|
MEKARN Regional Conference 2007: Matching Livestock Systems with Available Resources |
Four, rumen-fistulated growing male Thai native swamp buffaloes averaging 330±30 kg in liveweight were fed with urea-treated rice straw (UTS) and concentrate at 0.2% of body weight (BW) as basal diet in a 4x4 Latin square design to determine rumen ecology, microbial protein synthesis and digestibility of diets with different sources of supplemental forages: cassava hay (CH), Phaseolus calcaratus (PH), sweet potato vine hay (SH) or no supplement (UTS). The forages replaced 50% of the UTS on DM basis. The offer level of UTS + forages was ad libitum.
Dry matter intake (2.4 % of BW) was higher in buffalos fed CH than other treatments (2.2, 2.3 and 2.2 % of BW for UTS, PH and SH, respectively). Foliage supplements had no effect on rumen pH and temperature and rumen concentration of acetic, propionic and butyric acids. Ruminal ammonia-nitrogen and blood-urea nitrogen concentrations were higher in the control compared with the other treatments. Bacterial and fungal zoospore populations were not significantly different among treatments. Protozoal population tended to be lower in control and UTS+CH than in other treatments. Nitrogen supply, efficiency of rumen microbial protein synthesis and P/E ratio were highest in CH. The forage supplements had no effect on apparent digestibility coefficients of DM and OM. Apparent digestibility of crude protein was highest in buffalos fed the CH supplement.
It is concluded that 50% replacement of the urea-treated straw basal diet with cassava hay at 50% was beneficial in swamp buffaloes, as it resulted in improved ammonia-nitrogen utilization in the rumen, and increases in nitrogen supply, efficiency of rumen microbial protein synthesis and P/E ratio in nutrients available for metabolism.ff
In the tropics, likewise in Thailand, buffaloes and cattle are raised as an integral part of the crop production system, especially where rice is the main commodity (Chantalakana 2001). According to Wanapat (1995) buffaloes are raised in subsistence systems utilizing grazing and supplementation with on-farm resources. Wanapat et al (1999) and Kennedy and Hogan (1994) have reviewed the major differences between buffaloes and cattle in terms of nutrition. It was found that buffaloes could utilize feed more efficiently, particularly where the feed supply is of low quantity and/or quality, with the digestibility of feed being typically 2-3 percentage units higher than in cattle Wanapat (2000b) suggested that this may be explained by buffaloes having a different rumen ecology than in cattle with higher population of cellulolytic bacteria and fungal zoospores and a greater capacity to recycle nitrogen to the rumen.
An inadequate feed supply is one of the most limiting constraints for livestock growth, reproduction and production in Thailand. Forage quality is important in the context of digestibility and the requirement for additional nutrients. It has been found that buffaloes raised under village conditions suffer from nutritional inadequacy during periods with low forage quantity and/or quality (Scholz et al 1989). The very low nitrogen intake makes energy use less efficient, and considerable protein catabolism occurs to meet energy requirements. Under these conditions the animals may also be more susceptible to infectious or parasitic diseases.
Recently, cassava hay (Manihot Esculenta, Crantz) has been grown as a protein foliage supplement in ruminant feeding especially for dairy cattle, beef and buffalo production (Wanapat 1993; Wanapat 2000a, b; Wanapat 2003; Khang et al 2005). Cassava hay consists of the foliage of the cassava crop harvested usually after 4 months of growth. The stem with leaves is cut into 3-5-cm pieces and then sun-dried for 2-3 days to attain a DM of about 80-90% (Wanapat et al 1997). Cassava hay contains a high level of protein (25% of DM in average) and a strategic amount of condensed tannins (4% of DM on average) according to Wanapat et al (1997).The use of cassava hay was successfully implemented in several ways by either direct feeding or as a protein source in concentrate mixtures (Wanapat et al 2000a, b; Hong et al 2003; Kiyothong and Wanapat 2004a, b), as component with soybean meal and urea in feed supplements (Wanapat et al 2006) and as an ingredient in high quality feed blocks (Wanapat and Khampa 2006).
