Simple SummaryLameness is a prevailing problem in dairy herds that has a negative effect on welfare, reproduction, and economic viability. The aim of this study was to investigate if the negative impact of lameness on ovarian activity at the end of puerperium is related to the energy status of dairy cows and to measure the responsiveness of lame dairy cows to hormonal manipulations. Lame cows had poorer ovarian activity at the end of puerperium; however, this finding was not associated with the energy status of the cows. Most lame cows responded well to estrous synchronization protocols and showed adequate long term reproductive performance. The severity of lameness was explanatory mainly for the risk of a cow to be culled during the study, whereas the type of lesion was primarily associated with lower fertility. Our results emphasize the need for the prompt diagnosis and treatment of lame cows. Additionally, these cows require intensive reproductive management due to the greater risk of being anovulatory at puerperium.AbstractThe purpose of this study was to assess the ovarian and energy status of multiparous lame dairy cows at the end of puerperium and investigate their responsiveness to estrous synchronization treatment regimens. Initial lameness scoring was performed at 28 ± 5 and 37 ± 5 d post partum, followed by lesion documentation and treatment. Cows were blocked by lameness severity and were randomly allocated to an estrous synchronization treatment regimen with seven days of progesterone supplementation (group LP,n= 26) or with an administration of PGF2αtwice, 14 d apart (group LC,n= 26). Non-lame cows served as controls (group C,n= 27) and the same treatment regimen was imposed as that for group LC. Twelve days after estrous presynchronization, an Ovsynch treatment regimen and timed AI were imposed. Ultrasonography of the ovaries and blood sampling for progesterone were used to assess cyclicity status, whereas β-hydroxybutyrate (BHBA) and non-esterified fatty acids (NEFA) were used to assess energy status. Lame cows were to a greater proportion non-cycling (36.5% vs. 11.1%;p= 0.02), had greater overall NEFA concentrations (0.32 ± 0.02 vs. 0.26 ± 0.02 mEq/L;p= 0.02) and a greater incidence of elevated NEFA concentrations (53.9% vs. 29.6%,p= 0.04) compared to control cows. However, no interaction between energy and lameness status was evident regarding non-cycling cows. The percentage of cows responding to the presynchronization, synchronization and ovulating did not differ between groups LP, LC, and C. The first-service conception rate (FSCR) tended to be greater for group C (37.0%) compared to group LP (16.0%;p= 0.08). Long-term reproductive performance did not differ between lame and control cows, although culling rates did (21.2% vs. 0%, respectivly;p= 0.01). The severity of lameness had an effect on culling rates (30.6% vs. 0% for cows with marked vs. moderate lameness;p= 0.01), whereas the type of lesion largely explained poor reproductive performance (FSCR 13.9% vs. 40.0% for cows with claw horn disruptions vs. infectious lesions;p= 0.04). Conclusively, cows that were lame during puerperium are at a greater risk of not cycling irrespective of energy status. Treatment regimens for the synchronization of ovulation seem to be efficient at resuming ovarian cyclicity. Marked lameness was detrimental to survivability, whereas cows with claw horn lesions had compromised reproductive capacity.