**Values of Blood Variables in Calves**

Martina Klinkon and Jožica Ježek

*Clinic for Ruminants, Veterinary Faculty, University of Ljubljana, Slovenia* 

#### **1. Introduction**

300 A Bird's-Eye View of Veterinary Medicine

Zuckermann, F.A.; Garcia, E.A.; Luque, I.D.; Christopher-Hennings, J.; Doster, A.; Brito, M.;

ISSN 0378-1135.

& Osorio, F. (2007). Assessment of the efficacy of commercial porcine reproductive and respiratory syndrome virus (PRRSV) vaccines based on measurement of serologic response, frequency of gamma-IFN-producing cells and virological parameters of protection upon challenge. *Veterinary Microbiology*, Vol. 12, pp. 69–85.

> Haematological and biochemical variables are most widely used medical decision making tool. Haematological and biochemical analyses of blood are very useful to get an insight in metabolic and health status of animal. During diagnostic procedure it is very useful to compare the values obtained from ill animal with normal values in healthy animals. Therefore specific reference intervals are needed for each animal species for appropriate interpretation of results of haematological and biochemical analyses. The reference values of different blood variables are well established for adult cattle, but for calves there is not a lot of data available. The values of different blood variables in calves and other young animals are changing with age. The values of haematological variables change after birth because of colostrums intake, short life time of erythrocyte and decrease of concentration of foetal haemoglobin. In growing calves the feeding and rearing system has an important influence on the values of different blood variables. Influence of feeding becomes more apparent after 5th week when consummation of dry food (hay, starter) increases

> In our contribution we would like to present the results of our research about different blood variables (haematological, biochemical) in calves and their dependence from age (from birth till age of 6 months). Further we will discuss about factors which influence the values of different blood variables like; laboratory methods, feeding and rearing systems, health status, etc. We would like to explain how the knowledge about values of blood variables could be used for proper interpretation of results of laboratory analyses and for assessment of health or metabolic status in an animal.

#### **2. Haematological variables in calves**

The number of erythrocytes (E) in blood is lover in young animals and indicates more signs of regeneration (higher number of reticulocytes) as in adult animals (Kraft, 1999a). The life span of E in cattle lasts 160 days. Different authors studied values of haematological variables in calves and observed that the values are changing with age (Greatorex, 1954; Scheidegger, 1973; Hanschke & Schulz, 1982; Steinhardt & Thielscher, 2000a; Steinhardt & Thielscher, 2000b; Klinkon et al., 2000;Brun-Hansen et al., 2006; Moosavian et al., 2010;Mohri et al., 2010). Immediately after parturition the values of (PCV), haemoglobin (Hb) and

Values of Blood Variables in Calves 303

increased from birth to the age of 10 weeks, than it oscillated more or less to the age of 1 year and is slightly higher as in adult animals the most of values are between 6.5-11.5 x 109/L (Greatorex, 1954). Terosky et al. (1997) observed the oscillation of WBC number in the period from birth to the age of 18 months; the number was between reference values for adult animals. In calves fed exclusively with milk replacer the number of WBC decreased after the 1st week (10.42 ± 2.29 x 109/L) and was 7.30 ± 1.21 x 109/L at the age of 21 weeks

The number of platelets (PLT) in calves is around 400 x 109/L in the first three days of life, then it increase rapidly to 900 x 109/L at 10 days of age. Then after the PLT number increase slowly when it amount 1100 x 109/L, later it decrease slightly (Knowles et al. 2000). In Norwegian research performed on calves of Norwegian Red breed the increasing of PLT number to the age of 2 weeks was observed when it was 987 x 109/L. Then the PLT number decreased slowly to the age of 27-29 weeks, when it was 518 x 109/L (Brun-Hansen et al., 2006). In Simmental calves the PLT number increased rapidly from the 1st to the 7th day of life, later it almost did not change to the age of 84 days (Egli & Blum, 1998). The observations of different studies indicate that PLT number increase rapidly in the first days

The results of various studies on age dependent dynamics of haematological variables are different what established also the other researchers (Jain, 1986; Knowles et al., 2000). The differences are influenced by the fact that blood samples were taken in different age periods,

By analysing of results of different studies was established, that the most marked differences are between calves which are fed with milk or milk replacer and receive starter and hay and veal calves which receive predominantly or exclusively milk or milk replacer and no hay. The differences in values of haematological variables are partly influenced with the use various analysing methods. In older studies the blood cells were counted manually with Neubauer chambers, PCV values were estimated with centrifugation in microhaematocrit tubes, and Hb concentration was measured photometrical (Greatorex, 1954; Hanschke & Schulz, 1982). In later studies the blood cell numbers were counted with automated counters from different producers, PCV value was still estimated by microhaematocrit method (Scheidegger, 1973; Terosky, 1997; Steinhardt & Thielscher, 2000a; Steinhardt & Thielscher, 2000b; Reece & Hotchkiss, 1987). In most of recent researches, which were published in last years the haematological variables were measured with various automated counters (Egli & Blum, 1998; Muri et al., 2005; Knowles et al., 2000; Klinkon et al., 2000; Mohri et al., 2007,

The knowledge about normal values of biochemical variables in blood serum and other physiological variables is important for assessment of damage of organs and tissues in different diseases and for assessment of development from the welfare aspect (Steinhardt & Thilescher, 2000c; Terosky et al., 1997). The values of biochemical variables in calf's serum differ from the values in adult animals. Different authors ascertained that there are deficient data available about physiological values of biochemical variables in calves and that results

of life, and for later the establishments of studies about PLT dynamics differ.

breeds, rearing systems, geographic regions, and different feeding system.

