| Livestock Research for Rural Development 21 (10) 2009 | Guide for preparation of papers | LRRD News | Citation of this paper |
It is generally accepted that certain viable microbial cultures beneficially affect the productive potentials of ruminants, pig and poultry. The species employed in probiotic preparation are mainly lactic acid bacteria for non-ruminants and for ruminants, the yeast culture (YC), Saccharomyces cerevisiae was considered as the promising probiotic culture for efficient nutrient utilization.
The research has demonstrated that viable YC preparations can stimulate specific groups of beneficial anaerobic bacteria in the rumen, and has provided mechanistic models that can explain their effects on animal performance. The effects of YC on animal productivity are strain-dependant. Many workers have reported that volatile fatty acids (VFA) production, microbial counts and microbial protein synthesis are improved due to addition of yeast culture in ruminants. Yeast culture may alter the pattern of VFA production. Supplementation with 2 specific Enterococcus faecium strains produced 2.3kg more milk/cow per day than did non-supplemented cows and early lactation cows receiving supplemental DFM (two specific Enterococcus faecium strains) produced more milk and consumed more DM during the pre- and post-partum periods. The increased milk yield was due to enhanced nutrient supply to the mammary gland rather than mobilization of body reserves. The additional DM intake provided extra energy for cows given yeast culture, which is used for milk synthesis and weight gain. Increased fat percentage in the milk from cows supplemented with direct-fed-microbial product consisting of two strains of Enterococcus faecium and Saccharomyces cerevisiae was due to increased VFA production. The feeding systems for lactating animals followed by the Indian farmers are diversified; basically the farmers are dependent on grazing/pasture land and crop residues; therefore, researchers should stress more on proper selection of probiotics/direct-fed-microbials which are effective on high fibrous diet.
Future work will allow to better understand the behaviour of the probiotics, specifically yeast culture, in the rumen and, hopefully, identify specific characteristics which will help to further select more targeted additives for improved benefits in ruminant under Indian condition.
Key words: Cow, intake, milk yield, probiotics, rumen
The concept of microbial manipulation in the gastro-intestinal tract was first appreciated by Metchnikoff (1907) who viewed the consumption of yoghurt by Bulgarian peasants as confering a long span of life. The term "Probiotics" was first coined by Parker (1974) who described this as "microorganism or substance which contribute to the intestinal microbial balance". In 1989, Fuller defined the probiotic as "a live microbial feed supplement which beneficially affects the host animals by improving its intestinal microbial balance." The term probiotic means "for life" and has a contrast with the term antibiotic which means "against life".
At present, probiotics are classified by the US food and Drug Administration as GRAS (Generally Recognised As Safe) ingredient. Now it is generally accepted that certain viable microbial cultures beneficially affect the productive potentials of ruminants, pig and poultry. The species employed in probiotic preparation are mainly lactic acid bacteria like Lactobacillus acidophilus, Lactobacillus bulgaricus, Lactobacillus lactis, Lactobacillus plantarum, Lactobacillus salivarius, Streptococcus thermophilus, Enterococcus faecium, E. faecalis, Bifidobacterium species and Bacillus subtilis.
For ruminants, the yeast culture (YC), Saccharomyces cerevisiae has been considered as the promising probiotic culture for efficient nutrient utilization. In contrast of earlier concept, the yeast and some lactic acid bacteria may survive and multiply in the anaerobic environment of rumen and intestine. Saccharomyces cerevisiae may multiply and exhibit growth in the rumen or in rumen simulating continuous cultures and confer beneficial effects on cellulolysis and productive trait of the host animal (Weidmeier et al 1987; Dawson and Newman 1988; Harris and Lobo 1988).
