October 17, 2018
Lallemand conference deals with multi-dimension aspects of acidosis, rumen health
Professor Giulio Cozzi from the University of Padova, who chaired the seminar, showed how the number of scientific publications on the topic has increased over the past decade.
Today, a growing body of scientific data makes the definition of acidosis more complex, although better understood. Nevertheless, the conference established that acidosis is a multi-factorial challenge, which originates in the rumen as a microbial imbalance and has several effects on the homeostasis of the entire gastrointestinal tract, as well as on host physiology and behavior.
Practical outcomes were also discussed in terms of feeding management and nutrition to help mitigate the risks at the farm level.
Diagnostics: More than just pH
Sub acute rumen acidosis (SARA) is a disorder of the rumen microbial ecosystem. Rumen pH is a classic indicator of SARA.
Research has shown that rumen pH must not be considered as an absolute, or average, value but as a dynamic dimension, according to Lallemand.
Currently, the development of new wireless sensor technologies (rumen pH and temperature boluses) offers new opportunities for early detection of rumen health risks on the farm. Thanks to this technology, Dr.Clothilde Villot from INRA-UMRH, France, had developed a new mathematical approach that takes into account individual variabilities. This new tool complements existing parameters.
The conference ended on a round table discussion moderatedby Prof. G. Cozzi, from University of Padova.
However, it is important to keep in mind that average rumen pH (time under low pH (5.6), etc) are not the only parameters. Other indicators of rumen health problems should be monitored, such as feeding and rumination behaviors.
Risk factors for acidosis
Many changes at the farm level, big or small, represent stresses that can potentially impact the rumen environment and its microbial ecosystem. The areas undergoing change include diet, transportation, pig pens, feeding transitions, weaning and calving. These factors could contribute to metabolic imbalance.
Dr.Alex Bach from IRTAin Spain focused on a particular challenge for the rumen: The transition from the dry to the lactating diet in the dairy cow.
Using endoscopic biopsy collection, Dr Bach's team recently looked at the impact of transition on the gene expression of immune biomarkers and rumen wall integrity, showing how transition weakens tight junctions in the rumen epithelium, thus increasing its permeability, and with detrimental effects on rumen wall inflammation.
Dr. Trevor de Vries from the University of Guelph, Canada, also showed that it is not only about what the cows eat but how they eat. Feeding behavior is very important; it is not only about total dry matter intake but also meals duration and frequency - not also forgetting rumination activity.
In addition, particle size should be optimal — not too short for proper rumen function, but not too long as well in order to avoid sorting. All these behavioral parameters are becoming increasingly easy to monitor thanks to new technologies like rumination collars.
In the near future, better monitoring of feeding behavior would allow early detection of digestive issues on the farm for better health management and prevention of SARA.
The vicious cycle of SARA: What happens in the rumen and beyond
Thanks to new '-omics' and next generation sequencing technologies, the rumen microbial ecosystem is increasingly well described and the complex relationships between the host and its microbial ecosystem is better documented.
Dr. Leluo Guan from University of Alberta, Canada, stressed the complexity of the multi-layered rumen wall and the associated microbiota, also called epimural microbiota, whose function is still being scrutinised.
The rumen wall plays key metabolic functions including nutrient absorption and energy metabolism as well as important barrier functions, thus contributing to the balancing of the rumen environment.
A poor rumen environment is detrimental to the rumen barrier effect and nutrient absorption capacity. Histology demonstrates that acidosis weakens the epithelium of ruminal papillae. Dr. Greg Penner from the University of Saskatchewan, Canada, described the acidosis cascade: low rumen pH increases rumen fluid osmolality and rumen wall permeability (leaky epithelium), which, in turn, leads to the passage of endotoxins in the blood and potentially induces systemic inflammation.
As Dr. Bach reminded the audience, SARA has a negative impact on feeding behavior, rumination patterns and total feed intake, altogether leading to lower milk solids.
Prevention rather than cure
As the causes are multiple, so are the solutions.
SARA is not - strictly speaking - a disease, with a distinct causative agent. Instead, it is a multi-factorial disorder.
Various solutions and strategies were discussed during the seminar. Certainly, early detection and prevention remain the best options. For now, the recommended measures are:
Diet structure: Provide sufficient physically effective forage, which will promote positive behavioral patterns - slower consumption of feed, in smaller and more frequent meals per day. This should also avoid sorting, and, as a result of greater fibre content and particle size, increase rumination. (T. de Vries).
Feeding the bugs: Dr. Bach added that the diet should be formulated not only for the cow but also for the microorganisms of the rumen. Appropriate fiber size and content will not only influence cow nutrient uptake but also the rate of fermentation.
Feed additives: Dr. Helen Golder from Scibus in Australia discussed the benefits of feed additives, which are affected by local authorisations on antibiotics (outside EU), buffers, live yeasts or direct-fed microbials (DFM) and enzymes.
Several results were presented, showing how rumen modifying live yeast has a positive effect on various rumen health indictors including rumen pH and rumen pH variations, inflammatory signals (histamine), feeding behavior (Bach, De Vries), and rumination patterns.
IRTA's recent trial with rumen endoscopy also showed that the ruminant specific live yeast Saccharomyces cerevisiae CNCM I-1077 helps the rumen better prepare for the stress of transition and calving (reinforcement of the epithelium tight junctions, lower rumen inflammatory status).
A better understanding of the rumen microbial ecosystems and tight interactions with the host, coupled with the development of new wireless sensors technologies (rumen pH and temperature boluses, rumination collars, etc.) on the farm offers new opportunities for defining visible criteria and allow early detection of rumen health risks and early intervention through precision feeding systems, Lallemand said.