23 Sustainable Livestock Breeding with a Focus on Heat Stress

Abstract The genetic selection is a form of optimization. Traits in explicit or implicit index are improved, while other traits change according to correlations among the traits. After long selection, usually production improve fitness deteriorate. At gene level, it seems that genes associated with positive effects on major tend fixation, and remaining large effect exhibit pleiotropy. While for moderately successful because small heritability, constantly improving management counterbalances deterioration Treating as an optimization raises question about limits, particular feed conversion. Latest experiences suggest eventually strong residual intake reduces fertility increases late mortality. environment changes, climate having profound effect. industry faces choice either breeding new conditions devising managemental modifications. depends species can be more easily improved animals confinement raised intensive (pigs, broilers, dairy cattle), but less pasture (beef cattle sheep). financials speed. An interesting example such trade-off approach mitigate heat stress, which results plummeting fertility, decreased milk yield, premature culling leading insufficient replacements. To counter these challenges, methodology evaluation tolerance was developed applied US national data Holsteins. Instead genetics, implemented modifications: cooling devices, timed AI increased use sexed semen. In pigs chicken, response stress nucleus stronger commercial environment, performance paramount. summary, mitigations involve combination environmental factors.