Mice with early onset of death (EOD) due to lupus glomerulonephritis.
(9/4007)
Both MRL-lpr/lpr (lpr) and BXSB mice fall victim to autoimmune disease as a function of age. To combine their properties, brother-sister mating of (female lpr x male BXSB)F1 mice was done. Mice for mating were selected according to indicators of early onset of glomerulonephritis and subsequent early death (i.e., EOD). This mating was continued for more than 16 generations. The EOD mice thus established had homozygous H-2k/k, lpr/lpr, and possible yaa/- (in the case of males). The average life span of males was 83 days while that of females was 126 days. After 12 weeks of age, the majority (> 80%) of male EOD mice were characterized by the abnormality of urine due to glomerulonephritis. We then characterized how glomerulonephritis was evoked, especially in terms of expanding lymphocyte subsets in various immune organs. Similar to the case of parental lpr mice, the major expanding cells were CD4-8-B220+ TCRint cells in the immune organs and kidney. In addition, myeloid cells were found to infiltrate the kidney. This massive infiltration of both TCRint cells and myeloid cells might be responsible for the onset of acute glomerulonephritis. Even after more than 50 generations, these EOD mice still carry both lpr and yaa genes. These results suggest that EOD mice might be a very useful tool for the study of acute lupus glomerulonephritis which is evoked by the genetic abnormalities. (+info)
Effect of breed (Angus vs Simmental) on immune function and response to a disease challenge in stressed steers and preweaned calves.
(10/4007)
Two experiments were conducted with feeder steer calves and preweaned calves to determine the effects of breed on immune response. In Exp. 1, newly weaned Angus (n = 24) and Simmental (n = 24) steer calves were blocked by weight within breed and randomly assigned to 12 pens with four calves per pen. The basal diet consisted of 87% corn silage (DM basis) and 13% of a soybean meal-mineral-vitamin supplement. Steers were allowed ad libitum access to feed throughout the study. On d 2 following weaning, calves received an intranasal inoculation of infectious bovine rhinotraecheitis virus (IBRV; 2.7 x 10(8) CCID50). Rectal temperatures in response to the IBRV were higher (P < .05) in Angus calves. On d 9, calves were injected i.m. with 10 mL of a 25% pig red blood cell (PRBC) suspension. Total immunoglobulin (Ig) and IgM titers against PRBC were higher (P < .05) for the Angus calves. Breed did affect cell-mediated immune response to phytohemagglutinin (PHA). In Exp. 2, preweaned (16 Angus and 16 Simmental) calves were selected based on breed, body weight, and sex. On 0 d, all selected calves were injected i.m. with 10 mL of a 25% PRBC suspension. Total Ig and IgG titers against PRBC were higher (P < .05) for Angus calves. On d 28, lymphocytes were isolated from peripheral blood obtained from eight calves per breed. Peripheral lymphocytes from the Angus calves had a greater (P < .07) blastogenic response to 6.25 microg/mL of PHA than lymphocytes from Simmental calves. Results indicate that the immune response of Angus and Simmental calves may differ. (+info)
"Quasi-REML" correlation estimates between production and health traits in the presence of selection and confounding: a simulation study.
(11/4007)
Performance of the "quasi-REML" method for estimating correlations between a continuous trait and a categorical trait, and between two categorical traits, was studied with Monte Carlo simulations. Three continuous, correlated traits were simulated for identical populations and three scenarios with either no selection, selection for one moderately heritable trait (Trait 1, h2 = .25), and selection for the same trait plus confounding between sires and management groups. The "true" environmental correlations between Traits 2 (h2 = .10) and 3 (h2 = .05) were always of the same absolute size (.20), but further data scenarios were generated by setting the sign of environmental correlation to either positive or negative. Observations for Traits 2 and 3 were then reassigned to binomial categories to simulate health or reproductive traits with incidences of 15 and 5%, respectively. Genetic correlations (r(g12), r(g13), and r(g23) and environmental correlations (r(e12), r(e13), and r(e23)) were estimated for the underlying continuous scale (REML) and the visible categorical scales ("quasi-REML") with linear multiple-trait sire and animal models. Contrary to theory, practically all "quasi-REML" genetic correlations were underestimated to some extent with the sire and animal models. Selection inflated this negative bias for sire model estimates, and the sign of r(e23) noticeably affected r(g23) estimates for the animal model, with greater bias and SD for estimates when the "true" r(e23) was positive. Transformed "quasi-REML" environmental correlations between a continuous and a categorical trait were estimated with good efficiency and little bias, and corresponding correlations between two categorical traits were systematically overestimated. Confounding between sires and contemporary groups negatively affected all correlation estimates on the underlying and the visible scales, especially for sire model "quasi-REML" estimates of genetic correlation. Selection, data structure, and the (co)variance structure influences how well correlations involving categorical traits are estimated with "quasi-REML" methods. (+info)
Properties of threshold model predictions.
(12/4007)
Estimation of genetic parameters and accuracy of threshold model genetic predictions were investigated. Data were simulated for different population structures by using Monte Carlo techniques. Variance components were estimated by using threshold models and linear sire models applied to untransformed data, logarithmically transformed data, and transformation to Snell scores. Effects of number of categories (2, 5, and 10), incidence of categories (extreme, moderate, and normal), heritability in the underlying scale (.04, .20, and .50), and data structure (unbalanced and balanced) on accuracy of genetic prediction were investigated. The real importance of using a threshold model was to estimate genetic parameters. An expected heritability of .20 was estimated to be .22 and .10 by a threshold model and a linear model, respectively. Accuracy increased significantly with a larger number of categories, a more normal distribution of incidences, increased heritability, and more balanced data. Even threshold models were shown to be more efficient with more than two categories (e.g., binomial). Transformation of scale did not accomplish the purpose intended. (+info)
Relative development of subcutaneous, intermuscular, and kidney fat in growing pigs with different body compositions.
