraga i elektrolite mokrace. Vet. arhiv 68, 1-9, 1998.

SAZETAK

Radi pracenja promjena tjelesnih elektrolita izvedeni su pokusi na bivolskoj teladi (Bubalus bubalis L.). Melasa secerne repe u kolicini od 20 ml/kg tjelesne mase jednokratno je aplicirana teladi ezofagealnom sondom odmah nakon jutarnjeg hranjenja. Dinamika promjena u sveukupnom kalciju, anorganskom fosfatu, magneziju, kaliju, natriju, pH i specificnoj tezini mokrace odredena je u uzorcima krvi, sadrzaja buraga i mokrace uzetima 48, 24 i 0 sati prije, te 2, 4, 6, 8, 24, 48 i 72 sata poslije davanja melase. Svaka litra melase sadrzavala je 540 g saharoze. Ustanovljen je smanjeni pH buraznog sadrzaja, mokrace i krvi, dok je koncentracija anorganskog fosfata bila povecana u svim uzorcima. Koncentracija sveukupnog kalcija i magnezija bila je povecana samo u sadrzaju buraga. Koncentracija natrija povecala se u krvi, a smanjila u sadrzaju buraga. Kalij se povecao i u krvi i sadrzaju buraga, a povecana je bila i specificna tezina mokrace.

Kljucne rijeci: bivolska telad, Bubalus bubalis L., acidoza buraga, pH, krv, mokraca, sadrzaj buraga, elektroliti