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ELSEVIER PI1:S0960-8524(98)00043-1 Bioresource Technology 66 (1998) 13-18 © 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0960-8524/98 $19.00 EFFECT OF PROCESSING METHOD ON RUMINAL SOLUBILITY AND DEGRADABILITY OF BROILER LITTER Wansup Kwakfl Joseph P. Fontenot b* & Joseph H. Herbein b "Department of Animal Science, Kon-Kuk University, Chung-Ju, Chung-Buk, Korea ;'Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA (Received 30 June 1997; revised version received 2 March 1998; accepted 3 March 1998) Abstract Ruminal crude protein (CP) degradability and solubility of ensiled, deepstacked, and composted broiler litter were determined in situ and in vitro, and compared to soybean meal. The estimated ruminal degradability of CP was 75"2% for soybean meal and 89-94% for broiler litter. Ruminal degradability of dry matter (DM) of broiler litter processed by different methods was 66-69%, and that of soybean meal was 77"9%. Degradability of DM of deepstacked litter from private farms was lower (P < 0"05) in the surface and charred areas, compared with normal brown, properly preserved litter within the stack. Results indicate that nutritional value of broiler litter for ruminants is affected by soluble and degradable DM and CP. The nutritional value may be reduced by improper storage. © 1998 Elsevier Science Ltd. All rights reserved Key words: poultry, broiler litter, solubility, degra- dability, ruminal. INTRODUCTION Animal wastes have been used as sources of plant nutrients since before the introduction of inorganic fertilizers. During the past 40 y research results have shown that the wastes can be utilized as sources of nutrients for feeding animals (Fontenot, 1991). Broiler litter is more valuable for use as animal feed than the other animal wastes (Fontenot & Ross, 1980). Animal wastes must be processed for use as feed to destroy pathogens, improve storage and handling characteristics, and maintain or enhance palatability (CAST, 1978). Broiler litter used for feed is processed and stored primarily by deepstacking, but it may be processed by ensiling and composting. In broiler litter, approximately 50% of the nitrogen (N) is in a non-protein form (Bhattacharya *Author to whom correspondence should be addressed. & Fontenot, 1965). High acid detergent insoluble N content (Van Soest & Robertson, 1976) indicates that some litter N may be unavailable for microbial or enzymatic breakdown in the digestive tract of ruminants. Method of preservation of poultry litter may alter solubility and degradability of litter DM and CP in the rumen, but in situ or in vitro informa- tion is not available to describe these characteristics of processed broiler litter. Excess heat generated during deepstacking frequently causes charring, which also may alter nutritional characteristics. This study was conducted to estimate the solubility and degradability of protein (nitrogen) and dry matter fractions in the rumen of ensiled, composted, and deepstacked (surface, charred, and normal) broiler litter. 13 METHODS In situ Experiment 1 Broiler litter, collected fresh from a broiler house, was transported approximately 350 kin. Processing methods were ensiling, deepstacking, and composting. Wood shavings had been used as bedding. The ash content of the litter was 29%, DM basis (Abdelmawla et al., 1988). For ensiling, water was added to the litter to achieve 40% moisture, and the litter was ensiled in 200-1 metal drums double lined with polyethylene bags and sealed as described by Caswell et al. (1977). Litter was deepstacked or composted in wooden cells with depth of 1"5 m, length of 1"2m, and width of 1"2m in a covered shed open on all sides. Composted litter was aerated once daily during the first week of the processing period, every other day during the second week, and weekly for the next 4 weeks. Deepstacked litter was not disturbed during the 6-week processing period. A replicated in situ experiment was conducted with two mature Holstein cows fitted with ruminal cannula to determine ruminal degradability of soybean meal (SBM), ensiled (EBL), deepstacked

Effect of processing method on ruminal solubility and degradability of broiler litter

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ELSEVIER P I 1 : S 0 9 6 0 - 8 5 2 4 ( 9 8 ) 0 0 0 4 3 - 1

Bioresource Technology 66 (1998) 13-18 © 1998 Elsevier Science Ltd. All rights reserved

