Q#1. What is the species name of the model/study organism?
The species name for an Angus feedlot calf is Pos (primigenius) taurus (“Angus”, 2018).
Q#2. Intellectual merit and broader impact: A) Why did the authors feel this research was important enough to spend time and money doing it? B) Is there an economical, environmental, medical, health, or a combination of reasons that makes this research valuable?
In P. (primigenius) taurus, a diet restricted in vitamin A is often implemented in cattle/dairy farms used for beef production to improve the quality and marbling of the meat being sold for consumption. Studies have been done previously to show the effects on immune system responses in P. (primigenius) taurus and vitamin A. However, those tests didn’t specifically target the pathogens/diseases themselves. The Bovine coronavirus disease is one that occurs frequently in P. (primigenius) taurus and is a problem for cattle/dairy farms seeking to produce quality beef. The lack of current knowledge on the nutritional effects of vitamin A on immune responses to this disease is what lead the researchers to conduct this experiment.
This research is valuable from an economical standpoint because the results of this research could cause beef producers to have to re-evaluate how to produce higher quality beef if the low vitamin A diet they are currently giving P. (primigenius) taurus is a contributing factor to higher rate of disease among the species. The alternatives they may have to choose could be more costly or time consuming. In turn, this could effect the beef marketplace by making high quality beef harder to attain as well as driving up the costs for both the public and industries that use beef such as restaurants.
Q#3. What is the major question and/or hypothesis studied in the journal article?
The major question of this article is how vitamin A content in the diets of P. (primigenius) taurus (dairy and feedlot calves) would effect antibody responses to a vaccine created to prevent the disease of Bovine coronavirus in the species. The major hypothesis that was studied in this journal article was that diets that were low in vitamin A would prevent vaccines meant for Bovine coronavirus from being effective.
Q#4. Sampling for the study: A. Where did they sample? B. How did they sample? C. Number of samples taken?
The sample for this study was conducted on a feedlot in Wooster, Ohio, at The Ohio State University Beef Research Center.
Researchers sampled the calves by dividing them into two categories: one group which was fed a diet high in vitamin A throughout the study and one group which was fed a diet lower in vitamin A throughout the study. There were 20 calves assigned to each group for a total of 40 calves in the study. This study was conducted over a period of 140 days, or about 5 months. All calves were given a vaccine for the Bovine coronavirus on days 112 and then a second dose on day 126. Throughout this study, samples were collected by means of nasal swab, fecal sampling, and blood sampling. These samples were tested and analyzed using a few different statistical methods to be able to determine the concentration of vitamin A in the blood serum in the calves as well as using liquid chromatography to identify the presence of vitamin A and antibodies in the blood that fight against the Bovine coronavirus. The blood serum of an animal can contain many antibodies used for the function of immunity and defense in the body’s system (Encyclopedia Britannica online, n.d.).
The calves were fed daily either the high vitamin A or low vitamin A diet based on the group they were randomly assigned. The vaccine was administered two times throughout the study period. The samples of nasal swab, fecal samples, and blood samples were taken five times throughout this study; on days 0, 4, 35, 112, and 140.
Q#5. Choose one experiment from the study: A. Describe the experiment. B. What are the predictor and response variables for this experiment? C. What evidence did the experiment produce? D. Describe how the evidence supported/answered the major hypothesis/question?
One experiment done in the study involved using high-performance liquid chromatography to analyze the concentrations of the vitamin A in the serum in the blood of the calves. High-performance liquid chromatography is used to separate different compounds in a solute for analyzation (Libretexts, 2018). This was done by randomly selecting 10 calves from each group (high vitamin A diet or low vitamin A diet) and taking blood samples every 28 days during the experiment.
These blood samples were taken via the jugular vein of the calves and wrapped in aluminum foil so that light would not have an effect on the vitamin A concentrations in the blood. All of the following procedures of this experiment had to be performed in the dark to prevent a skew of data caused by the light on the serum. These samples were stored on ice until they were to be evaluated. Before being analyzed, the serum was extracted from the blood with the solvent hexane. The serum was dried out and then rehydrated before being put into the liquid chromatography system.
The data collected about the concentration of vitamin A in the blood gathered from this experiment was then analyzed using statistical analysis. This statistical analysis was used to create graphs showing the change in data over time and giving the researchers more of a frame of reference to be able to evaluate their results.
