Stress is said to be the relationship between a response and the environmental conditions that caused it. Stress initiates a reaction due to conditions that puts one under a significant amount of pressure, possible threats, or the individual working under high demands (Dobson and Smith 2000). For an animal, stress may be seen as the inability to cope with its environment (Dobson and Smith 2000). Stress can be positive or negative depending on the reaction it generates. Positive stress pushes an individual to do better and try harder. Negative stress is known for limiting an individual’s ability to perform, this can result in decreased fitness (Dobson and Smith 2000). Stress in animals, can be divided into three subcategories, indication of the stressor, biological mechanism against the stressor, and the outcome of the response (Moberg and Mench 2001). The final subcategory allows for the recognition if the response is negative or positive. Often, animals can avoid stress by removing themselves from situations, however animals such as livestock, undergo daily routines and the ability to escape stress is faulted (Moberg and Mench 2001). Although there are implications that livestock do undergo stress, there are little ways to measure these behaviors outside of labs. The central nervous system of the animals emit a different combination of responses to the same stimuli creating difficulties determining the exact indicator of the stress causing events (Moberg and Mench 2001).
When a stressor begins to create health issues for the animal, it is referred to as ‘distress’ (Moberg and Mench 2001). Distress can be seen as non-threatening, “good stress” or a stress response where the animals’ well being is at risk, “bad stress”. In order to truly measure an animals stress level observing all aspects of the animal is important (Moberg and Mench 2001). This can include behavioral response, chemical responses and others. Researchers that performed a study on rats, Rattus, were interested in the chemical changes that affect rats’,behaviors in different environments (Moncek, et al. 2004). Through these findings, they concluded that it is the neuroendocrine regulation that responds to environmental enrichment, indicating chronic stress (Moncek, et al. 2004). Relationships of a stressor and the animals’ welfare can often be seen in the animals hormone levels and the behavioral response.
There are behavioral responses that can be easily observed as well. Dogs, Canis lupus familiaris, behavior was observed while being shown positive and negative stimuli and it was found that dogs lick their mouths more frequently when shown a negative stimulus (angry facial expressions) compared to positive stimuli or drapery (Albuquerque, et al. 2018). This suggests that dogs may be able to recognize human expression which is important for human research in stress and understanding displacement activities (Albuquerque, et al. 2018). Although emotions are subjective states and cannot be measured directly in animals, an index can be made for species-specific behaviors to interpret them appropriately (Hemsworth, et al. 2013).
Proudfoot and Habing (2015) argued that the type of environment and how routines are executed can produce stress behavior in livestock. Further they discovered that social isolation, crowding, and social instability are all key factors to assessing stress. After analyzing group housing of pregnant pigs, Sus, evidence of increased aggression, injuries, and food competition could be seen (Hemsworth, et al. 2013). Therefore, stress responses can be described to be both internal and external responses due to hormone levels and behavioral changes.
Cows, Bos taurus, show stress in various ways. The most common represented response to stress is reduced eating (Tucker et. al 2008). Cows experience stress from milking and this can affect their udders (Giesecke 1985). Cows inability to cope to their milking environments heightens the risk for infection in the udder (Giesecke 1985). As Pragna et. al (2016) stated that stress in cows can cause a reduction in milk production, this agrees with Nielsen (2015) that duration of lactation is directly proportional to production, cows lactate less and produce more milk when under stress. With an increase of milk production the average lifespan of the cow decreases (Stefani et al. 2018).
In relation to stress, behaviors can be seen in observations through milking, relocating and other experiments revolving around cows put in stressful conditions. Behaviors corresponding with milking can vary depending on the method being used. Hopster et al. (2002) performed an experiment on cows that were milked using an automatic milking system versus cows being milked conventionally to determine the amount of steps and kicks, as well as head position while milking. Behavioral events to stress can be seen in cows while being milked, regardless of the method used to milk them.
Therefore, an interesting question to discuss is, how does milking cows influence stress? This question is interesting because observing cows at different times such as before, during and after milking can lead to key insight on determining stress behaviors. We first hypothesize that milking cows increase behaviors of stress. To test this hypothesis, we predict that during the act of milking, a cow will show the most behaviors of stress when compared to before and after milking. Another hypothesis for how milking affects behavior would be, cows become stressed when anticipating being milked. If this is so, we would expect that when a cow is getting prepared for milking, it will show the most amount of stress-linked behaviors when compared to before and after milking. Lastly our final hypothesis would be, cows’ level of stress reduces after milking. Our prediction to test this hypothesis is, after getting milked, the cow will show the least amount of stressful events when compared to before and after milking.
