Infrared milk analyzers: Milk urea nitrogen calibration

Portnoy, Matilde; Coon, C. N.; Barbano, D.M.

doi:10.3168/jds.2020-18772

Cited by 10 publications

(8 citation statements)

References 17 publications

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“…The p-values>0.05 confirming significance of the instrument effects throughout all 177 weeks confirms this, while the weekday variations within each instrument were significant for only two of the 177 weeks. Recent work on minor milk components such as milk urea has also shown the impact of inter instrument differences on IR predicted results (Wood et al, 2020;Portenoy et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

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Routine Monitoring of Instrument Stability in a Milk Testing Laboratory With ASCA: A Pilot Study

et al. 2021

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Mid-infrared spectroscopy has been developed as a reliable and rapid tool for routine analysis of fat, protein, lactose and other components in liquid milk. However, variations within and between FTIR instruments, even within the same milk testing laboratory, present a challenge to the accuracy of measurement of particularly minor components in the milk, such as individual fatty acids or proteins. In this study we have used Analysis of variance–Simultaneous Component Analysis (ASCA), to monitor the spectral variation between and within each of four different FOSS FTIR spectrometers over each week in an independent milk testing laboratory over 4 years, between August 2017 and March 2021 (223 weeks). On everyday of each week, spectra of the same pilot milk sample were recorded approximately every hour on each of the four instruments. Overall, variations between instruments had the largest effect on spectral variation over each week, making a significant contribution every week. Within each instrument, day-to-day variations over the week were also significant for all but two of the weeks measured, however it contributed less to the variance overall. At certain times other factors not explained by weekday variation or inter-instrument variation dominated the variance in the spectra. Examination of the scores and loadings of the weekly ASCA analysis allowed identification of changes in the spectral regions affected by drifts in each instrument over time. This was found to particularly affect some of the fatty acid predictions.

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Section: Discussionmentioning

confidence: 99%

“…Recent work on minor milk components such as milk urea has also shown the impact of inter instrument differences on IR predicted results. (Wood et al, 2020;Portenoy et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

Routine Monitoring of Instrument Stability in a Milk Testing Laboratory With ASCA: A Pilot Study

et al. 2021

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“…Modified Milk Calibration Sample Set to Evaluate Method Performance. Modified milk calibration samples (14 milk samples per set), prepared in the Cornell University Pilot Plant as described by Kaylegian et al (2006), and as modified by Portnoy et al (2021), were shipped to a total of 9 laboratories, where they were analyzed by reference chemical methods for all the main milk components and MUN. The methods used to determine fat, protein, and lactose in the sample set were the following validated methods (AOAC International, 2019c): for fat, Mojonnier ether extraction (Barbano et al, 1988;AOAC International, 2019c; method 989.05); for true protein, Kjeldahl analysis for direct protein nitrogen determination (Barbano et al, 1991;AOAC International, 2019c;method 991.22); for lactose, spectrophotometric enzymatic analysis (Lynch et al, 2007;AOAC International, 2019c;method 2006.06).…”

Section: Performance Evaluation Of the Enzymatic Spectrophotometric Mun Methodsmentioning

confidence: 99%

Performance evaluation of an enzymatic spectrophotometric method for milk urea nitrogen

Portnoy

Coon

Barbano

2021

Journal of Dairy Science

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Our objective was to determine the within and between laboratory performance of an enzymatic spectrophotometric method for milk urea nitrogen (MUN) determination. This method first uses urease to hydrolyze urea into ammonia and carbon dioxide. Next, ammonia (as ammonium ions) reacts with 2-oxoglutarate, in the presence of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) and the enzyme glutamate dehydrogenase (GlDH), to form l-glutamic acid, water, and NADP + . The change in light absorption at 340 nm due to the conversion of NADPH to NADP+ is stoichiometrically a function of the MUN content of a milk sample. The relative within (RSD r ) and between (RSD R ) laboratory method performance values for the MUN enzymatic spectrophotometric method were 0.57% and 0.85%, respectively, when testing individual farm milks. The spectrophotometric MUN method demonstrated better within and between laboratory performance than the International Dairy Federation differential pH MUN method with a much lower RSD r (0.57 vs. 1.40%) and RSD R (0.85 vs. 4.64%). The spectrophotometric MUN method also had similar method performance statistics as other AOAC International official validated chemical methods for primary milk component determinations, with the average of all RSD r and RSD R values being <1%. An official collaborative study of the enzymatic spectrophotometric MUN method is needed to achieve International Dairy Federation, AOAC International, and International Organization for Standardization official method status.

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“…Mitchell et al (2005) also found that the infrared predictions showed greater heritability than the wet chemistry MU values (0.22 vs. 0.15, respectively). Recently, Portnoy et al (2021) pointed out, when using a PLS model to predict the urea content of milk, that careful attention needs to be given to modeling the background variation in milk fat, true protein, and lactose, as they are correlated with the urea content.…”

Section: Descriptive Statistics and Main Sources Of Variation In Milk...mentioning

confidence: 99%

Effects of breed, farm intensiveness, and cow productivity on infrared predicted milk urea

Bittante

2022

Journal of Dairy Science

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Milk urea content is receiving growing interest from science and industry as a tool to infer the protein adequacy of dairy cows' diets, nitrogen excretion and its environmental impact, and efficiency of animals' protein metabolism. Fourier-transform infrared (FTIR) prediction is a high-throughput method for rapidly and cheaply evaluating milk urea content at the population level. Existing knowledge of the major sources of variation (e.g., year, season, farming system, individual herd, and the cow's breed, parity, stage of lactation, and productive potential) is fragmentary. The objective of this work was to study at the population level the simultaneous effects of all the major sources of variation and their most important interactions. Milk urea content in 1,759,706 test day milk samples collected from 291,129 lactations of 115,819 cows from 6,430 herds over 8 yr was predicted by FTIR. The milk urea content data (and also milk protein percentage, for comparison) were analyzed using a linear model that included the effects of parity, days in milk (DIM) class, year, month, herd intensiveness level, cow productivity level, breed, and herd intensiveness and cow productivity levels within breed. All sources of variation of milk urea content proved highly significant, the most important in terms of F-value being breed > year > herd intensiveness level > parity. The ranking for milk protein was very different (DIM class > herd intensiveness level > parity > breed). The patterns of the least squares means for urea and protein contents of milk were also very different and sometimes contrasting. The seasonal variation in urea was sinusoidal. Urea content increased during the first 4 mo of lactation and then remained almost stable before decreasing after 11 mo. Specialized dairy breeds had lower average milk urea content than dual-purpose breeds; in the former case it was lower in Holsteins than in Brown Swiss, and in the latter it was lower in Simmentals than in Alpine Greys. The effect of herd intensiveness level was much stronger than the effect of cow productivity level; the increase in milk urea with increasing herd average daily milk yield was almost linear in the case of dairy breeds but curvilinear in dual-purpose breeds. The large differences in breed and the modest relationships with the cow's productive potential require further analysis at the genetic level to obtain information of potential use in genetic improvement of the dairy cow populations.

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Infrared milk analyzers: Milk urea nitrogen calibration

Cited by 10 publications

References 17 publications

Routine Monitoring of Instrument Stability in a Milk Testing Laboratory With ASCA: A Pilot Study

Routine Monitoring of Instrument Stability in a Milk Testing Laboratory With ASCA: A Pilot Study

Performance evaluation of an enzymatic spectrophotometric method for milk urea nitrogen

Effects of breed, farm intensiveness, and cow productivity on infrared predicted milk urea

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