Stabilization of Poultry Processing By-Products and Waste and Poultry Carcasses Through Lactic Acid Fermentation1

01994Applied Poultry Science. Inc

STABILIZATION OF POULTRY PROCESSING BY-PRODUCTS AND WASTE AND POULTRY CARCASSES THROUGH LACTIC ACID FERMENTATION'

Primary Audience: Poultry Producers, Flock Supervisors, Rendering Managers, Processing Managers

MMARY Laboratory and field experiments were conducted to evaluate lactic acid fer th industrial carbohydrate by-products as fermentation subs r processing offal, blood, and dissolved air flotationwastewater carcasses. Additions of 15% brewer's solubles, 15% dry mol molasses, 6% cane sugar,6%whey product, or higher proportion ge (pHS4.2) at 30°C or 37°C o 15% or less putrefied. Reduced te a commercial silage culture of lactic acid rmentation. Offal mixed with DAF sludge at 12% and 24% was alone. Fermentation with 15% brewer's solubles was the d for preserving both poultry processing by-products and waste for subsequent nutrient recovery. cts, carcasses, fermentation, lactic a 1994J. Appl. Poul

A portion of this paper was presented at the 1992 Food Industry Environmental Conference, Georgia Tech Research Institute, Atlanta, GA. 2 Present address: Division of Environmental Analysis, Senator William X. Wall Experiment Station, Massachusetts Department of Environmental Protection, 37 Shattuck Street, Lawrence, MA 01843. 3 To whom correspondence should be addressed 1

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TIANDE CAI and OSCAR C. PANCORB02 Department of Food Science and Technology, University of Georgia, Athens, G A 30602 Phone: (706) 542-1001 FAX: (706) 542-7472 WILLIAM C. MERKA Department of Poultry Science, University of Georgia,Athens, G A 30602 JEAN E. SANDER Department of Avian Medicine, University of Georgia, Athens, G A 30602 HAROLD M.BARNHAR? Department of Food Science and Technology, University of Georgia, Athens, G A 30602

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FERMENTATION OF POULTRY WASTE

with 10-20% fermentable combined carbohyDESCRIPTION OF PROBLEM drates produced an acidic silage. In our previous studies on direct acidification of poultry offal and carcasses [12], putrefaction was prevented when silage pH was maintained below 4.5 and volatile nitrogen (NH3-N) content was less than 0.3%. The present study sought to evaluate lactic acid fermentation using inexpensive carbohydraterich industrial by-products as fermentation substrates and to establish a technically and economically feasible lactic fermentation process that would stabilize poultry offal, blood, DAF sludge, and poultry carcasses. Specific objectiveswere: 1) to determine industrial carbohydrate by-product fermentability and the minimum levels required to stabilize poultry carcass and offal silage, 2) to evaluate the effect of temperature on fermentation, 3) to test the feasibility of fermenting various poultry processing by-products and waste (offal, blood-offal mixture, and DAF sludge-offal mixtures) and poultry production wastes (broiler carcasses, dead male chicks, and hatchery waste), 4) to determine whether supplementation with a commercial silage culture was necessary, and 5 ) to demonstrate the economic feasibility of the optimal fermentation process.

MATERIALS AND METHODS CARBOHYDRATE SOURCES A N D SILAGE CULTURE Industrial carbohydrate-rich by-products tested for fermentability were liquid molasses, dry molasses, corn meal, non-delactosed dry wheys, and brewer’s solubles. Cane sugar was used as a carbohydrate control since it was a good fermentation substrate [4]. A commercial microbial silage culture used in this study contained Lactobacillus plantarum, Lactobacillus acidophiliis, Streptococcus faecium, Bacillus subtilk, and Aspergillus otyzae . FERMENTATIONPROCESS Laboratoty Experiments: Dead broilers (dead-on-arrival birds), offal, and DAF sludge were obtained from a local broiler processing plant. Dead male chicks and hatchery waste came from a local commercial hatchery farm. Broiler carcasses (axe-chopped before grinding), offal, chicks, and hatchery waste consisting of egg shells, non-fertile eggs, dead embryos, and deadkull chicks were separately

