The nutritive value of
Tipuana tipu
and
Calliandra calothyrsus
as supplements to low-quality straw for goats
B.W. Norton
*, M.H. Waterfall
School of Land and Food Sciences, The University of Queensland, Brisbane, Qld 4072, Australia
Received 1 October 1999; accepted 23 March 2000
Abstract
Twenty-four Australian cashmere goats (32±40 kg live-weight (LW)), held in separate metabolism cages, were used in an experiment with a 24 factorial arrangement of treatments to study the effects of supplements of the dried leaves (browse)
from two species of fodder tree (Tipuana tipu, andCalliandra calothyrsus) at four different levels (0, 0.83, 1.66% LW and ad libitum) on voluntary intake and utilisation of a basal diet of barley straw (BS). A supplement of urea±molasses (UM) (30 g urea, 70 g molasses) was given to control goats (0% browse), and both these goats and those given browse supplements consumed BS ad libitum. The basal diet of barley straw plus UM was consumed in limited amounts (41 g/kg0.75day) and was of low DM digestibility (47±53%). At the lowest level ofTipuanasupplementation (0.83% LW, 27% DM intake), voluntary consumption of BS was signi®cantly increased above basal, resulting in a 50% increase in total intake, and 73% in digestible DM intake. WhenTipuanasupplements were increased to 1.66% LW (56% DM intake), BS intakes decreased to the same extent that the supplement increased , resulting in no further improvement in either total intake or ef®ciency of diet use. When Tipuanawas offered as the sole feed, total voluntary intake and digestible DM intake reached a maximum (66.4 and 42.0 g/ kg0.75per day, respectively), and from a consideration of all aspects of this evaluation,
Tipuana tipucompared very favourably with other high-quality browse species. However,Calliandra calothyrus proved to be of less value. The lowest level of supplementation resulted in a small increase in total (18%) and digestible DM (19%) intakes, but a decreased digestibility and availability of N for absorption and use. Further increases in supplement increased digestible intake, but N availability remained low and limiting. WhenCalliandrawas offered as the sole diet ad libitum, total and digestible DM intakes (45.6 and 21.6 g/kg0.75per day) were no better than the control (barley straw plus UM) diet (41.5 and 22.0 g/kg0.75per day) and may be
characterised as low in nutritive value and, in comparison with other browse species, of limited value as either a supplement or sole feed for ruminants in the tropics.#2000 Elsevier Science B.V. All rights reserved.
Keywords:Goats; Barley straw;Calliandra calothyrsus;Tipuana tipu; Supplementary feeding
1. Introduction
In many tropical countries, the low quality of native grasses and straws limits the productive potential of ruminant animals. Protein supplements from both plant and animal sources, and non-protein nitrogen
sources, are commonly used to improve animal per-formance on these low-quality roughages (Leibholz, 1982). There is an increasing interest in the use of both local and introduced leguminous trees and shrubs as inexpensive sources of protein for livestock feeding (Gutteridge and Shelton, 1994). The foliage of legu-minous trees is usually high in protein and minerals (Norton, 1994a), and has been used as either a supple-ment of low-quality hay and straw or as a sole source *Corresponding author.
of feed (Robertson, 1988; Norton et al., 1992; Norton, 1994b).
Calliandra calothyrsus (calliandra) is a native of Central America, but has been most commonly used for fuel and fodder in Indonesia (Palmer et al., 1994). The palatability of calliandra leaves for livestock appears variable (Arias and Macqueen, 1996; Shelton et al., 1996), and drying or wilting has been varyingly reported to either depress (Palmer and Schlink, 1992) or improve its nutritive value (Norton and Ahn, 1997). Tipuana tipu (tipuana) is another leguminous tree originating from South America, and is suited to growing in warm temperate climates. Although widely planted for its attractive appearance, it has a long growing season, tolerates frequent cutting and grazing and is palatable to grazing stock. However, its potential as a fodder tree has not been explored.
