The Benefit of Rumen Protected Glycerol Over Normal Liquid Glycerol

Introduction

Feeding dairy cows’ liquid glycerol is a common strategy to avoid ketosis. A condition which occurs when the cow mobilises body fat to satisfy her energy requirements in volumes which exceed the capacity of the liver to convert the fat into glucose (energy).

She mobilises body fat within early lactation to satisfy her increasing energy requirements, which are largely driven by milk production. Around the point of calving feed intake is naturally depressed, so the cow is often unable to physically consume enough feed to meet her increasing energy requirements. This is a condition known as negative energy balance as illustrated in Figure 1, where her energy requirements exceed her energy intake, this condition can last up to 20 weeks. Minimising the “energy gap” is important for avoidance of ketosis and maintaining health, production & profitability.

 

Figure 1 Energy balance of dairy cows from gestation to lactation adapted from Hoeij, (2017).

Why glycerol can be effective in alleviating ketosis

Glycerol can be effective in aiding to alleviate ketosis because it’s a very efficient glucose precursor. The metabolic pathway of glycerol is much closer to glucose than other major precursors for gluconeogenesis, such as propionate, lactate and amino acids (McDonald et al., 2011). Compared to propionate conversion of glycerol to glucose is only a 3-step process, whereas propionate to glucose is a 6-step process as shown in Figure 2. This means that glycerol is converted to glucose at a higher metabolic efficiency, using less energy intermediates which reduces the energy cost and nutrient requirement to the cow to synthesise the glucose from glycerol. Ultimately, this increases blood glucose levels and improves metabolism.

Figure 2 Major pathways of gluconeogenesis in cattle adapted from McDonald et al., (2011).

When cattle use their body fat for energy this can also commonly reduce the cow’s appetite. Therefore, by supplying glycerol and increasing blood glucose levels this will reduce the requirement for the breakdown of fat for energy and subsequently support feed intake (Allen et al., 2003).

Feeding liquid glycerol in a rumen available form reduces the effectiveness 

Whilst feeding and particularly drenching glycerol has some proven efficacy, studies have shown that delivering liquid glycerol into the rumen significantly reduces the effectiveness for several reasons.

Glycerol is rapidly fermentable within the rumen meaning that:

• Typically, most of the glycerol fed is fermented by rumen microbes into propionic and butyric acids, often at the expense of acetate which can contribute to reduced milk fat levels
• A majority of the butyric acid subsequently leaves the rumen as beta hydroxybutyrate a ketone body, contributing to ketosis further
• Due to the rapid fermentation of the glycerol energy is lost as gas in the form of carbon dioxide and methane
• Some studies have established that glycerol can reduce rumen pH levels increasing the risk of ruminal acidosis at high doses
• Findings regarding the ability of the rumen to absorb glycerol prior to fermentation by rumen microbes are mixed, although some suggest that only 10% of the total amount fed can escape the rumen unaltered (Kristensen and Raun, 2007)

Within a 2015 study, Piontoni and Allen infused glycerol either into the rumen or abomasum (this simulates rumen protection). They found that infusing glycerol into the abomasum instead of the rumen was more effective in increasing blood glucose levels, indicating better energy supply when the glycerol is not released within the rumen.

It’s clear from research that feeding glycerol in a way that it remains unaltered within the rumen will offer better and more consistent results. Hippen et al., (2008) stated that to be a glucogenic precursor glycerol must be able to bypass the rumen. That’s why the glycerol in Glycal Forte® is rumen protected.

 

How it works

• The glycerol in Glycal Forte® has been refined into a free-flowing powder that’s easier to handle and disperses well through the TMR
• The glycerol within Glycal Forte® is protected within a calcium glycerol complex and remains rumen inert (doesn’t break down) at a desirable non acidic rumen pH level
• At an acidic rumen pH level Glycal Forte® does break down within the rumen to release acid-neutralising anions, but only when rumen pH is to low, i.e. on-demand. The lower the pH the more anions are released. This increases the rumen pH avoiding acidosis to maintain optimum rumen performance and allow bypass of the complex as the cow continues to feed throughout the day
• As the cow continues to feed, the Glycal Forte® bypasses the rumen where the glycerol is released within the abomasum and subsequently enters the liver via the portal vein to provide extra energy

The results speak for themselves

Within in vivo on farm trials Glycal Forte® has been shown on multiple occasions to:

• Increase milk yield
• Increase feed intakes
• Decrease body condition loss
• Increase pregnancy rates
• Maintain optimal rumen pH avoiding acidosis (measured by pH monitoring boluses)
• Improve metabolic profile
• Reduce ketosis cases

Within in vitro trials Glycal Forte® has been shown to:

• Increase rumen microbial population
• Increase feed dry matter digestibility
• Decompose mycotoxins and kill moulds
• Eliminate endotoxins (cause of systemic inflammation in transition dairy cows)

To request any further information email connor.smith@bimeda.com

References

Allen, M.S., Bradford, B.J. and Oba, M. 2009. Board-invited review: The hepatic oxidation theory of the control of feed intake and its application to ruminants. Journal of Animal Science, 87 (10), pp.3317-3334.

Hippen, A.R., DeFrain, J.M. and Linke, P.L. 2008, January. Glycerol and other energy sources for metabolism and production of transition dairy cows. In Florida Ruminant Nutrition Symposium (Vol. 605, No. 1).

Kristensen, N.B. and Raun, B.M.L. 2007. Ruminal fermentation, portal absorption and hepatic metabolism of glycerol infused into the rumen of lactating dairy cows. Publication European Association for Animal Production, 124, p.355.

Mc Donald, P., Edwards, R.A., Greenhalgh, J.F.D., Morgan, C.A., Sinclair, L.A. & Wilkinson, R.G. 2011. Carbohydrate synthesis. In: Animal Nutrition. pp. 226-234. Harrlow, England: Pearson Education Limited 7th Edition).

Piantoni, P. and Allen, M.S. 2015. Evaluation of propylene glycol and glycerol infusions as treatments for ketosis in dairy cows. Journal of Dairy Science, 98 (8), pp.5429-5439.

Van Hoeij, R. 2017. Metabolic status, lactation persistency, and udder health of dairy cows after different dry period lengths. Wageningen University and Research.