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Broiler processing plants produce large quantities of offal, feathers, blood, and dissolved air flotation (DAF) sludge. Most offal is shipped to rendering plants for processing into animal feed supplements. However, rapid putrefaction of offal requires immediate rendering of fresh offalto prevent odor problems. The hauling fee per ton of offal increases when less-than-truckload quantities of offal are transported. The utilization of offal becomes more difficult when high summer temperatures accelerate offal deterioration, which results in a poorer quality of poultry meal. Holding offal on weekends is most troul?!esome to manage since a typical rendering plant stops operations on weekends to maintain plant equipment. Thus, developing a technically feasible and economical method to stabilize poultry offal would benefit both poultry processing and rendering plants. The disposal of poultry carcasses also presents significant environmental, biological, and financial problems for the poultry industry. Currently, carcasses are disposed of by burial, incineration, rendering, composting, or landfilling [1,2]. Each of these processes, however, has its unique flaws. Burial of dead birds in a pit can lead to ground water contamination. Incineration is expensive and can potentially pollute the air. Rendering dead birds into by-product meal is constrained by transportation cost and restrictions on the movement of diseased birds from one location (e.g., a county) to another [l].Landfilling is subject to land availability and limitations on diseased carcass movement. Lactic acid fermentation offers potential hope for economically disposing of dead birds without contaminating the environment and may also provide an income from the recovery of nutrients since the fermented product (silage) is suitable for rendering [l]. In fact, fermentation of dead birds, poultry offal, and edible food wastes with lactic acid bacteria is very effective in inactivating pathogenic viruses and bacteria [3,4, 51. The ensiled products from poultry viscera [ 6 ] ,poultry offal [7], swine slaughter-house offal [8],and waste fish (9,101have been demonstrated to be useful for incorporation into swine and poultry diets. More recently, Murphy and Silbert [ l l ] reported that fermentation of broiler carcasses

Research Report CAI et al.

sive of the added water. The mixture was transferred by an auger to a truck tank, held and accumulated each day. When the tank was full, the silage was shipped to a plant in north Georgia for rendering, where samples were taken for quality analysis. DATA RECORDING AND ANALYSIS Ammonia nitrogen (volatile nitrogen) in samples was analyzed according to Section 417D of APHA Standard Methods [16]. Acidity (pH) wasmeasured with a CorningpH meter equipped with a flat surface combination probe electrode. Statistical methods of regression, general linear model, paired t test, and Duncan's multiple comparison procedures [ 171 analyzed the experimental data. Significance was defined as probability of 0.05 or less. All treatments and samples were run in duplicate, unless otherwise specified.

RESULTS AND DISCUSSION SUBSTRATE FERMENTABILITY AND CONCENTRATION Poultry carcasses and offal are deficient in carbohydrates necessary to support the growth of lactic acid bacteria. Therefore, inexpensive carbohydrate supplements were tested to evaluate pH reduction as a measure of fermentability at 37°C with the addition of 2% activated liquid silage culture. All pH values of carbohydrates (except corn meal) decreased from about 6.0 to 14.2 during the first two days of fermentation (Figure 1). Carcasses treated with cane sugar (100% sucrose), dry wheys (83% lactose for whey product and 72% lactose for sweet dry whey), liquid molasses (50% invert sugar), and dry molasses (38% invert sugar) had significantly greater pH reductions (P c .05). This finding indicates that sucrose, lactose, glucose, and fructose were more fermentable by indigenous microflora and the silage culture than the starch in corn meal. The addition of 6% liquid molasses (LM), 10% dry molasses (DM), 10% or 15% corn meal (CM), or 10% brewer's solubles (BS) did not produce adequate acids to stabilize the carcasses for eight days. Carcasses treated with corn meal yielded pH patterns different from those with other substrates during fermentation (Figure 1) because the starch in corn meal was not directly fermentable. It had to be broken down by the silage culture, particularly Aspergillus