The studies reported below investigate the compara-tive value of calliandra and tipuana (browse) as sup-plements to a low quality straw, and as a sole feed.
2. Materials and methods
2.1. Experimental design and statistical analysis
The experimental design was a 24 factorial treat-ment arrangetreat-ment with three replicates per treattreat-ment. Two browse species, tipuana (Tipuana tipu) and cal-liandra (Calcal-liandra calothyrsus) were offered at four levels (0, 0.83 and 1.66% of initial live weight (LW) as supplements to chaffed barley straw offered ad libitum and as the sole diet (ad libitum). The control diet of barley straw (0% browse) was supplemented with 100 g of a 30%:70% urea:molasses mixture to provide N for ruminal fermentation. Data were analysed using the analysis of variance procedures described by Steel and Torrie (1960). The model contained the treatment effects of browse (B) type (1 df), supplement (S) level (3 df), B±S interaction (3 df) and error (15 df) to account for one missing value in the data.
2.2. Animal management and feeding procedures
Twenty-four male Australian cashmere goats (15 months old, 32±40 kg LW) were held in separate metabolism cages in a naturally lit and ventilated animal house for a trial period of 4 weeks
(Janu-ary±February) at the University of Queensland farm at Mt. Cotton in south-east Queensland. Prior to entry to the animal house, all animals had been maintained on Pangola grass (Digitaria decumbens) pastures, and during the ®rst 7 days in the animal house were offered Pangola grass hay, which was progressively substi-tuted with barley straw. In the second week, after randomly assigning animals to treatment groups, browse leaves were substituted for barley straw until the required level of supplementation was reached, after which barley straw was provided ad libitum to all except those offered the browse leaves as the sole diet. After this week of adaptation, the feeding trial lasted a further 20 days for the tipuana treatments and 16 days for the calliandra treatments. During the last 7 days of each treatment feeding period, a digestibility and N balance study was undertaken and ruminal ¯uid sam-ples collected on the last day.
Browse, which included edible leaves, shoots, twigs, stems and pods, was harvested by hand-strip-ping. Tipuana tipubrowse was harvested just before ¯owering (November) from mature trees at the Uni-versity of Queensland campus at St. Lucia.Calliandra calothyrusbrowse was harvested from young trees (3 years old) growing at Mt. Cotton research farm. Harvested browse was placed on weld-mesh ¯oors in fan-forced air drier until dry (4±5 days), then dried browse was stored in wool bales until used. Fresh samples of both species were taken at harvest and stored frozen for later analysis.
Goats offered the control (barley straw only) diet were provided with a supplement of urea-molasses (100 g/day, 30% urea, molasses 71.3% DM, 18.5% ash in DM) to provide an amount of additional dietary N equivalent to that provided by the lowest level (0.83% LW) of browse supplementation. All experi-mental diets were offered daily at 08.00, and water was freely available from automatic watering bowls. The browse supplement intakes (0.83 and 1.66% initial LW) remained constant, but the basal diet of barley straw and 100% browse treatments were offered free choice and consumed ad libitum through-out the trial.
2.3. Measurements and analytical methods
were measured weekly, and samples of each were retained for later analysis. During the last week of the trial, daily feed intakes and refusals, and faecal and urinary excretion were measured. Daily faecal outputs for each animal were weighed, sub-sampled (10%) then bulked with samples taken on previous days and stored frozen. Daily urinary excretion for each animal was collected into 50-ml glacial acetic acid, and after measuring volume, sub-sampled, bulked and stored frozen until analysed. At the end of the trial, repre-sentative samples of feed, refusal and faeces were ground (1-mm sieve), sampled and stored until ana-lysis. On the ®nal day of the digestibility trial, rumen ¯uid samples were collected from each goat by sto-mach tube immediately before, and 3 h after, feeding. Each sample was strained through nylon stocking and one portion (10 ml) mixed with an equal volume of 0.2 M HCl (for ammonia determination) and another portion (4 ml) mixed with 1 ml protein precipitant (4:1, 25% metaphosphoric acid: 2 mg/ml iso-caproic acid) for determination of volatile fatty acid (VFA) concentrations.
