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Biomedical subjects

C Hagger

Publications and source records attributed to C Hagger.

27 records · Page 2Linked to original sources
PubMed1992

Inbreeding in Swiss Braunvieh and its influence on breeding values predicted from a repeatability animal model.

Inbreeding coefficients were computed for 910,444 animals of the Swiss Braunvieh population. Of the animals born in 1984, 71.5% were inbred with 67.9, 3.4, and .2% having inbreeding coefficients between greater than 0 and 5%, greater than 5 to 10%, and greater than 10%, respectively. The average inbreeding coefficient was 1.14% but, for animals with both parents and at least one grandparent known, it was 1.67%. Breeding values for total milk, fat, and protein yields and for fat and protein percentages were predicted using a repeatability animal model including a regression on the inbreeding coefficient. Phenotypic performance was sizeably depressed for milk yield only (-26 kg/% of inbreeding or 2.4% of the phenotypic standard deviation). Adjusting for inbreeding increased the estimated genetic trend slightly. Inbreeding is only partially accounted for when it is ignored in the construction of the inverse of the numerator relationship matrix. This effect was investigated by comparing predicted breeding values from a model including the complete matrix with predicted breeding values from a model including a matrix constructed with inbreeding ignored. Only .8% of all predicted breeding values were affected by more than +/- 5.5 kg. The maximum difference observed was 55.3 kg. The observed average absolute differences between the breeding values of offspring predicted with the two models increased with inbreeding of parents.

Animals↗
PubMed1991

Visual habit formation in 3-month-old monkeys (Macaca mulatta): reversal of sex difference following neonatal manipulations of androgens.

The ability to perform on a concurrent visual discrimination task with 24-h intertrial intervals (24-h ITI task) develops a few weeks earlier in female than in male infant monkeys. To test whether this sex difference was related to the presence of perinatal androgens, plasma testosterone levels were reduced in male infant monkeys by neonatal orchiectomy and increased in neonatally ovariectomized female infant monkeys by treatment with either testosterone propionate (TP) or its reduced metabolite, dihydrotestosterone (DHT). At 3 months of age, the animals were tested on the 24-h ITI task and their performance compared with that of age-matched intact male and female monkeys. Orchiectomy which was followed by a slight but visible atrophy of the external genitalia, hastened performance of male infant monkeys to the level of intact infant females. Conversely, androgenization of ovariectomized female infant monkeys given DHT, which had only a slight virilizing effect on the external genitalia, showed the learning of these female infants to the rate of intact male infant monkeys. Curiously, although TP treatment in ovariectomized female infant monkeys was more effective than DHT in virilizing the external genitalia, it failed to slow the rate of learning. This dissociation between the effects of TP and DHT on external genital organs and learning abilities is discussed in terms of possible differences in dose-dependent, time-dependent, and receptor-binding mechanisms of the two androgens. The present study provides further evidence that early androgen secretions affect the organization not only of brain structures related to primary sexual characteristics but also of those related to learning abilities.

Androgens↗
PubMed1991

Sex differences in the development of learning abilities in primates.

The role of steroid gonadal hormones in promoting sex differences in reproductive behaviors has been thoroughly studied in numerous mammalian species. More recent experiments have indicated that the presence or absence of steroid hormones during the critical period of brain differentiation likewise might promote the development of sex differences in cognitive abilities. Studies in infant rhesus monkeys have demonstrated that there exist sex differences in learning abilities that can be altered by perinatal hormonal manipulations, suggesting that testosterone might be a crucial factor responsible for the development of sex differences in cognitive styles. In addition, neonatal lesion studies have shown that the cortical areas mediating specific learning abilities mature at different rates in male and female infant monkeys. These findings support the view that the perinatal hormonal environment can affect the rate of brain maturation by influencing neuronal connectivity at the cortical level. The combined data from sex differences in learning abilities in human infants and their reversibility in endocrinological syndromes suggest that testosterone may affect the maturation of the human brain in a manner similar to that demonstrated in nonhuman primates.

Animals↗
PubMed1991

Phenotypic and genetic effects on feed intake of laying hens in different years.

Feed intake from 21 to 40 wk and from 41 to 60 wk of age of brown egg layers was analyzed. The full model contained BW, egg mass (EM) output, BW change (BWCH), and age at first egg as covariates in addition to effects of plumage condition class, sire, and dam. A reduced model contained the covariates only. Between 905 and 1,161, and 880 and 1,119 hens were available in the first and second periods, respectively. Averaged over 6 yr the full model explained 84 and 77%, the reduced model 73 and 63%, respectively, of the variance in feed consumption in the two periods. Regression coefficients for BW showed only a small variation between years as well as between periods. Variation was larger for the coefficients of EM and of BWCH. Larger coefficients were observed in the first period for both traits. The sequence of entering the reduced equation in a stepwise procedure was always BW, EM output, then BWCH. Averaged over 6 yr, the relative contribution of BW by its own to the accuracy of the regression model, was 68 and 60% in the two periods. Egg mass output then added 25 and 39%, and BWCH 7 and 2% in the first and second periods, respectively. The predictive value of the covariates changed with increasing age of the hens. A high average heritability of .48 could be estimated for the residual feed intake in both periods. This suggested enhanced selection response for efficiency.

