Artificial selection for intrinsic aerobic endurance running capacity in rats

2001 ◽  
Vol 5 (1) ◽  
pp. 45-52 ◽  
Author(s):  
LAUREN GERARD KOCH ◽  
STEVEN L. BRITTON
Keyword(s):  
Body Weight ◽  
Artificial Selection ◽  
High Capacity ◽  
Founder Population ◽  
Endurance Running ◽  
Family Selection ◽  
High Line ◽  
Selection For ◽  
Coefficient Of Inbreeding

Artificial selection for intrinsic aerobic endurance running capacity was started using genetically heterogeneous N:NIH stock of rats as a founder population ( n = 168). Selection for low and high capacity was based upon distance run to exhaustion on a motorized treadmill using a velocity-ramped running protocol. The starting velocity was 10 m/min and was increased by 1 m/min every 2 min (slope was constant at 15°). At each generation, within-family selection was practiced using 13 families for both the low and high lines. A rotational breeding paradigm maintained the coefficient of inbreeding at less than 1% per generation. On average the founder population ran to exhaustion in 355 ± 11 m. Six generations of selection produced lines that differed in running capacity by 171%, with most of the change occurring in the high line. At generation 6 the low line ran 310 ± 8 m and the high line 839 ± 21 m at exhaustion. Selection for running capacity produced changes in body weight as a correlated trait. By generation 6, the low-line females were 20% heavier than the high-line females, and the low-line males were 16% heavier than the high-line males.

scholarly journals The limits to artificial selection for body weight in the mouse: IV. Sources of new genetic variance—irradiation and outcrossing

1967 ◽  
Vol 9 (1) ◽  
pp. 87-98 ◽  
Author(s):  
R. C. Roberts
Keyword(s):  
Body Weight ◽  
Artificial Selection ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Negative Results ◽  
Selection For ◽  
The Cross

1. Two methods are examined of introducing new genetic variance into a line of mice selected for high 6-week weight which, at its limit, displayed no additive genetic variance.2. The first method—irradiation—gave largely negative results. Any further gain under selection that was achieved could not be clearly distinguished from a possible environmental trend.3. The second method—outcrossing to an unselected strain and then selecting from the cross—resulted in a clear gain over the original limit, but nine generations were required even to recover the original limit.4. Various methods of transcending selection limits are evaluated in terms of their application to livestock improvement.

Selection for economic characters in Australian Merino sheep.

1954 ◽  
Vol 5 (2) ◽  
pp. 305 ◽  
Author(s):  
FHW Morley
Keyword(s):  
Body Weight ◽  
Least Squares ◽  
Expected Value ◽  
Merino Sheep ◽  
Random Deviation ◽  
Selection For ◽  
Australian Merino ◽  
Coefficient Of Inbreeding ◽  
Staple Length

The effect of inbreeding and parent-offspring regressions for some economic characters of Merino sheep were estimated by a least-squares procedure. The model was: Yi = a + b1X1i + b2X2i + ei ,where Yi and X1i represent the phenotype and coefficient of inbreeding of the ith sheep, X2i the phenotype of the dam of that sheep, and ei the random deviation of Y, from its expected value. Increased coefficients of inbreeding were accompanied by highly significant decreases in greasy and clean fleece weights, body weight, and fold score. No significant association was observed between inbreeding and yield, staple length, crimps per inch, or birthcoat grading. Increased inbreeding was associated with decreased survival. Significant correlations between X1 and X2 were demonstrated for fleece weights, staple length, body weight, and crimps per inch. The implications of these correlations are discussed. The parent-offspring regressions were all highly significant. Estimates of heritability were high for all characters studied. The importance of these findings on the effectiveness of selection for flock improvement is considered.

scholarly journals Two-way within-family and mass selection for 8-week body weight in different mouse populations

1984 ◽  
Vol 43 (2) ◽  
pp. 191-200 ◽  
Author(s):  
Ines von Butler ◽  
Henning Willeke ◽  
Franz Pirchner
Keyword(s):  
Body Weight ◽  
Inbred Strains ◽  
Selection Response ◽  
Mass Selection ◽  
Individual Selection ◽  
Family Selection ◽  
Body Weights ◽  
Selection For ◽  
Size At Birth ◽  
Better Than

SUMMARYTwo mouse populations, randombred albino mice and a cross of four inbred strains, were divergently selected for high (H8) and low (L8) 8-week body weight over 18 generations using within-family and individual selection. The crossbreds showed asymmetry of selection response and realized heritabilities (H8 0·29 ± 0·01; L8 0·17 ± 0·01). In the randombred population realized heritabilities were symmetrical (H8 0·23 ± 0·01; L8 0·22 ± 0·02). Over the first nine generations individual selection was nearly 40 per cent better than within-family selection, as was expected from the full sib correlation in both populations. As selection progressed, within-family selection reached 82% and 61% of the responses obtained with individual selection in the crossbreds and randombred respectively. Correlated responses for 3-week (weaning) and 5-week body weights agreed with observations made on direct responses, but selection for L8 did not reduce weaning weight. Selection for L8 decreased and selection for H8 increased first litter size at birth. However, mass-selected L8-pairs had a higher life-reproduction and life-span than H8-pairs.

