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Genetic selection for improved feed efficiency and lean growth in pigs has resulted in reduced intramuscular fat content. The aim of this study was to evaluate growth performance, carcass traits, and meat quality in genetically lean immunocastrated pigs grouped based on divergent Warner-Bratzler Shear Force (WBSF) values. The WBSF values of the longissimus lumborum (LL) muscle were obtained from a previous trial evaluating 4 diets, 6 replicates per diet, and 3 pigs per pen, summing up to 72 Large White immunocastrated male pigs. Pigs (initial BW = 28.44 ± 2.95 kg) were fed diets containing either 1.5% soybean oil (CON) or 3% soybean oil (SO), canola oil (CO), or fish oil (FO) in a 98-d study. The original dataset was used to segregate pigs into 2 treatments: high (5.4 to 4.3 kg) and low (3.8 to 2.8 kg) WBSF. The SO diet did not show extreme values for WBSF and was not included in the resulting dataset, which comprised 2 treatments (high- and low-WBSF), 3 blocks (CON, CO, and FO), and 6 replicates per treatment (12 experimental units). No significant differences were observed for growth performance between WBSF groups. When compared with low-WBSF pigs, high-WBSF pigs tended to have decreased (P = 0.07) backfat thickness and intramuscular fat content in the LL and greater (P = 0.09) carcass lean percentage and cooking losses. Oleic acid concentration was less (P = 0.05) in the LL intramuscular fat of high- than low-WBSF pigs. There were statistical tendencies for decreased (P = 0.06) total monounsaturated fatty acids and increased (P = 0.09) total polyunsaturated fatty acids concentrations in the LL intramuscular fat of high- than low-WBSF pigs. In conclusion, immunocastrated male pigs with tender meat had improved nutritional attributes of pork, with no effects on feed efficiency and carcass traits.

Heat stress will become a more substantial issue for swine production as global temperatures continue to rise. Efforts have been made to mitigate the negative impacts of heat stress through advances in genetic selection, nutrition, precision technology, and management practices. However, heat stress is still a limiting factor to swine production that must be addressed. A key aspect to mitigating heat stress-related production losses in swine may be developing better management approaches and genetic selection techniques to improve heat stress resilience. This is especially true for heat stress sensitive populations such as gestating and lactating sows. Gestating and lactating sows are considered heat stress sensitive due to greater metabolic heat production resulting from fetal growth and milk production, respectively. Additionally, swine offspring are adversely affected by in utero heat stress, which imprints long-term negative phenotypes that reduce health and productivity regardless of environmental conditions. To address these concerns, swine producers have implemented a variety of cooling and management strategies to mitigate heat stress. However, the recommended or perceived heat stress temperature thresholds for implementation may not accurately reflect the thermal requirements of modern swine with current genetics or at variable gestation stages leading to ineffective use. As such, a re-evaluation of heat stress thresholds for modern swine is warranted. Additionally, genetic selection for productivity traits (e.g., litter sizes and lean growth) has increased metabolic heat production resulting in increased heat stress sensitivity. Therefore, the ability to perform large-scale measures of and implement heat stress tolerance traits within breeding populations may be advantageous for producers to improve heat stress resilience within their herds. Taken together, as heat stress becomes a greater issue for the swine industry, it will become increasingly important to develop sustainable approaches that improve swine heat stress resilience while maintaining or improving producer profitability.