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Evaluation of rice straw — poultry droppings based rations supplemented with graded levels of rice bran in fistulated buffaloes
ANIMAL FEED SCIENCE AND TECHNOLOGY
EJ_.SEVIER
Animal Feed Science Technology
58
(I 996) 227-237
Evaluation of rice straw - poultry droppings based rations supplemented with graded levels of rice bran in fistulated buffaloes D.V. Reddy ’ Depurtment
of Feed & Fodder
Technology.
College o;f’Vrterinury
Science, Tiruputi-517502,
India
Received 17 August 1994; accepted 23 August 1995
Abstract The effect of supplementation of deoiled rice bran (DORB) at catalytic levels of 500 (D-l), 750 (D-2), 1000 (D-3) and 1250 (D-4) g along with a caged poultry droppings (CPD)-molassesmineral mixture of 8 10 g and ad lib rice straw (0.704% nitrogen) was evaluated with four rumen fistulated graded Murrah (Bubalus bubalis) bull calves (176.5 + 0.2) in a 4 X 4 latin square design using criteria such as in sacco degradability of rice straw, voluntary dry matter (DM) intake, apparent digestibility of nutrients and rumen parameters. Rumen degradation characteristics of DM and neutral detergent fibre (NDF) of rice straw were described by fitting the data to the exponential equation P = a + b[ I - e(-c’)]. The rumen environment created by supplementation of DORB at 1000 g day-’ (D-3) to a rice straw-based diet increased (P < 0.05) the potential degradability (a + b) and rate of degradability (c) of DM and NDF of rice straw over those diets with 500 (D-l) or 750 (D-2) g day- ’ of supplementation. Supplementation of DORB up to 1000 g (D-3) along with 500 g CPD and 250 g molasses to a rice straw-mineral diet significantly increased the DM intake of basal rice straw and total feed and digestibility of DM, crude protein (CP), NDF and acid detergent fibre (ADF) (P < 0.05) and organic matter (OM) (P < 0.01). The digestible crude protein (DCP) and total digestible nutrients (TDN) of diets 1, 2, 3 and 4, respectively, were 3.37, 50.47%; 3.75, 52.49%; 4.11, 56.47% and 3.88, 56.06% which were significantly (P < 0.05) influenced by the supplementation. The rumen parameters (averages of 0, 2, 4, 6 and 8 h postfeeding) revealed that pH and ammonia nitrogen (NH,-N) of D-3 were conducive to rumen fermentative digestion of feed and total volatile fatty acid (TVFA) concentrations were positively correlated with the DM intakes of the animals. it is concluded that supplementation of DORB at 1000 g day-’ along with a poultry droppings-
’ Present address: Department of Animal Nutrition, Sciences, Kurumbapct, Pondicherry 605 009, India. 0377-840
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Rajiv
Gandhi
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of Veterinary
and Animal
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molasses-mineral
D.V. Reddy/Animal
Feed Science Technology 58 (1996) 227-237
mixture to rice straw maximizes
the utilization
of rice straw
in buffaloes and
thus paves the way to develop an economic feeding system. Keywords: Buffalo; Catalytic level; Supplementation; Rice bran; Poultry droppings; Rice straw
1. Introduction Crop residues such as rice straw and wheat straw represent a potential source of energy for ruminants in India while rice straw forms the major roughage source for feeding buffaloes and cattle in southern India. The availability of rice straw in India has been calculated to be 1.51 million metric tons based on the rice production data of the International Rice Research Institute (1993) with a straw to grain ratio of 1.36 (Reddy, 1992). One of the ways to overcome the chronic deficit of feed and fodder in India would be the effective utilization of straw by supplementation with deficient nutrients. Low levels of supplementation may have a beneficial effect on rumen fermentation, enhancing both the rate and extent of fermentation, and often increasing intake of straw (Preston and Leng, 1984). Studies conducted on the effect of supplementing graded levels of caged poultry droppings (CPD) to a rice straw-mineral diet revealed that the buffalo bull calves could not consume more than 220 g of CPD dry matter though 500 g of CPD was offered along with molasses at a ratio of 2:l @u-ushottam Reddy et al., 1996). It is imperative to improve the palatability of the CPD-molasses supplement, not only to increase the nutritive value of rice straw but also to utilize the poultry droppings as a nutrient resource in an environmentally friendly way. Deoiled rice bran, a basal energy supplement is a common household agroindustrial byproduct in southern India and it has been reported (Singh and Mehra, 1990) to have a supplementary effect at 500 g per animal per day. Hence, an attempt has been made in the present study to develop an economic feeding system by supplementation with deoiled rice bran (DORB) at catalytic levels, initially at 500 g followed by increments of 250 g to a CPD-molassesmineral mixture, for buffaloes kept on rice straw feed.
2. Materials and methods Four rumen fistulated (Bar Diamond, Inc., USA) graded Murrah (Bubalus bubafis) bull calves (176.5 f 0.2 kg body weight; about 3 years of age> in a 4 X 4 latin square switch over design (LSD) were used to evaluate the effect of supplementation of DORB at 500 (D-l), 750 (D-21, 1000 (D-3) and 1250 (D-4) g to rice straw-poultry droppings based diets. During the pre-experimental feeding period the animals were housed in sheds with cement floors and with individual feeding arrangements and during the digestion trials they were kept in specially designed metabolism stalls. Clean drinking water was provided for the animals at 09:OOh and 15:00 h. The animals were weighed at the start and end of every feeding period and the average body weights of animals were used for calculation of feed intake. The CPD-molasses-mineral mixture supplement consisted of 500 g, 250 g, 30 g and
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Feed Science Technology 58 (1996) 227-237
219
30 g of CPD, molasses, mineral mixture and salt, respectively. CPD and molasses were