(Jazbec et al., 1973).

Heidarpour Bami et al., 2008).

**3. Biochemical variables in calves** 

number of E are higher and they decreased in first days of life what could be associated with colostrum intake, which increase the plasma volume due to osmotic effect (Scheidegger, 1973; Harvey, 1997). To decreased values contribute also lover production of erythrocytes in first days after parturition and shorter life span of intrauterine produced E (Harvey, 1997). The findings of Kurz and Willet (1991) are in agreement with these establishments. They studied the dynamics of Hb and PCV values and number of E in calves from the 1st to the 6th day after calving and established continuous decrease of mentioned variables from birth till the 6th day when the Hb concentration was 9.3 g/dl, value of PCV was 27.2 % and number of E was 7.1 x 1012/L. The different time of first colostrum intake did not influence the dynamics of these variables. Similar dynamics till 5th day after birth observed also Muri et al. (2005) in calves of Simmental and Holstein Friesian breed only they established slightly lover values of Hb (6.6 g/dl), PCV (24 %) and E (7.8 x 1012/L) as were established in other studies (Scheidegger, 1973; Kurz & Willet, 1991; Egli & Blum, 1998). Mohri et al. (2007) observed a decrease of PCV and Hb from birth to the age of 28 days later the values increased with age. Heidarpour Bami et al. (2008) found lower values of Hb and PCV to the age of 28 d in calves, which did not received iron and higher values in those, which received iron injections. In veal calves the highest values of some variables were established immediately after birth E (9.35 x 1012/L), Hb (12.86 g/dl), PCV (41 %), MCV (43.2 fL) in L (13.99 x 109/L). The values decreased to the age of 48 hours and at the age of 3 weeks they observed higher values except MCV value which still decreased (Adams et al., 1992). Higher values of E, Hb and PCV are response of calf's organism to the hypoxia which could appear at the end of the pregnancy (Steinhardt et al., 1993). The decrease of haematological variables in the first weeks after calving was observed by majority of authors and is influenced also by decline of foetal erythrocytes which contain foetal Hb (HbF), they are replacing with E containing haemoglobin of adult animals HbA (Scheidegger 1973; Harvey, 1997) and have smaller volume. Smaller MCV is compensated with higher number of E to retain normal Hb amount which is nearly on the level of adult animals (Brun-Hansen et al. 2006).

In growing calves feeding and rearing system has an important influence on the values of haematological variables (Reece & Hotchkiss, 1987; Scheidegger, 1973). Influence of feeding regime becomes more apparent after the 5th week when consummation of dry food (hay, starter) increases. In this period the values of RBC, Hb and Ht increase. In veal calves fed predominantly with milk the values of mentioned variables decreased and calves become anaemic due to iron deficiency. In calves fed exclusively with milk replacer (feeding for white meat) the number of E decreased from birth to the age of 15 weeks when it was only 3.96 ± 0.66 x 1012/L. Similar dynamics was observed by Hb concentration which was 7.65 ± 1.28 g% at the age of 15 weeks and PCV value which decreased from 41.40 ± 5.86 % in the 1st week to 26.82 ± 5.03 % in the 15th week (Jazbec et al., 1973).

The number of leucocytes (WBC) in blood of calves is higher in comparison with adult animals and is more variable as values of other haematological variables. Different types of leucocytes have different life spans so their number can change rapidly and blood serves only as transport medium from the place of origin to the place of inflammation (Kraft, 1999a). The number of WBC usually increases at the presence of disease, especially in association with inflammatory processes and possibly at stress. The number of WBC

