**3.5 Gamma Glutamyl Transferase (GGT)**

The highest activity of GGT is in bile ducts epithelium and in kidney. The enzyme is located in membrane structures of the cells. The increased serum activity of GGT is usually associated with cholestasis and bile ducts damage. Very high activity of GGT is also in colostrum of cattle, sheep and goats. Hammon and Blum (1998) measured in colostrum of cows mean activity of GGT 22.432 U/L. After colostrum intake the enzyme is absorbed through intestinal wall, consequently the GGT activity is very increased in this period and can be used for indirect estimation of colostrum supply (Bostedt, 1983). The GGT activity in newborn calves was 10-31 U/L, after colostrum intake it increased to 370-5000 U/L, then it slowly decreased to the age of 20 days when it stabilised (Braun et al., 1982). In calves which received only milk or milk replacer instead of colostrum, the GGT activity did not increase (Boediker, 1991). In the first week of life GGT activity was high later it decreased rapidly (Knowles et al., 2000; Egli & Blum, 1998). The GGT activity below 100 U/L at the age of 2 days indicates insufficient colostrum supply or disturbed absorption (Klee, 1985). Tyler et al. (1999b) claimed that activity of GGT above 50 U/L in the calves serum indicate sufficient colostrum supply, Perino et al. (1993) stated 200 U/L for the boundary value.

By comparison of various data from the literature in some cases considerable differences in the activity of enzymes were established. There are also considerable differences between

Values of Blood Variables in Calves 307

the organism and is controlled by iron amount in the intestine mucosa. The majority of iron is absorbed in the duodenum. The absorption is more efficient in animals with iron deficiency (Underwood & Suttle, 2001). The iron is very important for synthesis of haemoglobin. Approximately 60-75% of iron in the body is bound to haemoglobin (Kraft, 1999a). Haemoglobin is composed from four molecules of hem and each of them contains one atom of iron. The main occupation of iron is transportation of oxygen. The rest of iron in the body is bound to transferine and feritine, small amount also to mioglobin. Iron is important for normal functioning of numerous enzymes. Iron deficiency in calves cause decreasing of haemoglobin and mioglobin concentration (Underwood & Suttle, 2001). In milk the iron is in relatively small quantity for all that in this period intensive synthesis of haemoglobin is expiring in calves (Kraft, 1999a). Long lasting iron deficiency influence on lost of appetite, growth retardation, whitening of mucous membranes due to progressive hypochromic anaemia (Underwood & Suttle, 2001). In fast growing suckling calves mild anaemia can appear, but usually it does not come to iron deficiency in ruminants, because

The calves were born with iron concentration around 27.7 ± 9.6 μmol/L, then it decreased on 18.0 ± 3.0 μmol/L at the age of 4 days. After the 2nd week of life iron concentration started to increase and at the age of 6 weeks it reached similar level as at birth (28.0 ± 7.8 μmol/L) (Bostedt et al., 1990). Knowles et al. (2000) established gradually increasing of iron concentration from 30th to 80th day of age, but at the age of 80 days the concentration was still on the lower limit of reference values for adult cattle. Other studies observed gradual increase of iron concentration to the age of 60 days (Steinhardt & Thielscher, 2000a;

Iron dynamics with age is influenced by feeding regime of calves. By suckler calves the iron concentration was low in the first weeks (around 9 μmol/L) later it increased to the age of 14 weeks (approximately 36 μmol/L). The calves which received milk replacer, have already at the age of 1-2 weeks, higher iron concentration as suckler calves. In calves which received starter and hay in addition to milk replacer the iron concentration increased to the 3rd week of age later it slightly oscillated but it did not decrease to the age of 13 weeks. In calves fed exclusively with milk replacer the iron concentration decreased after 2nd week of age and at the age of 14 weeks it was only 4 μmol/L (Reece & Hotchkiss, 1987; Scheidegger, 1973). In the calves fed only with milk replacer the iron concentration decreased from birth to the 10th week when it was 5.19 ± 4.29 μmol/L, later it increased slightly, but the lowest concentration was established at the age of 22 weeks when it was only 1.79 ± 1.43 μmol/L (Jazbec et al., 1975).

The concentration of urea in blood depends from nutrition, diagnostically is important also at diseases of kidneys (Kraft & Dürr, 1999b; Jazbec, 1990). Increased concentration of urea in calves' serum indicates increased catabolism of proteins and appears at long lasting

The colostrum intake did not influence the urea concentration (Steinhardt et al., 1993). In calves the urea concentration slightly decreased from birth to the age of 60 days when it was 2.7 mmol/L (Steinhardt & Thielscher, 2000d). Knowles et al. (2000) observed increasing of

there is enough iron in forage.

