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PubMed2006

Genetic parameter estimates for scrotal circumference and semen characteristics of Line 1 Hereford bulls.

The objectives of this study were to estimate heritability for scrotal circumference (SC) and semen traits and their genetic correlations (rg) with birth weight (BRW). Semen traits were recorded for Line 1 Hereford bulls (n = 841), born in 1963 or from 1967 to 2000, that were selected for use at Fort Keogh (Miles City, MT) or for sale. Semen was collected by electroejaculation when bulls were a mean age of 446 d. Phenotypes were BRW, SC, ejaculate volume, subjective scores for ejaculate color, swirl, sperm concentration and motility, and percentages of sperm classified as normal and live or having abnormal heads, abnormal midpieces, proximal cytoplasmic droplets (primary abnormalities), bent tails, coiled tails, or distal cytoplasmic droplets (secondary abnormalities). Percentages of primary and secondary also were calculated. Data were analyzed using multiple-trait derivative-free REML. Models included fixed effects for contemporary group, age of dam, age of bull, inbreeding of the bull and his dam, and random animal and residual effects. Random maternal and permanent maternal environmental effects were also included in the model for BRW. Estimates of heritability for BRW, SC, semen color, volume, concentration, swirl, motility, and percentages of normal, live, abnormal heads, abnormal midpieces, proximal cytoplasmic droplets, bent tails, coiled tails, distal cytoplasmic droplets, and primary and secondary abnormalities were 0.34, 0.57, 0.15, 0.09, 0.16, 0.21, 0.22, 0.35, 0.22, 0.00 0.16, 0.37, 0.00 0.34 0.00, 0.30, and 0.33, respectively. Estimates of rg for SC with color, volume, concentration, swirl, motility, and percentages of live, normal, and primary and secondary abnormalities were 0.73, 0.20, 0.77, 0.40, 0.34, 0.63, 0.33, -0.36, and -0.45, respectively. Estimates of rg for BRW with SC, color, volume, concentration, swirl, motility, and percentages live, normal, and primary and secondary abnormalities were 0.28, 0.60, 0.08, 0.58, 0.44, 0.21, 0.34, 0.20, -0.02, and -0.16, respectively. If selection pressure was applied to increase SC, all of the phenotypes evaluated would be expected to improve. Predicted correlated responses in semen characteristics per genetic SD of selection applied to SC were 0.87 genetic SD or less. If selection pressure was applied to reduce BRW, the correlated responses would generally be smaller but antagonistic to improving all of the phenotypes evaluated. Predicted correlated responses in SC and semen characteristics per genetic SD of selection applied to BRW were less than 0.35 genetic SD.

Animals↗
PubMed1983

Genetic and phenotypic parameters estimated from Nebraska specific-pathogen-free swine field records.

Records collected during 1971 through 1979 from 101,606 hogs raised in 18 Nebraska Specific Pathogen Free herds were analyzed. Traits considered were backfat at 100 kg (BF), weight at 140 d of age (WT) and, in some analyses, number of live pigs/litter at birth (NBA). The phenotypic correlation of BF and WT, averaged across herds, was -.07. The correlations between BF and NBA and between WT and NBA were .04 and -.05, respectively. Average phenotypic standard deviations for BF, WT and NBA were 2.6 mm, 8.8 kg and 2.0 pigs. Estimates of the heritability of BF and WT were lower than most estimates reported from university research herds. Within breed, herd and sex estimates of heritability ranged from -.22 and .51 (unweighted mean = .16 +/- .025) for BF and ranged from -.28 to .49 (mean = .16 +/- .016) for WT. Estimates of the genetic correlation between BF and WT were extremely variable (mean = -.62 +/- 14.3, range = -9.42 to 1.30) among breed-herd-sex subclasses.

Adipose Tissue↗
PubMed1986

Genetic parameter estimates for reproductive traits of male and female littermate swine.

Reproductive traits of purebred and crossbred pigs produced in a four-breed diallel mating system using the Duroc, Landrace, Spotted and Yorkshire breeds were collected for five consecutive farrowing seasons (two farrowing seasons/year) beginning in fall 1976. Paternal half-sib heritabilities and genetic correlations for testicular traits (120 boars from 36 sires), serum testosterone (TE) and luteinizing hormone (LH) concentrations before and after treatment with gonadotropin releasing hormone (GnRH; 131 boars from 37 sires) and breeding performance traits (151 boars from 38 sires) were estimated. Heritability estimates were generally small to moderate except for sperm/gram testis (SGT), LH concentrations before (LHO) and at 3 h (LH3) after treatment with GnRH (.73 +/- .48, .61 +/- .46 and 1.19 +/- .45, respectively). A large positive genetic correlation was found for LHO with LH3 (.94 +/- .39), while a negative relationship existed for LH3 with TE concentrations at 3 h after GnRH injection. The genetic correlation between a boar's average first service conception rate and average conception rate also was significant (.82 +/- .54). Genetic correlations among littermate traits would suggest that selection for decreased age at puberty in gilts could cause an increase in LH concentrations in boar offspring, before and after GnRH injection, and may also have adverse effects on their ability to settle females. Selection for increased weight at puberty of gilts could cause TE concentrations of boar offspring to increase while having little effect on their breeding performance.

