Bark Broiler Litter as a Potential Feedstuff for Ruminants

Bark Broiler Litter as a Potential Feedstuff for Ruminants

Bark Broiler Litter as a Potential Feedstuff for Ruminants PETER LABOSKY, JR. 1 , J. W. DICK2 and D. L. CROSS 3 1 Department of Forestry, 2 Departmen...

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Bark Broiler Litter as a Potential Feedstuff for Ruminants PETER LABOSKY, JR. 1 , J. W. DICK2 and D. L. CROSS 3 1

Department of Forestry, 2 Department of Poultry Science and 3Department of Animal Science, Clemson University, Clemson, South Carolina 29631 (Received for publication April 25, 1977)

ABSTRACT To assess the potential use of both softwood and hardwood bark broiler litters as a feedstuff for ruminants, the nutrient composition and in vitro digestibility for both raw and ensiled bark litters were chemically evaluated and compared to softwood planer shavings broiler litter. Each bark type was either processed or used directly as it came from the rosserhead debarker. Ensiling studies showed the lactic acid content was higher for hardwood bark litters than for softwood planer shavings. Softwood bark litter contained the least amount of lactic acid after fermentation in mini-silos. In vitro dry matter digestibility was higher for hardwood bark litters than for softwood bark litters or softwood planer shavings. No difference in in vitro dry matter digestibility was observed between raw and ensiled bark litter. No differences in ash, phosphorus, ether extract, nitrogen, total energy, and acid detergent fiber content were observed among the litters tested. The pH. of ensiled hardwood bark was lower than ensiled softwood bark. Results indicate that from a nutritive standpoint, bark litters are potentially useful as a ruminant feed. Hardwood bark litter also appears to ensile better and to be more digestible and possibly more nutritious than softwood bark and softwood planer shavings litter. Poultry Science 56:2064-2069, 1977 INTRODUCTION T h e use of p o u l t r y waste as a feed supplem e n t for r u m i n a n t s has received considerable a t t e n t i o n by b o t h p o u l t r y and beef cattle producers during t h e past five years. Several states have n o w approved legislation allowing for t h e recycling of p o u l t r y wastes into b o t h poultry and cattle diets (Cross, 1 9 7 5 ) . Earlier workers f o u n d t h a t it was feasible t o feed either raw or ensiled p o u l t r y litter t o cattle (Noland et al, 1 9 5 5 ; F o n t e n o t et al, 1 9 7 1 ) . However, palatibility and disease organisms are potential p r o b l e m s when raw litter is fed t o animals (Cross, 1975). Feeding trials have shown t h a t litter rations are b o t h acceptable and n u t r i t i o u s t o t h e animal (Creger, 1 9 7 5 ; Creger et al, 1 9 7 3 ; Cross, 1 9 7 5 ; Cross and J e n n y , 1 9 7 6 ; F o n t e n o t et al, 1 9 7 1 ; Noland et al., 1955). F o n t e n o t et al., ( 1 9 7 1 ) r e p o r t e d t h a t p o u l t r y litter is a good source of nitrogen and minerals for r u m i n a n t s . Weight gains of over 1 kg. per h e a d p e r day have been r e p o r t e d using ensiled p o u l t r y waste as part of t h e feed ration (Creger, 1 9 7 5 ; Cross etal, 1 9 7 6 ) . Poultry litter m a n u r e s can vary widely in chemical analysis. Studies have s h o w n t h a t t h e protein c o n t e n t in p o u l t r y litter is d e p e n d e n t on such factors as t h e n u m b e r of birds reared on t h e litter and t h e t y p e of feed m a n a g e m e n t used in t h e p o u l t r y h o u s e (Cross, 1 9 7 5 ; Creger, 1975). T h e digestibility of t h e p o u l t r y waste

will also be d e p e n d e n t in p a r t o n t h e t y p e of litter used in t h e house ( A n o n y m o u s , 1 9 7 5 ; Baker et al., 1975). Since t h e p o u l t r y industry has t u r n e d t o substitute litter materials, such as bark, it would be useful t o t h e r u m i n a n t n u t r i t i o n i s t t o establish t h e p o t e n t i a l n u t r i e n t c o m p o s i t i o n and digestibility for various types of b a r k litter (Weldon, 1 9 6 9 ; Labosky et al, 1 9 7 7 ; Cochran, 1968). This s t u d y examines and compares t h e n u t r i e n t composition and digestibility for b o t h r a w a n d ensiled shortleaf pine bark broiler litter and mixed h a r d w o o d bark broiler litter t o a standard broiler litter, shortleaf pine planer shavings broiler litter.

