Index selection for both current and future generation gains

1978 ◽  
Vol 26 (2) ◽  
pp. 111-118 ◽  
Author(s):  
J. W. James
Keyword(s):  
Body Weight ◽  
Selection Index ◽  
Future Generation ◽  
Index Selection ◽  
Economic Returns ◽  
Present Value ◽  
Individual Traits ◽  
Selection Decisions ◽  
Selection For ◽  
Combined Selection

ABSTRACTWhen economic returns from current and future generation gains are comparable in magnitude, selection decisions should take account of both sources of gain. A combined selection index is devised to maximize the present value of discounted returns from all sources. The index depends on genetic and phenotypic variances and covari-ances, population structure, discount rate and the relation of annual returns to individual traits. The combined index can be regarded as the sum of separate indices maximizing returns from each source. The method is illustrated with a simple example using wool weight and body weight in sheep.

SELECTION FOR NURSING ABILITY AND ADULT WEIGHT IN MICE

Genetics ◽  
1978 ◽  
Vol 88 (4) ◽  
pp. 761-780
Author(s):  
J Nagai ◽  
E J Eisen ◽  
J A B Emsley ◽  
A J McAllister
Keyword(s):  
Body Weight ◽  
Selection Index ◽  
Genetic Correlations ◽  
Regression Coefficients ◽  
Index Selection ◽  
Single Pair ◽  
Adult Weight ◽  
Selection For ◽  
Possible Cause ◽  
Line Generation

ABSTRACT Three selection treatments were conducted for 12 generations in each of two base populations (P and Q): (1) increased nursing ability of the mother (n12), as measured by mean 12-day weight of eight young within a crossfostering set (MP and MQ lines), (2) increased adult (42-day) body weight of the offspring (w42) (WP and WQ lines), and (3) performance combining the two traits (n12 and w42) into a selection index (BP and BQ lines). Lines CP and CQ were maintained as unselected controls in each population. In each line-generation subclass, 92 single-pair matings were made and the offspring assigned to balanced crossfostering sets of four dams each. Regression coefficients of mean performance (in grams) on generations were 0.080 ±0.029 and 0.054 ± 0.031 for n12 in MP and MQ, and 0.680 ± 0.039 and 0.868 ± 0.051 for w42 in WP and WQ, respectively. The BP and BQ lines showed genetic gains in n12 (0.090 and 0.053, respectively) and w42 (0.576 and 0.696) intermediate between the performance of MP and WP, and MQ and WQ, respectively, except for n12 of BQ. Realized heritabilities for n12 were 0.16 ± 0.05 and 0.11 ± 0.06 and those for w42 were 0.40 ± 0.02 and 0.43 ± 0.03 for P and Q, respectively. The realized genetic correlations between n12 and w42 were 0.70 ± 0.07 and 0.73 ± 0.08 in P and Q, respectively. The ratios of the predicted to observed responses in MP, BP and BQ were 0.99, 1.03 and 0.89, respectively. However, the predicted and observed responses differed in MQ, WP and WQ; the ratios were 1.29, 0.65 and 0.65, respectively. The observed combined responses for n12 and w42 in the index lines (BP and BQ) were smaller than the optimum expected from index selection. A possible cause was that the estimated genetic correlations (0.22 ± 0.16 and -0.17 ± 0.16 for BP and BQ, respectively) and heritabilities (0.39 ± 0.03 and 0.28 ± 0.02, respectively) for w42 that were used to construct the selection index were smaller than the respective realized parameters.

A comparison of the topmaking performance of wool from sheep selected by index and visual methods

1999 ◽  
Vol 39 (8) ◽  
pp. 941 ◽  
Author(s):  
A. L. Vizard ◽  
K. A. Hansford
Keyword(s):  
Body Weight ◽  
Coefficient Of Variation ◽  
Selection Index ◽  
Fibre Diameter ◽  
Visual Assessment ◽  
Index Selection ◽  
Visual Methods ◽  
Merino Sheep ◽  
Fleece Weight ◽  
Index Value