Animals↗
PubMed1988

Genetic parameter estimates for preweaning traits of beef cattle in a stressful environment.

Data collected from 1957 through 1985 from a Hereford herd located in the Southwest were analyzed separately for each sex to evaluate the heritabilities of and genetic correlations among preweaning growth traits within groups of environmentally similar years. Data were grouped into years with poor, moderate and good environments based on contemporary group means for male calves' weaning weight. A total of 7,690 records were analyzed for birth weight, weaning weight and preweaning daily gain with a model that included year of birth, sire within year of birth, age of dam and a covariate of day of birth for birth weight or age at weaning for the weaning traits. Year of birth was a significant source of variation in all environments for all traits, accounting for more of the variation in the good and poor years than in moderate years. Heritability estimates for all traits were greater in good and moderate years than in poor years for bull calves. For heifers, however, estimates for weaning weight and preweaning daily gain were greater in the poor environment. Genetic correlations among birth weight and preweaning gain increased from the good environment to the poor environment (-.49 +/- .26 to .82 +/- .56 for male calves and -.09 +/- 2.6 to .46 +/- .25 for female calves) but phenotypic correlations were near zero in all environments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Genetic component of heat stress in dairy cattle, parameter estimation.

Our data included 119,205 first-parity, test-day records from 15,002 Holsteins in 134 Georgia farms with temperature and humidity data from 21 weather stations throughout Georgia. The test-day model included the effects of herd test date, days-in-milk (DIM) classes, age, milking frequency, general additive effect, random regression on the heat-humidity index for heat-tolerance additive effect, general permanent environment, and the random regression on the heat-humidity index for a permanent environment. The general effects, which corresponded to effects in the current repeatability models, were assumed to be correlated with the heat-tolerance effects. Variance components were estimated by REML. For heat-humidity indices below 72, heritability for milk was 0.17, and additive variance of heat tolerance was 0. For a heat-humidity index of 86 (which would correspond to temperatures of 36 degrees C at 50% humidity), the additive variance of heat tolerance was as high as for general effect, and the genetic correlation between the two effects was -0.36. Results for fat and protein were similar. Current selection for production reduces heat tolerance. Joint selection for heat tolerance and production is possible.

Animals↗
PubMed2005

Genetic parameter estimates of portuguese dairy cows for milk, fat, and protein using a spline test-day model.

A spline animal model was fitted to 152,103 test-day milk, fat, and protein yield records from 14,423 first-lactation cows. The models included age at calving and the herd-test-month as fixed effects. Model fitting was carried out using Restricted Maximum Likelihood with ASREML. For milk yield, the heritability at 18 d in milk was 0.19, which increased to the maximum estimated value of 0.23 at midlactation and then decreased. On average, milk, fat, and protein yield heritabilities were 0.22, 0.14, and 0.19, respectively. For milk yield, all correlations were positive and ranged from 0.54 to 0.99 for the genetic component and from 0.32 to 0.78 for the phenotypic component. Genetic correlations were higher than phenotypic ones. For fat and protein yields, all genetic correlations were positive, ranging from 0.43 to 0.99. The phenotypic correlations for fat yield had the lowest correlations of the 3 traits. Curves of estimated breeding values for milk, fat, and protein over lactation had positive deviations from mean curves for sires with high genetic merit, but there was considerable variability in the shapes of the curves for different sires. More research is needed to compare the spline function with other mathematical functions used as submodels of lactation curve.

Animals↗
PubMed1997

Effect of inaccurate parameter estimates on genetic response to marker-assisted selection in an outbred population.

