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Feeding value of tree leaves (hybrid poplar and black locust) evaluated with sheep, goats and rabbits
ANIMAL FEED SCIENCE AND TECHNOLOGY
ELSEVIER
Animal Feed Science Technology 57 (1996) 51-62
Feeding value of tree leaves ( hybrid poplar and black locust) evaluated with sheep, goats and rabbits AC. Ayers a, R.P. Barrett b, P.R. Cheeke a,* ’Department of Animal Sciences, Oregon State University, Corvallis. OR, 97331, USA b Department of Forestry, Michigan State University, East Lansing, MI 48824, USA Received 13 April 1994; accepted 18 July 1995
Abstract Feeding trials were conducted with rabbits, sheep and goats to evaluate black locust (Robinia pseudoacacia) and hybrid poplar (Populus spp.) leaves as animal feed. The crude protein (CP),
neutral detergent fiber (NDF), and acid detergent fiber (ADF) values for black locust (BL) foliage used in the feeding trials were: CP, 17.8%; NDF, 48.1%; ADF, 29.8%. The hybrid poplar (HP) foliage used in Experiment 1 (rabbit trial) contained CP, 14.77%; NDF, 42.09%; ADF, 29.26%. In Experiment 2 (sheep trial), the HP contained: CP, 11.40%; NDF, 36.39%; ADF, 29.45%. In Experiment 1, 10 New Zealand White (NZW) weanling rabbits per treatment were fed diets with 40% alfalfa meal (AM), and 10, 20 and 40% dried HP leaves substituted for AM. Digestibilities for AM diet and the average of all HP diet treatments were: crude protein (CP): 78.8 vs. 63.9% (P < 0.05); ADF: 26.3 vs. 18.1%; NDF: 36.9 vs. 26.3% (P < 0.05); dry matter (DM): 64.4 vs. 58.3%; ash: 60.6 vs. 49.8% (P < 0.05). Average daily gain (ADG) and DM intake were 35.5 g vs. 37.7 g and 106 g vs. 121 g (P < 0.05) for AM and HP. In Experiment 2, 10 mature crossbred ewes were fed diets with 50% AM or 50% HP for 14 days. Nutrient digestibilities for AM and HP diets were: DM: 75.5 vs. 67.0; CP: 84.3 vs. 55.4; ADF: 51.7 vs. 24.8; NDF: 54.1 vs. 41.1; ash: 62.6 vs. 51.0. All values were lower (P < 0.05) for HP. In Experiment 3, BL leaf meal and AM were fed each at 25% of the diet to 10 NZW weanling rabbits per treatment, with 50% AM in the control diet. BL treatments were BL alone, BL + 1% polyethylene glycol (PEG), BL + 1% phytase and BL + 0.3% DL methionine + 0.3% choline chloride. PEG binds tannins; phytase may increase P availability and methyl donors are needed for metabolism of phenolic acids. A 20 day trial was conducted. The % digestibility for AM vs. all BL treatments were: CP: 77.1 vs. 60.7; ADF: 15.8 vs. 6.7; NDF: 25.8 vs. 18.6; DM: 68.8 vs. 63.2; ash, 75.3 vs. 67.8; Ca: 84.5 vs. 74.8; P: 70.3 vs. 62.1. All BL values were lower than for AM (P < 0.05). ADG was 37.0 g vs. 31.9 g
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A.C. Ayers et al./Animal Feed Science Technology 57 (1996) 51-62
52
(P < 0.05) for AM and all BL treatments. Addition of PEG increased (P < 0.05) CP digestibility compared to the unsupplemented BL diet (55.8 vs. 66.3%). The other supplements had no effect on BL digestibility and ADG. In Experiment 4, 4 mature ewes and 4 mature female Angora goats were fed diets of 100% BL or AM in a digestibility trial. Within diet, there were no differences between sheep and goats. With both species combined, digestibilities for AM vs. BL were: DM: 61.9 vs. 44.5; CP: 78.8 vs. 40.1; ADF: 30.4 vs. -21.8; NDF: 28.9 vs. 2.9; ash: 50.4 vs. 33.1. All values for BL were lower (P < 0.05) than for AM. The negative ADF digestibility is probably due to formation of CP-tannin complexes in the gut. Daily kg DM intake kg-’ BW for AM and BL were 0.0341 vs. 0.0180. Both HP and BL leaves have lower feeding value than AM, probably due to adverse effects of tannins. Keywords:
Tree leaves; Digestibility; Tannins; Goat; Rabbit; Sheep
1. Introduction Tree foliage is a common feedstuff for animals, particularly for browsing species such as goats. In the US Pacific Northwest, extensive areas of fast-growing trees such as
hybrid poplars are grown in rapid-cycle plantations for wood pulp. Large amounts of leaf residue are produced, which may have potential as an animal feedstuff. The objective of this study was to evaluate the foliage of hybrid poplar (Populus spp.) and the nitrogen-fixing black locust (Robinia pseudoacacia) as feedstuffs for small livestock (rabbits, sheep and goats). Phenolic compounds (e.g.tannins) occur in poplars (Palo, 1984) and black locust (Kumar and Horigome, 1986); they act as chemical defenses against herbivory. It was hypothesized that the presence of phenolics might impair protein digestibility, and that a browsing animal, the goat, might be less sensitive to the effects of phenolics because of evolutionary pressures selecting for phenolic detoxication, such as salivary tannin-binding proteins (Austin et al., 1989). In a series of four trials, the digestibility of hybrid poplar (HP) and black locust (BL) foliage-containing diets was determined. The effects of dietary additives which counteract phenolics, such as polyethylene glycol, on digestibilities and growth performances of rabbits were examined. Comparative digestibility of BL foliage and alfalfa meal (AM) in sheep and goats was determined.
2. Materials and methods Approximately ten-year old BL and HP trees were cut down, and the leaves hand-harvested. The leaves were sun-dried on screens, and when dry were ground in a hammer-mill. Because of the high moisture content of the leaves (90-95%), a large quantity of harvested leaves produced a relatively small amount of dried leaf meal. The length of the digestibility trials and number of animals per treatment, especially for the sheep and goats, were thus limited by the quantity of leaf meal available. Samples were analyzed for dry matter (DM) and ash by standard procedures (AOAC, 19841, crude protein (CP) by macro-Kjeldahl analysis (AOAC, 19841, and neutral detergent fiber (NDF) and acid detergent fiber (ADF) by a micro-method (Waldem,
A.C. Ayers et al./Animal Feed Science Technology 57 (1996) 51-62
53
Table 1 Ingredient (as fed basis) and chemical composition (I) of rabbit diets (Experiment 1) Diet number
Ingredient, % Alfalfa meal, sun-cured Corn oil Dicalcium phosphate Molasses Limestone Hybrid poplar leaf meal Soybean meal Trace mineral salt Wheat mill run Vitamin mix Chemical analysis (DM basis) Crude protein ADF NDF Ash Chemical analysis (DM basis)
Hybrid poplar leaves Alfalfa meal
1
2
3
4
40 1 0.25 3
30 1 0.5 3 0.25 10 10 0.5 48.5 0.25
20 1 0.5 3 0.5 20 10 0.5 48.3 0.25
_ 1 0.5 3 0.5 40 10 0.5 48.3 0.25
18.0 19.7 37.3 7.6
18.1 19.8 34.7 7.9
18.7 18.4 33.3 7.7
Crude protein
ADF
NDF
Ash
N-ADF ’
14.77 20.29
29.26 29.45
42.09 38.65
8.98 10.12
0.94 0.41
_ 10 0.5 49 0.25 of diets: 18.9 20.0 38.8 7.4 of ingredients:
a Nitrogen contained in the ADF fraction.