MATERIALS AND METHODS Five b r o o d s of broilers ( H u b b a r d X Hubb a r d ) were raised on t w o types of bark litters. A split plot design was used to d e t e r m i n e t h e effects of bark litter t r e a t m e n t a n d ensiling o n the n u t r i e n t composition and in vitro digestibility of b o t h b a r k types. T h e litter types used in t h e e x p e r i m e n t were: 1) fresh shortleaf pine bark (Pinus echinata L.) used directly as it c a m e from t h e rosserhead debarker; 2) shortleaf pine bark screened t o removed large bark pieces > 5 c m . diameter; 3) fresh mixed h a r d w o o d bark used directly as it c a m e from t h e rosserhead d e b a r k e r (mixed


BROILER LITTER hardwood bark consisted of approximately 50% yellow-poplar (Liriodendron tulipifera L.), 25% red oak {Quercus falcata Michx), and 25% black gum (Nyssa sylvatica Marsh) ); 4) hammermilled and screened mixed hardwood bark and 5) shortleaf pine planer shavings Each treatment was replicated for a total of ten trial pens. Day old chicks were placed into each pen and each bird was allocated 0.08 m. 2 of floor space. Standard broiler rations were fed throughout the eight week grow-out period. Between trials, heavily caked litter material was removed and replaced with fresh litter. Only after the fifth brood was caked litter material retained and incorporated into the bark litter samples for further analysis. After the fifth brood was raised on the five different type litters, random samples (70 kg. in weight) were collected from each pen (10 pens total) and thoroughly blended. Approximately 400 g. was collected from each blend and placed into plastic bags. Immediately after collection, these samples were ground in a Wiley mill using a 6mm. diameter screen and the ground samples were placed into sealable bags. Triplicate samples were removed from each bag and freeze dried for nutrient analysis of the raw litter. The remaining blended raw litter samples were ensiled according to the method described by Cross (1975). The method used is described as follows: 1) Approximately 66 kg. of blended raw litter were placed into a horizontal mixer and water added to bring the moisture content to 42%. The contents were mixed for five minutes. 2) The mixed, wet sample was placed in an air impermeable plastic bag. Two minisilos containing five kg. of wet bark were prepared from each pen (20 samples total). 3) Air was evacuated from each bag using a vacuum pump and each bag was sealed with twist wires and placed into 20 liter cans. 4) The mini-silos were packed with wet sand and covered with a lid. 5) All 20 mini-silos (five treatments X two replications X two mini-silos) were stored at a constant room temperature of 22°C. for 60 days.


After the fermentation period, samples were withdrawn for each mini-silo. Two 5 g. samples were used for lactic acid determinations using the method described by Barnett (1951). A 50 g. sample was used to measure pH. Additional samples were withdrawn and freeze dried for nutrient analysis. Acid detergent fiber was determined by the method described by Van Soest and Wine (1967). Ash, ether extract and Kjeldahl nitrogen were determined using standard A.O.A.C. procedures. Litters were wet ashed with nitric and perchloric acid for mineral analysis. Phosphorus was determined colorimetrically using stannous chloride as a reducing agent. Calcium was determined using atomic absorption. Total energy was determined with the bomb calorimeter and in vitro dry matter digestibility was determined by the method described by Baumgardt et al., (1962). Data were analyzed using least-square regression analysis. Differences among means were determined by Duncan's multiple range test (Steel andTorrie, 1960). RESULTS Significant differences (P<.05) in lactic acid content were measured among the ensiled bark broiler litters and planer shavings (Table 1). Lactic acid concentration was highest in both ensiled hardwood bark litters with ensiled unscreened hardwood bark litter containing the highest concentration (7.8 mg./g.). Softwood bark litters contained the least amount of lactic acid after fermentation (average 2.45 mg./g. or lower). An olfactory evaluation was made immediately on opening the mini-silos to determine if fermentation had occurred during the ensiling process. The odor was ranked from 0 to 5 with 5 indicating a pleasant, sweet smell. Each mean represented an average of four mini-silo openings containing identical litters. Sniff tester A found no differences (P<.05) among ensiled litters, whereas sniff tester B ranked ensiled planer shavings the least favorable in odor compared to the four bark litters tested. The mineral content was measured, and the results showed that both ensiled and raw hardwood bark contained more calcium than did the other litters (Table 2). However, no difference (P<.05) in ash content or phosphorus content was measured among litters tested. No significant differences (P<.05) were measured in ether extract and acid detergent fibers for the ensiled and unensiled litters. Although


