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Biomedical subjects

A E Freeman

Publications and source records attributed to A E Freeman.

At least 37 records · Page 2Linked to original sources
PubMed1996

Relationships between polymorphism for mitochondrial deoxyribonucleic acid and yield traits of Holstein cows.

Two independent data files from the breeding herd of Iowa State University and six North Carolina herds were used to examine relationships between yield traits and mtDNA polymorphism. Maternal lineages were established by tracing ancestry of cows to founder females in the herd book of the Holstein Association. Data from Iowa State University were 1476 records from 602 cows from 29 maternal lineages. The nucleotides of mtDNA encoding rRNA were sequenced. Eleven sites of polymorphism were found. An animal model for gene substitution was used to examine the relationship between sequence differences and yield traits. Traits analyzed were mature equivalent yield of milk, fat, SNF, and milk energy as well as concentrations of fat, SNF, and milk energy. Effects of sequence differences were significant for most traits. Sequence information from the D-loop was available for 12 lineages from North Carolina. The effect of polymorphism at 4 sites was examined using 1472 records from 668 cows. Traits measured were the same, except that protein replaced SNF. No significant relationships existed between any of the traits and D-loop polymorphism, but results suggested that an association might exist between polymorphism and concentrations of milk yield, fat percentage, and energy. Whenever a significant relationship was detected, the effect of mutation (rare genotype) was detrimental.

Animals↗
PubMed1996

Multiple herd evaluation of the effects of maternal lineage on yield traits of Holstein cattle.

Effects of maternal lineage on yield traits were examined by using animal models. Data were 6054 multiparous records of 2264 cows from six herds in North Carolina and the breeding herd of Iowa State University. Separate analyses were performed by using first lactation records from North Carolina, all records from North Carolina, and pooled records from North Carolina and Iowa. Traits were mature equivalent yields of milk, fat, and protein; percentages of fat and protein; and milk energy concentration and yield. Cattle were assigned to maternal lineages on the basis of the earliest female ancestor recorded. Fixed effects in the models were herd-year-season, parity, and maternal lineage; random effects were animal, permanent environment, and residual. All additive genetic relationships were considered. For all analyses, maternal lineage was associated with significant differences in fat percentage and milk energy concentration. Differences between maternal lineages for yield traits were not significant. Variance components were also obtained with REML using the same data and models, but with lineage as a random effect. Based on records pooled from Iowa and North Carolina, maternal lineage accounted for 2.7% of the variance in fat percentage. Otherwise, < 1.2% of the variance of any trait was associated with maternal lineage.

Animals↗
PubMed1996

Impacts of cytoplasmic inheritance on genetic evaluations.

Simulation was used to examine the consequences of ignoring cytoplasmic effects on genetic evaluations. Effects on variance component estimation, accuracy of selection, genetic trend, and selection of bull-dams were considered. Comparisons were made for sire and animal models, several levels of cytoplasmic variance, and definition of cytoplasmic effects as either fixed or random. Ten replications with approximately 9000 cows and 20,000 records were simulated for each model and level of cytoplasmic variance. Derivative-free REML was used for estimation of variance components. Ignoring cytoplasmic effects caused overestimation of heritability with an animal model. Permanent environmental variance was underestimated with an animal model and overestimated with a sire model. Results were used for simulation of large (approximately 200,000 cow) data files for analysis of effects on accuracy of selection. Accuracy of selection increased when cytoplasmic effects were accounted for properly. Improvement of predicted breeding values was greater for cows than for sires and increased as cytoplasmic variance increased. Genetic trend also increased slightly, primarily as a function of increased accuracy of bull-dam selection. Little practical difference was detected when cytoplasmic effects were considered to be fixed rather than random.

Animals↗
PubMed1995

Study of immunological dysfunction in periparturient Holstein cattle selected for high and average milk production.

