Hyunjin Cho

Objective: Mastitis is a major disease affecting dairy cows that requires timely detection to enable efficient management and to reduce substantial economic losses. In this study, we developed a practical mastitis monitoring framework based exclusively on daily milk yield, a routinely collected and noninvasive variable readily available from automated milk-recording systems.Methods: Daily milk yield records (n = 121,692) from 555 Holstein cows on four Korean dairy farms were analyzed. Lactations were reconstructed, and mastitis datasets were matched 1:1 with non-mastitis controls by farm, date, and days in milk. After completeness screening, 63 matched pairs were divided into development (44 pairs) and test datasets (19 pairs). Expected yield was estimated using exponential smoothing and a modified Wilmink equation. The index combined milk yield reduction, a day-specific 90% lower prediction threshold, and consecutive negative deviations. Index changes were compared across 7-, 9-, and 11-day intervals, and alert rules based on index level, relative decline, or both were optimized in the development dataset and evaluated in the test dataset.Results: In mastitis datasets, mean index scores gradually decreased from the pre-diagnosis to post-diagnosis intervals across all window sizes, with significant differences among all three intervals (p<0.05). No significant interval-dependent differences were observed in matched non-mastitis datasets. In the development dataset, the highest F1-score was 0.800 at day +7 using a 3-day evaluation window and a 5% relative-decline rule. In the test dataset, the best and most balanced performance was observed from days +4 to +6, with accuracy, sensitivity, specificity, and F1-score all reaching 0.790.Conclusion: Persistent deviations from expected daily milk production patterns can be converted into an interpretable alert signal for mastitis-associated changes. The proposed framework may support practical and noninvasive identification of cows requiring closer observation or confirmatory testing without additional sensors or invasive sampling.

Detecting feeding behavior in cattle is important but can be cumbersome when done manually. This study aimed to validate two wearable biosensors─RumiWatch noseband (RW) and Nedap SmartTag Neck (ND)—for monitoring feeding behavior in Hanwoo cattle. Specifically, we assessed the agreement between feeding behaviors recorded by RW and ND and those obtained manually through video observation (VO), focusing on eating time (ET) and ruminating time (RT). Three Hanwoo cows (540 ± 24.12 kg) were fitted with both sensors and continuously video-recorded for three consecutive days. Data from both 1 h (n = 216) and 24 h (n = 9) summaries were used to compare RW with VO, while ND data were analyzed only at the 24 h level. The RW showed strong agreement with VO for RT, with concordance correlation coefficients (CCC) of 0.98 (1 h) and 0.95 (24 h). In contrast, RT from ND showed poor agreement with VO (CCC = 0.12 for 24 h). Least squares means for RT (min/24 h) did not differ between VO (460 min) and RW (461 min), but ND significantly underestimated RT (211 min; p < 0.001). Both RW and ND performed poorly in detecting ET (CCC = 0.05 for RW and −0.15 for ND at 24 h). However, when time spent on both eating and other jaw movements was combined in VO, the combined time did not differ significantly from ET reported by RW (441 min vs. 454 min; p > 0.05), with improved agreement (CCC = 0.62). Cow, day, and their interaction had no significant effect on the deviation between VO and RW for RT (p > 0.05). Overall, these results indicate that RW accurately detects RT but tends to overestimate ET, whereas ND significantly underestimates both ET and RT with poor concordance in Hanwoo cows.

Palm kernel meal (PKM), the solvent-extracted counterpart of palm kernel expeller (PKE), is generated in growing volumes as the palm oil industry expands, yet remains underexploited as a sustainable feed resource for ruminants. This study evaluated its nutritive value and valorization potential for cattle. Eight commercial PKM sources were analyzed and compared with PKE, corn gluten feed, and beet pulp by in vitro ruminal fermentation. Major nutrients were consistent across sources, with coefficients of variation ≤3.1% for organic matter, neutral detergent fiber (NDF, 765 g/kg dry matter), and crude protein (185 g/kg), whereas ether extract (24 g/kg) and the insoluble fractions varied more widely. Amino acid and fatty acid profiles were similar to those of PKE. The 48 h NDF digestibility (NDFD) was significantly higher in PKM (71.9%, p < 0.05) than PKE (53.7%) and did not differ from beet pulp (63.6%). The total digestible nutrients, estimated from composition and NDFD, were numerically higher in PKM (68.3%) than PKE (63.6%) despite its lower fat content and similar to beet pulp (70.3%), attributed to its higher truly digestible NDF. PKM is a reliable non-forage fiber source for ruminant diets, and its valorization as a secondary feed resource reduces dependence on conventional feed ingredients.