1971) based on the Goering and Van Soest (1970) procedure. Calcium was measured by atomic absorption spectrometry (AOAC, 1984), and phosphorus was measured colorimetrically by the vanadomolybdate method (AOAC, 1984). 2.1. Experiment
1
Ten individually-caged weanling New Zealand White (NZW) rabbits of 5 weeks of age were assigned to treatments of 0, lo%, 20% and 40% HP foliage. A diet with 40% AM was the control (Table 1). The HP was substituted directly for AM. The trial consisted of a 1Cday adaptation period followed by a 7&y digestibility trial. Total fecal collection was made on screens underneath each cage. Apparent digestibilities of proximate categories of the total diets were determined. The experimental diets were offered ad libitum; body weights were measured weekly and at the beginning and end of the digestibility period. 2.2. Experiment
2
The objective was to compare digestibilities of HP leaf meal and AM in a diet for mature sheep. Five Sulfolk X Hampshire ewes of about 67 kg body weight were randomly assigned to each of 2 treatments: HP diet or AM diet (control). The diets
54
A.C. Ayers et al. /Animal Feed Science Technology 57 (1996) 51-62
Table 2 Ingredient (as fed basis) and chemical composition (%I of sheep diets (Experiment 2) Alfalfa diet Ingredient, % Alfalfa, sun-cured 50 Poplar leaves Ground barley 21.5 Molasses 5 Trace mineralized salt 0.5 Vegetable oil 3.0 Wheat mill run 20 Chemical analysis (DM basis) of diets: Crude protein 16.8 ADF 20.4 NDF 34.7 Ash 8.7 Chemical analysis (DM basis)of ingredients:
Poplar leaves Alfalfa
Poplar diet
50 21.5 5 0.5 3.0 20 11.9 19.8 32.0 8.7
Crude protein
ADF
NDF
Ash
11.40 20.30
29.45 26.02
36.39 38.65
9.88 10.12
contained 50% either AM or HP (Table 2). The trial consisted of an &day adaptation period followed by a 6-day digestibility period. The sheep were housed in wooden metabolism crates in a barn with constant lighting. The sheep were offered and consumed 2 kg (as fed basis) of feed per day (3% of body weight). After the end of the digestibility period, total feces were weighed and a subsample was oven dried at 60 “C for 48 h. Digestibilities of NDF, ADF, ash, CP and DM were determined. 2.3. Experiment
3
The objective was to determine the effects of various dietary additives on the digestibility of BL leaf meal in rabbits. Previous BL feeding trials with rabbits, chickens and sheep have shown poor growth, low CP digestibility, and low bioavailability of phosphorus (Horton and Christensen, 1981; Harris et al., 1984; Raharjo et al., 1990; Takada et al., 1980). Condensed tannins are likely responsible for these effects (Kumar and Singh, 1984). Polyethylene glycol (PEG) binds tannins and reduces their adverse effects (Oh et al., 1980). Methionine and choline chloride act as methyl donors for the methylation and excretion of absorbed phenolic acids. Sulfur amino acids are also implicated in tannin detoxification. Thus these additives were used to determine if they improved the utilization of diets containing 25% BL, substituted for an equal amount of AM in the control diet (Table 3). The chemical composition of the BL meal was the same as listed for Experiment 4. Phytase was used to evaluate its effect on the availability of P. Additive levels were 1% PEG, 1% phytase, 0.3% DL-methionine and 0.3% choline chloride. Eight weanling NZW rabbits of 5-6 weeks of age were assigned
A.C. Ayers et al./Animal
Feed Science Technology 57 (1996) 51-62
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Table 3 Ingredient (as fed basis) and chemical composition (%) of rabbit diets (Experiment 3) Diet number
Ingredient, % Alfalfa meal, sun-cured Black locust leaves Ground barley Molasses Trace mineral salt Vegetable oil Vitamin mix Choline chloride L-Methionine
1
2
3
4
5
50
25 25 42.5 5 0.25 2 0.25 _
25 25 41.5 5 0.25 2 0.25
25 25 41.5 5 0.25 2 0.25
25 25 41.9 5 0.25 2 0.25 0.3 0.3
42.5 5 0.25 2 0.25
_
_
Phytase Polyethylene glycol Chemical analysis (DM basis): Crude protein ADF NDF Ash Ca P
15.53 18.53 30.32 7.02 0.98 0.33
15.70 18.34 30.27 7.44 1.49 0.27
_
1
1
_
15.60 18.85 30.11 7.68 1.61 0.25
15.9 18.49 29.55 7.84 1.43 0.28
_
16.31 18.86 29.80 7.67 1.64 0.30
to each treatment. The trial consisted of a 10 day adaptation period and a 10 day fecal collection period. Diets were fed ad libitum. 2.4. Experiment
4
The digestibilities of BL and AM were compared in sheep and goats. The experimental design was a 2 X 2 Latin Square conducted in two replicates, with animals switched to the alternate diet in the second replicate. Four crossbred ewes (about 85 kg body weight) and 4 Angora goat does (about 38.5 kg body weight) were used. The diets were 100% AM (control) or BL leaf meal. The % composition of the AM and BL were: CP: 18.7, 17.8; ADF: 25.0, 29.8; NDF: 35.9, 48.1; ash: 10.0, 6.5, respectively. The first replicate was preceded by a 6 day adaptation period, followed by the two replicates of 7 days each. During the collection periods, sheep were offered 2.2 kg of AM per day (2.6% of SW) or 2.0 kg of BL (2.3% of SW>. Goats were offered 1100 g AM per day (2.8% BW) or 1000 g BL per day (2.6% of SW>. The BL leaves were air-dried and fed in a coarsely chopped form. The AM was commercially-available chopped material. Feed offered is expressed on an as-fed basis. 2.5. Statistics The data were analyzed using the general linear model procedure @AS, 1985). Treatment means were compared using pre-planned comparisons.
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A.C. Ayers et al. /Animal Feed Science Technology 57 (1996) 51-62
3. Results and discussion 3.1. Experiment
1
There was no difference in growth rates of rabbits on the various diets, even though digestibilities were lower on diets with HP than for the AM control (Table 4). Greater gut fill on the HP-containing diets, associated with the higher feed intakes with these diets (Table 4), may compromise accuracy of the weight gain data. The reduced CP digestibility with increasing dietary HP is likely due to effects of tannins. The HP leaves had about twice the amount of N bound to ADF as did the alfalfa (Table 1) which may have contributed to the lower digestibility. 3.2. Experiment
2
The digestibilities of CP, ADF, NDF, DM and ash were all lower (P < 0.05) for the HP leaf diet than for the AM diet (Table 5). The reduced digestibility is probably due to the effects of tannins. According to Palo (1984), phenolics are the only class of defensive chemicals in the family Sulicuceae (in which Populus spp. are taxonomically located). Poplar leaves are reported to contain tannins (Meyer and Montgomery, 1987). We did not conduct a tannin analysis. The contribution of metabolic fecal nitrogen to total fecal nitrogen would presumably be greater with the HP diet; this could have some influence on the apparent CP digestibility. 3.3. Experiment
3
The dietary inclusion of 25% BL reduced growth rate of rabbits, as well as digestibilities of DM, CP, NDF, ADF, ash, Ca and P (Table 6). These effects are likely due to the presence of tannins in the BL leaves. Tannins may be classified as condensed or hydrolyzable tannins (Salunkhe et al., 1990). The BL leaves contain primarily condensed tannins (Kumar and Horigome, 1986). Tannins precipitate proteins by hydrogen-bonding and hydrophobic interactions (Haslam, 1974). Kumar and Horigome (1986) examined the nature of BL tannins. The proanthocyanidins (condensed tannins) in BL may exist in 5 molecular sizes. Their protein-precipitating capacity increases with an increasing degree of polymerization. Horton and Christensen (198 1) found that when lambs were fed BL leaves as a sole feed, the digestibilities of organic matter, CP, ADF, NDF and P were less than half those of AM. Although no significant differences were seen between lambs fed BL leaves and AM in terms of ADG or DM intake, they concluded that BL was not a satisfactory replacement for AM. Harris et al. (1984) found ADG for weanling rabbits fed a 40% BL diet to be lower than for the AM control even though DM intake was higher for the BL diet. Raharjo et al. (1990) also found ADG to be lower for rabbits fed a 50% BL diet when compared to an AM control, and reported twice as much N bound to the ADF fraction in the diets containing BL leaves as compared to the AM control diet. In our experiment, the addition of 1% PEG improved crude protein digestibility from 58.8% to 66.3%. This is in agreement with the findings of Horigome et al. (19841, who
a different than b (P < 0.05).