Other attractive crops are Phaeiolus calcaratus (leguminous crop) and sweet potato for ruminant feeding. Phaseolus calcaratus (PC) has quite a high protein content (15-20% in DM) (Wanapat, unpublished data) and can grow well in poor soil and dry areas. A preliminary study revealed that after two months, PC can grow up to a height of about 20 cm, fully in bloom and produce pods at three months. The whole PC crop can be sun-dried as PC hay as an animal feed while the seeds can be a protein source for human consumption. Phaseolus calcaratus is therefore a promising legume for intercropping and hay making for animal and human food (food-feed system). There have been very few data on PC hay for use in ruminant feeding, research work with this plant is therefore warranted.
Sweet potato (Ipomoea batata (L.) Lam) is one of the most widely cultivated crops on the small farms of tropical America. After harvesting, a large volume of foliage consisting of stems and leaves, and a variable amount of non-commercial roots is left in the field, all of which could be utilized in the feeding of ruminants (Backer et al 1980). Some varieties of sweet potatoes can be grown two to three times per year, with yearly yields of up to 125 tonnes of fresh biomass of which 64% is the aerial part (foliage) (Pinchinat 1970). Chemical analyses of the aerial part have shown values of 12%-17% of crude protein in the DM, less than 18% of fiber in DM, and a dry matter (DM) digestibility higher than 70% (Ffoulkes et al 1978; Ruiz et al 1995). In an experiment designed to evaluate the response of beef cattle fed sweet potato roots and foliage it was found that the average daily intake was 2.37 kg DM/100 kg BW and this intake was independent of the ratio roots/foliage in the diet (Backer et al 1980).
This research was therefore conducted to further establish the effects of
cassava hay, PC hay and sweet potato hay on rumen ecology, digestibility of
nutrients and feed intake in swamp buffaloes fed on urea-treated rice straw.
This experiment was conducted on-station at the Tropical Feed Resources Research and Development Center (TROFREC), Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Thailand from September to December 2006. During this experiment the mean daily temperature was 29 0C and mean relative humidity was 82%.
Four, rumen-fistulated growing male Thai native swamp buffaloes averaging 330±30 kg in weight were fed a urea-treated rice straw (UTS)based diet and 0.2% of body weight (BW) of a concentrate in a 4x4 Latin square design (21 days for each period). The treatments were different sources of supplemental forage: cassava hay (CH), Phaseolus calcaratus (PH) and sweet potato vine hay (SH). The experimental treatments were replacement of 50% of the UTS (Dm basis) with CH, PH or SH. The treatments were therefore, as follow
UTS: 100% of roughage as urea-treated rice straw
CH: Urea-treated rice straw + cassava hay (50:50)
PC: Urea-treated rice straw + Phaseolus calcaratus hay (50:50)
SH: Urea-treated rice straw + Sweet potato vine hay (50:50)
The animals were individually penned and water and mineral block were available at all times. Before the start of the experiment, each animal was treated for external and internal parasite with Ivomectin, and given vitamins A, D3 and E. The animals were adjusted to the respective feeds at least 2 weeks before starting the experiment. In each period the animal was raised in the pen for 14 days and then was moved to metabolism crates for 7 days (2 days for adjustment and 5 days for collecting of samples). The UTS/forage component of the diet was fed ad libitum maintaing the offer level at 50"50 (DM basis). The concentrate (Table 1) was give at 0.2 % of BW to all animals in two equal portions, at 08.00h and 16.00h.
Urea-treated rice straw (UTS) was prepared by mixing 5 kg urea in 100 kg water and adding this to 100 kg of rice straw. The treated straw was covered with a plastic sheet for a minimum of 10 days before feeding to the animals (Wanapat 1985)
The live weight of each animal was determined in the morning prior to feeding at the start and at the end of each period.
During the first 14 days of each period, feed offered and feed refusals were weighed daily for measuring voluntary feed intake. Feed samples were randomly collected twice a week for DM analysis using hot air oven (AOAC 1990). During the last 5 days of each period, feed samples were collected every day and divided into two parts; first part was analyzed for DM while the second part was kept and pooled at the end of each period for analyses of ash, N (AOAC 1990), NDF and ADF (Goering and Van Soest 1970). During the last 5 days of each period faeces were collected and weighed. Samples of about 5% of total fresh weight of the faeces were dried in a hot air oven (60°C) and the dried samples analyzed for DM, Ash, N and EE (AOAC 1990), and for NDF and ADF (Goering and Van Soest 1970). Total urine was collected on the same days as the collection of the faeces by using a plastic container with a few drops of concentrate sulfuric acid to protect the contents from nitrogen loss. Samples of about 10% of urine volume were kept in a refrigerator and pooled at the end of each period to be analyzed for N by the hypochlorite-phenol procedure (Beecher and Whitton 1978). Purine derivatives were measured by High Pressure Liquid Chromatography (HPLC; Model Water 600; UV detector, Millipore Crop.) according to the method of Samuel et al (1997). Microbial protein synthesis was determined according to the procedure of Zinn and Owens (1986).
