摘要 :
Residual feed intake is a linear function of feed intake, production and maintenance of liveweight, and as such is an attractive characteristic to use to represent production efficiency. The phenotypic and genetic parameters of re...
展开
Residual feed intake is a linear function of feed intake, production and maintenance of liveweight, and as such is an attractive characteristic to use to represent production efficiency. The phenotypic and genetic parameters of residual feed intake can be written as a function of its constituent traits. Moreover, selection indices containing the constituent traits are equivalent with an index that includes residual feed intake. Therefore, definition of the term residual feed intake may be useful to interpret variation in production efficiency, but it does not help in obtaining a better selection response than selection on constituent traits alone. In fact, multiple trait genetic evaluation of constituent traits rather than residual feed intake is likely to be more accurate as this more appropriately accommodates different models for the constituent traits and missing data. For residual feed intake to reflect true biological efficiency in growing animals, it is important that feed intake and liveweight are accurately measured. Accounting for growth and body composition would significantly help in revealing between-animal variation in feed utilisation. Random regression models can be helpful in indicating variation in feed efficiency over the growth trajectory.
收起
摘要 :
Naked neck and dwarf gene lines which were under low intensity of selection for 6-week body weight for 11 generations, were utilized in the present study. The body weight at 6 weeks in I I generations since 1995-96 to 2005-06 rang...
展开
Naked neck and dwarf gene lines which were under low intensity of selection for 6-week body weight for 11 generations, were utilized in the present study. The body weight at 6 weeks in I I generations since 1995-96 to 2005-06 ranged between 798 and 1217 g in naked neck gene line and 601 and 834 g in dwarf gene line. No definite phenotypic trend in gain in body weight was observed over generations in both the lines. Phenotypic response in 6-week body weight was -15.48 +/- 11.12 g in naked neck and -8.97 +/- 6.59 g in dwarf gene line, which were nonsignificant. Genetic and phenotypic parameters for growth and production of 11th generation were analysed. The average body weight at 4-week and 6-week, respectively were 467.30 +/- 0.67 g and 877.60 +/- 0.10 g in naked neck and 258.55 +/- 0.66 g and 607.32 +/- 0.12 g, respectively, in dwarf gene line (S 11 generation). Heritability estimates (h(2)S) of 4-week and 6-week body weight, respectively, were 0.16 +/- 0.08 and 0.06 +/- 0.05 in naked neck and 0.16 +/- 0.09 and 0.13 +/- 0.08 in dwarf. Genetic (r(g)) and phenotypic (r(p)) correlations between these 2 traits were 0.56 +/- 0.33 and 0.42 in naked neck and 0.45 +/- 0.44 and 0.57 in dwarf. The average production performance of ASM, 20-week body weight, 40-week body weight, 28-week egg weight, 32-week egg weight, 40-week egg weight and 40-week egg production were 175.81 +/- 0.09 d, 2349.15 +/- 2.15 g, 3 157.90 +/- 2.23 g, 53.46 +/- 0.02 g, 57.58 +/- 0.02 g, 61.45 +/- 0.03 g and 62.60 eggs +/- 0.14, respectively, in naked neck and 151.50 d +/- 0.05, 2 103.98 g +/- 2.80, 2 562.93 g +/- 0.79, 48.94 g +/- 0.01, 52.32 g +/- 0.01, 56.54 g +/- 0.01 and 59.30eggs +/- 0.08, respectively, in dwarf. In naked neck the heritability estimates from sire component were high for majority of the traits, while in dwarf the heritability estimates of the traits from sire component were low except for egg weights at 28 and 32 weeks of age, which were high. The genetic and phenotypic correlations between different combinations of traits varied in different directions and magnitude in both lines.
收起
摘要 :
Data from a Western Australian experimental flock of Merino sheep were used to estimate genetic and phenotypic parameters for clean fleece weight (CFW), greasy fleece weight (GFW), average fibre diameter (FD), and clean yield (Y) ...
展开
Data from a Western Australian experimental flock of Merino sheep were used to estimate genetic and phenotypic parameters for clean fleece weight (CFW), greasy fleece weight (GFW), average fibre diameter (FD), and clean yield (Y) from hogget fleeces as well as liveweights at birth (BWT), weaning (3WT), 8-9 months (8WT), 11-12 months (11WT) and 14-15 months (14WT) of age. The estimates were derived for male and female hoggets using restricted maximum likelihood REML. Simple models were fitted in which most environmental effects were omitted for comparison with results from models containing all recorded significant environmental effects. There were no significant differences amongst heritability estimates between models or sexes. Genetic correlations were calculated between sexes for each trait, with none being significantly different to unity. Ranges of heritability estimates across models and sexes were: GFW, 0.30-0-42; CFW, 0.26-0.44; Y, 0.46-0.59; FD, 0.47-0.59; BWT, 0.16-0.33; 3WT, 0.32-0.39; 8WT, 0.22-0.36; llWT, 0-27-0.44; 14WT, 0.27-0.50. Estimates of genetic and phenotypic correlations were in reasonable agreement with other literature values. As with the heritability estimates, the model fitted did not result in important differences in either genetic or phenotypic correlations.