2. 10% Hybrid poplar 3. 20% Hybrid poplar 4. 40% Hybrid poplar
35.5 f 2.7 39.7 + 2.7 36.7 f 2.7 37.9*3.1
gain (g)
Ave. daily
and nutrient digestibilities
1.40%Alfalfa
Treatment
Table 4 Performance
105.6f4.9 117.3f4.9 122.3 f 4.9 133.9f5.5
Daily DM intake (g)
(means+SE)
3.4kO.2 3.3 f 0.2 3.8 f 0.2 4.0 f 0.2
Feed/gain
78.75 68.71 60.05 54.76
CP 26.28 19.04 18.40 10.15
ADF a jz 4.01 b f 4.01 b *4.01 b k4.48
36.87 29.53 20.88 18.79
NDF
1)
a f 3.82 b f 3.82 b k3.82 b f 4.27
hybrid poplar leaf meal (Experiment (%)
a f 2.11 bf2.11 b k2.11 b f 2.36
Digestibility
for rabbits fed diets containing
DM 64.35 59.02 55.72 57.63
rt 2.76 f 2.76 f 2.76 -f: 3.08
Ash 60.62 51.93 48.95 44.73
= f 2.02 b *2.02 b *2.02 b f 2.26
Y
58
A.C. Ayers et al. / Animal Feed Science Technology 57 (I 996) 51-62
found that adding 1.6% PEG to rat diets containing BL leaves increased CP digestibility from 49.1% to 70.7%. Only 46% of the PEG was recovered in the feces compared to 91% from a diet containing brewers’ grains, thus showing that a water-insoluble complex was formed in the gut. Pritchard et al. (1988) fed sheep Acacia aneuru (which contained 6.1% tannins) and found that drenching the sheep every day with PEG increased body weight and wool growth. These findings contrast with those of NunezHemandez et al. (19911, who determined that adding PEG to diets containing mountain mahogany leaves, which have condensed tannins, did not improve nutrient digestion or affect N balance in goats and lambs. Garrido et al. (1991) found that the addition of PEG to faba bean seed coat, at a level of 200 mg of PEG per gram of seed coat, increased CP digestibility in vitro from 52.4% to 75.5%. A reduction of 97% of the tannins was observed by the addition of increasing levels of polyvinylpyrrolidine. Tannins may affect not only CP digestibility but the digestibilities of other nutrients as well. A lower digestibility of DM and energy was observed in lambs fed BL as compared to AM (Horton and Christensen, 1981). In our study, ADF digestibility was also improved by addition of PEG to the BL diet. The ADF was poorly digested for the control BL diet (2.63%), but increased slightly to 8.55% with addition of PEG. Insoluble tannin-fiber complexes may be measured as ADF in the feces to give very low ADF digestibilities (Cheeke, 1992). It is evident from the NDF values in this study that the hemicellulose portion is better utilized for the AM control than the BL treatments. The effect that tannins may have on mineral availability is not entirely clear, but tannins appear to form insoluble complexes with divalent metal ions which make them less absorbable (Salunkhe et al., 1990). Horton and Christensen (1981) found P to be poorly digested by lambs fed BL. In our study, Ca and P were less available in the BL control diet as compared to the AM control and the addition of phytase did not improve P or Ca utilization; however, there was a trend towards improved DM digestibility with addition of phytase. If tannins rather than phytate are responsible for the low P availability, then phytase might not be effective. The addition of methionine and choline chloride to the BL diet did not improve CP digestibility, but it did improve ADF digestibility, giving an increase from 2.63% to 8.81%. The explanation for this response is not apparent. There was also a trend towards improved P utilization with addition of methionine and choline chloride. In a study by Myer et al. (19861, dietary methionine was not effective in alleviating the detrimental effects of tannins on swine. No improvement was seen in ADG or feed efficiency. Fuller et al. (1967) found that adding methionine hydroxy analogue or choline to diets
Table 5 Means ( f SE) of nutrient digestibilities sheep (Experiment 2)
Alfalfa diet Podar diet
(%) of diets containing
50% alfalfa or 50% poplar leaf meal fed to
Crude protein
ADF
NDF
Dry matter
Ash
84.25 a f 1.39 55.44 b f 1.56
51.74 = L-3.07 24.84 b f 3.43
54.12 a rt2.63 41.12 b L-2.95
75.48 B*0.97 67.02 b f 1.09
62.64 = f 1.77 51.00 b f 1.97
a differs from b (P < 0.05).
66.30
60.06 f I .34
57.71 f 1.34
60.73
(Co”trol) 2. 25% Alfalfa
and 25% BL (black locust Control) 3.Black locust
Control + PEG 4. Black locust
Control + phytase 5.Black locust
Control + Lmethionine and choline chloride Average of
Contrasts are: I Alfalfa each of the black locust
2,3,4 and 5 (BL diets)
58.80 f
I. 25% Alfalfa
(%)
1.79
1.79
1.20
1.20
1.20
62.43 + 0.85
64.50 f 0.85
63.64 f 0.85
62.32 f 0.85
18.56 * f 1.20 63.22 f 0.85
17.14+
18.94 f
18.38f
19.79 f I .20
* 67.76
1.7
94.7 f 3.2
94.4 * 3.2
91.2 k 3.2
100.1 it 3.2
93.0 f 3.2
by *, 2. Black locust control
* f 1.7
33.3 * 1.7
31.4*
32.4 f 1.7
30.4 f 1.7
95.9 f 3.2
(g)
gain (g) 37.0 f 1.7
Daily DM inlake
parameters
Average daily
* f 2.39 31.9
64.83 f 2.39
63.65 f 2.39
61.60 f 2.39
58.48 f 2.39
3)
Performance
(Experiment
70.33 f 2.56
P
additives
* f 1.58 62.14
74.58 * I .58
73.72 f I.58
75.33 * I .58
75.62 f I .58
84.5 I + I .58
Ca
* f 1.34 74.81
67.90 f 1.34
68.67 * 1.34
68.13 f 1.34
66.32 f I .34
75.26 f 1.34
Ash
black locusl leaf meal with various
68.80 f 0.85
DM
fed diets containing
25.78 f I .20
NDF
for rabbits
6.73 * f 1.79
8.81 ‘*f
6.91 * 1.79
8.55 “f
2.63 f 1.79
15.81 * 1.79
ADF
digeslibilities
control vs. black locust treatments (Group I vs. 2,3,4 and 5). Significant differences (P < 0.05) indicated treatments (Groups 3.4 and 5). Significant differences (P < 0.05) from Group 2 indicated by * *.
* f 1.34
’ * f 1.34
77.07 f I .34
I .34
CP
Digestibility
and % nutrienl
Dietary treatment
Table 6 Growh performance
(Group
2) vs.
3.3 * f 0.1
3.2 f 0.1
3.2 f 0.1
3.5 f 0.1
3.4 f 0.1
2.9 f 0.1
Feed gain
alfalfa black locust alfalfa black locust
Sheep Sheep Goats Goats (SE)
29.68 - 15.05 31.15 - 28.62 (*7.91) 30.42 -21.84 ’
78.44 37.56 79.22 42.60 (f3.45) 78.83 40.08 ??
