Summer M. Russell
Department of Poultry Science
North Carolina State University
Raleigh, NC,
USA
There is public concern about the use of antibiotic growth promoters (AGP) for poultry creating an interest in alternatives such as direct fed microbial (DFM) and other pro-biotic type products. Therefore, one university trial and three field trials were conducted to determine if DFMs are potential candidates to AGP for rearing turkeys. The two products used were PrimaLac® (Star Labs, Clarksdale, MO, USA) and ALL-LAC DC7® (Alltech, Inc., Nicholasville, KY, USA).
PrimaLac® is a DFM product that contains Lactobacillus acidophilus, L. casei, Bifidobacterium bifdium, and Enterococcus faecium which remain viable post-pelleting. PrimaLac® contains a minimum of 1.0 x 108 CFU of Lactobacillus sp. organisms per gram.
ALL-LAC DC7® is a DFM that contains Enterococcus faecium, L. acidophilus, L. fermentum, B. longum, L. casei, L. plantarum, and Pediococcus acidilactici. ALL-LAC DC7® contains a minimum of 100 billion CFU per gram.
In a university trial, typical turkey diets were formulated with and without PrimaLac®. All feed was provided by a commercial feed mill.
BUTA T2 (Lewisburg, WV, USA) Large White male turkey poults (18/pen) were placed in 48 pens (24 pens/treatment) on day of hatch and were reared to 20 wk. Feed consumption (by pen) and body weight were determined at 3, 5, 8, 10, 12, 15 & 20 wk. Feed conversion (FC) was calculated. Data were analyzed using the General Linear Model procedure of SAS, Inc. The LS Means procedure was used to separate treatment means (P≤0.05). Cumulative FC was significantly improved for birds fed DFM compared to birds fed control feed from 3 to 20 wk (20 wk FC; DFM=2.52, Control=2.59 + 0.02). Body weight was significantly greater for birds fed DFM versus control fed birds through 12 wk (9.5 versus 9.2 + 0.1 kg) but not at 15 wk (13.6 versus 13.5 + 0.1 kg) or 20 wk (21.1 versus 21.0 + 0.1 kg).
Three field trials were conducted, two with PrimaLac® and one with ALL-LAC®. In each trial two brooder and four grow-out houses were paired on a farm. All birds received the same feed provided by the integrator which contained AGP. The DFM was provided in the water from placement to market in one brooder house and two matching grow-out houses. Breeder flocks were equally represented in both brooder houses within a trial. There were approximately 12,000 male poults placed in each brooder house. They were transferred to two grow-out houses at 5 wk of age. Across the three trials, mean liveability was increased from 84.2 to 87.0%, mean body weight was increased from 13.6 to 14.1 kg, mean total weight removed from the farms was increased by 9500 kg, mean FC was improved from 2.61 to 2.53, and cost of production was reduced (mean reduction =$US 0.015 per lb live weight) by the DFM. In conclusion, some DFM products can be viable alternative candidates to AGP for rearing turkeys.
Introduction
Feed borne antibiotic growth promoters (AGP) have been fed to livestock in the US and other countries for about 50 years to improve growth performance (Dibner and Richards, 2005). Early indications of improved performance in poultry were reported in 1946 (Moore et al., 1946). Poultry have been fed AGP during the rearing period to protect them from pathogenic organisms, maintain health, improve growth efficiency and improve meat quality and wholesomeness. However, antibiotics have come under increasing scrutiny by some scientists, consumers, activists, politicians, and bureaucrats because of the argued potential development of antibiotic-resistant bacteria (including pathogenic strains) after long use of AGP in livestock and poultry feed. Antibiotic resistance displayed by field Escherichia coli isolates from North Carolina commercial turkey farms has been reported, including resistance to Enrofloxacin, one of the most recently approved antibiotics for use in poultry (Fairchild et al., 1998). However, most of the AGPs have no specific claims to control disease (Gustafson and Bowen, 1997). Debate over resistance observed among bacteria such as E. coli and Salmonella has generated the strongest objection to antibiotic use (Evagelisti et al., 1975; Scioli et al., 1983; Gustafson and Bowen, 1997). It has been reported that antibiotic resistance of indigenous E. coli of poultry has remained at a relatively high level since the 1950's (Gustafson and Bowen, 1997).