Data from twenty assays of traits associated with innate and adaptive immunity were evaluated from 137 periparturient Holstein cows. These cows had been selected through planned matings for four different levels of milk production (high and average pounds of milk, and high and average pounds of milk fat plus protein). For up to seven generations, the genetic lines were produced by mating females of each line to sires of corresponding merit. With the exceptions of neutrophil ingestion of Staphylococcus aureus and directed migration, all assays measuring neutrophil functions were depressed beginning 2 to 3 weeks before calving through 3 weeks after calving. Serum concentrations of immunoglobulin G1 decreased while those of immunoglobulin G2 increased around calving time. Serum complement and conglutinin concentrations decreased before calving and reached a minimum around calving time. Cows selected for high milk production (pounds of milk and pounds of milk fat plus proteins) had significantly higher (P < 0.10) numbers of circulating neutrophils and mononuclear cells, had higher (P < 0.10) neutrophil resting chemiluminescence and higher (P < 0.10) neutrophil directed migration than cows with average production potentials. There were significant (P < 0.001) sire progeny group differences for most traits associated with the immune system that we tested. These results can be considered encouraging, in that selection for high milk yield did not produce unfavorable correlated responses in the functional capacity of immune function traits, and that there is sufficient genetic variation in these immunological traits among sires of high genetic merit for milk production to potentially improve the immunocompetence of periparturient cows through planned mating experiments.

Animals↗
PubMed1995

Mastitis of periparturient Holstein cattle: a phenotypic and genetic study.

Environmental and genetic factors affecting somatic cell scores, clinical mastitis, and IMI by minor and major pathogens were studied on 137 periparturient Holstein cows selected for milk production. Environmental effects were obtained by generalized least squares and logistic regression. Genetic parameters were from BLUP and threshold animal models. Lactation number affected the number of quarters with clinical mastitis and the number of quarters infected with minor pathogens. The DIM affected somatic cell score and number of quarters infected with major pathogens. Heritabilities for all mastitis indicators averaged 10%, but differences occurred among the indicators. Correlations between breeding values of the number of quarters infected with minor pathogens and the number infected with major pathogens were antagonistic and statistically significant.

Animals↗
PubMed1995

Two retroviral infections of periparturient Holstein cattle: a phenotypic and genetic study.

Environmental and genetic factors affecting prevalences of antibodies to bovine leukosis virus and bovine immunodeficiency-like virus were studied on 137 periparturient Holstein cows selected for milk production. Environmental effects were obtained by logistic regression, and genetic parameters were determined using threshold animal models. Cows selected for high predicted transmitting ability for kilograms of milk fat plus protein had the highest prevalence of antibodies to bovine immunodeficiency-like virus and the lowest prevalence of antibodies to bovine leukosis virus. Heritability estimates for susceptibility to retroviral infections were close to zero.

Animals↗
PubMed1994

Comparison of Holsteins selected for high and average milk production. 1. Net income and production response to selection for milk.

The objective of the experiment was to quantify differences between two divergent lines of Holsteins for net income per day, per lactation, and per life-time using a linear profit function. Data consisted of 2768 lactation records from 1078 Holstein cows by 140 sires. Bulls with high PD milk were mated to daughters of sires with high PD for milk, and bulls with average PD for milk were mated to cows of average genetic merit, creating two divergent genetic lines of cattle. Data on production, health, and reproduction were collected. Analyses were based on lactation and lifetime. High line cows had greater net returns than average line cows by $.30/d (16.0%) per lactation and $.33 (19%) advantage/d of life. The high line cows were $103.79 more profitable (20.4%) per lactation and $375.60 (17.4%) more profitable during their lifetime than their average line herdmates. This income superiority was because high line cows averaged 940 kg more milk per lactation (16.4%) and 3435 kg more milk per lifetime (15.7%) than the average line cows. High line cows were superior by 500 kg for PTA for milk from January 1990. Selecting sires with high PD for milk effectively improved milk production and increased net income.

Animals↗
PubMed1994

Immunological parameters of periparturient Holstein cattle: genetic variation.

