Theses and Dissertations at Montana State University (MSU)
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Item Genomic, microbial, and linear relationships between residual feed intake, dry matter intake, average daily gain, and post weaning weights in range sheep(Montana State University - Bozeman, College of Agriculture, 2023) Schaub, Daniel James; Chairperson, Graduate Committee: Christian J. PosberghOver forty years, United States sheep producers have selectively bred range sheep for larger post-weaning weights using estimated breeding values. However, this has led to increased feed intake, prompting this study's objective to quantify the relationship between lamb growth estimated breeding values, feed intake, and feed efficiency. The study involved 40 Targhee and 40 Rambouillet ewe lambs weaned at four months and put on a GrowsafeTM feeding system for a 56-day experimental period, with ewes weighed weekly and at the start and end of the trial. Residual feed intake was calculated using body weights, average daily gain, and daily feed intake measurements. The ewe lambs' post-weaning weight estimated breeding value was associated to their phenotypic traits. These procedures were repeated when the same ewes were yearlings and at maintenance. The study found that while post-weaning weight estimated breeding values predicted dry matter intake (P<0.05), they lacked association with residual feed intake (P>0.05) in both experimental periods. However, the ewe's post-weaning weight estimated breeding value predicted mid-trial body weight in both periods (P<0.05). Thus, while selecting higher post- weaning weight animals may increase feed usage due to larger body size, it does not affect feed efficiency. Comparing the residual feed intake between the two experimental periods, growth residual feed intake measurements did not predict residual feed intake in maintenance. Therefore, caution should be used when utilizing residual feed intake from the growth period as an indicator of feed efficiency in maintenance. The study also examined rumen microbial profiles in sheep between the two experimental periods. Methanogenic archaea were relatively increased within the growth experimental period, where a pelleted diet was used, and cellulolytic bacteria were increased in the maintenance experimental period, where hay was provided. Since methanogens are associated with decreased feed efficiency, diet may play a role in changing a sheep's microbiome towards more feed efficient bacteria. Finally, a genome-wide association study found the Dmrt2 gene associated with DMI and RFI in maintenance. The Dmrt2 gene may regulate muscle and bone development in the early embryo, affecting feed efficiency in sheep later in life.Item Experimental infection of specific pathogen-free domestic lambs with Mycoplasma ovipneumoniae(Montana State University - Bozeman, College of Agriculture, 2021) Johnson, Thea Haviland; Chairperson, Graduate Committee: Diane Bimczok; Diane Bimczok, Kerri Jones, Cassie Mosdal, Steven Jones, SK, CB, AS, and B. Tegner Jacobson were co-authors of the article, 'Immunoglobulin transfer, survival, and growth in motherless lambs fed a bovine serum-based colostrum replacer' which is contained within this thesis.; Kerri Jones, B. Tegner Jacobson, Julia Schearer, Noah Adams, Isaak Thornton, Cassie Mosdal, Steven Jones, Mark Jutila, Agnieszka Rynda-Apple, Thomas Besser and Diane Bimczok were co-authors of the article, 'Experimental infection of specific-pathogen-free domestic lambs with Mycoplasma ovipneumoniae causes asymptomatic colonization of the upper airways that is resistant to antibiotic treatment' in the journal 'Veterinary microbiology' which is contained within this thesis.Mycoplasma ovipneumoniae (M. ovi) is a respiratory pathogen commonly found in sheep and goats. It is associated with mild to moderate respiratory disease in domestic lambs, but severe pneumonia outbreaks in wild ruminants, specifically bighorn sheep. The goal of our study was to better understand the role of M. ovi as a respiratory pathogen in domestic sheep and to explore potential antibiotic treatment approaches. We first established a flock of specific pathogen-free (SPF) lambs through supervised lambing and motherless rearing in a Large Animal BSL-2 facility. Lambs were fed a colostrum replacer that yielded low mortality, steady weight gain and serum IgG and protein concentrations comparable to those of lambs raised on ewe colostrum. We inoculated the SPF lambs with field isolates of M. ovi and monitored the lambs for eight weeks for colonization with the bacteria, M. ovi-specific antibodies, clinical symptoms, and cellular and molecular correlates of lung inflammation. After eight weeks, lambs were treated with the macrolide antibiotic gamithromycin