Biomedical subjects

V A Garwood

Publications and source records attributed to V A Garwood.

At least 19 recordsLinked to original sources

PubMed1993

Association of dominant marker traits and metric traits in chickens.

This study was initiated to determine whether an allelic substitution of a dominant marker gene would identify a region close to a locus affecting expression in a metric trait. The rationale for the experiment was to utilize disequilibrium between a multiple recessive randombred Rhode Island Red (RRc) stock previously selected for quantitative trait performance and an unimproved dominant marker stock (MDM). The reporter genes in the MDM were: barring (B), silver (S), creeper (Cp), rose comb (R), double uropygial gland (U), crest (Cr), dominant white (I), frizzle (F), duplex comb (D), multiple spurs (M), polydactyly (Po), blue egg (O), pea comb (P), naked neck (Na), extended black (E), white skin (W+), muffs and beard (Mb), and feathered shanks (Fsh). Appropriate reciprocal crosses of MDM with RRc and F1 to RRc produced segregating full sibs that were evaluated for association with reporter traits. Carriers of Cr, I, and F were significantly later in sexual maturity than their recessive full sibs. The pleiotropic effects of F are believed to account for the later maturity. None of the marker traits had a significant association with egg numbers or egg weight. Birds expressing E were distinctly heavier at 8 and 32 wk. There is no obvious explanation for the significant larger size for the E phenotype. The CR-I-F phenotypes were significantly smaller at 32 wk than noncarrier full sibs.

Alleles↗

PubMed1989

Growth response to chronic beta agonist feeding and mature carcass characteristics of quail (Coturnix coturnix japonica) selected for high and low body densities.

A study was conducted to determine the effect of long-term feeding of a beta agonist (cimaterol) on female Japanese quail. Quail used were from lines selected for high (HD) and low (LD) body density from a randombred population. Dietary treatments consisted of 1) the basal feed, 2) the basal feed containing .5 ppm, or 3) 1.0 ppm of the beta agonist. The treatment period for the six experimental groups extended from 14 to 94 days of age. Weight gains to 49 days and live weights at 94 days of age were greater (P less than .05) in the cimaterol-fed groups. Age and live weight at first egg in both lines were greater (P less than .01) when groups were fed treated diets. Eviscerated carcass yields were higher (P less than .01) and carcass moisture was lower (P less than .05) in treated groups. There were no differences in carcass fat or protein among the dietary treatments. Abdominal fat pad weights were larger (P less than .05) in the heavier (P less than .01) HD line but were not significantly affected by cimaterol. Abdominal adipocyte diameters were significantly larger in HD (P less than .05) and cimaterol-treated (P less than .05) quail.

Abdomen↗

PubMed1987

Response of growth-selected Japanese quail lines to tannin levels in grain sorghum diets with suboptimal protein.

Growth of selected lines of Japanese quail fed grain sorghum diets was evaluated. Suboptimal protein levels (23 and 25%) were used in conjunction with two varieties of sorghum differing in tannin content (.02 vs. 6.06%). Chicks of three related lines of quail differing in growth rates and mature body sizes were fed the diets from 0 to 28 days of age. Growth was significantly reduced (14 and 6%) by substitution of high tannin sorghum for low tannin sorghum in the 23 and 25% protein diets, respectively. No line X diet interaction was observed.

Animal Feed↗

PubMed1987

Body volume and density of live Coturnix quail and associated genetic relationships.

A device was developed for the nondestructive measure of body volume by air displacement. Two experiments were performed on Coturnix quail to determine the feasibility of using body density and volume of the live bird as criteria of selection for changing whole body lipid content. In Experiment 1,423 birds were used from three selected lines differing in adult weight. Three measurements of volume were taken on each bird. Repeatability of volume was consistently high for all line-sex subclasses, averaging .75. A phenotypic correlation of .55 was derived for body density and lipid content of the whole carcass. Estimates of heritabilities and genetic relationships for body density, volume and weight, and whole body lipid content were derived in Experiment 2 on 739 birds representing 50 sires and 125 dams of a randombred population. Heritability of volume averaged over full and half-sibs and over sexes was high (.66). The average genetic correlation for volume and lipid content was .44. Heritabilities of density averaged .38 and were highly genetically correlated (.69) with lipid content, which had an average heritability of .35. Body weight was very highly heritable in the population (.82) and correlated genetically with body lipid (.60).