The DM content of barley straw, tipuana, calliandra, refusals and faeces was determined by drying in a forced-draught oven at 608C for 48 h, and the residual DM, estimated immediately prior to chemical analy-sis, was determined by drying at 1208C for 12 h in an
analytical oven. Ash was determined by incineration in a muf¯e furnace at 5008C for 4 h, neutral detergent ®bre (NDF) by the method of Van Soest and Wine (1967), acid detergent ®bre (ADF) and lignin as described by Van Soest (1963), cellulose and hemi-cellulose (Minson, 1971) and total nitrogen (N) by Kjeldahl digestion and an autoanalyser technique (Henzell et al., 1968). Ammonia in rumen ¯uid was determined by distillation and titration (Buchi Sys-tem) and the concentrations and proportions of VFA were analysed by gas±liquid chromatography (Hew-lett±Packard 5830A). The free, protein-bound and ®bre-bound tannin content of the tipuana and callian-dra were determined by modi®ed colorimetric assay (Bate-Smith, 1954) using puri®ed condensed tannin standards from Desmodium intortum (Perez-Maldo-nado and Norton, 1996).
3. Results
3.1. Chemical composition of feeds and effects of drying
Table 1 shows means values for the composition of both fresh and dried tipuana and calliandra, and for the barley straw used as the basal diet. Drying resulted in
Table 1
Mean values for the chemical composition (g/kg DM) of fresh and driedTipuana tipuandCalliandra calothyrsusand barley straw fed to Australian cashmere goats
Component Tipuana tipu Calliandra calothyrsus Barley straw (as fed)
Fresh Dried Fresh Dried
Dry matter (g/kg as fed) 903 906 901 907 914
Organic matter 934 913 964 960 905
Nitrogen 28.8 27.0 25.2 26.5 5.5
Neutral detergent fibre 337 389 305 293 779
Acid detergent fibre 312 322 245 237 466
Hemicellulose 24 60 60 51 286
Cellulose 202 201 157 151 371
Lignin 88 100 70 71 60
Condensed tannin
Free 62.7 19.9 65.2 51.2 nda
Protein-bound 5.5 14.2 7.9 10.2 nd
Fibre-bound 0.4 2.8 3.5 3.4 nd
Total 68.6 36.8 76.6 64.8 nd
small increases on N content, and apparently reduced the free and total condensed tannins in both browse samples.
3.2. Effects of browse supplements on voluntary feed intake and digestibility
Table 2 shows mean values for the intakes of straw and browse by goats offered the various treatments. Goats readily consumed all levels of browse offered, although the voluntary intake of tipuana was higher (p<0.05) than that for calliandra when both were offered as the sole feed. However, the response to supplementation was different for each browse type. At the lowest level of supplementation, tipuana
sup-plements increased (p<0.05) the basal intake of straw, and hence total intake. Thereafter, increasing tipuana depressed (p<0.05) straw intake to the same extent as browse intake was increased, and no further increases in total intake were found. When calliandra was offered at the lowest level, straw intake decreased slightly, but total DM intake increased. Further increases in cal-liandra decreased (p<0.05) straw intake, in direct compensation for browse intake, such that there was no net increase in overall feed intake by these goats. The provision of tipuana as a supplement increased (p<0.05) the overall digestibility of the mixed diet, and contrasts with the effects of calliandra supplements which had either no effect or depressed (p<0.05) digestibility (Table 3). Exceptions to this trend were Table 2
Effects of varying intakes of browse tree leaves (Tipuana tipuandCalliandra calothyrsus) on the voluntary consumption of low-quality straw by goats
Browse species Browse intake (% live-weight (LW)) Mean LW (kg) Dry matter intakea(g/kg0.75day)
Planned Actual Straw Browse Total
Tipuana 0 0 35.0 35.1 a 0 40.7 ab
0.83 0.66 39.0 45.2 b 16.6 a 61.8 b
1.66 1.38 32.7 26.2 c 33.1 b 59.3 b
Ad libitum 2.77 33.0 ± 66.4 c 66.4 b
Calliandra 0 0 32.5 35.4 a 0 41.0 ab
0.8 0.72 32.5 31.5 ac 17.1 a 48.6 ac
1.66 1.27 33.2 21.9 c 30.5 b 52.4 bc
Ad libitum 1.90 33.0 ± 45.6 d 45.6 ac
Pooled SE 2.4 0.8 2.6
aValues in columns with different letters differ signi®cantly (p<0.05). bMolasses-urea supplement was fed at 5.6 g/kg0.75per day.