Printed in Great Britain 0960-8524/98 $19.00

EFFECT OF PROCESSING M E T H O D ON R U M I N A L SOLUBILITY A N D D E G R A D A B I L I T Y OF BROILER LITTER

Wansup Kwakfl Joseph P. Fontenot b* & Joseph H. Herbein b

"Department of Animal Science, Kon-Kuk University, Chung-Ju, Chung-Buk, Korea ;'Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA

(Received 30 June 1997; revised version received 2 March 1998; accepted 3 March 1998)

Abstract Ruminal crude protein (CP) degradability and solubility of ensiled, deepstacked, and composted broiler litter were determined in situ and in vitro, and compared to soybean meal. The estimated ruminal degradability of CP was 75"2% for soybean meal and 89-94% for broiler litter. Ruminal degradability of dry matter (DM) of broiler litter processed by different methods was 66-69%, and that o f soybean meal was 77"9%. Degradability of DM of deepstacked litter from private farms was lower (P < 0"05) in the surface and charred areas, compared with normal brown, properly preserved litter within the stack. Results indicate that nutritional value o f broiler litter for ruminants is affected by soluble and degradable DM and CP. The nutritional value may be reduced by improper storage. © 1998 Elsevier Science Ltd. All rights reserved

Key words: poultry, broiler litter, solubility, degra- dability, ruminal.

INTRODUCTION

Animal wastes have been used as sources of plant nutrients since before the introduction of inorganic fertilizers. During the past 40 y research results have shown that the wastes can be utilized as sources of nutrients for feeding animals (Fontenot, 1991). Broiler litter is more valuable for use as animal feed than the other animal wastes (Fontenot & Ross, 1980). Animal wastes must be processed for use as feed to destroy pathogens, improve storage and handling characteristics, and maintain or enhance palatability (CAST, 1978). Broiler litter used for feed is processed and stored primarily by deepstacking, but it may be processed by ensiling and composting.

In broiler litter, approximately 50% of the nitrogen (N) is in a non-protein form (Bhattacharya

*Author to whom correspondence should be addressed.

& Fontenot, 1965). High acid detergent insoluble N content (Van Soest & Robertson, 1976) indicates that some litter N may be unavailable for microbial or enzymatic breakdown in the digestive tract of ruminants. Method of preservation of poultry litter may alter solubility and degradability of litter DM and CP in the rumen, but in situ or in vitro informa- tion is not available to describe these characteristics of processed broiler litter. Excess heat generated during deepstacking frequently causes charring, which also may alter nutritional characteristics. This study was conducted to estimate the solubility and degradability of protein (nitrogen) and dry matter fractions in the rumen of ensiled, composted, and deepstacked (surface, charred, and normal) broiler litter.

13

METHODS

In situ Experiment 1 Broiler litter, collected fresh from a broiler house, was transported approximately 350 kin. Processing methods were ensiling, deepstacking, and composting. Wood shavings had been used as bedding. The ash content of the litter was 29%, DM basis (Abdelmawla et al., 1988). For ensiling, water was added to the litter to achieve 40% moisture, and the litter was ensiled in 200-1 metal drums double lined with polyethylene bags and sealed as described by Caswell et al. (1977). Litter was deepstacked or composted in wooden cells with depth of 1"5 m, length of 1"2m, and width of 1"2m in a covered shed open on all sides. Composted litter was aerated once daily during the first week of the processing period, every other day during the second week, and weekly for the next 4 weeks. Deepstacked litter was not disturbed during the 6-week processing period.

A replicated in situ experiment was conducted with two mature Holstein cows fitted with ruminal cannula to determine ruminal degradability of soybean meal (SBM), ensiled (EBL), deepstacked

14 W. Kwak et al.

(DBL), and composted (CBL) broiler litter. Soybean meal was used as positive control, since it is the most widely used protein supplement for animal feeding. Cows were fed a barley silage-based total mixed diet (14-2% CP and 75-2% TDN, DM basis) for at least 2 weeks before each in situ trial. Cows were fed at 0200 and 1400 daily on an ad libitum basis.