This study evaluated the effects of expected progeny difference (EPD) grade and feeding system on carcass performance in Hanwoo steers using a large-scale field dataset collected under commercial production conditions. Records from 4561 steers (1466 fed total mixed fermented feed [TMF] and 3095 on a conventional separate-feeding system) across 269 farms in Korea from January 2023 to May 2025 were analyzed. Expected progeny difference grades for carcass weight (CWT), backfat thickness (BFT), ribeye area (REA), and marbling score (MBS) were classified A-D. Carcass performance significantly differed among EPD grades. Compared with grade D, grade A steers exhibited greater CWT (45.2 kg), less BFT (3.44 mm), greater REA (10.77 cm²), and greater MBS (1.57 units). Genetically superior animals reached slaughter age earlier. Steers fed TMF demonstrated higher CWT, BFT, REA, and MBS than conventionally fed steers. No significant interaction between EPD grade and feeding system was found for any carcass trait. These results indicate that EPD grades consistently predict carcass performance across different feeding environments, while TMF improves the absolute level of carcass traits. This large field dataset demonstrates that integrating Hanwoo EPD information with appropriate feeding management may support more efficient and profitable carcass production under commercial farm conditions.

Objective: The objective of this study was to investigate the effects of increasing dietary crude protein (CP) concentration on growth performance, rumen characteristics, blood metabolites, and methane (CH4) emissions in finishing Hanwoo steers.Methods: Twenty-four 26-month-old Hanwoo steers (717±50.1 kg) were utilized in a 12-week study based on a completely randomized block design. The animals were randomly assigned to one of four dietary treatments by feeding concentrate mixes with different CP levels (15.0%, 16.2%, 17.5%, and 18.5% on a dry matter [DM] basis). Forage was fed ad libitum, while the concentrate mix was provided in a fixed amount.Results: Forage and total dry matter intake (DMI) linearly increased (p≤0.029) with increasing CP levels while concentrate intake was not affected by treatments. Initial and final body weight and average daily gain were not different among treatments. Feed efficiency showed a trend of linear decrease (p = 0.092) with increasing CP levels. Rumen parameters, including ruminal pH, total volatile fatty acid, molar proportions of acetate, propionate, isobutyrate, butyrate, isobutyrate, valerate, and acetate to propionate ratio, were not affected by treatments. Treatments also did not affect blood concentrations of total protein, urea, glucose, non-esterified fatty acid, albumin, creatinine, triglyceride, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, calcium, and phosphorus. Concentrations of CH4 from respiration or eructation were not affected by dietary CP. CH4 ppm per DMI and neutral detergent fiber (NDF) intake was not also different among treatment in respiration or eructation. However, CH4 ppm per forage NDF intake linearly decreased (p≤0.005) with increasing CP from both respiration and eructation.Conclusion: These findings provide no clear evidence that increasing the CP content of the concentrate mix from 15.0% to 18.5% DM improves growth performance and body metabolism in finishing Hanwoo steers. Nevertheless, they suggest that a higher CP level may negatively affect feed efficiency.

Weight is the most basic and important indicator in cattle management, and automation of its measurement serves as a fundamental step toward modern smart livestock farming. Automated weighing systems (AWS) capable of continuously measuring cattle weight, even during movement, have been explored as key monitoring components in smart livestock farming. However, owing to the high measurement variability caused by environmental factors, the accuracy of AWSs has been questioned. These factors include real-time fluctuations due to animal activities (e.g., feeding and locomotion), as well as measurement errors caused by residual feed or excreta within the AWS. Therefore, this study aimed to develop an algorithm to enhance the reliability of steer weight measurements using an AWS, ensuring close alignment with actual cattle body weight. Accordingly, daily weight data from 36 Hanwoo steers were processed using a three-stage approach consisting of outlier detection and removal, weight estimation, and post-processing for weight adjustment. The best-performing algorithm that combined Tukey’s fences for outlier detection, mean-based estimation, and post-processing based on daily weight gain recommended by the National Institute of Animal Science achieved a root mean square error of 12.35 kg, along with an error margin of less than 10% for individual steers. Overall, the study concluded that the AWS measured steer weight with high reliability through the developed algorithm, thereby contributing to data-driven intelligent precision feeding.

Adequate but not excessive dietary energy supply is crucial for growth and productivity in cattle. This study aimed to evaluate the effects of three incremental changes in metabolizable energy (ME) levels in concentrate mixes, i.e., low (LEC, 10.4 MJ/kg DM), medium (MEC, 10.8 MJ/kg DM), and high (HEC, 11.0 MJ/kg DM), on growth performance and comprehensive physiological parameters in Hanwoo steers. Thirty steers, averaging 499 ± 38.0 kg, were randomly allocated to one of the treatments. Each steer received up to 8 kg of concentrate mix, with ad libitum access to tall fescue. Body weights were measured every four weeks. In week 12, rumen samples were collected, followed by fecal and blood samples. The HEC group exhibited a 16.5% higher average daily gain compared to the other groups (p = 0.035). Forage and total dry matter (DMI) were 46% and 12% lower in the HEC group (p < 0.001). Fiber digestibility increased with energy content (p < 0.05). Total volatile fatty acid and the acetate-to-propionate ratio decreased in the HEC group (p < 0.001), while blood creatinine concentration increased (p < 0.01). In conclusion, feeding Hanwoo steers with a high-energy concentrate mix (up to 11.0 MJ ME/kg DM) improved growth and feed efficiency without compromising rumen health.