mixed in a ratio of 2:l fortnightly to retain the original aroma of molasses while the other ingredients were added to it on the day of feeding. Supplemental feeds offered at 08:OO h to each animal kept on diets l-4 were 1310 g, 1560 g, 18 10 g and 2060 g, respectively. Rice straw was offered ad libitum after the consumption of supplemental feed to an extent of about 80% (between 09:30 and 10:00 h). Feeds offered and residues left over were recorded to calculate voluntary feed intake. Each period of the LSD consisted of an adjustment period of 7 days followed by 21 days for recording voluntary feed intake. In sacco polyester bag (16 X 7 cm, pore size 44 pm> studies were conducted between 18 and 21 days after which a digestion trial of 7 days duration was conducted. Rumen biochemical studies were conducted during the last 2 days succeeding the digestion trial. During the collection period, feed intakes and leftovers were measured, samples of feeds offered and residues left over were taken in separate polythene bags for each animal daily for chemical analysis. Twenty four hour collection of faeces was recorded at 08:OO h and a 2% aliquot was retained and frozen. After completion of each trial, frozen faecal samples were thawed, mixed thoroughly and subsampled for nitrogen (N) and dry matter (DM) estimation. For chemical analysis, faecal material was dried at 60°C and ground to pass through a 1 mm screen in a Wiley mill and preserved in airtight bottles. Feeds were also prepared similarly for analysis. The percentage disappearance of DM/neutral detergent fibre (NDF) of rice straw (3 g sample; ground to pass through a 2 mm screen and sieved through British Standard Sieve Mesh No. 100 to remove particles smaller than 150 pm> for different incubation periods (6, 12, 24, 48 and 72 h) was used to calculate the degradability of each nutrient at time r hours by the exponential equation p = a + b[ 1 - e’- “)I. All the polyester bags were wetted in water to prevent any lag time for microbial attachment before placing them deep in the liquid phase of the ventral sac of the rumen. About 90 cm of polypropylene thread was used so that a length of about 60 cm would be available for free movement of the bag inside the rumen. On removal from the rumen, each bag was held under running tap water to rinse off the feed particles from the outside of the bag with special attention paid to the neck of the bag. The bag material was cleaned by rubbing between the fingers and thumb until the wash water was clear. Bags were dried to a constant weight for 48 h in a forced draft oven at 60°C. The constants a, h and c were calculated by fitting a curve by eye to the data points of disappearance of DM/NDF at different incubation times (Orskov et al., 1980). Strained rumen liquor (SRL) was collected at 0, 2, 4, 6 and 8 h postfeeding (supplemental feed) through metallic probes whose multiple holes were wrapped with nylon cloth and located at four different sites in the rumen. After measuring pH with a digital pH meter, SRL samples were acidified and frozen for further analysis. Samples of feed and faeces were analysed for proximate principles (Association of Official Analytical Chemists, 1985) and cell wall constituents (Goering and Van Soest, 1970). Hemi-cellulose and cellulose were calculated as NDF - ADF and ADF - ADL, respectively. SRL was analysed for ammonia nitrogen (NH,-N) by steam distillation and total volatile fatty acids (TVFA) (Bamett and Reid, 1956) concentration. Data were analysed as per the methods described by Snedecor and Cochran (1967). The metaboliz-
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Feed Science Technology 58 (1996) 227-237
Table 1 Chemical composition (%) of feed ingredients (on DM basis except for DM) Feedstuff
DM
CP
Total ash
Acid Insoluble Ash
NDF
ADF
ADL
Hemicellulose
Cellulose
Caged poultry droppings (CPD) CPD-molasses mixture Deoiled rice bran Rice straw
88.50
19.98
33.10
11.85
51.30
31.80
9.17
19.50
22.63
81.50
15.15
25.90
8.1
34.20
21.20
6.11
13.00
15.09
91.50
12.60
11.80
7.6
52.20
24.50
5.80
27.70
18.70
90.80
4.40
12.50
10.2
83.90
52.10
6.50
31.80
45.60
Composition of mineral mixture on dry matter basis: Ca, 22%; P, 9%; NaCl, 22%; Fe, 0.6%; I, 0.1%; Cu. 0.1%; Co, 0.02%; Mn, 0.12%; Fl, not more than 0.03%.
able energy (ME) values of the diets were calculated (Ministry of Agriculture, Fisheries and Food, 1975) by the following equation ME(MJKg-‘DM)
= O.l5DOMD%
3. Results The sugarcane molasses contained 67.5% DM. The crude protein (CP), total ash and acid insoluble ash (AIA) of molasses, respectively, were 5.49%, 11.5% and 0.6% on a dry matter basis. The CPD-molasses mixture has higher CP and total ash than DORB while both have roughly similar AIA and lignin (Table 1). The rumen environment created by graded levels of DORB supplementation increased (P < 0.05) the in sacco DM and NDF disappearance of rice straw at 6, 12 and 72 h of rumen incubation (Table 2). Supplementation of DORB to a rice straw-CPDmolasses-based diet at 1000 (D-3) or 1250 (D-4) g levels significantly (P < 0.05) enhanced the soluble fraction (a), potential degradability (a + b) and rate of degradability (c) of DM and NDF of rice straw over those of D-l and D-2. The CPD-molasses-DORB-mineral mixture supplement offered under dietary treatments l-4 had average DMs of 84.27%, 85.11%, 85.71% and 86.17%, respectively. The supplements in D-l, D-2, D-3 and D-4 contained poultry droppings (CPD) to an extent of 38.17%, 32.05%, 27.62% and 24.27%, respectively. The animals kept on D-l, D-2, D-3 and D-4 consumed 832, 1171, 1522 and 1445 g of supplement dry matter (Table 3) out of 1104, 1328, 1551 and 1775 g dry matter offered to them. On calculation the CPD consumption was found to be 377 g, 441 g, 491 g and 407 g on a fresh basis, respectively, in buffalo calves kept on D-l, D-2, D-3 and D-4. Supplementation of a rice straw-based diet with DORB at 1000 (D-3) or 1250 (D-4) g significantly (P < 0.05) increased the voluntary DM intake of basal rice straw, total feed intake per day, percentage body weight or per kg metabolic body weight over that of 500 (D-l) or 750 (D-2) g of supplementation (Table 3). There was no significant difference in feed intake data of the animals fed D-3 and D-4.
Ohs
Percentage
31.29 33.1 I 35.28 36.39 I .50
60.12 64.29 69.10 69.57 1.09
component;
d d e ’ *
50.80 52.2 I 56.65 54.12 1.20
72 h
d’e’f Values in the columns bearing different superscripts differ significantly. ’ P < 0.05. CL,% loss of water-soluble component; b, % loss of water-insoluble g Represents rapidly water soluble material from polyester bags within 5 min.
16.10 17.90 24.29 24.00 0.91
36.2 I 37.19 40.21 39.20 0.91
48 h
61.12 62.14 68.21 68.69 0.92
d d e e *
Neutral detergent fibre (NDF) I 3.50 8.10 2 _ 9.68 3 _ 14.01 4 _ 13.91 SEM _ 0.41
21.10 d 21.6Od 27.80 ’ 28.10’ 0.62 *
24h
of rice straw (n = 8)
48.10 49.12 53.1 I 55.67 I .70
’ d e ’ *
6h
12h
on in sacco degradability
disappearance
11.80 12.50 16.60 16.40 0.51
Dry matter (DM) I 7.36 2 _ 3 4 SEM -
Diets
Table 2 Effect of rumen environment
d d e ’ *
d d e ’ *
c, rate constant
6.71 7.29 10.82 10.76 0.20
9.12 9.02 12.11 12.81 0.19
a
d d e e *
d d e ’ *
54.41 54.85 57.39 57.93 0.8 I
51.00 55.27 56.99 56.76 0.67
h
kinetics
for degradation
Degradation
of component
0.0246 0.0298 0.0341 0.0334 0.001
d d e e *
0.0277 d 0.0279 d 0.0321 ’ 0.03 10 e 0.002 *
c
h.
