Background: South Korea has recently faced record-high temperatures, which have adversely affected dairy production. Holstein cows, the primary dairy breed globally, are particularly sensitive to heat stress. In contrast, Jersey cows have shown greater heat tolerance, as demonstrated by phenotypic studies. Methods: We investigated physiological and molecular responses to heat stress in Holstein and Jersey cows by measuring rectal temperature, milk yield, and average daily gain, confirming Holstein cows’ greater vulnerability. To explore molecular mechanisms, we analyzed circulating microRNA profiles from whole blood samples collected under heat stress and normal conditions using microRNA-sequencing. Differential expression patterns were compared between the two breeds to identify biological pathways associated with heat stress. Results: Four microRNAs (bta-miR-20b, bta-miR-1246, bta-miR-2284x, and bta-miR- 2284y) were significantly differentially expressed in both breeds under heat stress (|FC| ≥ 2, p < 0.05). Notably, bta-miR-20b and bta-miR-1246 were linked to corpus luteum function and progesterone biosynthesis, while bta-miR-2284x and bta-miR- 2284y were associated with immune responses. A comparison of 11 potential heat stress-related microRNAs identified in previous studies of Holstein cows revealed consistent expression trends in Jersey cows, albeit with lower fold changes, suggesting their superior heat resilience. Conclusions: Our study highlights the physiological and microRNA-based differences in heat stress responses between Holstein and Jersey cows. Jersey cows exhibited greater resilience, supported by more stable microRNA expression profiles and improved heat stress indicators, making them a promising breed for dairy production in increasingly hot climates.

This study was conducted to clarify behavior and body weight of weaned piglets between different social experiences during suckling period. Control (no social experience) and treatment (social experience) groups of weaned piglets were housed and observed with the aid of video technology for 8 consecutive hours in early (days 1 and 2) and late (days 22 and 23) periods after mixing. Inactive, locomotion and exploration were significantly different between control and treatment groups in early mixed period. Feeding differed between groups in late mixed period. In social behaviors, agonistic and interaction with adjacent pen were significantly higher in treatment group than in control group during early mixed period. However, social behaviors dramatically decreased in late mixed period. There was negative correlation between average daily gain of body weight and agonistic behavior. In social experienced weaned piglet groups, there were less agonistic behavior and more daily gain of body weight in this study. Social experience during suckling period would be useful for stable group management in swine industry.

본 연구의 목적은 한우 도체형질과 등심에 대한 일반성분(수분, 조지방, 조단백질, 조회분) 분석을 통 한 등심의 영양학적 가치와 유전모수 추정을 통한 개량형질 적용 가능성을 확인하기 위하여 실시하였 다. 본 연구에 이용된 공시 재료는 한우 후대검정우 47차부터 57차까지 실시한 2,033두에 대하여 등심 1㎏을 시료를 채취하여 분석한 자료를 이용하였다. 연구결과 한우 도체형질인 도체중, 등심단면적, 등 지방두께, 근내지방도에 대한 유전력은 각각 0.37, 0.51, 0.44, 0.57로 추정되었으며, 일반성분 분석인 수분, 조지방, 조단백질, 조회분에 대한 유전력은 각각 0.62, 0.64, 0.58, 0.12로 추정되었다. 그리고, 도체형질과 일반성분간의 유전상관은 도체중과 조지방에서 0.35, 근내지방도와 수분, 조지방, 조단백 질, 조회분에서 각각 -0.966, 0.964, -0.924, -0.664으로 고도의 유전상관을 보였다. 수분과 조지방, 조단백질간의 유전상관은 각각 -0.998, 0.969로 분석되었으며, 조지방과 조단백질에서 -0.979로 고도 의 유전상관을 보였다. 일반성분 분석치인 수분, 조지방, 조단백질에서 고도의 유전력을 보였으므로, 개 량형질 이용 가능성이 있을 것으로 사료된다.

