Topic
Control line
About: Control line is a research topic. Over the lifetime, 59 publications have been published within this topic receiving 1103 citations. The topic is also known as: U-Control.
Papers published on a yearly basis
Papers
TL;DR: It is concluded that selection for high or low FEC in Romney s has achieved an 11-fold difference between the divergent lines, and it will generally be necessary in a commercial environment to apply index selection for a combination of increased productivity, decreased FEC and possibly decreased dags, when potential candidates are recorded under conditions of nematode challenge.
Abstract: Divergent breeding lines of Romney sheep, selected as lambs for consistently high or low faecal worm egg count (FEC) following natural multi-species challenge by nematode parasites, were established in New Zealand at Wallaceville Animal Research Centre in 1979 and at Rotomahana Station in 1985. In 1988 the Rotomahana lines, including an unselected control line maintained under the same management conditions, were transferred to Tokanui Station where they remained for 4 years. In 1993 elite high and low FEC animals from Tokanui, along with the controls, were transferred to Wallaceville, where merged lines have since been managed together. Selection responses from the lines at Rotomahana and Tokanui, and from a further 5 years of divergent selection in the merged lines, are reported here. For the two most recent lamb crops (1996 and 1997 birth years), log-transformed FECs of the high and low lines were 1·27 and -1·46 phenotypic standard deviation units from the control. After back-transformation to the original scale, where the FEC for control line lambs averaged 1255 eggs per g, the means for the high and low lines were 3Ό5 and 0·27 times the control mean. Animal-model restricted maximum likelihood estimates of her it ability and repeatability for single-record FEC (following separate infections) were 0·28 (s.e. 0·02) and 0·42 (s.e. 0Ό1), respectively. Correlated responses in production traits include significantly decreased post-weaning weight gain and increased dags (breech soiling) in lambs, and decreased fleece weight in yearlings and ewes in the low FEC line, compared with those in the high line. However the low FEC line had proportionally 0·11 more lambs weaned per ewe mated than the high FEC line (F < 0·01). It is concluded firstly that selection for high or low FEC in Romney s has achieved an 11-fold difference between the divergent lines. Secondly, it will generally be necessary in a commercial environment to apply index selection for a combination of increased productivity, decreased FEC and possibly decreased dags, when potential candidates are recorded under conditions of nematode challenge.
127 citations
TL;DR: With the aim of improving general disease resistance, chickens were divergently selected for their antibody titers 5 d after immunization with sheep red blood cells for nine generations and realized heritability was .21 and .25 in the high and low lines, respectively.
Abstract: With the aim of improving general disease resistance, chickens were divergently selected for their antibody titers 5 d after immunization with sheep red blood cells for nine generations. Selected and control lines differed significantly for primary and secondary responses after three generations. Heritability of the antibody titer was estimated by REML fitting an animal model using a derivative-free algorithm. The heritability estimate using data on all lines simultaneously was .31. Realized heritability of the antibody titer in the selected lines was estimated by using either the phenotypic cumulative response as the deviation from the control line or the mean breeding values obtained with an animal model. Values from the two methods were consistent, giving a realized heritability of .21 and .25 in the high and low lines, respectively. The genetic trend was not linear and the response to selection tended to accelerate over generations.
106 citations
1 Jan 1985
TL;DR: Developmental stability was assessed among lines of rats selected for increased (up lines), decreased (down lines), and no body weight gain (controls) by the measurement of fluctuating asymmetry in 11 bilateral osteometric characters to test the hypothesis that developmental stability should be lower in both selection lines compared to the control line.
Abstract: Developmental stability was assessed among lines of rats selected for increased (up lines), decreased (down lines), and no body weight gain (controls) by the measurement of fluctuating asymmetry (FA) in 11 bilateral osteometric characters. This was done primarily to test the hypothesis that developmental stability should be lower (and thus FA higher) in both selection lines compared to the control line. FA values were obtained for all characters in each sex, line, and replicate (two each) within lines. Expressed as a proportion of the total variance, the FA values ranged from about 2% to over 50%, the average being 23%. FA for 3 of the 11 characters showed statistically significant differences among the lines, and in a multivariate analysis of variance, lines (but not sex or replicates) also showed overall significance (P less than 0.05). For the pooled sexes and replicates, seven of 11 FA values in the high line were greater than the comparable values in the control line (especially that for femur length), this conforming with theoretical expectations. Only one FA value in the down line was greater than that of the controls, however, and it was hypothesized that this was a consequence of the action of natural selection opposing artificial selection for decreased body weight gain.
49 citations
TL;DR: A long-established inbred strain of mice was divergently selected for body weight for 50 generations, suggesting a substantial contribution from the selection of mutations with large effects on the trait.
Abstract: A long-established inbred strain of mice was divergently selected for body weight for 50 generations. Selection of new mutations affecting the trait eventually led to a divergence of approximately three phenotypic standard deviations between the high and low lines. Heritability for body weight increased at a rate between 0.23% and 0.57% per generation from new mutations, depending on the genetic model assumed. About two-thirds of the selection response was in the upward direction. The response was episodic, suggesting a substantial contribution from the selection of mutations with large effects on the trait. A maximum likelihood procedure was used to estimate the number of factors contributing to the response using data from line crosses, with models of n equivalent gene effects (i.e., to estimate the Wright-Castle index), or n genes with variable effects. The results of the analysis of data from a cross between the selected high line and an unselected control line indicated that two major factors were involved, with the suggestion of an additional minor factor.
49 citations
TL;DR: Results indicated that one generation of inbreeding increased number of days required for eggs to hatch by 21%, but did not significantly influence spawn weight or hatchability score, however, inbred females produced more eggs/kg body weight than control females.
Abstract: Inbred channel catfish (Ictalurus punctatus) were produced from two generations of full-sib matings to study the effect of inbreeding on reproduction, growth and survival. A randomly mated control line was propagated from the same base population to be used for the evaluation of the inbred fish. First generation inbred (I1) and control (C1) lines comprised five full-sib families each. Second generation inbred (I2) and control (C2) lines were produced by mating each male catfish from the I1 or C1 line to two females in sequence, one from the I1 and one from the C1 line. The design also produced two reciprocal outcross lines to be compared to their contemporary inbred and control lines. The coefficient of inbreeding for the inbred line increased from 0.25 in generation 1 to 0.375 in generation 2. The inbreeding coefficient was zero for all other lines. The resulting fish were performance tested in two locations, Tifton, Georgia and Auburn, Alabama and no genotype-environment interactions occurred. Results indicated that one generation of inbreeding increased number of days required for eggs to hatch by 21%, but did not significantly influence spawn weight or hatchability score. However, inbred females produced more eggs/kg body weight than control females. Two generations of full-sib mating in Georgia did not depress weight when expressed as a deviation to random controls but was depressed 13-16% when expressed as a deviation to half-sib out-crosses. Second generation inbreds produced in Alabama exhibited a 19% depression for growth rate when compared to either random or half-sib outcross controls. Survival rates at various age intervals was not decreased by inbreeding. The amount of inbreeding depression varied among families and between sexes.
41 citations
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| Year | Papers |
|---|---|
| 2025 | 2 |
| 2024 | 5 |
| 2023 | 4 |
| 2022 | 11 |
| 2021 | 1 |
| 2020 | 2 |