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Browsing by Author "Rhoads, Michelle L."

Now showing 1 - 4 of 4
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    Heat Stress Increases Mammary Epithelial Cells and Reduces Viable Immune Cells in Milk of Dairy Cows
    Lengi, Andrea J.; Stewart, Jacob W.; Makris, Melissa; Rhoads, Michelle L.; Corl, Benjamin A. (MDPI, 2022-10-17)
    Somatic cells normally found in milk are generally either immune cells such as lymphocytes, monocytes and granulocytes, or mammary epithelial cells. The number and composition of somatic cells in milk can be influenced by a variety of factors, including infection and temperature-humidity index. The objective of this study was to determine the specific effects of heat stress on the cellular composition of the somatic cell population in milk. We used flow cytometry to ascertain the concentration and viability of mammary epithelial cells, T cells, monocyte/macrophage, and granulocytes in milk from cows maintained under heat stressed conditions compared to thermoneutral conditions. We found a significant 10% increase in the natural log concentration of epithelial cells in the milk of heat stressed cows compared to thermoneutral cows (9.3 vs. 8.4 ln(cells/mL, p = 0.02)). We also found a 12% decrease in the log concentration of live CD45+ cells (p = 0.04), and a 17% decrease in the log concentration of live CD45+ granulocytes (p = 0.04). No changes were found in CD3+CD45+ cells or CD14+CD45+ cells, however, we noted an unusual population of CD14+CD45− cells that showed significant increases of 10% (p = 0.03) and 12% (p = 0.01) in the log concentration of total and dead cells, respectively, under heat stressed conditions. These results suggest that heat stress influences the relative populations and viability of some somatic cells populations in milk. Increased losses of secretory epithelial cells into milk could have implications for milk production, and fewer viable immune cells could negatively impact the immunocompetence of dairy cows under heat stress.
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    Human continuous glucose monitors for measurement of glucose in dairy cows
    Byrd, M.K.H.; Arneson, A.G.; Soffa, D.R.; Stewart, J.W.; Rhoads, Michelle L. (Elsevier, 2022)
    The purpose of this study was to determine whether interstitial glucose measurements collected by sensors designed for humans could replace blood-based glucose measurements in dairy cows. Lactating Holstein cows (n = 21) were fit with indwelling jugular catheters, as well as FreeStyle Libre (FSL; Abbott) or Dexcom G6 (DexCom Inc.) interstitial glucose monitors secured either near their ears or on their upper rear legs. Functional longevity of the sensors was greatest for those sensors secured near the ear. Blood glucose concentrations were most closely correlated with interstitial measurements from the FSL ear (r = 0.82) and the Dexcom G6 ear (r = 0.71), but accuracy was low. Both ear sensors detected an increase in glucose concentrations following a bolus dose but neither produced results exactly matching the blood glucose measurements. The results of this work indicate that both sensors can detect large changes in glucose, but neither is currently capable of replacing blood-based glucose measurements in dairy cows.
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    Influences of Supplementing Selective Members of the Interleukin-6 Cytokine Family on Bovine Oocyte Competency
    McKinley, Endya; Speckhart, Savannah L.; Keane, Jessica A.; Oliver, Mary A.; Rhoads, Michelle L.; Edwards, J. Lannett; Biase, Fernando H.; Ealy, Alan D. (MDPI, 2023-12-21)
    This work explored whether supplementing selective members of the interleukin-6 (IL6) cytokine family during in vitro bovine oocyte maturation affects maturation success, cumulus–oocyte complex (COC) gene expression, fertilization success, and embryo development potential. Human recombinant proteins for IL6, IL11, and leukemia inhibitory factor (LIF) were supplemented to COCs during the maturation period, then fertilization and embryo culture commenced without further cytokine supplementation. The first study determined that none of these cytokines influenced the rate that oocytes achieved arrest at meiosis II. The second study identified that LIF and IL11 supplementation increases AREG transcript abundance. Supplementation with IL6 supplementation did not affect AREG abundance but reduced HAS2 transcript abundance. Several other transcriptional markers of oocyte competency were not affected by any of the cytokines. The third study determined that supplementing these cytokines during maturation did not influence fertilization success, but either LIF or IL11 supplementation increased blastocyst development. No effect of IL6 supplementation on subsequent blastocyst development was detected. The fourth experiment explored whether each cytokine treatment affects the post-thaw survivability of cryopreserved IVP blastocysts. None of the cytokines supplemented during oocyte maturation produced any positive effects on post-thaw blastocyst re-expansion and hatching. In conclusion, these outcomes implicate IL11 and LIF as potentially useful supplements for improving bovine oocyte competency.
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    Plasma γ-Aminobutyric Acid (GABA) Concentrations in Lactating Holstein Cows during Thermoneutral and Heat Stress Conditions and Their Relationships with Circulating Glucose, Insulin and Progesterone Levels
    Arneson, Alicia G.; Stewart, Jacob W.; Byrd, MaryKate H.; Perry, George A.; Rhoads, Michelle L. (MDPI, 2024-03-21)
    Heat-stressed lactating dairy cattle exhibit unique metabolic symptoms, many of which are undoubtedly involved in heat-induced subfertility. Because of its known systemic effects, we hypothesized that γ-aminobutyric acid (GABA) participates in the regulation of insulin and progesterone during heat stress. Multiparous lactating Holstein cows (n = 6) were studied during four experimental periods: (1) thermoneutral (TN; d 1–5), (2) TN + hyperinsulinemic–hypoglycemic clamp (d 6–10), (3) heat stress (HS; d 16–20), and (4) HS + euglycemic clamp (d 21–25). Blood samples were collected once daily via coccygeal venipuncture into heparinized evacuated tubes. Analysis of GABA concentrations from all four treatment periods yielded no differences. In direct comparison to TN concentrations, plasma GABA tended to decrease during the HS period (16.57 ± 2.64 vs. 13.87 ± 2.28 ng/mL, respectively, p = 0.06). Both milk production and plasma insulin were moderately correlated with plasma GABA (r = 0.35, p < 0.01; r = −0.32, p < 0.01). Plasma progesterone was correlated with plasma GABA concentrations during TN but not HS periods. These results are the first to indicate that peripheral GABA could be involved in the regulation of factors known to affect production and reproduction during heat stress. More research is needed to determine its precise role(s).