Animals↗
PubMed1990

Age and sex differences in the effects of selective temporal lobe lesion on the formation of visual discrimination habits in rhesus monkeys (Macaca mulatta).

Three-month-old infant monkeys with neonatal ablations of either cortical area TE or the amygdala and hippocampus and age-matched normal infants were trained in a concurrent object discrimination task with 24-hr intertrial intervals. Neonatal area TE lesions yielded a transient deficit in visual habit formation, present in the female monkeys only, whereas the same lesions in adult monkeys yielded a severe and long-lasting deficit in both males and females. Although pointing to a greater neural compensation for the early loss as compared with the later loss of cortical area TE, the results also corroborate a recent suggestion (Bachevalier, Hagger, & Bercu, 1989) that, at 3 months of age, area TE is more fully functional in females than in males. Neither early nor late amygdalohippocampal lesions impaired the ability to form visual discrimination habits, strengthening the proposal that the habit system uses a corticononlimbic circuit.

Aging↗
PubMed1989

Gender differences in visual habit formation in 3-month-old rhesus monkeys.

The rate of learning concurrent visual discriminations with 24-hr intertrial intervals, a measure of habit formation, was assessed in infant monkeys of both sexes and compared with the rate of learning in adults. In two separate series of animals, 3-month-old male monkeys learned an initial set of discriminations (but not later sets) more slowly than 3-month-old females. This gender difference was absent in 6-month-old monkeys and in adults, both of which learned the initial set at the same rate. Determination of plasma gonadal hormone levels at the time of testing revealed a significant correlation (rs = 0.95) between testosterone levels and learning scores on the initial set in the 3-month-old male monkeys (i.e., the higher the level the poorer the score). No such correlation was found in the 3-month-old female monkeys or in the 6-month-olds of either sex. These results suggest that high testosterone levels found perinatally in male monkeys temporarily slows maturation of the neural system underlying visual habit formation.

Animals↗
PubMed1988

Selection with restriction in a poultry breeding scheme with different selection procedures in both sexes: direct responses.

1. A selection experiment with two lines of White Leghorns originating from a common base population was carried out over 5 generations with the aims of maintaining an unchanged egg weight, reducing age at first egg and reducing adult body weight. Each line consisted of 14 male and 42 female breeders. 2. Males were mass selected for low body weight at 20 weeks of age. To compensate for the expected correlated loss in egg weight, hens were selected according to an index which counteracted this undesirable change while also reducing age at first egg and reducing body weight. 3. An index value was calculated for each individual hen from average egg weight, age at first egg and body weight at 20 weeks. Index weights had to be calculated for each generation and line in accordance with the expected change in egg weight due to male selection on body weight. 4. For control matings hens with an index near the population average were mated either to males with body weight near the population average (control C1) or to the selected males within lines (control C2). 5. Expected and observed total responses agreed well for all traits in line 1 and for body weight in line 2. 6. Phenotypic variances and covariances showed little change during the experiment. However, genetic variances and covariances estimated at the end of the experiment showed some differences, both between lines and compared to the parameters used for index construction.

Animals↗
PubMed1984

Relationships between the H and A-O blood types, phosphohexose isomerase and 6-phosphogluconate dehydrogenase red cell enzyme systems and halothane sensitivity, and economic traits in a superior and an inferior selection line of swiss landrace pigs.

Associations between production traits and the genes for halothane sensitivity (HAL), S, A and H blood group systems and phosphohexose isomerase (PHI) and 6-phosphogluconate dehydrogenase (6-PGD) enzyme systems were investigated in two lines of pigs selected for an index. The phenotypic variance-covariance matrix of the index included backfat thickness and daily gain, whereas the genetic variance-covariance matrix included daily gain, feed conversion and percentage of lean meat. The experiment was conducted at the experimental station of the Institute of Animal Production and has been underway since 1973. The same index was applied but in two opposite directions to give a superior and inferior line in relation to the production traits. One hundred twenty-nine animals of the superior line in the seventh generation and 88 animals of the inferior line in the sixth generation were studied. Forty-two percent (54/129) of the animals of the superior line were halothane-positive. No animals in the inferior line were halothane reactors. Of the halothane-positive pigs, 70.4% (38/54) in the superior line had the HaHa and 94.4% (51/54) had the SsSs genotype, whereas only 4% (3/75) of the HaHa and 12% (9/75) of the SsSs pigs were halothane-negative. By practicing selection at the H and S loci, it seems possible to efficiently reduce halothane sensitivity in Swiss Landrace pigs. In pigs of the superior line, there were significant differences in percentage of lean meat, carcass length, pH1 (pH value at 45 min to 1 h postmortem, M. longissimus) and reflectance values among genotypes of the HAL, S and H systems and among some genotypes of the 6-PGD system. Poorest meat quality, highest percentage of lean meat and shortest carcass length were observed in pigs homozygous for the alleles HALn, Ss, Ha, PHIB and 6-PGDA. In the inferior line, these associations were absent. As the HAL locus is associated with the above mentioned production traits, linkage disequilibria may explain the observed associations among the H, S, PHI and 6-PGD types and production traits.

Alleles↗