In the US, reports from the Institute of Medicine, the Council for Agricultural Science and Technology and a Committee on Drug Use in Food Animals recommended reduction or elimination of AGP in livestock feeds even though none of these reports provided data proving that AGP resistant microorganisms were responsible for antibiotic-resistant infections in humans (Dibner and Richards, 2005). Although this debate continues, there is interest in developing alternatives to AGP, such as probiotics. The term "probiotic" can refer to feed additives other than live cultures such as non-digestible feed ingredients that enhance host digestive tract microflora (Fuller, 1989). This would include many of the indigestible sugars such as oligosaccharides (Patterson and Burkholder, 2003).
Therefore, the Association of American Feed Control Officials (AAFCO, 1999) and the US Food and Drug Administration (FDA, 2003) have recommended the term "direct-fed microbials" (DFM) be used to describe live culture feed additives (Elam et al., 2003). Other types of probiotics that are not live cultures have been referred to as "prebiotics" (Patterson amd Burkhold, 2003).
Probiotics have been developed to counter the growth depressing effects that certain strains of bacteria elicit in poultry. There are numerous reports of DFM, including Lactobacillus spp., being fed to poultry including turkeys. However, there are few reports where the feed, containing the DFM, has been pelleted or of DFMs used in commercial poultry operations.
Therefore, the objective of this study was to determine, in two university trials and three field trials, if DFMs are potential candidates to AGP for rearing Large White commercial turkeys.
Materials and methods
The two products used were PrimaLac® and ALL-LAC DC7®. The PrimaLac® was used in two university trials and in two of three field trials while the ALL-LAC DC7® was used in one field trial. PrimaLac® (Star Labs/Forage Research, Inc., Clarksdale, MO, USA) is a DFM product that contains Lactobacillus acidophilus, L. casei, Bifidobacterium bifdium, and Enterococcus faecium which remain viable post-pelleting. PrimaLac® contains a minimum of 1.0 x 108 CFU of Lactobacillus sp. organisms per gram.
ALL-LAC DC7® (Alltech, Inc., Nicholasville, KY, USA) is a DFM that contains Enterococcus faecium, L. acidophilus, L. fermentum, B. longum, L. casei, L. plantarum, and Pediococcus acidilactici. ALL-LAC DC7® contains a minimum of 100 billion CFU per gram.
Two university trials were conducted. In both trials, all birds were reared and handled by methods approved by the Institutional Animal Care and Use Committee. In trial one, 18 BUTA T2 (Lewisburg, WV, USA) Large White male turkey poults were placed in each of 48 pens (24 pens/treatment; 64 ft2/pen) on day of hatch. The pens were arranged into four rows that served as blocks with 12 pens per row.
For trial two, Hybrid Converter® (Kitchner, Ontario) Large White hens were reared in the same facility after a total clean-out. The same treatments were applied in the same design as trial one. There were 30 day of hatch hen poults started per pen. The area in each pen was restricted with a wire partition to approximately 40 ft2. This provided 1.3 ft2 per bird during brooding. At six week of age the partition was removed providing 2.1 ft2 per bird. Typical turkey diets were formulated with and without PrimaLac®. Feed samples were analyzed to ascertain that the treatment feed contained the DFM and that the control feed did not. The DFM was fed at 1 g/kg through 8 wk of age and then 0.5 g/kg until market age. Each treatment was replicated six times per row. All feed was provided by a commercial feed mill and was formulated to meet or exceed NRC recommendations (NRC, 1994).
