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Paper Information

Journal:   JOURNAL OF AGRICULTURAL SCIENCE (UNIVERSITY OF TABRIZ)   2007 , Volume 17 , Number 1; Page(s) 83 To 90.
 
Paper: 

STUDY ON SOME SUGGESTED MEASURES OF MILK YIELD PERSISTENCY IN HOLSTEIN DAIRY CATTLE OF IRAN

 
 
Author(s):  ATASHI H.*, MORADI SHAHR BABAK M., MOTAMEDIFAR M.
 
* DEPT. OF ANIMAL SCIENCE, FACULTY OF AGRICULTURE, UNIVERSITY OF TEHRAN, KARAJ, IRAN
 
Abstract: 

In this research, Phenotypic and genetic parameters were estimated for five persistency criteria of milk yield. The criteria included, the maximum production of all test-day records per lactation divided by the related mean, standard deviation of all test-day records of complete lactation, the percentage of daily milk retained from the peak to the end of lactation, the ratio of latest test-day yield record to the mean of all test-day yield records and a criterion which derived from estimated lactation curve factors in incomplete Gamma function. Data set comprised 36487 records of first lactation milk yields of Holstein dairy cattle of Iran with at least eight recorded test-days per lactation. Estimated heritabilities based on the univariate models were 0.32 for 305-days milk yield, and between 0.0469 to 0.0819 for persistency criteria. Estimated heritabilities based on the multivariate models were changed a little in comparison to univariate models. Genetic correlation between persistency criteria and 305-day milk yield were between -0.6124 to 0.6617. Genetic correlation between persistency criteria were between -0.9265 to 0.9988. Phenotypic correlation had similar trend to genetic correlation. The result showed that genetic correlation between milk yield and some persistency criteria were favorable for selection and breeding programs.

 
Keyword(s): HOLSTEIN DAIRY CATTLE, LACTATION CURVE, PERSISTENCY
 
References: 
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