The genetic variability of blood neutrophil functions, lymphocyte blastogenic responses to mitogens, serum Ig concentrations, and serum complement and conglutinin activities was investigated from 35 d prepartum to 35 d postpartum for 137 Holstein cows. Periparturient cows experience an immunosuppression of various immunologic parameters at calving. Heritability estimates were obtained before, during, and after the episodes of immunosuppression. Significant genetic variability occurred in the periparturient changes for total number of neutrophils, neutrophil chemokinesis, assays of the neutrophil respiratory burst associated with phagocytosis (cytochrome c reduction, chemiluminescence, and iodination), serum concentrations of IgG1, IgG2, and IgM, and serum homolytic complement activity. This variability implies that immune profiles could be used for the selection of cattle with improved innate immune response without adverse effects on milk productivity. These results should be considered tentative, however, because the number of observations included in the data were limited.

Animals↗
PubMed1994

The selection index--then, now, and for the future.

When improvement is desired for several traits that may differ in variability, heritability, economic importance, and in the correlation among their phenotypes and genotypes, simultaneous multiple-trait index selection was more effective than independent culling levels or sequential selection. Such comparisons required definition of aggregate breeding value determined jointly by breeding values and economic importance of the component traits. The economic weight should approximate the partial regression of cost per unit of enterprise output value on breeding value for each trait. These can vary with production and marketing system, with performance of traits, and with breed role (i.e., paternal, maternal, or general) in crossbreeding systems. Genetic gains desired to maintain competitive ranking also may define the relative importance of traits. Because information available to estimate breeding values varies among the ages and categories of individuals under selection and because means are unknown, regressed (BLUP) predictions of trait breeding values are useful. They allow appropriate economic weights to be applied as the last step for predicting aggregate breeding values for individuals of different age classes, and they simplify choosing the proportions of selected breeders from each age class that maximize rate of change in aggregate breeding values. Inappropriate economic weights or errors in the parameters used to predict trait breeding values overestimate realized response in true aggregate breeding value.

Animal Husbandry↗
PubMed1994

Comparison of Holsteins selected for high and average milk production. 2. Health and reproductive response to selection for milk.

The objective of the experiment was to evaluate direct and correlated responses of secondary (fitness) traits to selection for milk yield. Data consisted of 2768 lactation records from 1078 Holstein cows by 140 sires. Bulls with high PD for milk were mated to daughters of sires with high PD for milk, and bulls with average PD for milk were mated to cows of average genetic merit, creating two genetic lines of cattle. Production, health, and reproductive data were collected. Major health categories were mammary, reproductive, respiratory, digestive, and skin and skeletal disorders. Analyses were per lactation and per lifetime. High PD line cattle averaged 940 kg more milk per lactation than the average line and differed by 500 kg for PTA milk during January 1990. By lactations, the high line cattle averaged 3.8% higher total health costs and 11.2% higher mammary costs than their average herd mates. For most health categories, high line cattle tended to incur higher cost than did average cattle. Selection of sires for high PD milk resulted in daughters that had slightly higher health costs, but total net return was still higher for daughters of high PD bulls.

Animals↗
PubMed1994

Differences in major histocompatibility complex frequencies after multitrait, divergent selection for immunocompetence.

White Leghorn chickens from lines selected for four immune-response traits (IR lines) were serotyped for B system alloantigens characterizing the haplotypes and genotypes to examine the effect of divergent selection for multitrait immunocompetence on MHC haplotype and genotype frequencies. The selected lines were derived from the Ottawa Strain 7. The selection index included four immunocompetence traits: antibody production against Mycoplasma gallisepticum (MG) and Pasteurella multocida, inflammatory response to phytohemagglutinin, and reticuloendothelial carbon clearance. The four lines include two replicates of high and low multitrait-immunocompetence lines. After four cycles of selection, significant differences (P < .05) in several B system haplotype frequencies were observed, both among IR lines and between the IR lines and the Ottawa Strain 7. The B2 haplotype frequency was greater in all IR lines than in the Ottawa Strain 7. The B21 frequency was less in both high lines than in the Ottawa Strain 7. In comparisons among lines, frequencies of B21 were greater in both replicates of the low lines and the B12 and B19 frequencies were significantly greater (P < .05) in the high lines. A gene substitution model showed effects (P < .10) of specific haplotypes on MG and on the index. The B2 haplotype had a positive effect associated with MG. Haplotype B21 was positively associated with the multitrait index. Haplotype B13 had a negative effect on both MG and the index. Significant differences (P < .01) in genotype frequencies were also noted among the IR lines. Associations between specific MHC haplotypes or genotypes and immune-response traits may offer insight into MHC-mediated mechanisms of disease resistance.