Adipose Tissue↗

PubMed1987

Estimates of heritability for plasma very low density lipoprotein concentration and genetic correlations with lipid content, body volume, and density in Coturnix coturnix japonica.

Genetic parameters associated with very low density lipoprotein concentration (VLDL) in a randombred population of Coturnix were estimated. Associated traits were: body density, volume, and weight of the live bird, and lipid content of the whole carcass. A total of 739 progeny by 50 sires and 126 dams was the basis of the data. The VLDL was highly heritable (.52) and highly correlated with lipid content (greater than .50) but correlated to lesser degrees with body density (.24) and body volume (.20). The genetic correlation estimates between VLDL and body weight were small relative to their standard errors.

Adipose Tissue↗

PubMed1985

Genetic parameters and cellularity of adiposity in layer-type chickens.

Genetic parameters concerning weight of abdominal fat pads were determined for a randombred layer-type population. Progeny by the upper (U) and lower (L) 10% of the sires with respect to weights of fat pads were compared. Cellularity measures were made of the fat pads from random samples of the two groups of progeny. Progeny of U sires had fat pads numerically heavier than those of progeny by all sires. However, progeny of L sires had fat pad weights similar to those of all sires. Heritability estimates of abdominal fat pad weight, as calculated from half-sib correlation and regression of offspring on sires, were .29 +/- .36 and .27 +/- .06, respectively. Genetic estimates indicated fat pad weight to be highly correlated with growth but essentially uncorrelated with egg production. Progeny of the L and U sires had the same number of adipocytes, but progeny by U sires had larger adipocytes than progeny by L sires.

Abdomen↗

PubMed1984

Influence of sex-linked feathering phenotypes of parents and progeny upon lymphoid leukosis virus infection status and egg production.

Data were collected on egg production, livability, lymphoid leukosis virus and antibody incidence, and hemagglutinin response to sheep red blood cells for slow- and fast-feathering female progeny from slow- and fast-feathering dams with known lymphoid leukosis virus infection status. Analyses of these results indicate that when the offspring or the dams are of the slow-feathering type, the offspring experience an increased rate of horizontal infection. This infection seemingly leads to an immunologically tolerant condition with an inability to produce specific lymphoid leukosis virus antibodies, thereby allowing the viremia to persist. This immunologically tolerant condition, which also occurs in the progeny of virus positive dams due to congenital transmission, is associated with depressed egg production performance. However, a hypothesized lack of immunological competence was not found in the hemagglutinin response to sheep red blood cells late in life. Our results suggest that fast-feathering progeny of slow-feathering dams may also be adversely influenced by increased congenital infection from their dams.

Animals↗

PubMed1983

The effects of geographical area, rearing method, caging density, and lymphoid leukosis infection on adult performance in egg stocks of chickens.

Birds were brooded reared, and laying house-tested at two widely separated sites: Animal Research Centre (ARC) and North Central Region Poultry Breeding Laboratory (NCRPBL). Two strain and a commercial stock were included only at NCRPBL. At ARC, all birds were brooded, reared, and laying house-tested in cages. At NCRPBL, half of the chicks were brooded and reared on floor and half in cages, and all hens were laying tested at one or two birds per cage. Most hens housed one per cage were tested for lymphoid leukosis virus (LLV) infection by the complement fixation test for group specific antigen in egg albumen. When all hens tested at NCRPBL were considered, the method of brooding and rearing affected only egg weight and body weight in favor of the hens reared in floor pens. The commercial stock and the strain crosses performed better than the control strains. Despite very similar genetic backgrounds, there were large differences between control strains 10 and NCR. Hens housed one per cage had lower mortality and higher egg production than those housed two per cage. Average performance of birds at ARC was somewhat better than that at NCRPBL, but there were genotype-site interactions for mortality, egg production, and sexual maturity. The frequency of shedders in the crosses (17.2%) was the same as that of the control strains (20.8%), but the frequency of shedders in the commercial stock (4.5%) was much lower. The method of brooding and rearing had no effect on the frequency of shedders. The LLV infection was associated with significant reductions in egg production and egg quality. For example, the difference between test-positive and test-negative hens was 25 eggs per hen housed and 16 eggs per surviving hen.