and observed for an additional four weeks. Stable colonization of the upper respiratory tract with M. ovi was established in all four M. ovi-inoculated, but in none of the four mock-infected lambs. All M. ovi-infected lambs developed a robust antibody response to M. ovi within 2 weeks. However, we did not observe significant clinical symptoms, evidence of lung damage or inflammation in any of the infected lambs. Interestingly, treatment with gamithromycin failed to reduce M. ovi colonization. These observations indicate that, in the absence of co-factors, M. ovi causes asymptomatic colonization of the upper respiratory tract of that is resistant to clearance by the host immune response as well as by gamithromycin treatment in domestic lambs.Item Attitude and value study of the 4-H market lamb project in Gallatin County(Montana State University - Bozeman, 1978) Isaacs, Nicholas WaldonItem Influence of supplementation on the productivity of ewes grazing improved pasture and suckling twins(Montana State University - Bozeman, College of Agriculture, 1988) Frey, Ana LidiaItem The effect of aureomycin upon lamb mortality and body weights and the effect of delayed feeding upon weaning weights(Montana State University - Bozeman, College of Agriculture, 1957) Bassett, James WilburItem The effect of Aureomycin in pelleted or whole grain creep rations fed to suckling lambs : the effect of Thyroprotein, Thiouracil, and Stilbestrol on gains of fattening lambs(Montana State University - Bozeman, College of Agriculture, 1956) Daley, Charles A.Item A study of the effect of feeds on the cooking quality of lamb(Montana State University - Bozeman, College of Education, Health & Human Development, 1933) Belden, Judith JeanItem The economics of lamb fattening(Montana State University - Bozeman, College of Agriculture, 1939) Grenier, Ovide E.Item Production of two-year-old ewes(Montana State University - Bozeman, College of Agriculture, 1957) Colman, Kenneth L.; Chairperson, Graduate Committee: J. L. Van HornThe purpose of the investigation of these data was to explore the possibilities of relationships existing between the body weights of the ewes during their early life and their subsequent lamb and wool production as two-year-olds. The effects of environmental influences, such as type of birth and age at weaning, on the growth of ewe lambs and their production as two-year-olds were studied. The growth of two-hundred and fifty-nine ewes was measured by body weights taken at irregular intervals from birth to twenty-three months of age. Records of the individual lamb and wool production of these ewes were tabulated with the body weights. Results showed that the effect of type of birth and age at weaning, on body weights of ewe lambs was reduced as the lambs progressed toward maturity from weanling age. It was also found that the birth weights, weaning weights, and fall yearling weights of the ewes were significantly related. The fall yearling weight of the ewes was most indicative of two-year-old lamb and wool production. A significant relationship was found between the birth weights of the Rambouillet ewes and the pounds of lamb born per ewe as two-year-olds. The relationship between the birth weights of the Targhee ewes and the pounds of lamb born per ewe was not significant nor was this relationship significant for the birth weights of the Columbia ewes and the pounds of lamb born per ewe. The early single-born lambs were consistently lighter at birth than the late single-born lambs; however, at weaning time, the early single-born lambs were consistently heavier than the late single-born lambs. The average daily gain of the early single-born lambs and the late single-born lambs was about the same. The weaning weights of the ewes and their yearling fleece weights were significantly and positively related. The difference between the yearling fleece weights of the ewes and their two-year-old fleece weights was significant, the yearling fleece weights being the heaviest. It is evident from this study that valuable genetic breeding stock may be lost if suitable precautions are not taken to adjust for environmental conditions affecting the size of ewe lambs at weaning time when most replacements are selected. According to these data and that published previously by other workers, a sounder method of selecting higher producing replacements is to retain a larger number of ewe lambs at weaning and to make final selections at fall yearling age. Since production factors are closely related to body weight at fall yearling age, the heavier ewes of similar breeding will be better producers than the lighter ewes if selections are made at this age.Item Lamb selection by index(Montana State University - Bozeman, College of Agriculture, 1949) Williamson, Leslie O.