H. C. BOHRA Division of Animal Studies Central Arid Zone Research Institute, Jodhpur ABSTRACT

Transcription

1 Annals of Arid Zone-19 (1 and 2), 73-81, Ino Nutrient utilization of ProsoPis cineraria (Khejri) leaves by desert sheep and goats H. C. BOHRA Division of Animal Studies Central Arid Zone Research Institute, Jodhpur ABSTRACT The digestibility coefficients of different cell-wall and cellular constituents. and the gross energy intake from the leaves of ProsoPis cineraria (Khejri) tree, an important top feed species of Rajasthan desert, were investigated using indigenous sheep and goats. Dry matter intake (OMI) per unit body weight was 48.9 percent higher in the goat than in the sheep. While the feed contained 14.2 percent crude protein, the per centage of digestible crude protein was only 3.1 percent and 5 5 percent in sheep and goats respectively. In sheep. the digestibi'lityof cellulosic fraction of this feed (23.2 percent) was less than half that recorded for grass (Cenchrus ci/iaris) cellulose (57.4 per cent). The observed low digestibility of the feed protein may be due. to the formation of an insoluble tannin-protein complex, which remains undi. gested in the intestine of the animals. Negative digestibilities of acid detergent fibre and lignin were recorded. probably due to the formation of an artifact in the hind gut of the animals as analysed quantitatively as lignin and which qualitatively resembled a non-conjugated phenolic lignin fraction. The digestible and metabolizable energies of the feed (kcal/g OM!) availabe to the sheep were estimated as 1.82 and 1.43 respectively. while for goats these values were 2.33 and 1.76 respectively. The dillestibility coefficients of different cell-wall constituents and proteins, and the gross energy intake were higher in the goats than in the sheep. INTRODUCTION The gross chemical composition of Prosopis cineraria, a common tree of the arid and semi-arid areas of western Rajastpan, has been reported by several workers (Sen and Ray, 1964; Ganguli el al., 1964; Mathur, 1976; Patel el a/1978; Bhandari et al., 1979). As the most important top feed for all livestock species in the desert, P. cineraria leaves deserve to be more throughly studied, than has been hitherto done, particularly with reference to the digestibility of the cell-wall constituents ~nd the digestible (DE) and metabolizable energy (ME) derived by sheep and goat when maintained on this feed. Mathur (1976) has investigated

2 74 H. C. BOHRA the availability of digestible energy (DE) of this feed to the camel, but information on other livestock species has been almost totally lacking. The present study was therefore undertaken to find the composition and digestibility of the cell-wall constituents of P. cineraria leaves, as well as the digestible and metabolizable energies available to sheep and goats when feeding on these leaves. The role of different chemical constituents of the feed in relation to the observed reduced digestibility of proteins and reduced availability of feed energy in desert adapted sheep and goats has also been examined. MATERIAL AND METHODS The study was coducted during July 1979 at Jodhpur, located in the Indian desert (29 05lN, 73 0 OllE). Four adult males, each of the Marwari breed of sheep and the Barmer breed of goats, having average body weights of 366 ± 0.31 kg and kg respectively, were selected for the study. Air dried leaves (summer lopped) of P. cineraria (approx. day matter content: 90.5 per cent) were fed to the experimental animals in metabolic stalls. The chemical composition of the feed, estimated by standard techniques, was found to be as follows: organic matter (OM) 90.8 per cent, cell-wall contituents or neutral detergent fibres (CWC or NDF) 45.5 per cent, acid detergent fibres (ADF) 28.4 per cent, hemicelluloses (HC) 17.1 per cent, celluloses 16.9 per cent tannins 11.6 per cent and silica 3.7 per cent on dry matter (OM) basis. Amongst the proximate components, crude fibres (CF), crude proteins (CP) and ether extract (EE) were found to be 18.6, 14.2 and 63 per cent respectively on OM basis. The experiment comprised a 10-day preliminary period of stall feeding on the experimental feed, followed by a 7-day collection period. During the collection period, the animals were housed individually in wooden metabolism cages. Faeces were collected in faecal collection bags (made of canvas with an inner plastic lining) harnessed to the animals. The bags were emptied twice (at 800 a.m. and 6.00 p.m.) daily. Urine from the individual animals were collected in glass bottles of 2 litres capacity, each bottle containing 2 ml of 1 N sui ph uric acid. Faeces and urine were subsampled from the 24 hr collections and analysed for different chemical constituents. Duplicate samples of feed, faeces and urine were analysed for nitrogen by the micro-kjeldahl method, and the proximate components of the feed by the approved methods of the A.O.A.C. (1965). Feed and faecal samples were analysed for NDF by the modified method of Van Soest and Wine (1967), omitting the Na2S0 3 step since sulphites reportedly remove lignin (Hartley, 1972). ADF was estimated by the method of van Soest (1963) and cellulose and silica by the method of van Soest and Wine (1968). The cell-contents and hemi-celluloses were estimated

