SELECTION IN HEREFORD CATTLE I. SELECTION INTENSITY, GENERATION INTERVAL AND INDEXES IN RETROSPECT

Selection intensity and generation interval were evaluated in a Hereford cattle herd of 14 inbred lines and 14 linecross groups corresponding to the lines of inbred sire at the San Juan Basin Research Centre, Hesperus, Colorado. Selection indexes practised were calculated in retrospect. The records analysed were weaning weight and postweaning traits in males and females collected from 1946 through 1973. Analyses were performed by line for the inbreds and pooled analyses for the inbred and linecross populations. From records of 1,239 calves weaned, age of sire averaged 3.75 years compared with 4.52 years for age of dam, showing faster generation turnover for sires than for dams. Generation interval determined 98 actual age of midparent was 4.13 years.Selection applied, evaluated as annual selection differentials within inbred lines and then pooled over all lines, averaged .55 standard deviations per generation for sires for weaning weight. Selection of females was much less. Midparent selection differential amounted to .33 standard deviations per generation. Pooled standardized selection differentials per generation over all lines for sires were .49, .46, 40, -.20, -.10, and .69, respectively, for initial weight, final weight, feed consumption, unadjusted feed efficiency, adjusted feed efficiency, and average daily gain. Selection of females for postweaning traits was not intense. Selection Indexes actually practiced in retrospect were: for sires, IS = .4661(WW) -.0092(FE) + .6126(ADG); for inbred dams, ID = .1824(WW) -.0284 (12W) + .0736 (18W) - 1097 (SPW) -.1097 (FAW); for linecross dams, ID= .2693 (WW) - 2960 (12W) + .0147 (18W) + 1185 (SPW) -.0354 (FAW). The corresponding index selection differentials were .818, 203, and .209. Sire index selection differentials represent about 79 percent of the total selection differentials.

Download Full-text

A note on selection differential and generation length when generations overlap

Animal Science ◽

10.1017/s0003356100039271 ◽

1977 ◽

Vol 24 (1) ◽

pp. 109-112 ◽

Cited By ~ 31

Author(s):

J. W. James

Keyword(s):

Age Groups ◽

Parental Age ◽

Selection Differential ◽

Generation Interval ◽

Generation Length ◽

The Mean ◽

Selection Differentials ◽

Selection Of

SUMMARYThe generation interval may be defined as the mean age of parents of all progeny born, or as the mean age of parents of only those progeny destined to be selected as replacements. If the mean age of parents of replacements is used, selection differentials must be calculated within parental age groups. If the mean age of parents of all progeny born is used, the selection differential contains a component due to disproportionate selection of replacements from different parental age groups.

Download Full-text

Comparison of non-parametric indexes to select soybean genotypes obtained by recurrent selection

Semina Ciências Agrárias ◽

10.5433/1679-0359.2019v40n5p1761 ◽

2019 ◽

Vol 40 (5) ◽

pp. 1761

Author(s):

Gustavo Henrique Freiria ◽

Luiz Júnior Perini ◽

Douglas Mariani Zeffa ◽

Paulo Sérgio Novais ◽

Wilmar Ferreira Lima ◽

...

Keyword(s):

Recurrent Selection ◽

Selection Index ◽

Inbred Lines ◽

Cultivar Selection ◽

Days To Maturity ◽

Soybean Genotypes ◽

Superior Genotypes ◽

Selection Indexes ◽

Coefficient Of Coincidence ◽

Selection Of

In the final steps of a breeding program, it is necessary to evaluate several traits, which makes it difficult to select the superior genotypes. This study aimed to compare nonlinear indexes in the selection of superior soybean inbred lines obtained by recurrent selection. The experiment was carried out in Londrina, Paraná State, Brazil. During the 2010/11 and 2011/12 seasons, 67 soybean inbred lines and two commercial controls (BMX Potência RR and NK 7059 RR) were evaluated. The experimental design was a randomized complete block with three replicates. The evaluated traits were: days to maturity, agronomic value, lodging, first pod insertion height, and grain yield. A combined analysis of variance for seasons was performed and the sum of ranks index, ideotype distance index, and cultivars selection index were applied. All traits were significant for the genotypic source of variation and showed complex genotype × environment interactions. The selection indexes were consistent with each other. The ideotype and cultivar selection index showed higher concordance on indication of 15 superior inbred lines with a coefficient of coincidence of 80%. The inbred lines SR-03, SR-12, SR-22, SR-41, SR-49, SR-55, SR-61, and SR-62 were indicated for all indexes and are therefore considered superior to other inbred lines.

Download Full-text

Selection intensity for milk yield in 1970—1977 in the Finnish Ayrshire

Agricultural and Food Science ◽

10.23986/afsci.71991 ◽

1978 ◽

Vol 50 (6) ◽

pp. 445-454

Author(s):

U. B. Lindström

Keyword(s):

Milk Yield ◽

Genetic Gain ◽

Genetic Change ◽

Selection Intensity ◽

Genetic Progress ◽

Generation Interval ◽

Ayrshire Breed ◽

The Mean ◽

Selection Differentials

Selection differentials for sires and dams of bulls taken into AI use in 1970—1977, as well as for sires used in AI, were combined with an estimate of the quality of dams of female replacements to calculate the (predicted) genetic change in milk yield in the Ayrshire breed. In the period the average annual genetic gain was 0.97 % of the mean yield, in the last three years it was c. 1.1 %. The average generation interval was 6.8 years; 8.7 years for the bull sires, 7.4 years for the bull dams and 6.4 years for the cow sires. The bull sires accounted for 42 %, the bull dams for 37 % and the cow sires for only 12% of the total genetic gain. A more rational use of progeny tested and young bulls, combined with a reduction of the generation interval of 15 %, could easily have increased the genetic progress by 20 %.

