Unraveling the role of zinc transporters in healthy and respiratory disease challenged feedlot steers: Insights into zinc status assessment
Bibliographic record
Abstract
Zinc (Zn) is an essential micronutrient that impacts all aspects of immune function and overall health in humans and animals, particularly in cattle. In calves, marginal Zn deficiency can lead to suboptimal growth and increased susceptibility to respiratory disease. However, in contrast to other trace minerals such as copper, tissue and plasma concentrations of Zn do not change readily in conditions of supplementation or marginal deficiency. Therefore, this thesis explores the expression dynamics of the Zn transporter machinery in bovine immune cells under homeostasis, in conditions of high Zn supplementation or during a respiratory infection in feedlot steers. Chapter 2 provides an in-depth exploration of Zn homeostasis, including its impact on immune function, metabolism, Zn transporters, and metallothioneins (MTs) in healthy and sick animals, with a focus on cattle experiencing bovine respiratory disease (BRD). In addition, this section covers the impact of Zn on the severity of BRD, commonly caused by a combination of viral and bacterial pathogens, such as bovine respiratory syncytial virus (BRSV), followed by secondary bacterial pathogens such as Mannheimia haemolytica (MH). In the first study (Chapter 3), eighteen Angus crossbred steers (261 ± 14 kg) were blocked by body weight and randomly assigned to two dietary treatments: no supplemental Zn (control) or supplemented with 150 mg ZnSO4/kg DM (HiZn). The analyzed Zn concentration for the control diet was 58 mg Zn/kg DM, and HiZn was 207 mg Zn/kg DM. This study investigated the effects of dietary Zn supplementation on labile Zn concentration and Zn transporter gene expression in circulating immune cells isolated from healthy feedlot steers. Labile Zn levels (based on FluoZin-3 fluorescence) in innate and adaptive immune cells were significantly altered in steers fed the HiZn diet. Steers supplemented with the HiZn diet had modulated Zn transporter expression in sort-purified resting immune cells, particularly in B cells, and CD8 and CD4 T cells. The second study evaluated the effects of a BRSV-MH coinfection on the gene expression of Zn transporters and MTs in whole blood (WB), cells from the nasopharynx (NPS), and bronchoalveolar lavages (BAL). A secondary objective was to observe the impact of intranasally treated Zn and vitamin A (VA) on the expression of these transporters. Forty-eight Angus-cross steers (333 ± 4.2 kg) were randomly assigned into four intranasal (IN) treatment groups (n = 12/group); control, IN VA, IN Zn, or IN VA and Zn combined (VA/Zn). Steers were trucked for 6 h on d (-1), aerosol inoculated with a BRSV on d 0, treated with IN treatments on d 4, followed 24 h later by intratracheal infection with MH. WB and NPS were collected on d 0, 5, and 7, and BAL was collected on d 0 and 7. Steers infected with BRSV infection had higher expression of most ZIPs and ZnTs in NPS by d 5, while in the peripheral blood compartment, expression patterns varied. MH infection downregulated the expression of most ZIPs and ZnTs in NPS and increased most ZIPs in WB and BAL. Interestingly, MT1A and MT2A expression decreased in IN Zn-treated steers on d 5 of viral infection (24 hours after IN treatment). This study highlights the impact of respiratory infection on the local and systemic expression of Zn transporter machinery and suggests that evaluation of Zn transporter expression may be useful to assess Zn status in BRD-affected animals. In conclusion, the findings from both studies highlight the significance of maintaining optimal Zn intake and status for proper immune function and provide insights into Zn deficiency, supplementation, and their impact on immune responses in cattle experiencing BRD. While the studies presented in this thesis offer valuable insights into the effect Zn supplementation has on labile Zn concentration and Zn transporter gene expression in both healthy cattle and cattle experiencing BRD, further research is needed to explore the potential of labile Zn, as well as Zn transporter and MT gene expression for better representation of an animal's Zn status. Such research would greatly benefit the feedlot industry in identifying proper Zn diet requirements for animals responding to respiratory disease, ultimately the negative consequences seen in BRD cases in feedlot settings.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".