Growing public disquiet over the use of antibiotics in feed additives has encouraged recent commercial interest in probiotics as an alternate therapy against harmful pathogens in the GI tract, this is due to exhibited drug resistance as a result of indiscriminate use of antibiotics. The effects of specific YC preparations on the rumen environment and performance of ruminants have been well documented, and has generated considerable scientific interest over the last two decades. It is clear from these research efforts that YC supplements can beneficially modify microbial activities, fermentative and digestive functions in the rumen. The research has demonstrated that viable YC preparations can stimulate specific groups of beneficial bacteria in the rumen, and has provided mechanistic models that can explain their effects on animal performance. The effects of YC on animal productivity are strain-dependant. So, all YC preparations are not equivalent in efficiency. This aspect opens a new field of research for new strains, each being more specialized in its use. Continuous research with live YC supplements has clearly established scientifically-proven strategies for modifying and optimizing microbial activities in the gastrointestinal ecosystem and techniques for improving performance and health of ruminants. Several workers have reported that supplementation of yeast culture to the lactating cows improved milk yield or FCM yield (Hoyos et al 1987; Williams et al 1991; Kung et al 1997). Supplementation with 2 specific Enterococcus faecium strains produced 2.3kg more milk/cow per day than did non-supplemented cows and early lactation cows receiving supplemental DFM (two specific Enterococcus faecium strains) produced more milk and consumed more DM during the pre- and post-partum periods (Nocek and Kautz 2006). Bertin and Andrieu (2005) demonstrated the beneficial effect of Yea-Sacc®1026 on the performance of high-producing dairy cows. Yea-Sacc ®1026 significantly improved milk poduction among high-producing dairy cows. Dairy cows fed Yea-Sacc®1026 were better able to rebuild body stores than control cows. Kravale et al (2005) also reported that Yea-Sacc®1026 significantly improved milk yield of dairy cows, fat and protein content in cow’s milk especially during the hot season.
This article reviews the current status in relation to the effect of probiotic cultures on nutrient intake, rumen fermentation, its utilization and milk production in different ruminant species.
Nutrient supply to the animals has been improved due to yeast culture supplement at a fixed intake (Williams et al 1990), but in farm trials, its effect on intake appears the most important cause of improved performance. In several studies it has been observed that yeast culture addition increased the feed intake in lactating cows (Williams 1990; Williams et al 1991; Scott et al 1994; Dann et al 2000). In lactating cows yeast culture supplementation significantly increased the DM intake by 1.2 to 1.6 kg/day with a higher milk production (Williams 1990; Williams et al 1991). Wohlt et al (1991) observed that primiparous Holstein cows fed YC, starting 30 days prepartum and continuing through week 18 of lactation, had higher DMI around parturition and higher milk yield through week 18 of lactation versus unsupplemented cows. Robinson and Garrett (1999) observed trends to increased DMI and milk yield during early lactation for cows fed YC prepartum and postpartum. In a study with Jersey cows, Dann et al (2000) reported YC supplementation increased DMI during the transition period around calving (Wohlt et al 1998). Wohlt et al (1998) reported that an additional 10 g/day of YC at 29 days in lactation added to 10 g/day of YC fed from 30 days prepartum to 28 days in lactation increased DMI from 5 to 18 week of lactation, compared with removing the 10 g of YC/day at 29 days in lactation. The specific combination of Enterococcus faecium strains showed increased prepartum intake as well as postpartum production in high-producing dairy cattle (Nocek et al 2003).
The increased milk yield was due to enhanced nutrient supply to the mammary gland rather than mobilization of body reserves. The additional DM intake provided 11.1 MJ of ME/d extra for cows given yeast culture, which is used for milk synthesis and weight gain (Williams et al 1991). DMI is often considered to be a function of the initial rate of fibre digestion; early stimulation of ruminal activity can be expected to have a major impact on the feed consumption and can provide a driving force for improved animal performance. Such studies suggest an important role of YC supplementation in digestion in animals maintained on high forage diets (Dawson and Tricarico 2002). A positive effect of yeasts on the performance of dairy cows and on the content of milk components resulted from increased daily feed intake and improved digestibility of nutrients (Jouany 2001). The positive effect of these additives may be related to stimulation of growth of cellulolytic bacteria, which led to increased hay intake and fibre digestibility. These fungal additives appear to have enhanced digestive efficiency of buffalo calves with hay in the diet. A better digestive efficiency can reduce the weaning stress occurring during the transition from milk to solid food (Francia et al 2008). Differences in response to added yeast might have been due to interactions among yeast, diet and stage of lactation. These beneficial effects of YC on fibre digestion may be partly responsible for the increase in DM intake often observed with yeast feeding (Jouany 2006).