61.12 62.14 68.21 68.69 0.92
60.12 64.29 69.10 69.57 1.09
U+h
d d e e *
d d ’ e *
232 Table 3 Voluntary
D.V. Reddy /Animal Feed Science Technology 58 (1996) 227-237
feed intake and digestibility D-l
Particulars Average body weight (kg per animal) DM intake (g day- ’) Supplement Rice straw * Total * Total DM intake (g per 100 kg day-‘) * Total DM intake (g per kg W”.75 day- ‘) Digestibility DM * OM * * DOMD * CP * NDF * ADF ’
of nutrients
coefficients
in buffaloes
D-2
fed various experimental D-3
diets
D-4
SEM
176.5
176.0
176.5
177.0
832 2848 a 3680 a 2085 a
1171 2868 b 4039 b 2295 b
1522 3104b 4626 ’ 2621’
1445 3107 b 4552 ’ 2572 ’
94 120 60
76.00 a
83.59 b
95.54 c
93.80 ’
1.1
59.6 b 62.1 a.c 53.0 b 52.7 a 65.6 b 60.9 b
60.2 66.3 57.0 55.2 68.7 64.9
60.1 b 65.9 b.c 56.6 b 53.2 b 67.1 b 62.2 b
0.65 0.72 0.92 0.52 1.01 0.94
(%) 57.7 59.3 50.9 51.3 62.1 56.8
a,b.c Values in the rows bearing different * P < 0.05; ’ * P < 0.01.
a a a a a a superscripts
b b b b b ’
differ significantly.
The catalytic level of supplementation of DORB to a rice straw-based diet in buffalo bull calves significantly affected the digestibility (Table 3) of organic matter (OM) (P < O.Ol), DM, digestible organic matter in dry matter (DOMD), CP, NDF and acid detergent fibre (ADF) (P < 0.05). Digestibility of DM, DOMD and NDF were significantly (P < 0.05) higher in animals fed D-2, D-3 and D-4 than in those fed D-l. There was no significant difference in digestibility of DM, DOMD and NDF of diets 2, 3 and 4. Crude protein digestibility of D-3 and D-4 was significantly (P < 0.05) higher than that of D-l or D-2. No significant difference was observed in CP digestibility of D-3 and D-4 or D-l and D-2. Digestibility of ADF was highest for diet 3 and least for diet 1, while the values for diet 2 and diet 4 were not significantly different. The digestible crude protein (DCP) and total digestible nutrients (TDN) of the diets (Table 4) 1, 2, 3 and 4, respectively, were 3.37 and 50.47%, 3.75 and 52.49%, 4.11 and 56.47% and 3.88 and 56.06% which were significantly (P < 0.05) influenced by the supplementation. The animals kept on D-3 and D-4 consumed significantly (P < 0.05) higher DCP and TDN than those kept on D-l while the values for D-2 were intermediate. Rumen parameters such as pH and ammonia nitrogen (P < 0.05) and TVFA (P < 0.01) were significantly influenced by the level of DORB supplementation (Table 4). DORB supplementation depressed the rumen pH while ammonia nitrogen (NH,-N) and TVFA were increased. There was no significant difference in the NH,-N and TVFA
D.V. Reddy/Animul
Feed Science Technology 58 (1996) 227-237
233
Table 4 The effect of supplementing graded levels of DORB on nutritive value, nutrient intake and rumen fermentation in buffalo calves D-2
D-l
Particulars
D-4
D-3
SEM
DM intake (g day- ’)
3680 a
4039 b
4626 ’
4552 c
120
Nutritive value CP (g kg- ’ DM) DCP * (g kg- ’ DM) TDN * (g kg- ’ DM) ME (MJ kg- r DM)
65.8 33.7 a 504.7 a 7.64
71.3 37.5 b 524.9 a 7.94
74.4 41.1 c 564.7 b 8.54
72.9 38.8 b 560.6 b 8.48
_ 1.1 10.1 _
Nutrient intake CP intake (g day
’)
DCP intake (g day _ ’) * TDN intake (g day-‘) * ME intake (MJ day _ ’) N intake (g day- ’) DOM intake (g day- ’) N/DOM
242
288
344
332
_
124a 1857 a 28.12 38.72 1873 0.021
151 b 2120 b 32.07 46.08 2139 0.022
190c 2612’ 39.51 55.04 2620 0.021
177 c 2552 ’ 38.60 53.12 2571 0.021
2.5 72 _ _ _ _
6.68 b 8.61 a.b 152.59 b
6.70 a.b 9.35 b 150.68 b
0.02 0.40 1.98
Rumen parameters (averages of 0, 2,4,6 and 8 h collection data) pH of SRL * 6.73 a 6.73 a NH,-N (mg dl-’ SRL) * 7.75 a 8.74 ab 111.11 a 119.97 a TVFA (mequiv. l- ’SRL) * *
“bx Values in the rows bearing different superscripts differ significantly. * P < 0.05; * * P < 0.01.
concentration of SRL of animals fed diets 3 and 4 while animals kept on diet 2 had an apparently higher concentration compared with diet 1.
4. Discussion Supplementation of straw with nitrogen (N) is known to improve feed intake by increasing the supply of N to micro-organisms in the rumen. Caged poultry droppings are comprised of proteins (dietary, micro-organisms) as well as non-protein nitrogenous compounds (ammonia, uric acid) which can be utilized by rumen micro-organisms for their own synthesis. The resultant increased microbial population increases the rate of digesta breakdown and passage of the digesta leading to proportionate improvement in feed intake (Van Soest, 1982). DORB supplementation up to 1000 g (D-3) of a poultry droppings-molasses-mineral supplement was associated with significantly (P < 0.05) higher potential degradability (a + b) and rate constant (c) of DM and NDF of rice straw (Table 2) which were reflective of higher DM and NDF losses than 500 g (D-l) and 750 g (D-2) of supplementation. It is possible that the 1000 g of DORB might have contributed sufficient fermentable energy to the rumen in the form of available cellulose and hemi-cellulose, which are known to stimulate fibre digestion (Silva and Orskov, 1988) apart from its contribution of amino acid-N which is required for microbial growth (Maeng et al., 1976) in addition to non-protein-nitrogen.
