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Articles 1 - 10 of 10
Full-Text Articles in Sheep and Goat Science
Estradiol’S Role In Timely Puberty Onset In The Ewe, Eliana Gerardine Aerts
Estradiol’S Role In Timely Puberty Onset In The Ewe, Eliana Gerardine Aerts
Graduate Theses, Dissertations, and Problem Reports (ETD)
In female sheep, the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus triggers luteinizing hormone (LH) to be released from the pituitary. Luteinizing hormone, in turn, acts on the ovaries to elicit estradiol (E2) release. E2 acts in a negative feedback manner to control the amount of LH released. The increase in LH release that drives puberty onset results from a decrease in sensitivity to E2 as the animal ages. However, the neural mechanisms mediating this change in sensitivity are not known, as is where in the hypothalamus E2-negative feedback occurs. In the arcuate …
Puberty-Associated Changes In Kiss1r, Mc3r, And Mc4r In The Ewe, Ashleigh Caitlyn Thomson
Puberty-Associated Changes In Kiss1r, Mc3r, And Mc4r In The Ewe, Ashleigh Caitlyn Thomson
Graduate Theses, Dissertations, and Problem Reports (ETD)
The neural mechanisms that control the onset of puberty are not completely understood. In livestock, the onset of puberty relies on an increase in gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH). Kisspeptin, neurokinin B, and dynorphin neurons (KNDy) and their receptors, Kiss1r, NK3R, and KOR, respectively, are important regulators of puberty. Previous data from our laboratory has shown that KNDy neurons may be responding to other inputs, including the melanocortin system, that will affect the timing of puberty. Given this, we examined kisspeptin receptor (Kiss1r) mRNA expression in GnRH neurons as well as examining melanocortin 3 and 4 receptor …
Immune Outcomes Affected By Selection For Parasite Resistance In Katahdin Sheep, Kelsey Lynne Bentley
Immune Outcomes Affected By Selection For Parasite Resistance In Katahdin Sheep, Kelsey Lynne Bentley
Graduate Theses, Dissertations, and Problem Reports (ETD)
Our understanding of the complex connection between selection for parasite resistance and the overall health outcomes in livestock is unclear. This study investigates the impact of post-weaning fecal egg count (PFEC) estimated breeding values (EBV) on health outcomes and immune responses in Katahdin sheep. Selection for PFEC, favoring Low-PFEC lambs, not only affects survivability to weaning but also suggests broader implications for immunity beyond parasite resistance. The effect of PFEC EBV on antibody production in response to vaccination against Clostridium perfringens type C&D and tetanus toxoid (CD&T) revealed a stepwise decrease in immunoglobin (IgG) from Low-PFEC to High-PFEC groups upon …
Exploring The Biological Basis Of Residual Feed Intake In Beef Cattle Using Multi-Omics Analysis., Godstime Ayobami Taiwo
Exploring The Biological Basis Of Residual Feed Intake In Beef Cattle Using Multi-Omics Analysis., Godstime Ayobami Taiwo
Graduate Theses, Dissertations, and Problem Reports (ETD)
Efficient feed utilization is critical for both economic sustainability and environmental responsibility in modern livestock production. While there has been extensive research, the multifaceted nature of feed efficiency remains complex, with many biological factors still unexplored. This dissertation examines the physiological foundations of feed efficiency by elucidating some of the complex biological mechanisms associated with residual feed intake (RFI) phenotype in beef cattle, using a range of Omics approaches. We hypothesized that metabolites related to amino acids, carbohydrates, and fatty acids could act as potential biomarkers for RFI. Through a chemical group-based metabolomics method, we identified enriched pathways in feed-efficient …
Impact Of Haemonchus Contortus On Feed Efficiency And Feeding Behavior Of Katahdin And Suffolk Lambs, Camren L. Maierle
Impact Of Haemonchus Contortus On Feed Efficiency And Feeding Behavior Of Katahdin And Suffolk Lambs, Camren L. Maierle
Graduate Theses, Dissertations, and Problem Reports (ETD)
Nutritional impact of internal parasitism, specifically Haemonchus contortus (Hc), is a significant contributor to production losses in small ruminants. Both chronic and subclinical infections generate millions of dollars of losses worldwide. Understanding the nutritional impact of Hc on lamb performance is crucial in determining the additional nutrient requirements of infected individuals. The aim of this study was to evaluate nutritional impact of Hc on infected Katahdin lambs with extensive genetic selection for parasite resistance and susceptible Suffolk lambs. Growth, feeding behavior, and feed efficiency (RFI. F:G) were evaluated during artificial Hc infection. Katahdin ewes from the Virginia …
