Abstract
Submitted 2020-07-17 | Accepted 2020-08-18 | Available 2020-12-01 https://doi.org/10.15414/afz.2020.23.mi-fpap.250-257 This study aimed to evaluate the score for subclinical ketosis risk, which is routinely monitored in Czech Holstein cows. The score is based on milk recording indicator traits which include fat-to-protein ratio, fat-to-lactose ratio, citric acid, β-hydroxybutyrate, and acetone concentrations. The score was significantly (P <0.001) affected by the age of cow at calving, days in milk (DIM) and season of test-day recording. Variance components were estimated with a univariate linear animal model for the score on the first test-day and with a multivariate linear animal model for the score in 3 successive test-days (6-40, 30-70, 60-100 DIM). The heritability estimate was lower at the beginning of lactation (0.08) and increased gradually to 0.11 at the end of the recorded period. Genetic correlations between the score at the first and the other two test-days were lower than 1 indicating that they are genetically different traits. Estimated breeding values were normally distributed with mean 0.20 and reliabilities up to 0.66 in females and 0.98 in males. Breeding values were negatively correlated with most of other routinely evaluated traits, with the strongest correlations with milk fat percentage (0.39), body condition score (-0.26) and fertility of cows (-0.25). The score for subclinical ketosis risk showed sufficient genetic variability and had the potential to be used in genetic improvement of resistance to (sub)clinical ketosis of Czech Holstein cows. Keywords: metabolic status, indicator trait, ketone body References Bastin, C. et al. (2016) On the role of mid-infrared predicted phenotypes in fertility and health dairy breeding programs. Journal of Dairy Science, 99(5), 4080–4094. https://doi.org/10.3168/jds.2015-10087 Belay, T.K. et al. 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Highlights
Ketosis is one of the most prevalent metabolic disorders in dairy cows with incidence up to 17.2% for its clinical and 36.6% for its subclinical form (Pryce et al, 2016)
Ketone bodies content can be used as an indicator trait (Koeck et al, 2014, Vosman et al, 2015, Belay et al, 2017), as it is regularly measured under the testday milk recording programme, and it reflects the physiological status of the cow (Bastin et al, 2016)
Means of the score according to test-days (Table 2) and least squares means of the score according to days in milk (DIM) (Figure 1) showed the highest values at the beginning of the lactation which reflects a more severe negative energy balance experienced by the cow after calving (Martens, 2020)
Summary
Ketosis is one of the most prevalent metabolic disorders in dairy cows with incidence up to 17.2% for its clinical and 36.6% for its subclinical form (Pryce et al, 2016). Ketosis in clinical form is manifested as reduced feed intake, weight loss and production decline Both clinical and subclinical ketosis are characterized by the accumulation of ketone bodies (acetone, acetoacetate, β-hydroxybutyrate) in body fluids, including milk (Pryce et al, 2016). Risk of subclinical ketosis within the first 100 days in milk (DIM) is routinely evaluated using five indicators based on milk components predicted with mid-infrared analysis of test-day milk samples in the Czech Republic. These indicators include fat-to-protein ratio (FP), fat-to-lactose ratio (FL), citric acid (CA), milk β-hydroxybutyrate (BHB), and milk acetone (ACE) content. The total score for subclinical ketosis risk is calculated for each cow as a sum of cases when the predicted indicator was higher than the previously determined threshold (Hanuš et al, 2013)
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