234
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Feed Science Technology 58 (1996) 227-237
The improvement in poultry droppings consumption to 491 g in animals kept on diet 3 over that (220 g) reported by Purushottam Reddy et al. (1996) was possibly due to the addition of DORB and a level of 1000 g rice bran (D-3) was found to be optimum to improve palatability of the supplemental feed. Supplementation of DORB at greater than the 500 g (D-l) level to a rice straw diet effected improvements of 0.07% (D-2) and 9.0% (D-3 and D-4) in intake of the rice straw DM and 9.8% (D-21, 25.7% (D-3) and 23.7% (D-4) in intake of the total diet DM. This indicates that DORB acted as a true supplement and there was no additional benefit beyond the 1000 g level (D-3). The major determinant of the apparent digestibility of a diet is its apparent digestibility in the rumen. The level of DORB supplementation positively correlated with the in sacco degradability of rice straw, the correlation coefficients being 0.96 and 0.82, respectively, for (a + b) and c of dry matter. The high correlation between voluntary feed intake (VFI) and its overall apparent digestibility (Blaxter et al., 1961) is thus largely due to correlation of VFI with apparent digestibility of feed in the rumen (Ulyatt et al., 1967). The results of the present work conform with those of Ulyatt et al. (1967). Supplementation of a rice straw-based diet with greater than 750 g DORB (diets 2-4) effected a significant (P < 0.05) improvement in digestibility of DM, DOMD, NDF and ADF while in the case of OM (P < 0.01) and CP (P < 0.05) a level of 1000 g DORB produced improvement (Table 3). It is possible that by offering a DORB-CPD molasses supplement prior to feeding basal rice straw, a greater degree of colonization of the straw may occur, not only by bacteria, but also by rumen fungi (Bauchop, 1981) which have been implicated in fibre breakdown. The animals on diets 1, 2, 3 and 4, respectively, consumed 242 g, 288 g, 344 g and 332 g of crude protein daily (Table 4). O’Donovan et al. (1983) reported that adequate amounts of supplements rich in rapidly rumen-degradable N increased the intake of low-quality mature grass hay due to stimulation of the rate of breakdown of cell walls in the rumen (Campling et al., 1962). Rumen-degradable protein (RDP) needed for optimal rumen microbial activity and microbial protein production is dependent on the overall energy intake. The requirement (RDP = 7.8 X ME intake, MJ; Agricultural Research Council, 1980) of RDP for animals kept on diets 1, 2, 3 and 4 was 219 g, 250 g, 308 g and 301 g, respectively, which indicates that diets provided the required RDP assuming all the CP consumed is rumen degradable. The feed intake and digestibility of nutrients of the present study are in close agreement with the findings of O’Donovan et al. (1983) and Campling et al. (1962). The ratio N/digestible organic matter (N/DOM) for the experimental diets (Table 4) was 0.021-0.022 while the optimum should be 0.032 g N g-’ DOM (Agricultural Research Council, 1980). The nutritive requirements (Kearl, 1982) of buffalo calves weighing 200 kg with daily growth of 250 g are 4.8 kg DM intake, 2.53 kg TDN intake and 281 g DCP intake. The availability of nutrients for different treatments (Table 4) indicates that diet 3 could provide the required DM and TDN intake but less than the required DCP intake. There was a significant (P < 0.05) reduction in pH of strained rumen liquor (SRL) due to graded levels of DORB supplementation from 500 to 1250 g (Table 4). The lowering of pH after feeding (Fig. 1) could be related to increased total volatile fatty acid (TVFA) concentration in the rumen liquor upon feed intake since they are inversely
D.V. Reddy/Animal
Feed Science Technology
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1
641 0
TItiiE
-
D-l
+
D-2
+
215
58 (1996) 227-237
I 8
(h) cl-3
-a-
D-4
Fig. 1. pH of SRL with time after feeding.
6
2
0
TI$E
-
D-l
+
D-2
+
D-3
8
(h) -8-D-4
Fig. 2. NH, -N of SRL with time after feeding.
correlated. Perusal of pH values indicates that the pH is optimum for cellulolytic bacteria (Orskov, 1982). Supplementation of graded levels of DORB enhanced (P < 0.05) the ammonia nitrogen (NH,-N) concentration in SRL proportionately (Fig. 2; Table 4). This increase in NH,-N concentration in SRL of animals fed diets 2, 3 and 4 might possibly be related to the relative consumption of CPD. Increased feed intake with graded levels of DORB supplementation enhanced (P < 0.01) the TVFA concentrations (Fig. 3; Table 4). Th’IS is in accordance with that increased TVFA production associated with increased energy intake (Chaturvedi et al., 1974). 5. Conclusion Voluntary feed intake, in sacco rumen degradability of rice straw, in vivo digestibility of nutrients and rumen parameters for different diets show that daily supplementation of
236
D.V. Reddy/Animal
Feed Science Technology 58 (1996) 227-237
2
0
6 TI&
-
D-l
+
D-2
6
(h) +
D-3
-s-
D-4
Fig. 3. TVFA of SRL with time after feeding.
DORB at the 1000 g (D-3) level along with CPD-molasses-mineral mixture has been found to be optimum to maximize the utilization of rice straw in buffaloes. Further, a need for supplementation of protein meals was felt to overcome the protein insufficiency.
Acknowledgements The author wishes to acknowledge financial support from the International Foundation for Science, Sweden (Grant No. B/1792-1).
References Agricultural Research Council, 1980. The Nutrient Requirements of Ruminant livestock. Commonwealth Agricultural Bureau, Farnham Royal. Association of Official Analytical Chemists, 1985. Ofticial Methods of Analysis, 14th edn. Association of Official Analytical Chemists, Washington, DC. Bamett, A.J.G. and Reid, R.L., 1956. Studies on the production of volatile fatty acids from the grass by rumen liquor in an artificial rumen. 1. Volatile fatty acid production from grass. J. Agric. Sci., 48: 315-321. Bauchop, T., 1981. The role of anaerobic fungi in mmen tibre digestion. Agric. Environ., 6: 333-348. Blaxter, K.L., Wainman, F.W. and Wilson, R.S., 1961. The regulation of food intake by sheep. Anim. Prod., 3: 51-61. Campling, R.C., Freer, M. and Balch, C.C., 1962. Factors affecting the voluntary intake of food by cows. 3. The effect of urea on the voluntary intake of oat straw. Br. J. Nutr., 16: 115- 124. Chaturvedi, M.L., Singh, U.B. and Ranjhan, S.K. 1974. Correlation between volatile fatty acid production and availability of digestible and metabolizable energy to the growing cattle and buffaloes. Indian J. Anim. Sci., 44: 293-296. Goering, H.K. and van Soest, P.J., 1970. Forage tibre analysis (apparatus, reagents, procedures and some applications). ARS, USDA Agriculture Hand Book No. 379, Washington, DC. International Rice Research Institute, 1993. Rice Facts. International Rice Research Institute, Manila, Philippines.