ABO Blood-Group System↗
PubMed1994

Direct and correlated responses to multitrait, divergent selection for immunocompetence.

Leghorn lines had been selected for an immunocompetence index based on four traits: antibody production to Mycoplasma gallisepticum (MG) and Pasteurella multocida (PM) vaccines, reticuloendothelial clearance of colloidal carbon (CCA), and cell-mediated, wing web response to phytohemagglutinin (PHA). The purpose of this study was to produce replicated lines of chickens with divergent levels of multitrait immunocompetence by index selection. The objectives of analyses of Generations 5 to 7 of this study was to characterize these lines with respect to immune-response traits, correlations among these traits, and correlated responses in other important production traits. Differences (P < .05) existed between the lines selected for high or low immune response and between the two replicates in mean breeding values and in individual immune-response traits. Averages of heritability estimates, weighted by number of offspring and pooled across three generations (two cycles of selection), estimated by using sire variance components and parent-offspring correlations were, respectively, .16 and .09 for the index, .31 and .08 for MG, .21 and -.02 for PM, .06 and .05 for CCA, and .08 and .12 for PHA. Realized heritabilities (response divided by effective selection differential) pooled across the two selection cycles, were .19 and .11 for the index, .06 and -.01 for MG, .44 and .32 for PM, 1.52 and -1.21 for CCA, and .48 and .15 for PHA, for Replicates 1 and 2, respectively. Phenotypic correlations among traits were generally small, and several estimates were negative. Estimates of genetic correlation varied widely. Juvenile and adult body weights, age of first egg, 32-wk egg weight, and rate of egg production were analyzed to evaluate effects of selection on these traits of direct economic importance. Very few differences were noted.

Age Factors↗
PubMed1993

Challenges to dairy cattle management: genetic considerations.

Several new technologies will be used to produce continued genetic change in dairy cattle. These technologies are categorized broadly as 1) improved modeling, selection, and evaluation methods; 2) use of new and improved reproductive technologies; 3) new developments in molecular genetics; and 4) new developments in immunogenetics. Improvements in evaluation will continue as computers become faster and have more storage capabilities. Improved mathematical models that more nearly describe the biology of lactation will maximize estimation of genetic differences and reduce residuals. New reproductive technology could allow reduction of generation intervals two- to fivefold compared with present generation intervals and, combined with genetic markers, could markedly accelerate progress. Health problems in dairy cattle are expected to increase as production increases. Thus, selection for decreased incidences of health disorders will be needed, probably by selection of sires with improved general immunocompetence. Research is in the early stages of application of techniques of molecular genetics to animal breeding. Early uses will allow detection and alleviation of genetic defects. Eventually, marker genes that directly affect production and metabolic pathways that also affect production will be subjected to selection. The ability to foresee new and potentially useful techniques will be determined by scientific advancement of areas in which researchers are engaged; thus, accurate prediction far into the future cannot be expected.

Animals↗
PubMed1992

Genetic and phenotypic parameters for type and production in Guernsey dairy cows.

Heritabilities; genetic and phenotypic correlations for milk, fat, and protein production; and linear type traits were estimated from a sire model including sire relationships using multiple-trait REML. For the milk production traits, 68,109 first parity records were analyzed. Heritabilities ranged from .31 to .37, genetic correlations between the milk production traits ranged from .80 to .92, and phenotypic correlations ranged from .86 to .94. Linear type traits from 12,996 cows on 15 traits were used to estimate heritabilities and genetic and phenotypic correlations between linear type traits. The heritabilities ranged from .53 for stature to .09 for foot angle. Rear udder height and rear udder width had the highest positive genetic correlation (.85), whereas dairy form and udder depth had the highest negative genetic correlation (-.41). When the first parity production records were merged with type records for cows, 9867 records on 18 traits were obtained. Dairy form, rear udder height, and rear udder width had strong to moderate positive genetic correlations with the three production traits. Fore udder attachment and udder depth had moderate negative genetic correlations with the three milk production traits. These results suggest that selection for improvement of milk production will lead to correlated increases in dairy form, rear udder height, rear udder width, and udder depth and to correlated decreases in the strength of fore udder attachment.