Adequate but not excessive dietary energy supply is crucial for growth and productivity in cattle. This study aimed to evaluate the effects of three incremental metabolizable energy (ME) levels in concentrate mixes: low (LEC, 10.4 MJ/kg DM), medium (MEC, 10.8 MJ/kg DM), and high (HEC, 11.0 MJ/kg DM) on growth performance and comprehensive physiological parameters in Hanwoo steers. Thirty steers, averaging 499 ± 38.0 kg, were randomly allocated to one of the treatments. Each steer received up to 8 kg of concentrate mix, with ad libitum access to tall fescue. Body weights were measured every four weeks. In week 12, rumen samples were collected, followed by fecal and blood samples. The HEC group exhibited a 16.5% higher average daily gain compared to the other groups (p = 0.035). Forage and total dry matter (DMI) were 46% and 12% lower in HEC (p < 0.001). Fiber digestibility increased with energy content (p < 0.05). Total volatile fatty acid and the acetate-to-propionate ratio decreased in HEC (p < 0.001), while blood creatinine concentration increased (p < 0.01). In conclusion, feeding Hanwoo steers with a high-energy concentrate mix (up to 11.0 MJ ME/kg DM) improved growth and feed efficiency without compromising rumen health.

Objective: This study investigated the repeatability of feed efficiency and its association with carcass traits in Hanwoo steers during the entire growing and fattening periods.Methods: The growth and intake of thirty-six Hanwoo steers (259±19.7 kg; nine months) were monitored throughout five periods, including two growing periods (GP) and three fattening periods (FP). The steers were fed two types of concentrate mixes with varying nutrient compositions until they reached a target weight of 800 kg for slaughter. For each period, steers were categorized into three classes based on their feed efficiency rankings using residual feed intake (RFI) and feed conversion ratio (FCR). Feed efficiency repeatability was assessed using the Spearman correlation coefficient, decomposition of random errors, and the Theil segregation index (TSI). The Pearson correlation coefficient was used to examine the relationship between feed efficiency and carcass traits.Results: The results demonstrated a significant and high correlation with RFI, but not FCR, during the growing or fattening stages (r>0.5; p<0.01). When steers were classified according to their feed efficiency rankings, 58% of the animals in the high RFI class (low efficient) initially (GP 1) remained in the same class by the last period (FP 3), whereas steers were randomly distributed based on FCR. The repeatability, assessed by the decomposition of random errors, was higher for RFI (0.61) than for FCR (0.15). The TSI also indicated that RFI rankings, rather than FCR rankings, are more likely to be maintained. Moreover, a weak association was observed between feed efficiency and carcass traits.Conclusion: In conclusion, RFI repeatability throughout the GP and FP surpassed that of the FCR, with steers classified as high RFI during the GP more likely to remain in the same class during the FP. Feed efficiency was weakly correlated with carcass traits.

This study aimed to investigate the effect of varying levels of dietary crude protein (CP) on growth performance, rumen characteristics, blood metabolites, and methane emissions in fattening Hanwoo steers. Twenty-four steers, weighing 504 ± 33.0 kg (16 months old), were assigned to four dietary treatments with different CP concentrations (15, 18, 19, and 21% of CP on a dry matter (DM) basis). A linear increasing trend in the average daily gain (ADG) was observed (p = 0.066). With increased dietary CP levels, the rumen ammonia concentration significantly increased (p < 0.001), while the propionate proportion linearly decreased (p = 0.004) and the proportions of butyrate and valerate linearly increased (p ≤ 0.003). The blood urea exhibited a linear increase (p < 0.001), whereas the blood non-esterified fatty acids and cholesterol showed a linear decrease (p ≤ 0.003) with increasing dietary CP. The methane concentration from eructation per intake (ppm/kg), forage neutral detergent fiber (NDF) intake, total NDF intake, and ADG exhibited linear decreases (p ≤ 0.014) across the treatments. In conclusion, increasing the dietary CP up to 21% in concentrates demonstrated a tendency to linearly increase the ADG and significantly decrease the propionate while increasing the butyrate. The methane concentration from eructation exhibited a tendency to linearly decrease with increasing dietary CP.