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Kearl, L.C., 1982. Nutrient Requirements of Ruminants in Developing Countries. International Feedstuffs Institute, Utah Agricultural Experiment Station, Utah State University, Logan, UT. Maeng, W.J., van Nevel, C.J., Baldwin, R.L. and Morris, J.G., 1976. Rumen microbial growth rates and yields: Effect of amino acids and protection. J. Dairy Sci., 59: 68-78. Ministry of Agriculture, Fisheries and Food, 1975. Tech. Bull. No. 33, Energy Allowances and Feeding Systems for Ruminants. Her Majesty’s Stationary Office, London. O’Donovan, P.B., Silva, J.M. and Euclides, V.P.B., 1983. Beef production from native and improved grasslands in West-Central Brazil - nutritional considerations. World Anim. Rev., 47: 30-37. Orskov, E.R., 1982. Protein Nutrition in Ruminants. Academic, New York. Orskov, E.R., Hovel, F.D. and Mould, F., 1980. The use of nylon bag technique for evaluation of feedstuffs. Trop. Anim. Prod., 5: 195-213. Preston, T.R. and Leng, R.A., 1984. Supplementation of diets based on fibrous residues and byproducts. In: F. Sundstol and E. Owen (Editors), Straw and Other Fibrous By-products as Feed. Elsevier Science, Amsterdam, pp. 373-430. Purushottam Reddy, G., Reddy, K.V.S. and Reddy, D.V., 1996. Effect of supplementing graded levels of poultry droppings on nutrient digestibility and rumen fermentation pattern in buffaloes fed with rice straw. Buffalo J., in press. Reddy, D.V., 1992. Development of package of practices using crop byproducts based rations under Integrated Farming Systems. Annual Report (1992-93), Regional Agricultural Research Station, APAU, Tirupati, pp. 88- 100. Silva, A.T. and Orskov, E.R., 1988. The effect of five different supplements on the degradation of straw in sheep given untreated barley straw. Anim. Feed Sci. Technol., 19: 289-298. Singh, U.B. and Mehra, U.R., 1990. Utilization of ammoniated wheat straw given in a feed block and supplemented with varying quantities of fish meal and oil extracted rice bran. Anim. Feed Sci. Technol., 28: 129-130. Snedecor, G.W. and Cochran, W.G., 1967. Statistical Methods, 6th edn. Oxford and IBH, Calcutta. Ulyatt, M.J., Blaxter, K.L. and McDonald, J., 1967. The relationship between the apparent digestibility of roughages in the rumen and lower gut of sheep, the volume of fluid in the rumen and voluntary feed intake. Anim. Prod., 9: 463-470. Van Soest, P.J., 1982. Nutritional Ecology of the Ruminants. 0 and B Books Inc., Corvallis, OR.
EJ_.SEVIER
Animal Feed Science Technology
58
(I 996) 227-237
Evaluation of rice straw - poultry droppings based rations supplemented with graded levels of rice bran in fistulated buffaloes D.V. Reddy ’ Depurtment
of Feed & Fodder
Technology.
College o;f’Vrterinury
Science, Tiruputi-517502,
India
Received 17 August 1994; accepted 23 August 1995
Abstract The effect of supplementation of deoiled rice bran (DORB) at catalytic levels of 500 (D-l), 750 (D-2), 1000 (D-3) and 1250 (D-4) g along with a caged poultry droppings (CPD)-molassesmineral mixture of 8 10 g and ad lib rice straw (0.704% nitrogen) was evaluated with four rumen fistulated graded Murrah (Bubalus bubalis) bull calves (176.5 + 0.2) in a 4 X 4 latin square design using criteria such as in sacco degradability of rice straw, voluntary dry matter (DM) intake, apparent digestibility of nutrients and rumen parameters. Rumen degradation characteristics of DM and neutral detergent fibre (NDF) of rice straw were described by fitting the data to the exponential equation P = a + b[ I - e(-c’)]. The rumen environment created by supplementation of DORB at 1000 g day-’ (D-3) to a rice straw-based diet increased (P < 0.05) the potential degradability (a + b) and rate of degradability (c) of DM and NDF of rice straw over those diets with 500 (D-l) or 750 (D-2) g day- ’ of supplementation. Supplementation of DORB up to 1000 g (D-3) along with 500 g CPD and 250 g molasses to a rice straw-mineral diet significantly increased the DM intake of basal rice straw and total feed and digestibility of DM, crude protein (CP), NDF and acid detergent fibre (ADF) (P < 0.05) and organic matter (OM) (P < 0.01). The digestible crude protein (DCP) and total digestible nutrients (TDN) of diets 1, 2, 3 and 4, respectively, were 3.37, 50.47%; 3.75, 52.49%; 4.11, 56.47% and 3.88, 56.06% which were significantly (P < 0.05) influenced by the supplementation. The rumen parameters (averages of 0, 2, 4, 6 and 8 h postfeeding) revealed that pH and ammonia nitrogen (NH,-N) of D-3 were conducive to rumen fermentative digestion of feed and total volatile fatty acid (TVFA) concentrations were positively correlated with the DM intakes of the animals. it is concluded that supplementation of DORB at 1000 g day-’ along with a poultry droppings-
’ Present address: Department of Animal Nutrition, Sciences, Kurumbapct, Pondicherry 605 009, India. 0377-840
I /96/$15.00
SSDf 0377-840
Rajiv
Gandhi
0 I996 Elsevier Science B.V. All rights reserved 1(95)00902-7
College
of Veterinary
and Animal
228
molasses-mineral
D.V. Reddy/Animal
Feed Science Technology 58 (1996) 227-237
mixture to rice straw maximizes
the utilization
of rice straw
in buffaloes and
thus paves the way to develop an economic feeding system. Keywords: Buffalo; Catalytic level; Supplementation; Rice bran; Poultry droppings; Rice straw
1. Introduction Crop residues such as rice straw and wheat straw represent a potential source of energy for ruminants in India while rice straw forms the major roughage source for feeding buffaloes and cattle in southern India. The availability of rice straw in India has been calculated to be 1.51 million metric tons based on the rice production data of the International Rice Research Institute (1993) with a straw to grain ratio of 1.36 (Reddy, 1992). One of the ways to overcome the chronic deficit of feed and fodder in India would be the effective utilization of straw by supplementation with deficient nutrients. Low levels of supplementation may have a beneficial effect on rumen fermentation, enhancing both the rate and extent of fermentation, and often increasing intake of straw (Preston and Leng, 1984). Studies conducted on the effect of supplementing graded levels of caged poultry droppings (CPD) to a rice straw-mineral diet revealed that the buffalo bull calves could not consume more than 220 g of CPD dry matter though 500 g of CPD was offered along with molasses at a ratio of 2:l @u-ushottam Reddy et al., 1996). It is imperative to improve the palatability of the CPD-molasses supplement, not only to increase the nutritive value of rice straw but also to utilize the poultry droppings as a nutrient resource in an environmentally friendly way. Deoiled rice bran, a basal energy supplement is a common household agroindustrial byproduct in southern India and it has been reported (Singh and Mehra, 1990) to have a supplementary effect at 500 g per animal per day. Hence, an attempt has been made in the present study to develop an economic feeding system by supplementation with deoiled rice bran (DORB) at catalytic levels, initially at 500 g followed by increments of 250 g to a CPD-molassesmineral mixture, for buffaloes kept on rice straw feed.