Blood samples were collected from the jugular vein at 0, 2, 4 and 6 h-post feeding of each animal on the last day of each period (at the same time as rumen fluid sampling). Blood samples were refrigerated for 1 h and then centrifuged at 3500 x g for 20 min. The plasma was removed and was analyzed for blood-urea nitrogen (BUN) according to the method of Roseler et al (1993).
Samples of rumen fluid (80ml) were taken from the fistulated rumen at 0, 2, 4 and 6 h-post feeding of each buffalo. Rumen pH was immediately determined using a glass electrode pH meter. Then 50 ml of fluid were collected and fixed by adding 5 ml of 2M H2SO4 to stop microbe activity and then centrifuged at 3,000 x g for 10 min. About 20-30 ml of supernatant were collected and stored in the freezer (-20°C) until analyzed for NH3-N by the hypochlorite-phenol procedure (Beecher and Whitton 1978) and volatile fatty acids (VFAs) using High Pressure Liquid Chromatography (HPLC; Model Water 600; UV detector, Millipore Crop.) according to the method of Samuel et al (1997). A further portion of the fresh rumen fluid was immediately fixed with 10% formalin solution (1:9 v/v, rumen fluid: 10% formalin) (Galyean 1989) for measuring the microbial population. The total direct count of bacteria, protozoa (Holotrich and Entodiniomorph) and fungal zoospores was made using the procedure of Galyean (1989) using a haemacytometer (Boeco). Methane (CH4) production was estimated from the concentrations of C2, C3 and C4 according to the equation of Moss et al (2000).
The various data sets were subjected to Analyses of variance (ANOVA) procedure according to a Latin square design using the General Linear Model (GLM) of the SAS system for windows (SAS 1998). Treatment means was compared by using Duncan's New Multiple Range Test (Steele and Torrie 1980). The statistical model was:
Yijk = µ + Ti + Cj + Rk + e ijk ,
where,
Yijk = The criteria under study, in treatment i; column j; row k,)
µ = Over all sample mean,
Ti = Effect of treatment i,
Cj = Effect of treatment i at column j,
Rk = Effect of treatment i at row k,
e i j k = Error
The ash content was lower and crude protein higher in the CH compared with PH and and SH supplements (Table 1). Condensed tannin levels were similar for all three forages.
|
Table 1. Chemical composition of concentrate mixture and feeds |
|||||
|
Item |
Concentrate |
UTS |
CH |
PH |
SH |
|
Ingredients, % fed basis |
|
|
|
|
|
|
Cassava chips |
69.0 |
|
|
|
|
|
Rice bran |
15.0 |
|
|
|
|
|
Soybean meal |
8.0 |
|
|
|
|
|
Molasses |
3.0 |
|
|
|
|
|
Urea |
2.0 |
|
|
|
|
|
Salt |
1.0 |
|
|
|
|
|
Sulphur |
1.0 |
|
|
|
|
|
Mineral mixture |
1.0 |
|
|
|
|
|
Total |
100.0 |
|
|
|
|
|
Price; Baht/kg |
5.8 |
|
|
|
|
|
Chemical composition |
|
|
|
|
|
|
DM, % |
87.8 |
55.0 |
89.6 |
89.9 |
89.2 |
|
|
% in DM |
||||
|
Ash |
6.5 |
18.5 |
9.5 |
13.7 |
12.6 |
|
CP |
12.7 |
8.0 |
24.5 |
18.1 |
14.2 |
|
NDF |
10.8 |
69.8 |
49.9 |
45.2 |
42.0 |
|
ADF |
6.7 |
49.0 |
40.7 |
40.0 |
36.1 |
|
CT |
- |
- |
3.2 |
3.2 |
3.1 |
|
HCN( mg/kg) |
- |
- |
1.9 |
2.0 |
2.0 |
|
UTS= urea treated rice straw, CH=
cassava hay, PH= phaseolus calcaratus hay, CP = crude protein, NDF = neutral-detergent fiber, ADF = acid-detergent fiber, CT = condensed tannin, HCN = hydro-cyanic acid, 1 USD = 36 Baht |
|||||
The mean values of ruminal pH and temperature and were similar among treatments, ranging from 6.4 to 6.7 and 38.6 to 39.1ºC, respectively (Table 2). . Ruminal ammonia-nitrogen and blood urea-nitrogen concentrations were significantly higher in the control (UTS) than in other treatments.
