Validation of milk mid-infrared spectroscopy for predicting the metabolic status of lactating dairy cows in Australia

Abstract

Increased concentrations of some serum biomarkers are known to be associated with impaired health of dairy cows. Therefore, being able to predict these biomarkers, especially in the early stage of lactation, would enable preventive management decision. Some health biomarkers may also be used as phenotypes for genetic improvement for improved animal health. In this study, we validated the accuracy and robustness of models for predicting serum concentrations of β-hydroxybutyrate (BHB), fatty acids, and urea nitrogen, using milk midinfrared (MIR) spectroscopy. The data included 3,262 blood samples of 3,027 lactating Holstein-Friesian cows from 19 dairy herds in Southeastern Australia, collected in the period from July 2017 to April 2020. The models were developed using partial least squares regression and were validated using 10-fold random cross-validation, herd-year by herd-year external validation, and year by year validation. The coefficients of determination (R 2 ) for prediction of serum BHB, fatty acids, and urea obtained through random cross-validation were 0.60, 0.42, and 0.87, respectively. For the herd-year by herd-year external validation, the prediction accuracies held up comparatively well, with R 2 values of 0.49, 0.33, and 0.67 for of serum BHB, fatty acids, and urea, respectively. When the models were developed using data from a single year to predict data collected in future years, the R 2 remained comparable, however, the root mean squared errors increased substantially (4-10 times larger than compared with that of herd-year by herd-year external validation) which could be due to machine differences in spectral response, the change in spectral response of individual machines over time, or other differences associated with farm management between seasons. In conclusion, the mid-infrared equations for predicting serum BHB, fatty acids, and urea have been validated. The prediction equations could be used to help farmers detect cows with metabolic disorders in early lactation in addition to generating novel phenotypes for genetic improvement purposes.

The use of milk mid-infrared spectroscopy to improve genomic prediction accuracy of serum biomarkers

“…Genetic correlations between ) and between fatty acids and MFA (0.28-0.56) were moderate and had large standard errors (0.13-0.32). The genetic correlations are in line with the prediction accuracies of the MIR equations reported by Ho et al (2020): prediction accuracies of the MIR equations were highest for urea and lowest for fatty acids. Despite having a genomic correlation significantly lower than 1, MBHB and MFA may still be useful for genomic prediction, especially if many more records would be available for MBHB and MFA than for BHB and fatty acids.…”

“…The use of milk mid-infrared spectroscopy to improve genomic prediction accuracy of serum biomarkers I. van den Berg, 1 * P. N. Ho, 1 T. D. W. Luke, 1,2 M. Haile-Mariam, 1 S. Bolormaa, 1 and J. E. Pryce 1,2 using milk MIR to predict these serum biomarkers, with the value of R 2 obtained through random crossvalidation ranging between 0.21 and 0.92 (Belay et al, 2017;Grelet et al, 2019;Luke et al, 2019a,b;Pralle and White, 2020). In Australia, the equations for predicting serum BHB, fatty acids, and urea were initially developed by Luke et al (2019b) and have recently been validated by Ho et al (2020), with accuracies obtained through 10-fold random cross-validation of 0.60, 0.42, and 0.87, respectively. In this context, if MIR-predicted biomarkers are heritable, genetically correlated with the measured serum biomarkers concentrations, and available on a large number of individuals, they should theoretically help to increase the size of reference populations, and thereby aid the implementation of genomic prediction for health traits based on biomarkers.…”

“…The MIR-predicted biomarkers were derived using the equations previously developed by our group (Luke et al, 2019b;Ho et al, 2020). A full description of the development of the MIR equations used in our study can be found in Ho et al (2020).…”

“…The MIR-predicted biomarkers were derived using the equations previously developed by our group (Luke et al, 2019b;Ho et al, 2020). A full description of the development of the MIR equations used in our study can be found in Ho et al (2020). Generally, the prediction accuracies (R 2 ) obtained for BHB, fatty acids, and urea were 0.60, 0.42 and 0.87 through 10-fold random cross-validation, and 0.48, 0.35, and 0.69 through herdby-herd validation.…”

Genetic parameters of blood urea nitrogen and milk urea nitrogen concentration in dairy cattle managed in pasture-based production systems of New Zealand and Australia

“…BUN requires a more difficult and costly blood sample, which limits the number of records. However, BUN can be accurately predicted using mid-infrared spectroscopy of a milk sample (Ho et al 2021). Our previous study showed that mid-infrared spectroscopy-predicted BUN (MBUN) and BUN are highly correlated, with a genetic correlation close to 1 (van den Berg et al 2021), and may therefore be considered as the same trait.…”