3 NUTRIENT UTILIZATION OF PROSOPIS CiNERARIA (KHEJRI) 75 indirectly by subtracting the value of NDF from that of total dry matter and the value of ADF from tbat of NDF respectively. The tannin content of the feed was analysed by the method proposed by Burns (1971). The gross energies of the feed, faeces and urine were estimated by bomb calorimetry. Methane energy was computed following the equatiofl used by Armstrong et al. (1964). The data were statistically analysed following Snedecor and Cochran (1967). RESUL TS AND DISCUSSION The daily dry matter intake (DMO, digestibility coefficients of different cell-wall constituents and nitrogen balance in sheep and goats fed P. cinero.ria leaves have been presented in Table I. The average daily DMI per sheep and goat was found to be g and 1306 ± g respectively, the value for goat being almost double that of in the sheep. The digestible energy (DE) and metabolizable energy (ME) intakes (kcal/g DM!) were also found to be 17.0 and 21.0 per cent higher in tbe goat than in the sheep. The DMI (per 100 kg body weight) of Marwari sheep fed Cenchrus ci/iaris hay has been reported to be 2.4 ± O. I 8 kg (Bohra and Ghosh, 1977). The present study has indicated that when these sheep are fed on P. cineraria leaves, the daily DMIJI 00 kg body weight. comes to 1.9 ± 0.19 kg. P. cineraria leaves contain approximately 11.6% tannins (on dry matter basis). The astringent taste of tannins is likely to reduce feed intake (Bate-Smith, 1954). It is possible that since goats bave a higher threshold of tolerance of bitterness (Goather and Church, 1970), they are better adapted to utilise the presumably bitter leaves of P. cineraria. No significant difference in the digestibility coefficients for dry matter, organic matter and the different cell-wall constituents were observed between goats and sheep, although the digestibility of crude proteins was significantly higher in the goat than in the sheep. The digestibility coefficient for lignin and acid-detergent fibre were negative, in both the sheep and the goats, the values being more pronouik:ed in the sheep than in the goats. Similar negative results in respect of lignin and ADF digestibilities have been reported by Allison and Osbourn (1970) in sainfoin (Oonobrychis v.iciifolia) fed sheep. These authors had postulated that the nagative values for lignin, recorded in the course of th~ir studies, might have arisen due to post-ruminary formation of an artifact that analysed quantitatively as lignin and qualitatively resembled a non conjugated phenolic lignin fraction. The production of this artifact apparently disturbed fibre digestibility estimat s and might have affected DM digestibility values. Although P. cineraria leaves contain appreciable amounts of crude proteins, D.C.P. values were appreciably low, being only 3.1 and 5.5 per cent for sheep and goats respectively. On 100 gm protein intake, goates excreted 22.9 per cent less

4 76 H. C. BOHRA Table 1. Dry matter intake digestibility of nutrients and nitrogen balance in sheep and goat maintained on P. cineraria leaves Trait Sheep Animal type Goat 't' value Intake Dry matter, g/day 68S± ±1l *** Dry matter, g/kg/day 18.8± ± *** Organic matter, g/day 621.9± ± *** Digestible energy, 1.82±O ± ** kcal/g, DMI Metabolizable energy, 1.43± ± ** kcal/g, DMI Apparent digestibility (%) Dry matter 4i.4± ± (N.S,) Organic matter 42.9± ± (N.S.) Crude protein 22.0± ± Cell-wall constituents 9.8± ± (N.S.) Cell contents 67.8± ± (N.S.} Acid-detergent fiber -28.9±8; ± (N.S.} Hemicelluloses 74.2± ± (N.S.} Cellulose 23.2± ± (N.S.) Ligni ± ± (N.S.) Aitrogen balance, 2/day Nitrogen intake 15.75±O ± *U Faecal nitrogen 12.23±O ± ** Urinary nitrogen I.42±O.1l7 1.99± *" Total excretion 13.65± ± " Nitrogen balance 2.10± ± " Treatment differed significantly,.p 0.05; **p 0.01;."p 0.001

5 NUTRIENT UTILIZATION OF PROSOPIS CINERARIA (KHEJRI) 77 nitrogen through urine and faeces while retaining about 210 per cent more nitrogen than the sheep. Studies conducted on this feed by Gupta (1967) had revealed low DM digestibility, presumably due to the high tannic acid content of the leaves. The tannins combine with the feed proteins or ruminaliy formed microbial proteins and make the conjugates undegradable in the hind gut of the animal. Evidence of the formation of an insoluble nitrogen fraction, composed of undigested tannin-protein complex, has been presented by Driedger (1971). Vegetable tannins have been found to depress protein digestion by depressing the activity of the enzyme pancreatin (Driedger and Hatfield, 1972) in the hind gut of the sheep. The gross energy intake per 100 kg body weight was about 49 per cent higher in the goats than in sheep feeding on P. cineraria leaves. The percentage fosses of the gross energy intake through faeces and urine were comparatively higher in the sheep, and the overall losses through all avenues per kcal intake were comparatively lower in the goats (Table 2). The available DE and ME were higher in goats than in the sheep, which indicated that the goats are better adapted for utilizing the energy contents of the leaves of P. cineraria. Changes in the body weight and water intake of sheep and goats during the experimental period have been shown in Fig. 1. During the 17-day experimental period; the average gain in body weight was 0.5 kg in sheep and 1.4 kg in goats. The average daily water intake in sheep and goats were 5.78 percent and 4.06 per cent of their body weights respectively. Although the gross water intake by the sheep was only 42.3 per cent higher than that by the goat, water intake/kg of food intake was per cent higher in the sheep than in the goat. In other \yords, the sheep would need 2.1 times more water than the goat when feeding on P. cineraria leaves. The study reveals a paradox - that of the most abundant and nutritionally adequate top-feed of the desert region being limited in its utility because of its high tannin and lignin contents. In view of the vast potentials of this feed not only in increasing animal production in the desert in normal years, but also in sustaining livestock herds during droughts, it is important to devise ways and means of eliminating the undesirable components of this feed for optimal utilization of its protein and cellulose components by the animals. The other important fact emerging from this study is the relatively superior efficiency of the desert goat to that of desert sheep, in utilizing P. cineraria leaves despite the feed's apparent drawbacks in respect of palatability and digestibility. This explains, to some extent the phenomenal Increase