Animals↗
PubMed1992

The importance of maternal lineage on milk yield traits of dairy cattle.

Maternal lineage effects on milk yield traits, considered indicative of cytoplasmic inheritance, were evaluated with animal models. Cattle were from a selection experiment begun in 1968. Maternal pedigrees were traced to the first female member in the Holstein-Friesian Herdbook; purchased cows entering the herd, considered foundation females, were assigned to maternal lineage groups. All models accounted for year-season of calving, parity, and selection lines. Maternal lineage effects were included in a repeated records model with cow effects and preadjustment for sire and maternal grandsire transmitting abilities. Maternal lineage accounted for 5.2, 4.1, and 10.5% of phenotypic variation of preadjusted records of milk yield, fat yield, and fat percentage, respectively. Maternal lineage was evaluated as a fixed effect in an animal model including random animal and permanent environmental effects. Maternal lineage significantly affected fat percentage but not milk yield. Maternal genetic (nuclear) effects and their covariance with additive animal effects did not significantly account for additional variation nor did they influence maternal lineage estimates. Maternal lineage affected calculated net energy of milk but was not important for SNF yield or concentration. Maternal lineage influenced fat percentage, energy concentration, and, to a lesser extent, fat yield in milk of dairy cattle.

Animals↗
PubMed1992

Genetic parameters for yield traits of Holsteins, including lactose and somatic cell score.

First lactation milk, fat, protein, and lactose yields and percentage yields were analyzed using a multiple-trait sire model including herd-year-season, sire group, and age of cow as fixed effects. Somatic cell score was fit both as a fixed effect in the model and as an additional dependent variable in two analyses with almost identical results. Variance components were estimated using REML with an expectation-maximization algorithm including sire relationships. Lactose means ranged from 4.84 to 4.97% across three dairy breeds. Data used to estimate variance components were first lactation Holstein records collected from 1986 to 1988 from 5246 daughters of 392 AI sires. Heritability estimates were .30, .29, .27, and .26 for milk, fat, protein, and lactose yields; .45, .47, and .53 for fat, protein, and lactose percentage yields; and .16 for somatic cell score. Genetic correlations of lactose percentage with milk, fat, protein, fat and protein percentages, and somatic cell score were -.30, -.16, -.21, .10, .29, and -.11, respectively, and phenotypic correlations were -.08, -.02, .01, .11, .29, and -.15.

Animals↗
PubMed1992

Relationship of in vitro immune function with health and production in Holstein cattle.

Eighty-seven lactating Holstein cows from the Iowa State University Breeding Research Herd were evaluated for 20 in vitro measures of immune function. Principal component analysis was used to discard redundant assay variables such that the 11 remaining variables were more nearly independent than the original variables. Multiple linear regression in an animal model was used to determine the effects of these 11 variables on lifetime production and on general, under, and reproductive health traits. A significant joint effect of the 11 immune function variables on California mastitis test scores was observed. California mastitis test scores were positively correlated with antibody-dependent neutrophil cytotoxicity and negatively correlated with antibody-independent neutrophil cytotoxicity. Wisconsin mastitis test scores were also positively associated with antibody-dependent neutrophil cytotoxicity. Cytochrome c reduction was negatively associated with mammary and total health costs. A positive relationship between clinical mastitis and discarded milk and IgG2 was observed, and IgG1 was associated with increased quarter California mastitis test scores and increased production. Thus, certain in vitro immune function assays may serve as indicators of susceptibility to health problems in dairy cattle, particularly for traits associated with udder health.

Agglutination Tests↗