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ground using an Enterprise meat grinder with a 12 mm sizing dice. The ground poultry waste was then mixed with a carbohydrate and incubated in a partially sealed plastic container at a specified temperature. Samples taken at various times during fermentation revealed pH measurement and ammonia nitrogen analysis. Silage culture inoculum (by weight of 0%, 0.01% dry powder, or 2% activated liquid culture) was added to carbohydrate-supplemented ground poultry waste in a 2.3 liter (0.5 gal) plastic container containing 1.5 kg of the final mixture. The activated liquid culture was prepared by inoculating 0.3% dry silage culture into 5% whey product solution in water. This mixture was incubated at 37°C for six to nine hr until lactic acid bacteria reached 108-109 CFU/ml. To ensure adequate mixing and to raise the final moisture of silage to 60-70% for lactic acid bacterial fermentation [l, 151, carbohydrate materials were diluted before use with reagent-grade ( m e I) water [16] in the following ratios (w/w): dry mo1asses:water = 1:2; corn meakwater = 1:2; dried whey:water = 1:2; cane sugar:water = 1:2; liquid mo1asses:water = 1:l; brewer's solub1es:water = 1:0-0.5. After mixing with the carbohydrate and silage culture, the ground carcass or offal was incubated at 21", 30", or 37°C for up to twenty-eight days, unless otherwise specified. Field Experiments: Poultry processing offal was obtained from a rendering plant in north Georgia. The offal was ground and mixed with 6% whey product or 15% brewer's solubles, and with or without 0.01% dry silage culture. The final mixture (about 40 kg) in a 57 liter (15 gal) covered plastic container was manually homogenized with a metal potato masher and stored at ambient temperatures for twenty-two days. Ammonia nitrogen and pH were monitored during fermentation. Fermentation of poultry carcasses in field trials was carried out on a poultry farm in north Georgia. Dead layer carcasses were received from the farm and ground with a 20" G.P.R. poultry grinder (Animal Health Sales, Inc., Selbyville, DE). About 1.5 kg of a 34% whey solution in water inoculated with 0.057% dry silage culture was added to every five birds (about 8 kg) during grinding. Therefore, the ground mixture contained approximately 6% dry whey and 0.01% dry silage culture exclu-

19

JAPR FERMENTATION O F POULTRY WASTE

20

I

n

n

10%

es

I

n

-*

4-

15% es 20% BS

3 Days

Days

FIGURE 1. Effectsof supplemental carbohydrate type and concentration on the p H of broiler carcasses during fermentationat 37°C: LM = liquid molasses, DM =dry molasses, CM = corn meal, WP = whey product, DW = dry sweet whey, CS= cane sugar, and BS= brewer's solubles.

oyzae and Bacillus subtilis, before sufficient acids could be produced. As a result, pH increased after the depletion of available sugars and decreased again after the starch began to break down. Carcasses fermented with 15% corn meal had approximately the same pH as with 20% corn meal on day 8, but the former became putrid on day 6, having high pH and NH3-N concentrations (Figures 1and 2). The pH (54.2) of carcasses fermented with 2 10% LM, 215% DM, 215% BS, 26% WP, 510% dry sweet whey (DW), or 2 6 % CS was significantly lower than the pH of other silage during storage for eight days (Figure 1). Regression analysis showed that the pH was highly correlated linearly with the square root

of tested substrate concentration (R2 > 0.91, P < .OOl) for each of the carbohydrate supplements. A projected minimum of 6% CS, 8% WP, 12% LM, 13% DM, 15% BS, or 24% CM should have produced a pH of 4.2 and 4.4 or less in carcasses ensiled for two and eight days, respectively. The minimum fermentable carbohydrate levels required to produce endpoint pH (14.2) are close to those reported previously [9], but lower than those reported by Murphy and Silbert [ll].The discrepancy may be attributed to the different ground carcass sizes. The larger the ground tissue size, the more acid is nccded to penetrate it; therefore, more fermentable carbohydrate is required as supplement.

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I

Research Report 21

CAI etal.

contained 0.32% 2 0.11% NH3-N (Table 1). These findings were similar to those of the laboratory silage produced from one-day-old carcasses fermented with 6% whey product for eight days (Table 2).

