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Subject: sheep

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    Estimating the Impacts of Litter Size and Non-Additive Genetic Effects on Ewe Longevity and Stayability in a U.S. Western Extensive Range Production System
    (North Dakota State University, 2021) Oribamise, Babatunde Victor
    Non-additive genetic effects are usually ignored in animal breeding programs due to data structure, computational limitations, and over-parameterization of the models. Non-additive genetic effects play an important role in the expression of complex traits in livestock species, such as longevity and stayability. Components of genetic variance for additive and non-additive genetic effects were estimated for longevity and stayability in U.S. Western ewes using pedigree relationship matrices. Litter size were also investigated for direct and maternal effects. For longevity, a larger proportion of phenotypic variance was explained by non-additive genetic effects than by additive effects for model A+D, indicating that including dominance genetic effects are important. Results suggest that inclusion of non-additive genetic effects in animal models is possible in estimating longevity and stayability and will improve selection accuracy and reduce overestimation of additive genetic effects.
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    Effects of Nutrient Restriction, Realimentation, and Twinning on Plasma Volume, Umbilical Hemodynamics and Placental Characteristics in the Pregnant Adolescent Ewe
    (North Dakota State University, 2019) Vasquez Hidalgo, Manuel Alexander
    Reproductive physiology in production animals is a key economic component of longevity and profitability of animal farming. There are several components that can benefit or compromise adequate pregnancy periods. Sheep production is not only a very important economic activity for farmers around the United States, but sheep are also an important medical and surgical model to study human diseases. Our findings suggest that estradiol-17 beta could be involved in acute increased plasma volume early in gestation which can benefit overall gestation. We report that umbilical blood flow decreases upon nutrient restriction in adolescent ewes and does not recover upon realimentation. Finally, we suggest that a similar umbilical blood flow, placental development and plasma volume expansion in twins and singleton pregnancies could be enough to obtain similar birthweights in singletons and twins.
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    The Effects of Late Gestational Exercise on Colostrum Quality and Neonatal Immunoglobulin Absorption
    (North Dakota State University, 2021) Gavette, Juan Simon
    To investigate the effects that late gestational exercise has on ewe performance and colostrum IgG levels, and to evaluate how it impacts neonatal serum IgG absorption and future performance, thirty-two multiparous Dorset ewes were divided into two treatment groups and were housed in individual pens. The treatment group was walked for thirty minutes per day, every other day from the start of the third trimester to lambing. The results indicate that colostrum IgG levels were significantly greater in exercised ewes compared to ewes held in confinement. Increased locomotion impacted pregnant ewe feed intake, body weight, and average daily gain. Gestational exercise did not impact lamb birth weight or weaning weight. There were no significant differences in serum IgG levels amongst lambs after colostrum consumption but there were in serum protein. Further research is needed to better understand how and why gestational exercise increased colostrum IgG levels.
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    Can Hematocrit Levels at Estrus in Dairy Cows and Sheep Be an Indicator for Pregnancy Success?
    (North Dakota State University, 2019) Kelany, Khaled Elaraby
    Despite the major reproductive advances in the livestock industry, prenatal embryonic loss is still one of the major issues that causes substantial economic loss. While there are many tests available to determine pregnancy soon after maternal recognition of pregnancy, most of the prenatal losses are undetectable because it occurs before then. Based on previous research we hypothesized that increased plasma volume around the time of estrus will increase the survivability of the embryo at early stages of gestation. However, our findings indicate that hematocrit levels are not a consistent measurement in determining successful pregnancies.