收起
摘要 :
Phenotypic and genetic parameter estimates for reproductive traits in Kermani sheep were estimated using reproductive records of 860 ewes. Data were collected during 1995-2007 at the experimental breeding station of Kermani sheep,...
展开
Phenotypic and genetic parameter estimates for reproductive traits in Kermani sheep were estimated using reproductive records of 860 ewes. Data were collected during 1995-2007 at the experimental breeding station of Kermani sheep, south-east of Iran. Investigated traits were litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lamb born (LMWLB) and litter mean weight per lamb weaned (LMWLW) as basic traits, total litter weight at birth (TLWB) and total litter weight at weaning (TLWW) as composite traits. Quantitative genetic analyses were performed applying restricted maximum likelihood (REML) procedure under repeatability models. Ewe age had significant effect on LMWLB, LMWLW, TLWB and TLWW (P <0.01). However, LSB and LSW were not affected by age of the ewe. All the studied traits were significantly affected by lambing year (P <0.01). Direct heritability estimates for LSB, LSW, LMWLB, LMWLW, TLWB and TLWW were 0.01, 0.03, 0.13, 0.22, 0.06 and 0.18, respectively, while the corresponding repeatabilities were 0.08, 0.10, 0.17, 0.29, 0.09 and 0.23, respectively. Genetic correlation estimates between the investigated traits ranged from 0.94 for LSB-LMWLB and LSW-LMWLW to 0.99 for LSB-TLWW. Phenotypic and environmental correlations were generally lower than those of genetic correlations. Phenotypic correlations ranged from 0.34 for LSB-LMWLB to 0.58 for TLWB-TLWW. Environmental correlations ranged from 0.33 for LSB-LMWLB and LSW-LMWLB to 0.33 for LMWLB-LMWLW. The results suggested that selection based on TLWW could be more effective than the other traits on improvement of reproductive performance in Kermani ewes.
收起
摘要 :
A data file on 36396 lactations was used to determine the strength of the phenotypic relationship between productive, reproductive and lifespan traits for 7935 Spanish Churra ewes. These ewes first lambed between 1989 and 1997 and...
展开
A data file on 36396 lactations was used to determine the strength of the phenotypic relationship between productive, reproductive and lifespan traits for 7935 Spanish Churra ewes. These ewes first lambed between 1989 and 1997 and belonged to 23 flocks. The study took into account four lifespan traits (lifetime, productive life, useful life and. lifetime score), three productive traits (total milk yield produced during lifetime, lambs weaned during ewe lifetime and total revenues from sold milk and weaned lambs during lifetime) and two reproductive traits (age at first lambing and mean interval between successive lambings). Moreover, milk yield and revenues from sold milk and weaned lambs were calculated per day of lifetime, productive life and useful life. Partial lifespan traits were considered for the first three parities. The model included flock, birth year within flock and season of birth of the ewe as fixed effects. The first two effects contributed significantly to variation in all traits, while season significantly affected lifespan traits, productive traits and age at first lambing. Milk production level was added to the model for lifespan traits only. It significantly contributed to explaining the variation in all life-span traits with high percentage of variance explained averaging 14.91%. Lifetime averaged 2324 d. Productive life accounted for 57% of lifetime while useful life represented 50% of productive life. Age at first lambing averaged 622 d and average days dry during lifetime was 560. During lifetime, ewes gave an average of 4.6 parities, 6.5 weaned lambs and 636 l of milk. Average revenue from milk and lambs during lifetime was ?673. Milk/day of lifetime, productive life and useful life averaged 0.26, 0.51 and 0.93 l, respectively. The corresponding per-day revenues from sold milk and weaned lambs were, ?0.27, ?0.55 and ?1.01, respectively. Lifespan and productive traits had strong relationships (r_p among these traits ranged between 0.75 and 0.95). Two-parity and three-parity per-day milk yield had moderately high correlation (0.70-0.83) with total lifetime per-day milk yield traits. Therefore, good use of these traits would be helpful in determining best individuals early in life.
收起
摘要 :
With the objective of evaluating the resistance level of commercial corn hybrids and comparing the efficiency of the estimates of the area under the disease progress curve (AUDPC) and that of the phenotypical stability parameters ...