I

LM

DY

CY

WP

DW

CS

Ca rbohyd rats Source

Ammonia is an index of lactic acid fermentation because high values indicate high protein degradation. A successful lactic acid fermentation would result in low pH and low ammonia content. At least 10% LM, 13%DM, 20% CM, 6% W, 8% DW, or 6% CS was needed in the carcasses to achieve an NH3-N content of less than 0.3% (Figure 2). Ammonia nitrogen increased with pH and they were positively correlated linearly (R = 0.91, P < .Ol). Thus, pH to agreat extent can be used to evaluate silage quality and stability. Field studies on the fermentation of ground offal from three broiler processing plants at ambient temperatures of 6°C to 22°C showed that the addition of 6% whey product and 0.01% silage culture stabilized the offal for twenty-two days with an endpoint pH of 4.81 2 0.05 and an endpoint NH3-N concentration of 0.19% 2 0.01%. No statistically significant differences in pH and NH3-N content occurred among the offal from the different plants during fermentation for twenty-two days. Ammonia nitrogen concentration in offal was not significantly different before and after fermentation. The ground offal control (untreated offal) in this study putrefied during storage and had an NH3-N content of 0.7% at eight days. These results indicate that fermentation at low temperatures inhibited ammonia production. Fermentation of poultry carcasses at ambient temperatures on a 650,000 layer farm in north Georgia has been in operation since June of 1991. Carcasses fermented for five months from July to November showed that the carcass silage had a pH of 4.9 2 0.3 and

MONTH

BATCH#

pH

NH3-N(%)

July

1

4.9

0.21

August

2

5.4

0.48

September

3

4.8

0.36

October

4

4.9

0.26

November

5

Mean 2 Standard Deviation

4.6

0.28

4.920.3

0.3220.11

TABLE 2. p H of one-day-oldcarcassesfermentedfor eiaht d a w with carbohvdrate sumlement

670 WP

10% LM

15% BS

4.73a

0.40a

4.69a

0.3Sa

37

4.79a

-

30 21

4.61a 4.61a

-

37

4.21b

0.33a

30

4.2.1b

0.32a

21

4.5?

0.30a

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FIGURE 2. Ammonia nitrogen in broiler carcasses fermented for eight days at 37°C with liquid molasses (LM), dry molasses (DM), corn meal (CM), whey product (WP), dry sweet whey (DW), or cane sugar (CS).

FERMENTATION TEMPERATURE Temperature is an important factor influencing fermentation. Carcasses and offal fermented at 30°C and 37°C yielded acidic silage in the presence of sufficient carbohydrate (Figure 3). No differences (P > .60) in pH reduction occurred between 30°C and 37°C. A considerably higher pH of poultry offal at 21°C than 30°C and 37°C was observed when the offal was fermented for eight days with 6% WP, 10% WP, 10% LM, or 15% BS because of slow

JAPR FERMENTATION OF POULTRY WASTE

22

-

5 4

3 37 3 o z i

373021

~ 7 ~ 0 2371 3021

3730

T e m p e r a t u r e (OC) FIGURE 3. Effect of temperature on pH of broiler offal (A) and carcasses (8)fermented for eight days with whey product (WP), liquid molasses (LM), or brewer's solubles (BS).

fermentation at the lower temperature (Figure 3A). The opposite occurred when the substrate concentration was low ( i e . ,6% LM), presumably because the depletion of fermentable carbohydrate stopped the production of acid at the higher temperatures (Figure 3A). Similar results appeared in fermented carcasses with 10% BS and 15% BS (Figure 3B). A fermentation temperature of 21°C produced a lower pH with 10% BS, but yielded a higher pH with 15% BS than at 30°C and 37°C at eight days. Thus, an interaction between substrate concentration and temperature occurred. Whenever there was adequate carbohydrate available for fermentation of poultry offal and carcasses, a higher pH would be observed at 21°C than at 30°C or 37°C. POULTRY PROCESSING AND PRODUCTION WASTE Fermented broiler offal, carcasses, and male chicks had a pH of 4.3 or less when stored for eight days at 37°C (Figure 4A). However, the pH of fermented hatchery waste was significantly (P c .OS) higher, resulting in putrefaction of the material after four days. The poor quality of the raw material before incu-

