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J F Keown

Publications and source records attributed to J F Keown.

6 recordsLinked to original sources
PubMed1996

Effect of variance of interaction effects of sire and herd on selection for milk and fat yield.

The animal model for genetic evaluations of dairy cattle by the USDA currently includes a term for interaction effects of sire and herd. The relative magnitude of the variance of that effect was established in the 1960s as 14% of the total variance, but recent research has shown that the proportion is 2% or less. This report compared EBV using either the 14% or the actual estimate from 20 samples of records from herds in California, New York, and Pennsylvania. From 6 to 22% of bulls or cows selected for milk and fat yields based on evaluation with 14% of the total variance would not be selected using the sample estimates, depending on selection intensity, region, and whether only first or up to three lactations were used in the evaluations. Nevertheless, the average EBV of the bulls and cows selected based on 14% of the total variance were only slightly less than for those selected on 2%. This pilot research suggests that further study of the national data be done to establish the appropriate proportion of variance from interaction effects of sire and herd to use with national evaluations. Kinds of evaluations of bulls and ages of cows and bulls should be considered.

Animals↗
PubMed1995

Variance of interaction effects of sire and herd for yield traits of Holsteins in California, New York, and Pennsylvania with an animal model.

An animal model with a REML algorithm was used to estimate variances of additive genetic effects and interaction effects of sire and herd. Milk and fat yields were analyzed for first, second, and third lactations of Holsteins from California, New York, and Pennsylvania. Twenty samples of data were used in the study: 10 from California, 4 from New York, and 6 from Pennsylvania. Mean number of lactations per sample was 36,820 from 18,189 cows in 156 herds. Mean fractions of phenotypic variance of interaction effects of sire and herd for milk and fat yields were .015 and .019 for first lactation and .019 and .021 for all (up to three) lactations rather than the .14 used for national genetic evaluations in the US. Mean heritability estimates for milk and fat yields were .26 and .24 for first lactation and .21 and .21 for all lactations in California and .34 and .35 for first lactations and .28 and .29 for all lactations in New York. Sums of variances of permanent environmental and interaction effects of sire and herd were similar to those used for national genetic evaluations in the US. Analysis of another 10 samples from California and 10 samples from New York showed only slightly different fractions of phenotypic variance for milk yield for interaction effects of sire by herd, sire by herd by year, and sire by herd by year by season: .023, .027, and .037 for California and .023, .017, and .023 for New York, respectively.

Animals↗
PubMed1995

Estimates using an animal model of (co)variances for yields of milk, fat, and protein for the first lactation of Holstein cows in California and New York.

First lactation yields of milk, fat, and protein from Holstein cows in New York and California were used to obtain REML estimates of (co)variances for yield traits using a multitrait animal model. Data from each state were split randomly into 10 samples, averaging 5504 cows per sample from California and 5078 from New York. Mean heritability estimates for milk, fat, and protein yields were .30 +/- .02, .31 +/- .01, and .29 +/- .01 for California data and .33 +/- .01, .35 +/- .01, and .30 +/- .01 for New York data. Averages of genetic correlation estimates for California and New York were .63 +/- .01 and .52 +/- .02 between milk and fat, .84 +/- .01 and .83 +/- .01 between milk and protein, and .73 +/- .01 and .68 +/- .01 between fat and protein. Estimates of environmental correlations were larger than estimates of genetic correlations. Mean estimates of phenotypic correlations for California and New York were .75 +/- .01 and .72 +/- .01 between milk and fat, .92 +/- .01 and .91 +/- .01 between milk and protein, and .81 +/- .01 and .79 +/- .01 between fat and protein yields. On average, these estimates agree with those obtained from animal models with limited rounds of iteration for small data files.

Animals↗
PubMed1986

Effect of days carried calf, days dry, and weight of first calf heifers on yield.

Effects of days carried calf, days dry, and weight of first calf heifers were studied using records of Holstein cows processed at the Northeast Dairy Records Processing Laboratory between July 1980 and August 1984. Multiplicative factors were estimated for days carried calf for milk, fat, and protein using a model that adjusted for the age-month and herd-year of freshening. Factors developed show a close relationship between protein and milk with fat factors being smaller. Factors also are smaller than others reported in the literature. First lactation factors differed from second and third lactation factors. Analysis of days dry indicated that optimum number of days dry between lactations 1 and 2, 2 and 3, and 3 and 4 for maximized subsequent yield was 51 to 60 d dry for all lactations. Calculated F values showed greater significance for days dry than age-month of freshening. Optimum freshening weight of a first calf heifer to maximize first lactation milk yield is between 544 and 567 kg. The F values for weight at freshening were more significant than age-month of freshening.

Animals↗
PubMed1984

Evaluation of the genotoxic and embryotoxic potential of chlorpyrifos and its metabolites in vivo and in vitro.

The genotoxicity and embryotoxicity of chlorpyrifos (CPF) and two metabolites were evaluated using the chick embryo, Chinese hamster ovary cells, and by examining blastocysts from superovulated cows crossed to chlorpyrifos-treated bulls. Chlorpyrifos and metabolites were dissolved in acetone and administered to 3-day embryos by the air cell method. The LD50 was 1,500 micrograms/embryo when mortality was checked through and including 17 days of development. The metabolites were more embryotoxic than the parent compound, CPF. Chlorpyrifos and metabolites did not increase the sister chromatid exchange (SCE) frequency above background at any dosage in the 3-day chick embryo assay. Similarly, none of these compounds increased SCE frequencies in three-point dosage tests (1, 10, 100 micrograms/ml) using Chinese hamster ovary cells. Controls in these assays consisted of the solvent carrier acetone (7.0 +/- 2.5 SCE/cell) and 8.6 micrograms/ml methyl methane sulfonate (30.5 +/- 7.4 SCE/cell). Studies of bovine blastocysts obtained from superovulated cows crossed with Dursban 44 treated bulls did not reveal evidence of chromosome aberrations or developmental anomalies associated with pesticide application. However, reproductive performance of breeders may be subnormal as a result of severe poisoning. This underscores the limitations of short-term assays and emphasizes the need to perform thorough toxicological assays of a chemical according to actual usage patterns in the species of concern.

Animals↗