Animal Husbandry↗

PubMed1982

Effects of temporary feed deprivation on performance of yearling hens.

Four treatment groups each of 200 hens 72 weeks old were randomly selected from a randombred white Leghorn population. Treatment groups were deprived of feed for 0 (control), 2, 4, and 6 days during the 1st week of the 25-week experiment. Hens in Treatments 2, 4, and 6 had an immediate temporary decline in egg production, but their normal rate of lay was resumed after week 5 of the experiment. Losses in egg production during fasting and recovery were compensated for by higher rates of lay during the last 15 weeks of the experiment. Body and egg weights and mortality were unaffected by treatments; however, egg specific gravity was adversely affected at week 10 in treatments where egg production continued during feed deprivation.

Animals↗

PubMed1981

Some genetic parameters involving poststress performance traits in chickens.

Genetic parameters of several economic traits associated with an 18 week period of poststress egg production were estimated in a randombred population of 1800 White Leghorn hens. Genetic correlations among 6 of 11 traits associated with poststress egg production were different (P less than .05) between the control and stress groups. Earlier maturing birds recovered from stress sooner than later maturing birds and had higher egg production. Early egg production (20 to 40 weeks of age) was a better indicator of poststress egg production (55 to 73 weeks of age) in the stress group than in the control group. Rate of lay from the 9th to the 18th week after stress was higher in the stress group, but overall poststress rate of lay was higher in the control group.

Animals↗

PubMed1981

Association of lymphoid leukosis virus and performance in a randombred layer population.

The association of subclinical infections with lymphoid leukosis virus and performance was investigated in a randombred White Leghorn type population. The proportion of birds shedding group specific (gs) antigen into their egg albumen was high (23.8%). Birds with gs antigen in their albumen matured later, produced fewer and smaller eggs, and grew less rapidly tha their nonshedding counterparts.

Animals↗

PubMed1980

Selection of layers for rapid recovery from stress.

A one-generation experiment was conducted to evaluate response to selection of layers for rapid recovery from stress and to estimate genetic parameters associated with the selected trait. Stress was induced at 55 weeks of age and maintained for 8 days on 1450 laying hens of a randombred White Leghorn population. Egg production persisted an average of 3.5 days after onset of stress and had ceased in all birds by 8 days. Average recovery time, from cessation of lay to first poststress egg, was 27.1 days, and heritability estimated from the sire component of variance was .30 for the selected trait. Hens with higher rates of lay resumed production sooner after stress and tended to continue production longer duration stress. Selection of 11% of layers in generation 0 with shortest recovery time in each of 11 replicates resulted in a significant (P < .05) reduction of 4.1 days in recovery time in generation 1.

Animals↗

PubMed1976

Sex difference in mortality rates of Leghorn-Red reciprocal crosses.

Mortality rates among White Leghorn-Rhode Island Red pure-line and reciprocal cross adult female progeny were recorded for 8 years. The mortality rate among progeny of White Leghorn males exceeded that of the progeny of Rhode Island Red males in both pure-line and crossbreds. White Leghorn X Rhode Island Red crossbred progeny had the highest mortality rate. In a second phase of the study, a comparison was made between mortality rates of male and female progeny of White Leghorn-Rhode Island Red reciprocal crosses. Rate of loss was significantly lower in males than in females but did not differ between crosses. These results support a conclusion that sex linkage is a major factor in differential mortality rates between progeny of White Longhorn-heavy breed reciprocal crosses.

Animals↗

PubMed1974