Korean Journal of
Veterinary Service

Hanwoo (Bos taurus coreanae) is the indigenous cattle breed of Korea. Since the 1960s, coinciding with Korea’s rapid economic growth, Hanwoo has been increasingly raised as a meat-producing breed (Lee et al., 2014). Over the decades, significant advancements in livestock improvement and feeding technologies have been implemented, leading to substantial enhancements in this breed’s characteristics. These advancements include the selection of certified sires and dams, revisions to feeding standards, and the application of genomic selection techniques (Jin et al., 2024). The results of these efforts are evident in the remarkable increase in the average weight of Hanwoo cattle. Specifically, the average weight rose from 506 kg in 1997 to 696 kg in 2020, representing a 37.5% increase over 23 years. This weight gain has been accompanied by a corresponding rise in meat production, underscoring the success of Korea’s long-term breeding and management strategies.

The body condition score (BCS) is a crucial indicator used to assess the degree of weight gain and fatness in cattle, based on subcutaneous fat deposits around the tail head, pelvic, and lumbar areas. This evaluation, typically performed through visual observation and palpation, quantifies results into a numerical score using either a 5-point or 9-point scale, where lower scores indicate leaner individuals and higher scores suggest a greater degree of fatness (Isensee et al., 2014; Lee et al., 2022). Various factors, including genetic selection, feeding practices, diet composition, age, calving, and parity, can influence BCS in cattle (Roche et al., 2009). This scoring system is particularly valuable for identifying health risks, assessing metabolic status, and facilitating livestock management by enabling the maintenance of appropriate body weight (Isensee et al., 2014). Moreover, BCS is closely associated with reproductive performance in cows, influencing factors such as the timing of ovarian activity, the onset of the first ovulation, embryo production, and conception rates in embryo transfer programs, making it an indispensable tool in both health management and breeding strategies for optimizing herd performance and welfare (Yeom et al., 2013).

Serum biochemistry is an essential tool in veterinary clinical practice, offering valuable insights into an animal’s health status and aiding in disease diagnosis and prognosis; under normal conditions, blood composition maintains homeostasis within a specific range, but this balance is disrupted during disease states, reflecting the organism’s physiological and pathological conditions (Lee et al., 2015; Cho et al., 2016). Various biochemical markers serve as indicators for different organ functions and metabolic processes. For instance, blood urea nitrogen (BUN), creatinine (CRE), and aspartate aminotransferase [AST, formerly glutamic-oxaloacetic transaminase (GOT)] can assess skeletal or cardiac muscle health. Liver function is evaluated using BUN, total protein (TP), glucose (GLU), albumin (ALB), alanine aminotransferase [ALT, formerly gamma-glutamyl transferase (GPT)], gamma-glutamyl transferase (GGT), and AST. Renal performance is evaluated by TP, ALB, inorganic phosphorus (IP), CRE, BUN, and calcium (Ca). Energy balance is associated with GLU and triglycerides (TG), while sodium (Na), potassium (K), chloride (Cl), and TP relate to metabolic function (Kim et al., 2021). It’s important to note that these biochemical values can vary depending on factors such as species, breed, age, sex, diet, and even the animal’s BCS, underscoring the need for careful interpretation within the context of each individual case (Lee et al., 2015; Wu et al., 2020; Kim et al., 2021).

While some studies have examined serum biochemistry values in Hanwoo cattle, most have focused on disease-related changes or age-related variations (Kim et al., 1997; Cho et al., 2008; Yu et al., 2010; Cho et al., 2016). However, there is limited research exploring the relationship between serum biochemistry and BCS in this breed. Furthermore, considering the significant changes in body size that Hanwoo cattle have undergone over the past two decades, it is likely that corresponding alterations in blood characteristics have occurred to maintain homeostasis. This study, therefore, aims to investigate the differences in biochemical parameters among BCS groups and analyze the correlation between blood biochemistry parameters and BCS in Hanwoo cattle. The goal is to provide valuable data that can be utilized to enhance management practices by monitoring health status and productivity in this breed.

Ethics statement

This study involved only retrospective analysis of data collected during routine veterinary care and does not require separate ethics committee approval. However, all procedures were conducted in compliance with veterinary ethical standards.