P. LABOSKY, JR., J. W. DICK AND D. L. CROSS TABLE 1 .—Lactic acid and olfactory evaluation1 of ensiled bark broiler litter


Lactic acid (mg./g.)**

Tester A

Olfactory evaluation Tester B


1.92c 7.20 ab 2.45 bc 7.80a 3.85 abc

3.25 4.0 2.75 2.25 3.25

3.50a 3.25* 3.75a 3.75a 1.50b


Ratings based from 0—5 with 0 = worst smell or musty and 5 = best or very sweet smell; average of 4 tests. *SWB SC = Southern Yellow Pine Bark screened; HWB SC = Mixed Hardwood Bark hammermilled and screened; SWB = Southern Yellow Pine Bark; HWB = Mixed Hardwood Bark; and SHAV = Southern Yellow Pine Wood. **mg. lactic acid/g. of wet litter. ' ' Means in the same column followed by different superscript letters are significantly (P<.05) different.

not significant, the ether extract was consistently higher for the ensiled litters. Softwood barks appeared to contain the highest percentage of ether extractable materials. Acid detergent fiber content ranged from a low of 34.2 to a high of 47.8% for all litters tested. In vitro digestibility results showed that both types of hardwood bark litters were most digestible (P<.05) compared to the other litters. Softwood bark litters appeared to be the least digestible. No significant differences (P<.05) in percent nitrogen and gross energy were observed between ensiled and raw litters. Percent nitrogen ranged from a low of 3.1 to a high of 3.7% whereas, gross energy ranged from a low of 3730 to a high of 3881 calories/g. for all litters. Unensiled softwood bark litter pH. was consistently higher (P<.05) than planer shavings which was higher (P<.05) than hardwood bark litters. DISCUSSION The nutritive value of a feed for ruminants can be estimated by measuring its chemical composition. In this study a number of tests were performed on both ensiled and raw bark litters and planer shavings to estimate their potential nutritive value. Differences were observed and the importance of these differences are now considered in subsequent discussions. Calcium and phosphorus are two of the most important mineral elements required in cattle diets (N.R.C., 1976). Significant differences in calcium content were measured with both types of ensiled and raw hardwood bark litters containing more calcium than did either of the

softwood bark litters or planer shavings. Since all litter material had birds raised on it with the same feed management, these observed differences can be attributed to the type of litter used. This apparently is the case for Choong et al. (1976) also reports that the calcium content is much higher in hardwood bark than in wood. Kramer and Kozlowski (1960) reported that a fourfold increase in calcium was measured in deciduous species as compared to coniferous species. Calcium is reported to appear in the form of calcium oxalate crystals found in the cell walls. Hardwood bark litters can, therefore, be concluded to be rich in calcium compared to either softwood bark litter or softwood shavings. However, all litter materials contained sufficient quantities of calcium and phosphorus to meet the animals' requirements even at low levels of litter feeding. Cattle need digestible protein for growth, maintenance and production. Cattle can also utilize non-protein nitrogen. Only approximately one-third of the nitrogen in poultry litter is non-protein nitrogen (Cross, 1975). It is necessary to know the amount of nitrogen found in broiler litter in order to evaluate its potential as a protein supplement for cattle. Since only a small amount of nitrogen is found in bark as noted in Basham and Thompson, (1967) and Choong et al. (1976), the amounts measured in the litter can be attributed to the broiler droppings in the litter. This is the case because no differences were observed in nitrogen content among the litters tested. Cross (1975) reported that two-thirds of the total nitrogen is in the form of true protein nitrogen after two

14.6 13.2

14.8 13.7

14.4 13.5

Unensiled Ensiled

Unensiled Ensiled

Unensiled Ensiled

Unensiled Ensiled

Unensiled Ensiled






2.7 3.3

3.0 4.0

3.5 4.2

2.8 3.8

4.1 4.2

Ether extract 1

41.4 40.4

34.2 40.9

46.1 47.8

40.1 37.1

47.1 40.2

Acid detergent fiber

3.4 3.2

3.6 3.2

3.1 3.2

3.7 3.2

3.1 3.2

Percent nitrogen 1

Phosphorus 1 1.9 1.7 1.8 1.9 1.9 1.8 2.0 2.0 1.9 2.0

Calcium 1.7 b 1.5b 2.2a 2.2a 1.6^ 1.5b 2.2a 2.0a 1.7b 1.6 b


' ' Means in the same column by different superscript letters are significantly (P<.05) different.

