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Renewed Selection For Heat Loss In Mice: Direct Responses And Correlated Responses In Feed Intake, Body Weight, Litter Size, And Conception Rate, J. M. Mcdonald, Merlyn K. Nielsen
Renewed Selection For Heat Loss In Mice: Direct Responses And Correlated Responses In Feed Intake, Body Weight, Litter Size, And Conception Rate, J. M. Mcdonald, Merlyn K. Nielsen
Department of Animal Science: Faculty Publications
Divergent selection in mice was renewed in 3 independent replicates for high (MH) and low (ML) heat loss. An unselected control (MC) was maintained in all replicates. Heat loss was measured for individual male mice for 15 h, overnight in direct calorimeters. After 16 initial generations of selection followed by 26 generations of relaxed selection, divergent selection resumed for 9 generations. The realized selection applied was very close to the maximum possible selection according to the criteria and protocol. Selection differentials were greater for high than for low selection due to greater variation in the MH line. When corrected for …
Comparison Of Feed Energy Costs Of Maintenance, Lean Deposition, And Fat Deposition In Three Lines Of Mice Selected For Heat Loss, D. L. Eggert, Merlyn K. Nielsen
Comparison Of Feed Energy Costs Of Maintenance, Lean Deposition, And Fat Deposition In Three Lines Of Mice Selected For Heat Loss, D. L. Eggert, Merlyn K. Nielsen
Department of Animal Science: Faculty Publications
Three replications of mouse selection populations for high heat loss (MH), low heat loss (ML), and a nonselected control (MC) were used to estimate the feed energy costs of maintenance and gain and to test whether selection had changed these costs. At 21 and 49 d of age, mice were weighed and subjected to dual x-ray densitometry measurement for prediction of body composition. At 21 d, mice were randomly assigned to an ad libitum, an 80% of ad libitum, or a 60% of ad libitum feeding group for 28-d collection of individual feed intake. Data were analyzed using 3 approaches. …
Performance Of Mouse Lines Divergently Selected For Heat Loss When Exposed To Different Environmental Temperatures. I. Reproductive Performance, Pup Survival, And Metabolic Hormones, P. M. Kgwatalala, J. L. Deroin, Merlyn K. Nielsen
Performance Of Mouse Lines Divergently Selected For Heat Loss When Exposed To Different Environmental Temperatures. I. Reproductive Performance, Pup Survival, And Metabolic Hormones, P. M. Kgwatalala, J. L. Deroin, Merlyn K. Nielsen
Department of Animal Science: Faculty Publications
Mouse populations differing in metabolic rate have been developed through selection for high (MH) and low (ML) heat loss, along with the unselected controls (MC). Objectives of the study were to compare the MH, ML, and MC lines for reproductive performance, pup survival, and metabolic hormones when reared at 12, 22, and 31°C, and to search for line × environment interactions. Conception and litter size were recorded on the parent generation mice introduced to the environments at 11 wk of age and bred after a 3-wk acclimatization period. Survival of pups (pre-weaning to 3 wk; post-weaning from 3 to 9 …
Performance Of Mouse Lines Divergently Selected For Heat Loss When Exposed To Different Environmental Temperatures. Ii. Feed Intake, Growth, Fatness, And Body Organs, P. M. Kgwatalala, Merlyn K. Nielsen
Performance Of Mouse Lines Divergently Selected For Heat Loss When Exposed To Different Environmental Temperatures. Ii. Feed Intake, Growth, Fatness, And Body Organs, P. M. Kgwatalala, Merlyn K. Nielsen
Department of Animal Science: Faculty Publications
Mouse populations differing in metabolic rate have been developed through selection for high (MH) and low (ML) heat loss, along with the unselected controls (MC). Objectives of the study were to compare the MH, ML, and MC lines for feed intake, growth, body fatness, and organ weights when reared at 12, 22, and 31°C, and investigate potential line × environment interactions. Feed intake was recorded weekly from 3 to 9 wk of age, and BW at 3, 6, and 9 wk of age. Body fat percent and organ weights were measured at 9 wk of age. No line × environment …
Selection For Maternal Behavior In Mice—Direct And Correlated Responses, Chung-Feng Chiang, Rodger K. Johnson, Merlyn K. Nielsen
Selection For Maternal Behavior In Mice—Direct And Correlated Responses, Chung-Feng Chiang, Rodger K. Johnson, Merlyn K. Nielsen
Department of Animal Science: Faculty Publications
