Figure 1: The addition of cane molasses on rumen gas production
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Butyrate is known to stimulate rumen, abomasum and small
intestine development. It also modulates the secretion in the gastro- intestinal tract of gut regulatory peptides and hormones. Together these effects increase the nutrient absorption in the digestive tract. By increasing the proportion of butyrate, molasses has been shown to improve overall diet utilisation. In addition, by increasing the butyrate:acetate ratio the addition
Gas production is an indicative measure of rumen microbial
activity. When molasses was added to in vitro diets a significant and sustained increase in gas production was observed (Fig. 1). While the sugars in molasses were effectively exhausted within
four hours, they had effectively kick started the fermentation, increasing overall rumen microbial activity. The consequence will be increased feed utilisation and nutrient capture and also a greater rumen throughput which may explain why molasses has a reputation for stimulating intakes. There is evidence that shows adding molasses can increase the overall total digestibility of the other feed ingredients. The addition of molasses also has an impact on rumen VFA
production, both the total production and also the relative proportions of VFAs produced. Fig. 2 shows the effect of molasses inclusion on VFA production. At all time-points the total VFAs produced is higher in the molasses supplemented diets, indicative of greater rumen microbial activity and an enhanced energy supply to the cow.
Figure 2: The effect of the addition of cane molasses on rumen VFA production (mmol/L)
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and butyrate. The increase in butyrate production is particularly significant.
Figure 3: The effect of the addition of cane molasses on key rumen VFA ratios
Table 2 shows the impact of increasing the proportion of sugars
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in the diet. All three diets contain a similar total percentage of starch and sugar, with starch reducing as sugar content increases. The digestibilities of the dry matter, NDF and ADF all increased.
Fibre digestion Ruminants rely on being able to digest fibre. Effective digestion of fibre is vital as we strive to increase forage intakes to maximise production from forage and reduce costs per litre. Rather than striving to get more forage into cows, the goal must be to utilise it better. Micro-biological analysis confirms that the addition of molasses
stimulates the populations of fibre digesting micro-organisms in the rumen. Table 3 shows the impact of a number of fermentable carbohydrate sources on NDF digestibility. The ED&F man blend and
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of sugars can help reduce problems with rumen acidosis. Increased production of butyrate and reduced acetate output reduces the acid load in the rumen because butyrate is a less powerful acid. Butyrate can also increase the absorption of acids from the rumen, further helping moderate acid loading. High yielding dairy cows, in particular, require a high supply of
fermentable carbohydrates, but increasing levels can increase the risk of acidosis. Carbohydrate levels are usually assessed in diets as combined starch and sugars with a maximum of around 30-35% in the dry matter. The new research indicated a benefit from considering sugars
and cane molasses more closely. Increasing the proportion of sugars to starch would allow an increase in total fermentable carbohydrates while reducing the risk of acidosis. The trend has been to higher starch diets, increasing the risk of cows being prone to acidosis. Starch fermentation tends to increase rumen lactic acid production, which has a more dramatic effect on pH than other rumen VFA’s. Increasing the sugar levels in the diet to 7% while holding overall starch and sugar at around 30% will allow a more efficient fermentation without increasing the acidosis risk.
Table 2: The effect of higher sugar content on the digestibility of dry matter and fibre in the diet
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