|
Table 2. Effect of different local feed resources supplementation on ruminal pH, temperature, ammonia- nitrogen (NH3-N) and blood-urea nitrogen (BUN) of swamp buffaloes |
|||||
|
Item |
UTS |
CH |
PH |
SH |
SEM |
|
Rumen pH |
|
|
|
|
|
|
0 h, post-feeding |
6.6 |
6.6 |
6.6 |
6.5 |
0.08 |
|
2 |
6.8 |
6.7 |
6.7 |
6.5 |
0.12 |
|
4 |
6.6 |
6.6 |
6.6 |
6.5 |
0.13 |
|
6 |
6.6 |
6.5 |
6.4 |
6.4 |
0.09 |
|
Mean |
6.6 |
6.6 |
6.6 |
6.5 |
0.06 |
|
Temperature, ◦C |
|
|
|
|
|
|
0 h, post-feeding |
39.3 |
39.3 |
39.3 |
38.9 |
0.22 |
|
2 |
38.9 |
38.8 |
38.7 |
38.6 |
0.14 |
|
4 |
39.1 |
39.0 |
38.9 |
38.9 |
0.18 |
|
6 |
39.0 |
38.9 |
38.9 |
38.7 |
0.23 |
|
Mean |
39.1 |
39.0 |
38.9 |
38.8 |
0.09 |
|
NH3-N, mg % |
|
|
|
|
|
|
0 h, post-feeding |
23.2a |
18.0b |
16.6b |
15.8b |
1.4 |
|
2 |
34.9a |
32.0ab |
21.9bc |
18.6c |
3.7 |
|
4 |
31.0 |
28.9 |
22.4 |
19.2 |
5.0 |
|
6 |
21.7 |
20.5 |
19.1 |
13.3 |
4.5 |
|
Mean |
28.7a |
27.3ab |
20.3bc |
17.9c |
2.7 |
|
BUN, mg % |
|
|
|
|
|
|
0 h, post-feeding |
19.3a |
18.3ab |
17.8ab |
14.2b |
1.5 |
|
2 |
21.9a |
20.4ab |
18.8ab |
16.5b |
1.6 |
|
4 |
22.6a |
21.4ab |
19.2ab |
16.1b |
1.9 |
|
6 |
22.5a |
21.7ab |
19.7ab |
15.6b |
2.1 |
|
Mean |
21.3a |
20.1ab |
18.6ab |
15.6b |
1.6 |
|
a,b,c Means in the same row with different superscripts differ (P<0.05) NH3-N = ammonia-nitrogen, BUN = blood urea-nitrogen, UTS = urea-treated rice straw, CH = cassava hay, PH = Phaseolus calcaratus hay, SH = sweet potato hay, SEM = standard error of the mean |
|||||
There were no effects of forage treatments on total TVFA, acetic acid (C2) and butyric acid (C4) (Table 3). There was higher (p<0.05) propionic acid (C3) concentration in rumen at 4 h post-feeding of buffalo fed PH which resulted in lower C2 to C3 than in other treatments, however mean value of C3 acid concentration and C2 to C3 ratio were not significantly different among treatments.