Serum biochemical tests in Hanwoo

In this study, serum biochemical tests were conducted on 45 healthy Hanwoo cattle (approximately 2.7 years old). The farms (N=3) were placed in Gumi-si, Gyeongsangbuk-do, Republic of Korea and fed a diet of forage and concentrate to cattle, according to the Korean Feeding Standard for Hanwoo established by the Rural Development Administration. Prior to sampling, a veterinarian performed general inspections, physical examinations, and checking BCS. Fresh whole blood samples were collected via jugular venipuncture into plain tubes and immediately transported to the research laboratory at Kyungpook National University within 1 hour. The samples were centrifuged at 2,000×g for 10 minutes, after which serum was isolated and stored at −80℃. Serum biochemical parameters were analyzed using the DRI CHEM NX700 (Fujifilm, Tokyo, Japan) for a comprehensive panel including GLU, TG, high-density lipoprotein (HDL), BUN, IP, CRE, TP, ALB, globulin (GLOB), GGT, GPT, GOT, Na, K, Cl, and Ca, along with the ratios of ALB/GLOB, GOT/GPT, BUN/CRE, and Na/K. Reference ranges for these parameters were sourced from Veterinary Medicine (7^th Edition; Blood et al., 2007) and Cornell University College of Veterinary Medicine (Cornell University College of Veterinary Medicine, 2017).

Scoring the body condition and group classification

The BCS of cattle was evaluated using a 5-point scale based on the Ferguson system as described by Elanco (1997), with scores ranging from 1.0 to 5.0 in 0.25 increments (Isensee et al., 2014). This method involves visual assessment and palpation of body areas including the loin, pelvic region, and tail head. The assessment begins with the pelvic area, where a V-shaped line indicates a score ≤3.00, while a U-shaped line suggests a score ≥3.25. As all cattle in the present study exhibited a U-line or transitional appearance from V-line to U-line, indicating a score ≥3.25, they were classified into three groups in the present study: group 1 (BCS: 3.0∼3.25), group 2 (BCS: 3.5∼3.75), and group 3 (BCS: 4.0∼4.25), with detailed scoring procedures and classification provided in Table 1.

Table 1 . Body condition score (BCS) criteria used to classify Hanwoo cattle.

Group (BCS range)	Criteria for BCS
Group 1 (BCS: 3.0∼3.25)	• Transition from angular to more rounded appearance of the pelvic area • Hooks and pin bones are moderately visible • Ligaments between the pin bones and around the tail head are clearly defined • Moderate fat cover over the loin and rump areas
Group 2 (BCS: 3.5∼3.75)	• Rounded appearance of the pelvic area • Hooks and pin bones are visible but less prominent • Ligaments are still discernible but less pronounced • Considerable fat cover over the loin and rump areas
Group 3 (BCS: 4.0∼4.25)	• Rounded appearance of the pelvic area • Hooks and pin bones are less visible due to fat coverage • Ligaments are barely visible or completely obscured • Substantial fat cover over the loin and rump areas, creating a smooth contour

Statistical analysis

In the analysis of descriptive statistics, raw values for each serum biochemistry parameter in cattle were calculated for the mean and standard deviation (SD). Significant differences among groups were assessed using one-way ANOVA followed by Tukey’s post hoc test (SPSS 27.0, SPSS Inc., Chicago, IL, USA). The results are presented as mean±SD. In addition, Pearson’s correlation analysis was performed to evaluate the relationship between raw values of serum biochemistry parameters and BCS. Statistical significance was set at P<0.05.

Scoring the body condition and group classification

The cattle used in this study were divided into three groups based on the criteria listed in Table 1, and the representative BCS images for each group are shown in Fig. 1. In the classification of Hanwoo based on BCS in the present study, both group 1 (BCS: 3.0∼3.25) and 2 (BCS: 3.5∼3.75) included 18 cattle, and group 3 (BCS: 4.0∼4.25) comprised 9 cattle.

Figure 1. Representative images (lateral and posterior views) for three BCS groups of Hanwoo cattle. The body condition score (BCS) of Hanwoo in this study was evaluated using a 5-point scale based on the Ferguson system, described in Table 1, and they were classified into three groups as group 1 (BCS: 3.0∼3.25), group 2 (BCS: 3.5∼3.75), and group 3 (BCS: 4.0∼4.25).

