Intensive farming practices require a high plane of nutrition, which typically includes high levels of fermentable carbohydrates which can put the animal at risk for developing metabolic disorders, in particular, challenges to rumen stability and sub acute rumen acidosis (SARA).
Different degrees of acidosis appear when the fermentation profile of the rumen is unbalanced by high levels of lactic acid or butyric acid (Castillo-Lopez E. et al., 2014), (Krause K.M., Oetze G. R. 2006), (Enemark J. M. D. 2008), (González L. A. e al., 2012).
Sub Acute Ruminal Acidosis (SARA)
- More common, results from excessive volatile fatty acid (VFA) production that exceeds the ability of the rumen to neutralize and it exceeds the absorption capacity of the ruminal papillae.
- It has been considered that when rumen pH drops below 8 and remains below this threshold for three or more hours within a 24-hours period is at risk for SARA; recent research suggests that relative pH indicators generated from in-dwelling reticulo-rumen pH sensors are more robust for identifying affected animals in a herd and also for comparing SARA risk among studies (Villot et al., 2018) .
- Animals generally have mild diarrhea, lowered dry matter intake and laminitis.
- Can develop into acute acidosis if the pH is never able to recover.
Acute Ruminal Acidosis
- Less common, more severe, usually occurs when pH falls below 5.5.
- Usually associated to a drastic diet change.
- Animals have depressed productivity, go of feed, have elevated heart-rate, diarrhea and may die.
- Severe lactic acidosis may cause irregular feeding behavior and gorging, which creates more spikes of acid production.
| Indicators and risk parameters | General Reasons |
|---|---|
| Decreased animal performance | – Reduced average daily gain and feed conversion ratio may be due to impaired rumen fermentation in beef cattle. – Low milk production, milk fat and a reduced fat/protein ratio may be due to impaired rumen fermentation in lactating dairy cattle (Britt J. S. et al., 2003), (Allen M. S. 1997), (Sauvant D. and Peyraud J. L. 2010). |
| Reduced rumination activity | A lack of ruminating activity may be due to reduced rumen motility during acidosis (Allen M. S. 1997), (Grant R. J. et al.,1990). |
| Locomotion issues | Lame animals can indicate high levels of rumen histamine production and bacteria endotoxin release (Nocek J. E. 1997). |
| Poor rumen fill | An empty rumen can indicate poor rumen efficiency because of irregular intake (Zaaijer D. and Noordhuizen J. P. T. M. 2003). |
| Manure consistency | Liquid feces can indicate poor rumen efficiency due to an increased passage rate, from an imbalanced diet and more lower gut fermentation (Hall M. B. 2002), (Hutjens M. F. 2010), (Zaaijer D. and Noordhuizen J. P. T. M. 2003). |
| Cleanliness score | An increased passage rate from an imbalanced diet and low digestibility can lead to unclean animals. |
| Undigested grains | Undigested processed grains in the feces because of poor rumen efficiency may be due to an increased passage rate due to an imbalanced or low diet digestibility (Hall M. B. 2002). |
| Heat stress | Heat stress (temperature and / or humidity) increases the risks of acidosis and low fiber degradation because: – Eating behavior is negatively affected: cattle prefer to eat during cooler times of the morning and later evening. – Dry matter intake (DMI) is decreased: cattle sort the diet with a lower proportion of forage and higher levels of fermentable carbohydrates. – High loss of saliva (from drooling and open-mouthed breathing) in hot weather decreases the amount of natural buffers to the rumen (Burgos et al., 2011). |
The invisible threat: rumen Acidosis damages rumen wall papillae
Financial impacts
The financial impact of rumen acidosis is staggering.
In lactating dairy cows, economic loss can be attributed to: lower milk fat content (-0.76%), depressed milk production (-10%), poor reproductive performance and increased risk of secondary metabolic disorders. One study estimates the overall impact to the U.S. dairy industry is between $500 million and $1 billion per year (Krause K.M., Oetze G. R. 2006).
Another study estimates sub acute acidosis costs $34,750 per 100 cows (Zebelli Q. et Ametaj B. N. 2009).
In growing and finishing beef cattle, economic loss can be attributed to:
- Lower growth rate (-78g/hd/d; -0.17 lbs/hd/d)
- Impaired feed-to-gain conversion
- Lower meat grades
- increased risk of secondary metabolic health events (Thompson P. N. et al., 2006).
FAQ About Rumen Acidosis
Yes. Acidosis alters the diversity and composition of the rumen microbiota, reducing beneficial bacteria like Prevotella and increasing harmful ones. This microbial imbalance can impair digestion and immune function.
Chronic SARA can lead to liver inflammation, laminitis, reduced milk quality, and increased culling risk. It also triggers systemic inflammation due to damage to the gut lining.
Yes. Emerging strategies include:
- Yeast probiotics to stabilize rumen pH
- Essential oils and plant extracts to modulate fermentation
- Slow-release starches to reduce rapid acid production
- Precision feeding using real-time monitoring tools
Yes. AI-based systems using gas sensors (e.g., CH₄ and CO₂) and deep learning algorithms are being developed to detect early signs of SARA in real time, offering a proactive approach to herd health.
To prevent SARA, it's important to optimize the particle size of the diet. Here are some key recommendations:
- Balanced particle size: The forage particle size should be neither too long nor too short. Longer particles can lead to sorting behavior, where cows selectively eat the more palatable parts of the feed, potentially leading to SARA. Conversely, very short particles can reduce rumen motility and nutrient absorption
- Physically Effective Fiber (peNDF): Ensuring the diet has adequate physically effective fiber is crucial. This helps stimulate chewing and saliva production, which buffers the rumen pH.
- Theoretical Length of Cut (TLC): For corn silage, a TLC of around 19 mm is often recommended. This length helps balance effective fiber and digestibility.
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