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At least 289 records · Page 16Linked to original sources
PubMed1997

Effects of sire, dam traits, calf traits, and environment on dystocia and subsequent reproduction of two-year-old heifers.

A study was conducted over 3 yr to evaluate effects of sire birth weight EPD, calf birth weight and shape, and heifer pelvic area and weight, individually and in combination, on dystocia and subsequent rebreeding of 2-yr-old heifers. Heifers (n = 550), MARC II yearlings, were assigned for breeding to one of four Angus sires with birth weight EPD of -.95, -82, +2.9, and +2.7 kg. At calving, heifers were assisted as needed. A gauge attached to the cal puller recorded applied traction pressure. Analysis of traction pressure detected only slightly larger amounts of variation (2 to 3%) affecting dystocia than the standard five-point scoring system. Dam weight did not affect calving difficulty score (CDS), except dam birth weights were heavier (P < .05) for CDS 5 (Caesarean section) than CDS 1 (unassisted). Dams requiring Caesarean section had smaller pelvic areas (P < .05), with no other differences among CDS. The CDS increased as calf birth weight and cal external measurements increased. Low EPD sires produced calves with smaller (P < .05) birth weights and smaller calf head and food circumferences and caused less dystocia than high EPD sires. The CDS did not affect subsequent pregnancy rates but did affect conception date of the second calf. Calves delivered by Caesarean section were lighter (P < .05) at weaning than other calves but had similar slaughter weights. As mean winter temperature increased (6.1 degrees C) from yr 1 to 3, calf birth weight decreased (4.6 kg) and calving difficulty decreased 23%. Results indicate sire birth weight EPD, calf birth weight and shape, dam pelvic area, and climate affected CDS, and CDS affected subsequent conception date.

Aging↗
PubMed1981

Comparison of single and multiple-trait selected sires. Response in mastitis traits.

Estimated somatic cell counts and incidence mastitis were measured on 163 daughters of two groups of bulls selected by two alternative criteria. Yield bulls were selected solely on progeny test for milk in first lactation; Merit bulls were selected by independent culling levels on fat-corrected milk yield, percent daughters culled in first lactation, and udder type conformation of daughters. Daughters of Yield sires exceeded daughters of Merit sires by 685 kg milk in first lactation. Groups did not differ significantly in measures of clinical mastitis or in measures of estimated cell counts of milk. Also, groups did not differ in kilograms milk discarded because of antibiotic treatment for mastitis, in spite of the large difference in total milk yield. Mean milk discarded per lactation completed was 171 kg, representing 64,243, and 207 g for parities one, two, and three.

Animals↗
PubMed1988

Association of rate-of-feathering genotypes in broilers with production and carcass composition traits. 2. Effect of genotypes and diet on processing traits and lipid deposition.

Five rate-of-feathering genotypes: K/K, K/k+, and k+/k+ in male and K/W and k+/W in female broilers were produced from matings of grandparent stocks of a common genetic background. Genotypes were compared for differences in processing characteristics and lipid deposition using isocaloric high and low protein diets from 28 to 52 days. The two female genotypes reared on the same diet did not differ on measures of plant weights, eviscerated carcass weights, breast weights, and abdominal fat pad weights. Significant differences were observed among the male genotypes reared on the same diet in plant weights, eviscerated carcass weights, and breast weights. All genotypes reared on the high protein diet had significantly increased plant weights, eviscerated carcass weights, and breast weights and significantly decreased abdominal fat pad weights and percentage carcass lipid.

Animals↗
PubMed1995

The use of feed restriction for improving reproductive traits in male-line white turkey hens. 2. Ovary morphology and laying traits.

The influence of feed restriction during rearing was investigated in male-line Large White breeder hens with regard to effects on ovarian morphology, egg production, laying patterns, and egg characteristics. Two hundred poults were reared from 4 to 28 wk of age under four treatments as follows: full-fed controls (FF), low-protein diet (12% CP from 12 to 28 wk; LP), and reduced BW (10 to 20% lower BW than FF; R10 and R20). At photostimulation (28 wk), all birds consumed a commercial breeder diet ad libitum for the remainder of the study (48 wk of age). Settable egg production (eggs per hen) to 48 wk for all hens, and those in lay was: FF, 39.4 (48.6); LP 42.7 (51.7); R10, 41.4 (52.8); R20, 40.7 (55.4). Inferior egg production per bird in R10 and R20 hens reflected a reduced persistency of lay. At first egg, hens of all treatments had a mean of 4.9 postovulatory follicles (POF) not accounted for by an egg. Number of unreconciled POF correlated with abdominal fat pad weight (P < or = .01). Ovary weight correlated with BW (P < .0001) and fat pad weight (P < .0004). Proportion of yolk and shell in the egg and egg specific gravity were improved with feed restriction. Sequence length was longest in R20 treatment hens and pause length shortest in R10 and R20 hens. Incidence of multiple-follicle sets was reduced in the R10 and R20 treatments. Feed restriction during rearing can potentially improve laying characteristics by altering ovarian morphology without limiting shell quality or yolk size. Quantitative feed restriction was most effective at improving egg quality, reducing average pause length, and reducing ovarian multiple-follicle sets. If problems with persistency of lay are addressed, the R10 and R20 treatments are the recommended rearing restriction treatments for male-line turkey breeder hen candidates.