Descriptive statistics in serum biochemistry

The analysis of 20 serum biochemical parameters in Hanwoo cattle revealed variations in their values among different BCS groups (Table 2). Significant differences (P<0.05) were identified in several parameters, including BUN, GGT, TG, and BUN/CRE ratio. Specifically, TG and the BUN/CRE ratio showed significant increases as BCS increased. BUN exhibited a significant difference between group 1 and group 2 but not between group 2 and group 3. The GGT showed a significant difference between group 1 and group 3, while group 2 displayed a trend similar to both group 1 and group 3. Notably, some values, such as GLU and Ca, fell outside the upper and lower reference limits reported in reference range from Veterinary Medicine (7^th Edition; Blood et al., 2007). Additionally, parameters including TG, CRE, TP, ALB, GGT, GOT, Cl, and Ca exceeded the reference limits provided by Cornell University College of Veterinary Medicine. However, because this study used only clinically healthy and normal Hanwoo cattle, relying solely on the normal hematological ranges established from other breeds may compromise the reliability of the clinical results for Hanwoo cattle.

Table 2 . Descriptive statistics of biochemical parameters obtained from three groups of Hanwoo cattle.

Parameter	Unit	Descriptive statistics on different groups				Reference range
		Group 1 (n=18)	Group 2 (n=18)	Group 3 (n=9)		Veterinary Medicine 7th ED.	Cornell University College of Veterinary Medicine
GLU	mg/dL	60.94±2.89	60.77±2.09	69.28±4.52		35.0∼55.0	57.0∼79.0
TG	mg/dL	10.87±1.39a	17.7±1.71b	28.85±2.82c		-	10∼19
HDL	mg/dL	90.27±3.24	102.95±4.71	91.14±4.20		-	-
BUN	mg/dL	8.78±0.68a	13.48±0.88b	15.65±0.09b		-	7.0∼19.0
IP	mg/dL	5.83±0.42	5.22±0.20	5.66±0.40		-	-
CRE	mg/dL	1.00±0.06	1.30±0.04	1.10±0.03		1.0∼2.7	0.4∼0.9
TP	g/dL	6.4±0.19	7.00±0.12	7.08±0.35		5.7∼8.1	6.7∼8.8
ALB	g/dL	3.11±0.09	3.21±0.06	3.31±0.13		2.1∼3.6	3.3∼4.3
GLOB	g/dL	3.28±0.14	3.77±0.11	3.77±0.28		-	2.8∼5.4
GGT	U/L	15.27±1.58a	20.55±2.70ab	27.57±3.33b		-	17.0∼54.0
GPT (ALT)	U/L	24.33±0.99	22.3±0.95	21.00±0.69		-	-
GOT (AST)	U/L	43.76±3.16	38.77±1.66	48.16±4.32		60.0∼150.0	54.0∼135.0
Na	mEq/L	137.83±1.98	139.26±1.22	140.57±2.37		132.0∼152.0	134.0∼144.0
K	mEq/L	4.95±0.21	4.95±0.12	4.91±0.08		3.9∼5.8	4.0∼5.9
Cl	mEq/L	100.11±1.58	101.89±0.90	102.28±1.66		95.0∼110.0	92.0∼99.0
Ca	mg/dL	7.51±0.31	7.48±0.27	6.95±0.32		8.0∼10.5	8.9∼10.9
ALB/GLOB	-	0.96±0.04	0.86±0.03	0.89±0.06		-	0.6∼1.6
GOT/GPT	-	1.80±0.13	1.82±0.08	2.24±0.21		-	-
BUN/CRE	-	7.49±0.72a	10.46±0.85b	14.35±1.04c		-	-
Na/K	-	28.58±1.08	28.35±0.60	28.66±0.73		-	-

^a,b,cDifferent superscripts indicate significant (P<0.05) difference between groups..

GLU, glucose; TG, triglycerides; HDL, high-density lipoprotein; BUN, blood urea nitrogen; IP, inorganic phosphorus; CRE, creatinine; TP, total protein; ALB, albumin; GLOB, globulin; GGT, gamma-glutamyl transferase; GPT (ALT), glutamic-pyruvic transaminase (alanine aminotransferase); GOT (AST), glutamic-oxaloacetic transaminase (aspartate aminotransferase)..

Correlation between BCS and blood biochemical parameters

Among the 20 hematological parameters analyzed in Hanwoo cattle, seven showed a significant correlation with the increase in BCS (Fig. 2). A significantly positive correlation was found between BCS and BUN (r=0.688, P=0.000), GGT (r=0.424, P=0.004), TG (r=0.629, P=0.000), TP (r=0.393, P=0.008), GLOB (r=0.352, P=0.019), and BUN/CRE ratio (r=0.670, P=0.000). In contrast, a significantly negative correlation was observed between BCS and GPT (r=−0.298, P=0.046). However, no statistically significant correlation was found between BCS and electrolytes such as Na, K, and Cl. These results indicate that even in healthy physiological conditions, the hematological parameters of Hanwoo cattle can change to maintain homeostasis during the fattening period. Additionally, the findings of this study provide the normal range of hematological values for Hanwoo cattle during the fattening phase.

