Theses and Dissertations at Montana State University (MSU)
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Item Inbreeding and inbreeding depression in linebred beef cattle(Montana State University - Bozeman, College of Agriculture, 2020) Hieber, Jordan Kelley; Chairperson, Graduate Committee: Jennifer ThomsonThis research applied genomics and phenotypic information in three different beef cattle populations. The methods applied were association analyses, runs of homozygosity, and genetic correlations. This incorporated both genomic and phenotypic approaches to identify the results of linebreeding in two closed Hereford populations. Further work evaluated carcass and maternal traits from the American Simmental Association Carcass Merit Program using genomic and phenotypic information to identify how carcass-based selection decisions impact maternal performance of Simmental-based cattle. Line 4 pedigree inbreeding, genomic inbreeding, and genomic pedigree inbreeding ranges were 0 - 36%, 0 - 49%, and 0 - 29%, respectively, and average inbreeding was 12.6%, 12.3%, and 17.7%, respectively. Line 1 pedigree inbreeding, genomic inbreeding, and genomic pedigree inbreeding ranges were 0 - 71%, 0 - 46%, and 0 - 63%, respectively, and average inbreeding was 42.1%, 14.4%, and 31.0%, respectively. Average rate of change in inbreeding per year was 0.03% over 55 years for Line 4 and -0.03% over 83 years for Line 1. Identified for Line 4 were 45 ROH regions, 35 strongly significant single nucleotide polymorphisms, three strongly significant SNP within ROH, and some significant SNP within 12 previously identified genes. Identified for Line 1 were 50 ROH regions, 93 strongly significant SNP, three strongly significant SNP within ROH, and some significant SNP within 11 previously identified genes. Within the Simmental dataset, nine chromosomes had genome-wide significance, explaining 0.2142 percent of total phenotypic information. The single-locus model identified 365 novel regions and 251 novel positional candidate genes. The multi-locus model identified 393 novel regions and 283 novel positional candidate genes. Also, detrimental genetic correlations between carcass characteristics and maternal traits were less than previously reported. Analyses utilized in this study indicate ROH and significant SNP can be used to identify regions of the genome affected by inbreeding. Also, simultaneous selection for carcass and maternal traits reduced the negative impact seen with single-trait selection for carcass traits.Item The influence of biostimulation on the occurrence of puberty in beef heifers(Montana State University - Bozeman, College of Agriculture, 1985) Roberson, Mark StephenItem Fertility of non-puberal estrus, pregnancy rates and progesterone concentrations of beef heifers bred at puberal or third estrus(Montana State University - Bozeman, College of Agriculture, 1987) Byerley, Darryl JayItem The temporal relationship of the ovary and ovarian morphology for the onset and duratin of behavioral estrus in prostaglandin F 2 alpha-treated ewes(Montana State University - Bozeman, College of Agriculture, 1984) Courtney, Lynn Patricia; Chairperson, Graduate Committee: James G. BerardinelliThe objective of this study was to determine the temporal relationship of ovarian follicles and corpora lutea (CL) on the time to onset (TO) and duration (D) of behavioral estrus in PGF 2 alpha- treated ewes. Forty normally cycling Western White-Faced ewes were randomly assigned to one of eight treatments to be either sham-operated (SO) or ovariectomized (OVX) at 36, 44, 52 or 60 h after a PGF 2 alpha injection given on day 12 of the estrous cycle. At the time of injection (Oh) and every 4 h afterwards for 96 h, each ewe was observed for estrus using a teaser ram. At surgery, ovaries of each ewe were macroscopically examined for number and size (mm) of antral follicles and CL. Ovaries of OVX ewes were prepared for histological evaluation. Actual size and number of follicles and CL were determined by taking photographic slides of stained tissue sections and projecting them onto a paper screen. Follicles were classified as atretic (A) or non atretic (NA), and CL as normal or regressing. Proportion of ewes in estrus was lower (P<.05) for OVX ewes (11 of 20; 55%) than for SO (20 of 20; 100%) and there was a time by treatment interaction (P<.05). Mean TO of estrus was 48.2 + or - 3.6 h for OVX ewes which showed estrus and 52.2 + or - 2.4 h for SO ewes (P>.05); and the overall mean was 50.7 + or - 1.9 h. Duration of estrus was 25.6 + or - .8 h for OVX ewes which showed estrus and 32.6 + or - 3.2 h for SO ewes (P>.05); and the overall mean was 29.8 + or - 2.5 h. There were no treatment effects for either TO or D of estrus (P>.05). At 44, 52 and 60 h fhe number of actual large NA (LNA) follicles was negatively associated with TO of estrus (r= -.97, -.73, -.87, respectively) and positively associated with D of estrus (r-.76, .70, .65). Actual CL volume was positively associated with D of estrus (r=.84, .58, .68) and negatively associated with TO of estrus (r= -.93, -.36, -.39). Total number of actual antral follicles did not change over time (P>.05), nor did number of follicles in the small (1-3.9mm), medium (4.0-5.9mm) and large (>6.0mm) size groups (P>.05). There was a shift in class of follicles such that number of medium NA follicles decreased and number of LNA follicles increased from 36 to 52 h (PC.05). CL size was smaller at 60 h (P<.05), while CL volume remained constant (P>.05). These results indicated that there is a temporal relationship of the ovary for the TO and D of estrus in that the ovary is required for at least 44 h, probably longer, for estrus to occur. However, once estrus has been initiated the presence of the ovary is no longer required for the normal expression of estrus. Individual variation in the TO and D of estrus may be related to differences in the number of LNA follicles and (or) CL volume.Item Sire by sex and sire by management unit interactions in Simmental cross calves(Montana State University - Bozeman, College of Agriculture, 1977) Friedrich, Robert LarsItem Lactation curves and milk production in beef cattle with varying degrees of crossbred influence(Montana State University - Bozeman, College of Agriculture, 1984) Casebolt, David GeorgeItem Postpartum interval to estrus and patterns of luteinizing hormone (LH) concentrations in first-calf suckled beef cows exposed to mature bulls(Montana State University - Bozeman, College of Agriculture, 1988) Custer, Edward EarlItem Factors affecting ovulation rate, fertilization rate and ova normality in ewes managed under range conditions(Montana State University - Bozeman, College of Agriculture, 1965) Engle, Clair C.Item AI beef management with prostaglandin F 2alpha controlled estrus(Montana State University - Bozeman, College of Agriculture, 1977) Lambert, Paul WilsonItem Comparison of Finnish Landrace crossbred ewes with Columbia, Rambouillet, and Targhee on western range(Montana State University - Bozeman, College of Agriculture, 1984) Lewis, Robert David