In this study, the effects of milking on cows was looked at. Our first hypothesis and prediction that during the act of milking, cows will show the most stress-linked behaviors when compared to each milking stage, was not supported by the data. Our second hypothesis was that cows would become stressed when anticipating being milked. If this was the case, cows would start to show the highest amount of stressful events compared to the other stages. The low p- value depicts that our data collected did not support this hypothesis, showing that there was no significance in stressful behaviors between milking stages when compared to each other. Lastly, it was hypothesized that cows’ level of stress would reduce after milking. A prediction was made that after getting milked, cows would show the least amount of stressful events when compared to before and during milking. Cows did exhibit the least amounts of stressful events after milking however the difference was not significant and the hypothesis was rejected. The data shows that there is no significance between stage of milking and number of stressful events the cow shows. From these findings, we can conclude that in our study there was no significant evidence that milking effects the number of stressful events at each milking stage (before, during, after) in holstein dairy cows at the Fairchild farm.
There are different methods of milking as well as different ways to record stressful events. Hopster et al. (2002) compared cows that were milked using an automatic milking system to cows being milked conventionally in order to record stress events due to different methods of milking. Contrary to our findings this study found that the presence of behavioral tics due to stress could be seen in cows while being milked regardless of milking method. Our data showed that there was no relationship between the milking stage and the stress events seen, however Hopster et al. (2002) argues that stress events would always be present in the “during” milking stage which was also insignificantly represented in our data. Hopster et al. (2002) was able to observe the cows well before the milking process, which could be a reason why our data contradicts their findings since we only observed the cows fifteen minutes beforehand. Although our study did not compare the methods of milking, with machine versus conventionally, using Hopster et al. (2002) techniques for both conventional milking and automatic as well as expanding Hopster et al. (2002) ethogram could be a future study we perform.
When referring to Moberg and Mench (2001), the way they describe animal ‘distress’ can be connected to what the cows exhibit during milking. Because the cows are experiencing milking everyday and it may cause stress. The animals’ central nervous system elicits a difference combination of stress responses, to the same stimuli, that are physically seen as a behavioral response. The cow may be stressed caused by milking, but due to its varying responses, the physical signs may or may not occur (Moberg and Mench 2001).
There are several errors that could have led to why our hypotheses may not have been supported. Prior to the during milking interval , the cows in study were held in a big groups where behavioral events were not recorded, although this small crowded room seemed to elicit a lot of stress. Another biological reason for error could be that the cows were milked heavily on this schedule and could be habituated to the entire milking process. We also did not take into account if the group was affected with stress due to other groups. The group chosen for our study was the first to go through the the milking process. We observed other groups getting agitated while our group in study were getting called into the smaller holding room. For instance group 3 hearing group 1 and 2 getting called in and the cows in group 3 exhibiting behavioral stress events.
Another error, that we had no control over, could have occured. Another study was going on while we were conducting ours leading to a few cows having rumen cannulas. A rumen cannula is a port that is attached to the cows abdomen to access their stomach with ease. Only two cows with this device were included in our study in which we investigated to see if this may cause a difference in behavioral events between cows with the rumen cannula compared to those without. Our data did not show a significant difference between those with and without a rumen cannula however a larger sample size may be needed to be able to come to a conclusion about these differing individuals. The results of these cows were averaged with those of the cows without the rumen cannulas, therefore we didn’t see any error involving these particular cows in our study. We also tried to take age into consideration but again were working with a very small sample size. The results of the regression show no relationship to age and number of stressful events.
When conducting our study, we went on two different days. Each time, there was a different milk handler who attached the milking machine to the cows’ utters. Observing if cows react differently to different handlers could be another future study. Cows may be able to sense if certain employees are more tense, stressed, or at ease compared to others which then may increase or decrease their levels of stress while being milked. Another study can be done strictly comparing those with rumen cannulas against those who do not while getting milked, seeing if there is any differences between the two. Studies to try and understand if cows are being unfairly treated in dairy farms, where they are subject to an intense routines of milking, verses privately owned smaller farms should be conducted. This is the most important study to conduct since the wellbeing of all animals is the principal concern of this study.
Domestic cattle provide milk, meat, leather, and labor for humans so their wellbeing and mental health is a large concern of ours. Dairy cows provide an essential source of protein and calcium for their calves as well as for us. By comparing stress levels to different stimuli we can determine how to reduce the amount of stress exhibited by domestic cows which in turn will allow more productivity. With the increasing consumer demands, farmers are required to increase their livestock production and management. Income growth and urbanization are making this a difficult task though. With less than 26% of potential agricultural land left in North America, farms are shrinking and disappearing while the population is increasing by 1.09% per year (Food and Agriculture Organization, 2018). Cattle meat production alone increased from 28 million tons per year to 68 million tons in 2014 (Knight and Chalise 2018). With the increasing demand, farmers are forced to prioritize production over ethical animal welfare. With this being said, change in behaviors during the time leading up to stressful events could lead to a change in agricultural advancements. Cows that are less stressed produce more milk that contains less fat (Pragna et al. 2016). The reduction of stress also allows cows to better care for their young and increases survival rate (Al-Katanani 2002). With this knowledge, additional funding and research could be put into determining if machine milking is the leading cause compared to other methods.