Three generations of divergent selection for a maternal care index (MCI) in mice were practiced in each of three replicates. MCI was recorded for 29–32 dams and litters in each replicate/line subclass. Pups of the top (or bottom) 6– 10 dams in each replicate, depending on number of females in the litters, were selected in high (H) and low (L) MCI lines. At birth, litters with more than 10 pups were standardized to 10 pups whereas litters with no more than 10 pups remained intact. On day 4, 8, 12, and 16 of lactation, time budgets during a 30-min session …
Maternal Behavior In Mice Selected For Large Litter Size, Chung-Feng Chiang, Rodger . K. Johnson, Merlyn K. Nielsen
Maternal Behavior In Mice Selected For Large Litter Size, Chung-Feng Chiang, Rodger . K. Johnson, Merlyn K. Nielsen
Department of Animal Science: Faculty Publications
A total of 96 lactating mice and their pups from each of three replications of lines selected 21 generations for increased litter size (LS) followed by 23–25 generations of random selection and contemporary unselected control lines (LC) were characterized for maternal behavior. Sixteen dams and their pups from each replication of LS and LC lines were sampled. Litter sizes at birth for LS versus LC in the first, second, and third replicates were 17.3 versus 13.2, 15.9 versus 13.1, and 12.3 versus 10.6 pups, respectively, with LS dams averaging 2.87 ± .70 pups more. One-half of the litters were standardized …
Divergent Selection For Heat Loss In Mice: Ii. Correlated Responses In Feed Intake, Body Mass, Body Composition, And Number Born Through Fifteen Generations, Merlyn K. Nielsen, B. A. Freking, L. D. Jones, S. M. Nelson, T. L. Vorderstrasse, B. A. Hussey
Divergent Selection For Heat Loss In Mice: Ii. Correlated Responses In Feed Intake, Body Mass, Body Composition, And Number Born Through Fifteen Generations, Merlyn K. Nielsen, B. A. Freking, L. D. Jones, S. M. Nelson, T. L. Vorderstrasse, B. A. Hussey
Department of Animal Science: Faculty Publications
Divergent selection for heat loss (kcal•kg-.75•d-1) , measured in 9- to 11-wk-old male mice, was conducted for 15 generations. Selection for high (MH) and low (ML) heat loss and unselected control (MC) occurred in each of three replicates for a total of nine unique lines. Feed intake in males was measured during Generations 9 through 15. Body mass at commencement of mating in females and at time of measurement of heat loss in males was recorded. Body fat percentage at 12 wk for animals of Generations 6, 10, and 14 was predicted as a function of …
Divergent Selection For Heat Loss In Mice: I. Selection Applied And Direct Response Through Fifteen Generations, Merlyn K. Nielsen, L. D. Jones, B. A. Freking, J. A. Deshazer
Divergent Selection For Heat Loss In Mice: I. Selection Applied And Direct Response Through Fifteen Generations, Merlyn K. Nielsen, L. D. Jones, B. A. Freking, J. A. Deshazer
Department of Animal Science: Faculty Publications
Divergent selection for heat production/ loss (kcal•kg-.75•d-1) , measured in 9- to 11-wk-old male mice, was conducted for 15 generations. Heat loss was measured for 15 h on individual animals placed overnight in direct, gradient-layer calorimeters. Selection for high (MH) and low (ML) heat loss and unselected control (MC) occurred in each of three replicates for a total of nine unique lines. Repeatability of the heat loss measurement was .45 and the CV was 10.5%. Cumulative realized selection differentials, averaged for the three replicates, were 145.1 and -105.0 (kcal•kg-.75•d-1) and ranged from …
A Simulation Model Including Ovulation Rate, Potential Embryonic Viability, And Uterine Capacity To Explain Litter Size In Mice: Ii. Responses To Alternative Criteria Of Selection, E. L. De A. Ribeiro, Merlyn K. Nielsen, Kreg A. Leymaster, Gary Bennett
A Simulation Model Including Ovulation Rate, Potential Embryonic Viability, And Uterine Capacity To Explain Litter Size In Mice: Ii. Responses To Alternative Criteria Of Selection, E. L. De A. Ribeiro, Merlyn K. Nielsen, Kreg A. Leymaster, Gary Bennett
Department of Animal Science: Faculty Publications
Direct selection for litter size was compared with selection for ovulation rate, ova success, or uterine capacity and for indexes of ovulation rate with ova success or uterine capacity. Selection was simulated for 10 generations in a mouse population based on a model integrating ovulation rate, potential embryonic viability, and uterine capacity. Two indexes including ovulation rate (OR) and ova success (OS) were I = .291 x OR + 2.19 x OS and I = .165 x OR + .736 x OS. Heritabilities for ovulation rate and ova success, assumed in the simulation and to derive the indexes, were .25 …