Figure 2. Pearson’s correlation analysis between raw values of serum biochemistry parameters and body condition score (BCS) of Hanwoo cattle. The Pearson’s correlation coefficients between each serum biochemistry parameter and BCS are displayed at the top of the graph. A significant correlation was considered at P<0.05.
GLU, glucose; TG, triglycerides; HDL, high-density lipoprotein; BUN, blood urea nitrogen; IP, inorganic phosphorus; CRE, creatinine; TP, total protein; ALB, albumin; GLOB, globulin; GGT, gamma-glutamyl transferase; GPT (ALT), glutamic-pyruvic transaminase (alanine aminotransferase); GOT (AST), glutamic-oxaloacetic transaminase (aspartate aminotransferase).

The BCS is a crucial indicator for assessing weight gain and fatness in cattle during the fattening phase, based on subcutaneous fat deposits (Isensee et al., 2014). In Hanwoo cattle, advancements in livestock management and feeding technologies, including genetic selection and revised feeding standards, have significantly increased average body weights (Jin et al., 2024). This has made BCS an essential tool for evaluating health, metabolic status, and reproductive performance (Choe et al., 2018; Kim et al., 2024). The fattening of Hanwoo cattle involves stage-specific nutrition management, with different feeding strategies applied at each growth stage to ensure optimal muscle and fat accumulation. For instance, during the growth phase, high-quality forages are provided to prepare for long-term fattening, while during the pre-fattening phase, restricted feeding of balanced rations ensures even accumulation of muscle and fat. Nutrient intake also varies by stage, with specific requirements for crude protein and digestible energy. In addition, health management is critical, particularly in the late pre-fattening phase, where metabolic diseases such as urolithiasis can occur due to changes in feed intake. While BCS is a system that can indirectly monitor the nutritional status of cattle during the fattening period, it does not provide a complete picture of their health status or all hematological changes. Particularly in the late fattening stage, where rapid weight gain occurs, monitoring the body’s homeostasis can be beneficial for maintaining a healthy fattening herd and increasing productivity. While studies have investigated the relationship between biochemical markers and BCS in lactating dairy cows (Wu et al., 2020), the correlation between serum biochemical values and different BCS levels in Hanwoo cattle remains poorly understood. To address this gap, this study analyzed the differences in biochemical parameters among BCS groups and investigated their correlations with BCS in Hanwoo cattle. The results revealed significant differences (P<0.05) between BCS groups in BUN, GGT, TG, and BUN/CRE ratio. Furthermore, significant correlations were found between BCS and several parameters, including GGT, GPT, TG, TP, GLOB, and the BUN/CRE ratio.

The study revealed significant differences (P<0.05) in BUN and BUN/CRE ratio among different BCS groups. BUN levels are influenced by urea synthesis in the liver and its excretion through the urinary tract. In dogs, decreased renal excretion is the most common cause of increased BUN concentrations, making BUN a reliable indicator of renal function. The BUN/CRE ratio is often used as a more comprehensive measure of kidney function, as it accounts for variations in hydration status and muscle mass (Prause and Grauer, 1998). However, in cattle, BUN concentrations are primarily influenced by dietary factors, such as energy level, protein intake, and protein degradability, although other factors like health status, physiological state, breed, lactation, and production levels also play a role (Hammond et al., 1994). The cattle used in this study were young, with a low possibility of age-related diseases, and only clinically healthy individuals were selected. Therefore, the increase in BUN and BUN/CRE ratio observed with increasing BCS in this study is likely due to increased protein feeding during the fattening stage. This finding highlights the importance of considering factors such as diet and production stage when evaluating BUN levels in cattle, as opposed to immediately attributing elevated BUN to kidney issues. It also underscores the need for a more nuanced approach to interpreting biochemical markers in different species and production systems within veterinary medicine. For instance, in dairy cows, an excessive supply of degradable protein has been shown to elevate serum urea nitrogen (SUN) concentrations, with a significant rise in plasma urea nitrogen (PUN) observed when cows were fed diets containing 17% crude protein (CP) compared to diets with 13% CP (Elrod and Butler, 1993; Kauffman and St-Pierre, 2001). Unlike BUN, serum CRE, which is excreted exclusively by the kidneys, is influenced only by muscle mass, making it a more specific indicator of renal function compared to BUN. The elevation of BUN/CRE ratio, which can provide valuable insights into the presence of intrinsic or extrinsic renal disease, typically arises from three primary mechanisms: overproduction of urea, decreased urea elimination relative to CRE, or reduced serum CRE levels due to decreased production (Robinson and Weber, 2002). Interestingly, while Jung et al. (2004) reported no direct relationship between BUN and BCS in Hanwoo cattle, the present study observed a significant increase in BUN and BUN/CRE ratio levels as BCS increased. Additionally, a significant positive correlation was found between BUN and BUN/CRE values with BCS in Hanwoo cattle. Since the BUN and BUN/CRE values observed in this study remained within the reference ranges outlined in Veterinary Medicine (7^th Edition; Blood et al., 2007), it is plausible that the higher intake of protein-rich feeds, such as those containing CP, in individuals with higher BCS may have contributed to these findings, rather than indicating a problem with renal function.