number of E are higher and they decreased in first days of life what could be associated with colostrum intake, which increase the plasma volume due to osmotic effect (Scheidegger, 1973; Harvey, 1997). To decreased values contribute also lover production of erythrocytes in first days after parturition and shorter life span of intrauterine produced E (Harvey, 1997). The findings of Kurz and Willet (1991) are in agreement with these establishments. They studied the dynamics of Hb and PCV values and number of E in calves from the 1st to the 6th day after calving and established continuous decrease of mentioned variables from birth till the 6th day when the Hb concentration was 9.3 g/dl, value of PCV was 27.2 % and number of E was 7.1 x 1012/L. The different time of first colostrum intake did not influence the dynamics of these variables. Similar dynamics till 5th day after birth observed also Muri et al. (2005) in calves of Simmental and Holstein Friesian breed only they established slightly lover values of Hb (6.6 g/dl), PCV (24 %) and E (7.8 x 1012/L) as were established in other studies (Scheidegger, 1973; Kurz & Willet, 1991; Egli & Blum, 1998). Mohri et al. (2007) observed a decrease of PCV and Hb from birth to the age of 28 days later the values increased with age. Heidarpour Bami et al. (2008) found lower values of Hb and PCV to the age of 28 d in calves, which did not received iron and higher values in those, which received iron injections. In veal calves the highest values of some variables were established immediately after birth E (9.35 x 1012/L), Hb (12.86 g/dl), PCV (41 %), MCV (43.2 fL) in L (13.99 x 109/L). The values decreased to the age of 48 hours and at the age of 3 weeks they observed higher values except MCV value which still decreased (Adams et al., 1992). Higher values of E, Hb and PCV are response of calf's organism to the hypoxia which could appear at the end of the pregnancy (Steinhardt et al., 1993). The decrease of haematological variables in the first weeks after calving was observed by majority of authors and is influenced also by decline of foetal erythrocytes which contain foetal Hb (HbF), they are replacing with E containing haemoglobin of adult animals HbA (Scheidegger 1973; Harvey, 1997) and have smaller volume. Smaller MCV is compensated with higher number of E to retain normal Hb

amount which is nearly on the level of adult animals (Brun-Hansen et al. 2006).

week to 26.82 ± 5.03 % in the 15th week (Jazbec et al., 1973).

In growing calves feeding and rearing system has an important influence on the values of haematological variables (Reece & Hotchkiss, 1987; Scheidegger, 1973). Influence of feeding regime becomes more apparent after the 5th week when consummation of dry food (hay, starter) increases. In this period the values of RBC, Hb and Ht increase. In veal calves fed predominantly with milk the values of mentioned variables decreased and calves become anaemic due to iron deficiency. In calves fed exclusively with milk replacer (feeding for white meat) the number of E decreased from birth to the age of 15 weeks when it was only 3.96 ± 0.66 x 1012/L. Similar dynamics was observed by Hb concentration which was 7.65 ± 1.28 g% at the age of 15 weeks and PCV value which decreased from 41.40 ± 5.86 % in the 1st

The number of leucocytes (WBC) in blood of calves is higher in comparison with adult animals and is more variable as values of other haematological variables. Different types of leucocytes have different life spans so their number can change rapidly and blood serves only as transport medium from the place of origin to the place of inflammation (Kraft, 1999a). The number of WBC usually increases at the presence of disease, especially in association with inflammatory processes and possibly at stress. The number of WBC increased from birth to the age of 10 weeks, than it oscillated more or less to the age of 1 year and is slightly higher as in adult animals the most of values are between 6.5-11.5 x 109/L (Greatorex, 1954). Terosky et al. (1997) observed the oscillation of WBC number in the period from birth to the age of 18 months; the number was between reference values for adult animals. In calves fed exclusively with milk replacer the number of WBC decreased after the 1st week (10.42 ± 2.29 x 109/L) and was 7.30 ± 1.21 x 109/L at the age of 21 weeks (Jazbec et al., 1973).

The number of platelets (PLT) in calves is around 400 x 109/L in the first three days of life, then it increase rapidly to 900 x 109/L at 10 days of age. Then after the PLT number increase slowly when it amount 1100 x 109/L, later it decrease slightly (Knowles et al. 2000). In Norwegian research performed on calves of Norwegian Red breed the increasing of PLT number to the age of 2 weeks was observed when it was 987 x 109/L. Then the PLT number decreased slowly to the age of 27-29 weeks, when it was 518 x 109/L (Brun-Hansen et al., 2006). In Simmental calves the PLT number increased rapidly from the 1st to the 7th day of life, later it almost did not change to the age of 84 days (Egli & Blum, 1998). The observations of different studies indicate that PLT number increase rapidly in the first days of life, and for later the establishments of studies about PLT dynamics differ.

The results of various studies on age dependent dynamics of haematological variables are different what established also the other researchers (Jain, 1986; Knowles et al., 2000). The differences are influenced by the fact that blood samples were taken in different age periods, breeds, rearing systems, geographic regions, and different feeding system.

By analysing of results of different studies was established, that the most marked differences are between calves which are fed with milk or milk replacer and receive starter and hay and veal calves which receive predominantly or exclusively milk or milk replacer and no hay. The differences in values of haematological variables are partly influenced with the use various analysing methods. In older studies the blood cells were counted manually with Neubauer chambers, PCV values were estimated with centrifugation in microhaematocrit tubes, and Hb concentration was measured photometrical (Greatorex, 1954; Hanschke & Schulz, 1982). In later studies the blood cell numbers were counted with automated counters from different producers, PCV value was still estimated by microhaematocrit method (Scheidegger, 1973; Terosky, 1997; Steinhardt & Thielscher, 2000a; Steinhardt & Thielscher, 2000b; Reece & Hotchkiss, 1987). In most of recent researches, which were published in last years the haematological variables were measured with various automated counters (Egli & Blum, 1998; Muri et al., 2005; Knowles et al., 2000; Klinkon et al., 2000; Mohri et al., 2007, Heidarpour Bami et al., 2008).