The effect treatment and process were not significant (P>.05).

*SWB SC = Southern Yellow Pine Bark screened; HWB SC = Mixed Hardwood Bark hammermiUed and screened; SW Hardwood Bark; SHAV = Southern Yellow Pine Wood.

13.2 12.4

16.5 14.5





TABLE 2.—Nutrient content of bark broiler litter (percent)


P. LABOSKY, JR., J. W. DICK AND D. L. CROSS TABLE 3 .—Approximate chemical composition of wood and bark} Softwood 2

Acidity-pH. Ash (%) Carbohydrate (%) Lignin (%) Extractives (%) Nitrogen (%) Calcium (p.p.m.) Phosphorus (p.p.m.)

Hardwood 2 ' 3




5.1 0.2 66-71 27-30 3-8 0.1

3.5 0.6-2.5 46.4 52.6 5-10 0.2

5.3 0.4 69-72 24-26 1-4 0.1 737-1575 200-600

Bark 3.7 1.5-10.7 55.1 41.8 2-6 0.2 29,900-40,210 200-600


Based on extractive free wood and bark. Taken from Basham and Thompson (1967). 3 Taken from Choong et al. (1976).


or three groups of birds have been reared on a litter. Considering these observations, it appears that different litter types do not affect the total protein content of poultry litter and that the poultry droppings would be the primary source of nitrogen for protein formation by cattle. In general, if a forage is high in digestibility, the animal will normally consume enough to meet its energy needs. Since in vitro dry matter digestibility estimates ruminal digestibility, in vitro digestibility was determined on the various litters. The results clearly show that both types of ensiled and raw hardwood bark litters were more digestible than the other litters tested. Ensiling did not enhance in vitro digestibility. Softwood bark litters were the least digestible, and this is probably due to the higher lignin content found in softwood bark (Table 3). Although the mechanism for how lignin affects digestion is not fully understood, it is thought that the rumen micro-organisms are not able to dissolve the lignin matrix to attack and hydrolyze the cellulosic material. Similar digestibility trials on wood and bark residues showed that the wood and bark of softwood species are essentially nondigestible whereas the wood and bark of hardwood species are somewhat digestible (Baker et al, 1975). Roughage is required in a cattle diet in order to stimulate cud-chewing which in turn increases salivation and supplies buffer for maintenance of rumen pH. This requirement is usually met by feeding cattle a good quality hay. However, any roughage substitute could be used provided it can maintain normal rumen

functions and feed intake. Although in vivo trials were not conducted, acid detergent fiber and in vitro digestibility results indicate that all the litters tested could be used as either a roughage extender or a partial roughage substitute. Previous studies using ensiled poultry litter as an animal feed have proved successful. It was found to be both feasible and economical to ferment broiler litter and the feedstuff proved palatable to the animal (Creger, 1975; Cross, 1975; Cross and Jenny, 1976). However, there was some question as to the feasibility of utilizing softwoods as a feedstuff for ruminants because of its terpenes and other volatiles resinous compounds which are thought to be toxic or inhibiting to micro-organisms of the ruminant (Koch, 1972). Since both ensiled and raw litters were chemically evaluated and no major differences in nutrient content were observed, it appears that from a nutritive standpoint either would be suitable as a feedstuff. However, although not apparent in the analysis, several differences were observed and reported by earlier investigators. First, the dust problem is avoided during ensiling. Most importantly the acid producing bacterum, Lactobacillus acidophilus, will kill most species of harmful bacteria that can be present in raw broiler litters. Creger (1975) reported it is possible to formulate a feed for beef cattle using chicken droppings without going through the fermentation process, but salmonella contamination of the feed is enhanced. Nonetheless, the current ensiling studies showed that it is feasible to ensile both

BROILER LITTER h a r d w o o d and softwood b a r k p o u l t r y litters. Although in vivo trials were n o t r u n , t h e results indicate t h a t t h e fermented litter would be b o t h nutritious and palatable t o cattle.

ACKNOWLEDGEMENT Appreciation is expressed t o Mr. J. G. Williams, Jr. for his assistance in t h e statistical analysis.

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