Published online by Cambridge University Press: 23 November 2017
Selection for increased milk production may have resulted in the “shift” in nutrient partitioning towards milk production away from maintenance of functional fitness. This has led to the conclusion that dairy cows appear to be less ‘robust’ than in the past. The current national index, £PLI, combines the predicted transmitting ability (PTA) for production and functional traits, multiplied by their relative economic values, with the overall goal of maximising cow profit. Stott et al. (2005) updated economic weights for £PLI, increasing the relative weight on functional traits, but showed that the genetic responses in functional traits were still expected to decline, albeit at a slower rate compared to selection on production alone. The aim of this work is to develop a Robustness Index for UK dairy cattle that halts the predicted genetic decline in health and fertility traits using a restricted index approach.