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Journal of Dairy Science – Editor's Choice for Article of the Month (December 2016)

November 17th, 2016

Genetic and phenotypic analysis of daily Israeli Holstein milk, fat, and protein production as determined by a real-time milk analyzer
J. I. Weller* 1  and E. Ezra†

*Institute of Animal Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel 
†Israel Cattle Breeders Association, Caesaria Industrial Park 38900, Israel



The objective was to test the hypothesis that more frequent but less accurately analyzed milk components may give a more representative measure of a cow’s total lactation production. Daily records for milk production and fat and protein concentration collected by the AfiLab recording system (Afimilk, Kibbutz Afikim Israel)  from  January  2014  to  January  2016  from  47 large  kibbutz (communal)  herds  distributed  through-out Israel with a total of 37,486 Israeli Holstein cows were compared with the same statistics derived from monthly test day records derived by Bentley and Foss milk analyzers at the central laboratory of the Israel Cattle Breeders Association. The lactation means for all traits were quite similar for the 2 methods in both parities, except for fat production, which was lower for the daily records. This finding corresponded to fat lactation curves, which showed that daily results were lower with low days in milk (DIM) but almost equal to the monthly results after 125 DIM. Relative to monthly records, daily records overestimated protein percentage before 150 DIM and underestimated protein percentage in the second half of the lactation. The standard deviation for first- and second-parity daily records scored by the monthly and daily system were least similar for fat percentage, but even for this trait the difference was no more than 0.1 percentage points. The standard sdf deviations  for  complete  lactation production  were  slightly lower  for  the  daily  results  for  all  trait  but  protein production.  

First party heritability's  were  higher  for lactations  computed  from  daily  records  for  all  traits except for protein percentage, but differences were not significant. For daily records, coefficients of determination to predict future milk, fat, and protein lactation production  from  truncated  lactations  were  greatest and root mean squared errors were least if the mean production  from  the  last  2  weeks  before  the  truncation date was used to estimate future production. Daily first-parity partial lactations for milk, fat, and protein production with <150 DIM predicted future lactation more accurately than corresponding monthly partial lactations. With only 30 DIM, genetic correlations between predicted and actual lactations ranged from 0.73 to 0.79 for milk, fat, and protein production. Real-time daily recording of fat and protein concentration by the daily recording system may be preferable to monthly analysis for herd-management decisions and genetic evaluation.  Further study is required to compare the results of individual cows in multiple lactations.


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