Although probiotics are known to benefit health and productivity of ruminants, the peculiarities of their digestive tract and its microbiota impose certain challenges to the use prebiotics and synbiotics. This article gives a concise introduction to the topic.
Probiotic products have been widely used to promote productive performance and gastrointestinal health in ruminant. However, the peculiarities of the ruminal gastrointestinal tract and its microbiota have limited the success of the application of prebiotics and synbiotics.
The ruminal microbiota is doubly beneficial to the animals. It actively degrades the diet, whilst providing nutrients released by the degradation process. At the same time, bacteria that leave the rumen are digested, supplying the animal with protein of high biological value. The rumen microorganisms live in symbiosis with the host animal, and the microbial interactions are numerous and highly complex
Rumen microorganisms live in symbiosis with the ruminant.
The inclusion of probiotics in diets for ruminants contributes to the maintenance of ruminal flora and the improvement of rumen function. Probiotics have been mainly applied to cows and calves, while less information is available on their use in lambs, sheep, and goats.
Studies on the application of probiotics have been carried out in young (pre-ruminant) and adult ruminants, considering the health status of the animals (reduction of diarrhea incidence/severity, presence of pathogenic microorganisms) and productive parameters.
Neonatal diarrhea in calves is an important cause of morbidity and mortality in young ruminants, it is generally caused by enterotoxigenic E. Coli. A significant reduction in the incidence of diarrhea was observed in calves fed fermented milk containing mixed cultures of lactic acid-producing bacteria, or a combination of Lactobacillus acidophilus and the yeast Saccharomyces cerevisiae (Agarwal et al., 2002).
Enterotoxigenic E. coli is an important cause of morbidity and mortality.
Furthermore, in a trial evaluating young calves, live yeast was incorporated into the diet. The results showed a significant reduction in the number of days with diarrhea (Galvao et al., 2005).
Also, Timmerman et al. (2005) evaluated probiotic preparations containing six species of Lactobacillus spp. of bovine and human origin. When administered to calves, mortality, incidence of diarrhea, and faecal coliform counts were reduced.
Among the zoonotic pathogens, E. coli O157: H17 is one of the main threats to ruminant health, besides playing an important role in the epidemiology of human infections (Griffin and Tauxe, 1991). In a large-scale trial, steers fed a corn-based diet supplemented with L. acidophilus showed a reduction of 57% in faecal excretion of E. coli O157:H17 (Younts-Dahl et al., 2004). These results were corroborated by Peterson et al. (2007), who conducted a two-year field trial and observed that the elimination of E. coli O157:H7 in faeces was decreased by 35% in cattle when L. acidophilus was administered daily in the diet.
Regarding productive performance of ruminants, improvements in weight gain and rumen development were observed in young calves when different bacterial strains and live yeasts were added to the diet (Adams et al., 2008). In dairy cows, live yeasts have proven to be effective in improving performance, with increases in dry matter intake and milk production as the most consistent effects (Jouany, 2006; Stella et al., 2007). A meta-analysis developed by Desnoyers et al. (2009) showed that yeast supplementation of ruminant diets increases milk production, rumen pH, rumen concentration of volatile fatty acids and organic matter digestibility.
Also, the inclusion of yeasts in the diet is associated with increases in rumen bacterial populations, specifically cellulolytic microorganisms (Chaucheyras-Durand et al., 2008), besides increases in fiber digestibility (Guedes et al., 2008; Marden et al., 2008).
The use of prebiotics in cattle have been limited by the ability of ruminants to degrade most prebiotic products. However, technological advances to protect the additives from rumen degradation could allow prebiotics to be fed to dairy and beef cattle (Callaway et al., 2008). In fact, several types of non-digestible oligosaccharides are found in the cell wall of plants normally used to feed cattle (Lema et al., 2002).
The concept of synbiotics in ruminants appears not to have been widely developed. Fleige et al. (2007) investigated the effects of feeding lactulose in combination with E. faecium to pre-ruminant calves on growth performance and intestinal morphology. In another study, Yasuda et al. (2007) evaluated the effect of a synbiotic consisting of Lactobacillus casei subsp. casei and dextran on milk production of Holstein cows.
Both synbiotics were beneficial to the animals. Particularly, the second study showed improved milk production, which resulted from a positive change in the profile of intestinal microbiota, a reduction of infectious diseases, and even a reduction of stress levels for the cow.
Due to the physiological and morphological characteristics of the gastrointestinal tract of ruminants, further studies are needed to understand the effects of using probiotics, prebiotics or synbiotics in these species.
This article was originally published in nutriNews Spain, with the title Aplicación de probióticos, prebióticos y simbióticos en rumiantes
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