Summary. The topmaking performance of fleeces from sheep that were ranked high or low on index selection using objective measurement was compared with that of sheep from the same flock that were ranked high or low on visual assessment. A flock of 451 15-month-old fine-wool Merino sheep were classed by 2 experienced fine-wool sheep classers into 3 grades: best, average and culls. Forty-four sheep were assessed as ‘best’ and 77 sheep were graded as ‘culls’ by both classers. These sheep were defined as the ‘best visual’ and ‘worst visual’ sheep, respectively. Measurements of clean fleece weight, mean fibre diameter, coefficient of variation of fibre diameter and body weight were used in a selection index to rank all sheep in the flock. The selection index was designed to rapidly reduce mean fibre diameter and slowly increase clean fleece weight, whilst maintaining staple strength and body weight. The 44 sheep with the highest index value were defined as ‘best index’ sheep and the group of 77 sheep with the lowest index or obvious physical faults were defined as the ‘worst index’ sheep. Twenty-five fleeces were randomly selected from each of the ‘best’ and ‘worst visual’, ‘best’ and ‘worst index’ sheep for individual processing through to top. The fleeces from the ‘best index’ sheep produced greater quantities of tops that were significantly finer, longer, of lower curvature and produced less noil than all other groups. In contrast to the large difference in quality between tops from the ‘best’ and ‘worst index’ sheep, there was little difference in quality between tops from the ‘best’ and ‘worst visual’ sheep. This indicates that the traditional wool producer views of wool quality are unrelated to processing performance. It was concluded that Merino sheep selected by index selection using direct measurement of fleece weight, mean fibre diameter and coefficient of variation of diameter as selection criteria produced greater quantities of wool of superior processing performance to that from sheep selected using visual assessment.

Preweaning losses of piglets as a result of index selection for reduced backfat thickness and increased growth rate

1993 ◽  
Vol 73 (2) ◽  
pp. 437-442 ◽  
Author(s):  
R. M. McKay
Keyword(s):  
Growth Rate ◽  
Key Words ◽  
Selection Index ◽  
Backfat Thickness ◽  
Index Selection ◽  
Selection For ◽  
Preweaning Period

Index selection for reduced backfat thickness and increased postweaning growth rate resulted in increased preweaning death losses due either directly or indirectly to the sow in the Yorkshire and Hampshire breeds. This resulted in a reduced percentage of piglets weaned in the Yorkshire breed. Key words: Swine, selection index, preweaning period, mortality, survival

scholarly journals COMPARISON OF TANDEM AND INDEX SELECTION IN THE MODIFIED PEDIGREE METHOD OF BREEDING SELF-POLLINATED SPECIES

1969 ◽  
Vol 49 (6) ◽  
pp. 773-781 ◽  
Author(s):  
J. Pesek ◽  
R. J. Baker
Keyword(s):  
Environmental Variability ◽  
Selection Index ◽  
Genetic Effects ◽  
Index Selection ◽  
Two Stage ◽  
Economic Values ◽  
Correlated Traits ◽  
Selection For

Two-stage tandem selection and index selection were simulated for the modified pedigree method of breeding self-pollinated crops. We assumed that two traits were negatively correlated due to repulsion linkages, and considered correlations ranging from 0.00 to −0.95 corresponding to linkage intensities of 0.50 to 0.05. Each trait was controlled by five different loci with equal genetic effects. Three levels of environmental variability were assumed. Economic values were set at 0.5, 1.0 and 1.5 for one trait and 1.0 for the other.Index selection was superior to tandem selection for all combinations of parameters simulated. The efficiency of tandem selection was increased substantially by selecting the most valuable trait first. The efficiency of index selection can be increased by more frequent estimation of selection index coefficients.We did not consider positively correlated traits.

scholarly journals Effects of selection for independent changes in two highly correlated body weight traits of mice

1977 ◽  
Vol 29 (2) ◽  
pp. 133-145 ◽  
Author(s):  
J. C. McCarthy ◽  
D. P. Doolittle
Keyword(s):  
Body Weight ◽  
Response Selection ◽  
The Other ◽  
Index Selection ◽  
Correlated Responses ◽  
Body Weights ◽  
Independent Culling ◽  
Selection For ◽  
Highly Correlated

SUMMARYMice were selected for high and low body weight at 5 and at 10 weeks of age. Selection was performed (1) separately for each trait, and (2) for various combinations of the two traits, using (a) independent culling levels and (b) restricted indices. Two-way selection for each trait separately gave large responses and correlated responses. Selection by independent culling levels intended to increase 5-week weight while restricting change in 10-week weight gave no demonstrable response; selection by culling levels intended to decrease 5-week weight while restricting change in 10-week weight resulted in decreases in body weights at both ages. Index selection, intended to change weight at one age while holding that at the other age constant, was generally successful. Observed responses did not conform very well with predicted responses for either index or culling levels selection. The significance of these observations in regard to the problem of selection involving restriction of traits is discussed.

AN APPLICATION OF INDEX SELECTION TO THE IMPROVEMENT OF SELF-POLLINATED SPECIES

1970 ◽  
Vol 50 (3) ◽  
pp. 267-276 ◽  
Author(s):  
J. PESEK ◽  
R. J. BAKER
Keyword(s):  
Triticum Aestivum ◽  
Selection Index ◽  
Triticum Aestivum L ◽  
Hybrid Population ◽  
Index Selection ◽  
Index Method ◽  
Quantitative Characters ◽  
Economic Weights ◽  
Selection For ◽  
Genotypic Effects

Results of a genetic study of four quantitative characters in a cross of two cultivars of Triticum aestivum L. em Thell. indicated that heritability of yield was lower than the heritabilities of maturity and height and that interactions between genotypic effects and year environmental effects were nonsignificant. The modified selection index method, based upon desired genetic gains rather than relative economic weights of traits, is explained in detail and applied to selection for maturity, height and yield from a hybrid population of wheat. The methods and problems of using index selection in self-pollinated species are discussed.