The predictor variables for this study were the High/Low vitamin A diets, as well as time (the blood samples obtained every 28 days). The response variable was the concentration of retinol (vitamin A) in the serum of the blood.
The evidence that this experiment produced includes noticing that there was a significant difference in the concentration of vitamin A found in the blood over time between the calves fed a high vitamin A diet and those fed a low vitamin A diet. The calves that were fed the high vitamin A diet had an increase in vitamin A concentration the first 28 days of the experiment. The calves that were fed the low vitamin A diet also had a big increase in vitamin A concentration during the first 28 days, as well as the second 28 days of the experiment. The difference can be seen dramatically, however, during the last half of the experiment. In the calves fed the high vitamin A diet, from days 28 until the end of the experiment, the concentration of serum vitamin A in the blood maintained a fairly steady plateau with only a slight decrease towards the end. On the other hand, the calves fed the low vitamin A diet started showing a decrease in concentration of serum vitamin A in the blood from days 56-112 and then showed a dramatic drop in concentration from days 112 to the end of the experiment. Although there was not a huge amount of statistical significance until day 112 in differences, it is important to note that day 112 was the day the initial vaccination was administered for both groups, so this could be very important in determining the effectiveness of the vaccine. This experiment also gave a reference for which to examine the other experiments in this study, especially regarding the amount of antibodies present in the blood that could be effecting the immunization effects of the vaccine. For example, because the dramatic difference was seen in vitamin A concentration in the serum of the blood from days 112-140, these days could be examined further in regards to other experiments done to test for the presence of antibodies in the system. These tests confirmed what was seen in the vitamin A concentration trends and showed that in calves that were fed a low vitamin A diet, the IgG1 (one of the main antibodies providing immune defense), was less present, therefore less effective (Durani, 2014).
This evidence did support the major hypothesis of the study which is that there is a correlation between vitamin A and antibodies and that a diet low in vitamin A would negatively effect the antibodies’ effectiveness against the vaccine for Bovine coronavirus. This hypothesis was supported because of the finding that lower amounts of vitamin A concentration were found in the calves that were fed the low vitamin A diet after the administration of the vaccine than in the calves that were fed the high vitamin A diet. It was also supported because of the finding that in the calves fed the lower amounts of vitamin A, the IgG1 antibody showed up in a much less amount than in the calves fed a high vitamin A diet. This shows a correlation and a parallel between the amounts of vitamin A in the blood and the amount of fighting antibodies. It mainly shows that higher levels of vitamin A can be associated with higher levels of antibodies, and thus an increase in immune defense against Bovine coronavirus is assumed. It also shows that lower levels of vitamin A can be associated with lesser levels of antibodies, which causes a higher risk, and less defense against Bovine coronavirus. These things strongly support the hypothesis that a low vitamin A diet limits antibody responses to vaccines. However, although the evidence supports the hypothesis, it is very evident that much more testing needs to be done to further support this hypothesis and come to a conclusion that could effect the beef industry greatly. One of the ways that this study does not fully support the hypothesis is that the conditions under which the study was run are not necessarily the conditions that are normal to the species. For example, calves might normally be exposed to a much bigger population which can effect spread of diseases. The environmental conditions can also vary from farm to farm. The results of the study might have been different if under different conditions which is a reason further testing needs to be done. Although this study shows a correlation supporting the hypothesis, this was the first study conducted for these specific factors, and also is only specific to Bovine coronavirus vaccines and not any other disease vaccines.
Q#6. What was the major conclusion of the study?
One of the major conclusions of this study is that there is still a lot of work to be done regarding this area of vitamin A in the diet of feedlot calves having an impact on the effectiveness of vaccines. At the end of the study, it could be concluded that low vitamin A diets MAY have an effect on inhibiting vaccines from working properly and cause more susceptibility to diseases. However, there still seemed to be too many other factors that could be attributing to the ineffectiveness of the vaccines to make a direct correlation in that way. This study did conclude that a diet in feedlot calves that is higher in vitamin A significantly made an impact on antibody responses to vaccines, so a positive correlation could be made. The main point made at the end of this study was that this was the first study done to evaluate the impact of vitamin A on antibody responses to the Bovine coronavirus vaccine in the feedlot calves so more studies would need to be conducted to investigate this matter further. This could be good news for many farmers and beef cattle raisers who are counting on feeding the animals low vitamin A diets to improve the quality of their product.