Animals↗
PubMed1992

Determination of hemoglobin Bart's in alpha thalassemia traits by two-site immunoradiometric assay. II. Detection of hemoglobin Bart's in alpha thalassemia traits.

A sensitive method for the determination of minute amounts of Hb Bart's in hemolysate of alpha thalassemia-1 and alpha thalassemia-2 was carried out by two-site immunoradiometric assay. This technique is very sensitive and is able to detect minute amounts of substances. When this method is used with specific anti-Hb Bart's derived from affinity column chromatography, then labelled with radioactive 125I, the two-site immunoradiometric assay will contain both the sensitivity and specificity for the determination of Hb Bart's. In this study, parents of fetus with Hb Bart's hydrops fetalis contained high levels of Hb Bart's 0.73-1.11 per cent (mean +/- S.D. = 0.86 +/- 0.12%). Parents of Hb H diseases had Hb Bart's in two groups. The first group contained high levels of Hb Bart's of 0.73-1.20 per cent (mean +/- S.D. = 0.88 +/- 0.14%), while the second group had levels of 0.39-0.45 per cent (mean +/- S.D. = 0.42 +/- 0.02%). Mothers of patients with Hb H disease contained Hb Bart's of 0.42 +/- 0.48 per cent (mean +/- S.D. = 0.45 +/- 0.02%). Eight out of ten normal subjects contained low levels of Hb Bart's of 0.17-0.26 per cent (mean +/- S.D. = 0.22 +/- 0.04%), while two contained high levels of Hb Bart's of 0.46 and 0.43 per cent respectively. The two-site immunoradiometric assay was able to differentiate the level of Hb Bart's among alpha thalassemia-1, alpha thalassemia-2 and normal subjects.

Hemoglobins, Abnormal↗
PubMed1992

High and low litter size trait and its relationship with serum and urine progesterone, serum zinc, and serum phosphorus in New Zealand white rabbits and improvement for the low litter size trait.

A number of does was classified according to their initial litter size to high (> 6 bunnies, group 1) and low (< 5 bunnies, group 2) in New Zealand White rabbits. Incidence of low litter size in the herd in the present study was 23%. The number of matings/conception, total mortality, corpora lutea/foetus, number and percentage of resorbed foeti were markedly higher in group 2 than in group 1. The litter weight, number of foetuses, implantation sites, and corpora lutea in group 2 showed a marked decrease over group 1. Serum and urine progesterone levels in pregnant rabbits of group 2 were significantly (P < 0.01) lower than in group 1, however, non-efficacious progesterone levels were significantly (P < 0.01) lower in group 2. The zinc content in serum, foetal dry weight and uterine horn dry weight, and serum inorganic phosphate in group 2 were significantly (P > 0.01) lower than in group 1. The litter size was significantly (P < 0.01) correlated with zinc and inorganic phosphate in group 2, while it was correlated with serum and urine progesterone in the two groups. The correlation coefficients were significant (P < 0.01) between urine progesterone and serum zinc and between serum progesterone and inorganic phosphate more frequently in group 2 during the gestation period than in group 1. The treatment of group 2 does with calcium carbonate, sodium phosphate dibasic, and zinc acetate in drinking water improved the serum progesterone, urine progesterone, and non-efficacious progesterone in addition to serum zinc and inorganic phosphate, which led to improvement of the number of matings/conception, litter size and litter weight, and lowered total mortality.

Animals↗
PubMed1987

Molecular-marker-facilitated investigations of quantitative-trait loci in maize. I. Numbers, genomic distribution and types of gene action.