Harrison et al (1988), Piva et al (1993) and Scott et al (1994) have observed non-significant improvement of DMI by lactating cows fed with yeast adjunct. However, some studies indicated no added advantage of yeast culture supplementation to lactating cows on DMI (Wohlt et al 1991; Kung et al 1997; Soder and Holden 1999). In their experiment Nikkhah et al (2004) did not find the dry matter intake and milk yield in cows to be affected (P>0.05) by experimental diets but milk composition including fat and percent total solids were improved by the addition of live yeast culture (LYC). Supplementing mid-lactation cows with DFM products containing Lactobacillus acidophilus and Propionibacterium freudenreichii did not affect rumen fermentation in cows (Raeth-Knight et al 2007).
It is reported that rumen pH is mainly associated with concentration of lactic acid in the rumen (Williams et al 1991). Diets having readily fermentable cabohydrate depressed ruminal pH (Williams et al 1991), lead to reduction in number of cellulolytic bacteria (Thomas and Rook 1981), impaired forage degradation (Williams 1989a) and feed intake (Orskov et al 1978). Supplementation of Saccharomyces cerevisiae decreased the lactic acid concentration which ultimately help in elevation of ruminal pH (Williams 1989a) and sufficient to rise the pH by 0.2 to 0.5 units (Williams et al 1991), pH changes in order of 0.2 units may have considerable effect on cellulolysis when the mean pH level are low or in the region of 6.0 (Williams 1990). Nisbet and Martin (1991) has demonstrated that soluble components in Aspergillus oryzae and Saccharomyces cerevisiae culture filtrate stimulated lactate uptake by Selenomonas ruminantium and Megasphaera elsdenii. For this reason in concentrate diet there is more cellulolytic activity due to addition of yeast culture (Carro et al 1992a).
Cellulose and hemicellulose represent about 300 g/kg of most ruminant diets. These plant cell wall polymers are insoluble, structurally complex and not totally physically accessible, which explains why their degradation is sometimes limited. Moreover, the host enzymes are unable to hydrolyse this kind of molecule. Addition of yeast culture resulted into increase in concentration of total anaerobic bacteria, but the increase was associated with fibre digesting and lactic acid utilising bacteria (Dawson 1992). Yeast culture supplementation stimulate the growth of cellulolytic bacteria in the rumen (Weidmeier et al 1987; Dawson 1990; Newbold et al 1995). Addition of yeast culture in dairy cow increased total viable bacteria and cellulolytic bacteria 1.3 and 1.5 fold (Weidmeier et al 1987). Germination of zoospores from a rumen fungal strain of Neocallimastix frontalis was stimulated in vitro by Saccharomyces cerevisiae (Chaucheyras et al 1995), and the authors suggested that yeasts could enhance fungal colonisation of plant cell walls. In the same studies, cellulose filter paper degradation by Neocallimastix frontalis was also stimulated in the presence of live yeast cells. Several modes of action were identified in this effect, one being the supply of thiamine, a vitamin required by rumen fungi for zoosporogenesis. A Saccharomyces cerevisiae strain stimulated growth of Fibrobacter succinogenes S85 and reduced the lag time for growth of Ruminococcus albus 7, Ruminococcus flavefaciens FD1, and Butyrivibrio fibrisolvens D1 in vitro (Girard and Dawson 1994). Callaway and Martin (1997) showed that the same yeast could accelerate rate, but not extent, of cellulose filter paper degradation by F. succinogenes S85 and R. flavefaciens FD1. Enterococcus faecium (EF212), a lactate-producing bacterium, alone or in combination with yeast, to feedlot cattle fed a high-grain diet could improve feed digestion (Beauchemin et al 2003). Moreover, most of the polysaccharidase and glycoside-hydrolase activities increased in the presence of this yeast product (Chaucheyras-Durand and Fonty 2001). But non-significant improvement of total anaerobic and cellulolytic bacteria was observed in Holstein cows when fed yeast or mixed culture of yeast and Aspergillus oryzae (Kim et al 1992a). Plata et al (1994) demonstrated increased rumen protozoal population in steers fed oat straw based diet with Saccharomyces cerevisiae ; whereas, Kim et al (1992a) observed no response of yeast with or without Aspergillus oryzae on rumen protozoa in non-lactating Holstein cows.