The in situ dacron bag technique was that of Nocek (1985). Polyester dacron bags were 10 × 23 cm and 5 9 + 2 pm porosity. Samples (approximately 10g) were weighed into duplicate bags and placed in the rumen. The ratio of sample size to bag surface area was approximately 26mg/cm 2, wet basis. Ruminal incubation times were 0, 1, 2, 4, 8, 12, 24, and 48h. Bags were submerged into the liquid layer in the ventral sac of the rumen. After removal, bags were rinsed in a continuous flow of tap water for approximately 24 h, then dried at 60°C for 48 h. Duplicate samples were composited at each incubation time per animal for each replicate. Nitrogen was analyzed by the Kjeldahl procedure (AOAC, 1985).

Ruminal degradation of DM and CP was classi- fied into three fractions, using a direct procedure. Fraction A was the soluble fraction, and fraction B represented the insoluble, but degradable fraction. The original sample weight without a 24-h tap water rinse was equal to the sum of fractions A, B, and C, whereas, the 0-h sample weight after a 24-h rinse equaled the sum of fractions B plus C. The rinsed residue after 48 h of incubation was considered the undegradable C fraction. Residues at each incuba- tion time minus the C fraction were converted to a percentage, transformed to the natural logarithm, and subjected to linear regression (Armentano et al., 1986). Slope of the regression line was degradation rate of fraction B (K~B). Computed degradation rates were used to predict ruminal degradability of DM and CP in SBM, EBL, DBL, and CBL, using the following equation (Orskov et al., 1983), and assumed passage rates (KpB) of 0.025 or 0"05/h (Miller, 1982):

Degradability = A + (KdB x B)/(KdB + KpB)

Disappearance percentage of DM and CP at any given time was calculated (Orskov et al., 1983) as follows:

Disappearance = A + B(1 - e k,)

where A = s o l u b l e A fraction, B = degradable B fraction, e = exponent, k = degradation rate of degradable B fraction, and t = time.

Statistical analysis was by analysis of variance using a model that included trial, cow, and feed. Least squares means were compared by orthogonal contrasts (SAS, 1982). Contrasts were SBM versus broiler litter (BL), EBL versus DBL and CBL, and DBL versus CBL.

In vitro experiment Solubilities of CP in SBM, EBL, DBL, and CBL were determined in autoclaved ruminal fluid according to the method of Wohlt et al. (1973). Ruminal fluid was collected from a ruminally cannu- lated mature Holstein steer fed chopped alfalfa hay. The fluid was filtered through four layers of cheese- cloth, autoclaved at 121°C for 45 min, and centri- fuged at 1500g for 5 min to obtain the solvent. The solvent was adjusted to pH 6.1 with ortho (85%) H3PO4 and 2 N NaOH.

Wet feed samples (equivalent to 250 mg of DM) were weighed into 1-1 flasks and filled with solvent to 1 1. Flasks were incubated at 40°C for 2 h while mechanically agitated at a mild rate in a water bath. Approximately 125-ml duplicate samples were removed and centrifuged at 1500g for 5 min. An aliquot of supernatant (approximated 10 g) was used for determination of soluble CP by the Kjeldahl procedure (AOAC, 1985).

In situ Experiment 2 To determine ruminal degradability of DM and CP of surface, normal, and charred deepstacked broiler litter, a duplicated in situ experiment was conducted with a ruminally cannulated Holstein steer. The in situ procedures and calculations were similar to those for Experiment 1. Samples of DBL were collected from two private broiler farms. At Farm 1, litter was stored inside a building for 2 months in a stack 2.4 m deep, 11.3 m wide, and 15.8 m long. At Farm 2, litter was stored outside, thus exposed to the weather for 8 months in a stack, 1.8 m deep, 3.7 m wide, and 14.6 m long. Surface samples were taken 5 - 1 5 c m from the top of the deepstacks, regardless of the depth. The normal and charred samples were obtained from the center of the stacks.

Statistical analysis for DM and CP percentage was by analysis of variance using a model that included farm, sample, and farm x sample interaction. The interaction was not significant and removed from the model. In situ fractions KdB, and degradability of litter DM and CP were analyzed for each farm, according to a model that included trial and sample. Means were compared by Tukey's studentized Range Test (SAS, 1982), and differences were considered significant for P < 0.05.