A Simulation Model Including Ovulation Rate, Potential Embryonic Viability, And Uterine Capacity To Explain Litter Size In Mice: I. Model Development And Implementation, E. L. De A. Ribeiro, Merlyn K. Nielsen, Gary Bennett, Kreg A. Leymaster
A Simulation Model Including Ovulation Rate, Potential Embryonic Viability, And Uterine Capacity To Explain Litter Size In Mice: I. Model Development And Implementation, E. L. De A. Ribeiro, Merlyn K. Nielsen, Gary Bennett, Kreg A. Leymaster
Department of Animal Science: Faculty Publications
Litter size in mice was studied using a model including ovulation rate, potential embryonic viability, and uterine capacity. Simulated results were compared with experimental results from a selection experiment with mice. The four criteria of selection were selection on number born (LS), selection on an index of ovulation rate and ova success (IX), selection on number born to unilaterally ovariectomized females (UT), and unselected control (LC). Comparisons were made to statistics of the base generation and to responses after 13 generations of selection. Phenotypic and genetic statistics for uterine capacity were generated so that simulations produced the experimental means, standard …
Embryonal Survival To 6 Days In Mice Selected On Different Criteria For Litter Size, E. L. De A. Ribeiro, M. A. J. Van Engelen, Merlyn K. Nielsen
Embryonal Survival To 6 Days In Mice Selected On Different Criteria For Litter Size, E. L. De A. Ribeiro, M. A. J. Van Engelen, Merlyn K. Nielsen
Department of Animal Science: Faculty Publications
Embryonal survival was compared in mice resulting from four criteria of selection: LS = selection on number born; IX = selection on an index of ovulation rate and ova success; UT = selection on number born to unilaterally ovariectomized females; and LC = unselected control. Selection occurred for 21 generations with three replicates of the four criteria; thereafter, relaxed selection was practiced. The evaluation was performed using mice of two replicates at Generation 35 and one replicate at Generation 36. Data on a total of 289 female mice were recorded. Females, at an average age of 9 wk, were mated …
Estimates Of Heritabilities And Genetic And Environmental Correlations For Left- And Right-Side Uterine Capacity And Ovulation Rate In Mice, Merlyn K. Nielsen, Y. L. Kochera Kirby, A. C. Clutter
Estimates Of Heritabilities And Genetic And Environmental Correlations For Left- And Right-Side Uterine Capacity And Ovulation Rate In Mice, Merlyn K. Nielsen, Y. L. Kochera Kirby, A. C. Clutter
Department of Animal Science: Faculty Publications
Heritabilities for and genetic and environmental correlations between uterine capacity, ovulation rate, and body mass (BM) were estimated in mice. Uterine capacity was defined as the number of fetuses (LUC or RUC for left or right side) in one uterine horn for unilaterally ovariectomized females. Ovulation rate (corpora lutea, LCL or RCL for left or right ovary) was measured on the remaining single ovary in these same females. Data on 1,931 mice from four selection populations were used. Left ovulation rate and LUC were measured on 958 animals, and RCL and RUC of another 972 animals were recorded. Genetic and …
Uterine Mass And Uterine Blood Volume In Mice Selected 21 Generations For Alternative Criteria To Increase Litter Size, Merlyn K. Nielsen, R. J. Kittok, Y. L. Kochera Kirby
Uterine Mass And Uterine Blood Volume In Mice Selected 21 Generations For Alternative Criteria To Increase Litter Size, Merlyn K. Nielsen, R. J. Kittok, Y. L. Kochera Kirby
Department of Animal Science: Faculty Publications
Lines of mice, selected for 21 generations using alternative criteria to increase litter size, were evaluated for uterine mass and uterine blood volume to help explain differences in uterine capacity. For this study, mice were sampled from Generation 27, the sixth generation after relaxation of selection. Mice came from all four criteria of selection (LS = selection on number born to unaltered females; M = selection on an index of ovulation rate and ova success; UT = selection on uterine capacity; and LC = unselected control) in each of three replicates (a total of 12 lines). Measurement was at one …
Differences In Pup Birth Weight, Pup Variability Within Litters, And Dam Weight Of Mice Selected For Alternative Criteria To Increase Litter Size, M. A. J/ Van Engelen, Merlyn K. Nielsen, E. L. De A. Ribeiro
Differences In Pup Birth Weight, Pup Variability Within Litters, And Dam Weight Of Mice Selected For Alternative Criteria To Increase Litter Size, M. A. J/ Van Engelen, Merlyn K. Nielsen, E. L. De A. Ribeiro