SINGLE-TRAIT AND ANTAGONISTIC INDEX SELECTION FOR LITTER SIZE AND BODY WEIGHT IN MICE

Genetics ◽  
1978 ◽  
Vol 88 (4) ◽  
pp. 781-811 ◽  
Author(s):  
E J Eisen
Keyword(s):  
Body Weight ◽  
Litter Size ◽  
Additive Genetic Variance ◽  
Selection Index ◽  
Genetic Correlations ◽  
Index Selection ◽  
Control Line ◽  
Female Performance ◽  
Vaginal Introitus ◽  
Perinatal Survival

ABSTRACT Individual selection based on female performance only was conducted in four lines of mice: L+ for increased litter size, W+ for increased 6-week body weight, L-W+ for a selection index aimed at decreasing litter size and increasing 6-week body weight and L+W- for a selection index aimed at increasing litter size and decreasing 6-week body weight. A fifth line (K) served as an unselected control. All litters were standardized to eight mice at one day of age. Expected heritability was based on twice the regression of offspring on dam (h  2  d), which contains additive genetic variance due to direct (α2Ao) and maternal (α2  Am) effects and their covariance (αAoAm). Responses and correlated responses were measured either deviated (method 1) or not deviated (method 2) from the control line. Realized heritabilities (h2  R) for litter size were 0.19 ± 0.04 (1) and 0.16 ± 0.03 (2), which were similar to h2  d of 0.17 ± 0.04. The h2  R for 6-week body weight of 0.55 ± 0.07 (1) and 0.44 ± 0.07 (2) agreed with h2  d of 0.42 ± 0.02. Realized genetic correlations (r*GR) between litter size and 6-week body weight calculated from the double-selection experiment were 0.52 ± 0.10 (1) and 0.52 ± 0.13 (2), which were not significantly different from the base population estimate of r*Gd = 0.63 ± 0.14. Divergence (L-W+ minus L+W-) in the antagonistic index selection lines was 0.21 ± 0.01 index units (I = 0.305 PW - 0.436 PL, where PW and PL are the phenotypic values for 6-week body weight and litter size, respectively.). The h2  R of index units of 0.14 ± 0.02 calculated from divergence agreed with h2  d of 0.14 ± 0.04. Divergences in litter size (-0.19 ± 0.07) and 6-week body weight (0.46 ± 0.10) were in the expected direction. Antagonistic index selection yielded about one-half the expected divergence in litter size, while divergence in 6-week body weight was only slightly less than expected. Realized genetic correlations indicated that litter size, 6-week body weight and index units each showed positive pleiotropy with 3-week body weight, postweaning gain and weight at vaginal introitus and negative pleiotropy with age at vaginal introitus. Sex ratio and several components of fitness (days from joining to parturition, percent fertile matings and percent perinatal survival) did not change significantly in the selected lines.

scholarly journals Genetic response to short-term index selection in females and mass selection in males of the Nigerian heavy local chicken ecotype

2020 ◽  
Vol 44 (2) ◽  
pp. 1-17
Author(s):  
C. C. Ogbu ◽  
C. C. Nwosu
Keyword(s):  
Body Weight ◽  
Genetic Gain ◽  
Egg Production ◽  
Index Selection ◽  
Mass Selection ◽  
Indigenous Chicken ◽  
Multiple Trait ◽  
Breeding Values ◽  
Expected Gain ◽  
Selection For

The study aimed to determine genetic gain in growth and egg production in the Nigerian indigenous chicken (NIC) subjected to multiple trait index selection for females and mass selection for males. The experimental birds (G generation) were generated from a reference 0 population of NIC and reared according to sire families from hatch. At point of lay, females were housed individually in laying cages for egg production. Hens were selected based on index scores calculated using an index of weighted breeding values constructed from own performance in body weight at first egg (BWFE), egg weight (EW) and egg production (EN), trait heritabilities and relative economic weights while cocks were selected based on own performance in body weight at 39 weeks of age (BW ). Selected parents were mated to 39 generate the G generation which in turn yielded the parents of the G generation. A control 1 2 population was used to measure environmental effects. Data were analyzed using the Restricted Maximum Likelihood (REML) computer programme. For hens, expected average direct genetic gain per generation was 12.58, 2.98g and 25.04g for EN, EW and BWFE, respectively while realized genetic gain was 2.19 and 1.59 for EN, 1.65 and 0.26g for EW, and -25.60 and 123.64g for BWFE for G and G generations, respectively. The corresponding 0 1 values for ratio of realized to expected genetic gains were 2.27 and 1.22, 3.15 and 0.24, and 0.95 and 2.21, respectively. Heritability (h2) ranged from 0.12 to 0.24 for EN, 0.34 to 0.43 for EW and 0.57 to 0.69 for BWFE, across the three generations. Similar improvements in BW 39 were observed in males with an average expected gain of 508.50g per generation. In conclusion, growth and egg production in the NIC can be improved using mass selection for cocks and index of weighted breeding values for hens.