Steinhardt & Thielscher, 2000b).

**3.8 Urea** 

diarrhoeas (Jazbec, 1990).

reference values of enzyme activity claimed by different authors. Enzymes are very sensitive indicators of cell damage, their activity change by tiny alternations, so it is understandable that enzyme activity could rather differ between single animals. Consequently there are different results between studies. Reasons for these differences are partly differences between breeds and breeding conditions where the results were obtained. Great influences on the measurements have also analytical procedures and temperatures at which the activity of enzymes was measured. In majority of literature the mentioned analytical procedures are deficiently described, so it is very difficult to compare the data, because it is not clear at which temperature the activity of enzyme was measured. Some sources (Egli & Blum, 1998) claimed twice as high activity of LDH, as was measured by us. The reason is most likely in measuring procedure because the activity of LDH is measured with reaction of transformation pyruvate to lactate which can expire in both directions. With experiences in our laboratory was established that if the LDH activity is measured with reaction from lactate to pyruvate almost for a half lower values are obtained, than when LDH activity is measured with reaction from pyruvate to lactate.

#### **3.6 Total serum bilirubin**

Bilirubin is formatted by enzymatic decay of hem at disintegration of mature erythrocytes. These processes are taking course in spleen, liver and bone marrow. In blood plasma the unconjugated (indirect) bilirubin is bound to the albumin and is carried to the liver. With help of special protein called ligandin, bilirubin pass into hepatocytes. In the liver of newborns there is very low concentration of ligandin, so their ability to excrete the bilirubin is decreased. They can have for 50-100% higher serum concentrations as the adult animals (Jazbec, 1990; Tennant, 1997). At the end phase conjugated (direct) bilirubin pass into bile and than in the intestine. Increased concentration of total serum bilirubin in cattle is usually associated with cholestasis, fatty liver or haemolytic anaemia (Tennant, 1997), but can also be in connection with decreased appetite (Kraft & Dürr, 1999a).

The total serum bilirubin concentration in one day old calves was higher (9.58 μmol/L) than in adult animals. Later it decreased slowly and at 31-60 days of age it was 4.45 μmol/L (Hanschke & Schulz, 1982; Egli & Blum, 1998). Kurz and Willett (1991) observed increase of total serum bilirubin concentration in the first 12 hours of life for approximately five times and until 6th day the concentration decreased approximately to the value at birth. In the research of Mohri et al. (2007) bilirubin concentration decreased from 1st to the 14th day of age and later it remain stable. Higher concentration of total serum bilirubin after birth is associated with destruction of foetal haemoglobine and slower excretion of bilirubin because of lower concentration of transport protein ligandin. Ligandin enables passing of indirect bilirubin into hepatocytes where it is transformed to direct bilirubine which can be excreted (Tennant, 1997). After the second week of age the concentration of total serum bilirubin is inside reference values for adult animals. What can be associated with improvement of glomerular filtration and liver function with age.

#### **3.7 Serum iron**

Iron is present in the milk in very low concentration, but it is absorbed very efficiently from the gut (Underwood & Suttle, 2001). Efficiency of iron absorption depends from the needs of

reference values of enzyme activity claimed by different authors. Enzymes are very sensitive indicators of cell damage, their activity change by tiny alternations, so it is understandable that enzyme activity could rather differ between single animals. Consequently there are different results between studies. Reasons for these differences are partly differences between breeds and breeding conditions where the results were obtained. Great influences on the measurements have also analytical procedures and temperatures at which the activity of enzymes was measured. In majority of literature the mentioned analytical procedures are deficiently described, so it is very difficult to compare the data, because it is not clear at which temperature the activity of enzyme was measured. Some sources (Egli & Blum, 1998) claimed twice as high activity of LDH, as was measured by us. The reason is most likely in measuring procedure because the activity of LDH is measured with reaction of transformation pyruvate to lactate which can expire in both directions. With experiences in our laboratory was established that if the LDH activity is measured with reaction from lactate to pyruvate almost for a half lower values are obtained, than when LDH activity is

Bilirubin is formatted by enzymatic decay of hem at disintegration of mature erythrocytes. These processes are taking course in spleen, liver and bone marrow. In blood plasma the unconjugated (indirect) bilirubin is bound to the albumin and is carried to the liver. With help of special protein called ligandin, bilirubin pass into hepatocytes. In the liver of newborns there is very low concentration of ligandin, so their ability to excrete the bilirubin is decreased. They can have for 50-100% higher serum concentrations as the adult animals (Jazbec, 1990; Tennant, 1997). At the end phase conjugated (direct) bilirubin pass into bile and than in the intestine. Increased concentration of total serum bilirubin in cattle is usually associated with cholestasis, fatty liver or haemolytic anaemia (Tennant, 1997), but can also