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A I4akh.r). W a s h

A Doad Yale Chicks

-L

0 BmilwOffal

5.0

n 4.0

3.5

'

2

0

6

4

I

IO

8

I

P

0

2

4

6

8

IO

12

14

16

Days of F e r m e n t a t i o n FIGURE 4. pH of poultry waste materialsfermented at 37%: (A) with 15% brewer's solubles; (8)mixtures of DAF sludge, brewer's soluble, and offal; 10SLGIOBS80FL = 10% OAF sludge, 10% brewer's solubles, and 80% offal; 15BS85FL = 15% brewer's solubles and 85% offal; etc. (wet weight basis).

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I a

37 30 21 37 30 21 37 30 21 37 30 21 37 30 21

bation and the high buffering capacity of egg yolk and egg shell (calcium) accounted for the unsuccessful fermentation of this waste. Thus, proper fermentation of poultry waste requires the material to be fresh and have a low buffering capacity. Studies of broiler carcass freshness also revealed that it was more difficult to stabilize one-day-old carcasses than fresh carcasses. A substrate concentration of 10% liquid molasses or 6% whey product added to one-day-old carcasses might not produce sufficient acids to stabilize the carcasses for more than eight days, as the carcass pH was unstable and increased to 4.8 during storage for eight days (Table 2). Therefore, old carcasses may need a higher concentration of fermentable carbohydrate to have a satisfactory lactic acid fermentation for preservation. Spoiled poultry materials, however, cannot be stabilized by fermentation. Offal silage had a higher acidity than carcass (broiler or chick) silage (Figure 4A). A similar phenomenon was observed (Figure 3) based on the same substrate treatment (e.g., 6% WP and 10% LM), since offal (viscera, heads, and feet) contains more car-

Research Report CAI et al.

SUPPLEMENTAL SILAGE CULTURE Fermentation with a commercial silage culture inoculum (2% liquid culture or 0.01% dry powder) was not significantly different from that without inoculation (Figure 5). Some differences in pH observed at the later stage

of fermentation probably stemmed from mold growth resulting from repeated opening of the container for pH measurements.These results indicate that the level of indigenous lactic acid bacteria in poultry offal and carcasses was adequate to ferment carbohydrates, also leading to the rapid production of acid to prevent putrefaction. A field study of the fermentation of broiler processing offal for eight days at ambient temperatures of k16"C at the rendering plant also showed no significant differences in acidity and ammonia content between offal silages with and without silage culture inoculation. Both offal silages had a pH of 5.0 and NH3-N concentrations of 0.30%-0.34%. We can conclude that adequate lactic acid bacteria are naturally present in poultry offal and carcasses and that supplementation of commercial lactic acid bacteria is unnecessary for effective fermentation of these materials.

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bohydrate than the whole carcass on a weight basis. Thus, carcasses should require more supplemental carbohydrate than offal for successful comparable fermentation. DAF sludge added to offal did not have a significant effect on pH at sludge concentrations of O%, 10% and 20% when fermented for fourteen days (Figure 4B). The difference in sludge-offal pH resulted from the influence of brewer's solubles (BS) concentration rather than from the effect of sludge concentration. Offal or sludge-offal ensiled with 15% BS had a more stable pH than that with 10% BS. All 15% BS-based offal and sludge-offal mixtures had a pH close to 4.0 after storage from one to fourteen days (Figure 4B).