The objective of this study was to estimate genetic parameters for 18 linear conformation traits and overall conformation score in Holstein cattle. A total of 376,606 records for type traits were collected from 2001 to 2011 from Korea Animal Improvement Association. The model of estimation of variance components and correlations among lactations using VCE included both fixed effects (herd-year-season and stage of lactation parity-wise) and random effect (animal additive genetic). The estimated heritabilities (h2) for capacity class, such as stature, chest width, body depth, angularity, and body condition score were 0.32, 0.16, 0.27, 0.12, and 0.19, respectively. Rump angle and width from rump class also showed h2 of 0.31 and 0.17, respectively. The heritabilities in udder class were mostly low to medium; in which traits were fore udder attachment (0.13), rear udder height (0.17), udder support (0.11), udder depth (0.33), front teat placement (0.17), front teat length (0.21), and rear teat placement (0.21). For feet and legs composite class, the estimated heritabilities for rear leg set, foot angle, rear leg rear view, and locomotion were 0.12, 0.07, 0.08, and 0.03, respectively. The h2 estimated for overall conformation score was 0.16 in the study. The genetic and environmental variance components estimated from this study would be helpful to change from single lactation animal models to multiple lactation animal models in the national genetic evaluation system for the improvement of linear type traits. Moreover, The breeding values obtained using these variance components would be able to be used in the calculation of Korean type production index (KTPI), udder composite (UDC) and, feet and legs composite (FLC).

The objectives of this study were to estimate genetic parameters for 10 linear conformation traits and final score in Hanwoo cows. A total of 53,277 records for type traits of Hanwoo cows were collected from 2008 to 2012 from Korea Animal Improvement Association. Ten linear traits studied were stature, body length, chest depth, body rump angle, rump length, pin bone width, udder volume, foot angle, rear legs side view, and rear legs rear view. The model included the fixed effects of herd-year-classifier, age at measurement and age after calving, the random animal additive genetic effect and residual effect. Heritability estimates for linear type traits were ranged from 0.003 for rear legs side view to 0.213 for final score. Genetic correlations among linear type traits were ranged from -0.068 (for rear legs side view and rear legs rear view) to 0.982 (for body length and rump length). The final score was found to be in a strongest genetic correlation with rear legs rear view (0.947), followed by pin bone width (0.918), body length (0.887), rump length (0.883), chest depth (0.883), udder volume (0.811), stature (0.802), rump angle (0.637), foot angle (0.519) and rear legs side view (0.176). Corresponding phenotypic correlations for pairs of linear type traits were mostly similar in direction, but smaller than the genetic correlations.

The objective of this study was to estimate genetic parameters on days to 90 kg body weight and ultrasound measured traits (back fat thickness, eye muscle area, retail cut percentage) and predict genetic progress when the weights for selection on the paternal traits of Duroc, which can be incorporated into sire line selection indexes. A simulation program, ZPLAN+, was used for the simulation. Genetic parameters of days to 90 kg body weight (D90KG), back fat thickness (BFT), eye muscle area (EMA) and retail cut percentage (RCP) used in the simulation were estimated from 27,972 heads of farm tested Duroc pigs from 2005 to July, 2012. Parameters of simulation used genetic parameters with parturition rates, ratios of test pigs and replacement rates that were dependent on selection protocols of simulated farms. Different weights of selection for traits of days to 90 kg and backfat thickness were compared. Estimates of heritability were 0.406, 0.355, 0.159 and 0.379 for D90KG, BFT, EMA and RCP, respectively. Genetic correlation of D90KG with BFT, EMA and RCP were –0.043, 0.049 and 0.021, respectively. Genetic correlation of BFT with EMA and RCP were –0.394 and –0.937. And genetic correlation between EMA with RCP were 0.524. Simulation result showed that index weight of 3:1 on D90KG and BFT was effective to shorten days to 90 kg without any significant changes in backfat thickness. Generally the genetic changes were greater as parturition rate and ratios of test pigs increased. Increase in replacement rate had a small effect on genetic changes in negative way. Thus, we recommend that index weight of 3:1 on days to 90 kg and backfat thickness could be utilized for sire line selection.