Implementation of Ketosis breeding value in Italian Holstein
An increase of circulating ketone bodies is associated, particularly at the onset of the lactation, with (sub)clinical ketosis, which may reduce cows’ health, production and increase culling rate. The aim of the current research was to develop a genetic evaluation for subclinical ketosis for Holstein dairy cattle using data routinely available from the national milk recording system and linear type classification. For this breeding value three traits were considered: 1) β-hydroxybutyrate (BHB), 2) fat-to-protein ratio (FPR), both measured during routine milk recording, and 3) linear body condition score (BCS) measured by a classifier. Both FPR and BCS were used as indicator traits for subclinical ketosis. Currently milk BHB and FPR were available on more than 2.2 million test-days records belonging to Holstein cows in the first 90 days-in-milk from first, second and third lactation. These records were subsequently matched to the closest linear classification date when body condition score (BCS) was scored. The pedigree of phenotyped cows was traced back up to 4 generations. (Co)variance components were estimated using trivariate linear mixed models; in particular, for BHB and FPR the fixed effects of herd-test-day, the two-way interaction between week of lactation and parity, and the three-way interaction between classes of age at calving, parity and year of calving were considered. The additive genetic effect and, only for BHB and FPR, the permanent environment were the random effects. Heritability estimates were 0.093, 0.090 and 0.157 for BHB, FPR and BCS, respectively, while repeatability estimates were 0.179 (BHB) and 0.209 (FPR). Phenotypically, milk BHB was positively correlated with FPR (0.279) and weakly with BCS (-0.038), similarly to the correlation estimated between FPR and BCS (-0.049). Milk BHB was genetically correlated with FPR (0.159) and BCS (-0.161), while the genetic correlation between FPR and BCS was -0.14. The results from the present study demonstrated the presence of exploitable genetic variation for breeding purposes resulting in EBVs.
LicenseAuthors who publish with this journal agree to the following terms:
- Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
- Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
- Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).