One of the common observations associated with the addition of yeast culture to ruminants and in rumen simulating fermentors has been the reduction of rumen ammonia concentration (Harrison et al 1988; Newbold et al 1990; Sohn and Song 1996). The concentration of ammonia was decreased by 10 to 35 per cent in vitro (Carro et al 1992a). Similar results have been reported by Harrison et al (1988), Newbold et al (1990) and Chademana and Offer (1990) in vivo, suggesting an improved microbial capture of ammonia (Chademana and Offer 1990). Reduced ammonia levels have not been associated with decreased protein degradation or deamination (Williams and Newbold 1990). Incorporation of ammonia into microbial protein was enhanced due to supplementation of yeast (Carro et al 1992a; Olson et al 1994), which was confirmed by greater microbial yield and microbial true protein reaching the duodenum (Erasmus 1991). Erasmus et al (1992) reported higher flow of non-ammonia nitrogen (NAN), microbial-N and dietary-N to the duodenum by addition of yeast culture in the diet of lactating dairy cows. The flow of methionine increased significantly by yeast culture supplementation whereas there were non-significant improvements in the flow of lysine, phenylalanine, threonine and histidine to the duodenum of dairy cows. Many workers have reported that volatile fatty acids (VFA) production is improved due to addition of yeast culture in ruminants. Yeast culture may alter the pattern of VFA production (Martin et al 1989). The total VFA (TVFA) concentration was increased from 172.2 to 184.5 mmol/d (Harrison et al 1987). Similarly improved TVFA was observed by Martin et al (1989) who have used commercial yeast culture. In lactating cow, Harrison et al (1988) observed that there was higher production of propionate and reduction of acetate to propionate ratio due to supplementation of yeast culture. Similarly, enhanced production of propionate and reduction of acetate to propionate was reported by Plata et al (1994) and Moloney and Drennan (1994). Contrary to this Piva et al (1993) observed higher tendency of acetate production and increased acetate to propionate ratio in dairy cow fed 30% corn silage, 22% alfalfa hay and 48% concentrate.
Out of total global emission of methane (CH4) from all sources ruminants (cattle, buffalo, sheep, goat and deer) are thought to contribute 12 to 15 per cent. Therefore, methane reduction strategies offer an effective means of slowing global warming. Methane emissions from lactating Holstein cows have been reported to vary from 1.7 to 14.7% of gross energy intake, equivalent to 245 and 419 L of CH4 /day per cow (Holter and Young 1992). Grutzen et al (1986) calculated that cattle in developed countries emitted 55 kg of CH4 /year per animal in contrast to cattle in developing countries (35 kg /year/ animal). Yeast culture supplementation resulted into reduction of methane production in steers by 28% (Williams 1989a). The addition of yeast culture resulted in a lower methane production for medium concentrate diet, but higher for the high concentrate diet (Carro et al 1992a). Lynch and Martin (2002) reported a 20% decrease in methane production after a 48 h of incubation of mixed rumen microorganisms in the presence of alfalfa and a live yeast product. Studies with other yeast strains have been conflicting, reporting either no effect in fistulated sheep (Mathieu et al 1996), and in vitro (Lila et al 2004), or an increase in methane production in batch cultures with mixed rumen microflora (Martin et al 1989). Methane production of beef cattle, expressed as a proportion of gross energy intake, was not impacted by the presence of the yeast strain (McGinn et al 2004). A recent evaluation of various yeast strains in rumen-simulating fermenters on methane production reported a strong strain effect, with results ranging from no effect in one study to a 58% decrease in another (Newbold and Rode 2006). The effect of yeast culture on rumen fermentation has been summarized in the Table 1.