ADF
Crude protein 28.94 5.81 28.83 -0.11 (k6.57) 28.89 2.85 *
NDF
62.14 45.50 61.57 43.41 ( f 3.28) 61.86 44.49
Dry matter
??
??
.0214 .0159 .0253 ’ .0201 * * ( f .0067) .0341 .0180 ’
49.89 33.04 50.84 33.05 ( f 4.76) 50.37 33.05 ’
??
Daily kg intake kg-’ BW
Ash
1838 1371 985 183
(d
Daily intake
?? ??
??
??
Contrasts are: 1. Alfalfa vs. black locust (sheep and goats). Significant differences (P < 0.05) indicated by . 2. Sheep vs. goats on black locust. Significant differences (P < 0.05) indicated by . 3. Sheep vs. goats on alfalfa. Significant differences indicated by * * .
Avg. alfalfa (sheep and goats) Avg. black locust (sheep and goats)
Diet
Species
Table I Nutrient digestibilities and average DM intake kg- ’ of body weight of alfalfa or black locust leaf diets fed to sheep and goats (means f SE) (Experiment 4)
A.C. Ayers et al./Animal
Feed Science Technology 57 (1996) 51-62
61
containing tannic acid partially alleviated the growth depression due to the tannic acid in chicks. They proposed that the methionine probably provides labile methyl groups for the production of 4-O-methyl gallate, found by Booth et al. (1959) to be the major metabolite in the urine of rats and rabbits fed tannic acid and gallic acid. 3.4. Experiment
4
There were no differences between sheep and goats in digestibility values (Table 7). The digestibilities for BL were markedly lower than for AM (Table 7). Tannins in BL are probably the causative factors. Negative values for ADF and NDF digestibilities could be due to tannin-protein complexes formed in the gut. The results are similar to those of Horton and Christensen (1981) with sheep fed either AM or BL. Proline-rich proteins (PRP) in the saliva may provide the first line of defense against tannins in the diet (Mehansho et al., 1987). Mehansho et al. (1987) found that feeding a tannin-rich diet to rats enlarged the parotid glands four-fold and increased the production of PRPs. The rats gained weight at the normal rate. According to Austin et al. (19891, the saliva of mule deer, a browser, has more PRP than the saliva of grazing animals such as cows and sheep, and also has more tannin-binding ability. We theorized that goats, being browsers, would be more equipped to tolerate the tannins in BL leaves than the sheep; however, in our study, no differences were found in the nutrient digestibilities between the two species.
4. Conclusions
Tree foliage has potential as animal feed. In our experiments, the digestibilities of protein and energy were lower for HP and BL foliage than for AM. Tannins in both species are the likely cause of lower nutrient availability, particularly for protein. In rabbits, CP and ADF digestibilities of BL were increased by dietary supplementation with PEG, suggesting a role of tannins in reducing digestibility. Digestibilities of BL leaf meal were similar in sheep and goats, and were markedly lower than for alfalfa.
References AOAC, 1984. Official Methods of Analysis (14th Ed.), Association of Official Analytical Chemists, Washington, DC. Austin, P.J., Suchar, L.A., Robbins, CT. and Hagerman, A.E., 1989. Tannin-binding proteins in saliva of deer and their absence in saliva of sheep and cattle. J. Chem. Ecol., 1.5: 1335-1347. Booth, A.N., Morse, MS., Robbins, D.J., Emerson, O.H., Jones, F.T. and Deeds, F., 1959. The metabolic fate of gallic acid and related compounds. J. Biol. Chem., 234: 30143016. Cheeke, P.R., 1992. Black locust forage as an animal feedstuff. hoc. Int. Conf. on Black Locust: Biology, Culture and Utilization. Dept. of Forestry, Michigan State University. In: Hanover, J.W. (Ed.), pp. 32. Fuller, H.L., Chang, S.I. and Potter, D.K., 1967. Detoxification of dietary tannic acid by chicks. J. Nutr., 91: 477-481. Ganido, A., Gomez-Cabrera, A., Guerrero, J.E. and van der Meer, J.M., 1991. Effects of treatment with
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A.C. Ayers et al. /Animal Feed Science Technology 57 (1996) 51-62
polyvinylpyrrolidone and polyethylene glycol on faba bean tannins. Anim. Feed Sci. Technol., 35: 199-203. Goering, H.K. and Van Soest, P.J. 1970. Forage Fiber Analyses (apparatus, reagents, procedures, and some applications). Agric. Handbook 379. USDA, ARS, Washington, DC. Harris, D.J., Cheeke, P.R. and Patton, N.M., 1984. Evaluation of black locust leaves for growing rabbits. J. Appl. Rabbit Res., 7: 7-9. Haslam, E. 1974. Polyphenol-protein interaction. B&hem. J., 139 285-288. Horigome, T., Ohkuma, T. and Muta, M. 1984. Effect of condensed tannin of false acacia leaves on protein digestibility, as measured with rats. Jpn. J. Zootech. Sci., 55: 299-306. Horton, G.M.J. and Christensen, D.A., 1981. Nutritional value of black locust tree leaf meal (Robinia pseudoacacia) and alfalfa meal. Can. J. Anim. Sci., 61: 503-506. Kumar, R. and Horigome, T., 1986. Fractionation, characterization, and protein-precipitating capacity of the condensed tannins from Robinia pseudoacacia L. leaves. J. Agric. Food Chem., 34: 487-489. Kumar, R. and Singh, M., 1984. Tannins: their adverse role in ruminant nutrition. J. Agric. Food Chem., 32: 447-453. Mehansho, H., Butler, L.G. and Carlson, D.M., 1987. Dietary tannins and salivary proline-rich proteins: interactions, induction, and defense mechanisms. Ann. Rev. Nutr., 7: 423-440. Meyer, G.A. and Montgomery, M.E., 1987. Relationships between leaf age and the food quality of cottonwood foliage for the gypsy moth, Lyrnantria dispar. Gecologia, 72: 527-532. Myer, R.O., Combs, G.E. and Gorbet, D.W., 1986. Effect of methionine addition on the feeding value of diets containing bird-resistant grain sorghum for growing-finishing swine. Nutr. Reports Int., 33: 843-850. Nunez-Hemandez, G., Wallace, J.D., Holechek, J.L., Galyean, M.L. and Cardenas, M., 1991. Condensed tannins and nutrient utilization by lambs and goats fed low-quality diets. J. Anim. Sci., 69: 1167-1177. Oh, HI., Hoff, J.E., Armstrong, G.S. and Haff, L.A., 1980. Hydrophobic interaction in tannin-protein complexes. J. Agric. Food Chem., 28: 394-398. Palo, R.T., 1984. Distribution of birch (Betula spp.), willow (Salti spp.), and poplar (Populus spp.) secondary metabolites and their role as chemical defense against herbivores. J. Chem. Ecol., 10: 499-520. Pritchard, D.A., Stocks, D.C., O’Sullivan, B.M., Martins, P.R., Hurwood, LS. and O’Rourke, P.K., 1988. The effect of polyethylene glycol (PEG) on wool growth and live weight of sheep consuming a Mulga (Acacia aneura) diet. Proc. Aust. Sot. Anim. Prod., 17: 290-293. Raharjo, Y.C., Cheeke, P.R. and Patton, N.M., 1990. Effect of cecotrophy on the nutrient digestibility of alfalfa and black locust leaves. J. Appl. Rabbit Res., 13: 56-61. Salunkhe, D.K., Chavan, J.K. and Kadarn, S.S., 1990. Dietary Tannins: Consequences and Remedies. CRC Press, Boca Raton, FL, 200 pp. SAS, 1985. SAS User’s Guide: Statistics. SAS Inst., Inc., Cary, NC. Takada, K., Nakazato, T., Chro, K., Honda, H. and Yamane, T., 1980. Feeding value of leaf meal of acacia on poultry feed. Jpn. Poultry Sci., 17: 299-305. Waldem, D.E. 1971. A rapid micro-digestion procedure for neutral and acid detergent fiber. Can. J. Anim. Sci.. 51: 67-69.
