The present study was conducted to evaluate the effect of a live culture of Aspergillus oryzae (A; CCT4359) and fibrolytic enzyme (E; Fibrozyme Alltech Inc.) on fibre digestibility by a gas production bioassay and in vitro degradation of maize silage and sugarcane silage. A completely randomized design trial was performed to evaluate: A doses (0, 20, 60 and 100 mg/l), E doses (0, 160, 320 and 480 mg/l) and roughage source (R; maize and sugarcane silage) in a 4 × 4 × 2 factorial arrangement. The inclusion of increasing doses of A and E increased dry matter and neutral detergent fibre in vitro digestibility linearly, but for E this effect occurred only in maize silage. There was a linear increase in the potential for gas production at the highest dose of A only in sugarcane silage, with no effect on lag time (L). Increasing doses of E increased the volume of gases produced linearly, and a trend of linear reduction of L, regardless of the roughage. There was a linear reduction in ammonia-nitrogen concentration in response to increasing doses of A and E, and an increase in acetic acid concentration at the highest dose of A, regardless of roughage. The additives had no synergistic effect on gas production and digestibility, but were efficient in altering the fermentative pattern, demonstrating the potential to increase fibre degradation.

All livestock animal species harbour complex microbial communities throughout their digestive tract that support vital biochemical processes, thus sustaining health and productivity. In part as a consequence of the strong and ancient alliance between the host and its associated microbes, the gut microbiota is also closely related to productivity traits such as feed efficiency. This phenomenon can help researchers and producers develop new and more effective microbiome-based interventions using probiotics, also known as direct-fed microbials (DFMs), in Animal Science. Here, we focus on one type of such beneficial microorganisms, the yeast Saccharomyces. Saccharomyces is one of the most widely used microorganisms as a DFM in livestock operations. Numerous studies have investigated the effects of dietary supplementation with different species, strains and doses of Saccharomyces (mostly Saccharomyces cerevisiae) on gut microbial ecology, health, nutrition and productivity traits of several livestock species. However, the possible existence of Saccharomyces which are indigenous to the animals’ digestive tract has received little attention and has never been the subject of a review. We for the first time provide a comprehensive review, with the objective of shedding light into the possible existence of indigenous Saccharomyces of the digestive tract of livestock. Saccharomyces cerevisiae is a nomadic yeast able to survive in a broad range of environments including soil, grass and silages. Therefore, it is very likely that cattle and other animals have been in direct contact with this and other types of Saccharomyces throughout their entire existence. However, to date, the majority of animal scientists seem to agree that the presence of Saccharomyces in any section of the gut only reflects dietary contamination; in other words, these are foreign organisms that are only transiently present in the gut. Importantly, this belief (i.e. that Saccharomyces come solely from the diet) is often not well grounded and does not necessarily hold for all the many other groups of microbes in the gut. In addition to summarizing the current body of literature involving Saccharomyces in the digestive tract, we discuss whether the beneficial effects associated with the consumption of Saccharomyces may be related to its foreign origin, though this concept may not necessarily satisfy the theories that have been proposed to explain probiotic efficacy in vivo. This novel review may prove useful for biomedical scientists and others wishing to improve health and productivity using Saccharomyces and other beneficial microorganisms.

We hypothesised that probiotic feeding would alter the fatty acid (FA) profile of sheep's milk. Sixteen lactating ewes, kept under the same feeding and management practices, were randomly allocated to receive either a control diet or the same diet supplemented with a commercial multi-strain bacterial probiotic. Milk fat FA contents were monitored fortnightly for eight consecutive weeks from 14 d after lambing. Probiotic supplementation increased the contents of butyric and caproic acids in milk fat and had no negative effects on other relevant FA from the human's health point of view (i.e., no differences in branched chain, vaccenic, rumenic and n-3 FA were observed). Under the conditions assayed in the present work, the contents of milk FA originated from rumen microbial metabolism were scantly altered, which suggests that the rumen conversion pathways of FA were not substantially modified by the probiotics.

A 26-day trial with 18 Pietrain×(Landrace×Duroc) pigs was conducted to investigate the effect of two dose levels of a specifically selected Bacillus spp. direct-fed microbial (DFM) product, on the emission of environmentally harmful gasses (methane, ammonia and hydrogen sulphide) from manure. Pigs were assigned to one of three treatments in a randomized complete block design according to their sex and initial BW. Each treatment contained three replications with two pigs per pen. The test treatments included a Bacillus spp. DFM containing 3×108 colony-forming unit/g, added at a low (250 mg/kg) and high (500 mg/kg) dose to an antibiotic free high fibre-based diet, and a non-supplemented control diet. Manure from pigs fed with the supplemented diets emitted lower amounts of atmospheric contaminants. The most significant reduction was observed with low DFM supplementation, in which methane and ammonia volatilization decreased (P<0.05) by >40% and 50%, respectively, on fresh weight basis in relation to the control. Microbiome analysis of manure by high through put sequencing techniques on eubacterial and archaeal 16S rRNA genes highlighted the complex interactions between indigenous gut microflora and inoculated Bacillus spp. The tested Bacillus DFM could be considered as a best available technique in reducing the environmental impacts of growing pigs fed with high fibre-based diets.

Concerns about the environmental effect and the economic burden of methane (CH4) emissions from ruminants are driving the search for ways to mitigate rumen methanogenesis. The use of direct-fed microbials (DFM) is one possible option to decrease CH4 emission from ruminants. Direct-fed microbials are already used in ruminants mainly to increase productivity and to improve health, and are readily accepted by producers and consumers alike. However, studies on the use of DFM as rumen CH4 mitigants are scarce. A few studies using Saccharomyces cerevisiae have shown a CH4-decreasing effect but, to date, there has not been a systematic exploration of DFM as modulators of rumen methanogenesis. In this review, we explored biochemical pathways competing with methanogenesis that, potentially, could be modulated by the use of DFM. Pathways involving the redirection of H2 away from methanogenesis and pathways producing less H2 during feed fermentation are the preferred options. Propionate formation is an example of the latter option that in addition to decrease CH4 formation increases the retention of energy from the diet. Homoacetogenesis is a pathway using H2 to produce acetate, however up to now no acetogen has been shown to efficiently compete with methanogens in the rumen. Nitrate and sulphate reduction are pathways competing with methanogenesis, but the availability of these substances in the rumen is limited. Although there were studies using nitrate and sulphate as chemical additives, use of DFM for improving these processes and decrease the accumulation of toxic metabolites needs to be explored more. There are some other pathways such as methanotrophy and capnophily or modes of action such as inhibition of methanogens that theoretically could be provided by DFM and affect methanogenesis. We conclude that DFM is a promising alternative for rumen methane mitigation that should be further explored for their practical usage.

This paper reviews recent advances on the use and mode of action of probiotics (direct-fed microbials) in poultry. The addition of probiotics to the diet has been found to improve growth performance and feed conversion in broilers, and egg mass, egg weight and egg size in layers. The mode of action of probiotics in poultry includes (i) maintaining normal intestinal microflora by competitive exclusion and antagonism; (ii) altering metabolism by increasing digestive enzyme activity and decreasing bacterial enzyme activity and ammonia production; (iii) improving feed intake and digestion; and (iv) neutralizing enterotoxins and stimulating the immune system.