Genetic and Environmental Smoothing of Lactation Curves with Cubic Splines

White, Ian; Thompson, R.; Brotherstone, S.

doi:10.3168/jds.s0022-0302(99)75277-x

Cited by 136 publications

(149 citation statements)

References 6 publications

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“…Using the sum may be reasonable if the genetic influence is constant over time. However, studies have shown that correlations between measurements differ over the lactation [2,24].…”

Section: Discussionmentioning

confidence: 99%

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Detection and modelling of time-dependent QTL in animal populations

et al. 2008

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-A longitudinal approach is proposed to map QTL affecting function-valued traits and to estimate their effect over time. The method is based on fitting mixed random regression models. The QTL allelic effects are modelled with random coefficient parametric curves and using a gametic relationship matrix. A simulation study was conducted in order to assess the ability of the approach to fit different patterns of QTL over time. It was found that this longitudinal approach was able to adequately fit the simulated variance functions and considerably improved the power of detection of time-varying QTL effects compared to the traditional univariate model. This was confirmed by an analysis of protein yield data in dairy cattle, where the model was able to detect QTL with high effect either at the beginning or the end of the lactation, that were not detected with a simple 305 day model. QTL detection / longitudinal data / random regression models

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“…Using the sum may be reasonable if the genetic influence is constant over time. However, studies have shown that correlations between measurements differ over the lactation [2,24].…”

Section: Discussionmentioning

confidence: 99%

“…It is likely that these biological components influence the QTL expression, which will result in non constant QTL effects over time. In fact evidence from polygenic studies suggest that the additive genetic variance changes over lactation stages for production traits in dairy cattle [2,7,18,24].…”

Section: Introductionmentioning

confidence: 99%

Detection and modelling of time-dependent QTL in animal populations

et al. 2008

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“…Regression splines (White et al, 1999) were used to model lactation curves. Six-knot regression splines, with knots positioned at days 7, 20, 50, 135, 245 and 335, were considered to be an accurate way to model lactation curves (Druet et al, 2003).…”

Section: Datamentioning

confidence: 99%

“…These models differ in the way the lactation curve is modelled as a function of days in milk (DIM), with fixed classes, parametric or semi-parametric (splines) curves; in the way the genetic and permanent environment components are described (fixed or random regression using Legendre or other polynomials); and in the way heterogeneous residual variances are accounted for. In France, regression splines (White et al, 1999) were chosen to model lactation curves (Druet et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Environmental effects on lactation curves included in a test-day model genetic evaluation

Leclerc

Duclos²,

Barbat³

et al. 2008

Animal

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A large number of environmental factors affect the daily milk production of a cow. Lactation curves included in the French test-day model are modelled as a function of days in milk with semi-parametric curves (splines). The proper modelling of environmental effects in the test-day analysis was investigated using test-day records collected from the first three lactations of French Montbé liarde cows from 1988 to 2005. Four lactation-curve effects describing calving month, length of dry period, age at calving and gestation defined within parity-class were fitted. The shape of lactation curves did not depend on year of calving, which can be modelled as a constant over the whole lactation. To reduce computational requirements and time, data were pre-adjusted in a first step for fixed effects with no year interaction, and then used for genetic evaluation. Correlations for each lactation between 305-day estimates of genetic and permanent environment effects computed using pre-adjustment factors obtained at a 4-year interval were virtually one. The use of a two-step procedure had a very limited impact on the estimates of genetic and permanent environment effects. The minimum correlations with values estimated with a one-step procedure were 0.9984 and 0.9974, respectively. The knowledge of systematic environmental effects affecting the cow daily yield through lactation curves offers interesting perspectives to predict future daily milk production.

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“…Future research should investigate alternative, more parsimonious models. On the one hand, these could include parametric curves (linearised if applicable) or splines, similar to applications to model test day yields in dairy cattle (see [4] and [42], respectively). On the other hand, there may be scope to reduce the number of parameters by modelling the within animal, permanent environmental covariance structure invoking a parametric correlation function described by one or two parameters in conjunction with a variance function to allow for heterogeneous variances (e.g.…”

Section: Alternative Modelsmentioning

confidence: 99%

Estimates of direct and maternal covariance functions for growth of Australian beef calves from birth to weaning

Meyer

2001

Genet. Sel. Evol.

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-Records for birth and subsequent, monthly weights until weaning on beef calves of two breeds in a selection experiment were analysed fitting random regression models. Independent variables were orthogonal (Legendre) polynomials of age at weighing in days. Orders of polynomial fit up to 6 were considered. Analyses were carried out fitting sets of random regression coefficients due to animals' direct and maternal, additive genetic and permanent environmental effects, with changes in variances due to temporary environmental effects modelled through a variance function, estimating up to 67 parameters. Results identified similar patterns of variation for both breeds, with maternal effects considerably more important in purebred Polled Herefords than a four-breed synthetic, the so-called Wokalups. Conversely, repeatabilities were higher for the latter. For both breeds, heritabilities decreased after birth, being lowest when maternal effects were most important around 100 days of age. Estimates at birth and weaning were consistent with previous, univariate results. covariance functions / early growth / modelling / beef cattle / maternal effects

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Genetic and Environmental Smoothing of Lactation Curves with Cubic Splines

Cited by 136 publications

References 6 publications

Detection and modelling of time-dependent QTL in animal populations

Detection and modelling of time-dependent QTL in animal populations

Environmental effects on lactation curves included in a test-day model genetic evaluation

Estimates of direct and maternal covariance functions for growth of Australian beef calves from birth to weaning

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