Effect Of Fecal Egg Count Estimated Breeding Value On Antibody Production In Katahdin Lambs, Kelsey L. Bentley
Effect Of Fecal Egg Count Estimated Breeding Value On Antibody Production In Katahdin Lambs, Kelsey L. Bentley
Graduate Theses, Dissertations, and Problem Reports (ETD)
With current pressures to seek out genetic solutions to combat antimicrobial resistance, genetic resistance to the gastrointestinal nematode Haemonchus contortus may reduce need for prophylactic antibiotic use. The Katahdin breed has effectively utilized post-weaning fecal egg count estimated breeding value (PFEC EBV) to reduce parasitism within their flocks, but there still remains significant opportunity for selection within breed. In a previous study, Katahdin sheep sired by low PFEC sires had greater survivability to weaning than lambs sired by high PFEC rams and preweaning was caused by other diseases than parasitism. Those data lead to the hypothesis that selection for PFEC …
Haemonchus Contortus Antigen Identification And Use Of Tropomyosin In Ovine Vaccine Development, Brynnan P. Russ
Haemonchus Contortus Antigen Identification And Use Of Tropomyosin In Ovine Vaccine Development, Brynnan P. Russ
Graduate Theses, Dissertations, and Problem Reports (ETD)
Globally, the small ruminant industry loses hundreds of millions of dollars due to parasitism by the gastrointestinal nematode Haemonchus contortus. This parasite feeds on blood in the host’s abomasum leading to disease including anemia, hypoproteinemia, lethargy, and death. There have been exhaustive efforts to manage this parasite including different management applications, anthelmintic treatment, and now integration of resistance genetics into a flock. Like antibiotics, overuse of anthelmintics has led to resistance of H. contortus to these drugs. Therefore, other methods of control are the main focuses of many research initiatives. St. Croix are a resistant breed of sheep that mount …
Impact Of Sire Selection And Breed On Parasite Resistance In Sheep, Andrew Ryan Weaver
Impact Of Sire Selection And Breed On Parasite Resistance In Sheep, Andrew Ryan Weaver
Graduate Theses, Dissertations, and Problem Reports (ETD)
Selection within and among breeds are strategies to mitigate the impact of parasitism given failing chemotherapeutics. While Texels have improved marketability compared to other parasite-resistant breeds, the mechanism by which Texels reduce fecal egg count (FEC) is unclear. The immune response to Haemonchus contortus (Hc) was compared in Texel, parasite-resistant St. Croix, and parasite-susceptible Suffolk sheep. Adult worms exposed to St. Croix- and Texel-derived peripheral blood mononuclear cells and serum in vitro had greater binding around the reproductive structures than Suffolk and worm egg release tended to be affected by breed (P = 0.09). Resistance in Texels …
Effect Of Sire Breed On Grass-Based Lamb Production, Camren L. Maierle
Effect Of Sire Breed On Grass-Based Lamb Production, Camren L. Maierle
Graduate Theses, Dissertations, and Problem Reports (ETD)
Improvement of lamb performance in low-input operations may prove vital for the sustainability of eastern US sheep production. Maintaining growth while improving carcass conformation using terminal sire crossbreeding systems may increase value in a pasture-based system. Therefore, the aim of this study was to compare effects of terminal sire breed on parasitism, growth, marketability of grazing lambs. Suffolk (SU; n = 2) and Texel (TX; n = 2) sires were mated to commercial ewes at the WVU Organic Farm. April-born lambs were managed on pasture as one group until weaning (mid-June), then were separated into 3 replicates per sire breed. …
Characterization Of Ovine Monocytes In Response To Haemonchus Contortus Larvae In Vitro And A Novel Role Of Interleukin-13 Inducing Larval Paralysis, Elizabeth Shepherd
Characterization Of Ovine Monocytes In Response To Haemonchus Contortus Larvae In Vitro And A Novel Role Of Interleukin-13 Inducing Larval Paralysis, Elizabeth Shepherd
Graduate Theses, Dissertations, and Problem Reports (ETD)
Haemonchus contortus is a hematophagous, gastrointestinal parasite affecting small ruminants. Parasitism by H. contortus is the greatest concern of sheep producers in the United States and accounts for billions of dollars in economic loss worldwide. However, different breeds of sheep display differences n natural resistance to H. contortus. St. Croix hair sheep have a remarkable ability to clear H. contortus without the aid of anthelmintics and develop a robust T helper type 2 (Th2) immune response, preventing establishment of infective stage 3 larvae (L3), when compared to susceptible Suffolk sheep. However, the mechanism of development of immune response and …