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Butyrate in diets for newborn calves

Paweł Górka for Progressive Dairyman Published on 09 March 2017

It is now common to find butyrate in commercial milk replacers and solid feeds for calves. However, the impact it has on the calf varies depending on the delivery method and the source of dietary butyrate being used. Let’s have a closer look at why butyrate is a valuable feed additive, how it can be supplemented and how its use in feeds affects calf performance.

Gastrointestinal tract development

The gastrointestinal (GI) tract of calves is not fully developed at birth. This predominantly refers to the rumen. Rumen volume is very small at birth and rumen papillae are nearly absent. It stays this way for the first two to three weeks, until regular solid feed intake starts.

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The abomasum and small intestine, on the other hand, begin to undergo rapid development right away. This is because these regions of the GI tract are the main sites of liquid feed (milk or milk replacer) digestion. Since liquid feed is the main source of nutrients for calves prior to solid feed intake, which usually takes place in the second or third week of life, the development of the abomasum and small intestine has a huge impact on the growth and health of calves at a very early stage of life.

Rumen development, on the other hand, occurs gradually and is driven predominantly by solid feed intake and short chain fatty acids produced by microbes in the rumen.

Why butyrate?

Butyrate is a natural end product of microbial fermentation of carbohydrates in the GI tract. Its production is especially high in the rumen, particularly when animals are fed diets high in starch and simple sugars. When solid feed high in these carbohydrates is offered, it results in high butyrate production in the rumen and a substantial acceleration of rumen epithelium and rumen papillae development.

This, in turn, results in high solid feed intake and efficient solid feed digestion at a very early age. Butyrate is also present in whole milk. Prior to the development of the rumen, this source of butyrate has a substantial impact on calf GI tract development, particularly the development of the abomasum, small intestine and pancreas.

For the first two to three weeks of life, butyrate production in the calf’s rumen is minimal, due to low solid feed intake and not yet fully developed rumen microflora. At this stage, dietary butyrate supplementation may allow for substantial acceleration of GI tract development.

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Furthermore, newborn calves are often fed milk replacers, instead of whole milk, which, in most cases, lack butyrate, due to the use of alternative fat sources, instead of milk fat.

Dietary supplementation

Butyrate can be supplemented in liquid feed (milk or milk replacer), solid feed (starter mixture) or both. Since liquid feeds bypass the rumen via the esophageal groove and enter the abomasum, but solid feeds enter the rumen, the method of butyrate supplementation determines the region of the GI tract directly exposed to its action.

When it is supplemented in liquid feed, butyrate predominately affects the abomasum and small intestine. If it’s added to solid feed, it primarily affects the rumen (Figure 1).

effect of dietary butyrate on gastrointestinal tract development in ruminantsNevertheless, the addition of butyrate into liquid feed may affect rumen development, and butyrate supplementation in solid feed may affect abomasum and small intestine development, especially when the protected form of butyrate is used in solid feed.

For example, the stimulatory effect of butyrate added into milk replacer on abomasum and small intestine development may result in higher solid feed intake. This, in turn, speeds up rumen development.

Besides different methods of butyrate supplementation, various sources of butyrate can be used in feeds. Butyrate can be supplemented as a salt (sodium, calcium) or as ester of butyrate and glycerol (e.g., mono-, di- or tributyrin or mixture of those). These butyrate sources differ substantially in terms of their physicochemical properties and impact on the calf’s GI tract.

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From the above mentioned, sodium butyrate is the most often used source of butyrate in feeds for calves. Sodium butyrate easily dissolves in water and rapidly dissociates in water solutions. When this source of butyrate is used in feed, butyrate action is located predominantly in the stomach (forestomach, abomasum).

Calcium butyrate, on the other hand, is much less soluble in water solutions than sodium butyrate. Therefore, at least part of the butyrate delivered in this form is expected to bypass the stomach and enter the small intestine.

When delivered as mono-, di- or tributyrin, butyrate must be released from glycerol by lipase before it elicits its effect on the GI tract (Figure 2). This takes place predominantly in proximal regions of the small intestine.