RESULTS AND DISCUSSION

In situ Experiment 1 Soluble DM in BL was approximately twice (P<0-05) that in SBM (Table 1). The degradable fraction of litter DM was approximately one-third that of SBM. Within BL, CBL contained less (P<0"05) soluble and more (P<0.05) degradable DM than DBL. Degradable DM was highest (P<0.05) for EBL, compared with DBL and CBL,

Ruminal solubility and degradability o f broiler litter

Table 1. In situ fractions and rates of degradation of dry matter and crude protein a

15

Item Soybean meal Processed broiler litter

Ensiled Deepstacked Composted

SE

Dry m a t t e r (%)b.c,d 90"0 59"4 76'0 83"5 1"2 Dry matter

Fractions (%) Soluble A h'c'd 32-4 51 "0 59-9 50"5 1"4 Degradable B b'c'd 66-1 28-4 16"2 24"7 1"4 Undegradable C b'c 1-5 20-6 23.9 24.8 0"3

KdB e (%/h) I''c 12"6 6"0 7"1 9"1 0"6

Crude protein (%)b.c.d 48"8 34"9 29'5 25"9 1'6 Crude protein

Fractions (%) Soluble A ~'c'd 22.3 88.4 86-0 80.4 1"3 Degradable B b'd 77"4 8"7 8-4 13-3 1-3 Undegradable C bc'd '3 3-0 5.6 6.4 0-1

KdB c (%/h) b 12'2 7-2 8.0 8'8 1-0

aMeans for replicated in situ determinations for two cows. bSoybean meal differs from litters (P < 0.01). CEnsiled differs from deepstacked and composted litters (P < 0-05). dDeepstacked differs from composted litter (P<0"01). ~Degradation rate of degradable B fraction.

but the undegradable fraction of EBL was lowest (P<0"01). In addition, EBL had a lower (P<0.01) degradation rate of fraction B (KaB) than DBL and CBL. Overall, however, processing methods influ- enced in situ DM characteristics of broiler litter only to a limited extent.

Soluble A, degradable B, and undegradable C fractions of SBM CP (Table 1), were similar to values obtained by Zerbini and Polan (1985). Soluble fractions of CP in BL were 80-88%; whereas, degradable fractions were 8-13%, and undegradable fractions were 3-6%. The highly soluble CP fractions in BL may be attributed to high NPN content (Bhattacharya & Fontenot, 1965). Erdman et al. (1987) reported that potentially degradable N, which was soluble plus degradable N, was 90% or greater for most feedstuffs. In the present study, approximately 93-97% of N in BL was apparently available for digestion in the rumen, but most of the N was in the soluble fraction.

The undegradable CP fraction in BL was more than 10 times that of SBM. With respect to processing methods, EBL had the highest (P<0-05) soluble fraction and the lowest (P<0"05) undegrad- able fraction, possibly due to a microbial degrada- tion of some of the litter protein during ensiling. Composting showed trends opposite to ensiling, possibly due to NH3 volatilization during composting and heat damage of N. In a previous study, higher temperatures were recorded from composting than ensiling or deepstacking (Abdelmawla, 1990).

Rates of degradation of the degradable B fraction of CP in SBM were similar to those for DM. Zerbini and Polan (1985) observed a KaB of 10"3%/h for SBM CP, compared with 12"2%/h in this study.

Degradable CP (KdB) in BL was more slowly degraded (P<0"01) than that of SBM, but no differ- ences among BL were detected. Rate of CP disappearance after 12 h might reflect the degrada- tion of more resistant protein (Miller, 1982). Loerch et al. (1983) suggested that in situ CP disappearance at 12 h of incubation had the highest correlation with CP escaping ruminal fermentation in vivo. In the present study, CP disappearances at 12 h were 80"4% for SBM and 89-94% for BL. Our observed disappearance of CP in SBM at 12 h was somewhat higher than 65-69% reported by Loerch et al. (1983) and Stern et al. (1985).

The amount of potentially degradable DM or CP in a feedstuff actually degraded in the rumen varies with rate of passage of undigested residue (KpB). Predicted DM degradability was 86.4% for SBM and approximately 70-71% for BL when KpB = 0-025/h, and 77"9% for SBM and approximately 66-69% for BL when KpB = 0"05/h (Table 2). Regardless of passage rate selected, DM degradability was lower (P<0-0001) for BL than SBM, primarily due to the higher undegradable fraction C in BL. With respect to processing methods, composting lowered (P < 0"005) DM degradability compared to deepstacking.