展开
With the objective of evaluating the resistance level of commercial corn hybrids and comparing the efficiency of the estimates of the area under the disease progress curve (AUDPC) and that of the phenotypical stability parameters in the evaluation of resistance maize white spot and gray leaf spot, three experiments were carried out in the agricultural year of 2007/2008 in three environments. Twelve commercial maize hybrids were used, in a randomized block experimental design with three replications. Five evaluations of disease severity (maize white spot and gray leaf spot) based on visual symptoms were performed at seven-day intervals from the 80(th) day after maize emergence, ranging from 1 (highly resistant) to 9 (highly susceptible). The area under the disease progress curve (AUDPC) was estimated, as were the phenotypical stability parameters, i.e., the linear regression coefficient (b(i)) between the independent variable evaluation time (x), and the dependent variable, disease severity (y) and the determination coefficient (R-2). It was found that in the case of maize white spot and maize gray leaf spot, both methodologies used proved to be effective in the discrimination of the resistance level of the hybrids, enabling them to be ranked in a similar way. The most resistant hybrids to maize white spot and maize gray leaf spot were AG7088, AG 7010 and 2B707, and the most susceptible were 30F44, 30F53 and AG8021. The 30K64, DKB177, DKB390 and Impacto hybrids showed variable levels of resistance with the environment.
收起
摘要 :
Genetic parameters for scale activity score (AS) were estimated from generations 5, 6, and 7 of a randomly selected, composite population composed of Duroc, Large White, and 2 sources of Landrace (n = 2,186). At approximately 156 ...
展开
Genetic parameters for scale activity score (AS) were estimated from generations 5, 6, and 7 of a randomly selected, composite population composed of Duroc, Large White, and 2 sources of Landrace (n = 2,186). At approximately 156 d of age, pigs were weighed (BW) and ultrasound backfat measurements (BF1, BF2, and BF3) were done. While pigs were in the scale, an AS was assigned, which ranged from 1 (calm) to 5 (highly excited), where 58.1, 28.5, 8.9, 4.0, and 0.5% were scored as 1, 2, 3, 4, and 5, respectively. Statistical model effects were year-week of measurement, sex, covariates of age for AS and BW or BW for BF1, BF2, and BF3, and an animal direct genetic effect. A 5-trait linear mixed model was used. Estimated heritabilities were 0.23, 0.54, 0.56, 0.52, and 0.48 for AS, BW, BF1, BF2, and BF3, respectively. Estimated genetic correlations between AS and BW, AS and BF1, AS and BF2, and AS and BF3 were 0.38, 0.11, 0.12, and 0.16 respectively. Results indicated AS had a heritable genetic component and was genetically correlated with performance traits. Estimated genetic correlations between AS and backfat measurements adjusted to a common BW were negative, as was the genetic correlation of AS with BW. Therefore, selection for more docile animals would be expected to result in fatter, faster growing pigs.
收起
摘要 :
Genetic and non-genetic influences on the body weights of 2425 Bharat Merino lambs sired by 154 rams over 1982-1996 were evaluated. Year and season of lambing, sex of lamb, type of birth, age of dam and ewe weight were significant...
展开
Genetic and non-genetic influences on the body weights of 2425 Bharat Merino lambs sired by 154 rams over 1982-1996 were evaluated. Year and season of lambing, sex of lamb, type of birth, age of dam and ewe weight were significant sources of variation for lamb weights and daily gains. The average lamb weights were 3.1 +/- 0.03 kg at birth, 15.0 +/- 0.2 kg at 3 months, 21.6 +/- 0.2 kg at 6 months, and 29.1 +/- 0.3 ka at 12 months of age, and average daily gains were 133 +/- 1.6 and 52 +/- 0.9 a at pre- and post-weaning periods, respectively. Correspondingly, estimates of heritability were 0.23 +/- 0.07, 0.14 +/- 0.06, 0.52 +/- 0.09, 0.51 +/- 0.09, 0.17 +/- 0.07 and 0.56 +/- 0.09. Genetic and phenotypic correlations among growth traits were significant and in the desirable direction. These estimates demonstrate that there is an opportunity for improvement of Bharat Merino lambs based on selection for growth rate.
收起
摘要 :
Most of the strategies of breeding plan in animal depend on heritability which is one of the most important genetic parameter. Data from 698 pigs were used to examine the potential usefulness of growth curve parameters as selectio...
展开
Most of the strategies of breeding plan in animal depend on heritability which is one of the most important genetic parameter. Data from 698 pigs were used to examine the potential usefulness of growth curve parameters as selection criteria for altering the relationship between body weight and age. A logistic growth function was found to be best fitted to model growth through 24 weeks of age. Estimates of asymptotic body weight (K), maximum growth rate (R) and age at point of inflection (t*) have been obtained by non-linear least squares. Phenotypic and genetic parameters were estimated for the estimated growth curve parameters and for body weights through 24 weeks of age. Half-sib model were used for computing genetic parameters. Heritabilities of estimated growth curve parameters were: K(0.301 +/- 0.121), R (0.102 +/- 0.070) and t* (0.874 +/- 0.228).
收起
原文获取