Lopose action on tributyrin

Further modulation of butyrate impact on the GI tract can be obtained by its protection from degradation in the stomach. This can be done by butyrate embedding in the fat (lipid) matrix (Figure 3), commonly referred to as microencapsulation or fat coating.

Microencapsulated butyrateMicroencapsulated butyrate is only partially released in the stomach and most of the active substance is gradually released along the entire small intestine. The remaining portion of encapsulated butyrate, not released into the stomach and small intestine, can be released into the large intestine, as a result of microbial lipase action.

Results of studies

Butyrate in milk replacer

From the different sources of butyrate, unprotected sodium butyrate supplementation in milk replacer was repeatedly shown to stimulate GI tract development in calves. It is worth noting that this effect was observed even at a very low level of supplementation (0.3 percent of milk replacer dry matter).

When we delivered it in milk replacer, the unprotected sodium butyrate most likely rapidly dissociated in the abomasum and was completely absorbed and metabolized at the abomasum level. However, this method of butyrate supplementation was also shown to stimulate the small intestine and pancreas development and function, and also rumen papillae development.

Sodium butyrate supplementation in milk replacer increased brush border enzyme activity and pancreatic secretion, and, consequently, increased efficiency of nutrient digestion and positively affected growth performance of calves.

However, only a few reports that document the impact of unprotected calcium butyrate and protected forms of butyrate use in milk replacer on growth performance and GI tract development of calves are available, and unprotected tributyrin addition into milk replacer was shown to negatively impact growth performance of calves. Furthermore, the effect of butyrate supplementation in whole milk on GI tract development and performance of calves has not been investigated.

Butyrate in solid feed

When used in solid feed, both protected and unprotected butyrate showed a positive impact on GI tract development and growth performance of newborn ruminants. Unprotected sodium butyrate use in concentrate increased concentrate intake and rumen papillae length.

Nevertheless, this effect seems to be dose- and age-dependent. Specifically, the results of the studies suggest that unprotected sodium butyrate supplementation in a calf starter mixture at a very low level, equaling 0.3 percent of dry matter, can effectively stimulate rumen epithelium development and solid feed intake during the pre-weaning period.

However, to sustain this effect after weaning, a much higher level of supplementation may be required, even as high as 1 percent of dry matter. Nevertheless, levels equal to 3 percent of concentrate was shown to decrease concentrate intake by calves, as compared with lower levels of supplementation. Furthermore, the optimal level of unprotected sodium butyrate supplementation in solid feed may depend on the presence of or lack of forages in the diet and forage proportion in the diet.

Unprotected forms of butyrate, however, only showed a positive impact on performance and GI tract development in calves during the pre-weaning period. A very low level of supplementation (0.3 percent of microencapsulated product per kilogram of dry matter) was reported to enhance GI tract development of calves and starter mixture intake in the first weeks of life. However, this effect was no longer visible after weaning.

Furthermore, levels of supplementation higher than 0.3 percent in pelleted starter mixture resulted in an inferior response. This altogether suggests that microencapsulated butyrate has the potential to enhance gut development and performance of calves mainly during the pre-weaning period. Higher level of supplementation may be required after weaning, but its determination requires further studies.

So far no reports on efficiency of unprotected calcium butyrate as well as both unprotected and protected tributyrin use in starter mixtures for calves are available.

Butyrate both in liquid and solid feed

So far only one study has compared different methods of butyrate supplementation in diets for newborn calves. In this study, the addition of unprotected sodium butyrate in milk replacer improved growth performance of calves, whereas the supplementation of protected sodium butyrate in starter mixture increased solid feed intake. Both methods of supplementation stimulated GI tract development.

However, no additive effects of simultaneous butyrate supplementation in milk replacer and starter mixture on GI tract development and performance of calves was shown in this study. Nevertheless, it was concluded that when calves are fed milk replacer, which may delay GI tract development, the addition of butyrate into both liquid and solid feed may be recommended.  end mark

Dr. Paweł Górka is a researcher in the department of animal nutrition and dietetics at the University of Agriculture in Krakow, Poland. Email Dr. Paweł Górka. 

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