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Table 1. Some effects of yeast culture on rumen fermentation |
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Effect |
References |
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1. Moderated ruminal pH |
Teh et al 1987; Williams 1987; Williams et al 1991, Nisbet and Martin 1991 |
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2. Stabilized fermentation |
Harrison et al 1988 |
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3. Altered VFA production |
Teh et al 1987; Harrison et al 1987; Williams 1989a; Martin et al 1989 |
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4. Decreased ammonia concentration |
Carro et al 1992a; Sohn and Song 1996 |
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5. Increased concentrations of anaerobic bacteria and cellulolytic bacteria |
Weidmeier et al 1987; Harrison et al 1988; Dawson et al 1990; Kim et al 1992a; Newbold et al 1995 |
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6. Enhanced microbial protein synthesis |
Weidmeier et al 1987; Chademana and Offer 1990; Carro et al 1992a; Olson et al 1994; Erasmus et al 1992 |
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7. Reduced methane production |
Williams 1989a; Carro et al 1992a, Lynch and Martin 2002 |
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8. Increased concentrations of yeast in the populations |
Dawson et al 1990; Newbold et al 1990 |
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9. Decreased lactic acid concentration |
Williams 1989a |
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10. Altered digestive patterns |
Chademana and Offer 1990; Malik 1993; Newbold et al 1995 |
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11. Decreased soluble sugar concentrations |
Williams 1989a |
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12. Increased ethanol concentrations |
Bruning and Yokoyama 1988 |
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13. Increased propionate and decreased acetate |
Harrison et al 1988; Plata et al 1994; Moloney Drennam 1994 |
A number of studies provided evidence that live yeast cells enhance the digestive process in the gastrointestinal tract. Supplementation of Saccharomyces cerevisiae increased the digestibility of protein (Wohlt et al 1991; Kim et al 1992b), cellulose (Gomez-Alarcon et al 1987; Wohlt et al 1991), fibre (Weidmeier et al 1987; Gomez-Alarcon et al 1990), NDF (Kim et al 1992b; Plata et al 1994 ) and ADF (Kim et al 1992b). Similarly, Weidmeier et al (1987) observed that supplementation of yeast culture increased hemicellulose and CP digestibility in ruminants. DM digestion in the rumen of dairy cows was increased receiving yeast culture (Gomez-Alarcon et al 1987). A significant (P<0.05) improvement (P<0.05) in the digestibility of nutrients had been observed on supplementation with Lactobacillus acidophilus in crossbred calves (Das et al 2001). Carro et al (1992a) reported that effect on digestibility is dependent on the forage to concentrate ratio, supplementation of yeast culture with high concentrate diet resulted in significantly higher DM and NDF digestibilities in rumen (Rusitech). However, on high forage diet yeast culture had no effect on DM, NDF and cellulose digestibility. In another study by Kim et al (1992b); CF, ADF and NDF digestibilities were significantly improved due to supplementation of yeast to lactating cows. Bhoi (1992) has shown that the fibre digestion was better in the combined culture of yeast and Lactobacillus acidophilus in goats as compared to individual ones. Supplementation of Saccharomyces cerevisiae alone or alongwith Lactobacillus acidophilus increased the in vivo DM and CF degradability (Malik 1993). The effect of different doses of live YC (LYC) (Saccharomyces cerevisiae , strain SC-47) (0, 3, 6 and 12 g of yeast/day respectively) on the lactation performance of Holstein dairy cows was described by Nikkhah et al (2004). Williams et al (1991) also indicated that the initial rate of degradation, rather than the potential degradability of the forage, was affected. Yeast supplementation significantly (P < 0.05) increased digestibility of dry matter (DM), organic matter (OM), crude protein (CP), NDF and ADF of tomato pomace where the gross digestibility derived from the supplementation (4 g yeast) was superior to the control group (Paryad and Rashidi 2009). Kobayashi et al (1995) have observed that concentrations of free methionine, arginine, lysine and isoleucine in blood plasma were significantly higher in early lactation cows fed the yeast culture, suggesting a greater rate of essential amino acid absorption in these cows. Baker’s yeast enhanced cell wall degradation of berseem hay and dramatically reduced the lag time of digestion as a result of its direct enhancement of cellulase activity (El-Waziry and Ibrahim 2007). Digestible organic matter (DOM) intake and TDN intake per kgW0.75 were significantly (P<0.01) higher in crossbed cows feed with combined DFM culture (yeast, lactobacilli and streptococci) (95.02 and 99.55 g) over control (89.41 and 93.68 g) (Dutta and Kundu 2008).
Supplementation of Lactic acid bacteria increased the bioavailability of calcium, magnesium, phosphorus and zinc from all diets (Schaafsma et al 1988), when consumption of lactic acid bacteria resulted into increased bone calcium and improved bone formation (Kaup 1988).
