2. Birds were reared for 35 d, and morphological measurements consisting of the length and width of breast muscle were recorded for all birds using a digital caliper. After slaughtering, the weight and percentage of carcass traits were measured on chilled carcasses. The dimensions of breast muscle were measured in 638 birds with an ultrasound scanner before slaughter at 35 d of age.
3. Genetic parameters from univariate and bivariate analyses were obtained by restricted maximum likelihood using ASREML software.
4. Genetic correlations between body weight at 35 d (BW35) and the percentage of carcass traits were low. Therefore, selection for BW35 may not effectively improve the yield of carcass components in Japanese quail.
5. High genetic correlations between carcass traits and ultrasonic measurements compared to morphological measurements suggest that the ultrasonic technique is a better method to improve breast weight and yield in Japanese quail. 相似文献
2. Genetic and phenotypic correlations among enzyme activities at the three ages were positive and high.
3. Genetic correlations of enzyme activities with production traits indicated that the bird having higher activities of these enzyme will grow faster, mature earlier and produce heavier but fewer eggs. 相似文献
2. Nineteen models were evaluated to identify the best orders of Legendre polynomials. A model with Legendre polynomial of order 3 for additive genetic effect, order 3 for permanent environmental effects and order 1 for maternal permanent environmental effects was chosen as the best model.
3. According to the best model, phenotypic and genetic variances were higher at the end of the rearing period. Although direct heritability for BW reduced from 0.18 at hatch to 0.12 at 7 d of age, it gradually increased to 0.42 at 49 d of age. It indicates that BW at older ages is more controlled by genetic components in Japanese quail.
4. Phenotypic and genetic correlations between adjacent periods except hatching weight were more closely correlated than remote periods. The present results suggested that BW at earlier ages, especially at hatch, are different traits compared to BW at older ages. Therefore, BW at earlier ages could not be used as a selection criterion for improving BW at slaughter age. 相似文献
2. The data conformed to a mixed model and adjustments were made for the fixed effects sex, hatch date and location. Adjustment improved the precision of the estimates by reducing the error variances significantly.
3. Rearing equal numbers of birds from each family at different locations made the interactions negligible.
4. Weight gain was greater if illumination intensity up to 35 d was less.
5. Females were not heavier on the 1st day but were heavier on the 14th and 35th days than males.
6. Variance components and genetic parameters were estimated. 相似文献
2. Egg production, egg weight and food consumption were recorded on 1200 hens in every generation. Parent females were selected on individual performance. Males were not recorded and selected at random within half sib families to minimise rate of inbreeding.
3. A linear selection response of 0.46 and 0.43 monetary units per generation was observed, which resulted in a total response of 19.8% and 18.2% of the phenotypic mean of the base population over the 5 generations. A large increase in egg weight was the most important reason for the selection response in income minus food cost.
4. Further changes in associated traits were: an increase in egg number and egg mass, and a decrease in age at first egg, body weight and food: egg mass ratio.
5. The direct and correlated selection responses were similar in both lines. The realised response was somewhat less than expected in both lines.
6. A summary of phenotypic and genetic parameters, estimated from the data, is given. All genetic correlations between income minus food cost and the associated traits analysed, were in a favourable direction. 相似文献
2. The heritabilities for oviposition interval, 0.54 in NL and 0.52 in CL, were much higher than those for egg number or rate of lay and the genetic correlation between intervals in the two lighting environments was 0.82, suggesting some interaction between genotype and lighting regimen.
3. The genetic correlations between mean oviposition interval in either environment and conventional measures of egg production were all high and negative and, together with the above heritability estimates, suggested a possible advantage of oviposition interval as a selection criterion for improvement of egg production.
4. In NL, mean and standard deviation of oviposition times showed moderate to high heritabilities and high genetic correlations with oviposition interval, as expected from their close physiological relations. 相似文献
2. Over the first 10 generations with selection almost exclusively for number of eggs to the age of 273 d, all traits, except rate of mortality, showed significant changes. Regressions per year were: 273 d production, 3.07 eggs; 497 d production, 5.18 eggs; production from 274 to 497 d, 2.43 eggs; age at first egg, ‐2.33 d; mean weight of first 10 eggs, ‐0.82 g; body weight at 497 d, ‐19.02 g and rate of mortality, 0.19%.
3. Over the rest of the period increasing selection pressure for egg weight has been applied. This resulted in positive changes for this trait and no or small negative changes in egg number.
4. In general, heritabilities and genetic correlations did not change over the period of selection. The heritability of the main trait of selection, production to 273 d was 0.19 ± 0.04 and heritabilities of egg size traits about 0.50.
