Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

Nutrient requirements of dairy cattle , Nutrient requirements of dairy cattle , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Nutrient requirements of dairy cattle

生活習慣病とgenome-wide association study

Linear models

The effects of frame size (FS) and body condition score (BCS) on performance of Brahman cows were evaluated using records collected from 1984 to 1994 at the Subtropical Agricultural Research Station, Brooksville, Florida. Age at puberty (AP), calving rate (CR), calving date (CD), survival rate (SR), weaning rate (WR), birth weight (BWT), weaning weight (WWT), preweaning ADG, and kilograms of calf produced per cow exposed (PPC) were obtained from first- (n = 215), second- (n = 130), and third or greater-parity (n = 267) dams. Based on hip height at 18 mo of age, heifers were assigned to three FS groups: small (115 to 126 cm), medium (127 to 133 cm), or large (134 to 145 cm). Small and medium FS heifers attained puberty at younger (P < .05) ages (633.2 ± 12.3 and 626.4 ± 12.0 d) than large FS heifers (672.3 ± 17.1 d). Calving rate in large FS second-parity dams was 27% less (P < .05) than in small and medium FS dams. In third or greater-parity dams, CR was greater (P < .05) for small FS cows than for medium and large FS cows. Across the three parity groups, CR improved with increasing BCS. Except for the first-parity dams, animals with better fall BCS calved earlier (P < .05). In first-parity dams, SR was less (P < .01) in large (47.9 ± 11.0%) than in small (80.7 ± 5.2%) and medium (83.4 ± 4.7%) FS groups. Weaning rates of large FS first- and second-parity dams were less (P < .05) than those of small and medium FS dams. Second-parity dams with BCS 3 had lower (P < .05) WR than dams with BCS 4 and 5. Within first- and third or greater-parity dams, BWT of calves born to small FS cows were the lightest, and those born to large FS dams were the heaviest; those born to medium FS dams were intermediate (P < .05). In second-parity dams, BWT of calves of large FS dams were greater (P < .05) than those of small and medium FS dams. In first- parity dams, calves weaned by small FS cows had lower (P < .05) WWT than those weaned by higher FS cows. In the third or greater-parity group, large FS dams weaned heavier calves (P < .05) than other dams. In all parity groups of dams, calves out of large FS cows had greater ADG (P < .05) than those from small and me- dium FS cows. In first-parity dams, PPC was compara- ble between small and medium FS dams, but both tended to be greater (P < .10) than PPC of large FS dams. Small and medium FS females reached puberty at an earlier age, calved earlier, and had greater calv- ing, survival, and weaning rates, as well as greater kilograms of calf produced per cow exposed than the large FS females. As the large FS cows matured, they seemed to have overcome the negative effects imposed by FS that were observed at younger ages. Their perfor- mance traits were generally all comparable to those of smaller cows once they had reached maturity.

/pdf/influence-of-frame-size-and-body-condition-score-on-10zzxp8erx.pdf

Influence of frame size and body condition score on performance of Brahman cattle.

Genetic parameters were estimated for scrotal circumference (SC; n=287), age at puberty in heifers (AP; n=292), and hip height in both sexes (HH; n=684) for Brahman cattle born from 1984 to 1994 at the Subtropical Agricultural Research Station, Brooksville, Florida. Age at puberty was defined as the age (days) at first detected ovulatory estrus. Measurements of SC and HH were taken at 18 mo of age. Fixed effects considered in the SC model were year of birth (YOB), age of dam (AOD), and age at measurement (AGE) as a linear covariate. Fixed effects fitted to the AP model were YOB and AOD. Fixed effects in the HH model were YOB, sex, AOD, and AGE as a linear covariate. Variances and covariances were estimated using REML with a derivative-free algorithm and fitting a multiple trait animal model. Estimates of heritability for SC, AP, and HH were .28, .42, and .65, respectively. Estimates of genetic correlations between SC and AP, SC and HH, and AP and HH were -.32, .19, and .25, respectively. Estimates of environmental correlations were .19 between SC and HH, and -.13 between AP and HH. Estimates of genetic parameters indicate a favorable genetic relationship between SC in Brahman bulls and AP in Brahman heifers under subtropical conditions. There was also evidence that selecting Brahman bulls for HH would not adversely affect SC but would have some detrimental effect on AP in female progeny.