Table 3
Mean values for the digestibilities (%) of dietary dry matter (DM), organic matter (OM), neutral detergent ®bre (NDF), acid detergent ®bre (ADF), cellulose and hemicellulose in goats given different supplemental levels ofTipuana tipuandCalliandra calothyrsus
Browse Browse Supplement (% LW) DM OM NDF ADF Cellulose Hemicellulose
Tipuana 0 49.0 aa 50.9 ad 46.7 a 40.3 ac 63.0 a 59.9 a
0.83 56.3 b 57.5 ab 57.7 b 50.1 a 71.4 b 68.5 b
1.66 57.9 bc 59.5 bc 52.4 ab 42.6 a 74.4 b 67.3 b
Ad libitum 63.3 c 63.8 c 37.2 c 27.3 b 84.4 c 70.4 b
Calliandra 0 53.1 ab 54.9 a 58.2 b 51.1 a 66.2 a 62.8 ab
0.83 53.8 ab 54.6 a 52.9 b 32.7 c 79.8 b 61.4 a
1.66 57.1 b 57.6 a 42.2 c 21.6 bc 84.7 b 55.8 a
Ad libitum 47.4 a 48.4 d ÿ17.8 d ÿ34.0 d 71.3 a 41.1 c
Pooled SE 2.0 2.0 3.0 3.6 2.4 2.3
the digestibilities of NDF and ADF which were pro-gressively decreased (p<0.05) with increasing intakes of browse. The negative digestibilities recorded at the higher browse intakes are thought to be artifacts of the analytical method used, and will be discussed later.
3.3. Nitrogen utilisation and live-weight changes
In diets where browse was offered, N intake and faecal N excretion increased (p<0.05) with increasing level of supplementation. However, when compared with the N intake of goats given only barley straw and urea±molasses, N intakes were only increased (p<0.05) when browse was offered ad libitum (Table 4). Goats given urea±molasses supplements had the highest N digestibility, and with only one exception, had higher urinary N excretion and N balances than all other treatments. Goats consuming tipuana ad libitum were the exception, having higher (p<0.05) N digestibilities and balances than did those in other treatments where browse was offered. In fact, increasing levels of calliandra decreased (p<0.05) N digestibility and balance, such that goats consuming calliandra ad libitum were excreting more N in urine and faeces than was being consumed in feed (negative N balance). Although the trial period was not long enough to draw ®rm conclusions about the LW changes associated with these diets, there was evi-dence that lowest levels of supplementation with both browse species would have increased weight gains
above those found for goats given the basal barley straw/urea-molasses diets. However, higher levels of supplementation were not indicated, and those fed only calliandra did little better than those given the basal diets.
3.4. Browse supplements and rumen metabolites
Table 5 shows mean values for the concentrations of volatile fatty acids (VFA) and ammonia in the ruminal ¯uid of goats offered the various treatments. There were no signi®cant differences in the concentrations of either VFA or ammonia in the rumen of goats before feeding, but there was a signi®cant rise in concentra-tions of ammonia following feeding. This was greatest for goats given the barley straw/urea±molasses diets, and least at the highest levels of calliandra feeding. The molar proportions of propionic acid and branch-chained VFA tended to be higher and acetic acid lower in goats fed tipuana compared with calliandra, but only a few of these differences were signi®cant.