Department of Animal Science: Faculty Publications
Selection for litter size had been practiced for 21 generations and relaxed selection for 13 generations in mice. Three replicates were used with four selection criteria: index of components (ovulation rate and ova success), uterine capacity, litter size, and an unselected control. Especially with selection for litter size and the index relative to the control, number of pups born had increased, and differences also occurred in mating weight. Dams of the three replicates and their litters were used to evaluate the effects of accumulated selection on pup birth weight, variability in weight of littermates, and dam's weight at mating and …
Uterine Capacity And Ovulation Rate In Mice Selected 21 Generations On Alternative Criteria To Increase Litter Size, A. C. Clutter, Y. Kochera Kirby, Merlyn K. Nielsen
Uterine Capacity And Ovulation Rate In Mice Selected 21 Generations On Alternative Criteria To Increase Litter Size, A. C. Clutter, Y. Kochera Kirby, Merlyn K. Nielsen
Department of Animal Science: Faculty Publications
After 21 generations of selection for alternative criteria to change litter size in mice, responses in uterine capacity and ovulation rate were evaluated. Females from Generations 22 and 23 were sampled from 12 lines, representing three replicates of four selection criteria: LS = direct selection on litter size; M = selection on an index of ovulation rate and the proportion of ova shed that resulted in fully formed offspring; UT = selection on uterine capacity measured as litter size from females unilaterally ovariectomized at 4 wk of age; and LC = unselected control. All females in the present evaluation (a …
Alternative Methods Of Selection For Litter Size In Mice: Iii. Response To 21 Generations Of Selection, Yvonne Kochera Kirby, Merlyn K. Nielsen
Alternative Methods Of Selection For Litter Size In Mice: Iii. Response To 21 Generations Of Selection, Yvonne Kochera Kirby, Merlyn K. Nielsen
Department of Animal Science: Faculty Publications
Alternative methods of selection to increase litter size in mice have been practiced for 21 generations followed by six generations of relaxed selection. Three replicates were used with four selection criteria: index of components (IX: I = 1.21 x total ovulation rate + 9.05 x ova success), uterine capacity (UT), litter size (LS), and an unselected control (LC). In IX, ovulation rate and ova success were measured by number of corpora lutea and number of pups born/number of corpora lutea, respectively. In UT, uterine capacity was measured and defined as number of pups born to unilaterally ovariectomized (right ovary excised) …
Genetic Variation Liver Mass, Body Mass, And Liver:Body Mass In Mice, L. D. Jones, Merlyn K. Nielsen, R. Britton
Genetic Variation Liver Mass, Body Mass, And Liver:Body Mass In Mice, L. D. Jones, Merlyn K. Nielsen, R. Britton
Department of Animal Science: Faculty Publications
Genetic variation for liver mass (LM), body mass (BM), and 1iver:body mass (LM/ BM) was examined for outbred populations of laboratory mice. Liver mass and body mass data were collected on 170 pureline sires at 12 wk of age, representing four outbred stocks of laboratory mice; 523 of their male and female two-way cross progeny at 9 or 12 wk; and 214 four-way-cross' offspring at 12, 14, or 16 wk. Genetic differences for LM, BM, and LM/BM were found among the base sire lines and between two-way crosses. Heritabilities and genetic correlations for LM, BM, LM/BM, and LM/MBM (MBM = …
Alternative Methods Of Selection For Litter Size In Mice: I. Characterization Of Base Population And Development Of Methods, A. C. Clutter, Merlyn K. Nielsen, R. K. Johnson
Alternative Methods Of Selection For Litter Size In Mice: I. Characterization Of Base Population And Development Of Methods, A. C. Clutter, Merlyn K. Nielsen, R. K. Johnson
Department of Animal Science: Faculty Publications
Studies on a base population of mice were used to establish an index of components of litter size and a physiological model for measuring uterine capacity to be used subsequently in a selection experiment evaluating alternative methods for practicing selection to increase litter size. Heritability estimates of litter size, ovulation rate and ova success (fraction of ova resulting in fully formed pups) were .18, .33 and .15, respectively. No significant genetic or phenotypic correlation was found between overall ovulation rate and ova success. Phenotypic means and genetic variances were higher for characteristics measured on the right than on the left …