Some studies (Williams 1989a, b; Chademana and Offer 1990) revealed that DM digestibility was not changed by addition of yeast culture, suggesting that the effects of yeast on digestion may be very subtle and can not easily be identified in studies of total tract digestibility (Williams 1989a, Gomez-Alarcon et al 1990) but influences the initial digestion rates of fibrous substrate in the rumen (Dawson 1992). In lactating Holstein cows addition of yeast culture had similar effect on DM, NDF, ADF and hemicellulose digestibilities but CP and cellulose digestibility tended to be improved (Wohlt et al 1991). Few reports have indicated that addition of yeast culture to ruminants had no added advantage on the digestibility of OM (Chademana and Offer 1990), NDF (Chademana and Offer 1990; Carro et al 1992b; Kim et al 1994), ADF (Carro et al 1992b; Kim et al 1994), CP (Kim et al 1994), cellulose (Carro et al 1992b), hemicellulose (Harrison et al 1988) and starch (Harrison et al 1988). Jung and Varel (1987) noted that increased number of cellulolytic bacteria did not correspond to increases in digestion of cell wall, cellulose or hemicellulose. Supplementating mid-lactation cows with DFM products containing Lactobacillus acidophilus and Propionibacterium freudenreichii did not affected cow performance and diet digestibility (Raeth-Knight et al 2007). The YC had no effect (P > 0.05) on dry matter (DM), neutral detergent fiber (NDF) or non-fibrous carbohydrates digestibility (Kawas et al 2007).
Several workers have reported that supplementation of yeast culture to the lactating cows improved milk yield or FCM yield (Williams et al 1991; Kung et al 1997). European commercial farm trials demonstrating the effect of including Yea-Sacc in the diet of dairy cows on milk yield revealed that there was increase in milk yield in maximum cases. However, in some cases the effect was not so prominent (Williams 1989c). Dobos et al (1989) showed that addition of Yea-Sacc increased milk yield. The increase in the milk yield in dairy cows (William et al 1991) and buffaloes (Kumar et al 1992a and b) on supplementing diet with yeast culture may be due to the changed rumen parameters. Gunther (1989) has shown the same trend in dairy cows indicating that the inclusion of Yea-Sacc increased FCM from 30.10 kg/day to 35.35 kg/day. Milk production by primiparous Holstein cows fed corn silage:grain (1:1, DM basis) and hay (0.9 kg/d) improved by the addition of yeast culture (Wohlt et al 1991). The effect of LYC supplementation on the performance of dairy cows during the transition period was studied by Nocek et al (2003). During the postpartum period, dry matter intake, milk yield, and milk protein content were higher in cows receiving direct-fed microbial supplementation compared with the control group. Doreau and Jouany (1998) and Zheng et al (2000) also reported that the addition of LYC (Saccharomyces cerevisiae ) into the feeding ration of dairy cows improved their milk production performance significantly. The effect of the strain SC I1077 on milk production was largely dependent of the type of diet (Sniffen et al 2004). Dawson and Tricarico (2002) analyzed the results gained from 22 studies with Yea-Sacc1026 involving more than 9039 lactating dairy animals. He found an average increase in milk production of 7.3% in yeast-supplemented animals. Responses to supplementation were variable and ranged from 2 to 30% increase in milk production. The improvement of milk production was 1.8 l in the controlled experiments which is probably significant. It became 1.4 l in the field studies. Formigoni et al (2005) reported that Yea-Sacc®1026 improved significantly the DMI and milk yield of dairy cows, on the overall period, but also, during heat stress period. Yea-Sacc ®1026 improved significantly the composition of cow’s milk, including fat (P<0.01) and protein (P<0.05) content. Bertin and Andrieu (2005) demonstrated the beneficial effect of Yea-Sacc®1026 on the performance of high-producing dairy cows. Yea-Sacc ®1026 significantly improved milk poduction among high-producing dairy cows. Dairy cows fed Yea-Sacc®1026 were better able to rebuild body stores better than control cows. Kravale et al (2005) also reported that Yea-Sacc®1026 significantly improved milk yield of dairy cows, fat and protein content in cow’s milk especially during the hot season. Economic results of the dairy herd were improved in the Yea-Sacc®1026 group in comparison with untreated control. Many other investigations demonstrated a significantly positive effect of Yea-Sacc® 1026 on milk production of dairy cows (Sinclair et al 2006; Tricarico et al 2006), lactating buffalo (Agovino 2006), dairy sheep and goats (Sara et al 2004; Spruzs and Selegovska 2004). Reklewska et al (2000) and El-Ghani (2004) reported that goats fed yeast culture had a significantly higher milk yield. The lactating Zaraibi goats had higher (P<0.05) milk yield, and contents of milk energy, protein, total solid and solid not fat (SNF) than the control goats (El-Ghani 2004). Supplemented with 2 specific Enterococcus faecium strains produced 2.3kg more milk/cow per day than did non-supplemented cows and early lactation cows receiving supplementatal DFM (two specific Enterococcus faecium strains) produced more milk (Nocek and Kautz 2006). Feeding Saccharomyces cerevisae (CNCM I-1077) to early lactating dairy goats determined a positive significant effect of 0.3 kg of milk yield per day. The higher milk production can be related to the higher feed intake of treated goats. No effect on body condition score was observed when Saccharomyces cerevisiae was administered (Stella et al 2007). Supplementation of mixed culture (Saccharomyces cerevisiae -NCDC-47, L. plantarum-NCDC-25 and Enterococcus faecium-NCDC-124, total dose, 10×109, ratio 6:2:2) to crossbred lactating cows increased milk and FCM yield with higher fibre digestibility, DCP and TDN intakes (Dutta and Kundu 2008).