4. Discussion
4.1. The nutritive value of Tipuana as a supplement and as a sole feed
Dried Tipuana tipu leaves were found to be a valuable supplement for goats, and effective in
Table 4
Mean values for the intakes, digestibility and retention of N by goats given different levels of supplementation withTipuana tipu and Calliandra calothyrus
Browse Browse
supplement (% LW)
N intake (g per day)
Faecal N (g per day)
Apparent digestibility of N (%)
N balance (g/day)
Tipuana 0 13.3 aa 3.1 a 77.2 a 1.0 ab
0.83 10.7 b 5.8 b 45.8 b 0.6 ab
1.66 14.2 c 6.8 b 52.0 c ÿ0.2 ab
Ad libitum 25.5 d 10.8 c 57.5 c 3.6 a
Calliandra 0 13.3 a 2.8 a 78.6 a 1.4 ab
0.83 8.5 e 5.8 b 31.5 d ÿ0.7 ab
1.66 13.2 a 9.0 d 31.3 d ÿ0.1 ab
Ad libitum 16.1c 13.9 e 12.8 e ÿ2.4 b
Pooled SE 0.5 0.4 1.9 1.9
increasing the intake and utilisation of a low quality straw by these animals. Supplementation at 0.8% LW (27% DM intake) increased digestible DM intake by 73% (20.1±34.8 g/kg0.75 per day) and the additional protein supplied by this supplement (44 g per day) was of greater bene®t than 10.5 g urea N provided in molasses to goats given the basal barley straw diet. The increased feed intake at this level of supplemen-tation may be the result of a greater rate of digesta passage from the rumen-associated increases in the digestibility of both cellulose and hemicellulose in the rumen. It is possible that increased intake could also be associated with improved nutrient absorption and nutritional status. The apparent decreasing digestibil-ities of NDF and ADF are possibly artifacts of the analytical system used (Van Soest et al., 1989). It is also possible that during passage through the digestive tract, condensed tannins are bound to these ®brous fractions (Carre and Brillouet, 1986), and are subse-quently included as over-estimates of true faecal NDF and ADF excreted, and underestimates of NDF and ADF digestibility (Waghorn et al., 1987; Perez-Mal-donado and Norton, 1996).
Norton et al. (1992) have investigated , in similar trials, the supplementary value ofLeucaena leucoce-phalacv. Cunningham (leucaena) and Sesbania ses-ban (sesbania), and found that when leucaena was provided at 0.8% LW, straw plus browse intakes and
diet DM digestibility were maximised (64 g/kg0.75per day, 60.5%) which compares favourably with that found for tipuana in the present experiment (61.8 g/ kg0.75 per day, 56.3%). However, higher levels of sesbania (1.66% LW) were required to achieve max-imum intake and digestibility, and its likely that the optimum levels for other browse supplements will depend on both the quality of the browse and of the basal diet offered.
Tipuana was found to be highly palatable, and despite containing comparatively high concentrations of condensed tannins (CT), appeared to contain no compounds injurious to goats. Ahn et al. (1989) have reported that fresh (freeze-dried) tipuana foliage had very low concentrations of total phenolics which were further decreased by oven-drying. In the present study, free CT concentrations in tipuana were as high as those in calliandra (63 vs. 65 g/kg), but were more signi®cantly reduced by drying than those in callian-dra (20 vs. 51 g/kg). Similar results have been reported by others where drying improved the nutritive value of calliandra (Ahn et al., 1997; Norton and Ahn, 1997). It is possible that any detrimental effects of tipuana CT may have been removed by drying, but only further feeding trials with fresh tipuana could con®rm or deny this assertion. It is also possible that compared with calliandra tannins, the tannins of tipuana have only benign effects on nutritive value. The voluntary intake Table 5
Mean values for the concentrations of ammonia (before, and after, feeding) and volatile fatty acids (3 h after feeding) in the rumen of goats supplemented with varying levels ofTipuana tipuandCalliandra calothyrsus
Browse Browse level (% LW)
Volatile fatty acidsb Ammoniab(mg N/L)
Totala
aSampled 3 h after feeding.