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ECONOMIC FEASIBILITY Fermentationwith 15% brewer's solubles (BS, which contained 50-52% solids) was the most inexpensive of the effective carbohydrate 6.0 I 1 sources and concentrations tested (Table 3). The cost of this substrate was $8.3/1,000 kg silage (based on 1992 cost estimate). In addition, fermentation of broiler offal, fresh carcasses, and one-day-old carcasses confirmed that 15% BS silage produced lower pH than the 6% whey product (WP) or 10% liquid 3.5 L A molasses (LM) silage (Table 2). Although the 6.0 i cost of 10% LM was approximately the same 5.5t Offa' as for 15% BS (Table 3), offal and carcasses ensiled with the latter were more stable during storage for twenty-eight days. The endpoint pH of 15% BS based silage was 4.3, whereas the pH of 10% LM silage was 5.2. Moreover, the addition of 15% BS to ground broiler car3.5 I . 1 , . casses, offal, or DAF sludge-offal mixture I---------(1:3.3 by wet weight) stabilized silage pH ( ~ 4 . 5 for ) sixty days. A typical poultry farm with 650,000 birds spends thousands of dollars annually on transportation costs and fees for landfilling dead birds. When lactic acid fermentation stabilizes the carcasses, the annual cost including overhead and materials will cost approximately $4,400 for fermentation with 6% whey product Days of Fermentation or $3,090 for fermentation with 15% brewer's solubles (Table 4). If the fermented carcasses FIGURE 5. Effect of silage culture supplementon the p H of broiler carcasses, offal, and DAF sludge-offal are saleable, the farm can realize a financial mixture (1:3.3 by wet weight) fermented with 15% return on the fermentation investment, bebrewer's solubles at 30°C. I

JAPR FERMENTATION OF POULTRY WASTE

24 TABLE 3. Cost estimates of carbohydrate supplements

Whey product

Brewers solubles

Grinder, auger

$1750/yr

$175O/yr

Facilities, supplies

$ 400&

$400/yr

Whey product (6%)

$2250/yr

-

-

$ 94Otvr

Brewers solubles (15%) Annual cost

w00/yr

Carcass silage sales ($0.02/lb) Possible net return

I

I

$309O/yr

S5600/yr

$5rn/yr

$1200/vr

SZlO/vr

cause renderers may pay $0.02-0.03/lb [l]. Therefore, unlike other disposal methods, fermentation of carcasses could not only save

dollars/provide economicbenefit for the poultry farm but also reduce environmental contamination significantly.

CONCLUSIONS AND APPLICATIONS 1. Effective stabilization of chicken processing offal, blood-offal and DAF sludge-offal mix-

tures, and chicken carcasses can be achieved by lactic acid fermentation supplementedwith cane sugar, dried whey, molasses, and brewer’s solubles. The minimum concentration of substrate used to stabilize chicken offal or carcasses for eight days was 6% for cane sugar, 6% for dried whey, 10% for liquid molasses, and 15% for brewer’s solubles. Higher levels may be needed for longer stabilization of coarsely-ground older carcasses or offal. 2. Corn meal was a poor fermentation substrate. Carcasses ensiled with 10-15% corn meal putrefied after storage for four to six days at 37°C.

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Based on sale in bu

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REFERENCES AND NOTES 1.Dobbins, C.N., J.r., 1990. Dead birddisposal through the use of Iactobaclllus fermentation (ensilage). Presented at the Southeastern Poultry and Egg h o c . Conf., Atlanta, GA. 2. Murphy, D.W. andT.S. Handwerker, 1988. Preliminary investigations of composting as a method of dead bird disposal. Pages 65-72 in: Proc. 1st National Poultry Waste Management Symp., Ohio State Univ., Columbus,

OH.

m

3. Dobbins, C.N., Jr., 1988. fermen tation: A method of disposal/utilization of carcasses contaminated by pathogenic organisms or toxic chemicals. Pages 76-80 in: Proc. 1st National Poultry Waste Management Symp., Ohio State Univ., Columbus, OH. 4. Pancorbo, O.C., W.C. Merka, S.M. Russell, D.L Fletcher, and R.W. Baslien, 1990. Destruction of bacterial pathogens and indicators in broiler processing waste (offal) during lactic acid fermentation. Pa es 104-112 in: Food Ind. Environ. Conf., Georgia Tech kesearch Institute, Atlanta, GA.