Estimation of genetic parameters for scrotal circumference, age at puberty in heifers, and hip height in Brahman cattle

Estimates of covariances and sire expected progeny differences of additive and nonadditive direct and maternal genetic effects for birth and weaning weights were obtained using records from 1,581 straightbred and crossbred calves from the Angus-Brahman multibreed herd at the University of Florida. Covariances were estimated by Restricted Maximum Likelihood, using a Generalized Expectation-Maximization algorithm applied to multibreed populations. Estimates of heritabilities and additive genetic correlations for straightbred and crossbred groups were within the ranges of values found in the literature for these traits. Maximum values of interactibilities (ratios of nonadditive genetic variances to phenotypic variances) and nonadditive correlations were somewhat smaller than heritabilities and additive genetic correlations. Sire additive and total direct and maternal genetic predictions for birth and weaning weight tended to increase with the fraction of Brahman alleles, whereas nonadditive direct and maternal genetic predictions were similar for sires of all Angus and Brahman fractions. These results showed that it is feasible to evaluate sires for additive and nonadditive genetic effects in a structured multibreed population. Data from purebred breeders and commercial producers will be needed to accomplish the same goal at a national level.

/pdf/covariance-components-and-prediction-for-additive-and-yf2cwaiaww.pdf

Covariance components and prediction for additive and nonadditive preweaning growth genetic effects in an Angus-Brahman multibreed herd.

Multibreed Sire Evaluation Procedures within a Country

Intrabreed additive genetic, environ- mental, and phenotypic variances and covariances for Romosinuano ( R ) and Zebu (Z), as well as interbreed nonadditive genetic variances and covariances (sire × breed-group-of-dam interactions), for birth weight (BWT), weaning weight (WW), and postweaning gain (GW) were computed using a Romosinuano-Zebu multibreed data set from the TuripanaExperiment Station in Colombia. Covariances were estimated with a sire-maternal grandsire model, using a multibreed REML procedure. The computing algorithm was a generalized expectation-maximization (GEM) al- gorithm. This algorithm yields no asymptotic standard errors as part of its computations. Because of the small size of the data set (2,546 calves), these REML covariance estimates should be viewed with caution. Estimates of intrabreed heritabilities were similar to the ratios of interbreed nonadditive to phenotypic variances (interactibilities) for direct and maternal effects of the growth traits evaluated in this study. Intrabreed heritability estimates for BWT, WW, and GW direct genetic effects were .16, .09, and .14, for R and .24, .10, and .14 for Z. Corresponding heritability values for maternal effects were .18, .09, and .23 for R and .14, .13, and .07 for Z. Interactibility estimates were .21, .05, and .12, for direct and .26, .04, and .11, for maternal BWT, WW, and GW. Negative correla- tions between additive maternal weaning weight and direct and maternal postweaning gain, as well as between environmental weaning weight and post- weaning gain, suggested that there was compensatory postweaning gain in this herd. Estimates of genetic variation and predictions of expected progeny differ- ences showed that Romosinuano animals competed well against Zebu and RZ crossbred animals under the tropical environmental conditions at Turipana ´ .

/pdf/additive-and-nonadditive-genetic-variability-for-growth-2grohidcp8.pdf

Mauricio A. Elzo

Papers

Influence of frame size and body condition score on performance of Brahman cattle.

Estimation of genetic parameters for scrotal circumference, age at puberty in heifers, and hip height in Brahman cattle

Covariance components and prediction for additive and nonadditive preweaning growth genetic effects in an Angus-Brahman multibreed herd.

Multibreed Sire Evaluation Procedures within a Country

Additive and nonadditive genetic variability for growth traits in the Turipaná Romosinuano-Zebu multibreed herd.