Merlyn K. Nielsen

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Energy balance is a complex trait with relevance to the study of human obesity and maintenance energy requirements of livestock. The objective of this study was to identify, using unique mouse models, quantitative trait loci (QTL) influencing traits that contribute to variation in energy balance. Two F2 resource populations were created from lines of mice(More)
Eleven generations of selection for increased index of ovulation rate and embryonal survival rate, followed by three generations of selection for litter size, were practiced. Laparotomy was used to count corpora lutea and fetuses at 50 d of gestation. High-indexing gilts, approximately 30%, were farrowed. Sons of dams in the upper 10% of the distribution(More)
Genotypic and phenotypic data were collected to estimate chromosomal position of the callipyge (CLPG) gene and to test gene action. Nine Dorset rams of extreme muscling phenotype and 114 Romanov ewes composed the grandparent generation of a resource flock of 362 F2 lambs segregating at the CLPG locus. The parent generation consisted of eight F1 sires and(More)
A resource flock of 362 F2 lambs provided phenotypic and genotypic data to estimate effects of callipyge (CLPG) genotypes on growth, slaughter, and carcass traits. Lambs were serially slaughtered in six groups at 3-wk intervals starting at 23 wk of age to allow comparisons at different end points. Probabilities of CLPG genotypes were calculated at a(More)
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(More)
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(More)
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(More)
Growth, feed intake, and temperament indicator data, collected over 5 yr on a total of 1,141 to 1,183 mixed-breed steers, were used to estimate genetic and phenotypic parameters. All steers had a portion of Hereford, Angus, or both as well as varying percentages of Simmental, Charolais, Limousin, Gelbvieh, Red Angus, and MARC III composite. Because the(More)
Divergent selection in mice was applied in 3 independent replicates for high (maintenance high; MH) and low (maintenance low; ML) heat loss for 16 generations. An unselected control (maintenance control; MC) was also maintained in all replicates. Selection ceased for 26 generations; heat-loss measurement and selection resumed at generation 42. Lactation(More)
Mouse populations differing in metabolic rate have been developed through selection for high (MH) and low (ML) heat loss (HLOSS), along with randomly selected controls (MC). Objectives of this study were to (a) compare MH, ML and MC lines for HLOSS and correlated traits of feed intake, body composition and organ weights; (b) compare three widely used inbred(More)