Data from a survey performed from 1986 to 1990 were analyzed to assess the effects of diseases on length of productive life of 3589 Holstein cows from 47 herds, using a proportional hazard model. The probability of a cow being culled, or hazard function, was supposed to be the product of an unspecified baseline hazard function and log-linear, time-dependent explanatory variables that possibly i...

A total of 989,582 test-day records of 160,243 first-parity cows collected from 131 herds of Iranian Holstein dairy cows from 1995 to 2014 by the Animal Breeding and Improvement Centre of Iran, were used to determine the best model for lactation curves of fat to protein ratio (FPR) and somatic cell scores (SCS) in the first lactation. Several mathematical models including the Wood (WD), Wilmink...

The Norwegian cow index of 1978 is described. The formula is standard and is based on information from a) lactation yield per year, b) corresponding herd averages, c) indexes of sire and maternal grandsire, and d. average of indexes of sires included in the herd averages. Analysis of data from 242 501 cows is also presented. Following conclusion may be drawn :-The cow index used seems to work w...

Information on the presence or absence of bacterial infections and abnormal secretions in each quarter of cows in their initial survey on the New York State Veterinary College Mastitis Program was used to obtain several criteria of udder infection. Year-season and stage of lactation effects were statistically significant for several criteria of infection in first, second, and later lactation gr...

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) herd...

the aim of the present study was to estimate the genetic parameters and genetic trends of somatic cell score (scs) in the first 3 lactations of iranian holstein cows by random regression (rr) animal model by using restricted maximum likelihood (reml) method. the data set used in this analysis included observations of 340318 test-day records of 41526 cows in 288 herds; 89969 test-day of 11750 co...

This experiment was conducted to determine the association between several risk factors which may affect culling of the Iranian Holstein cows. The data consisted of 329,772 lactation records collected by the Animal Breeding Center of Iran (2003 to 2012).The logistic regression was applied to investigate the associations between the response variable, the risk of culling, and predictor variables...