Indian Journal of Biotechnology
Vol 2, July 2003, pp 378-381
Effect of Lactic Acid Bacteria on Animal Performance
Zwi G Weinberg'
Forage Preservation and By-Products Research Unit, Department of Food Science, the Volcani Center,
Bet Dagan, 50250, Israel
Received 1 January 2003; accepted 20 February 2003
Lactic acid bacteria(LAB) which are included in inoculants for silage, sometimes impart beneficial effects, similar to when fed directly, on cattle performance. LABs might interact with rumen microorganisms in such a way that
their activity is enhanced and fibre degradability is improved. Another possibility is that LABs produce bacteriocins
in the silage which might inhibit detrimental microorganisms, both in the silage and in the rumen.
Key words: lactic acid bacteria, ruminants, animal performance, probiotic effects
Introduction
Ensiling, a method of preserving moist forage, is
widely used in North America, Europe, Israel and
elsewhere. It is based on natural fermentation, where
lactic acid bacteria (LAB) ferment water-soluble carbohydrates to organic acids, mainly lactic (LA), under
anaerobic conditions. As a result, the pH decreases,
inhibiting detrimental anaerobes and preserving the
nutritional value and palatability of the moist forage.
Inoculants including LABs are often used as silage
additives to enhance LA fermentation and, hence,
better to preserve the ensiled crops. Most commercially available inoculants contain homofermentative
LABs which are fast and efficient producers of LA
and thus improve the silage fermentation. Among the
homofermentative LABs, most frequently used are
Lactobacillus plantarum, Enterococcus faecium, Pediococcus acidilactici, P. pentosaceus and L. acidophilus. Heterofermentative LABs are also sometimes included in inoculants for silage, because they
produce volatile fatty acids (VFAs), which inhibit the
yeasts and moulds, which are activated upon aerobic
exposure of the silage. The recommended application
rates (105_106 viable cells/g) of these products are
usually, sufficient to enable the inoculant LAB population to overtake those of the epiphytic LABs and
become the predominant population in the silage.
Many studies involving silage inoculants have been
carried out (McDonald et al, 1991; Weinberg &
Muck, 1996).
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Effects of LAB Inoculant-treated Silage on Animal
Performance
The studies indicated that feeding cattle with silages treated with certain LABs improved ruminant
performance. Certain LABs are believed to induce
probiotic effects on humans. Improvements in animal
performance are in many cases the principal economic
justification for inoculant use. In several trials (Spoelstra, 1991; Muck, 1993), inoculants exhibited substantial effect on performance as follows: average
increases in intake, 4-11; live weight gain, 7-11; milk
production, 3-5; and feed efficiency, 9%. Inoculants
have improved animal performance in part, which
might be related to the inoculation rate. In alfalfa silages (Satter et al, 1987), an inoculation factor >10 (a
more than ten-fold increase in LABs over the natural
population) was necessary for increased milk production, a factor five times higher than that needed to
affect fermentation consistently (Pahlow, 1991).
A considerable number of animal experiments with
low dry matter (DM) grass silage inoculated with. L
plantarum MTD1, performed in Northern Ireland,
showed improvements in both silage fermentation and
animal performance. However, some studies showed
improvement in animal performance with no apparent
effect on fermentation (in some cases both the control
and treated silages were of good quality and in some
cases clostridial fermentation occurred in both) and
vice versa suggesting that effect may be probiotic.
Rooke & Kafilzadeh (1994) compared MTD 1 with
two other LAB strains. All three strains improved
fermentation similarly, but only MTDI resulted in a
significant increase in DM intake in weathers, which
WEINBERG: LACTIC ACID BACTERIA AND ANIMAL PERFORMANCE
indicates that this phenomenon might be strain specific.
In the rumen liquor of calves fed on MT01inoculated grass silage (Keady & Steen, 1994a,b,
1995), inoculation increased nitrogen degradability,
which might be related to the liberation of slowly degradable nitrogen because of modification of the cellwall structure. The inoculant treatment increased the
total ruminal VF A concentration and tended to decrease the butyrate and to increase the propionate
contents. Similar trends in low OM grass silage were
also observed (Sharp et ai, 1994) with a different inoculant, which contained strains of L. piantarum and
E. faecalis applied at 105 CFUs per gram. Studies
with other LAB inoculants had mixed results (Mayne,
1993; Smith et al, 1993).
The effects on animal performance of LAB inoculants in silages other than grass are variable. Stokes
(1992) found reduced OM intake by cattle fed on inoculated grass-legume silages and related this to the
poor aerobic stability of such silages. Kung et al
(1993), who used two different inoculants in corn silage, observed tendencies to higher fat-corrected milk
yields and higher OM intake only with MTOl, which
agrees with the results obtained in low OM grass silage. Sanderson (1993), who used corn silage inoculated with L. piantarum and E. Faecium, did not obtain any enhancement of fibre degradability. Salawu
et al (2001) observed increased rates of in situ degradation of nitrogen and fibre in bi-crop pea/wheat silage inoculated with L. piantarum and L. buchneri.
