Nutritional Value of Molasses for Cattle

Researchers have now fully explored the composition of molasses, which has now been analysed up to 97.4%, to better understand its benefits for livestock.

Typically, molasses was understood to be made up of dry matter, sugar, protein and ash content, however this new, more thorough analysis, contains information on specific organic acid presence and sugar ratios. This data provides further insights to help understand how molasses and molasses-based liquid feeds achieve such a high level of functionality within a ration and the rumen.

The addition of sugar to ruminant rations in the form of molasses has a long history. It started with the purpose of making the ration more palatable and avoiding sorting, as well as being used for decades in the feed mill industry as an energy source, appetiser, binding and anti-dust agent.

However, in the last few years, it has been shown to play an important role for the optimal functioning of the rumen ecosystem and we now understand molasses-based liquid feeds are not only interesting for these dietetic and technological roles, but that they have a functional role within a ration formulation.

In fresh forages, the sugar component can represent up to 10-12% of dry matter (DM), in hay on average 5-6% and in silages only 1-3% of DM. The main nutritional role of sugars is to supply the rumen microbiome with rapidly fermentable carbohydrates in order to balance the rumen fermentable proteins which can help to support higher levels of microbial growth and protein in the rumen.

Approximately 70% of the protein consumed by ruminants is broken down into ammonia in the rumen. It is then utilised by the rumen microbes as building blocks to produce microbial protein in a process which requires energy.

The addition of molasses into a ration provides an ideal source of readily available and rapidly fermentable carbohydrates, which provide the rumen microbes with the energy needed to utilise rumen ammonia, creating microbial protein and enhancing nitrogen utilisation within the rumen.

The key to efficient utilisation is to ensure the synchronous balance between energy and nitrogen, this can be achieved with the addition of molasses to a ration.

The digestibility of sugars has also been evaluated and specifically the digestibility of different types of carbohydrate sources. It was found that molasses has the fastest rate of fermentation in the rumen, proving its ability to provide readily fermentable energy to the rumen microbes.

Furthermore, total gas production was also analysed in order to evaluate rumen activity levels as the rumen microbes produce gas when active. A high level of gas production can indicate that the rumen microbes are more actively fermenting feed and therefore, extracting more nutritional value from the feed.

From this research it was also found molasses has the highest gas production compared to other carbohydrate sources such as wheat. Additionally, the production of gas continued over the 24-hour trial period showing the rumen microbes are still active long after the sugars have been digested. This suggests molasses may act as a catalyst in the rumen, stimulating microbial activity.

It is important to remember that not all sugars are equal. Sugars present in animal feeds can be categorised as either 6-Carbon or 5-Carbon sugars. 6-carbon sugar molecules are glucose, fructose and galactose and the 5-carbon sugar molecules are arabinose, xylose and ribose.

Sucrose is made up of two molecules, glucose and fructose, which are both 6-carbon sugars. Cane molasses typically contains a complex of many sugars with an average 38% sucrose, 4% glucose and 7% fructose, compared to beet molasses which contains a higher average of 47% sucrose but less than 1% glucose and fructose and not providing a diversification in sugars.

The 6-Carbon sugars which are present in molasses-based liquid feeds are more highly rumen fermentable and more effective at improving fibre digestion than 5-Carbon sugars.  The graph below shows the digestibility of the different types of sugar, after four hours both sucrose and glucose are fully digested compared to the 5-carbon sugars such as xylose which never reached 100% digestibility.

5-carbon sugars are typically found in feeds that have already been fermented e.g., pot ale syrup and wheat syrups, silages, and processed feeds. Due to the co-products having been fermented already, they have little or no effect on rumen activity when fed. This is unlike molasses-based liquid feeds which are fermented in the rumen, stimulate activity and microbial growth, providing a function beyond the calorific content.

Currently, laboratories can analyse not just the total sugar content in the feedstuffs, but also the individual sugars, thus making possible the formulation of diets considering the quantity of each specific kind of sugar.

It is important to note that different types of sugar can also have different effects on the rumen microbial populations. For example, Butyrvibrio fibrisolvens, a bacterium responsible in milk fat production and ensuring the correct pathway for fatty acids against milk fat depression, prefers the sucrose substrate compared to glucose.

A functional ingredient is one with an outcome that is beyond the expected nutritional response for the level of

energy or protein the ingredient has. For example, we know that feeding low doses of butyrate will stimulate rumen, abomasum, small intestine and pancreas development. It can also modulate gastrointestinal tract secretion of gut regulatory peptides and hormones. The outcome of this can increase nutrient absorption far beyond the level predicted by the caloric contribution.

In the same way, molasses behaves above and beyond its calorie or protein value in its effects on rumen pH modulation, fibre digestibility, volatile fatty acid production, microbial protein synthesis and milk quality increases.

In a previous blog, we explored the impact of feeding molasses to cows and discussed the effects on rumen pH. To summarise, cellulolytic bacteria are the main bacteria that influence fibre digestibility and are highly influenced by the pH of the rumen.

At a pH lower than 6.25, fibre digestion is compromised and at lower than 5.3 this decreases the growth of cellulolytic bacteria and stops their ability to adhere to plant cell walls. In order to maintain a healthy pH and rumen environment, feeding sugars in the form of molasses to cows can help greatly.

The influence of sugars on fibre digestibility is well documented with studies dating from the early 1950’s showing its beneficial effects on enhancing cellulose digestion. It is often theorised that for every 1% of undigested fibre (NDF), this can represent a 0.17kg drop in dry matter intakes and a 0.25kg reduction in milk yield.

On farm, we have seen a 17% improvement in ration digestibility by carrying out faecal sieving on a farm before and six weeks after implementing a molasses-based liquid feed into the ration. This total ration digestibility improvement is often translated into beneficial effects in performance. A meta-analysis carried out looking to summarise the benefits on milk quality with the addition of sugars to the ration found that as additional dietary sugar increased up to 5-7% DM, the amount of milk protein also increased. This effect was significantly increased in high yielding herds with average milk yields above 33kg/day. Milk fat yields also increased when additional dietary sugar was increased to 5-7% DM, with the high yielding cows having the most beneficial effects.

In conclusion, the true nutritional value of molasses is only just being fully unlocked and its behaviour as a functional ingredient within the rations for dairy cows and beef cattle is still being understood.

It is important to consider the type of sugar when feeding a liquid feed as not all sugars are equal and the most benefits are seen when a good complex of different types of sugar are fed such as those present in cane molasses.

If you’d like to know more about how molasses can benefit your cattle or would like support around incorporating molasses into your feed, get in touch.