With the objective of evaluating measures of milk yield persistency, 27,000 test-day milk yield records from 3362 first lactations of Brazilian Gyr cows that calved between 1990 and 2007 were analyzed with a random regression model. Random, additive genetic and permanent environmental effects were modeled using Legendre polynomials of order 4 and 5, respectively. Residual variance was mod...

Additive and dominance genetic variances were estimated for milk and fat yield in Canadian Holsteins using deriva-tivefree REML procedures. Traits were analyzed under two sire and dam models differing in assumptions on the data structure. Within herd, dam relationships were first defined to be hierarchical within sire to estimate the two genetic variances, assuming no maternal, epistatic geneti...

STATs are a family of latent transcription factors that reside in the cytoplasm of resting cells. The STAT1 transcription factor gene located on the chromosome 2 at interval 60 to 63 cM. This factor upon stimulation with INF gamma, dimerizes and translocate to the nucleus where mediates transcriptional regulation. In this study, we estimated the allele and genotype frequencies of STAT1/Pag<...

emphasis on milk yield (my) as well as milk yield persistency (myp) and calving interval (ci) is necessary to achieve more sustainable productionin dairy cattle. therefore the main objective of this study was to find an optimum regression model to estimate economic values for my, myp and ci.using a deterministic bio-economic model, seventyfiveproduction states differing mainly in my, mypand ciw...

The aim of the present study was to estimate genetic and phenotypic parameters of milk production traits in the first and second lactations of Romanian Simmental dairy cattle. For the estimation of variance, heritability, genetic and phenotypic correlations among milk yield, fat yield, protein yield, and percentages of fat and protein, 3400 first and second lactation records over a period of fi...

the objective of this study was to estimates the genetic and environmental components for the lactation curve parameters, milk yield, age at first calving (afc), calving interval (ci) and somatic cell count (scc) in iranian holstein cows. the dataset consisted of 210625 test day records from 25883 cows with milk yield in the first parity recorded from july 2002 to september 2007 in a total of 9...

In complex task domains, such as games, students may exceed their teachers. Such tasks afford diverse means to tradeoff one type of performance for another, combining task elements in novel ways to yield method variations and strategy discoveries that, if mastered, might produce large or small leaps in performance. For the researcher interested in the development of extreme expertise in the wil...

Milk yield, milk flow, and udder morphology traits were measured in 72 East Friesian crossbred multiparous ewes to estimate the variation in milk flow patterns present in this research flock, and to asses the repeatability of these measurements and their relationships with other lactation traits. A special milk flow apparatus designed for dairy ewes was used on two consecutive morning milkings ...

Some dairy farmers opt to omit one milking, either incidentally or weekly, without changing other milking times. This practice entails an extended milking interval of 24h (24h-MI), which is associated with a decrease in milk yield. This decrease varies among cows and could be partly due to factors such as stage of lactation and milk yield level. The aim of this study was to describe the average...

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...