香蕉牛奶

1、Seasonal changes in somatic cell content in milk of Polish Holstein-Friesian cows,Maciej Gierdziewicz The Faculty of Animal Sciences Agricultural University in Cracow,Somatic cells in milk,In cattle breeding, the number of somatic cells in milk (Somatic Cell Count - SCC) is a commonly accepted indicator of subclinical mastitis.,http:/ 天津电线电缆 电力电缆 低烟无卤电缆 http:/ http:/,Healthy cow SCC up to 100 000 /ml SCC depends on lactation number: 1st lactation cow up to 35 000 /ml 2nd lactation cow up to 50 0

2、00 /ml 3rd lactation cow up to 60 000 /ml,Cow with (sub)clinical mastitis SCC 500 000 5 000 000 50 000 000 ?,Somatic cells in milk (2),COUNCIL DIRECTIVE 92/46/EEC, 16 June 1992: Health rules for the production and placing on the market of raw milk, heat-treated milk and milk-based products, . CHAPTER IV Standards to be met for collection of raw milk . A. Raw cows milk .”,COUNCIL DIRECTIVE 92/46/EEC 16 June 1992 (continued),Somatic cell count (per ml) 400 000 (b) (b) Geometric average over a peri

3、od of three months, with at least one sample a month, or, where production levels vary considerably according to season, method of calculating results to be adjusted .”,Rozporzdzenie Ministra Rolnictwa i Gospodarki ywnociowej z dnia 29 wrzenia 1999 r. (Polish regulations),Wprowadzone w normie zmiany obejmuj: . 2. Ograniczenie iloci klas jakociowych mleka. . klasa Ekstra, klasa I i klasa II Wymagania szczegowe dla poszczeglnych klas mleka: Ekstra: Komrki somatyczne - liczba w 1 ml (SCC/ml limit)

4、100 000,Transformation of SCC to SCS,Somatic Cell Count is very variable: 0-1-10-100- . 10 000 000 - 100 000 000 . logarithmic transformation: SCS - Somatic Cell Score SCS = log2(SCC/100 000) + 3 SCC 6 250 12 500 25 000 50 000 100 000 200 000 400 000 800 000 SCS -1 0 1 2 3 4 5 6 .,Selected references I. General,Svendsen M., B. Heringstad, 2006: Somatic cell count as an indicator of sub-clinical mastitis. Genetic parameters and correlations with clinical mastitis. (Interbull Bulletin) Correlation

5、 coefficients between clinical and sub-clinical mastitis: 0,3 - 0,6,Selected references II. Age, test month, % of HF genes,Effect of age: Kennedy B.W. et al., 1982: Environmental Factors Influencing Test-Day Somatic Cell Counts in Holsteins (Journal of Dairy Science) slow decrease with age; steep increase in VI and XII Effect of HF genes percentage: Philipsson J., G. Ral, B. Berglund, 1995. Somatic cell count as a selection criterion for mastitis resistance in dairy cattle. (Livestock Production

6、 Science) HF share may influence SCS;,Selected references III. Days in milk (in Polish cattle),Ptak E., Brzozowski P., Jagusiak W., Zdziarski K., 2007: Genetic parameters for somatic cell score for Polish Black-and-White cattle estimated with a random regression model. (Journal of Animal and Feed Sciences ),Strabel T., Jamrozik J. 2006. Genetic analysis of milk production traits of Polish Black and White cattle using large-scale random regression test-day models. (Journal of Dairy Science),The g

7、oal,The aim of the work was to apply nonlinear regressions on month of calving and on month of test to investigate seasonal changes in somatic cell content in milk of Polish HF cows.,Data (1),over 12 600 000 test milking results about 880 000 cows first, second and third lactation 5 984 860, 4 139 104, 2 519 366 test results calving in 1997-2007, 1998-2007, 1999-2007 average SCS: 3.48, 3.92, 4.19,Data (2) average SCS by month of calving - lactations I - III,Data (3) average SCS by month of test

8、- lactations I - III,Methods (1),y - SCS (dependent variable) t - time (independent variable); 0 t 12 time scale - months of the year (month of calving or month of test milking) a0 - lactation mean of SCS a1 amplitude of seasonal changes of SCS a2 phase shift in months,Equation to fit to the data (each lactation separately):,Methods (2),Curve fitting - grid search phase,Calving month: a0 = 3.0 to 4.5 by 0.1 a1 = -0.2 to 0.2 by 0.05 a2 = 1.0 to 4.0 by 0.5 Test month: a0 = 3.4 to 4.3 by 0.1 a1 = 0

9、.0 to 0.20 by 0.05 a2 = -6 to 6 by 1;,Curve fitting - Iterative phase Gauss-Newton method,Hardware,IBM BladeCenter HS21 cluster (“mars“),One of 56 nodes - containing: - 2 Intel Xeon Dual Core processors (2.66 GHz) - 8 GB memory - hard disk 36.4 GB,Software,IBM BladeCenter HS21 cluster (“mars“),operating system : Linux RedHat SAS (Statistical Analysis System) version 9.1.3 documentation: http:/ remarks,The NLIN procedure of SAS was used. For examining the effect of the month of calving, grid search time was: 1h2658, 1h0002 and 0h3513 for lactations 1, 2 and 3, respectively. For estimating the effect of test month: 0h5619, 0h3903 and 0h232 Without iterative phase, about 330 in both cases.,Results for 1st lactation (1) grid search - residual sum of squares for phase shift = +1month,Results for 1st l

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