Thesis (Ph. D.)--University of Wisconsin--Madison, 1935. / Typescript. With this is bound: Analysis of variation in the sexual cycle and some of its component phases with special reference to cattle / by A.B. Chapman and L.E. Casida. Reprinted from Journal of agricultural research, vol. 54, no. 6 (15 March 1937), p. 417-435. Includes bibliographical references (leaves [78]-[83]).

Thesis--Ph. D., University of Hong Kong. / Typewritten.

published_or_final_version / Zoology / Doctoral / Doctor of Philosophy

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 76-78). Also available via the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1980. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 296-297).

Thesis (Ph.D.)--Aberdeen University, 2009. / Includes bibliographical references.

In mammals, day-length-sensitive (photoperiodic) seasonal breeding cycles depend on the pineal hormone melatonin, which modulates secretion of reproductive hormones by the anterior pituitary gland.  It is thought that melatonin acts in the hypothalamus to control reproduction through the release of neurosecretory signals into the pituitary portal blood supply, where they act on pituitary endocrine cells. Contrastingly, the work presented here shows that during the reproductive response of Soay sheep exposed to summer day lengths, the reverse applies. Melatonin acts directly on anterior-pituitary cells, and these then relay the photoperiodic message back into the hypothalamus to control neuroendocrine output. The switch to long days causes melatonin-responsive cells in the pars tuberalis (PT) of the anterior pituitary to increase production of thyrotrophin (TSH).  This acts locally on TSH receptor (TSH-R)-expressing cells in the adjacent mediobasal hypothalamus, leading to increased expression of type II thyroid hormone deiodinase (DIO2).  DIO2 initiates the summer response by increasing hypothalamic triiodothyronine (T3) levels. The present work also reports similar expression of TSH-R, TSH and DIO2 in European hamster, while DIO3 was oppositely regulated. These data and recent findings in quail indicate that the TSH-expressing cells of the PT play an ancestral role in seasonal reproductive control in vertebrates.  In mammals this provides the missing link between the pineal melatonin signal and thyroid-dependent seasonal biology.

Ruddy Ducks in the Chilcotin parklands of British Columbia nest in late June, July and early August, later than most other waterfowl species breeding in southwestern British Columbia, Canada. This thesis considers factors that may affect the timing of breeding in Ruddy Ducks by comparing Ruddy Ducks to Barrow's Goldeneye and Bufflehead (species that breed early but do not renest) and to American Coot (a species that breeds early and is able to renest). These factors include predation, flooding and desertion of nests, feeding behavior of ducklings, abundance of food, availability of green vegetation and fluctuations in temperature. Possible advantages of late breeding include reduced nest predation and higher ambient temperature during incubation. Longer dive durations and more frequent feeding and resting by Ruddy ducklings may enable ducklings to maximize energy for growth. Reduced nest flooding late in the season, dependence on green vegetation for nesting and greater abundance of food for young in summer were not demonstrated by this study. Therefore, these factors apparently do not explain the timing of breeding in Ruddy Ducks in southwestern British Columbia. Despite insufficient time to renest and shorter time for ducklings to mature before ponds freeze, the average number of 2B age class young produced per pair of Ruddy Ducks was similar to that of American Coots. Forty percent of nesting Ruddy females did not hatch any young, whereas almost all nesting Coot females successfully hatched young; however, survival of Ruddy ducklings to 2B age class (four weeks old) was higher than that of American Coots, Barrow's Goldeneye and Bufflehead. / Science, Faculty of / Zoology, Department of / Graduate

Mixed model equations to predict additive and nonadditive genetic values also predict specific combining abilities or combination effects among sire and dams or among sires and maternal grandsires (mgs). Current mating programs, utilizing nonadditive genetic variance only by avoiding mating between close relatives to prevent inbreeding depression, could be improved upon by use of predicted combination effects due to nonadditive variation beyond inbreeding. Simulation was employed to evaluate increase in progeny performance from nonrandom mating based on predicted combination effects among sires and mgs over random mating. Nonrandom mating strategies included mate allocation by linear programming, which is optimum, and two approximations, sequential selection based on progeny merit, and sequential selection based on deviation of progeny merit from mgs average. Genetic parameters were heritability equal to .05, .15, or .25 and ratio of dominance variance to phenotypic variance equal to .05, .10, or .15. These dominance ratios represent the range of recent estimates for yield and type traits. A total of 400 bulls were grouped by .99, .85, and .70 PTA reliability, with the first group being sires and mgs of the others. Using recurrence equations for combination effects, a matrix of true combination effects among the bulls was created. Reliabilites for estimated combination effects were computed for three types of bull populations; one with much information available (.41 to .79 ), one with little information ( .15 to .41 ) and one with an intermediate amount of information available (.15 to .79) and used to form matrices of estimated combination effects. Herds consisted of cows sired by .99 and .85 reliability bulls. Four mating groups of 123 cows, mated to 10 bulls from all bull groups, produced heifers to replace the herd. Herds were replicated 20 times for each type of bull population and each combination of heritability and dominance ratio. The three nonrandom mating strategies yielded means significantly different from random mating (p ≤ .05). When scaled by the standard deviation of milk yield, gains made by linear programming were 12.3 to 40.1 kg for low-reliability populations, 16.4 to 46.4 kg for intermediate reliability populations, and 31.0 to 80.3 kg for high reliability populations. Herds modified to utilize embryo transfer had less gain in progeny merit due to combination effects (20kg) with nonrandom mating compared to non-ET herds with identical heritability and dominance ratio, when donor cows were selected by estimated breeding value. Selection of donor cows based on combination effects yielded large gains (90.72kg) but such selection would only be justified in populations where nonadditive variance was more important than additive. A procedure for routinely approximating reliabilites of combination effects using information from three sources (information on parent subclasses, information on progeny subclasses, and records in subclass of interest) was presented. / Master of Science