The effect of inaccurate estimates of variance and of the location of the quantitative trait locus on the genetic response to marker-assisted selection was studied by simulation of an adult multiple ovulation and embryo transfer nucleus breeding scheme. Two genetic models were simulated for the quantitative trait locus: a total of 10 alleles or 2 distinct alleles per base parent. For both models, the locus explained either 5 or 10% of phenotypic variance. A polygenic component was simulated, and the two genetic components were summed to 35% heritability for a trait measured on females. Overestimation of variance of the quantitative trait locus had minimal effect on genetic gain for marker-assisted selection over the short term, but decreased long-term response. The long-term loss was reduced when variance of the quantitative trait locus was reestimated after four generations of marker-assisted selection. Selection for favorable alleles at a nonexistent quantitative trait locus resulted in first generation losses of 3 and 7% for postulated quantitative trait loci, explaining 5 and 10% of variance, respectively. The larger the degree of error in location, the larger was the genetic loss compared with the correct location scenario. For the largest simulated location error of 15 cM, genetic superiority of marker-assisted selection was reduced by 80% in the first generation. We concluded that studies should be undertaken to verify estimates of quantitative trait locus and location to make optimal use of marker-assisted selection.

Alleles↗
PubMed1999

Effect of milk protein genotypes on milk protein composition and its genetic parameter estimates.

The effects of kappa-casein (CN) and beta-lactoglobulin (LG) genotypes on milk protein concentration and composition were estimated for the US Holstein-Friesian population using a single-trait, mixed, linear animal model on 592 individual milk samples from 233 cows. Both milk protein genotypes had no statistically significant effect on the total milk protein concentration; however, substitution of the kappa-CN A allele additively increased the proportion of kappa-CN, and substitution of the beta-LG B allele additively increased the proportion of beta-LG in total milk protein. In response, proportions of the other milk proteins, mainly alpha S1-CN, were decreased. For proportions of alpha S1-CN, kappa-CN, and beta-LG in total milk protein, kappa-CN and beta-LG genotypes explain more than 50 and 25% of the heritability and repeatability estimates, respectively. We concluded that kappa-CN and beta-LG genotypes affect the phenotypic and genetic variation of milk protein composition but do not significantly affect milk protein concentration. A possible explanation for our conclusion is that altered gene sequences in the promoter region of kappa-CN B and beta-LG A, linked closely to the respective genotypes, favor the transcription or translation of their own protein at the expense of the synthesis of other milk proteins, in particular of alpha S1-CN.

Alleles↗
PubMed2002

[Parameter estimation for Rasch type items that have never been used].

This study proposes a new conjoint model with orthogonal array using the notation of the structural equation modeling. It is shown that commonly available computer programs such as LISREL (Jöreskog & Sörbom, 1993) and LISCOMP (Muthen, 1984) can be used to estimate the worth values of conjoint measure and item response curves of the Rasch type and graded response type. One remarkable feature of this method is that the response curves of items that have never been used, can be constructed. The constructed distribution functions were compared with the empirical distribution functions of cross validation data. The proposed method seemed to work well, because these functions were very similar to each other.

Models, Psychological↗
PubMed1985

Phasic ion channel blockade. A kinetic model and parameter estimation procedure.

For excitable membranes, use and frequency dependence represent a progressive incorporation of drug into gated ion channels with repetitive stimulation. In contrast to receptors where access to ligand is continuous in time, we define guarded receptors, such as gated ion channels, as receptors whose access to the ligand pool is transient and controlled by the channel-gating process. During repetitive stimulation, the fraction of ligand-bound channels (ion channel blockade) follows an exponential time course, determined by the interstimulus interval, channel-gating processes, drug concentration, and the forward and reverse rate coefficients characteristic of the binding process. Based on a first order model of ligand-receptor binding, we derive a characterization of ion channel blockade via a single diffusion path under conditions of repetitive phasic stimulation. Extension to multiple diffusion paths and multiple drugs leads to a more complex scheme, but these generalizations are straightforward. For the case of one diffusion path, we derive the steady state level of channel blockade for guarded receptors as a function of stimulus rate and develop a data analysis strategy suitable for characterizing ion channel-blocking agents such as local anesthetics and antiarrhythmic drugs. We show that as receptor access time increases, the transient and steady state properties of guarded receptors become equivalent to those derived from the standard continuous access ligand-receptor model. The analysis tools presented simplify the quantitative description of the functional properties of many ion channel blockers and appear to have general applicability to characterization of periodically accessible receptors.

Animals↗
PubMed1988

Dynamic ventilation scintigraphy: a comparison of parameter estimation gating models.

Two procedures for providing the synchronization of ventilation scintigraphic data to create dynamic displays of the pulmonary cycle are described and compared. These techniques are based on estimating instantaneous lung volume by pneumotachometry and by scintigraphy. Twenty-three patients were studied by these two techniques. The results indicate that the estimation of the times of end-inspiration and end-expiration are equivalent by the two techniques but the morphologies of the two estimated time-volume waveforms are not equivalent. Ventilation cinescintigraphy based on time division gating but not on isovolume division gating can be equivalently generated from list mode acquired data by employing either technique described.

Humans↗