Abstract
The purpose of this retrospective cohort study was to evaluate the effects of the timing of hyperketonemia (HYK) diagnosis during early lactation on milk yield and composition, reproductive performance, and herd removal. Plasma β-hydroxybutyrate (BHB) was measured twice a week during the first 2 wk of lactation in 362 multiparous Holstein cows for the diagnosis of HYK. In each week, cows were diagnosed as HYK positive (HYK+) if the plasma BHB concentrations were ≥1.2 mmol/L in at least one of the tests for the week evaluated. Milk-related outcomes (first 10 monthly milk tests) included milk yield, milk fat and protein content, milk urea nitrogen (MUN), and linear score of somatic cell count. Other performance outcomes of interest included risk of pregnancy within 150 d in milk (DIM) and herd removal (i.e., culling or death) within 300 DIM. Statistical models were built separately for cows diagnosed with HYK during the first week of lactation (wk1) and for cows diagnosed during the second week of lactation (wk2). All models for wk2 were adjusted by HYK diagnosed in wk1, along with other potential confounder variables. The association between HYK in each week and milk-related outcomes was assessed using generalized estimated equation models that accounted for repeated measures. Time to pregnancy and time to herd removal were analyzed using Cox's proportional hazard regression models. Seventy-eight cows (21.5%) tested positive for HYK during wk1, 60 cows (16.6%) in wk2, and 29 cows (8.0%) in both weeks. Hyperketonemia during wk1 was associated with a milk yield reduction of 3.7 kg [95% confidence interval (CI): -6.67 to -0.76] per cow per day throughout the lactation. Meanwhile, we did not observe evidence of an association between HYK diagnosed during wk2 and milk yield. During the first 2 monthly milk tests, cows diagnosed as HYK+ in wk1 had greater fat (0.42%; 95% CI: 0.16 to 0.67) and MUN (0.75 mg/dL; 95% CI: 0.26 to 1.24) content in milk than HYK-negative (HYK-) cows. We did not detect any evidence of an association between HYK diagnosed in wk2 and these outcomes. The HYK+ cows in wk1 had a 30% [hazard ratio (HR) = 0.70; 95% CI: 0.48 to 1.01] lower risk of pregnancy within 150 DIM and 2.48 times (95% CI: 1.63 to 2.89) higher risk of herd removal within 300 DIM than HYK- cows. Conversely, no evidence of association was observed between HYK+ cows in wk2 and risk of pregnancy by 150 DIM (HR = 0.98; 95% CI: 0.64 to 1.51) or removal from the herd within 300 DIM (HR = 0.91; 95% CI: 0.52 to 1.60). Our findings indicate that HYK diagnosed during wk1 of lactation is associated with negative performance in terms of milk yield, reproduction, and herd removal. No evidence of association was found for the same outcomes when HYK was diagnosed in wk2. Our results suggest the need to consider the timing when HYK is diagnosed when investigating its association with performance outcomes.
Highlights
During the transition from late gestation to early lactation, cows experience important physiological and metabolic changes (Bauman and Currie, 1980)
Our findings indicate that HYK diagnosed during wk1 of lactation is associated with negative performance in terms of milk yield, reproduction, and herd removal
Our results showed that wk1 HYK+ cows produced substantially less milk throughout lactation than wk1 HYK− cows, whereas wk2 HYK+ cows had a biologically relevant, but not statistically different, reduction (−1.5 kg/d) in milk yield throughout the lactation compared with wk2 HYK− cows
Summary
During the transition from late gestation to early lactation, cows experience important physiological and metabolic changes (Bauman and Currie, 1980). The capacity of dairy cows to adapt to their new physiological state will determine their health and productivity after calving (Herdt, 2000). As part of the metabolic adaptation, dairy cows mobilize body reserves— fatty acids from adipose tissue, which become ketone bodies—to be used as alternative sources of energy (Herdt, 2000). An excessive circulation of ketone bodies, known as hyperketonemia (HYK), is associated with compromised health, productivity, and reproductive performance (Ospina et al, 2010; Suthar et al, 2013; Raboisson et al, 2014). A Rodriguez et al.: EFFECTS OF HYPERKETONEMIA BY WEEK OF DIAGNOSIS high prevalence of HYK diagnosed during the first 2 wk after calving is traditionally considered an indicator of problems in the transition period. Screening protocols to diagnose HYK typically involve the testing of cows during the first 2 wk of lactation because of the elevated prevalence of HYK reported during this period (van der Drift et al, 2012; Suthar et al, 2013; Santschi et al, 2016)
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