Improving veal calf growth with soluble fibers

A number of tests have been conducted regarding short-chain fructo-oligosaccharides over the past 20 years, and the conclusion is clear: dietary supplements of short-chain fructo-oligosaccharides for calves result in higher performance. This information, if implemented, could result in substantial economic benefits for both feed manufacturers and breeders.

Short-chain fructo-oligosaccharides are a combination of a terminal glucose molecule and one, two or three molecules of fructose. They naturally exist in many plants but can also be produced from beet sugar by enzymatic process. In this case, the composition is stable among the three following molecules GF2: 37 percent, GF3: 53 percent, and GF4: 10 percent. They are listed in the European catalog of feed materials as Fructo-oligosaccharides (number 4.1.14).

Reducing pathogenic bacteria  

Not digested in the small intestine, these carbohydrates are considered as a source of soluble fibers that can present some prebiotic properties (Gibson et al., 2004). In many animal species, short-chain fructo-oligosaccharides are known to particularly stimulate the growth of intestinal bifidobacteria and some strains of lactobacilli (Xu et al., 2003; Tzortzis et al., 2004).

In veal calves, short-chain fructo-oligosaccharides have been shown to modulate the intestinal microbiota and reduce the prevalence of potentially pathogenic bacteria. As an example, dietary supplementation of short-chain fructo-oligosaccharides increased the level of bifidobacteria measured in faeces (Bunce et al., 1995). Furthermore, a recent in-vitro study demonstrated that the microbiota inhabiting the terminal part of the ileum was able to ferment these molecules. In comparison to a control fermentation substrate, the medium containing short-chain fructo-oligosaccharides induced a greater development of lactobacilli and streptococci as well as lactate-utilizing bacteria, while there was no difference on clostridium perfringens (Philippeau et al., 2010).

It was noticeable that the stimulation was negatively correlated to the initial level of bacteria; the lower the initial concentration, the higher the stimulation. Due to their fermentation by lactic acid bacteria, there was an increase in L-lactate production but very limited increase of D-lactate production accompanied by a higher concentration of acetate and butyrate than with the control medium. This is fully in accordance with what was observed in-vivo in other animal species like horses (Respondek et al., 2008a).

Improved weight gain  

Several studies have demonstrated that the addition of 2 g to 6 g of short-chain fructo-oligosaccharides/d improved body weight gain (+ 1 to 4 percent compared to the control diet, with no short-chain fructo-oligosaccharides) and the feed conversion ratio (Figure 1) of calves that weighed between 45 kg and 140 kg at the beginning of the experiments. Furthermore, the addition of short-chain fructo-oligosaccharides in diets contributed to homogenized growth performance of calves.

In a 2011 study conducted in France, an addition of 0.15 percent and 0.30 percent of short-chain fructo-oligosaccharides in diets only increased growth performance a small amount (1 percent on average), but strongly reduced standard deviation of the body weight of calves at slaughtering. The increase of growth performance was accompanied by a lower feed conversion ratio. As an example, a feed conversion ratio of 1.55 for the control diet without short-chain fructo-oligosaccharides dropped to 1.46 for the same diet after an addition of 0.50 percent of short-chain fructo-oligosaccharides was reported (1992, unpublished Beghin-Meiji). Figure 1 shows that growth performance increases as soon as 2 g/d/calf, and reaches a threshold when about 3 g/d/calf of short-chain fructo-oligosaccharides are fed. Maximum feed conversion ratio is reached when 3 to 6 g/d/calf of short-chain fructo-oligosaccharides are added to diets.

Stronger effects in case of stress  

The ability of short-chain fructo-oligosaccharides to promote growth performance are more pronounced when animals are under stress conditions. This point is important to underline since young animals are very sensitive to stress situations like weaning.

In the case of a nutritional stress, Kaufhold et al. (2000) evaluated the effects of short-chain fructo-oligosaccharides on the growth performance of calves fed with both normal and high levels of lactose in their diets. They noted in both cases an increase of growth performance but reported that all effects observed were prominent after lactose loads.

In other experimental conditions, and notably with a weaning stress, Tai et al. (2009) reported a very strong improvement and a homogenization of growth performance of early-weaned calves by addition of short-chain fructo-oligosaccharides. In this study, calves weaned at only 40 days old instead of 70 days and supplemented with 2 to 6 g/d of short-chain fructo-oligosaccharides for 30 days reached the same body weight gain than those of calves weaned later (520 g/d on average). In contrast, the body weight gain of non-supplemented early-weaned calves was much lower and averaged 371 g/d.

Improved carcass classification  

A French study (2001, unpublished Beghin-Meiji) first showed that carcass weight was increased by 1.2 percent. Secondly, the study demonstrated that in the European system, carcasses were less classified as P when calves were fed a diet supplemented with 0.15 percent of short-chain fructo-oligosaccharides than with a control diet containing no short-chain fructo-oligosaccharides. These results put forward a better carcass conformation when calves were fed with short-chain fructo-oligosaccharides.

Again, short-chain fructo-oligosaccharides supplementation not only improved carcass weights, but also tended to homogenize this result since standard deviation strongly decreased from 9.1 percent for the control to 5.8 percent for the short-chain fructo-oligosaccharides diet. In the same way, in a recent study (Grand et al., submitted for publication), a dietary addition of 3 or 6 g/d of short-chain fructo-oligosaccharides increased the carcass weight of calves by 3.9 kg.

Other effects of short-chain fructo-oligosaccharides are expected and are actually studied in calves. Thus, further research is currently underway to evaluate the interest of adding short-chain fructo-oligosaccharides for prevention of glucose intolerance generally appearing in veal calves fed high amounts of simple sugars, as it has already been seen in horses and in dogs that short-chain fructo-oligosaccharides can slightly improve metabolic parameters in such cases (Respondek et al., 2008b; Respondek et al., 2011).

Recommendation  

Finally, probably due to the effects on intestinal health and metabolism and to the change in intestinal microbiota, addition of short-chain fructo-oligosaccharides increases growth performance, improves carcass characteristics and allows homogenizing these criterions inside a group of calves. These assumptions are particularly true when calves are submitted to a stress.

In short, the addition of 3 to 6 g/d/calf of short-chain fructo-oligosaccharides in diets (or 1.5 to 3.0 kg/t of CMR) are a good recommendation to optimize calf performances.