Mit der vorliegenden Arbeit erfolgt erstmals eine vergleichende Studie hinsichtlich der endometrialen Funktionsmorphologie unter Einbezug klinisch-gynäkologischer Befunde und endokrinologischer Parameter bei zyklischen und nicht zyklischen Maultierstuten über den Zeitraum einer physiologischen Zuchtsaison. Dazu wurden beim Pferd etablierte Untersuchungsverfahren eingesetzt, was neben einer klinisch-gynäkologischen Untersuchung einschließlich Palpatio per rectum, Ultraschall der inneren Geschlechtsorgane und Vaginoskopie sowie die pathohistologische Auswertung von Endometriumpioptaten beinhaltete. Parallel dazu wurde zur Sicherung der Zyklusansprache und zur Erstellung eines endokrinologischen Verlaufsprofiles Blut zur Bestimmung der Sexualsteroide entnommen. Hierzu wurden sechs allgemein- und geschlechtsgesunde Maultierstuten über einen Zeitraum von Mitte April bis Mitte November in Abständen von zwei bis zehn Tagen untersucht. Die bei der Pferdestute etablierten Untersuchungsverfahren konnten auch bei den Maultierstuten wiederholt, aussagekräftig und komplikationslos eingesetzt werden. Besonders die Technik der Endometriumbiopsie mit Spreizspekulum, Zervixfasszange und Entnahmegerät zeigte sich als praktikabel und sicher bezüglich der Vermeidung von Verletzungen oder Kontamination der inneren Geschlechtsorgane mit lokaler Infektion. Es erfolgte eine Einteilung der Tiere in eine „azyklische“ Gruppe 1 und eine „zyklische“ Gruppe 2. Alle azyklischen Maultierstuten der Gruppe 1 zeigten während des Untersuchungszeitraumes sowohl klinisch als auch pathohistologisch eine vollständige Azyklie. Die bei den Blutproben gewonnenen Serumhormonwerte lagen bei der Gruppe 1 konstant im basalen Bereich. Histologisch wurde ein inaktives, irregulär differenziertes Endometrium vorgefunden. Die zyklischen Maultierstuten der Gruppe 2 wiesen eine variable endometriale Funktionsmorphologie mit teilweise ausgeprägter Fehldifferenzierung auf. Die Serumhormonwerte der Gruppe 2 zeigten starke Schwankungen und es konnte dabei keine Korrelation zwischen den klinisch-endokrinologischen Parametern und der endometrialen Funktionsmorphologie beobachtet werden. Weiterhin zeigten alle Tiere der Gruppe 1 und 2 eine Endometrose. Die endometrialen Gefäße wurden von jeder Maultierstute untersucht und der Gefäßschädigungsindex in Relation zum Alter dargestellt, wobei sich eine Altersassoziation hinsichtlich der Intensität der Gefäßalterationen ergab. Die Untersuchungsergebnisse der Endometriumbioptate jeder Maultierstute für sich gesehen, waren qualitativ und quantitativ über den langen Untersuchungszeitraum immer identisch und wiesen eine ausgeprägte Konstanz und Homogenität auf. Dies lässt den Rückschluss zu, dass die Ergebnisse repräsentativ für das ganze Endometrium der jeweiligen Maultierstute sind. Die Infertilität des Maultiers ist sicher durch genetische Ursachen, wie den ungeraden Chromosomensatz 2n=63 (WODSEDALEK 1916) begründet, aber auch Folgeerscheinungen wie eine reduzierte ovarielle Aktivität, eine Störung der Hypothalmus-Hypophysen-Ovarien-Uterus-Achse und eine daraus resultierende oder schon bestehende endometriale Fehldifferenzierung sind anhand der Ergebnisse dieser Studie als Ursachen der Infertilität zu berücksichtigen. Die eigenen Ergebnisse sprechen nicht dafür, dass Maultierstuten mit spontanem Zyklusgeschehen ohne exogene Unterstützung als Rezipienten für einen Embryotransfer geeignet sein dürften.