SCALING EFFECTS AND THE INHERITANCE OF JUVENILE BODY WEIGHT IN CHICKENS

1970 ◽  
Vol 12 (4) ◽  
pp. 724-727 ◽  
Author(s):  
I. F. Carte ◽  
P. B. Siegel
Keyword(s):  
Body Weight ◽  
High Weight ◽  
Scaling Effects ◽  
High Line ◽  
Low Weight ◽  
Selection For

Data are presented for 10 generations of selection for high and low body weight at 8 weeks of age. The response of males was greater than that of females in the high weight line, but not in the low weight line. The asymmetrical response of sexes in the high weight line was eliminated by adjustment for scaling effects. Although heritabilities were greater in the high line than in the low line, they were essentially equal for both sexes within a line.

scholarly journals Vascularity of myocardium and gastrocnemius muscle in rats selectively bred for endurance running capacity

2013 ◽  
Vol 45 (3) ◽  
pp. 119-125
Author(s):  
Patricia E. Beighley ◽  
Mair Zamir ◽  
Robert J. Wentz ◽  
Lauren G. Koch ◽  
Steven L. Britton ◽  
...  
Keyword(s):  
Gastrocnemius Muscle ◽  
Contractile Function ◽  
High Capacity ◽  
Treadmill Running ◽  
Micro Ct ◽  
Endurance Running ◽  
Selection For ◽  
Gastrocnemius Muscles ◽  
Myocardial Muscle ◽  
Vascular Branching

We tested the hypothesis that changes in the arteriolar branching architecture contributed to increased running capacity of rats subjected to two-way artificial selection for intrinsic aerobic endurance treadmill running capacity resulting in strains of low-capacity and high-capacity endurance rats. Hearts and gastrocnemius muscles were harvested from each strain, and the microvasculature's branching geometry measured from micro-CT images. The vascular branching geometry of the hearts and skeletal muscle from the high capacity was indistinguishable from low-capacity rats. Our hypothesis was not supported. Neither remodeling nor an increase in arteriolar microvasculature branching appears to play a role in the enhanced performance of the high capacity rats. We are led to speculate that endothelial tolerance for shear stress and/or increased coupling of myocardial muscle fiber metabolic-to-contractile function is increased in the high-capacity runner strain to the effect of allowing either higher flow rate per unit volume of muscle or more efficient use of oxygen and nutrients in the high-capacity endurance rats.

scholarly journals Intestinal Microbiota and Host Cooperate for Adaptation as a Hologenome

mSystems ◽  
2022 ◽  
Author(s):  
Hao Zhou ◽  
Lingyu Yang ◽  
Jinmei Ding ◽  
Ronghua Dai ◽  
Chuan He ◽  
...  
Keyword(s):  
Body Weight ◽  
Intestinal Microbiota ◽  
Founder Population ◽  
Term Selection ◽  
Common Founder ◽  
Selection For

The hologenome concept has broadened our perspectives for studying host-microbe coevolution. The multiomic analyses reported here involved two lines of chickens, from a common founder population, that had undergone long-term selection for high (HWS) or low (LWS) 56-day body weight.

scholarly journals The limits to artificial selection for body weight in the mouse II. The Genetic Nature of the Limits

1966 ◽  
Vol 8 (3) ◽  
pp. 361-375 ◽  
Author(s):  
R. C. Roberts
Keyword(s):  
Body Weight ◽  
Natural Selection ◽  
Artificial Selection ◽  
Sharp Increase ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Base Population ◽  
Relaxed Selection ◽  
Genetic Nature ◽  
Selection For

1. The effects of long-continued selection for body weight in two lines of mice, one large and one small, are described.2. The large line showed a sharp increase in weight after remaining at an apparent limit for twenty generations. A rare combinational event is suggested as the most likely explanation.3. Reversed and relaxed selection from the large line at the limit failed to yield any response. This indicates that effectively, the additive genetic variance in this line had been exhausted.4. In contrast, the small line at the limit regressed slightly towards the base population when selection was relaxed. Reversed selection yielded a ready response until a new limit was apparently reached. Loci affecting body weight in this line had therefore not been fixed by selection.5. Natural selection, operating on viability between conception and the time when the selection was made, appears to explain best the lack of fixation in the small line.6. Attention is drawn to the necessity of more experimental work to elucidate the genetic nature of the limits to artificial selection.

Circadian characteristics of Djungarian hamsters: effects of photoperiodic pretreatment and artificial selection

1991 ◽  
Vol 261 (3) ◽  
pp. R670-R676 ◽  
Author(s):  
W. Puchalski ◽  
G. R. Lynch
Keyword(s):  
Phase Angle ◽  
Artificial Selection ◽  
Phase Response Curve ◽  
Circadian Rhythmicity ◽  
Activity Duration ◽  
High Line ◽  
Free Running ◽  
Selection For ◽  
Free Running Period ◽  
Short Days

Bidirectional artificial selection for (High Line) and against (Low Line) photoresponsiveness altered the percent of photoresponsive hamsters within lines and affected circadian function of hamsters identical in photoresponsiveness. For example, free-running period was shorter in responsive relative to nonresponsive hamsters. Between-line differences for responders and nonresponders were also found: hamsters from the High Line had a shorter free-running period relative to Low Line hamsters. However, phase angle of entrainment to long and short days was not affected. In general, expression of circadian rhythmicity was extraordinarily inflexible in photononresponsive hamsters from both lines: 1) phase angle of entrainment to lights on was similar under short and long day; 2) activity duration was similar under long and short days, although some decompression occurred in constant dark; 3) aftereffects on the free-running period were absent; and 4) amplitude of the phase-response curve was small (+/- 1 h) and present only at circadian times 10-24. We propose that selection for or against photoresponsiveness may have affected the interaction of component oscillators underlying circadian rhythmicity.

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