According to Chevaux and Fabre (2007) LYC supplementation in the diet of dairy goat and sheep had a positive effect on reducing the somatic cell count in milk. When the goats received live yeast products and especially (Saccharomyces cerevisiae SCI-1077) their fecal E. coli population decreased, while total Lactobacilli population –the “friendly bacteria”, significantly increased. The authors suggest that the increased Lactobacilli level in treated animals may have been responsible for the reduction in level the opportunistic pathogen E. coli, not only through pH control, but also by competing for receptors at the surface of the gut, thereby improving the stability of the intestinal ecosystem.
Some workers reported that milk yield was unaffected by the addition of yeast culture to the diet of cows (Kim et al 1992b; Higginbotham et al 1994). Milk production, 4% fat-corrected milk, energy-corrected milk and DM intake were similar for cows fed control and yeast culture diets (Schingoethe et al 2004). Milk yield was not significantly different in Holstein cow supplemented with Saccharomyces cerevisiae or Aspergillus oryzae, whereas, milk fat per cent increased due to addition of these culture (Kim et al 2006). There were no differences in milk yield and DM intake in dairy cattle due to supplementation of yeast culture (Bach et al 2007). Dawson (1993) stated that yeast culture supplements did not have equal beneficial effects with all types of diets, and it is currently not possible to define the dietary conditions that provide optimum response to yeast culture supplementation.
Under farm trials, it has been observed that there was positive response on total butterfat production due to addition of Yea-Sacc in dairy cows (Williams 1989c). Gunther (1989) has observed significant improvement in butterfat percentage in dairy cows due to yeast supplementation. Teh et al (1987) found that both yeast culture and NaHCO3 increased milk fat percentage in early lactation goats. Other authors have also observed significant improvement in milk fat percentage of lactating cows due to supplementation of yeast culture (Piva et al 1993; Putnam et al 1997). Addition of mixed microbial culture to the lactating cows improved significantly milk fat percentage in the top producers (averaging 19.4% higher) and in the lower producing cows (averaging 14% higher) (Hoyos et al 1987). Slightly higher milk fat test has been observed by some workers in lactating cows when supplemented yeast culture as feed additive (Williams et al 1991; Kung et al 1997). Williams et al (1991) have noticed that milk fat percentage slightly improved only in high concentrate diet (60%). Oetzel et al (2007) reported that the increased fat percentage in the milk from cows supplemented with direct fed microbial product consisting of two strains of Enterococcus faecium and Saccharomyces cerevisiae was due to increased VFA production. El-Ghani (2004) and Giger-Reverdin et al (1996) reported higher milk fat content in early lactating dairy goats fed Saccharomyces cerevisiae and hence greater fat-corrected milk yield was recorded.
Some other authors did not record any difference in milk fat percentage due to yeast culture supplementation (Wohlt et al 1991; Scott et al 1994; Swartz et al 1994; Higginbotham et al 1994). No difference in fat-corrected milk was observed in cows when supplemented with two specific Enterococcus faecium strains (Nocek and Kautz 2006). Dietary supplementation of mixed microbial cultures (yeast, lactobacilli and streptococci) occasionally improve the fat content in milk of crossbred cows; however, average fat percentage was statistically similar between control and DFM fed group (Dutta and Kundu 2008).