The total serum bilirubin concentration in one day old calves was higher (9.58 μmol/L) than in adult animals. Later it decreased slowly and at 31-60 days of age it was 4.45 μmol/L (Hanschke & Schulz, 1982; Egli & Blum, 1998). Kurz and Willett (1991) observed increase of total serum bilirubin concentration in the first 12 hours of life for approximately five times and until 6th day the concentration decreased approximately to the value at birth. In the research of Mohri et al. (2007) bilirubin concentration decreased from 1st to the 14th day of age and later it remain stable. Higher concentration of total serum bilirubin after birth is associated with destruction of foetal haemoglobine and slower excretion of bilirubin because of lower concentration of transport protein ligandin. Ligandin enables passing of indirect bilirubin into hepatocytes where it is transformed to direct bilirubine which can be excreted (Tennant, 1997). After the second week of age the concentration of total serum bilirubin is inside reference values for adult animals. What can be associated with improvement of

Iron is present in the milk in very low concentration, but it is absorbed very efficiently from the gut (Underwood & Suttle, 2001). Efficiency of iron absorption depends from the needs of

measured with reaction from pyruvate to lactate.

be in connection with decreased appetite (Kraft & Dürr, 1999a).

glomerular filtration and liver function with age.

**3.7 Serum iron** 

**3.6 Total serum bilirubin** 

deficiency (Underwood & Suttle, 2001). The iron is very important for synthesis of haemoglobin. Approximately 60-75% of iron in the body is bound to haemoglobin (Kraft, 1999a). Haemoglobin is composed from four molecules of hem and each of them contains one atom of iron. The main occupation of iron is transportation of oxygen. The rest of iron in the body is bound to transferine and feritine, small amount also to mioglobin. Iron is important for normal functioning of numerous enzymes. Iron deficiency in calves cause decreasing of haemoglobin and mioglobin concentration (Underwood & Suttle, 2001). In milk the iron is in relatively small quantity for all that in this period intensive synthesis of haemoglobin is expiring in calves (Kraft, 1999a). Long lasting iron deficiency influence on lost of appetite, growth retardation, whitening of mucous membranes due to progressive hypochromic anaemia (Underwood & Suttle, 2001). In fast growing suckling calves mild anaemia can appear, but usually it does not come to iron deficiency in ruminants, because there is enough iron in forage.

The calves were born with iron concentration around 27.7 ± 9.6 μmol/L, then it decreased on 18.0 ± 3.0 μmol/L at the age of 4 days. After the 2nd week of life iron concentration started to increase and at the age of 6 weeks it reached similar level as at birth (28.0 ± 7.8 μmol/L) (Bostedt et al., 1990). Knowles et al. (2000) established gradually increasing of iron concentration from 30th to 80th day of age, but at the age of 80 days the concentration was still on the lower limit of reference values for adult cattle. Other studies observed gradual increase of iron concentration to the age of 60 days (Steinhardt & Thielscher, 2000a; Steinhardt & Thielscher, 2000b).

Iron dynamics with age is influenced by feeding regime of calves. By suckler calves the iron concentration was low in the first weeks (around 9 μmol/L) later it increased to the age of 14 weeks (approximately 36 μmol/L). The calves which received milk replacer, have already at the age of 1-2 weeks, higher iron concentration as suckler calves. In calves which received starter and hay in addition to milk replacer the iron concentration increased to the 3rd week of age later it slightly oscillated but it did not decrease to the age of 13 weeks. In calves fed exclusively with milk replacer the iron concentration decreased after 2nd week of age and at the age of 14 weeks it was only 4 μmol/L (Reece & Hotchkiss, 1987; Scheidegger, 1973). In the calves fed only with milk replacer the iron concentration decreased from birth to the 10th week when it was 5.19 ± 4.29 μmol/L, later it increased slightly, but the lowest concentration was established at the age of 22 weeks when it was only 1.79 ± 1.43 μmol/L (Jazbec et al., 1975).

#### **3.8 Urea**

The concentration of urea in blood depends from nutrition, diagnostically is important also at diseases of kidneys (Kraft & Dürr, 1999b; Jazbec, 1990). Increased concentration of urea in calves' serum indicates increased catabolism of proteins and appears at long lasting diarrhoeas (Jazbec, 1990).