(13/4007)
A total of 94 pigs from seven groups considered as lean (boars from a synthetic line and the Pietrain breed), conventional (boars, gilts, and barrows from the Large White breed), fat (barrows from the Meishan x Large White cross), or obese (Meishan barrows) were serially slaughtered between 12 and 110 kg BW. Carcasses were dissected into muscle, bone, skin, and fat, which was further separated into subcutaneous, intermuscular, and kidney fats. Subcutaneous fat accounted for 60 to 70% of body fat and intermuscular fat for 20 to 35% of body fat. Relative to total fat, intermuscular fat grew more slowly (allometric growth coefficients generally < 1), subcutaneous fat at the same rate (b close to 1), and kidney fat more rapidly (1.12 < b < 1.33). The leaner the animals genetically, the higher the proportion of intermuscular fat in total fat. The ratio of intermuscular to subcutaneous fat varied from .31 in Meishan barrows to .66 in Pietrain boars. Overall, the ratio of intermuscular fat to muscle weight or body weight was positively related to the development of total fat. However, Pietrain pigs were unique in having a high development of intermuscular fat. The present results suggest that 1) the genetic controls of the development of intermuscular and subcutaneous fat are partially independent and 2) the development of intermuscular fat may be determined at an early stage, before 20 kg BW. (+info)
Long-term trend toward earlier breeding in an American bird: a response to global warming?
(14/4007)
In regions with severe winters, global warming may be expected to cause earlier onset of breeding in most animals, yet no documentation of such a trend exists in North America. In a study of marked individuals of the Mexican jay (Aphelocoma ultramarina) in southeastern Arizona, from 1971 to 1998, the mean Julian date of first clutch in the population declined significantly by 10.1 days. The date of the first nest in the population also became earlier, by 10.8 days. These changes were associated with significant trends toward increased monthly minimum temperatures on the study area, traits that are associated with the onset of breeding in this population. Significant trends from 1971 to 1997 toward warmer minimum temperatures in the months before and during the initiation of breeding were observed. These trends parallel changes in minimum temperatures and community composition in a recent study of grassland ecology in the western United States. Together, they suggest that more attention should be given to the possible ecological importance of global change in minimum temperatures. (+info)
Reproductive performance of bulls divergently selected on the basis of blood serum insulin-like growth factor I concentration.
(15/4007)
The objectives of this study were to examine differences in scrotal circumference, sperm motility, and percentage of normal sperm cells between two lines of Angus beef cattle divergently selected for blood serum IGF-I concentration. Data were obtained from an ongoing experiment involving 100 spring-calving (50 high and 50 low line) and 100 fall-calving (50 high and 50 low line) purebred Angus cows. Scrotal circumference, percentage of motile sperm cells, and percentage of normal sperm cells did not differ between high and low IGF-I line yearling bulls (P = .79, .50, and .56, respectively). The IGF-I concentrations measured at d 28, 42, and 56 of the postweaning test are abbreviated as IGF28, IGF42, and IGF56, respectively. Coefficients for the quadratic regression of scrotal circumference on IGF28 and IGF42 tended to be negative (P = .07 and .08, respectively), as did the coefficient for the quadratic regression of the percentage of motile sperm cells on IGF42 (P = .08). The coefficient for the linear regression of percentage of normal sperm cells on IGF28 was positive (P = .02). The coefficient for the quadratic regression of percentage of normal sperm cells on IGF56 was negative (P = .04). Coefficients for the quadratic regression of scrotal circumference and percentage of normal sperm cells on mean IGF-I concentrations were negative and important (P = .04 and .08, respectively). Thus, scrotal circumference and percentage of normal sperm cells are related to blood serum IGF-I concentration in yearling Angus bulls. (+info)
Effect of genetic variants of the heart fatty acid-binding protein gene on intramuscular fat and performance traits in pigs.
(16/4007)
In order to find genetic markers to improve the meat quality of pigs by breeding we studied the relationship between variation in the heart fatty acid-binding protein (H-FABP) gene (FABP3) and intramuscular fat (IMF) content. To estimate the effect of H-FABP, pigs from two Duroc populations were selectively mated in such a way that at least two genotypes were present in each litter. In total, data from 983 pigs and pedigree information from three preceding generations were analyzed. Offspring were tested for IMF content as well as backfat thickness (BFT), BW, and drip loss of the meat (DRIP). All pigs were assigned to H-FABP RFLP genotype classes either by the assessed genotype (75%) or based on a probability score determined according to genotypic information of their relatives (25%). Contrasts were detected between homozygous H-FABP RFLP genotype classes for IMF content (.4%, P < .05), BFT (.6 mm, P < .01), and BW (2.4 kg, P < .10). No significant contrasts were detected for DRIP. Results for IMF content, BFT, and BW were confirmed when only genotyped animals were analyzed. Variation in BFT partially explained the effect on IMF content. Although other closely linked genes on porcine chromosome 6 might be responsible for the observed effect, interference of the halothane gene was excluded because all parental animals were noncarriers. In conclusion, H-FABP RFLP can be used as markers to select for increased IMF content and growth in breeding programs. (+info)