Gunther (1989) has observed significant improvement in milk protein in dairy cows using Yea-Sacc and higher milk protein was reported by Williams et al (1991) and Putnam et al (1997), but daily milk protein increased only in cows when given high concentrate diet plus yeast culture (Williams et al 1991) and altered by a significant diet treatment interaction. Oetzel et al (2007) studied that the increased protein percentage in the milk from cows supplemented with direct fed microbial product containing of two strains of Enterococcus faecium and Saccharomyces cerevisiae was due to increased VFA production. Yeast culture supplement in early and mid lactation cows increased milk protein by a mean of 5% and 8% respectively (Kobayashi et al 1995). Similarly, milk protein enhanced in early lactating cows supplemented with yeast culture on low CP (16.1%) diet (Putnam et al 1997). A culture of one or more viable non-pathogenic lactic acid producing bacteria (Lactobacillus, Streptotoccus, Pediococcus, Leuconostoc), amylase and proteinase-producing bacteria (Bacillus subtilis or Bacillus toyoi) were blended with a protein carrier (dried milk, amino acids) or carbohydrate carriers (Starch, cellulose, sugar) and given to the milk producing ruminants at a daily rate of 103 - 105 cfu/animal. It was claimed that this facilitated optimum growth of the bacteria in the stomach/intestine system of the animal and increased the protein content of the milk (Kvanta and Fischier 1989).
Some workers reported the reduction in milk percentage of milk protein in cows, when supplemented with yeast culture additive in its diet (Harris and Lobo 1988; Adams et al 1995). However, some researchers revealed no added advantage of yeast culture treatment to lactating cow on milk protein per cent (Higginbotham et al 1994; Kung et al 1997). Protein content in milk of crossbred cows was not influenced by the addition of mixed probiotics culture to lactating crossbred cows (Dutta and Kundu 2008). This variability of results may be due to behaviour of yeast culture, nature of ration, stage of lactation or interaction of these factors.
Very limited reports are available on the effect of yeast culture influencing milk lactose percentage in lactating cows. Kim et al (1992b) have reported significant improvement of milk lactose percentage in early to mid lactating dairy cows when supplemented with yeast culture. Commercial preparation of yeast culture (Yea-Sacc) had no positive response on lactose per cent in milk of dairy cows (Huber et al 1989). Similar type of observation was recorded by Arambel and Kent (1990), Scott et al (1994) and Kim et al (1994) who have also shown no added effect of yeast culture on milk lactose percentage in dairy cows. Whereas, percentage of lactose was lower for cows fed yeast culture plus Aspergillus oryzae (Higginbotham et al 1994).
Feed additives such as direct-fed-microbials can expect a promising future in ruminant nutrition due to its beneficial effects and no residual effect on the animal products. In India, the use of probiotics or direct-fed-microbials is limited for increased milk production in dairy animals. The probiotics are mainly used in poultry production in India. Controlled research studies indicate that probiotics can be useful to positively balance digestive microflora, improvement of animal production and health. Use of direct-fed-microbials appears particularly relevant when the digestive microbiota is challenged, for example during a feed transition such as weaning, grazing, supply of high-concentrate diets, or during periods of stress such as hot temperature or transportation. However, as substantial differences have been reported in response of the ruminal microbiota to yeast additives, care must be taken in the way that the yeast strain is selected. The direct-fed-microbials were fed relative to animal, rather than relative to DM intake, meaning that animals with higher DM intakes consumed less YP per kg of DM intake. The feeding systems for lactating animals followed by the Indian farmers are diversified; basically the farmers are dependent on grazing/pasture land and crop residues; therefore, researchers should stress more on proper selection of probiotics/direct-fed-microbials which are effective on high fibrous diet. Future work will allow to better understand the behaviour of the yeast cells in the rumen and, hopefully, identify specific characteristics which will help to further select more targeted additives for improved benefits in ruminant nutrition.
There should be systematic study to select promising DFM which are effective in different Indian dairy animals under different agro-climatic zones. Use of probiotics for higher buffalo milk production is a promising area of research in India. India has wide genetic diversity of different dairy animals like cows, buffaloes, goats, sheep and camels. The selection of DFM should be species and breed oriented under high fibre dietary regimen.
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Received 25 June 2009; Accepted 6 July 2009; Published 1 October 2009