Animal & Avian Sciences Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2741
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Item The effect of feeding mixed tocopherol oil on body accumulation and immune cell functions in lactating holstein dairy cows(2017) QU, YANG; Moyes, Kasey M; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Non-α-tocopherol (i.e. β, γ, and δ-tocopherol) supplements are as important as α-tocopherol with regard to maintaining lactating dairy cow health. However, information on non-α-tocopherol bioaccumulation and its effects on immune cell function is not available. A series of experiments were conducted to investigate the effect of mixed tocopherol oil supplement (Tmix; i.e. α, β, γ, and δ-tocopherol) on body accumulation and immune cell functions of the lactating Holstein dairy cow. Tissue, tissue mitochondria, blood and milk were collected from lactating dairy cows to measure the concentration of all four tocopherol isoforms via Tmix supplementation. In addition, polymorphonuclear leukocyte (PMN) were isolated to investigate the effect of Tmix on its function and immune gene expression. In the first experiment, Tmix increased γ-tocopherol concentrations but did not increase the α-tocopherol concentration in three different types of tissues (i.e. liver, mammary gland and muscle) and liver mitochondria. Within those three different types of tissues, liver showed the highest ability to store tocopherol isoforms (i.e. α- and γ-tocopherol) compared to the other two tissues. Also, amounts of α- and γ-tocopherol were detected in liver mitochondria, but limited amounts were detected in mammary gland mitochondria. In the following experiment, Tmix increased γ-tocopherol concentration in milk and blood as determined via every 8 h and daily measurements. Compared to γ-tocopherol, α-tocopherol showed the highest concentration of the tocopherol isoforms in milk and blood. Limited quantities of β- and δ-tocopherol were detected in milk and blood via Tmix supplementation. In the last experiment, Tmix increased PMN chemotaxis function and did not impair the whole blood respiratory burst response of dairy cows, which might be associated with non-α-tocopherol existing in Tmix. Even though Tmix increased the expression of pro-inflammatory genes in PMN, those are needed during the initial immune activation. Overall, the results of the experiments demonstrated that short-term supplementation with Tmix could compensate γ-tocopherol without altering α-tocopherol in dairy cows. The liver showed the highest capability of accumulating tocopherol isoforms compared to the mammary gland and muscle. In addition, Tmix did not harm immune functions or have any apparent effects on animal health in lactating Holstein dairy cows.Item Urea-N Recycling in Lactating Dairy Cows(2007-12-11) Dinh, Sarah; Kohn, Richard A; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study was designed to determine the effect of rumen degradable protein (RDP) and rumen undegradable protein (RUP) on urea-N recycling and microbial N flow. Eight mid-lactation Holstein cows were assigned to a repeated 4 x 4 Latin square. The diets were isoenergetic with RDP and RUP concentrations arranged in a factorial design (10.0 and 12.5% RDP and 5.6 and 8.1% RUP as a percentage of DM). The 10.0% RDP diets resulted in greater milk yield and lower milk protein concentration than the 12.5% RDP diets. High RUP diets tended (P = 0.1) to increase bacterial N flow in the liquid fraction. The NRC 1989 model predicted flow of microbial N and total N from the rumen more accurately than the NRC 2001. The NRC 2001 model predicted a higher RDP requirement and a lower RUP requirement for all four diets compared with the NRC 1989 model. Both models reflect the dietary changes that were intended by increasing the RDP and RUP in a factorial manner. There was no effect of RUP or RDP on the g/d of urea-N transferred from the blood to the gut or returning to the ornithine-urea cycle. However, plasma urea-N (PUN) incorporated into rumen microbial protein tended (P = 0.14) to increase with the low RDP diets. The rate of transfer of PUN to the gut appeared to be independent of PUN concentrations. The gene expression for urea transporters (bUT-B2) in the rumen did not change due to diet. As dietary protein intake increased, a constant amount (g/d), or decreasing fraction (g/g), of PUN was transferred to the gut. The apparent saturation of urea transporters in the gut prevented excess PUN from recycling to the gut on high-protein diets sparing the energy cost for N excretion that would have resulted from a constant percentage of PUN being recycled.