The PrimaLac® was added in the mixer and then the feed was pelleted. The pelleted feed was crumpled through six weeks of age and then feed was offered in pellet form. Birds were offered feed and water ad libitum. Feed was provided using one 22-kg capacity tube feeder per pen. Lighting was provided 23 hours per day for the first week. Beginning with the second week, lighting was by natural day-length. Heat lamps provided heat for each pen while gas fired heaters provided background room heat. Mortality and culled birds were recorded by pen.
Body weight and feed consumption, by pen, were measured at all data collection dates: 3, 5, 6, 8, 10, 12, 15, and 20 weeks in trial one, and 1, 3, 5, 6, 8, 10, 12, 14, 16 and 18 weeks in trial two. Body weight was measured in trial one by pen at 3 and 5 weeks and at 1 and 3 weeks in trial two.
Individual body weights were taken at all subsequent weight dates in each trial. Period and cumulative feed conversions were calculated. Period and cumulative feed consumption and feed conversion (FC), adjusted for mortality and culled birds, were determined for each of these periods. The data were subjected to the General Linear Models procedure (SAS, 1992). The pen served as the experimental unit. Variables having a significant F-test were compared using the LS Means function of SAS (SAS, 1992) and considered to be significant at P < 0.05.
Three field trials were conducted, two with PrimaLac® and one with ALL-LAC®. In each trial two brooder and four grow-out houses were paired on a farm. All birds received the same feed provided by the integrator which contained AGP.
The DFM was provided in the water from placement to market in one brooder house and two matching grow-out houses. Water samples were taken from each house to ascertain that the water contained the appropriate DFM and that the control houses did not. Breeder flocks were equally represented in both brooder houses within a trial. There were approximately 12,000 male poults placed in each brooder house. They were transferred to two grow-out houses at 5 wk of age and reared to approximately 18 weeks of age.
Results
Trial 1: Mean body weight (Table 1) was significantly greater for tom turkey fed DFM versus control fed birds through 12 wk (9.5 versus 9.2 + 0.1 kg) but not at 15 wk (13.6 versus 13.5 + 0.1 kg) or 20 wk (21.1 versus 21.0 + 0.1 kg). However, mean cumulative FC (Table 1) was significantly improved for birds fed DFM compared to birds fed control feed for the entire trial from 3 to 20 wk (20 wk FC; DFM=2.52, Control=2.59 + 0.02).
Trail 2: Mean body weight (Table 2) of hen turkeys fed DFM was greater than control fed birds through 8 weeks and again at 12 weeks (DFM=6.36, Control= 6.29 + 0.02). Mean body weights were not different from 14 to 18 weeks of age. Mean cumulative FC (Table 2) was improved for hens fed DFM through 8 weeks of age (DFM=1.39, Control=1.41 + 0.01).
Field Trials: Across the three field trials, mean liveability was increased from 84.2 to 87.0%, mean body weight was increased from 13.6 to 14.1 kg, mean total weight removed from the farms was increased by 9500 kg, mean FC was improved from 2.61 to 2.53, and cost of production was reduced (mean reduction =$0.007 per kg live weight) by the DFM (Table 3).
Discussion
The use of AGP became widespread for rearing livestock and poultry because of the benefits they afford to the producer, the animal, and the environment, as well as the consumer (Gadd, 1997). Specific benefits of feeding AGP to poultry by producers include improved feed efficiency and increased body weight gain. However, controversy over the feeding of antibiotics as growth promotants in many countries has increased because of the fears concerning the development of antibiotic resistant microbes from the use of AGP in food animals.
Trade with the European Union along with the uncertain future of feeding AGP in the US poultry industry (and possibly other countries) makes it prudent for US producers to seek alternatives to AGPs. In addition, while the use of DFM in research trials is not new, interest in their use has been renewed or increased due, in part, to consumer pressure and the political climate (Dibner and Richards, 2005).