2. Materials and methods Four rumen fistulated (Bar Diamond, Inc., USA) graded Murrah (Bubalus bubafis) bull calves (176.5 f 0.2 kg body weight; about 3 years of age> in a 4 X 4 latin square switch over design (LSD) were used to evaluate the effect of supplementation of DORB at 500 (D-l), 750 (D-21, 1000 (D-3) and 1250 (D-4) g to rice straw-poultry droppings based diets. During the pre-experimental feeding period the animals were housed in sheds with cement floors and with individual feeding arrangements and during the digestion trials they were kept in specially designed metabolism stalls. Clean drinking water was provided for the animals at 09:OOh and 15:00 h. The animals were weighed at the start and end of every feeding period and the average body weights of animals were used for calculation of feed intake. The CPD-molasses-mineral mixture supplement consisted of 500 g, 250 g, 30 g and
D.V. Reddy/Animul
Feed Science Technology 58 (1996) 227-237
219
30 g of CPD, molasses, mineral mixture and salt, respectively. CPD and molasses were
mixed in a ratio of 2:l fortnightly to retain the original aroma of molasses while the other ingredients were added to it on the day of feeding. Supplemental feeds offered at 08:OO h to each animal kept on diets l-4 were 1310 g, 1560 g, 18 10 g and 2060 g, respectively. Rice straw was offered ad libitum after the consumption of supplemental feed to an extent of about 80% (between 09:30 and 10:00 h). Feeds offered and residues left over were recorded to calculate voluntary feed intake. Each period of the LSD consisted of an adjustment period of 7 days followed by 21 days for recording voluntary feed intake. In sacco polyester bag (16 X 7 cm, pore size 44 pm> studies were conducted between 18 and 21 days after which a digestion trial of 7 days duration was conducted. Rumen biochemical studies were conducted during the last 2 days succeeding the digestion trial. During the collection period, feed intakes and leftovers were measured, samples of feeds offered and residues left over were taken in separate polythene bags for each animal daily for chemical analysis. Twenty four hour collection of faeces was recorded at 08:OO h and a 2% aliquot was retained and frozen. After completion of each trial, frozen faecal samples were thawed, mixed thoroughly and subsampled for nitrogen (N) and dry matter (DM) estimation. For chemical analysis, faecal material was dried at 60°C and ground to pass through a 1 mm screen in a Wiley mill and preserved in airtight bottles. Feeds were also prepared similarly for analysis. The percentage disappearance of DM/neutral detergent fibre (NDF) of rice straw (3 g sample; ground to pass through a 2 mm screen and sieved through British Standard Sieve Mesh No. 100 to remove particles smaller than 150 pm> for different incubation periods (6, 12, 24, 48 and 72 h) was used to calculate the degradability of each nutrient at time r hours by the exponential equation p = a + b[ 1 - e’- “)I. All the polyester bags were wetted in water to prevent any lag time for microbial attachment before placing them deep in the liquid phase of the ventral sac of the rumen. About 90 cm of polypropylene thread was used so that a length of about 60 cm would be available for free movement of the bag inside the rumen. On removal from the rumen, each bag was held under running tap water to rinse off the feed particles from the outside of the bag with special attention paid to the neck of the bag. The bag material was cleaned by rubbing between the fingers and thumb until the wash water was clear. Bags were dried to a constant weight for 48 h in a forced draft oven at 60°C. The constants a, h and c were calculated by fitting a curve by eye to the data points of disappearance of DM/NDF at different incubation times (Orskov et al., 1980). Strained rumen liquor (SRL) was collected at 0, 2, 4, 6 and 8 h postfeeding (supplemental feed) through metallic probes whose multiple holes were wrapped with nylon cloth and located at four different sites in the rumen. After measuring pH with a digital pH meter, SRL samples were acidified and frozen for further analysis. Samples of feed and faeces were analysed for proximate principles (Association of Official Analytical Chemists, 1985) and cell wall constituents (Goering and Van Soest, 1970). Hemi-cellulose and cellulose were calculated as NDF - ADF and ADF - ADL, respectively. SRL was analysed for ammonia nitrogen (NH,-N) by steam distillation and total volatile fatty acids (TVFA) (Bamett and Reid, 1956) concentration. Data were analysed as per the methods described by Snedecor and Cochran (1967). The metaboliz-
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Feed Science Technology 58 (1996) 227-237
Table 1 Chemical composition (%) of feed ingredients (on DM basis except for DM) Feedstuff
DM
CP
Total ash
Acid Insoluble Ash
NDF
ADF
ADL
Hemicellulose
Cellulose
Caged poultry droppings (CPD) CPD-molasses mixture Deoiled rice bran Rice straw
88.50
19.98
33.10
11.85
51.30
31.80
9.17
19.50
22.63
81.50
15.15
25.90
8.1
34.20
21.20
6.11
13.00
15.09
91.50
12.60
11.80
7.6
52.20
24.50
5.80
27.70
18.70
90.80
4.40
12.50
10.2
83.90
52.10
6.50
31.80
45.60
Composition of mineral mixture on dry matter basis: Ca, 22%; P, 9%; NaCl, 22%; Fe, 0.6%; I, 0.1%; Cu. 0.1%; Co, 0.02%; Mn, 0.12%; Fl, not more than 0.03%.
able energy (ME) values of the diets were calculated (Ministry of Agriculture, Fisheries and Food, 1975) by the following equation ME(MJKg-‘DM)
= O.l5DOMD%
3. Results The sugarcane molasses contained 67.5% DM. The crude protein (CP), total ash and acid insoluble ash (AIA) of molasses, respectively, were 5.49%, 11.5% and 0.6% on a dry matter basis. The CPD-molasses mixture has higher CP and total ash than DORB while both have roughly similar AIA and lignin (Table 1). The rumen environment created by graded levels of DORB supplementation increased (P < 0.05) the in sacco DM and NDF disappearance of rice straw at 6, 12 and 72 h of rumen incubation (Table 2). Supplementation of DORB to a rice straw-CPDmolasses-based diet at 1000 (D-3) or 1250 (D-4) g levels significantly (P < 0.05) enhanced the soluble fraction (a), potential degradability (a + b) and rate of degradability (c) of DM and NDF of rice straw over those of D-l and D-2. The CPD-molasses-DORB-mineral mixture supplement offered under dietary treatments l-4 had average DMs of 84.27%, 85.11%, 85.71% and 86.17%, respectively. The supplements in D-l, D-2, D-3 and D-4 contained poultry droppings (CPD) to an extent of 38.17%, 32.05%, 27.62% and 24.27%, respectively. The animals kept on D-l, D-2, D-3 and D-4 consumed 832, 1171, 1522 and 1445 g of supplement dry matter (Table 3) out of 1104, 1328, 1551 and 1775 g dry matter offered to them. On calculation the CPD consumption was found to be 377 g, 441 g, 491 g and 407 g on a fresh basis, respectively, in buffalo calves kept on D-l, D-2, D-3 and D-4. Supplementation of a rice straw-based diet with DORB at 1000 (D-3) or 1250 (D-4) g significantly (P < 0.05) increased the voluntary DM intake of basal rice straw, total feed intake per day, percentage body weight or per kg metabolic body weight over that of 500 (D-l) or 750 (D-2) g of supplementation (Table 3). There was no significant difference in feed intake data of the animals fed D-3 and D-4.
