Review: Deciphering animal robustness. A synthesis to facilitate its use in livestock breeding and management

Abstract

As the environments in which livestock are reared become more variable, animal robustness becomes an increasingly valuable attribute. Consequently, there is increasing focus on managing and breeding for it. However, robustness is a difficult phenotype to properly characterise because it is a complex trait composed of multiple components, including dynamic elements such as the rates of response to, and recovery from, environmental perturbations. In this review, the following definition of robustness is used: the ability, in the face of environmental constraints, to carry on doing the various things that the animal needs to do to favour its future ability to reproduce. The different elements of this definition are discussed to provide a clearer understanding of the components of robustness. The implications for quantifying robustness are that there is no single measure of robustness but rather that it is the combination of multiple and interacting component mechanisms whose relative value is context dependent. This context encompasses both the prevailing environment and the prevailing selection pressure. One key issue for measuring robustness is to be clear on the use to which the robustness measurements will employed. If the purpose is to identify biomarkers that may be useful for molecular phenotyping or genotyping, the measurements should focus on the physiological mechanisms underlying robustness. However, if the purpose of measuring robustness is to quantify the extent to which animals can adapt to limiting conditions then the measurements should focus on the life functions, the trade-offs between them and the animal's capacity to increase resource acquisition. The time-related aspect of robustness also has important implications. Single time-point measurements are of limited value because they do not permit measurement of responses to (and recovery from) environmental perturbations. The exception being single measurements of the accumulated consequence of a good (or bad) adaptive capacity, such as productive longevity and lifetime efficiency. In contrast, repeated measurements over time have a high potential for quantification of the animal's ability to cope with environmental challenges. Thus, we should be able to quantify differences in adaptive capacity from the data that are increasingly becoming available with the deployment of automated monitoring technology on farm. The challenge for future management and breeding will be how to combine various proxy measures to obtain reliable estimates of robustness components in large populations. A key aspect for achieving this is to define phenotypes from consideration of their biological properties and not just from available measures.

Symposium review: Breeding a better cow—Will she be adaptable?

“…In animal breeding, the reaction norm (i.e., the plotted line) can be generated if an animal itself is exposed to a variety of different environments, although it is more common for reaction norms, in dairy cattle at least, to be generated at a sire level where half-sib progeny of the sire (each assumed to have a covariance of ≥0.25), produce in multiple different environments (Hayes et al, 2003;Mulder, 2016). If the reaction norm for the individual (or sire) is horizontal, then the phenotype does not vary across the range of environmental conditions examined; such an individual is said to be a generalist for that trait (Levins, 1968;Friggens et al, 2017), or indeed said to have low environmental sensitivity for that trait. A nonhorizontal line implies that the expression of the genotype is a function of the environment; if the reaction norm is relatively steep, then the individual is said to be a specialist (i.e., it performs better in some environments; Friggens et al, 2017) or suffer from high environmental sensitivity for that trait.…”

“…If the reaction norm for the individual (or sire) is horizontal, then the phenotype does not vary across the range of environmental conditions examined; such an individual is said to be a generalist for that trait (Levins, 1968;Friggens et al, 2017), or indeed said to have low environmental sensitivity for that trait. A nonhorizontal line implies that the expression of the genotype is a function of the environment; if the reaction norm is relatively steep, then the individual is said to be a specialist (i.e., it performs better in some environments; Friggens et al, 2017) or suffer from high environmental sensitivity for that trait.…”

Review: New considerations to refine breeding objectives of dairy cows for increasing robustness and sustainability of grass-based milk production systems

“…Grazing systems require a cow with good grazing characteristics and a propensity for high pasture DMI, that has good fertility and is 'easy care' and docile, that can walk long distances, that is resistant to some of the diseases of grazing systems (e.g. hypomagnesaemia, foamy bloat) and that is robust to fluctuations in feed quality and quantity (Berry, 2015;Friggens et al, 2017;Delaby et al, 2018). These traits are fundamental for grazing systems to be successful and robust from 1 year to the next, as:…”

rePROBE: Workflow for Revised Probe Assignment and Updated Probe-Set Annotation in Microarrays

“…Current breeding goals and selection criteria for livestock species go beyond performance and carcass parameters and also consider the variation of functional traits [1,2]. To identify genetically robust farm animals, respective experimental approaches often require information from the various ‘omics’ levels [3].…”