5. Sholls, EB. Jr., R . E Wooley, and J.A. Dickens, 1984. Anti-microbiceffects o-f fermentation on edible waste material contaminated with infected carcasses. Am. J. Vet. Res. 452467-2470. 6. Tlbbells, C.W. and RW. Seerley, Poultry . . 1988. viscera ensiledwith for owing and finishing s w i n e f 8 8 S 9 1 3 . 7. Tibbells, G.W., R.W. Seerley, a n d H.C. McCampbell, 1987.Poultry offal ensiled with Lactobarillusi.ld@h’ for growing and finishing swine diets. J. Animal Sci. 64:182-190. 8. Szakacs, C., J. Cyory, and L Slankovin, 1985. Presexvation of autoclaved slaujhter-house by-product. Pages 1 6 2 1 in: Agric. Waste tilization and Management, Proc. 5th International S p p . on Agric. Wastes, American Society of Agric. Engineers, St. Joseph, MI. 9. Hassan, T.E. and J.L. Heath, 1986. Biological fermentation of fish waste for potential use in animal and poultry feeds. Agric. Wastes. 191-15.

10. Tibbells, C.W., R.W. Seerley, H.C. McCampbell, and SA.Vezey, 1981. An evaluation of an ensiled waste fish product in swine diets. J. Animal Sci. 52:93-100. 11.Murphy, D.W. and S.A. Silbert, 1992. Presewation of and nutrient recovery from poultry carcasses subject to lactic acid bacteria fermentation. J. Appl. Poultry Res. 156-74.

12. Cai, T., 1993. Stabilization of Poultry Processing Wastes and Poultry Carcasses through Direct Chemical Acidification and Lactic Acid Fermentation. Doctoral Dissertation, University of Georgia, Athens, GA. 13. McCullough, M E , 1978. Silage: Some general considerations. Pages 3-25 in: Fermentation of Silage: A Review. M.E. McCullough, ed. NFIA, West Des Moines, IA. 14. APHA, 1985. Standard Methods for the Ekamination of Water and Wastewater. 16th ed. American Public Health Assoc., Washington, DC.

15. SAS Instilute, 1988. SASiSTAT User’s Guide: Release 6.03 Edition. SAS Institute Inc., Cary, NC.

ACKNOWLEDGEMENTS Financial sup ort for this study by Georgia Proteins, Inc., Cummin &A (Grant No. 25-21-RC294-113to the University of h , , a Research Foundation) is gratefully acknowledged. Liquid molasses (Blackstrap), dry molasses (Sweetlix 38),non-delactosed dry wheys (Whey Product and Sweet Dry Whey), and brewer’s solubles (Brewex) were obtained from Savannah Food and Industries (Savannah, GA), PM ag Product (San Francisco, CA), Land O’Lakes (Minnea olis, MN), and Anheuser-Busch (Williamsburg, VA?, respectively. The microbial silage culture used (SII-All in freezedried powder form) was provided by Alltech, Inc., Nicholasville, KY.

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3. Fermentation of offal and carcasses was slower at 21°C than at 30°C and 37°C. Adding adequate fermentable carbohydrate produced a more stable silage at 30-37°C. 4. Stabilization of poultry carcasses required more supplemental carbohydrate than stabilization of poultry offal. 5. Indigenous lactic acid bacteria in chicken offal and carcasses fermented carbohydrates equally well with or without the supplementation of a commercial microbial silage culture. Thus, the addition of silage culture can be eliminated to reduce the cost of fermentation of these poultry wastes. 6. The addition of 15% brewer’s solubles to ground chicken offal, DAF sludge-offal mixtures, and chicken carcasses produced stable, acidic silage (pH < 4.5) for sixty days. This process seems to be the most economical and technically sound stabilization method to use on a large scale to preserve these materials for subsequent nutrient recovery. 7. Carcass silage production on a poultry farm proved that lactic acid fermentation to stabilize carcasses was technically and economically feasible if a renderer could provide a truck tank. Lower fermentation cost and higher silage quality would be expected if 15% brewer’s solubles was used as the supplement on the farm. Fermentation of carcasses may provide additional income for farms since the product was suitable for rendering. Furthermore, ensiled carcasses were reused and would not contaminate the environment like other carcass disposal methods.