406 Bridging the gap between feedlot and pasture: comparing production phenotypes of cattle in both dry lot and grazing systems.

Abstract Phenotypic testing in cattle is essential for evaluating traits related to growth performance, feed efficiency, and water intake. Traditional phenotypic evaluations occur primarily in dry lot-based systems; however, pasture-based systems are the predominant setting for commercial beef production. Therefore it is necessary to assess whether performance rankings from dry lot systems are reflective of what is observed in grazing systems. Understanding the degree of correlation between these systems is crucial for improving the accuracy of genetic evaluations and refining selection strategies for economically important traits. Our study utilizes Vytelle In-Pen Weighing (IPW) systems to measure body weight and individual water intake in confinement settings, alongside Vytelle feed bunks to quantify individual dry matter intake (DMI). To extend this evaluation to a grazing-based system, we implemented a mobile IPW to measure body weight and individual water intake, from which we can determine individual daily DMI. These technologies allow for a direct comparison of performance traits of cattle in both dry lot and pasture-based systems. We evaluated two groups of heifers in both the dry lot and grazing systems sequentially and analyzed the consistency of individual rankings for three key efficiency traits: Residual Feed Intake (RFI), Average Daily Gain (ADG), and DMI across both testing environments. Preliminary results indicate a weak correlation in ADG rankings (r = -0.179, and 0.083) between the yearling crossbred and purebred heifers, suggesting that growth performance can differ between the management conditions. Similarly, DMI rankings exhibited weak correlations (r = -0.006, and 0.121), indicating that feed intake tendencies observed in confinement do not persist in pasture environments. RFI rankings displayed a similar variability (r = 0.344), reflecting potential environmental influences on feed efficiency measures. Differences in forage availability, grazing behavior, and energy expenditures may contribute to these discrepancies, pointing to the importance of evaluating animals in the kind of system in which they will be expected to perform. These findings indicate that performance traits like ADG, DMI and RFI can be assessed in either system; however, the resultant phenotypes likely only apply to that environment. The application of mobile weighing systems and predictive algorithms offers promising advancements in extending phenotypic testing beyond traditional dry lot settings. However, further refinement of predictive models and additional data collection are necessary to improve the accuracy of efficiency trait evaluation in grazing systems. By comparing performance trait rankings across environments, this study enhances our understanding of how phenotypic testing conditions influence genetic evaluation outcomes. Integrating pasture-based phenotypic testing into genetic selection programs may improve the ability to select cattle with superior efficiency and productivity in real-world grazing conditions. Future research should focus on refining pasture-based intake measurement methodologies and exploring genetic-by-environment interactions that impact feed efficiency rankings.