Genetic Selection for Improved Profit Conditioned on Enterprise-Specific Circumstances

Abstract Circumstances of producers relative to objectives, economic constraints, and production environments differ substantially. Consequently, the specific path of sustainability differs among beef enterprises. Such a path must take a supply-chain approach, contemplating market (consumer) demands, and firm-level economic costs and returns in both the short- and long- term. Long-term economic returns imply longer-term stewardship of natural resources. Genetic selection is uniquely poised to aid in the pursuit of greater economic and biological efficiency, given it represents a cumulative and permanent source of change. However, it is critical that such change be consistent with the producer-specific sustainability path. Given there are multiple traits that impact economic outcomes economic selection indexes are the appropriate tool. The general form of such indexes has been around for about 80 years, albeit with a less than desirable adoption rate in beef selection decisions. The process of index development can account for known sensitivities to differences in marketing endpoints and current levels of phenotypic performance. Moreover, the time horizon used to determine the economic consequences of a selection decision could differ among enterprises. The choice of planning horizon (PH) is an important, yet often overlooked component of breeding objective and index construction. Shorter PH inherently emphasizes traits that can be fully expressed in the near term whilst longer PH allow more substantial weighting of traits expressed later in life. Misalignment of breeding objectives and selection indexes, as might be the case in using a terminal index to choose sires in a self-replacing herd, or incorrect choice of PH could lead to less profitable genetic selection decisions by increasing mature cow weight and/or de-emphasizing reproductive longevity. Consequently, our objective was to provide examples of how trait emphasis might be altered under different assumptions during selection index development using the web-based tool iGENDEC. Indexes assumed replacement females were retained and terminal animals were retained through harvest. We then compared changes in PH, annual cow variable costs, and phenotypic means of hot carcass weight (HCW). The combined relative emphasis (RE) of mature cow weight (MWT) and stayability (STAY) in the breeding objective was 0, 10, and 22% when planning horizon was 2, 10, and 20 years, respectively. As HCW increased from 318 to 408 kg the RE of STAY increased from 10.9% to 18.7% while the RE of HCW decreased from 43.8% to 28.9%. When annual cow variable costs were $250, $500, and $750 the RE of MWT was 6, 14.9, and 22.5%, respectively, assuming the value of calves sold stayed the same. Collectively, these examples illustrate that incorrect definition of breeding objectives and parametrization of indexes can lead to inappropriate weighting of traits that are drivers of long-term resource use (i.e., MWT and STAY).