Repeatability of feed efficiency and its relationship with carcass traits in Hanwoo steers during their entire growing and fattening period.

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 growing and fattening periods 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.

Effects of Dietary Crude Protein Level of Concentrate Mix on Growth Performance, Rumen Characteristics, Blood Metabolites, and Methane Emissions in Fattening Hanwoo Steers.

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.

Effects of Dietary Fat Level of Concentrate Mix on Growth Performance, Rumen Characteristics, Digestibility, Blood Metabolites, and Methane Emission in Growing Hanwoo Steers.

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.

Effect of the Meal Interval Setting of an Automated Concentrate Feeding System on Feed Intake and Feeding Behavior in Fattening Hanwoo Steers.

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.

Application of a hand-held laser methane detector for measuring enteric methane emissions from cattle in intensive farming.

The hand-held laser methane detector (LMD) technique has been suggested as an alternative method for measuring methane (CH4) emissions from enteric fermentation of ruminants in the field. This study aimed to establish a standard procedure for using LMD to assess CH4 production in cattle and evaluate the efficacy of the protocol to detect differences in CH4 emissions from cattle fed with diets of different forage-to-concentrate (FC) ratios. Experiment 1 was conducted with four Hanwoo steers (584 ± 57.4 kg body weight [BW]) individually housed in metabolic cages. The LMD was installed on a tripod aimed at the animal's nostril, and the CH4 concentration in the exhaled gas was measured for 6 min every hour for 2 consecutive days. For the data processing, the CH4 concentration peaks were identified by the automatic multi-scale peak detection algorithm. The peaks were then separated into those from respiration and eructation by fitting combinations of two of the four distribution functions (normal, log-normal, gamma, and Weibull) using the mixdist R package. In addition, the most appropriate time and number of consecutive measurements to represent the daily average CH4 concentration were determined. In experiment 2, 30 Hanwoo growing steers (343 ± 24.6 kg BW), blocked by BW, were randomly divided into three groups. Three different diets were provided to each group: high FC ratio (35:65) with low-energy concentrate (HFC-LEC), high FC ratio with high-energy concentrate (HFC-HEC), and low FC ratio (25:75) with high-energy concentrate (LFC-HEC). After 10 d of feeding the diets, the CH4 concentrations for all steers were measured and analyzed in duplicate according to the protocol established in experiment 1. In experiment 1, the mean correlation coefficient between the CH4 concentration from respiration and eructation was highest when a combination of two normal distributions was assumed (r = 0.79). The most appropriate measurement times were as follows: 2 h and 1 h before, and 1 h and 2 h after morning feeding. Compared with LFC-HEC, HFC-LEC showed 49% and 57% higher CH4 concentrations in exhaled gas from respiration and eructation (P < 0.01). In conclusion, the LMD method can be applied to evaluate differences in CH4 emissions in cattle using the protocol established in this study.

The hand-held laser methane detector (LMD) technique has been suggested as a potential method for measuring methane (CH4) emissions from enteric fermentation of ruminants in the field. This study aimed to establish a standard procedure for using LMD to assess CH4 production in cattle and evaluate the efficacy of the protocol to detect differences in CH4 emissions from cattle fed with diets of different forage-to-concentrate (FC) ratios which is known to affect CH4 emissions. Experiment 1 was conducted to establish a protocol for measuring and analyzing the CH4 emissions from cattle using LMD. In experiment 2, 30 Hanwoo growing steers were divided into three groups and fed with a diet of high FC ratio (35:65) with low-energy concentrate (HFC-LEC), high FC ratio (35:65) with high-energy concentrate (HFC-HEC), or low FC ratio (25:75) with high-energy concentrate (LFC-HEC). The CH4 concentrations for all steers were measured in duplicate according to the protocol established in experiment 1. HFC-LEC showed 49% and 57% higher CH4 concentrations in exhaled gas from respiration and eructation, respectively (P < 0.01), than LFC-HEC. In conclusion, the LMD method can be applied to evaluate differences in CH4 emissions in cattle using the protocol established in this study.

Development of a model to predict dietary metabolizable energy from digestible energy in beef cattle.

Understanding the utilization of feed energy is essential for precision feeding in beef cattle production. We aimed to assess whether predicting the metabolizable energy (ME) to digestible energy (DE) ratio (MDR), rather than a prediction of ME with DE, is feasible and to develop a model equation to predict MDR in beef cattle. We constructed a literature database based on published data. A meta-analysis was conducted with 306 means from 69 studies containing both dietary DE and ME concentrations measured by calorimetry to test whether exclusion of the y-intercept is adequate in the linear relationship between DE and ME. A random coefficient model with study as the random variable was used to develop equations to predict MDR in growing and finishing beef cattle. Routinely measured or calculated variables in the field (body weight, age, daily gain, intake, and dietary nutrient components) were chosen as explanatory variables. The developed equations were evaluated with other published equations. The no-intercept linear equation was found to represent the relationship between DE and ME more appropriately than the equation with a y-intercept. The y-intercept (-0.025 ± 0.0525) was not different from 0 (P = 0.638), and Akaike and Bayesian information criteria of the no-intercept model were smaller than those with the y-intercept. Within our growing and finishing cattle data, the animal's physiological stage was not a significant variable affecting MDR after accounting for the study effect (P = 0.213). The mean (±SE) of MDR was 0.849 (±0.0063). The best equation for predicting MDR (n = 106 from 28 studies) was 0.9410 ( ± 0.02160) +0.0042 ( ± 0.00186) × DMI (kg) - 0.0017 ( ± 0.00024) × NDF(% DM) - 0.0022 ( ± 0.00084) × CP(% DM). We also presented a model with a positive coefficient for the ether extract (n = 80 from 22 studies). When using these equations, the observed ME was predicted with high precision (R2 = 0.92). The model accuracy was also high, as shown by the high concordance correlation coefficient (>0.95) and small root mean square error of prediction (RMSEP), <5% of the observed mean. Moreover, a significant portion of the RMSEP was due to random bias (> 93%), without mean or slope bias (P > 0.05). We concluded that dietary ME in beef cattle could be accurately estimated from dietary DE and its conversion factor, MDR, predicted by the dry matter intake and concentration of several dietary nutrients, using the 2 equations developed in this study.

Analysis of the Factors Influencing Body Weight Variation in Hanwoo Steers Using an Automated Weighing System.

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.