Individual genetic factors which underlie variation in quantitative traits of maize were investigated in each of two F2 populations by examining the mean trait expressions of genotypic classes at each of 17-20 segregating marker loci. It was demonstrated that the trait expression of marker locus classes could be interpreted in terms of genetic behavior at linked quantitative trait loci (QTLs). For each of 82 traits evaluated, QTLs were detected and located to genomic sites. The numbers of detected factors varied according to trait, with the average trait significantly influenced by almost two-thirds of the marked genomic sites. Most of the detected associations between marker loci and quantitative traits were highly significant, and could have been detected with fewer than the 1800-1900 plants evaluated in each population. The cumulative, simple effects of marker-linked regions of the genome explained between 8 and 40% of the phenotypic variation for a subset of 25 traits evaluated. Single marker loci accounted for between 0.3% and 16% of the phenotypic variation of traits. Individual plant heterozygosity, as measured by marker loci, was significantly associated with variation in many traits. The apparent types of gene action at the QTLs varied both among traits and between loci for given traits, although overdominance appeared frequently, especially for yield-related traits. The prevalence of apparent overdominance may reflect the effects of multiple QTLs within individual marker-linked regions, a situation which would tend to result in overestimation of dominance. Digenic epistasis did not appear to be important in determining the expression of the quantitative traits evaluated. Examination of the effects of marked regions on the expression of pairs of traits suggests that genomic regions vary in the direction and magnitudes of their effects on trait correlations, perhaps providing a means of selecting to dissociate some correlated traits. Marker-facilitated investigations appear to provide a powerful means of examining aspects of the genetic control of quantitative traits. Modifications of the methods employed herein will allow examination of the stability of individual gene effects in varying genetic backgrounds and environments.

Chromosome Mapping↗
PubMedDate not supplied

Marker assisted selection for the improvement of two antagonistic traits under mixed inheritance.

A Monte Carlo simulation was used to investigate the potential of Marker Assisted Selection (MAS) in a multiple-trait situation. Only additive effects were considered. The base population was assumed to be in linkage equilibrium and, next, the population was managed over 15 discrete generations, 10 males and 50 females were chosen out of the 100 candidates of each sex. Performance for two traits was simulated with an overall heritability of a given trait equal to 0.25 or 0.10 and the overall genetic correlation between traits was generally equal to -0.4 except in one case where it was equal to 0. The model involved one biallelic QTL, accounting for 10 or 20% of the genetic variance of a given trait, plus polygenes. Initial allelic frequencies at the QTL, were generally equal to 0.5 but in one case were equal to 0.1 and 0.9. A marker with 120 different alleles in the 60 founder parents was simulated in the vicinity of the QTL. Two values of the recombination rate between these two loci were considered, 0.10 and 0.02. The genetic evaluation was based on a multiple-trait BLUP animal model, accounting (MAS) or not (conventional BLUP) for marker information. Two sets of simulations were run: (1) a "missing data" case, with males having no record for one of the traits, and (2) a "secondary trait" case, with one trait having a weight in the aggregate genotype 4 times less than the other trait and the QTL acting only on this secondary trait. In the first set, evaluation methods were found to mainly affect the accuracy of overall genetic values prediction for the trait with missing data. In comparison with BLUP, MAS led to an extra overall genetic response for the trait with missing data, which was strongly penalised under the conventional BLUP, and to a deficit in response for the other trait. This more balanced evolution of the two traits was obtained, however, at the expense of the long-term overall cumulated response for the aggregate genotype, which was 1 to 2.5% lower than the one obtained under the conventional BLUP. In the second set of simulation, in the case of low initial frequency (0.1) of the QTL allele favourable to the secondary trait, MAS was found to be substantially more efficient to avoid losing this allele than BLUP only when the QTL had a large effect and the marker was close. More benefits should be expected from MAS with more specific applications,such as early selection of animals, or by applying dynamic procedures i.e. letting the respective weights to QTL and polygenic values in the selection criterion vary across generation.

Animals↗
PubMed2005

Genetic and phenotypic parameter estimates of total and partial lifetime traits for dairy ewes.

A data file with 11,547 lactations for 2602 Spanish Churra ewes, daughters of 100 sires and 2179 dams, was used to estimate genetic and phenotypic parameters of total and partial lifetime traits with a multiple-trait animal model using REML. These ewes first lambed between 1992 and 1998 and belonged to 27 flocks enrolled in the nucleus scheme of the breed. The study took into account 4 life span traits, 2 productive traits, and 2 reproductive traits. Lifetime revenues from milk and lambs were calculated. Daily traits for both milk and revenues of lifetime, productive life, and useful life were also calculated. Partial lifetime traits were considered for the first 3 parities. The model included flock and birth year within flock as fixed effects and animal as a random effect. Both fixed effects contributed significantly to variation of all total lifetime traits. Milk production level was included in the model as a covariable to adjust life span traits. Heritability estimates for life span traits were low (0.02 to 0.06), indicating few possibilities for direct genetic selection. Genetic and phenotypic correlations among life span traits averaged 0.90 and 0.87, respectively. Heritabilities for daily milk and revenue traits were always higher than those for their corresponding lifetime traits. Heritability for milk yield per day of useful life was 0.25 (+/-0.04). Heritability estimates for partial lifetime performance traits increased notably when more parities were included (from the first parity to the first 3 parities). Their genetic and phenotypic correlations with total lifetime traits also increased gradually when more information was considered. These results indicate that possibilities for early genetic selection for some lifetime traits are not totally excluded.

Animals↗