ELSEVIER
Animal Feed Science Technology 57 (1996) 51-62
Feeding value of tree leaves ( hybrid poplar and black locust) evaluated with sheep, goats and rabbits AC. Ayers a, R.P. Barrett b, P.R. Cheeke a,* ’Department of Animal Sciences, Oregon State University, Corvallis. OR, 97331, USA b Department of Forestry, Michigan State University, East Lansing, MI 48824, USA Received 13 April 1994; accepted 18 July 1995
Abstract Feeding trials were conducted with rabbits, sheep and goats to evaluate black locust (Robinia pseudoacacia) and hybrid poplar (Populus spp.) leaves as animal feed. The crude protein (CP),
neutral detergent fiber (NDF), and acid detergent fiber (ADF) values for black locust (BL) foliage used in the feeding trials were: CP, 17.8%; NDF, 48.1%; ADF, 29.8%. The hybrid poplar (HP) foliage used in Experiment 1 (rabbit trial) contained CP, 14.77%; NDF, 42.09%; ADF, 29.26%. In Experiment 2 (sheep trial), the HP contained: CP, 11.40%; NDF, 36.39%; ADF, 29.45%. In Experiment 1, 10 New Zealand White (NZW) weanling rabbits per treatment were fed diets with 40% alfalfa meal (AM), and 10, 20 and 40% dried HP leaves substituted for AM. Digestibilities for AM diet and the average of all HP diet treatments were: crude protein (CP): 78.8 vs. 63.9% (P < 0.05); ADF: 26.3 vs. 18.1%; NDF: 36.9 vs. 26.3% (P < 0.05); dry matter (DM): 64.4 vs. 58.3%; ash: 60.6 vs. 49.8% (P < 0.05). Average daily gain (ADG) and DM intake were 35.5 g vs. 37.7 g and 106 g vs. 121 g (P < 0.05) for AM and HP. In Experiment 2, 10 mature crossbred ewes were fed diets with 50% AM or 50% HP for 14 days. Nutrient digestibilities for AM and HP diets were: DM: 75.5 vs. 67.0; CP: 84.3 vs. 55.4; ADF: 51.7 vs. 24.8; NDF: 54.1 vs. 41.1; ash: 62.6 vs. 51.0. All values were lower (P < 0.05) for HP. In Experiment 3, BL leaf meal and AM were fed each at 25% of the diet to 10 NZW weanling rabbits per treatment, with 50% AM in the control diet. BL treatments were BL alone, BL + 1% polyethylene glycol (PEG), BL + 1% phytase and BL + 0.3% DL methionine + 0.3% choline chloride. PEG binds tannins; phytase may increase P availability and methyl donors are needed for metabolism of phenolic acids. A 20 day trial was conducted. The % digestibility for AM vs. all BL treatments were: CP: 77.1 vs. 60.7; ADF: 15.8 vs. 6.7; NDF: 25.8 vs. 18.6; DM: 68.8 vs. 63.2; ash, 75.3 vs. 67.8; Ca: 84.5 vs. 74.8; P: 70.3 vs. 62.1. All BL values were lower than for AM (P < 0.05). ADG was 37.0 g vs. 31.9 g
* Corresponding author. 0377~8401/96/$15.00
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A.C. Ayers et al./Animal Feed Science Technology 57 (1996) 51-62
52
(P < 0.05) for AM and all BL treatments. Addition of PEG increased (P < 0.05) CP digestibility compared to the unsupplemented BL diet (55.8 vs. 66.3%). The other supplements had no effect on BL digestibility and ADG. In Experiment 4, 4 mature ewes and 4 mature female Angora goats were fed diets of 100% BL or AM in a digestibility trial. Within diet, there were no differences between sheep and goats. With both species combined, digestibilities for AM vs. BL were: DM: 61.9 vs. 44.5; CP: 78.8 vs. 40.1; ADF: 30.4 vs. -21.8; NDF: 28.9 vs. 2.9; ash: 50.4 vs. 33.1. All values for BL were lower (P < 0.05) than for AM. The negative ADF digestibility is probably due to formation of CP-tannin complexes in the gut. Daily kg DM intake kg-’ BW for AM and BL were 0.0341 vs. 0.0180. Both HP and BL leaves have lower feeding value than AM, probably due to adverse effects of tannins. Keywords:
Tree leaves; Digestibility; Tannins; Goat; Rabbit; Sheep
1. Introduction Tree foliage is a common feedstuff for animals, particularly for browsing species such as goats. In the US Pacific Northwest, extensive areas of fast-growing trees such as
hybrid poplars are grown in rapid-cycle plantations for wood pulp. Large amounts of leaf residue are produced, which may have potential as an animal feedstuff. The objective of this study was to evaluate the foliage of hybrid poplar (Populus spp.) and the nitrogen-fixing black locust (Robinia pseudoacacia) as feedstuffs for small livestock (rabbits, sheep and goats). Phenolic compounds (e.g.tannins) occur in poplars (Palo, 1984) and black locust (Kumar and Horigome, 1986); they act as chemical defenses against herbivory. It was hypothesized that the presence of phenolics might impair protein digestibility, and that a browsing animal, the goat, might be less sensitive to the effects of phenolics because of evolutionary pressures selecting for phenolic detoxication, such as salivary tannin-binding proteins (Austin et al., 1989). In a series of four trials, the digestibility of hybrid poplar (HP) and black locust (BL) foliage-containing diets was determined. The effects of dietary additives which counteract phenolics, such as polyethylene glycol, on digestibilities and growth performances of rabbits were examined. Comparative digestibility of BL foliage and alfalfa meal (AM) in sheep and goats was determined.
2. Materials and methods Approximately ten-year old BL and HP trees were cut down, and the leaves hand-harvested. The leaves were sun-dried on screens, and when dry were ground in a hammer-mill. Because of the high moisture content of the leaves (90-95%), a large quantity of harvested leaves produced a relatively small amount of dried leaf meal. The length of the digestibility trials and number of animals per treatment, especially for the sheep and goats, were thus limited by the quantity of leaf meal available. Samples were analyzed for dry matter (DM) and ash by standard procedures (AOAC, 19841, crude protein (CP) by macro-Kjeldahl analysis (AOAC, 19841, and neutral detergent fiber (NDF) and acid detergent fiber (ADF) by a micro-method (Waldem,
A.C. Ayers et al./Animal Feed Science Technology 57 (1996) 51-62
53
Table 1 Ingredient (as fed basis) and chemical composition (I) of rabbit diets (Experiment 1) Diet number
Ingredient, % Alfalfa meal, sun-cured Corn oil Dicalcium phosphate Molasses Limestone Hybrid poplar leaf meal Soybean meal Trace mineral salt Wheat mill run Vitamin mix Chemical analysis (DM basis) Crude protein ADF NDF Ash Chemical analysis (DM basis)
Hybrid poplar leaves Alfalfa meal
1
2
3
4
40 1 0.25 3
30 1 0.5 3 0.25 10 10 0.5 48.5 0.25
20 1 0.5 3 0.5 20 10 0.5 48.3 0.25
_ 1 0.5 3 0.5 40 10 0.5 48.3 0.25
18.0 19.7 37.3 7.6
18.1 19.8 34.7 7.9
18.7 18.4 33.3 7.7
Crude protein
ADF
NDF
Ash
N-ADF ’
14.77 20.29
29.26 29.45
42.09 38.65
8.98 10.12
0.94 0.41
_ 10 0.5 49 0.25 of diets: 18.9 20.0 38.8 7.4 of ingredients:
a Nitrogen contained in the ADF fraction.