Download Full-text

The effect of correction factors on response to selection in beef cattle

Animal Science ◽

10.1017/s0003356100023990 ◽

1980 ◽

Vol 30 (2) ◽

pp. 211-216 ◽

Cited By ~ 1

Author(s):

L. P. Jones ◽

I. R. Hopkins

Keyword(s):

Growth Rate ◽

Age Groups ◽

Correction Factors ◽

Response To Selection ◽

Weaning Weight ◽

Selection For ◽

Rate Selection ◽

Genetic Responses ◽

Selection Differentials ◽

Selection Of

ABSTRACTProgeny of younger dams grow more slowly than those of older dams. When the environmental effects of dam age are not allowed for in selection for growth rate, selection differentials and genetic responses to selection are reduced.In a model herd, with cows aged 2 to 8 years, it was found that neglecting the dam age effects reduced genetic gains by about 15% when selection is for weaning weight, and by 11 to 7 % when selection is at an age of 12 to 20 months. Much of the reduction occurs because of the selection of higher proportions from genetically inferior groups.If genetic differences among dam age groups are small the reduction is only 7% at weaning and less at older ages. The effect of ignoring calf age was also estimated. It was found that if calves born within a period of 33 days were compared and calf age was neglected, the response to selection for weaning weight would be reduced by about 6%.

Download Full-text

Selection indexes for bulls of beef cattle

Czech Journal of Animal Science ◽

10.17221/3941-cjas ◽

2011 ◽

Vol 51 (No. 7) ◽

pp. 285-298 ◽

Cited By ~ 5

Author(s):

P. Šafus ◽

J. Přibyl ◽

Z. Veselá ◽

L. Vostrý ◽

M. Štípková ◽

...

Keyword(s):

Maternal Effect ◽

Performance Testing ◽

Direct Effects ◽

Weaning Weight ◽

Breeding Values ◽

Breeding Objective ◽

Beef Herd ◽

Selection Indexes ◽

Daily Gain ◽

Selection Of

Three selection indexes were constructed for bulls of beef cattle: IM for terminal crossing (in dairy herds), IZ for the selection of foundation sires for beef herd and IS for the selection of bulls for beef herd. Each index was constructed in five variants that differed in the number of used traits from the most important ones to all traits with known breeding values. The sources of information were breeding values routinely calculated in performance testing – 10 breeding values for direct and maternal effects for easy calving and growth, breeding value for daily gain of bulls at performance-testing stations and 10 breeding values for the type traits of young animals. The reliability of partial breeding values that enter into the indexes ranged from 11% to 36%. Reliability influences subsequent accuracy of index selection for total genotype that is in the range of 30% to 46%. The discounting of economic values (0% or 10%) did not influence the selection indexes significantly. Index selection was expressed almost exclusively in genetic gain of direct effects while maternal effects were of only small importance in the breeding objective. Direct effects for daily gain until weaning and after weaning are of the highest importance in the breeding objective, accounting for 90% to 96% of the total selection effect. The most important information sources in selection indexes are direct effect of weaning weight (importance of approximately 74% to 95%) and maternal effect of weaning weight (importance of approximately 5% to 7%). The inclusion of daily gain of bulls at performance-testing stations with the importance of about 16% in the index decreased the importance of weaning weight. Selection can be aimed at these main traits – calving ease (direct and maternal effect) and weight at 210 days (direct and maternal effect) only because the importance of the other traits in the index is very low.  

Download Full-text

Long-term comparison between index selection and optimal independent culling in plant breeding programs with genomic prediction

PLoS ONE ◽

10.1371/journal.pone.0235554 ◽

2021 ◽

Vol 16 (5) ◽

pp. e0235554

Author(s):

Lorena G. Batista ◽

Robert Chris Gaynor ◽

Gabriel R. A. Margarido ◽

Tim Byrne ◽

Peter Amer ◽

...

Keyword(s):

Recurrent Selection ◽

Genetic Correlations ◽

Economic Importance ◽

Index Selection ◽

Selection Intensity ◽

Crop Breeding ◽

Breeding Programs ◽

Independent Culling ◽

Selection Of

In the context of genomic selection, we evaluated and compared breeding programs using either index selection or independent culling for recurrent selection of parents. We simulated a clonally propagated crop breeding program for 20 cycles using either independent culling or an economic index with two unfavourably correlated traits under selection. Cycle time from crossing to selection of parents was kept the same for both strategies. Both methods led to increasingly unfavourable genetic correlations between traits and, compared to independent culling, index selection led to larger changes in the genetic correlation between the two traits. When linkage disequilibrium was not considered, the two methods had similar losses of genetic diversity. Two independent culling approaches were evaluated, one using optimal culling levels and one using the same selection intensity for both traits. Optimal culling levels outperformed the same selection intensity even when traits had the same economic importance. Therefore, accurately estimating optimal culling levels is essential for maximizing gains when independent culling is performed. Once optimal culling levels are achieved, independent culling and index selection lead to comparable genetic gains.

Download Full-text