Ohs
Percentage
31.29 33.1 I 35.28 36.39 I .50
60.12 64.29 69.10 69.57 1.09
component;
d d e ’ *
50.80 52.2 I 56.65 54.12 1.20
72 h
d’e’f Values in the columns bearing different superscripts differ significantly. ’ P < 0.05. CL,% loss of water-soluble component; b, % loss of water-insoluble g Represents rapidly water soluble material from polyester bags within 5 min.
16.10 17.90 24.29 24.00 0.91
36.2 I 37.19 40.21 39.20 0.91
48 h
61.12 62.14 68.21 68.69 0.92
d d e e *
Neutral detergent fibre (NDF) I 3.50 8.10 2 _ 9.68 3 _ 14.01 4 _ 13.91 SEM _ 0.41
21.10 d 21.6Od 27.80 ’ 28.10’ 0.62 *
24h
of rice straw (n = 8)
48.10 49.12 53.1 I 55.67 I .70
’ d e ’ *
6h
12h
on in sacco degradability
disappearance
11.80 12.50 16.60 16.40 0.51
Dry matter (DM) I 7.36 2 _ 3 4 SEM -
Diets
Table 2 Effect of rumen environment
d d e ’ *
d d e ’ *
c, rate constant
6.71 7.29 10.82 10.76 0.20
9.12 9.02 12.11 12.81 0.19
a
d d e e *
d d e ’ *
54.41 54.85 57.39 57.93 0.8 I
51.00 55.27 56.99 56.76 0.67
h
kinetics
for degradation
Degradation
of component
0.0246 0.0298 0.0341 0.0334 0.001
d d e e *
0.0277 d 0.0279 d 0.0321 ’ 0.03 10 e 0.002 *
c
h.
61.12 62.14 68.21 68.69 0.92
60.12 64.29 69.10 69.57 1.09
U+h
d d e e *
d d ’ e *
232 Table 3 Voluntary
D.V. Reddy /Animal Feed Science Technology 58 (1996) 227-237
feed intake and digestibility D-l
Particulars Average body weight (kg per animal) DM intake (g day- ’) Supplement Rice straw * Total * Total DM intake (g per 100 kg day-‘) * Total DM intake (g per kg W”.75 day- ‘) Digestibility DM * OM * * DOMD * CP * NDF * ADF ’
of nutrients
coefficients
in buffaloes
D-2
fed various experimental D-3
diets
D-4
SEM
176.5
176.0
176.5
177.0
832 2848 a 3680 a 2085 a
1171 2868 b 4039 b 2295 b
1522 3104b 4626 ’ 2621’
1445 3107 b 4552 ’ 2572 ’
94 120 60
76.00 a
83.59 b
95.54 c
93.80 ’
1.1
59.6 b 62.1 a.c 53.0 b 52.7 a 65.6 b 60.9 b
60.2 66.3 57.0 55.2 68.7 64.9
60.1 b 65.9 b.c 56.6 b 53.2 b 67.1 b 62.2 b
0.65 0.72 0.92 0.52 1.01 0.94
(%) 57.7 59.3 50.9 51.3 62.1 56.8
a,b.c Values in the rows bearing different * P < 0.05; ’ * P < 0.01.
a a a a a a superscripts
b b b b b ’
differ significantly.
The catalytic level of supplementation of DORB to a rice straw-based diet in buffalo bull calves significantly affected the digestibility (Table 3) of organic matter (OM) (P < O.Ol), DM, digestible organic matter in dry matter (DOMD), CP, NDF and acid detergent fibre (ADF) (P < 0.05). Digestibility of DM, DOMD and NDF were significantly (P < 0.05) higher in animals fed D-2, D-3 and D-4 than in those fed D-l. There was no significant difference in digestibility of DM, DOMD and NDF of diets 2, 3 and 4. Crude protein digestibility of D-3 and D-4 was significantly (P < 0.05) higher than that of D-l or D-2. No significant difference was observed in CP digestibility of D-3 and D-4 or D-l and D-2. Digestibility of ADF was highest for diet 3 and least for diet 1, while the values for diet 2 and diet 4 were not significantly different. The digestible crude protein (DCP) and total digestible nutrients (TDN) of the diets (Table 4) 1, 2, 3 and 4, respectively, were 3.37 and 50.47%, 3.75 and 52.49%, 4.11 and 56.47% and 3.88 and 56.06% which were significantly (P < 0.05) influenced by the supplementation. The animals kept on D-3 and D-4 consumed significantly (P < 0.05) higher DCP and TDN than those kept on D-l while the values for D-2 were intermediate. Rumen parameters such as pH and ammonia nitrogen (P < 0.05) and TVFA (P < 0.01) were significantly influenced by the level of DORB supplementation (Table 4). DORB supplementation depressed the rumen pH while ammonia nitrogen (NH,-N) and TVFA were increased. There was no significant difference in the NH,-N and TVFA
D.V. Reddy/Animul
Feed Science Technology 58 (1996) 227-237
233
Table 4 The effect of supplementing graded levels of DORB on nutritive value, nutrient intake and rumen fermentation in buffalo calves D-2
D-l
Particulars
D-4
D-3
SEM
DM intake (g day- ’)
3680 a
4039 b
4626 ’
4552 c
120
Nutritive value CP (g kg- ’ DM) DCP * (g kg- ’ DM) TDN * (g kg- ’ DM) ME (MJ kg- r DM)
65.8 33.7 a 504.7 a 7.64
71.3 37.5 b 524.9 a 7.94
74.4 41.1 c 564.7 b 8.54
72.9 38.8 b 560.6 b 8.48
_ 1.1 10.1 _
Nutrient intake CP intake (g day
’)
DCP intake (g day _ ’) * TDN intake (g day-‘) * ME intake (MJ day _ ’) N intake (g day- ’) DOM intake (g day- ’) N/DOM
242
288
344
332
_
124a 1857 a 28.12 38.72 1873 0.021
151 b 2120 b 32.07 46.08 2139 0.022
190c 2612’ 39.51 55.04 2620 0.021
177 c 2552 ’ 38.60 53.12 2571 0.021
2.5 72 _ _ _ _
6.68 b 8.61 a.b 152.59 b
6.70 a.b 9.35 b 150.68 b
0.02 0.40 1.98
Rumen parameters (averages of 0, 2,4,6 and 8 h collection data) pH of SRL * 6.73 a 6.73 a NH,-N (mg dl-’ SRL) * 7.75 a 8.74 ab 111.11 a 119.97 a TVFA (mequiv. l- ’SRL) * *
“bx Values in the rows bearing different superscripts differ significantly. * P < 0.05; * * P < 0.01.
concentration of SRL of animals fed diets 3 and 4 while animals kept on diet 2 had an apparently higher concentration compared with diet 1.