6 78 : H. C. BOHRA in the goat population of the II arid and semi- arid districts of Rajasthan over the last two decades. In comparison, the sheep population of these districts has shown only minor increases during this period. Table 2. Energy balance in adult sheep and goat~ maintained on Prosopis cineraia leaves (values are means of observations on 4 animals ±S.E.) Trait Sheep Goat '1' value Gross energy intake (kca]) ± ± *** Gross energy output in : faeces (kcal) ± ± (62.6) l53. 3) 14.69*** urine (kca!) 83.6± ± * (2.7) ( 1.2) methane (kea!) 184.7± ± ** (6.1 ) (6.7) Total energy output (kca!) ± ± (71.5) (61.3) 16.63*** Digestible energy (kcal) ± ± (41.5) (46.6) 13.38"* Metabolizable energy (kea!) 989.5± ± ** (32.6) (38.7) Values in parenthese represent the per cent of gross energy intake. Levels of significance *P<O 05; P<O.Ol: P<O.OOl, ACKNOWLEDGEMENTS I am grateful to Dr. H. S. Mann, Director and Dr. P. K. Ghosh, Head, Division of Animal Studies of this Institute, for kindly providing the necessary facilities for this work.

7 NUTRIENT UTILIZATION OF PROSOPIS CINERARIA (KHEJRI) ~ 10 "0 ~l j!:t B a: >- 6 ",8 >-m ~ ~ 4 zo <II Q..., 2 :i.:; 0 ~PRELIMINARY PERIOD COLLECTION PERIOO ~ _. ~ -... ~_ -0-' _ ] o II 9 10 II / DURATION (days) BODY WEIGHT AND WATER INTAKE IN DESERT SHEEP AND GOAT. -,. BOdy",,'., -' goof and 00- sheep~ goo' and.--0«,"'heep. Water intake.. ~ Fig. 1

8 80 B. C. HOBRA REFERENCES Allison, D. W. and Osbourn, D. F The cellulose-lignin complex in forages and its relationship to forage nutritive value. J. agric. Sci., Camb. 74: A. O. A. C Official Methods of Analysis. Association of Official Agricultural Chemists. 10th edn. Washington, D. C. Armstrong, D. G., Blaxter, K. L. and Waite, R The evaluation of artificially dried grass as a source of energy for sheep. III. The prediction of nutritive value from chemical and biological measurements. J. agric. Sri. Comb., 62: Bate-Smith, E. C Flavanoid compounds in foods. In "Advances in Food Research" V. X p. Academic Press Inc. New York. Bhandari, D. S., Govil, H. N. and Hussain, A Chemical composition and nutritive value of Khejri (Prosopis cineraria) tree leaves. Ann. Arid Zone /8: Bohra, H. C. and Ghosh, P. K Effect of restricted water intake during summer on the digestibility of cell-wall constituents, nitrogen retention and water excretion in Marwari sheep. J. agric. Sci., Comb. 89: Burns, R.E Method for estimation of tannin in grain sorghum. Agron. J. 63: Driedger. A Biological investigation of selected plant polyphenols in ruminants. Dissertation Abstracts International. S, 31: Driedger, A. and Hatfield, E.E Influence of tannins on the nutritive value of Soyabean meal for ruminants. J. Anim. Sci. 34: Ganguli, B.N., Kaul, R.N. and Nambiar, K.T.N Preliminary studies on a few top feed species. Ann. Arid Zone 3: Goather, W.D. and Church, D.C Taste responses in ruminants IV. Reaction of pygmy goat, normal goats, sheep and cattle to acetic acid and quinine hydrochloride. J. Anim. Sci. 31: , Gupta, M.L Studies on variation in nutrient content of Khejri (Prosopis spicigera) and observations of the factors affecting its nutritive value. M.V.Sci thesis, University of Udaipur, Udaipur. Hartley, R.D p-coumaric and ferulic acid components of cell wall of ryegrass and their relationship with lignin and digestibility. J. Sci. Food Agric. 23:

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