1971) based on the Goering and Van Soest (1970) procedure. Calcium was measured by atomic absorption spectrometry (AOAC, 1984), and phosphorus was measured colorimetrically by the vanadomolybdate method (AOAC, 1984). 2.1. Experiment
1
Ten individually-caged weanling New Zealand White (NZW) rabbits of 5 weeks of age were assigned to treatments of 0, lo%, 20% and 40% HP foliage. A diet with 40% AM was the control (Table 1). The HP was substituted directly for AM. The trial consisted of a 1Cday adaptation period followed by a 7&y digestibility trial. Total fecal collection was made on screens underneath each cage. Apparent digestibilities of proximate categories of the total diets were determined. The experimental diets were offered ad libitum; body weights were measured weekly and at the beginning and end of the digestibility period. 2.2. Experiment
2
The objective was to compare digestibilities of HP leaf meal and AM in a diet for mature sheep. Five Sulfolk X Hampshire ewes of about 67 kg body weight were randomly assigned to each of 2 treatments: HP diet or AM diet (control). The diets
54
A.C. Ayers et al. /Animal Feed Science Technology 57 (1996) 51-62
Table 2 Ingredient (as fed basis) and chemical composition (%I of sheep diets (Experiment 2) Alfalfa diet Ingredient, % Alfalfa, sun-cured 50 Poplar leaves Ground barley 21.5 Molasses 5 Trace mineralized salt 0.5 Vegetable oil 3.0 Wheat mill run 20 Chemical analysis (DM basis) of diets: Crude protein 16.8 ADF 20.4 NDF 34.7 Ash 8.7 Chemical analysis (DM basis)of ingredients:
Poplar leaves Alfalfa
Poplar diet
50 21.5 5 0.5 3.0 20 11.9 19.8 32.0 8.7
Crude protein
ADF
NDF
Ash
11.40 20.30
29.45 26.02
36.39 38.65
9.88 10.12
contained 50% either AM or HP (Table 2). The trial consisted of an &day adaptation period followed by a 6-day digestibility period. The sheep were housed in wooden metabolism crates in a barn with constant lighting. The sheep were offered and consumed 2 kg (as fed basis) of feed per day (3% of body weight). After the end of the digestibility period, total feces were weighed and a subsample was oven dried at 60 “C for 48 h. Digestibilities of NDF, ADF, ash, CP and DM were determined. 2.3. Experiment
3
The objective was to determine the effects of various dietary additives on the digestibility of BL leaf meal in rabbits. Previous BL feeding trials with rabbits, chickens and sheep have shown poor growth, low CP digestibility, and low bioavailability of phosphorus (Horton and Christensen, 1981; Harris et al., 1984; Raharjo et al., 1990; Takada et al., 1980). Condensed tannins are likely responsible for these effects (Kumar and Singh, 1984). Polyethylene glycol (PEG) binds tannins and reduces their adverse effects (Oh et al., 1980). Methionine and choline chloride act as methyl donors for the methylation and excretion of absorbed phenolic acids. Sulfur amino acids are also implicated in tannin detoxification. Thus these additives were used to determine if they improved the utilization of diets containing 25% BL, substituted for an equal amount of AM in the control diet (Table 3). The chemical composition of the BL meal was the same as listed for Experiment 4. Phytase was used to evaluate its effect on the availability of P. Additive levels were 1% PEG, 1% phytase, 0.3% DL-methionine and 0.3% choline chloride. Eight weanling NZW rabbits of 5-6 weeks of age were assigned
A.C. Ayers et al./Animal
Feed Science Technology 57 (1996) 51-62
55
Table 3 Ingredient (as fed basis) and chemical composition (%) of rabbit diets (Experiment 3) Diet number
Ingredient, % Alfalfa meal, sun-cured Black locust leaves Ground barley Molasses Trace mineral salt Vegetable oil Vitamin mix Choline chloride L-Methionine
1
2
3
4
5
50
25 25 42.5 5 0.25 2 0.25 _
25 25 41.5 5 0.25 2 0.25
25 25 41.5 5 0.25 2 0.25
25 25 41.9 5 0.25 2 0.25 0.3 0.3
42.5 5 0.25 2 0.25
_
_
Phytase Polyethylene glycol Chemical analysis (DM basis): Crude protein ADF NDF Ash Ca P
15.53 18.53 30.32 7.02 0.98 0.33
15.70 18.34 30.27 7.44 1.49 0.27
_
1
1
_
15.60 18.85 30.11 7.68 1.61 0.25
15.9 18.49 29.55 7.84 1.43 0.28
_
16.31 18.86 29.80 7.67 1.64 0.30
to each treatment. The trial consisted of a 10 day adaptation period and a 10 day fecal collection period. Diets were fed ad libitum. 2.4. Experiment
4
The digestibilities of BL and AM were compared in sheep and goats. The experimental design was a 2 X 2 Latin Square conducted in two replicates, with animals switched to the alternate diet in the second replicate. Four crossbred ewes (about 85 kg body weight) and 4 Angora goat does (about 38.5 kg body weight) were used. The diets were 100% AM (control) or BL leaf meal. The % composition of the AM and BL were: CP: 18.7, 17.8; ADF: 25.0, 29.8; NDF: 35.9, 48.1; ash: 10.0, 6.5, respectively. The first replicate was preceded by a 6 day adaptation period, followed by the two replicates of 7 days each. During the collection periods, sheep were offered 2.2 kg of AM per day (2.6% of SW) or 2.0 kg of BL (2.3% of SW>. Goats were offered 1100 g AM per day (2.8% BW) or 1000 g BL per day (2.6% of SW>. The BL leaves were air-dried and fed in a coarsely chopped form. The AM was commercially-available chopped material. Feed offered is expressed on an as-fed basis. 2.5. Statistics The data were analyzed using the general linear model procedure @AS, 1985). Treatment means were compared using pre-planned comparisons.
56
A.C. Ayers et al. /Animal Feed Science Technology 57 (1996) 51-62
3. Results and discussion 3.1. Experiment
1
There was no difference in growth rates of rabbits on the various diets, even though digestibilities were lower on diets with HP than for the AM control (Table 4). Greater gut fill on the HP-containing diets, associated with the higher feed intakes with these diets (Table 4), may compromise accuracy of the weight gain data. The reduced CP digestibility with increasing dietary HP is likely due to effects of tannins. The HP leaves had about twice the amount of N bound to ADF as did the alfalfa (Table 1) which may have contributed to the lower digestibility. 3.2. Experiment
2
The digestibilities of CP, ADF, NDF, DM and ash were all lower (P < 0.05) for the HP leaf diet than for the AM diet (Table 5). The reduced digestibility is probably due to the effects of tannins. According to Palo (1984), phenolics are the only class of defensive chemicals in the family Sulicuceae (in which Populus spp. are taxonomically located). Poplar leaves are reported to contain tannins (Meyer and Montgomery, 1987). We did not conduct a tannin analysis. The contribution of metabolic fecal nitrogen to total fecal nitrogen would presumably be greater with the HP diet; this could have some influence on the apparent CP digestibility. 3.3. Experiment
3
The dietary inclusion of 25% BL reduced growth rate of rabbits, as well as digestibilities of DM, CP, NDF, ADF, ash, Ca and P (Table 6). These effects are likely due to the presence of tannins in the BL leaves. Tannins may be classified as condensed or hydrolyzable tannins (Salunkhe et al., 1990). The BL leaves contain primarily condensed tannins (Kumar and Horigome, 1986). Tannins precipitate proteins by hydrogen-bonding and hydrophobic interactions (Haslam, 1974). Kumar and Horigome (1986) examined the nature of BL tannins. The proanthocyanidins (condensed tannins) in BL may exist in 5 molecular sizes. Their protein-precipitating capacity increases with an increasing degree of polymerization. Horton and Christensen (198 1) found that when lambs were fed BL leaves as a sole feed, the digestibilities of organic matter, CP, ADF, NDF and P were less than half those of AM. Although no significant differences were seen between lambs fed BL leaves and AM in terms of ADG or DM intake, they concluded that BL was not a satisfactory replacement for AM. Harris et al. (1984) found ADG for weanling rabbits fed a 40% BL diet to be lower than for the AM control even though DM intake was higher for the BL diet. Raharjo et al. (1990) also found ADG to be lower for rabbits fed a 50% BL diet when compared to an AM control, and reported twice as much N bound to the ADF fraction in the diets containing BL leaves as compared to the AM control diet. In our experiment, the addition of 1% PEG improved crude protein digestibility from 58.8% to 66.3%. This is in agreement with the findings of Horigome et al. (19841, who
a different than b (P < 0.05).