5. The genetic correlation between egg production to 273 d and mean weight of first 10 eggs was estimated as ‐0.37 ± 0.06 but from the observed response a realised genetic correlation of ‐0.97 was calculated. 相似文献
2. A total of 8534 records from 900 quail, hatched between 2014 and 2015, were used in the study. Average weekly egg weights and egg numbers were measured from second until sixth week of egg production.
3. Nine random regression models were compared to identify the best order of the Legendre polynomials (LP). The most optimal model was identified by the Bayesian Information Criterion. A model with second order of LP for fixed effects, second order of LP for additive genetic effects and third order of LP for permanent environmental effects (MTRR23) was found to be the best.
4. According to the MTRR23 model, direct heritability for EW increased from 0.26 in the second week to 0.53 in the sixth week of egg production, whereas the ratio of permanent environment to phenotypic variance decreased from 0.48 to 0.1. Direct heritability for EN was low, whereas the ratio of permanent environment to phenotypic variance decreased from 0.57 to 0.15 during the production period.
5. For each trait, estimated genetic correlations among weeks of egg production were high (from 0.85 to 0.98). Genetic correlations between EW and EN were low and negative for the first two weeks, but they were low and positive for the rest of the egg production period.
6. In conclusion, random regression models can be used effectively for analysing egg production traits in Japanese quail. Response to selection for increased egg weight would be higher at older ages because of its higher heritability and such a breeding program would have no negative genetic impact on egg production. 相似文献
2. The data contain information about the laying performance of 1831 individuals in the first year of laying. To describe the trajectory of the laying performance, 10 mathematical models were tested. For the genetic parameter estimation of egg production, data from 1038 birds were used with a production higher than 20 eggs during the first season of laying.
3. The analysis of egg production was based on single and multi-trait models. Heritability, genetic and phenotypic correlations between phases of the laying performance as well as breeding values were estimated.
4. The best adaptation to the goose egg laying curve was the Ali and Schaeffer model. The estimates of heritability were 0.20 (0.06 SE) using the single-trait model and ranged from 0.12 to 0.24 using the multi-trait model.
5. The results suggest that the BLUP method can support the conservation programme. 相似文献
2. Three selection lines were established from a common population, two low lines and one high line. In addition, one control line was kept. The generation interval was one year and the experiment lasted for 4 generations.
3. The direct selection response was considerable and the realised heritability was close to 0.5. Food intake and food conversion (FCR) were lower in the low lines than in the high line.
4. The correlated selection responses showed no phenotypic or genetic correlations between percentage residual food consumption and egg production, but one of the low lines had a heavier adult body weight than the high line. No undesirable correlated responses were observed. 相似文献
The more severely confined birds had depressed plasma alkaline phosphatase activity but a raised plasma cholesterol level after 35 d. The alkaline phosphatase activity returned to normal after 70 d but the hypercholesterolaemia persisted. Acid phosphatase activity and plasma protein levels were unaffected by the treatments.
Pullets in the smaller cages laid fewer eggs but egg weight was unaffected.
Neither percentage metabolisable energy nor metabolisable nitrogen of the diet was affected by the severity of confinement, though less dietary nitrogen was retained by either group in the first half of the confinement period.
Severe confinement resulted in higher values of percentage metabolisable calcium and phosphorus by the 35th d but these decreased by the 70th d. In the less severely confined birds these values by the 70th d were higher than those at the 35th d. 相似文献
2. The estimates of heritability for the frequency of cracked eggs ranged from 0.11 to 0.43, for egg number from 0.12 to 0.29 and for egg weight from 0.58 to 0.65.
3. The estimates of the genetic correlations between the traits were variable but in general showed no evidence of antagonism between a reduction in crack frequency and an increase in the production traits.
4. The efficiency of selection for reduction in the frequency of cracked eggs based on early measurements is briefly discussed. 相似文献
2. A randombred control population of known pedigree was used to measure the environmental trends.
3. Selection in pure lines resulted in concomitant improvement in the crosses for the selected as well as the correlated traits.
4. Cross performance was comparatively more than expected on the basis of mid‐parent values, indicating involvement of non‐additive gene action in the expression of cross performance.
5. Crosses responded better to independent culling level selection for egg weight than their parents.
6. Heterosis appeared to increase in later generations as compared with initial generations of selection. 相似文献
2. Free range (FR) and standard (STD) broilers were killed and processed under commercial conditions and the M. pectoralis major muscle assessed for ultimate pH (pHu), sarcomere length, cooking loss and texture 24 h and 7 d after slaughter.
3. Although FR broilers were females with an average age of 60 d, whereas the STD broilers were 45 d old and predominantly male, there were no significant differences in mean values obtained for pHu, sarcomere length, cooking loss and shear force results between the two bird types.
4. While aging for 7 d increased the pHu and cooking loss means, sarcomere length means remained unchanged and shear force values decreased by 6% and 9% for FR and STD birds respectively.
