Milk urea concentration (MUC) is a suitable indicator of the health and nutrition state of dairy cows. MUC is in relation to their reproduction performance, longevity and technological milk indicators. The interpretation correctness of results depends on their reliability. There are a lot of principles of MUC analyses. Their results can be affected by a number of interferential factors. Disproportions were noticed in practice. Therefore the sources of variation in results are studied. The goal of this study was to investigate relationships between different methods of MUC determination with the use of standard samples of native milk with an artificial urea addition. After evaluation I (n = 7) the results of methods BI-1 and BI-2 (photometrical ones with diacetylmonoxime) were disqualified because of poor recovery (R), poor correlation (C) with other methods, higher random error (RER) and highest systematic error (SE). Evaluation II is more effective with stricter discrimination limits. Cs of all methods mutually (0.977 up to 0.998; P < 0.001) confirmed the methods as effective with the exception of BI-2 with poor Cs (0.713 up to 0.774), poor R (16.0 up to 69.0%) and high RER ±5.292 mg/100 ml. R of better methods was 44.0 up to 96.7%. The BI-1 method had good Cs (0.986 up to 0.994; P < 0.001), higher SE -7.546 mg/100 ml and poorer R (48.5 up to 75.3%). BI-1 method was a case of mistaken performance. BI method could be improved by the use of more samples in calibration. FT-MIR method (infra-analysis) has good addition R 69.5 up to 95.0% and Cs 0.981 up to 0.994 (P < 0.001). EH method (photometrical one with Ehrlich's agent) has good R 59.0 up to 96.7%, higher SE 4.755 (I) and 2.556 (II) mg/100 ml and close Cs 0.977 up to 0.994 (P < 0.001). UR method (ureolytical difference-conductometric) showed the best combination of results about R, C, SE and RER. MUC measurement was almost independent of fat in milk (r = 0.16 for UR and 0.01 for FT-MIR; P > 0.05) and MUC of both the methods did not increase significantly with lactose increase (r = 0.16 and 0.27; P > 0.05), which increased logically (r = -0.88; P < 0.001) during the fat concentration increase. The relationship of MUC results between UR and FT-MIR was significant (validation r = 0.96; P < 0.001) at average difference -0.93 ± 1.663 mg/100 ml. It is possible to see the result reliability as good after calibration performance of FT-MIR according to results of UR. It is not necessary to see the effects of fat, protein and lactose on MUC methods as substantial. FT-MIR method for MUC has good result reliability at the use of native milk samples, incidentally with urea additions. It is suitable to calibrate the FT-MIR method according to specific determination of MUC (UR). However, the most important for elimination of disproportions is the calibration method with concrete audited R, though nonspecific.

The urea as a product of liver detoxification of ammonium is in general an undesirable metabolite in body fluids of mammals, when its concentration exceeds the physiological limit. Its very low levels are nevertheless also undesirable as they indicate the nitrogen matter malnutrition. ABSTRACT:The milk urea concentration (MUC) is a respected indicator of the health and nutrition status of dairy cows. It is in relation to their reproduction performance, longevity and technological milk indicators. The accuracy of the interpretation of results depends on their reliability, which is so important. There are a lot of principles of MUC analyses. Their results can be affected by a number of interferential factors. Many disproportions were noticed for the above-mentioned reasons in laboratory practice. That is the reason why relevant result variation sources are studied. The goal of this paper was to search the relationships between different methods of MUC determination with the use of specifically modified samples on a milk basis with the absence of dissolved components such as lactose. The results of two methods (photometric BI with diacetylmonoxime and FT-MIR (mid infrared)) were disqualified for a large shift and variance of values, unsatisfactory recovery and paralysed relation to other methods (BI r = from 0.184 to 0.213; P > 0.05). Therefore the second BI method was retained in the evaluation, and it was probably a local defect in the performance at disqualification. Nevertheless, the procedure showed poorer recovery (75.5 ± 14.3%) and necessity for methodical modifications for support of result reliability such as increase in the number of calibration points as compared to the contemporary procedure. The results of FT-MIR method were strongly systematically displaced due to lactose absence in particular (by 33.824 ± 3.794 mg/100 ml). Nevertheless, the correlations with results of other relevant methods were tight (from 0.991 to 0.999; P < 0.001). The photometrical method with Ehrlich's agent (para-dimethylaminobenzaldehyde, EH) showed acceptable values of all the evaluated indicators of reliability. The specific Ureakvant method (UR; with conductivity difference measurement) showed the most proper results in combination with all the reliability indicators (recovery as much as 93.2 ± 10.2%; correlation from 0.989 to 1.0; P < 0.001; acceptable ratio of systematic and random error components). It is possible to use the tested specific standard samples for the control or calibration of all methods (BI, EH and UR) with the exception of FT-MIR.

