Mulberry silage to promote dairy cow gut health

With the ban on in-feed antibiotics, the feed industry is on the lookout for feed resources that confer animal health while maintaining high levels of performance. Plant-based products are rich in bioactive compounds valuable in boosting animal health.

Mulberry trees are fast-growing deciduous plants of the Moraceae family that are widely distributed in South Asia and East Asia. Mulberry trees are multipurpose, their fruits are used as food and for winemaking, while the leaves are often used as fodder due to the high biomass, crude protein content, and digestibility. The trees are rich in polyphenols such as flavonoids, anthocyanins, benzoic acid, and hydroxycinnamic acid. The anthocyanins can scavenge free radicals and inhibit low-density lipid oxidation.

Other studies show that polyphenols can regulate intestinal bacteria composition and inhibit the growth of pathogenic bacteria. It is also shown, in previous studies, that providing ensiled mulberry silage to dairy cows improves the immune and antioxidant function. On the other hand, the application of mulberry leaves silage has shown that it could be used in finishing steer diets without affecting production performance.

Mulberry study

The researchers of the current study investigated the effects of mulberry branch and leaves silage on milk yield, ruminal fermentation, and bacteria composition in dairy cows. They also evaluated the correlation between the ruminal microbiome and fermentation parameters. The mulberry leaves and branches were harvested at 0.8-1.0 m height (late growing period) and ensiled using 10% maize flour after chopping. A total of 36 mid-lactation cows were selected and randomly allocated to 3 groups:

• Control group: total mixed ratio (TMR) diet without the inclusion of mulberry silage
• Experimental groups: TMR supplemented with either 5% or 10% mulberry silage.

Milk yield and composition

The results of the study showed that the inclusion of 10% mulberry silage significantly increase milk yield, milk fat content and feed efficiency (Table 1). As observed in previous studies, the researchers suggested that ensiling mulberry could reduce the levels of lignin in the branches and increase the levels of soluble reducing sugars, leading to a higher rate of degradation in the rumen; the improved milk production was therefore attributed to the enhanced digestibility of mulberry silage in the rumen.

They added that some studies showed that dietary supplementation of fermented mulberry leaves increased levels of bioactive components and protein while reducing crude fibre content and anti-nutritional factors of the diet. They also stated that plant flavonoids could promote the development of mammary glands, improve milk quality, and modulate the ruminal microbiome and fermentation, as confirmed in the current study. The improvement in lactation performance was also related to a probable enhancement of the immune system, as supported by the observed decreases in milk somatic cell counts, in the present study.

In a similar study published in the Asian-Australasian Journal of Animal Sciences, researchers found that diets with 10-15% of mulberry silage enhance the immune and antioxidant function of dairy cows while increasing the polyunsaturated fatty acid concentration in the milk. In their study, researchers highlighted that today’s intensive model of farm animal husbandry brings high yields, but compromises animal health and welfare which might increase the incidence of diseases — hence, worthwhile to explore feed additives such as antioxidant-enriched forages to complement diets of dairy cattle.

Rumen fermentation

It was found that rumen propionic acid significantly increases with increasing levels of the mulberry silage; however, there were no differences in the pH, ammonia nitrogen, and total volatile fatty acids concentrations in the rumen. Butyrate showed higher values in both the 5% and 10% mulberry silage diets, but the difference from the control group was minimal.

The correlation analysis between rumen fermentation and microorganisms showed that propionic acid was positively correlated with Firmicutes bacteria but was negatively correlated with Bacteroides bacteria. It was highlighted that feed efficiency is positively correlated to Firmicutes (Succinivibrio and Enterococcus faecalis), which were abundant in the mulberry silage diet compared to the control group, in the current study. Succinivibrio can convert succinic acid into propionic acid, thus increasing the ruminal levels of propionic acid and consequently increasing the lactose and milk yield. “This explains the increase in the ruminal propionic acid levels and feed efficiency,” the researchers said.

The rumen microbiome

Dietary changes usually affect the rumen microbiome. The rumen microbiome in dairy cows plays an essential role in animal health and performance. In the current study, the partial replacement of forage and concentrate with 5% or 10% mulberry branch and leaves silage influenced the ruminal microbiome.

Consistent with previous studies, the microbiome analysis showed that Bacteroides, Firmicutes, and Proteobacteria were the predominant phyla. The proportions of the different bacteria phyla between the groups showed large differences. Compared to the mulberry-free diet, the abundance of Bacteroides was significantly decreased, while the Firmicutes and Proteobacteria were increased in the mulberry groups.

The Bacteroides Prevotella was significantly decreased in the mulberry silage groups, while the Proteobacteria Succinivibrionaceae_UCG-001 was increased. The abundance of Prevotella was shown to be negatively correlated with the milk fat yield, which corresponds to the lower fat yield observed in the control diets. In this study, the abundance of Lachnospiraceae (Lachnospiraceae_NK3A20_group) and Ruminococcaceae (Ruminococcaceae_NK4A214_group) was significantly higher than in the control group, suggesting that the mulberry silage led to an increase in the abundance of rumen fibre-degrading bacteria.

Overall, the correlation analysis showed that 8 bacterial species belonging to Firmicutes were positively correlated with propionic acid, while 4 bacterial species belonging to the Bacteroides group were negatively correlated with propionic acid. The researchers concluded that feed supplementation with mulberry silage modulates the rumen microbiota and fermentation, increasing the abundance of fibre-digesting and milk fat-related microorganisms, and propionic acid synthesis, consequently improving milk yield in dairy cows.

This article is based on a study by Yan Li, Jiaqi Wang, Jie Mei, Lingxia Huang and Hongyun Liu. 2022. Effects of Mulberry Branch and Leaves Silage on Microbial Community, Rumen Fermentation Characteristics, and Milk Yield in Lactating Dairy Cows. Fermentation, Vol 8, 86.