5. Variability in shear force values also decreased on aging for 7 d, no birds having values above 4 kg/cm2 on day 7 whereas 16% were above this value on day 1.
6. There were significant correlations between the results for shear force, pHu and sarcomere length, indicating that increased shear force values were associated with a decrease in both pHu and sarcomere length.
7. These correlations suggest that variability in the texture of cooked M. pectoralis major from FR and STD chickens is strongly influenced by those post‐mortem biochemical changes which lead to the development of rigor during the early stages of processing. 相似文献
Genetic correlations were estimated between pure‐line and cross‐line performance using both sire and dam covariances. These approached unity for body weight, egg quality traits and adult mortality but were considerably less than unity for production, sexual maturity, blood spots and mortality during growth and mortality due to Marek's disease.
The possible bias due to genotype x environment interaction is discussed and it is concluded that such a bias, if present, is small, and that in spite of possible G × E interaction effect the genetic correlations between pure‐line and cross‐line performance for production and sexual maturity are less than one. The same holds true of mortality during growth and to Marek's disease although these estimates are much less precise.
The genetic correlation between pure‐breds and cross‐breds appears to decrease over the span of the five generations.
Use of cross‐line performance will permit more efficient selection for traits when the genetic correlations are much less than one. 相似文献
2. During the last 7 years a random breeding sample of the production flock served as a genetic control.
3. Regressions of deviations of the production flock from the control flock on years, were highly significant for age at sexual maturity (‐2.18 d), egg production up to 275 d old (3.04 eggs), egg production to 500 d old (5.04 eggs) and egg weight at 14 months old (October) ( — 0.79 g).
4. The heritability of egg production up to 275 d old declined significantly from 0.35 to 0.19.
5. The realised heritability of egg production up to 275 d old was estimated to be 0.14.
6. The genetic correlation between egg production up to 275 d old and production in the residual part of the year was 0.48.
7. The rate of inbreeding in the production flock was 0.515% per generation and the expected rate of inbreeding in the control flock 0.21% per generation. 相似文献
2. Compared with the normal diet the low‐protein diet caused a decrease in growth rate which at 38 d was 37% and 25% for male and female chickens, respectively.
3. A genotype‐level of protein interaction was demonstrated for weight at 38 d. Expressed as a genetic correlation for the same trait and measured in the two feeding environments the values were about 0.33.
4. In estimating the genetic correlation the interaction as well as the covariance method were used. The two methods did not give the same estimates.
5. Heritabilities for weight at 38 d tend to be larger in the low‐protein environment. 相似文献
2. Heritabilities of 0.39, 0.19 and 0.20 were found for IFC, FCR and FSC, respectively.
3. Genetic correlations of ?0.61, 0.15 and 0.06 were found between IFC and FCR, IFC and FSC, FCR and FSC, respectively.
4. A positive, that is unfavourable, correlated selection response for FSC was observed in both selection lines. 相似文献
2. During the first 42 h as well as at the end of incubation, LG embryos were developmentally accelerated in comparison with their HG counterparts. An expected increase of line divergence across generations was observed only in traits analysed at the end of incubation.
3. In contrast to early generations, LG embryos continuously exhibited a higher BW than HG embryos and this difference temporarily disappeared only around incubation d 8. Analogous to early generations, the HG compared with LG embryos showed two periods of transient growth retardation compensated subsequently by a higher growth rate (incubation d 3–8 and 8–16).
4. More pronounced growth retardation of HG versus LG embryos in late versus early generations corresponded to more distinct decrease of HG versus LG growth rate during the first post-hatch days. Likewise, a disappearance of line BW differences on incubation d 8 characterising the late generations corresponded to the elimination of line differences in adult BW.
5. Alterations of growth pattern were associated with changes of egg size. While HG quail maintained a relatively constant adult BW and egg size across generations, the gradually increasing incidence of large eggs in the LG line allowed selection of birds with higher growth potential, which in turn amplified the line differences in the embryonic BW and eliminated the line differences in adult BW. Line differences in egg composition (larger albumen with lower density in LG compared with HG eggs) apparently contributed to the strengthening of line developmental divergence during incubation.
6. Transient lack of nutrient supply to HG embryos due to their developmental delay is probably responsible for a higher HG versus LG embryo mortality. 相似文献
2. Storage of eggs for 14 d caused a delay of 134 h in the mean total incubation period.
3. Female embryos hatched about 3 h earlier than males in the non‐stored eggs but there was no difference between the sexes in eggs stored for 14 d.
4. Rate of weight loss during incubation was similar in both non‐stored and stored eggs: there was no relationship between weight loss at 19 d incubation and total incubation period.
5. Hatchability of fertile eggs was 19.5% lower in eggs stored for 14 d and proportionately more embryos died between 4 d and 18 d incubation than in the non‐stored eggs. 相似文献