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Developments in Estimated Breeding Index

15 October 2013

Since 2001, a Breeding Index been evolving in Ireland to provide genetic information on milk quality, environmental footprint and health and disease.

Like any tool it must be constantly questioned and challenged, according to Sinead McParland and Donagh Berry of Teagasc, Ireland. 

Over the last twelve years the Estimated Breeding Index (EBI) has undergone many modifications, with the most recent coming with the inclusion on milking duration and temperament in 2013. 

Introduction 

A plethora of studies has clearly and unequivocally shown that improved profit ensues from selection on EBI. Genetic merit for milk solids continues to increase and genetic improvement for fertility is improving year on year.

By the year 2020 the genetic merit for fertility of the Irish national dairy herd will be back to 1989 levels; however the cow of 2020 will produce 60 per cent more milk solids than the cow of 1989. Scrutiny of the EBI, nonetheless, suggests at least three suites of traits that are either explicitly neglected or can be improved. These include 1) milk quality, 2) environmental footprint including feed intake, and 3) health, disease and welfare.

Milk quality

Ireland exports 90 per cent of its dairy products and therefore production of consistently high quality milk is paramount. Although the milk, fat and protein are included in the EBI, fat and protein alike can be decomposed into their individual components.

Milk fat is an accumulation of saturated and unsaturated fatty acids. Preliminary analysis suggests that the concentration of saturated fat in the milk fat of Irish dairy cows is naturally lower, likely attributable (in part) to our grazed grass diet. Lower saturated fatty acid concentrations are important because of their apparent unfavourable impact on human health.

Therefore Ireland already has a natural competitive advantage in our milk fatty acid profile. Furthermore, the level of conjugated linoleic acid (CLA) is, on average, greater in grazing cows; CLA is an anti-carcinogenic.

Researchers in Moorepark, as part of an international collaboration, developed the necessary methodology to accurately predict saturated fatty acid content of routinely collected milk samples from milk recording schemes. Considerable genetic differences exist among animals; the heritability of milk fatty acid content is 0.20 to 0.40.

The cost of generating the data is negligible and because the data are available on each milk recorded animal, genetic evaluations for milk fatty acid is possible. Once the extent of the genetic variation is known, research on how best to include this measure of milk quality in the
EBI will commence.

Research has also begun on quantifying the genetic variation present in milk protein and mineral profiles, as well as the functional characteristics of milk. These properties are all important contributors to cheese quality and yield. If ample genetic variation exists and improving these properties add value to the milk then their inclusion in future revisions of the EBI must be considered.

Environmental footprint and feed intake

Although no direct financial incentive currently exists for improving individual cow environmental footprint, this may not always prevail. Traits describing the environmental load of an individual animal include methane emissions and nitrogen excretion.

Irrespective, the excretion of such wastes usually also imply inefficiency in the production system. Methane emissions account for approximately six per cent of energy loss, therefore, reducing emissions assuming no deleterious consequences on performance could be beneficial.

Feed accounts for up to 80 per cent of the variable costs in Irish dairy production systems, thus improving the efficiency could yield considerable benefits. There is some scope to reduce feed intake per animal through breeding without compromising milk production, however the main efficiency goal is that of the entire system.

Milk production and live-weight, both included in the EBI account for a large proportion of feed efficiency, while fertility, health and survival account for a major proportion of the remainder. Therefore, the EBI is indirectly selecting for improved efficiency. 

The main reason for not including environmental footprint and feed intake in the EBI is the cost associated with collection of the data. However, developments in biosensors and other tools to predict these traits are currently under investigation to generate the necessary data for genetic evaluations.

Health, disease and welfare

Although a health sub-index currently exists within the EBI it includes only udder health and lameness and does not include other infectious and metabolic diseases or resistance/ resilience to parasites. The relative emphasis on health in the EBI is low because the impact of compromised health on performance such as reduced milk production, inferior fertility and decreased survival is already captured through inferior genetic merit of the animal for these traits. Inclusion of a trait in the EBI requires accurate estimates of the genetic differences among sires which in turn require large quantities of data.

Farmers know which animals were sick and the facility already exists to upload such information
into the ICBF database. This information can be used to identify which family lines have compromised health. More importantly, inclusion of such information in the EBI will improve the overall health status of the national herd similar to how the EBI is currently improving the fertility status. The onus is on farmers to record these data. Initiatives are also underway to collate the data from abattoirs and other sources. The applicability of non-expensive biosensor technology to measure health characteristics of an animal for use in genetic evaluations is under way.

Conclusions

The EBI has evolved since its introduction in 2001. It now includes seven main subindexes, milk production, fertility & survival, calving performance, beef, cow maintenance, health, and management. Research is underway to ensure the EBI remains relevant to the futuristic Irish production systems.

October 2013

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