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This study aims to estimate the connectedness rating (CR) of Korean swine breeding herds. Using 104,380 performance and 83,200 reproduction records from three swine breeds (Yorkshire, Landrace and Duroc), the CR was estimated for two traits: average daily gain (ADG) and number born alive (NBA) in eight breeding herds in the Republic of Korea (hereafter, Korea). The average CR for ADG in the Yorkshire breed ranges from 1.32% to 28.5% depending on the farm. The average CR for NBA in the Yorkshire herd ranges from 0% to 12.79%. A total of 60% of Yorkshire and Duroc herds satisfied the preconditions suggested for genetic evaluation among the herds. The precondition for the genetic evaluation of CR for ADG, as a productive trait, was higher than 3% and that of NBA, as a reproductive trait, was higher than 1.5%. The ADG in the Yorkshire herds showed the highest average CR. However, the average CR of ADG in the Landrace herds was lower than the criterion of the precondition. The prediction error variance of the difference (PEVD) was employed to assess the validation of the CR, as PEVDs exhibit fluctuations that are coupled with the CR across the herds. A certain degree of connectedness is essential to estimate breeding value comparisons between pig herds. This study suggests that it is possible to evaluate the genetic performance together for ADG and NBA in the Yorkshire herds since the preconditions were satisfied for these four herds. It is also possible to perform a joint genetic analysis of the ADG records of all Duroc herds since the preconditions were also satisfied. This study provides new insight into understanding the genetic connectedness of Korean pig breeding herds. CR could be utilized to accelerate the genetic progress of Korean pig breeding herds.

ABSTRACT: Selenium is a heat-stress-reducing substance that improves heat resistance and is being studied for its effective application in the broiler industry. However, research on feed additives is labor-intensive and time-consuming because of the need for feeding experiments. We aimed to compare the effects of selenium under heat stress in vitro and in ovo, specifically examining the gene expression of heat shock proteins (HSP) and inflammatory markers. Two groups were included in the in-vitro study: in-vitro control (TC; selenium 0 μg/ml) and in-vitro selenium (TS; selenium 5 μg/ml). The satellite cells were cultured at 42°C for 48 h after selenium treatment. The in-ovo study comprised 4 groups: in-ovo control and in-ovo selenium 1-3 (OC, OS1, OS2, and OS3; selenium 2.5, 5, and 10 μg/egg, respectively). Selenium was injected on the 18th day after hatching, and heat treatment was performed at 32–34°C from the 14th to the 21st day after hatching, and the leg muscles of the chicks were collected on the 21st day. The gene expression of heat shock proteins (HSP), caspase3, nuclear factor kappa light-chain enhancer of activated B cells (NF-kB), and IL-8 was analyzed in in-vitro and in-ovo experiments, respectively. In-vitro results showed significant increases in HSP90, HSP60, and HSP40 in TS compared to TC, with a significant decrease in HSP70. In the in-ovo study, HSP70, caspase3, NF-kB and IL-8 were significantly increased in OS1. HSP90, HSP60, HSP40, HSP27 and NF-kB were significantly decreased in in-ovo OS2 compared to in-vitro TS, implying a trend in ratio compared to control. Selenium appeared to enhance heat resistance in-vitro and in-ovo by modulating HSPs and inflammation. However, differences in mRNA expression were observed depending on the concentration of selenium. These findings suggest that selenium modulates heat resistance through different mechanisms in-vitro and in-ovo, likely due to the complexity of whole-organism interactions in-ovo compared to the single-cell-type environment in-vitro. Therefore, to directly apply in-vitro results to in-ovo, a concentration comparison study for each additive is necessary.