The colostrum intake did not influence the urea concentration (Steinhardt et al., 1993). In calves the urea concentration slightly decreased from birth to the age of 60 days when it was 2.7 mmol/L (Steinhardt & Thielscher, 2000d). Knowles et al. (2000) observed increasing of

Values of Blood Variables in Calves 309

The concentration of albumin decreased after colostrum intake (27.5 g/L), and was approximately on the lower limit of reference values for adult cattle (Steinhardt et al., 1993; Kurz & Willet, 1991). In calves, which received colostrum, higher concentration of TSP was established, as in calves which received only milk replacer, what is associated with immunoglobulin absorption in the first ones (Muri et al., 2005). The concentration of TSP and albumin is influenced with nutrition of calves and functioning of the liver. The albumins are predominantly synthesised in the liver, so their amount depends on maturity and functional ability of the liver (Steinhardt & Thilescher, 2000c). Hypoalbuminemia in calves could be the consequence of liver damage or protein catabolism at long lasting diarrhoeas (Jazbec, 1990). In calves at the age from 8 to 15 weeks statistically significant differences in albumin concentration were established when they received meals with different amount of proteins (Hugi et al. 1997). Hammon et al. (2002) compared the calves which received limited or unlimited amounts of milk and established significantly lower albumin concentration in calves, to the age of 28 days, which were fed with unlimited amount of milk. Lower concentration of albumin in healthy animals could be the consequence of insufficient supply with amino acids (Whitaker, 1997). In calves from the 5th to the 40th day of age the concentration of TSP decreased slightly, after the 60th day it increased again and was 55.7 g/L. The concentration of albumin gradually increased from the 5th to the 60th respectively the 80th day of age (Steinhardt & Thielscher, 2000d; Knowles et al., 2000). In sucker calves gradual increase of TSP and albumin concentration was established from birth to the age of two months. The values of both variables were higher than in calves which were fed with limited

The absorption of iP is taking place in the forestomacs and in the front part of the small intestine. The iP is excreted with faeces and urine in cows in lactation also with milk. Phosphorus is important for normal growth and mineralization of bones. In the skeleton of adult animals is stored approximately 80% of all phosphorus in the body, which could be mobilised at need. The rest 20% of phosphorus is in soft tissues and body fluids where it collaborates in numerous important processes. It is the ingredient of deoxi- and ribonucleinacids, as phospholipids it is the part of cell membranes, as phosphate is important by regulation of osmotic and acid-base balance in the organism. Phosphorus has an important role in metabolism of energy, where it collaborates by transport of energy and fatty acids, synthesis of amino acids and proteins and working of Na/K pump (Underwood & Suttle, 2001). The serum concentration of iP is higher in young animals because the growth hormone increases the reabsorption of phosphate in the kidney (Rosol & Capen, 1997). In the rumen the phosphate is working as buffer for volatile fatty acids and as substrate for microorganisms. In ruminants with phosphorus deficiency, lower microbe synthesis of proteins in rumen is established. Phosphorus is important for the control of appetite and efficiently use of nutrients (Underwood & Suttle, 2001). By decrease of iP concentration in serum, increase the activity of ALP. Phosphorus deficiency in young animals causes the lost of appetite and retarded growth. In rachitic calves and lambs the concentration of iP is decreased for 30-50 % (Jazbec, 1990). Normal plasma concentration of iP in calves should be 1.3-1.9 mmol/L and 1.0-1.5 mmol/L in adult cattle (Underwood & Suttle, 2001). Kraft (1999b) claimed slightly higher values in calves serum namely; at the age until 2 months 2.6- 3.5 mmol/L, from 2 to 6 months it should be 2.5-3.1 mmol/L and from 12 to 18 months the

amounts of milk (Steinhardt & Thielscher, 2000b).

**3.11 Inorganic Phosphate (iP)** 

urea concentration from 40th to 80th day of age. Hanschke and Schulz (1982) established higher values of urea in the age 31-60 days in calves in subtropical climate, where the concentration of urea was 5.14 mmol/L. In calves with diarrhoea at the age 4-15 days twice as high mean urea concentration (7.98 mmol/L) in plasma was established as in healthy calves of the same age (3.89 mmol/L) (Maach et al., 1992). The authors claimed that measuring of urea concentration is very helpful for assessment of dehydration and disturbances of acid-base balance in calves with diarrhoea. Hugi et al. (1997) ascertained association between protein amount in forage and serum urea concentration in calves at the age 8 to 15 weeks.
