Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
Browse
7 results
Search Results
Item Effect of supplemental trace mineral level and form on peripubertal bulls(Montana State University - Bozeman, College of Agriculture, 2003) Alexander, Whisper Lynn; Chairperson, Graduate Committee: Raymond P. Ansotegui.Item Biostimulatory effect of bulls : exposure type and day of exposure on resumption of postpartum ovarian cycling activity in first-calf suckled beef cows(Montana State University - Bozeman, College of Agriculture, 2002) Joshi, Pramod ShrinivasItem A comparison of progeny tests with sires tested on different cow herds and under different environmental conditions(Montana State University - Bozeman, College of Agriculture, 1947) Woodward, Ray R.Item Changes in temporal leptin concentrations and other metabolic factors in primiparous, postpartum, anestrous, suckled beef cows exposed to bulls(Montana State University - Bozeman, College of Agriculture, 2009) Olsen, Jesse Riley; Chairperson, Graduate Committee: James G. Berardinelli.Exposing cows to bulls or excretory products of bulls stimulates resumption of ovarian cycling activity in postpartum, suckled, anestrous cows. This biostimulatory effect may be mediated by pheromones produced by bulls that stimulate physiological changes in metabolic regulation of the hypothalamic-pituitary-ovarian (HPO) axis of cows. In Experiment 1, the hypotheses tested were that concentrations of glucose, NEFA, thyroxine (T4), tri-iodothyronine (T3), and T3:T4 ratios do not differ between cows exposed to bulls or steers. The biostimulatory effect of bulls was associated with lower mean concentrations of NEFA in postpartum cows. Experiment 2 was designed to determine if continuous (24-h daily) bull exposure alters temporal patterns of leptin concentrations in postpartum, anestrous cows. Cows exposed to bulls that resumed cycling activity after the start of the experiment tended to have higher leptin concentrations by the end of the 30-d exposure period than cows not exposed to bulls. However, it was not known if these changes were related to resumption of ovarian cycling activity in postpartum, anestrous cows. Experiment 3 tested the hypothesis that temporal leptin concentrations may depend upon duration of daily bull exposure. Cows had higher daily leptin concentrations and resumed ovarian cycling activity sooner as duration of daily bull exposure increased. In conclusion, as duration of daily bull exposure increases, the biostimulatory effect of bulls alters temporal leptin concentrations and this change may facilitate or support the function of the HPO axis and accelerate resumption of ovarian cycling activity in primiparous, postpartum, suckled, anestrous cows.Item The biostimulatory effect of bulls on postpartum follicular wave development in postpartum, anestrous, suckled beef cows(Montana State University - Bozeman, College of Agriculture, 2009) Wilkinson, Jarrod Robert Charles; Chairperson, Graduate Committee: James G. Berardinelli.The objective of this experiment was to determine if bull exposure influences follicular wave dynamics in primiparous, postpartum, anestrous, suckled, beef cows exposed to bulls. In Experiment 1, cows were exposed (continuously 24 h/d), (EB; n = 5) to bulls or not exposed to bulls (NE; n = 5) throughout the experimental period. In Experiment 2, cows were exposed to bulls for either 12 h, (EB12; n = 15), 6 h, (EB6; n =14) or not exposed to bulls (NE; n = 10) from the start to the end of the experimental period. In Experiments 1 and 2, cows were 67 d ± 3.8 (mean ± SE) and 51.5 ± 2.3 d postpartum at the start of the experiment. Follicular characteristics of each cow were examined by transrectal ultrasonography. In Experiment 1, interwave interval for wave 3 was shorter in EB than NE cows. Maximum dominant follicle (MDF) diameter tended to be greater during wave 2 for EB than NE cows, while wave 3 was greater for EB than NE cows. However, MDF diameter for wave 6 was greater for NE than EB cows. In Experiment 2, EB12 cows had fewer follicular waves to the resumption of luteal activity (RLA) than NE cows, while the number of waves to RLA for EB6 cows did not differ from that of EB12 or NE cows. Normalizing follicular waves to the time of RLA for cows within the EB12 and EB6 indicated that those cows at RLA had larger MDF diameters for the wave that produced the ovulatory follicle than cows that did not RLA. These data show the effects of bull exposure in altering follicular growth and developmental patterns, shortening the inter-wave interval and increasing the MDF diameter. Though the mechanism through which bull exposure alters postpartum follicular development is not entirely understood, these data provide new understanding.Item An economic comparison of breeding performance of yearling and two-year-old bulls(Montana State University - Bozeman, College of Agriculture, 1990) Carroll, Llane Glenn; Chairperson, Graduate Committee: R. Clyde Greer.An important decision a rancher makes is the age at which a bull will first be used for breeding. While yearling bulls are used by many ranchers in the Great Plains States, there is concern that lack of maturity among yearling bulls leads to lower breeding performance. To compare the breeding performance of yearling and two-year-old bulls Line One Hereford bulls in single sire breeding herds at Fort Keogh Livestock and Range Research Laboratory (LARRL) were analyzed. Tests for differences in pregnancy rates, calving dates, calf birth weight, and calf average daily gain were conducted. The physical attribute distributions were converted to a returns distribution for each age of bull. The distributions were then compared in a stochastic dominance framework. From the results it was concluded that the alternative "use the bull first as a two-year-old" dominated the alternative "use the bull first as a yearling" in the first order stochastic sense. While ranchers are using yearling bulls, the expected income is higher and the dispersion of observed income smaller from herds bred to two-year-old bulls. Ranchers may be deriving other benefits from the use of yearling bulls such as decreased intervals for introducing special genetic traits. Ranchers may be using yearlings in multiple sire settings which may diminish the downside risk of using yearling bulls as compared to using yearling bulls in single sire settings.Item The information content of seller-provided presale data in cattle auctions(Montana State University - Bozeman, College of Agriculture, 1997) Chvosta, Jan; Chairperson, Graduate Committee: Randal R. Rucker ; Myles Watts (co-chair)Both buyers and sellers of goods whose exact characteristics are uncertain have incentives to develop methods of reducing duplicative buyer presale measurements. This thesis examines this issue in the context of the cattle industry where sellers provide different types of presale information to reduce buyers' presale measurement activities. Of particular interest are marketing mechanisms that have developed in auctions for breeding bulls. At auctions of yearling bulls, sellers often provide buyers with information on such characteristics as the hull's birth, weaning, and yearling weights, as well as the hull's pedigree. A primary focus of this thesis is to compare the information contained in these simple performance measures (SPMs) with the information contained in recently developed alternative measures of prospective performance. This alternative--expected progeny differences (EPDs)-uses statistical methods not only to incorporate information on the characteristics of the sale bull, but also the bull' s relatives. The statistical method employed for this comparison is multiple regression analysis. The sale price of a bull is regressed on the hull's performance measures and other terms specified in the seller-buyer agreement. The regression results suggest that the simple performance measures (SPMs) contain substantial information in addition to that contained in expected progeny differences (EPDs). Conversely, it was found that EPDs contain some information in addition to that contained in SPMs, but this information is very limited. This finding is unexpected. EPDs, by construction design, contain the information found in SPMs, plus additional information on traits of related animals. Thus, it was hypothesized that the SPM measurements would contain no additional information beyond that contained within EPDs. The results of this research, however, suggest the contrary. An important question to be addressed by the cattle industry, therefore, is whether the costs of further development of EPDs are warranted.