Success of DFM fed to turkeys varied in early reports. Carlson et al. (1979) fed a microbial preparation to turkey hens and toms to 24 week of age without any observed effect on body weight or feed conversion. Potter et al. (1979) reported that Medium White turkeys fed L. acidophilus were heavier than controls at 8, 10 and 12 but not 16 weeks of age. Feed efficiency was not affected. Francis et al. (1978) fed a mixture of L. acidophilus and other Lactobacilli alone or in combination with zinc bacitracin to Broad Breasted Large White turkeys in battery cages to 3 weeks of age. There were "numerical" but not significant improvements in body weight and feed efficiency due to feed treatments. Damron et al. (1981) fed a probiotic to Large White turkey breeder hens in two experiments but did not observe any effect on reproductive performance.
However, other reports agree with the findings reported here. England et al. (1996) sprayed male Large White turkey poults with L. reuteri and included the L. reuteri in the feed with or without bacitracin methylene disalicylate (BMD) to 126 days of age. The DFM treated birds were significantly heavier at 126 days than control fed birds (15.1 versus 14.8 kg). There was no effect due to BMD. When adjusted to equal body weights, birds fed L. reuteri were determined to have an improvement in feed conversion of 2.678 versus the controls, which had a feed conversion of 2.734.
Owings (1992) fed four concentrations (100, 1,000, 10,000, or 100,000 cfu/g) of a microbial preparation of selected and proprietary Streptococcus spp., plus a control, to male Large White turkeys from 1 to 126 days of age. There was no effect of diet on 126 d body weight. However, the birds fed the 10,000 cfu/g treatment had improved feed conversion versus the control (3.12 versus 3.23). The others were intermediate.
Jiraphocakul et al. (1990) conducted two experiments, one with hens and one with toms, using Large White turkeys.
In the first experiment, a control diet or the control plus 44 ppm of penicillin-streptomycin (1:3) or the control plus 44 ppm of Zn-bacitracin all with or without a preparation of dried Bacillus subtilis were fed to hens to 16 week of age.
In the second experiment, a control diet or the control plus 44 ppm of Zn-bacitracin or 2.2 ppm of bambermycin all with or without a preparation of dried Bacillus subtilis were fed to toms to 20 weeks of age. There was no effect of the microbial treatment in the first experiment on body weight or feed conversion or on body weight in the second.
However, in the second experiment, toms fed the microbial preparation had significantly improved feed conversion at 20 weeks compared too control fed birds (3.58 versus 3.67). Blair et al. (2004) fed Calsporin®, which contains Bacillus subtilis in spore form (C-3102), bacitracin (50g/ton), or an unmedicated control to Large White turkey toms to 18 weeks of age. Both the Bacillus subtilis and the bacitracin treatment resulted in heavier turkeys compared to the control (14.32 & 14.15 versus 13.41 kg). There were no differences in feed to gain (mean=2.41 + 0.05) or carcass or parts yield due to treatment. However, litter samples from the pens where the Bacillus subtilis was fed had less ammonia volatilization than samples from pens receiving the control diet (7.80 + 4.87 versus 25.2 + 8.47 ppm). All of these studies had very similar results to the study reported here in that, while toms fed DFM were not different in 20-week body weight, they did have improved feed conversion throughout the trial compared to control fed birds. In addition, the work reported by Potter et al. (1979) could be argued to be a positive study for DFM usage rather than a negative one due to possible contamination of the control fed birds by the live culture fed to the treated birds. For example, England et al. (1996) reportedly observed, during a previous feeding study, contamination of control birds from across an isle by L. reuteri being fed to treated birds. In the subsequent published work, England et al. (1996) took unusual measures to prevent the contamination of the control birds. These observations and measures are supported by observations and efforts made by Tortuero (1973), Watkins and Miller (1983a), Watkins and Miller (1983b), and Fritts et al. (2000) using chicks.
Even in the current study measures were taken to contain the movement of the live cultures. For example, 18-inch partitions were placed around every pen to prevent the litter contact from pen to pen. In addition, all work was conducted with the control birds first. All work conducted with the treated birds was conducted with disposable boots worn by the workers and after all work was accomplished, the hall ways were washed.