Automatic milking system (AMS) brings a change in approach to ensure the data reliability in the offi cial milk recording (MR). The AMS is equipped with fl owmeter. AMS so ware provides the daily milk yield (DMY) and average of the last 7 daily milk yields (AVG7) for MR. Classic MR uses DMY. AVG7 could be more reliable value. Origin of both records (DMY and AVG7) is from AMS fl owmeter. The aim of paper was to compare the values of milk yield of cows from daily (DMY) and the extended records (AVG7) from AMS for objective assess of lactations to be used in cattle breeding. Study (2013) with 2 AMS herds (DeLaval and Lely Astronaut): herd 1 -Holstein (H) dairy cows; herd 2 -Czech Fleckvieh (CF) dairy cows. There were following milk records: n = 521 DeLaval (H); n = 567 Lely Astronaut (CF); 70 (H) and 68 (CF) dairy cows. MR samples were analyzed on: fat content; crude protein; somatic cell count. Correlations between AVG7 and DMY were: 0.888 (H); 0.898 (CF, both P ≤ 0.001). There were insignifi cant diff erences (P > 0.05; −0.07 ± 3.29 kg for H and 0.28 ± 3.3 kg for CF) between AVG7 and DMY for both robots. The same is valid for diff erences in the production of milk components. According to this comparison experiment the AVG7 of AMS is a suitable equivalent for the DMY regarding offi cial MR for assessment of lactations.

Milk acetone determination by the photometrical method after microdiffusion and via FT infra-red spectroscopyMilk acetone (AC) and betahydroxybutyrate (BHB) are important indicators of the energy metabolism of cows (ketosis occurrence) and an effective method for their determination, with reliable results, is of great importance. The goal of this work was to investigate the infrared method MIR-FT in terms of its calibration for milk AC and to develop a usable procedure. The microdiffusion photometric (485 nm; Spekol 11) method was used with salicylaldehyde as a reference (Re) and mid infrared spectroscopy FT (MIR-FT: Lactoscope FT-IR, Delta; MilkoScan FT 6000, M-Sc) as an indirect method. The acetone addition to milk had no recovery using MIR-FT (Delta). The reference AC set must have acceptable statistics for good MIR-FT calibration (M-Sc) and they were: 10.1 ± 9.74 at a geometric mean of 7.26 mg l-1, and a variation range from 1.98 to 33.66 mg l-1. The AC correlation between Re and MIR-FT (Delta) was low at 0.32 (P>0.05 but the Log AC relationship between Re and MIR-FT (M-Sc) was markedly better at 0.80 (P<0.01). The conversion of >10 mg l-1 as an AC subclinical ketosis limit could be > -0.80 (feedback 0.158 mmol l-1 = 9.25 mg l-1) and > -1.66. This could be important for ketosis monitoring (using M-Sc).

Samples of milk obtained in the course of evening and morning milking performed in variable time intervals of either 11 and 13 hours (n = 1.282) or 10 and 14 hours (n = 370) were collected with the aim to quantify the effect of the length of a variable (asymmetric) time interval between evening and morning milking on the total amount and composition of daily milk production of dairy cows. Milk samples were analysed in an accredited (EN ISO 17025) laboratory in Brno-Tuřany (Czech Republic) and the following contents of individual milk components were estimated: fat (F; g.100g−1), total protein (TP; g.100g−1), lactose (L; lactose monohydrate; g.100g−1), and somatic cell counts (SCC; ­103.ml−1) were estimated in. It was found out that with the increasing total daily milk production the shares of evening and morning milk yield increased as well; however, the percentages of evening and/or morning yields in the total yield remained practically unchanged and represented 43.5 % and 56.5% or 40.4 % and 59.6 % in variants with intervals of 11 and 13 hours and/or 10 and 14 hours, respectively. In the variant with the milking interval of 11 and 13 hours, values of correlation coefficients between the above parameters (i.e. F, TP, L, SCC, and log SCC) of evening and morning milk yields on the one hand and the total milk performance on the other ranged from the minimum r = 0.896 (F) to the maximum r = 0.980 (TP). In the variant with the interval of 10 and 14 hours, the corresponding values of correlation coefficients were r = 0.848 (F) and r = 0.983 (TP). These correlations were statistically highly significant in all cases (P ≤ 0.001). Further, linear regression equations enabling the estimation of milk parameters of the total milk yield on the base of results obtained in evening and morning milking was calculated as well. Values of coefficients of determination (R2) of these equations ranged from 0.803 (F) to 0.960 (TP) and from 0.718 (F) to 0.966 (TP) for intervals of 11:13 hours and of 10:14 hours, respectively.