This study aimed to determine the factors affecting the body weight (BW) of Hanwoo steers by collecting a large number of BW measurements using an automated weighing system (AWS). The BW of 12 Hanwoo steers was measured automatically using an AWS for seven days each month over three months. On the fourth day of the BW measurement each month, an additional BW measurement was conducted manually. After removing the outliers of BW records, the deviations between the AWS records (a) and manual weighing records (b) were analyzed. BW measurement deviations (a − b) were significantly (p < 0.05) affected by month, day and the time within a day as well as the individual animal factor; however, unexplained random variations had the greatest impact (70.4%). Excluding unexplained random variations, the difference between individual steers was the most influential (80.1%). During the day, the BW of Hanwoo steers increased before feed offerings and significantly decreased immediately after (p < 0.05), despite the constant availability of feeds in the feed bunk. These results suggest that there is a need to develop pattern recognition algorithms that consider variations in individual animals and their feeding patterns for the analysis of BW changes in animals.

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.

This study investigated the effect of different dietary fat levels in concentrate mixes on the growth performance, rumen characteristics, digestibility, blood metabolites, and methane emissions in growing Hanwoo steers. Thirty steers (386 ± 24.6 kg of body weight [BW]; 12 months old), blocked by BW, were randomly assigned to three dietary treatments with varying fat concentrations in concentrate mix (48, 74, and 99 g of ether extract per kg dry matte [DM]). The fat intake of the low-fat treatment represented 4.15% of the total dry matter intake (DMI), while the medium- and high-fat treatments accounted for 5.77% and 7.23% of total DMI, respectively. Concentrate mix DMI decreased with increasing fat level (p < 0.01). The growth rate and digestibility did not significantly differ based on the fat level (p > 0.05). As the fat level increased, propionate in the total ruminal volatile fatty acids increased, and butyrate and acetate-to-propionate decreased (p < 0.01). Cholesterol in blood serum increased significantly with increasing dietary fat levels (p < 0.01). Methane emissions exhibited a linear decrease with increasing fat level (p < 0.05). In conclusion, elevating fat content in the concentrates up to 100 g/kg DM reduced methane emissions without compromising the growth performance of growing Hanwoo steers.

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.

An automatic concentrate feeding system (ACFS) divides the day into several intervals, allowing cattle to consume a predetermined amount of concentrate mix per interval. This study investigated the impact of changing these intervals (four vs. six) in an ACFS on its precision in monitoring the feed intake and feeding behavior of fattening Hanwoo steers. The experiment, involving 29 fattening Hanwoo steers (688 ± 43.3 kg of body weight, 24 months old), employed a switchback design with two interval settings: four and six per day. Both individual forage and concentrate intakes and feeding behaviors were automatically recorded; however, the ACFS measured feed supply, not actual intake. The precision of the ACFS’s intake recordings was tested by manually assessing feed residuals per visit using video recordings. Although no difference was observed in the concentrate intake (p > 0.05), the six-interval setting reduced concentrate residuals by 0.2 kg per visit (p < 0.05). The increased interval setting also resulted in fewer visits for forage consumption and decreased forage and total dry matter intakes (p < 0.05). In conclusion, the increased interval setting for the ACFS reduced the visit frequency for forage consumption and actual forage consumption while improving the precision of the ACFS’s intake recordings.

Objective: Ulva sp., a blooming macroalgae causing the green tide in Korea, has been suggested as a feed ingredient for ruminant livestock. The objective of this study was to investigate the effects of 3% dry matter inclusion of Ulva sp. in a total mixed ration (TMR) on milk production, methane emitting potential, and physiological parameters in lactating Holstein cows.Methods: A total of 36 cows were allocated into two groups considering milk production, parity, days in milk, and methane production concentration from respiration and eructation, and fed the TMR with or without 3% dry matter inclusion of Ulva sp. for 4 weeks. Methane emitting potential was measured using a laser methane detector in week 4, and feed, milk, and blood were collected every 2 weeks.Results: Ulva sp. inclusion did not affect methane production concentration from respiration and eructation, but tended to decrease the methane intensity concentration from respiration (p = 0.06) and eructation (p = 0.06). In addition, it increased the milk fat yield, energy-corrected milk, and net energy for lactation in week 2, but this did not persist to week 4, indicating the interaction between treatment and week (p<0.05). Likewise, it increased milk urea nitrogen, blood urea nitrogen, and white blood cell counts in week 2 but not in week 4 (p<0.05). Cortisol concentration in hair tended to decrease with Ulva sp. inclusion (p<0.10), whereas the serum total antioxidant capacity and uric acid were not affected.Conclusion: It was demonstrated that Ulva sp. can be utilized as a feed ingredient for lactating cows without any adverse effects on milk production, complete blood cell counts, or blood metabolites. The potential methane-reducing property of Ulva sp. should be further investigated in future studies.