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dc.contributor.authorHurley, AMen_US
dc.contributor.authorLopez-Villalobos, Nen_US
dc.contributor.authorMcParland, Sen_US
dc.contributor.authorLewis, Een_US
dc.contributor.authorKennedy, Een_US
dc.contributor.authorO'Donovan, Men_US
dc.contributor.authorBurke, JLen_US
dc.contributor.authorBerry, DPen_US
dc.coverage.spatialAdelaide, Australiaen_US
dc.date.available2016-07-07en_US
dc.date.issued2016-07-07en_US
dc.identifier.citationProceedings of the New Zealand Society of Animal Production, 2016, 76 pp. 38 - 42 (5)en_US
dc.identifier.issn1176-5283en_US
dc.description.abstractThe objective of this study was to estimate genetic parameters for measures of energy conversion efficiency (ECE), energy balance (EB), net energy intake (NEI), net energy of lactation (NEL) and body weight (BW), within lactation stages in grazing dairy cows. Individual measurements of NEI (n=7,675) from 2,445 lactations on 1,245 grazing cows were available. Residual energy intake (REI) was defined as NEI minus predicted energy requirements; residual energy production (REP) was defined as net energy of lactation (NEL) minus predicted energy requirements. Energy conversion efficiency was defined as NEL divided by NEI; EB was defined as the difference between intake and energy required for maintenance plus lactation. Lactation was divided into three stages (8-90, 91-180, and >180 days in milk [DIM]). Genetic and phenotypic (co)variances for EB, NEL and BW were estimated using univariate and bivariate animal repeatability models. The models included the fixed effects of contemporary group (treatment and test-date), parity, DIM, as well as a random additive genetic effect of animal, a within-lactation stage random permanent environmental effect and an across-lactation permanent environmental effect. Heritability across-lactation stages varied from 0.13 (8-90 DIM) to 0.28 (91-180 DIM) for NEI, from 0.16 (8-90 DIM) to 0.33 (91-180 DIM) for NEL, from 0.04 (8-90 DIM) to 0.10 (91-180 and >180 DIM) for EB, from 0.03 (8-90 DIM) to 0.11 (>180 DIM) for REI, and from 0.04 (8-90 DIM) to 0.18 (>180 DIM) for ECE. A strong genetic association between REI and EB was evident when average BW change was close to zero. These genetic parameters from Holstein-Friesian dairy cows fed predominantly grazed grass imply that genetic improvement in selected efficiency traits is achievable.en_US
dc.format.extent38 - 42 (5)en_US
dc.publisherNZSAPen_US
dc.relation.urihttp://www.nzsap.org/system/files/proceedings/%2319%20Hurley.pdfen_US
dc.rightsThis work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License
dc.subjectgeneticsen_US
dc.subjecthertiabilityen_US
dc.subjectfeed efficiencyen_US
dc.subjectresidual energy intakeen_US
dc.titleGenetics of alternative definitions of feed efficiency in grazing lactating dairy cowsen_US
dc.typeConference Paper
dc.citation.volume76en_US
dc.description.confidentialfalseen_US
dc.identifier.elements-id280005
dc.relation.isPartOfProceedings of the New Zealand Society of Animal Productionen_US
dc.description.publication-statusPublisheden_US
pubs.organisational-group/Massey University
pubs.organisational-group/Massey University/College of Sciences
dc.identifier.harvestedMassey_Dark
pubs.notesNot knownen_US
dc.subject.anzsrc0702 Animal Productionen_US


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