In contrast to degradability of DM, that of CP was higher (P < 0-0001) for BL than for SBM at both passage rates, due to the very high soluble fraction in BL. Orskov et al. (1983) proposed that passage rate would affect degradability to a greater extent as the KaB of the degradable fraction decreases. However, in the present study degradability of CP in BL was not affected by passage rate, perhaps due to the extremely low quantity in the degradable

16 W. Kwak et al.

Table 2. In situ total dry matter and crude protein degradability at two rates of passage a

Item Soybean meal Processed broiler litter

Ensiled Deepstacked Composted

SE

Dry ma t t e r degradabi l i ty at KpB a 0.025 b,d 0.05 b,d

Crude prote in degradabi l i ty at KpB a 0.025 b,c 0.05b, c

86"4 71-2 71.4 69.5 0.3 77-9 66.7 68.6 66-0 0.4

85.3 95-2 92.3 90.8 0"5 75-2 94.2 91.0 89.0 0-7

aRates of passage (KpB) were assumed to be 0.025 and 0"05/h. bSoybean meal differs from litters (P< 0'0001). "Ensiled differs from deepstacked and composted litters (P < 0.005). dDeepstacked differs from composted litter (P< 0"005).

fraction. Among BL, EBL had the highest (P<0-005) CP degradability. In general, predicted CP degradability of BL apparently was influenced primarily by the quantity of CP in the soluble fraction.

Under practical feeding, BL has been used as feed primarily for ruminants at low to medium production, such as stocker cattle, and gestating and lactating beef cows (Ruffin & McCaskey, 1990). Litter characteristics of high soluble N fraction and degradability and low DM degradability, observed in the present study, appear to be suitable for these animals. Among processing methods, deepstacking and ensiling are practical and economical (Fontenot, 1991).

In vitro experiment The solubility of CP in autoclaved ruminal fluid was 12-3% for SBM, 61"5% for EBL, 58.9% for DBL, and 40-9% for CBL. Jancarik and Proksova (1970) reported that solubility was proportional to pH of the solvent. The solubility of SBM CP (12.3%) at pH 6.1 in the present study was between 7-4% at pH 5"5 and 16% at pH 6"5 reported by Wohlt et al. (1973). Broiler litter CP was more soluble (P<0-005) than CP in SBM. Among processing methods composting tended to reduce (P<0.1) solubility of CP when compared with deepstacking. Nitrogenous compounds, especially NH3, may have volatilized due to aerating of CBL during processing.

Solubilities of CP determined in vitro were lower than those determined in situ. If in vitro results were used as an index, soluble CP was overestimated by 31, 45, 44, and 96% for SBM, EBL, DBL, and CBL, respectively, by the in situ method. Composting yielded a humus-like product with very fine particles. Any particles washed out through the pores at 0 h contributed to the soluble CP estimates, but the particles would have been degraded at the same rate as insoluble protein (Mahadevan et al., 1980; Nocek et al., 1983).

In situ Experiment 2 Deepstacked broiler litter was charred partially at Farm 1 and mostly (over 90%) at Farm 2. For DBL collected at Farm 1, DM in charred samples was lower (P<0-05) than in surface and normal samples (Table 3). Soluble A and degradable B fractions of DM were similar, but the undegradable C fraction was lowest for charred samples. For DBL collected at Farm 2, percentage of DM was lower in surface and charred than in normal samples. Soluble A and degradable B fractions of surface samples were lower (P<0"05) and undegradable C fraction was higher (P<0"05), when compared with normal samples. Data for charred litter samples were inter- mediate between surface and normal samples. Dry matter degradabilities of surface and charred DBL from Farm 2 were low compared with those from Farm 1.