4. Discussion Supplementation of straw with nitrogen (N) is known to improve feed intake by increasing the supply of N to micro-organisms in the rumen. Caged poultry droppings are comprised of proteins (dietary, micro-organisms) as well as non-protein nitrogenous compounds (ammonia, uric acid) which can be utilized by rumen micro-organisms for their own synthesis. The resultant increased microbial population increases the rate of digesta breakdown and passage of the digesta leading to proportionate improvement in feed intake (Van Soest, 1982). DORB supplementation up to 1000 g (D-3) of a poultry droppings-molasses-mineral supplement was associated with significantly (P < 0.05) higher potential degradability (a + b) and rate constant (c) of DM and NDF of rice straw (Table 2) which were reflective of higher DM and NDF losses than 500 g (D-l) and 750 g (D-2) of supplementation. It is possible that the 1000 g of DORB might have contributed sufficient fermentable energy to the rumen in the form of available cellulose and hemi-cellulose, which are known to stimulate fibre digestion (Silva and Orskov, 1988) apart from its contribution of amino acid-N which is required for microbial growth (Maeng et al., 1976) in addition to non-protein-nitrogen.
234
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Feed Science Technology 58 (1996) 227-237
The improvement in poultry droppings consumption to 491 g in animals kept on diet 3 over that (220 g) reported by Purushottam Reddy et al. (1996) was possibly due to the addition of DORB and a level of 1000 g rice bran (D-3) was found to be optimum to improve palatability of the supplemental feed. Supplementation of DORB at greater than the 500 g (D-l) level to a rice straw diet effected improvements of 0.07% (D-2) and 9.0% (D-3 and D-4) in intake of the rice straw DM and 9.8% (D-21, 25.7% (D-3) and 23.7% (D-4) in intake of the total diet DM. This indicates that DORB acted as a true supplement and there was no additional benefit beyond the 1000 g level (D-3). The major determinant of the apparent digestibility of a diet is its apparent digestibility in the rumen. The level of DORB supplementation positively correlated with the in sacco degradability of rice straw, the correlation coefficients being 0.96 and 0.82, respectively, for (a + b) and c of dry matter. The high correlation between voluntary feed intake (VFI) and its overall apparent digestibility (Blaxter et al., 1961) is thus largely due to correlation of VFI with apparent digestibility of feed in the rumen (Ulyatt et al., 1967). The results of the present work conform with those of Ulyatt et al. (1967). Supplementation of a rice straw-based diet with greater than 750 g DORB (diets 2-4) effected a significant (P < 0.05) improvement in digestibility of DM, DOMD, NDF and ADF while in the case of OM (P < 0.01) and CP (P < 0.05) a level of 1000 g DORB produced improvement (Table 3). It is possible that by offering a DORB-CPD molasses supplement prior to feeding basal rice straw, a greater degree of colonization of the straw may occur, not only by bacteria, but also by rumen fungi (Bauchop, 1981) which have been implicated in fibre breakdown. The animals on diets 1, 2, 3 and 4, respectively, consumed 242 g, 288 g, 344 g and 332 g of crude protein daily (Table 4). O’Donovan et al. (1983) reported that adequate amounts of supplements rich in rapidly rumen-degradable N increased the intake of low-quality mature grass hay due to stimulation of the rate of breakdown of cell walls in the rumen (Campling et al., 1962). Rumen-degradable protein (RDP) needed for optimal rumen microbial activity and microbial protein production is dependent on the overall energy intake. The requirement (RDP = 7.8 X ME intake, MJ; Agricultural Research Council, 1980) of RDP for animals kept on diets 1, 2, 3 and 4 was 219 g, 250 g, 308 g and 301 g, respectively, which indicates that diets provided the required RDP assuming all the CP consumed is rumen degradable. The feed intake and digestibility of nutrients of the present study are in close agreement with the findings of O’Donovan et al. (1983) and Campling et al. (1962). The ratio N/digestible organic matter (N/DOM) for the experimental diets (Table 4) was 0.021-0.022 while the optimum should be 0.032 g N g-’ DOM (Agricultural Research Council, 1980). The nutritive requirements (Kearl, 1982) of buffalo calves weighing 200 kg with daily growth of 250 g are 4.8 kg DM intake, 2.53 kg TDN intake and 281 g DCP intake. The availability of nutrients for different treatments (Table 4) indicates that diet 3 could provide the required DM and TDN intake but less than the required DCP intake. There was a significant (P < 0.05) reduction in pH of strained rumen liquor (SRL) due to graded levels of DORB supplementation from 500 to 1250 g (Table 4). The lowering of pH after feeding (Fig. 1) could be related to increased total volatile fatty acid (TVFA) concentration in the rumen liquor upon feed intake since they are inversely
D.V. Reddy/Animal
Feed Science Technology
I 6
1
641 0
TItiiE
-
D-l
+
D-2
+
215
58 (1996) 227-237
I 8
(h) cl-3
-a-
D-4
Fig. 1. pH of SRL with time after feeding.
6
2
0
TI$E
-
D-l
+
D-2
+
D-3
8
(h) -8-D-4
Fig. 2. NH, -N of SRL with time after feeding.
correlated. Perusal of pH values indicates that the pH is optimum for cellulolytic bacteria (Orskov, 1982). Supplementation of graded levels of DORB enhanced (P < 0.05) the ammonia nitrogen (NH,-N) concentration in SRL proportionately (Fig. 2; Table 4). This increase in NH,-N concentration in SRL of animals fed diets 2, 3 and 4 might possibly be related to the relative consumption of CPD. Increased feed intake with graded levels of DORB supplementation enhanced (P < 0.01) the TVFA concentrations (Fig. 3; Table 4). Th’IS is in accordance with that increased TVFA production associated with increased energy intake (Chaturvedi et al., 1974). 5. Conclusion Voluntary feed intake, in sacco rumen degradability of rice straw, in vivo digestibility of nutrients and rumen parameters for different diets show that daily supplementation of
236
D.V. Reddy/Animal
Feed Science Technology 58 (1996) 227-237
2
0
6 TI&
-
D-l
+
D-2
6
(h) +
D-3
-s-
D-4
Fig. 3. TVFA of SRL with time after feeding.
DORB at the 1000 g (D-3) level along with CPD-molasses-mineral mixture has been found to be optimum to maximize the utilization of rice straw in buffaloes. Further, a need for supplementation of protein meals was felt to overcome the protein insufficiency.
Acknowledgements The author wishes to acknowledge financial support from the International Foundation for Science, Sweden (Grant No. B/1792-1).
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