2. 10% Hybrid poplar 3. 20% Hybrid poplar 4. 40% Hybrid poplar
35.5 f 2.7 39.7 + 2.7 36.7 f 2.7 37.9*3.1
gain (g)
Ave. daily
and nutrient digestibilities
1.40%Alfalfa
Treatment
Table 4 Performance
105.6f4.9 117.3f4.9 122.3 f 4.9 133.9f5.5
Daily DM intake (g)
(means+SE)
3.4kO.2 3.3 f 0.2 3.8 f 0.2 4.0 f 0.2
Feed/gain
78.75 68.71 60.05 54.76
CP 26.28 19.04 18.40 10.15
ADF a jz 4.01 b f 4.01 b *4.01 b k4.48
36.87 29.53 20.88 18.79
NDF
1)
a f 3.82 b f 3.82 b k3.82 b f 4.27
hybrid poplar leaf meal (Experiment (%)
a f 2.11 bf2.11 b k2.11 b f 2.36
Digestibility
for rabbits fed diets containing
DM 64.35 59.02 55.72 57.63
rt 2.76 f 2.76 f 2.76 -f: 3.08
Ash 60.62 51.93 48.95 44.73
= f 2.02 b *2.02 b *2.02 b f 2.26
Y
58
A.C. Ayers et al. / Animal Feed Science Technology 57 (I 996) 51-62
found that adding 1.6% PEG to rat diets containing BL leaves increased CP digestibility from 49.1% to 70.7%. Only 46% of the PEG was recovered in the feces compared to 91% from a diet containing brewers’ grains, thus showing that a water-insoluble complex was formed in the gut. Pritchard et al. (1988) fed sheep Acacia aneuru (which contained 6.1% tannins) and found that drenching the sheep every day with PEG increased body weight and wool growth. These findings contrast with those of NunezHemandez et al. (19911, who determined that adding PEG to diets containing mountain mahogany leaves, which have condensed tannins, did not improve nutrient digestion or affect N balance in goats and lambs. Garrido et al. (1991) found that the addition of PEG to faba bean seed coat, at a level of 200 mg of PEG per gram of seed coat, increased CP digestibility in vitro from 52.4% to 75.5%. A reduction of 97% of the tannins was observed by the addition of increasing levels of polyvinylpyrrolidine. Tannins may affect not only CP digestibility but the digestibilities of other nutrients as well. A lower digestibility of DM and energy was observed in lambs fed BL as compared to AM (Horton and Christensen, 1981). In our study, ADF digestibility was also improved by addition of PEG to the BL diet. The ADF was poorly digested for the control BL diet (2.63%), but increased slightly to 8.55% with addition of PEG. Insoluble tannin-fiber complexes may be measured as ADF in the feces to give very low ADF digestibilities (Cheeke, 1992). It is evident from the NDF values in this study that the hemicellulose portion is better utilized for the AM control than the BL treatments. The effect that tannins may have on mineral availability is not entirely clear, but tannins appear to form insoluble complexes with divalent metal ions which make them less absorbable (Salunkhe et al., 1990). Horton and Christensen (1981) found P to be poorly digested by lambs fed BL. In our study, Ca and P were less available in the BL control diet as compared to the AM control and the addition of phytase did not improve P or Ca utilization; however, there was a trend towards improved DM digestibility with addition of phytase. If tannins rather than phytate are responsible for the low P availability, then phytase might not be effective. The addition of methionine and choline chloride to the BL diet did not improve CP digestibility, but it did improve ADF digestibility, giving an increase from 2.63% to 8.81%. The explanation for this response is not apparent. There was also a trend towards improved P utilization with addition of methionine and choline chloride. In a study by Myer et al. (19861, dietary methionine was not effective in alleviating the detrimental effects of tannins on swine. No improvement was seen in ADG or feed efficiency. Fuller et al. (1967) found that adding methionine hydroxy analogue or choline to diets
Table 5 Means ( f SE) of nutrient digestibilities sheep (Experiment 2)
Alfalfa diet Podar diet
(%) of diets containing
50% alfalfa or 50% poplar leaf meal fed to
Crude protein
ADF
NDF
Dry matter
Ash
84.25 a f 1.39 55.44 b f 1.56
51.74 = L-3.07 24.84 b f 3.43
54.12 a rt2.63 41.12 b L-2.95
75.48 B*0.97 67.02 b f 1.09
62.64 = f 1.77 51.00 b f 1.97
a differs from b (P < 0.05).
66.30
60.06 f I .34
57.71 f 1.34
60.73
(Co”trol) 2. 25% Alfalfa
and 25% BL (black locust Control) 3.Black locust
Control + PEG 4. Black locust
Control + phytase 5.Black locust
Control + Lmethionine and choline chloride Average of
Contrasts are: I Alfalfa each of the black locust
2,3,4 and 5 (BL diets)
58.80 f
I. 25% Alfalfa
(%)
1.79
1.79
1.20
1.20
1.20
62.43 + 0.85
64.50 f 0.85
63.64 f 0.85
62.32 f 0.85
18.56 * f 1.20 63.22 f 0.85
17.14+
18.94 f
18.38f
19.79 f I .20
* 67.76
1.7
94.7 f 3.2
94.4 * 3.2
91.2 k 3.2
100.1 it 3.2
93.0 f 3.2
by *, 2. Black locust control
* f 1.7
33.3 * 1.7
31.4*
32.4 f 1.7
30.4 f 1.7
95.9 f 3.2
(g)
gain (g) 37.0 f 1.7
Daily DM inlake
parameters
Average daily
* f 2.39 31.9
64.83 f 2.39
63.65 f 2.39
61.60 f 2.39
58.48 f 2.39
3)
Performance
(Experiment
70.33 f 2.56
P
additives
* f 1.58 62.14
74.58 * I .58
73.72 f I.58
75.33 * I .58
75.62 f I .58
84.5 I + I .58
Ca
* f 1.34 74.81
67.90 f 1.34
68.67 * 1.34
68.13 f 1.34
66.32 f I .34
75.26 f 1.34
Ash
black locusl leaf meal with various
68.80 f 0.85
DM
fed diets containing
25.78 f I .20
NDF
for rabbits
6.73 * f 1.79
8.81 ‘*f
6.91 * 1.79
8.55 “f
2.63 f 1.79
15.81 * 1.79
ADF
digeslibilities
control vs. black locust treatments (Group I vs. 2,3,4 and 5). Significant differences (P < 0.05) indicated treatments (Groups 3.4 and 5). Significant differences (P < 0.05) from Group 2 indicated by * *.
* f 1.34
’ * f 1.34
77.07 f I .34
I .34
CP
Digestibility
and % nutrienl
Dietary treatment
Table 6 Growh performance
(Group
2) vs.
3.3 * f 0.1
3.2 f 0.1
3.2 f 0.1
3.5 f 0.1
3.4 f 0.1
2.9 f 0.1
Feed gain
alfalfa black locust alfalfa black locust
Sheep Sheep Goats Goats (SE)
29.68 - 15.05 31.15 - 28.62 (*7.91) 30.42 -21.84 ’
78.44 37.56 79.22 42.60 (f3.45) 78.83 40.08 ??
