the aim of this study was to estimate genetic parameters of age at first calving and its relationship with productive traits of holstein dairy cows. a total of 24491 first lactation records (2x 305d) which were collected from 1995 to 2009 were used. the general linear model (glm) procedure was applied to determine effective factors on studied traits. herd-year-season (hys) and age at first calv...

The performance of pigs is influenced by genetic and environmental factors. Both the genetic merit of the pigs and the environment they are raised in have to be improved continuously to optimise progress in performance. In addition, the requirements of genotypes available today may have changed due to selection and the management of pigs has to be adopted accordingly to maximise phenotypic perf...

introduction lamb production is the largest part of income in sheep industry. therefore, the mortality rate of lambs is a key factor in profit of the sheep breeding. mortality rate of lambs (or lamb mortality rate) in different breeds of sheep under different climatic conditions is varying from 15% to 50% and an average of 9% to 20% has been reported. survival rate is a combination trait that i...

a data file containing 607662 (317608) milk (open days) records belonging 294417 (177838) holstein cows that were calved from 1983 to 2008 was used. the bivariate repeatability model was used for data analyzing so that herd, calving year, calving month, days in milk (only for milk trait) and calving age for each parity, were assumed as fixed effects and additive genetics and permanent environme...

this study was carried out to investigate the effect of selection on the reduction of fat-tail size in lori-bakhtiari lambs. the study lasted for five years at the development and breeding center of lori-bakhtiari sheep station. estimation of fat-tail weight, using external fat-tail dimensions was obtained from regression procedure at 6 month age. soft tissue depth at the point 12 cm from the m...

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data related to yazd native fowls (obtained during 2000-2008) yazd native fowls were made use of in the present study. the investigated traits consisted of body weight at 8 (bw8) and 12 weeks (bw12), age at sexual maturity (asm), egg number during the first three months of production period (en) and the mean egg weight at 28, 30 and 32 weeks of age (ew). the genetic and phenotypic parameters we...

this investigation aimed to assess genetics of body conformation and feed efficiency traits in a control line of rhode island red (rir) chicken taking single hatched out pedigreed 100 chicks at central avian research institute, izatnagar, india. data was analyzed by least squares analysis of variance. least squares means of chick weight (cw), body weight (bw), shank length (sl), keel length (kl...