We first sought to clarify the effects of discounted rate, survival rate, and lactation persistency as a component trait of the selection index on net merit, defined as the first five lactation milks and herd life (HL) weighted by 1 and 0.389 (currently used in Japan), respectively, in units of genetic standard deviation. Survival rate increased the relative economic importance of later lactati...

variace / covariance components of 227118 first lactaiom test-day milk yield records belonged to 31258 iranian holstein cows were estimated using nine random regression models. afterwards, different measures of persistency based on estimation breeding value were evaluated. three functions were used to adjust fixed lactation curve: ali and schaeffer (as), quadratic (le3) and cubic (le4) order of...

Cows with high persistency tend to produce less milk than expected at the beginning of lactation and more than expected at the end. Best prediction of persistency was calculated as a function of a trait-specific standard lactation curve and a linear regression of test-day deviations on days in milk. Regression coefficients were deviations from a balance point to make yield and persistency pheno...

in the research the genetic investigation productive and reproductive traits and changes trend the traits in years, seasons and different lactation periods and genetic evaluation cows and bulls of 785 records for milk and 665 records for fat yield and reproductive information during years 1998 to 2003 of 207 dairy cows ghezlagh farm aboureyhan campus (university of tehran) studied. the least sq...

The objectives of this study were to analyze the genetic properties of three measures of lactation persistency in Polish Holstein-Friesian cows, and possibly to choose one measure which could be used for estimation of breeding value for lactation persistency in the Polish dairy cattle population. Data included 117,327 first three lactations of 110,141 cows calved in 1995-2009. The lactation cur...

Cows with high lactation persistency tend to produce less milk than expected at the beginning of lactation and more than expected at the end. Best prediction of lactation persistency is calculated as a function of trait-specific standard lactation curves and linear regressions of test-day deviations on days in milk. Because regression coefficients are deviations from a tipping point selected to...

the aim of this study was to investigate the effect of milking frequency (three times daily vs. two times daily) on the lactation curve shape, partial and 305-d lactation performance in holstein dairy cows in iran. data from february 2000 to december 2012 comprising 217345 lactations on 141364 cows distributed in 324 herds collected by the animal breeding center of iran were used. the mean milk...

Estimation of genetic trends is necessary to monitor and evaluate selection programs. The objective of this study was to estimate the genetic trends for milk yield in Iranian Holsteins cows using random regression test day model. Data set was consisted of 743205 test-day records from 1991 to 2008, which were collected by the Animal Breeding Centre of Iran. Breeding, environmental and phenotypic...

The aim of this study was to investigate the effect of milking frequency (three times daily vs. two times daily) on the lactation curve shape, partial and 305-d lactation performance in Holstein dairy cows in Iran. Data from February 2000 to December 2012 comprising 217345 lactations on 141364 cows distributed in 324 herds collected by the Animal Breeding Center of Iran were used. The mean milk...