ADF
Crude protein 28.94 5.81 28.83 -0.11 (k6.57) 28.89 2.85 *
NDF
62.14 45.50 61.57 43.41 ( f 3.28) 61.86 44.49
Dry matter
??
??
.0214 .0159 .0253 ’ .0201 * * ( f .0067) .0341 .0180 ’
49.89 33.04 50.84 33.05 ( f 4.76) 50.37 33.05 ’
??
Daily kg intake kg-’ BW
Ash
1838 1371 985 183
(d
Daily intake
?? ??
??
??
Contrasts are: 1. Alfalfa vs. black locust (sheep and goats). Significant differences (P < 0.05) indicated by . 2. Sheep vs. goats on black locust. Significant differences (P < 0.05) indicated by . 3. Sheep vs. goats on alfalfa. Significant differences indicated by * * .
Avg. alfalfa (sheep and goats) Avg. black locust (sheep and goats)
Diet
Species
Table I Nutrient digestibilities and average DM intake kg- ’ of body weight of alfalfa or black locust leaf diets fed to sheep and goats (means f SE) (Experiment 4)
A.C. Ayers et al./Animal
Feed Science Technology 57 (1996) 51-62
61
containing tannic acid partially alleviated the growth depression due to the tannic acid in chicks. They proposed that the methionine probably provides labile methyl groups for the production of 4-O-methyl gallate, found by Booth et al. (1959) to be the major metabolite in the urine of rats and rabbits fed tannic acid and gallic acid. 3.4. Experiment
4
There were no differences between sheep and goats in digestibility values (Table 7). The digestibilities for BL were markedly lower than for AM (Table 7). Tannins in BL are probably the causative factors. Negative values for ADF and NDF digestibilities could be due to tannin-protein complexes formed in the gut. The results are similar to those of Horton and Christensen (1981) with sheep fed either AM or BL. Proline-rich proteins (PRP) in the saliva may provide the first line of defense against tannins in the diet (Mehansho et al., 1987). Mehansho et al. (1987) found that feeding a tannin-rich diet to rats enlarged the parotid glands four-fold and increased the production of PRPs. The rats gained weight at the normal rate. According to Austin et al. (19891, the saliva of mule deer, a browser, has more PRP than the saliva of grazing animals such as cows and sheep, and also has more tannin-binding ability. We theorized that goats, being browsers, would be more equipped to tolerate the tannins in BL leaves than the sheep; however, in our study, no differences were found in the nutrient digestibilities between the two species.
4. Conclusions
Tree foliage has potential as animal feed. In our experiments, the digestibilities of protein and energy were lower for HP and BL foliage than for AM. Tannins in both species are the likely cause of lower nutrient availability, particularly for protein. In rabbits, CP and ADF digestibilities of BL were increased by dietary supplementation with PEG, suggesting a role of tannins in reducing digestibility. Digestibilities of BL leaf meal were similar in sheep and goats, and were markedly lower than for alfalfa.
References AOAC, 1984. Official Methods of Analysis (14th Ed.), Association of Official Analytical Chemists, Washington, DC. Austin, P.J., Suchar, L.A., Robbins, CT. and Hagerman, A.E., 1989. Tannin-binding proteins in saliva of deer and their absence in saliva of sheep and cattle. J. Chem. Ecol., 1.5: 1335-1347. Booth, A.N., Morse, MS., Robbins, D.J., Emerson, O.H., Jones, F.T. and Deeds, F., 1959. The metabolic fate of gallic acid and related compounds. J. Biol. Chem., 234: 30143016. Cheeke, P.R., 1992. Black locust forage as an animal feedstuff. hoc. Int. Conf. on Black Locust: Biology, Culture and Utilization. Dept. of Forestry, Michigan State University. In: Hanover, J.W. (Ed.), pp. 32. Fuller, H.L., Chang, S.I. and Potter, D.K., 1967. Detoxification of dietary tannic acid by chicks. J. Nutr., 91: 477-481. Ganido, A., Gomez-Cabrera, A., Guerrero, J.E. and van der Meer, J.M., 1991. Effects of treatment with
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polyvinylpyrrolidone and polyethylene glycol on faba bean tannins. Anim. Feed Sci. Technol., 35: 199-203. Goering, H.K. and Van Soest, P.J. 1970. Forage Fiber Analyses (apparatus, reagents, procedures, and some applications). Agric. Handbook 379. USDA, ARS, Washington, DC. Harris, D.J., Cheeke, P.R. and Patton, N.M., 1984. Evaluation of black locust leaves for growing rabbits. J. Appl. Rabbit Res., 7: 7-9. Haslam, E. 1974. Polyphenol-protein interaction. B&hem. J., 139 285-288. Horigome, T., Ohkuma, T. and Muta, M. 1984. Effect of condensed tannin of false acacia leaves on protein digestibility, as measured with rats. Jpn. J. Zootech. Sci., 55: 299-306. Horton, G.M.J. and Christensen, D.A., 1981. Nutritional value of black locust tree leaf meal (Robinia pseudoacacia) and alfalfa meal. Can. J. Anim. Sci., 61: 503-506. Kumar, R. and Horigome, T., 1986. Fractionation, characterization, and protein-precipitating capacity of the condensed tannins from Robinia pseudoacacia L. leaves. J. Agric. Food Chem., 34: 487-489. Kumar, R. and Singh, M., 1984. Tannins: their adverse role in ruminant nutrition. J. Agric. Food Chem., 32: 447-453. Mehansho, H., Butler, L.G. and Carlson, D.M., 1987. Dietary tannins and salivary proline-rich proteins: interactions, induction, and defense mechanisms. Ann. Rev. Nutr., 7: 423-440. Meyer, G.A. and Montgomery, M.E., 1987. Relationships between leaf age and the food quality of cottonwood foliage for the gypsy moth, Lyrnantria dispar. Gecologia, 72: 527-532. Myer, R.O., Combs, G.E. and Gorbet, D.W., 1986. Effect of methionine addition on the feeding value of diets containing bird-resistant grain sorghum for growing-finishing swine. Nutr. Reports Int., 33: 843-850. Nunez-Hemandez, G., Wallace, J.D., Holechek, J.L., Galyean, M.L. and Cardenas, M., 1991. Condensed tannins and nutrient utilization by lambs and goats fed low-quality diets. J. Anim. Sci., 69: 1167-1177. Oh, HI., Hoff, J.E., Armstrong, G.S. and Haff, L.A., 1980. Hydrophobic interaction in tannin-protein complexes. J. Agric. Food Chem., 28: 394-398. Palo, R.T., 1984. Distribution of birch (Betula spp.), willow (Salti spp.), and poplar (Populus spp.) secondary metabolites and their role as chemical defense against herbivores. J. Chem. Ecol., 10: 499-520. Pritchard, D.A., Stocks, D.C., O’Sullivan, B.M., Martins, P.R., Hurwood, LS. and O’Rourke, P.K., 1988. The effect of polyethylene glycol (PEG) on wool growth and live weight of sheep consuming a Mulga (Acacia aneura) diet. Proc. Aust. Sot. Anim. Prod., 17: 290-293. Raharjo, Y.C., Cheeke, P.R. and Patton, N.M., 1990. Effect of cecotrophy on the nutrient digestibility of alfalfa and black locust leaves. J. Appl. Rabbit Res., 13: 56-61. Salunkhe, D.K., Chavan, J.K. and Kadarn, S.S., 1990. Dietary Tannins: Consequences and Remedies. CRC Press, Boca Raton, FL, 200 pp. SAS, 1985. SAS User’s Guide: Statistics. SAS Inst., Inc., Cary, NC. Takada, K., Nakazato, T., Chro, K., Honda, H. and Yamane, T., 1980. Feeding value of leaf meal of acacia on poultry feed. Jpn. Poultry Sci., 17: 299-305. Waldem, D.E. 1971. A rapid micro-digestion procedure for neutral and acid detergent fiber. Can. J. Anim. Sci.. 51: 67-69.