scholarly journals Cow efficiency: modeling the biological and economic output of a Michigan beef herd

2020 ◽  
Vol 4 (3) ◽  
Author(s):  
Logan R Thompson ◽  
Matthew R Beck ◽  
Daniel D Buskirk ◽  
Jason E Rowntree ◽  
Melissa G S McKendree
Keyword(s):  
Body Weight ◽  
Body Size ◽  
Net Present Value ◽  
Biological Efficiency ◽  
Economic Returns ◽  
Present Value ◽  
Weaning Weight ◽  
Net Returns ◽  
Cow Calf ◽  
Lake City

Abstract In recent decades, beef cattle producers have selected cattle for biological traits (i.e., improved growth) to maximize revenue, leading to an increase in average cow body size. However, matching cow size to the production environment would allow producers to maximize productivity and economic returns per unit of land. This may help meet the goals of sustainable intensification, but environmental complexity and varying cow-calf production systems dictates a regional approach. The objective of this experiment was to examine the biological efficiency and economic returns of a Northern Michigan cow-calf system. We hypothesized that biological efficiency and economic returns would decrease with increasing cow body size. Data were collected from a Red Angus cow herd located at the Lake City AgBio Research Center in Lake City, MI from 2011 to 2018 on cow age, weight, and body condition score at weaning, and subsequent 205 d adjusted calf weaning weight (WW), sex, and yearling weight. Biological efficiency was defined as WW as a percentage of cow body weight (DBW). Enterprise budgeting techniques were used to calculate expected net returns from 2011 to 2018 after classifying cows into 11 BW tiers at 22.67 kg intervals beginning at 430.83 kg. Forward-looking net present value (NPV) was calculated using the same tier system, for a 10-yr production cycle with the baseline being a 200 d grazing season. Weaning weight increased with increasing DBW (P < 0.01), but the percentage of cow body weight weaned was reduced by −38.58 × Ln(DBW) (P < 0.01). This led to cows weaning 26.38 kg/ha more with every 100 kg drop in DBW. Expected net returns from 2011 to 2018 did not differ by DBW tier on a per cow basis but did on a per ha basis with a decrease in $10.27/ha with each increase in DBW tier (P < 0.01). Net present value was maximized in the baseline scenario at 453.51 kg DBW and decreased in value as DBW increased. These results suggest that for a Northern Midwestern cow-calf herd, comparatively lighter cows provide a higher economic value on a land basis.

Genetic analysis of fiber-dimension traits and combined selection for simultaneous improvement of growth and stiffness in lodgepole pine (Pinus contorta)

2019 ◽  
Vol 49 (5) ◽  
pp. 500-509 ◽  
Author(s):  
Haleh Hayatgheibi ◽  
Anders Fries ◽  
Johan Kroon ◽  
Harry X. Wu
Keyword(s):  
Pinus Contorta ◽  
Lodgepole Pine ◽  
Selection Index ◽  
Wood Quality ◽  
Genetic Correlations ◽  
Solid Wood ◽  
Fiber Wall ◽  
Wood Traits ◽  
Selection For ◽  
Combined Selection

Quantitative genetic variation of fiber-dimension traits and their relationship with diameter at breast height (DBH) and solid-wood traits (i.e., density and modulus of elasticity (MOE)) was investigated in lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.). A total of 823 increment cores were sampled from 207 half-sib families at two independent progeny trials, aged 34–35 years, located in northern Sweden. High-resolution pith-to-bark profiles were obtained for radial fiber width (RFW), tangential fiber width (TFW), fiber wall thickness (FWT), and fiber coarseness (FC) using SilviScan. Heritabilities ranged from 0.29 to 0.74, and inheritance increased with cambial maturity. Estimated age–age genetic correlations indicate that early selection between ages 5 and 8 years is highly efficient. Our results indicate that selection for a 1% increase in DBH or MOE incurs a negligible effect on fiber-dimension traits and maximum genetic gains are reached when DBH and MOE are considered jointly. Moreover, simultaneous improvement of growth and stiffness is achievable when a selection index with 7 to 10 economical weights for MOE relative to 1 for DBH is incorporated. However, the unfavorable relationship between solid-wood traits and pulp and paper related traits suggests that breeding strategies must be implemented to improve wood quality of lodgepole pine for multiple uses.

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