“Invited review: Sensor technologies for real-time monitoring of the rumen environment.” Journal of Dairy Science Vol. 105 No. 85, 2022. This invited review article, from researchers from the universities of Pennsylvania, Purdue and Virginia Tech, aims at summarizing the current knowledge regarding sensor technologies for real-time monitoring of the rumen environment. The authors say that quantifying digestive and fermentative processes within the rumen environment has been the subject of decades of research; however, they add, the existing research methodologies make it difficult to evaluate processes in a timely manner as well as in different regions of the rumen.
The authors provide some context for this study, explaining that as the global population increases the need for sustainably produced food becomes more important. The Food and Agriculture Organization (FAO) predicts that by 2050 the demand for meat will increase by 73%, and the demand for dairy will increase by 58% over 2011 levels. This trend has led to the intensification of animal production in several countries but, the authors say, more than just intensification, precision feeding and management technologies hold promise as strategies that can be adopted to continue efficiency and productivity trends. Understanding the rumen ecosystem is a key aspect to take advantage of the ability of ruminant animals to feed the growing population and to address the major sources of environmental impact attributed to ruminant production.
For decades, studies about the rumen have been done using fistulated cattle. These are animals that have undergone surgical placement of a cannula to allow direct, experimental access to the animal’s gastrointestinal tract. Although this has increased immensely the knowledge about the rumen, the authors explain that this system has its problems. For example, normally it’s done on a small number of animals, and there are also ethical challenges.
Traditionally, rumen pH has been a major focus of rumen studies because of the relationship between pH and cellulose digestion. Real-time monitoring of rumen pH has been proposed as a critical management tool to address animal health challenges such as ruminal acidosis and to improve understanding of fermentation processes. The technique of measuring rumen pH with probes inserted in the rumen through the rumen fistula has been successful. However, the authors say, this solution is not well suited to other applications because it is impractical to maintain large herds of cannulated cows in production settings.
Currently, the main route of investigation is using oral-ruminal probes. Contemporary, commercially available rumen monitoring systems focus on detecting estrus or heat, detecting the onset of diseases such as SARA and mastitis, and monitoring activity and productivity through indirect means that leverage measured biomarkers (e.g., temperature, pH and activity). Other than these, there is considerable research in other areas, namely expanding the capacity of the sensors for important metabolites such as volatile fatty acids (VFAs; the primary energy source for ruminants) or biomarkers, such as histamine.
The authors go in extensive detail explaining each of these new systems, their potential, advantages and challenges. It is a rather complex subject, due to the dynamic nature of the rumen. They acknowledge this by saying that despite marked progress in sensing technologies for important analytes within the rumen, several limitations to current research prototypes and commercial technologies must be addressed before widespread biomonitoring of the rumen environment is feasible. They summarize these challenges as primarily related to sensor size, sensor life span, sensor selectivity or durability to environmental interference, sensor relevance to the biological range and interpretation of information obtained from sensors. Interestingly, the authors finalize by saying that the final, and perhaps greatest, challenge associated with rumen biosensing comes after the successful development of a sensor: namely, the interpretation of data in order to make actionable decisions.
“Graduate student literature review: Role of pain mitigation on the welfare of dairy calves undergoing disbudding.” Journal of Dairy Science Vol. 105 No. 85, 2022. This literature review from the University of Guelph synthesizes research findings on the pain and welfare of dairy calves undergoing disbudding procedures. The authors explain that disbudding is a painful procedure commonly performed on dairy farms that, when performed without anaesthesia or analgesia (or both together) has been identified as a risk factor for poor calf welfare. They refer to statistics that indicate that in the U.S. 94% of responding dairy farms reported having dehorned animals, and in Canada over 95% of responding producers reported that they disbud their calves. Cattle are typically dehorned or disbudded because horned dairy cattle pose a risk of injury to people as well as to other animals.
The authors explain the difference between disbudding and dehorning. Disbudding is the removal of the horn-forming tissue before its attachment to the skull, whereas dehorning is the removal of the horn after this occurs, typically at 2 to 3 months old. Disbudding is recommended over dehorning because it is less invasive and less painful. The two most used methods for disbudding are cautery (or hot iron) and caustic paste disbudding, with cautery disbudding being the most common. Caustic paste is generally used on younger calves, compared with cautery disbudding, with most Canadian producers doing it before 3 weeks old. In contrast, the authors add, in Canada most producers (67%) using hot-iron disbudding to calves between 3 and 8 weeks old.
The authors say that although the use of pain relief for disbudding has increased over the past decade or so, there are still people in the dairy industry who do not believe pain control for disbudding is necessary, reporting cost of pain relieving as the reason. Also, in North America, producers reported that it is more common not to use pain relief in younger calves, as they believe young calves are less sensitive to pain. However, the authors say there is no evidence supporting this belief.
The authors say that during the healing process, wounds are painful for at least three weeks. Some studies determined that it takes anywhere from three to 13 weeks for cautery disbudding wounds to re-epithelialize, but in these studies calves were fed a restricted amount of milk (less than 6 litres per day). Studies showed that higher levels of milk intake (from 10 to 12 litres per day of milk) are associated with improved calf health and performance as well as reduced healing times after cautery disbudding.
Some of the criteria that researchers use to evaluate pain during these procedures are heart and respiratory rate, eye temperature and cortisol levels. Citing several studies, the authors say that heart rate increase is lessened with the use of a local anaesthetic or an NSAID or both medications together compared with less or no pain control. The use of a local anaesthetic has also been shown to decrease respiratory rate following disbudding, as well as a local anaesthetic with an NSAID. Providing calves with a local anaesthetic for cautery disbudding results in a smaller effect on the change in eye temperature compared with no pain control.
The article concludes that disbudding is a common procedure in the dairy industry and has been well documented to be painful and a significant welfare concern. Pain mitigation can alleviate some of the negative pain-related outcomes associated with the procedure. Researchers have begun to shift focus to better understand the affective state of calves during and following this procedure. Newer research has identified long-term effects of disbudding on the affective and motivational states of calves, and on their biological functioning, including very long healing times (up to 13 weeks). They recommend future research should aim to determine accurate behavioural tests for calves less than 1 week old undergoing disbudding to better understand their experience, further attempt to understand the effects of xylazine sedation for disbudding and potential impacts of providing this medication, and determine more ways to reduce the healing time and pain experienced by the calf after disbudding procedures.
This column brings you information regarding some of the research being done around the world and published in the Journal of Dairy Science. The objective is to bring to light areas of research that may have an immediate practical application on a dairy farm, as well as research that, even though it may not have a practical impact now, could be interesting for its future potential application. The idea is to give a brief overview of select research studies but not go into detail on each topic. Those interested in further in-depth reading can use the citations to find each study.
