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Leslie Foldager

Defining and using novel milk composition based heat stress resilience traits in the context of genomic selection for more robust dairy cows in Wallonia

Publikation: Bidrag til bog/antologi/rapport/proceedingKonferenceabstrakt i proceedingsForskningpeer review

Recent research showed the usefulness of using estimated breeding values (EBV)
for mid-infrared (MIR) based biomarkers in genetic improvement. A novel class of
biomarkers was defined based on modelling responses of milk composition
(e.g., mid-infrared (MIR) based) to stress expressed on continuous scales using
reaction norm models. Heat stress is an important aspect of dairy production even in temperate climates as shown in recent studies. Implementation of genomic selection for tolerance to heat stress is therefore not only an issue for Australian dairy cattle, a country that recently introduced such an evaluation. The question remains open if using milk composition based heat stress resilience genomically enhanced EBV (GEBV) is not a viable option. Genetic parameters were estimated for production, udder health, and milk composition traits. Data included 155,977 test-day records for milk, fat, and protein yields, fat and protein percentages, 9 individual milk fatty acids (FA), 7 FA groups, 5 minerals, and 3 ketone bodies predicted by mid-infrared spectrometry, and 7 FA groups. Data were from 21,375 first-lactation Holstein cows in 473 herds in the Walloon region of Belgium and were collected between 2008 and 2014. Test-day records were merged with daily temperature-humidity index (THI) values based on meteorological records from public weather stations. The maximum
distance between each farm and its corresponding weather station was 13 km. Linear reaction norm models were used to estimate the intercept and slope responses of 23 traits to increasing THI values. Most yield and FA traits had phenotypic and genetic declines as THI increased, whereas C18:0, C18:1 cis-9, and 4 FA groups (unsaturated FA, monounsaturated FA, polyunsaturated FA, and long-chain FA) increased with THI. Moreover, the latter traits had the largest slope-to-intercept genetic variance ratios, which indicate that they are more affected by heat stress at high THI levels, and therefore good candidate traits. Among all traits, C18:1 cis-9 was the most sensitive to heat stress. As this trait is known to reflect body reserve mobilization, using its response to THI could be a very affordable milk biomarker of heat stress for dairy cattle, expressing the equilibrium between intake and mobilization, and therefore adaptation, under warm conditions. By including novel milk based composition traits to traditional production traits, correlations between EBVs and GEBVs of those milk based traits and udder health, fertility and longevity increased considerably. This
study demonstrated that milk composition resilience heat stress traits could be used as early indicators of robustness traits. Our results also suggest that marker information tend to lead to higher accuracies of prediction. Therefore, new options to improve robustness through genomic selection in Walloon Holsteins are now available.
OriginalsprogEngelsk
TitelProceedings of the ICAR Conference
RedaktørerJ. Bryant, M. Burke, R. Cook, B. Harris, C. Mosconi, B. Wickham
Antal sider6
Vol/bind23
Udgivelsesår2018
Sider229-234
ISBN (trykt)92-95014-19-7
StatusUdgivet - 2018
BegivenhedICAR Conference - Auckland, New Zealand
Varighed: 10 feb. 201811 feb. 2018

Konference

KonferenceICAR Conference
LandNew Zealand
ByAuckland
Periode10/02/201811/02/2018
SerietitelICAR Technical Series
ISSN1563-2504

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