In spite of the lower DM content of charred, compared with normal and surface samples from Farm 1, CP content of the samples was similar (Table 4). Charred litter CP from Farm 1, however, contained more (P<0.05) soluble A fraction than normal litter, and less (P<0"05) undegradable C fraction than other litters (Table 4). Litter samples from Farm 2 contained less CP than samples from Farm 1. Surface samples had the lowest CP content, possibly due to N leaching and volatilization, since the litter was not protected from the weather. The undegradable fraction of samples from Farm 2 was considerably higher than samples from Farm 1 or samples processed for Experiment 1. The higher values may have resulted from weather exposure of the litter. Most of the litter inside the stack was charred. This charred litter was of low nutritional quality, and not very suitable as a feedstuff. Van Soest (1987) indicated that overheating during processing rapidly decreased soluble protein by denaturation and exponentially increased indigest- ible protein via the Maillard reaction. Feedstuffs vary in their potential for supporting the Maillard reaction during processing (Goering et al., 1972). For example, a considerable amount of N in many

Ruminal solubility and degradability of broiler litter 17

Table 3. Percentage, in situ fractions, and degradation rate of degradable fraction of dry matter in sheltered (Farm 1) and unsheltered (Farm 2) deepstacked broiler litter

Item Deepstacked broiler litter SE

Surface Normal Charred

Farm 1 Dry matter (%) 83.6 a 81.5 a 62.7 b 1.5 Dry matter fractions (%)

Soluble A 31-5 41.2 37.5 2.6 Degradable B 42-4 29.1 40.6 2-2 Undegradable C 26.1 "'b 29.7 b 21.9 a 0"6

KdB d (%/h) 4.7 3.9 5"7 0"4 DM degradability at KvB of 0"05 50.3 54-0 58.4 1"5

Farm 2 Dry matter (%) 40.7" 80"5 b 50.3 c 0"8 Dry matter fractions (%)

Soluble A 29-1" 43"3 b 35"8 a'b 1"1 Degradable 9-3 a 17.3 b 13.9 a'b 0.8 Undegradable C 61-7 a 39"5 b 53"2 c 0"5

KaB d (%/h) 8"0 6"6 5'6 2"2 DM degradability at KpB of 0"05 36"0" 53-2 b 41'1" 1"5

~"b'CMeans within a row lacking a common superscript differ (P < 0.05). JDegradation rate of degradable B fraction.

commerc ia l dehydra ted alfalfa hays was unavailable for animal use due to overheat ing (Goering, 1976).

C O N C L U S I O N S

Our results indicate that quality of commerc ia l broi ler litter may vary considerably, because CP content and distribution of N be tween soluble, degradable , and undegradab le fract ions were highly dependen t on preserva t ion m e t hod and exposure to the envi ronment . Lit ter of high N solubility and

degradabil i ty and low D M degradabil i ty appears to be more suitable as feed for ruminants at low to m e d i u m product ion. Ensiling and deepstacking produce a desirable p roduc t if appropr ia te pro- cedures are used. G o o d m a n a g e m e n t of deeps tacked litter is needed to avoid charring.

A C K N O W L E D G E M E N T S

Suppor ted in part by John Lee Prat t Animal Nutri- tion Program.

Table 4. Percentage, in situ fractions, and degradation rate of degradable fraction of crude protein in sheltered (Farm 1) and unsheltered (Farm 2) deepstacked broiler litter

Item Deepstacked broiler litter SE

Surface Normal Charred

Farm l Crude protein (%) 32.8 27.9 30"1 3.5 Crude protein fractions (%) Soluble A 74"8 a'b 69-4" 79"2 b 1-2 Degradable B 14.8 18.2 14.9 1.0 Undegradable C 10.4" 12.4 a 5'9 b 0"5

KdB d (%/h) 5"4 3"6 6'9 0"7 CP degradability at KpB of 0'05 82.2 "'b 77-5" 87'9 b 1.5

Farm 2 Crude protein (%) 16"0 a 24"3 b 23"9 b 0.8 Crude protein fractions (%) Soluble A 66.2 74-4 57.6 2.8 Degradable B 10.8 10-0 16.1 1-7 Undegradable C 23-0 15.4 26-4 1.7

KdB ° (%/h) 3.1 7-6 5"8 2.0 CP degradability at KpB of 0"05 72"9 a'b 80"5" 67"0 b 1"5

a'bXMeans within a row lacking a common superscript differ (P <0-05). dDegradation rate of degradable B fraction.

18 W Kwak et al.

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