Effect of Direct-fed LABs on Animal Performance
Several trials used direct-fed LABs in ruminant
feeding. Wallace & Newbold (1993) used lactobacilli
or enterococci as probiotics in calves and lambs.
Feeding with live bacteria resulted in decreased
counts of coliforms and improvements in intake and
liveweight gain. Keady & Steen (1996) applied L.
piantarum MTO 1 to well preserved grass silage at 109
colony-forming units (CFUs) per gram and immediately fed that silage to male cattle, no significant difference was observed in OM, nitrogen and fibre degradability, rumen pH, ammonia or VFA concentrations or feed intake.
Malik & Sharma (1998) observed improved in vitro dry matter and organic matter digestibility and
higher microbial protein nitrogen following addition
of L. acidophilus to rumen liquor taken by male cattle
which were fed wheat straw and concentrate (60:40)
379
rations. Addition of an LAB culture containing L.
acidophiius, L. casei and L. jugarti to grain free diet
of growing male crossbred cattle also had beneficial
effects on weight gain and feed intake, and resulted in
lower incidence of diarrhoea (Khuntia & Chaudhary,
2002). Ghorbani et al (2002), who fed Propionibacterium and Enterococcus faecium directly to steers, observed that the directly fed microbes might have decreased the risk of acidosis in feedlot cattle.
Possible Mechanisms of the Probiotic Effect
The cause of improved animal performance is unclear. The shifts in fermentation products and small
improvements in silage OM recovery would enhance
animal performance but not to the degree observed.
Muck (1993) reported a high degree of correlation
between effects on OM digestibility and on animal
performance, and also noted that fibre digestibility
was improved in 30% of the trials. This is certainly
unexpected, in that the LABs used in inoculants are
not known to have any direct activity on polysaccharides. LABs could interact with rumen microorganisms in such a way that their activity is enhanced and
fibre degradability is improved. Weinberg et al (2003)
observed higher pH in rumen fluid, which was inoculated with the LABs used in inoculants for silage.
This trend might be associated in changes in VF A
concentration in the rumen and might explain the observation that directly fed LAB might alleviate acidosis (Ghorbani et al, 2002). The sheep, immunized
with live Streptococcus bovis vaccine, had higher rumen pH, higher feed intake and alleviated symptoms
of acidosis (Gill et ai, 2000).
LABs, that produce bacteriocins in the silage,
might inhibit detrimental microorganisms, both in the
silage and in the rumen. It is well known that certain
LAB strains produce antimicrobial substances that
inhibit other LABs or other microorganisms (Muller
et al, 1996; Odenyo, 1994a; Vandenbergh, 1993).
Conclusions and Research Needs
Silage inoculant LABs has a probiotic effect on
ruminant performance. However, the mechanism of
this probiotic effect is not as yet clear. LABs might
change the rumen environment and interact with rumen microorganisms in such a way as to enhance feed
utilization. Therefore, helpful information might be
obtained through measurements of fibre degradability
and nitrogen metabolism or through studies of the
interactions of LABs with selected rumen micro or-
380
INDIAN J BIOTECHNOL,
ganisms by means of 16S rRNA probes (Odenyo et
al, 1994a, b; Chen & Weimer, 2001). Evaluation of
the bacteriocins production by the LAB strains used
in inoculants for silage for bacteriocin production
might be another useful research direction. A relevant
question concerns whether the probiotic effect is already active in the inoculated silage or whether it is
triggered in the rumen?
The rumen system is complex and is affected by
many factors including the feed (Weimer & Waghorn,
1999), the season, the number of days in milk, and
animal variations. The probiotic effects endowed by
the LABs might be affected by such factors, and research should address this point as well.
JULY 2003
Mayne C S, 1993. The effect of formic acid, sulphuric acid and a
bacterial inoculant on silage fermentation and the food intake
and milk production of lactating dairy cows. Anim Prod, 56,
29-42.
McDonald P et al, 1991. The Biochemistry of Silage, 2nd edn.
ChaJcombe Publications, Aberystwyth, UK. Pp 184-236.
Muck R E, 1993. The role of silage additives in making high
quality silage. in Silage Production from Seed to Animal.
Northeast Regional Agric. Engng. Service, NRAES-67,
Syracuse, NY, February 23-25. Pp 106-116.
Muller T et al, 1996. Antagonistic activity in plant-associated
lactic acid bacteria. Microbiol Res, 151, 63-70.
Odenyo A A et al, 1994a. The use of 16S rRNA- targeted oligonucleotide probes to study competition between ruminal fibrolytic bacteria: development of probes for Ruminococcus
species and evidence for bacteriocin production. Appl Environ Microbiol, 60, 3688-3696.
In conclusion, certain LABs used in silage inoculants impart beneficial effects on ruminant performance. In order to make the best use of this effect, more
research is needed to achieve better understanding and
control over it.
Odenyo A A et al, 1994b. The use of 16S rRNA- targeted oligonucleotide probes to study competition between ruminal fibrolytic bacteria: pure-culture studies with cellulose and alkaline peroxide-treated wheat straw. Appl Environ Microbiol,
60,3697-3703.
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