The study revealed significant correlations between BCS and protein-related parameters, including TP and GLOB. Protein-rich intake can influence serum TP, which is composed of approximately 60% ALB and 40% GLOB (Asrar et al., 2023). In dairy cows, TP, ALB, GLOB, and ALB/GLOB ratio are sometimes used as markers of inflammatory conditions, such as bovine mastitis (Bobbo et al., 2017b; Carvalho-Sombra et al., 2021). However, the observed positive correlation of TP and GLOB with BCS in the present study, while remaining within reference ranges and being derived from clinically healthy individuals, suggests that these changes are more likely related to dietary factors rather than inflammatory or metabolic imbalances. This interpretation is supported by research showing that high-producing herds, characterized by greater use of concentrates in the diet, had higher serum ALB concentrations (Bobbo et al., 2017a). Furthermore, studies have demonstrated that increasing dietary CP levels can affect carcass traits and growth performance in beef cattle, although the optimal protein level may vary depending on the production stage and breed (Jeon et al., 2021). In addition, it’s important to note that serum protein levels can be influenced by various factors, including herd productivity, breed, age, and stage of lactation, which should be considered when interpreting these results (Bobbo et al., 2017a).

This study revealed significant differences (P<0.05) in GGT and TG levels among different BCS groups, and significant correlations were found between BCS and several liver-related parameters such as GGT and GPT, and TG. The GGT, GPT, and GOT are indicators of liver dysfunction, with GGT being a valuable diagnostic parameter for hepatobiliary disorders in cattle, such as cholestasis, asciolosis, liver necrosis, bovine ketosis, and angiomatosis (Braun et al., 1983; Moreira et al., 2012). Given that the cattle used in this study were free from any underlying diseases, the increase in GGT levels in the high BCS group is likely attributable to mild or subclinical hepatic lipidosis, caused by high protein diet during fattening period (Elshafey et al., 2023). This is supported by research showing that cows with high BCS, due to increased insulin resistance, exhibit greater accumulation of triacylglycerol in the liver, leading to downregulated tissue lipoprotein lipase activity and impaired utilization of very-low-density lipoprotein (VLDL)-triacylglycerol, which ultimately results in increased TG levels; this mechanism accounts for the significant increase in TG level and the positive correlation between TG and BCS in the present study (Wu et al., 2020). Interestingly, GPT levels showed a negative correlation with BCS in this study. GPT levels can increase in response to injury or inflammation and decrease when synthetic capacity is impaired. Although some human studies suggest an association between body mass index (BMI) and GPT levels (Visaria et al., 2020), evidence supporting the negative correlation between BCS and GPT in cattle remains limited, indicating a need for further investigation in this area.

In conclusion, this study investigated the relationship between different BCS and serum biochemical parameters in Hanwoo cattle, revealing significant differences in BUN, GGT, GPT, TG, GLOB, and BUN/CRE ratio. The observed changes in biochemical parameters in high BCS cattle are likely related to dietary and metabolic factors rather than intrinsic or extrinsic disease, emphasizing the importance of considering body condition and nutritional status when interpreting biochemical levels. These findings highlight the significance of BCS as an indicator of health, management, and productivity in Hanwoo cattle, providing valuable insights into the physiological changes associated with different BCS levels. By facilitating better monitoring of health status and productivity, this study contributes to improving management strategies for Hanwoo cattle, potentially enhancing overall productivity in this important Korean cattle breed. The results underscore the close association between BCS, feed intake, and serum biochemical parameters, offering valuable data for refining cattle management practices and advancing our understanding of bovine physiology.

This work was supported by a grant from the National Research Foundation (NRF) of Korea, funded by the government of the Republic of Korea (RS-2023-00251171).

No potential conflict of interest relevant to this article was reported.