However, we conclude that even with these efforts, the hens in trial 2 experienced the spread of live culture into the control pens evidenced by the "catching-up" of the control birds with the treatment birds in body weight and cumulative feed conversion. Therefore, even other works reporting no effect of feeding DFM must be viewed with caution unless the authors describe the measures taken, if any, to isolate or contain the live cultures.
There are few reports of field trials describing the effects of DFM under commercial conditions. All three field trials reported here resulted in advantages for the birds provided the DFM in the water beyond the advantages that they may have experienced by having the AGP provided in the feed. This work is supported by the results conveyed by Fritts et al. (2000) of field trials conducted by Calpis Corporation (Kanagawa, Japan). In these trials, both body weight and feed efficiency were improved by feeding Bacillus subtilis to broiler chickens. In addition, Casas et al. (1998) reported the results of 16 paired-house field trials involving 280,000 commercial turkeys in eastern North Carolina. They delivered Lactobacillus reuteri (BioGaia Biologics, Raleigh NC) in spray form post-hatch and then metered into the feed in the feed hopper during the brooding period. They found that the L. reuteri treated birds had 2.8% less mortality in 13 trials, a 2.1% increase in body weight in 12 trials, a 3.5% improvement in feed conversion in 13 trials, and a 9% increase in the number of Grade A carcasses; all statistically significant at p<0.05. In one flock, body weight was measured at transfer from the brooder house to the grow-out house. The treated toms weighed 4.2 lbs compared to the control toms, which weighed 3.8 lbs at 42 days of age. Torres-Rodriguez et al. (2005) fed a Lactobacillus-based culture (FM-B11, IVS/Wynco) along with whey permeate to turkeys under field conditions. Turkey poults were kept in wire panel pens and treated up to 2 weeks of age either by water or feed administration. They were banded and released to the flock at 26 or 28 days of age (Experiments 1 or 2). Body weight was increased by 15.5 and 17.5% in birds receiving the culture plus the whey, or the whey alone, at the end of the experiment. Birds given the culture product and the whey were up to 436 grams heavier than controls at market age in experiment 1.
Not every trial with direct fed microbials has resulted in improved turkey performance. For example, Casas et al. (1998) reported that L. reuteri administration to unstressed turkey poults had no effect. However, in poults stressed by cold temperature and hatchery services such as beak and toe trimming, L. reuteri treated poults experienced increased eight gain. The implication is that there may be many opportunities for producers to test direct fed microbial products in their production systems.
While the explanation of the mode of action of DFM is not within the scope of this paper, proposed mechanisms of pathogen reduction or inhibition include competition for nutrients, production of toxic conditions and compounds, competition for binding sites on the intestinal epithelium, stimulation of the immune system, and enhancement of the mucous layer that covers the intestinal surface (Fuller, 1989; Gibson and Fuller, 2000; Patterson and Burkholder, 2003; Rolfe, 2000; Smirnov et al., 2005).
The use of DFM supplements in poultry diets changes and stabilizes the microflora environment of the avian digestive tract (Jin et al., 1998; Knarreborg, et al., 2002; Patterson and Burkholder, 2003; Smirnov et al., 2005). There are numerous reports describing competitive exclusion including the significant reduction of intestinal levels of Salmonella spp in turkeys or other livestock by use of DFM (Bailey, 1987; Casas et al. 1998; Juven et al., 1991; Nurmi and Rantala, 1973; Vicente et al., 2005). In addition to colonizing the intestinal tract, the use of L. reuteri resulted in shorter, lighter intestines and smaller relative intestinal weight in turkeys; similar results have been observed and reported in other studies with broilers (England et al., 1996).
Further research is needed to completely understand the effect of DFM on avian intestinal physiology and health. Further research is also needed to better understand the compatibility of DFM with other feed additives including commonly used AGP. In addition, further efforts are needed to extend the wide base of research knowledge to commercial use with respect to DFM. With the development and demonstration of DFM that survive feed processing and pelleting, additional testing of DFM under field conditions is warranted.
References are available on request
From Proceedings of the "Midwest Poultry Federation Convention", St. Paul, Minnesota, U.S.A.