and DM digestibility of tipuana (66 g/kg0.75per day, 63.3%) as a sole diet compares favourably with leu-caena (53±62 g/kg0.75per day, 62±64%). However, the overall digestibility of N was low (57%) and is possibly associated with the comparatively high CT content in fresh leaves (6.8% DM). It was noted that drying caused a signi®cant reduction in CT, and further studies are needed to determine whether the CT in fresh tipuana leaves will limit its value for direct feeding to animals. It is of some importance to note that while tipuana may be of high nutritive value when fed alone to goats, it is most valuable when used as a supplement to low-quality forages. For example, a diet containing 27% dried tipuana (0.8% LW) provides similar intakes of digestible DM (35 g/kg0.75per day) to one containing 100% tipuana (42 g/kg0.75per day). It is clear that while fodder trees are often valuable sources of dietary protein and energy for livestock, the greatest nutritional and economic bene®t will ¯ow if used as a supplement to cheap low-quality hays rather than as a sole feed.
4.2. The nutritive value of Calliandra as a supplement and as a sole feed
Drying calliandra decreased the apparent contents of free and total CT as has been found by others (Ahn et al., 1989, 1997; Norton and Ahn, 1997), but there were few other effects of drying on composition. At the lowest level of supplementation (0.66% LW or 35% DM intake), total digestible DM (DDM) intake was increased by 30%, but apparently digested N (ADN) intake decreased by >50% (10.2 to 4.9 g per day), and there was no signi®cant improvement in N balance over the control treatment (straw plus urea± molasses). As the level of supplementation increased, and while straw intake decreased DDM intake was increased from 26.1 to 33.9 g/kg0.75 per day (30%), but ADN intake decreased further (4.9 to 4.1 g per day), and provided little more than maintenance N requirements for these goats. When dried calliandra was consumed ad libitum as the sole diet, DDM intake decreased to 21.6 g/kg0.75 per day (similar to straw plus urea±molasses), ADN digestibility fell to 13% and all goats were in negative N balance. There have been few studies that can be compared with these results, but DM intakes for dried calliandra fed to goats recorded in the present study (46 g/kg0.75 per
day) are similar to those reported by Palmer and Schlink, 1992) for Merino sheep offered dried callian-dra diets (37 g/kg0.75 per day). These workers also noted a signi®cant increase in intake when fresh calliandra was fed (59 g/kg0.75per day), and suggested that only fresh browse be used to determine the nutritive value of fodder tree leaves in future. How-ever, other workers have found that when fresh or dried calliandra was used as a supplement for sheep (20±25% DM intake), there were no signi®cant effects of drying on nutritive value (Robertson, 1988; Norton and Ahn, 1997). There seems to be little doubt that when compared with other fodder trees, such as Leucaena leucocephala,Sesbania sesban,Albizia chi-nensis,Tipuana tipu and some provenances of Glir-icidia sepium, Calliandra calothyrus is of very low nutritive value. This low value is related to a high CT which has a high af®nity for binding plant protein and for subsequently inhibiting protein utilisation by rumi-nant animals consuming this feed. As was noted above, urea and molasses supplements are as effective as calliandra leaves in providing N for the mainte-nance of rumen function where only low-quality feeds are available. There are possibly other provenances of Calliandra that are lower in CT and may be useful as a source of high-quality feed for ruminants in tropical areas (Palmer and Ibrahim, 1996).
5. Conclusions
Acknowledgements
The authors would like to sincerely thank all staff at the Mt. Cotton farm for their able and willing assis-tance with this trial, Mr. Michael Nielsen for his help during harvesting of the leaf and the analysis of samples and Mr Graham Kerven for advice on the analysis of condensed tannins.
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