Date of Award

2022

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Department

Biological Sciences

First Advisor

Dr Craig Murphy

Second Advisor

Prof. Roy Sleator

Third Advisor

Dr Donagh Berry

Abstract

Despite the importance of feed intake and efficiency in beef production, there are still gaps in our knowledge on optimal production efficiency traits and breeding strategies for improved feed, production and economic efficiency. The objectives of this thesis were to redefine production efficiency in growing cattle by exploiting carcass information and to validate current beef breeding goals for improving efficiency, and to investigate the relationships of feeding behaviour with performance, feed efficiency, and carcass merit. Feed intake and liveweight data were available on up to 6,088 cattle, of which 3,146 had carcass data, 4,672 had ultrasound data and 1,548 had feeding behaviour data. Herd-level genetic merit and financial performance data were available from 1,311 commercial beef herds. Novel feed efficiency traits were derived that better depict an animal’s ability to convert feed into carcass, as opposed to just liveweight. Considerable phenotypic and genetic variation existed in a range of feeding behaviour traits, with heritability estimates ranging from 0.19 for meals per day to 0.61 for feeding time per day. Some feeding behaviours were phenotypically and genetically correlated with liveweight, efficiency, and carcass merit in growing cattle. Although the usefulness of feeding behaviour traits in predicting genetic merit for feed intake was marginal, some feeding behaviour traits explained up to 13.4 % of the inter-animal phenotypic variation in feed intake. Current terminal breeding goals in Ireland are already indirectly favouring feed and production efficient cattle; furthermore, analyses of herd-level data revealed that herds of superior beef terminal and maternal genetic merit generate more gross profit. This thesis presents potentially useful traits for the improvement of feed and production efficiency in growing cattle and should instil confidence in stakeholders as to the efficacy of beef breeding objectives.

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Access Level

info:eu-repo/semantics/openAccess

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