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Growing of public concerns towards use of antibiotics in animal feeding paved the way for probiotics utilization enlargement. Lactic acid bacteria (LAB) as a probiotic could improve dairy animal’s performance through prevention of ruminal acidosis; stimulate digestive enzymes production and secretion and stimulate animal’s immune system. The actions of LAB are species and strain specific and depend on their availability and viability in the host animal gastrointestinal tract. Therefore, the current review focus on impact of LAB on dairy animal’s feed intake, ruminal fermentation, nutrients digestibility, blood metabolites, milk yield and milk composition.
Improve dairy animal’s health and its productive performance has always remained a primary goal of researchers associated with the dairy animal production. This goal could be achieved by making desirable manipulation of rumen fermentation through using probiotics. Probiotics are live microbes beneficially affects the host animal by improving microbial balance of its gastrointestinal tract . Probiotics are broad and may include fungi, bacteria and yeast cells. Most of bacterial probiotics preparations are containing lactic acid bacteria (LAB) like Lactobacillus acidophilus, Lactobacillus plantarum, Streptococcus bovis, Streptococcus faecium, Enterococcus faecium and Enterococcus faecalis . Lactic acid bacteria (LAB) are gram-positive, acid-tolerant, either rod-shaped (bacilli) or spherical (cocci) bacteria. These bacteria are naturally found in the gastrointestinal tract (GIT) of the ruminants, produce lactic acid as the major metabolic end product of carbohydrate fermentation. The positive effects of LAB on dairy animal’s performance have been reported [1-3], but the actions of LAB are species and strain specific and depend on their availability and viability in the host animal GIT. There are many mechanisms have been proposed to explain LAB positive effects including: A) antagonist the harmful bacteria in GIT through production of lactic acid and bacteriocins ; B) compete with pathogens for adhesion and nutrients sites ; C) stimulate animal’s immune response through activate phagocytosis and natural killer cells ; D) detoxification of GIT toxins  and E) stimulate digestive enzymes production and secretion .
However, LAB might help for prevention of ruminal acidosis, by allowing the ruminal microflora to adapt to the presence of lactate in the rumen . As the energy issue is so critical for dairy animals in early lactation, LAB inclusion could promote nutrients uptake through decrease the thickness of the inflamed intestinal wall, as well as improve feed efficiency by diminish the amount of energy used for GIT tissue turnover . There is an enlargement in utilization of probiotics (e.g. LAB) as a feed additive has been noticed. This may be due to grow of public concerns towards use of antibiotics in animal feeding . The EU already bans use of antibiotics as animal’s growth promoters in 2003 to avoid their harmful effects on both animal’s and human immune system . It is worth to mention that the volume of probiotic market reached $33.19 billion in 2015 and expected to reach $46.55 billion in 2020 which reflecting the importance of the probiotics. Therefore, the current review will focus on the impact of LAB as a main bacterial probiotic on the dairy animal’s performance
In general supplementing dairy animals with LAB has been shown to improve feed efficiency with little change in dry matter intake (DMI) . In this concern, cows fed mixture of L. acidophilus, L. casei, E. faecium and mannanoligosaccharide consumed 0.42kg/d less DM and produced 0.73 kg/d more milk . Moreover, feeding dairy cattle combination of L. acidophilus (LA747), L. acidophilus strains (LA45) and P. freudenreichii
(PF24) had no effect on DMI . Also, no effect was detected for
Lactobacillus acidophilus (109 CFU/g) supplementation on DMI by
lactating Holstein cows .
It has been reported that supplemented dairy cows with
LAB (Bacillus subtilis natto) lead to increase ruminal total VFA
concentrations especially propionate [14,15]. Since propionate is
the precursor for gluconeogenesis and increase its concentration
in the rumen mean more glucose availability. In contrast, Holstein
cows treated with L. acidophilus and P. freudenreichii did not
show any change on their ruminal total VFA’s and ammonia
In general, lactic acid bacteria inclusion in ruminant’s
diets has led to improve nutrients digestibility. In this concern,
cows supplemented with B. licheniformis showed significant
differences in OM, CP, NDF and ADF digestibility coefficients .
Also, apparent total tract digestibilities of DM, OM, CP, CF and
NFE for goats fed lactobacillus acidophilus showed significant
improvement compared with those of the control . In contrast,
neutral detergent fiber (NDF), protein or starch digestibility not
change due to addition of LAB to animals’ diets .
lactating dairy cows suffering a negative energy balance during
early lactation because the energy output in milk is greater than
energy intake from feed; therefore, cows mobilize fat reserves to
meet their energy requirements and this led to marked change
in their blood metabolites. Positive effect of LAB (Enterococcus
faecium) on availability of energy for postpartum cows has been
reported . The treated cows showed higher blood glucose
and insulin concentrations . In addition, it has been noticed
that cows supplemented with Bacillus subtilis natto showed low
concentration of blood non-esterifies fatty acids (NEFA) which
indicates that cows are mobilizing less energy from adipose
deposits to meet their energy requirements . Less subclinical
ketosis has been observed after calving in cows consuming
Bacillus pumilus in their diets . These reports show that LAB
has potential to make the diet more energetically favorable for
cows during the transition period.
Commonly, LAB inclusions in dairy animal’s diets lead to
increase milk yield with little effect on milk composition. Several
studies on dairy animals fed combination of L. acidophilus. L.
plantarum, L. casei and S.faecium concluded that animal’s milk yield
increased by 0.75 to 2.0 (kg/d) . Cow’s milk yield increased by
2.3 kg/d after their treatment with a combination of Enterocccus
faceium, Lactobacillus plantarum, and Sacchormyces cerevisiae
. Moreover, mean daily yields of 4.0% fat corrected milk (FCM)
were significantly increased by cows fed diet supplemented with B.
licheniformis but not for Bacillus subtilis . Also, cow’s milk yield
increased by 3.2 kg/d with Bacillus subtilis natto supplementation
. In addition, goat’s milk, 4% FCM and the other components
yields were higher with lactobacillus acidophilus supplementation
. However, somatic cell count (SCC) decreased beside increase
milk yield has been observed for treated cows with mixture of
Lactobacillus casei and Lactobacillus plantarum P-8 . This
suggested that such treatment can reduce mammary gland
inflammation and subsequently increase animal’s milk yield.
Lactic acid bacteria inclusion in dairy animals’ diets lead to: A)
improve feed efficiency with little change in dry matter intake. B)
Increase ruminal total VFA concentrations especially propionate.
C) Improve nutrients digestibility and, D) Increase milk yield with
little effect on milk composition.