|
Table 3. Effect of supplementation on ruminal total volatile fatty acids (TVFA), acetic acid (C2), propionic (C3), butyric acids (C4) and C2 to C3 ratio in swamp buffaloes |
|||||
|
Item |
UTS |
CH |
PH |
SH |
SEM |
|
TVFA, m mol/litre |
|
|
|
|
|
|
0 h-post feeding |
88.6 |
84.9 |
73.7 |
76.5 |
16.8 |
|
2 |
66.7 |
88.2 |
65.9 |
58.7 |
19.2 |
|
4 |
62.4 |
63.3 |
67.1 |
68.1 |
7.5 |
|
6 |
79.5 |
53.5 |
80.3 |
117.7 |
24.5 |
|
Mean |
74.3 |
72.5 |
71.8 |
80.3 |
9.6 |
|
C2, mol/100mol |
|
|
|
|
|
|
0 h-post feeding |
73.5 |
73.8 |
64.1 |
72.4 |
5.7 |
|
2 |
71.8 |
68.3 |
74.1 |
73.4 |
4.5 |
|
4 |
74.8 |
74.7 |
73.0 |
73.4 |
0.8 |
|
6 |
75.1 |
75.2 |
75.3 |
78.7 |
3.5 |
|
Mean |
73.8 |
72.99 |
71.4 |
74.5 |
2.5 |
|
C3, mol/100mol |
|
|
|
|
|
|
0 h-post feeding |
21.8 |
19.7 |
31.8 |
20.8 |
6.5 |
|
2 |
23.5 |
26.3 |
21.0 |
20.5 |
4.3 |
|
4 |
21.5ab |
19.5b |
22.0a |
20.2ab |
0.67 |
|
6 |
21.6 |
20.1 |
20.5 |
15.8 |
2.8 |
|
Mean |
22.1 |
21.4 |
23.8 |
19.3 |
2.7 |
|
C4, mol/100mol |
|
|
|
|
|
|
0 h-post feeding |
4.7 |
6.5 |
4.1 |
6.8 |
1.3 |
|
2 |
4.7 |
5.4 |
4.9 |
6.2 |
0.8 |
|
4 |
3.7 |
5.8 |
5.0 |
6.4 |
1.0 |
|
6 |
3.4 |
4.7 |
5.3 |
5.5 |
1.18 |
|
Mean |
4.1 |
5.6 |
4.9 |
6.2 |
0.7 |
|
C2/C3, mol/mol |
|
|
|
|
|
|
0 h-post feeding |
3.4 |
3.8 |
2.9 |
3.5 |
0.4 |
|
2 |
3.2 |
3.0 |
3.6 |
3.6 |
0.5 |
|
4 |
3.2ab |
3.5a |
2.8b |
3.4a |
0.2 |
|
6 |
2.8 |
2.1 |
7.2 |
2.4 |
1.8 |
|
Mean |
3.5 |
3.8 |
3.6 |
9.6 |
3.6 |
|
a,b,c Means in the same row with different superscripts differ (P<0.05) TVFA = total volatile fatty acids, C2= acetic acid, C3 = propionic, C4= butyric acids, C2/C3= concentration of acids acetic acid to propionic ratio
UTS = urea-treated rice straw, CH = cassava hay, PH = Phaseolus
calcaratus hay, |
|||||
DM intake and crude protein apparent digestibility were higher with CH supplementation compared with other treatments (Table 4). There were no differences in coefficients of apparent digestibility of DM, OM, NDF and ADF. Body weight changes were not affected by forage supplementation.
|
Table 4. Effect of different local feed resources supplementation on voluntary dry matter feed intake and nutrient digestibility in swamp buffaloes |
|||||
|
Item |
UTS |
CH |
PH |
SH |
SEM |
|
DM, intake |
|
|
|
|
|
|
Urea-treated rice straw |
|
|
|
|
|
|
kg/d |
6.7a |
4.2b |
4.2b |
4.2b |
0.28 |
|
%BW |
1.9a |
1.3b |
1.2b |
1.2b |
0.06 |
|
g/kgBW0.75 |
83.6a |
52.9b |
51.5b |
51.6b |
3.09 |
|
Forage hay |
|
|
|
|
|
|
kg/d |
- |
3.4a |
2.6b |
3.3a |
0.03 |
|
%BW |
- |
1.0a |
0.8b |
1.0a |
0.03 |
|
g/kgBW0.75 |
- |
41.8a |
33.0b |
41.1a |
1.28 |
|
Total intake, kg/d |
7.4 |
8.3 |
7.5 |
8.2 |
0.28 |
|
%BW |
2.2a |
2.4b |
2.2a |
2.3ab |
0.08 |
|
g/kgBW0.75 |
92.3 |
103.3 |
93.1 |
101.3 |
3.87 |
|
Weight change, kg/day |
0.23 |
0.23 |
0.21 |
0.21 |
0.03 |
|
Apparent digestibility, % |
|
|
|
|
|
|
DM |
73.1 |
78.4 |
71.0 |
73.0 |
2.5 |
|
OM |
76.9 |
82.4 |
75.2 |
77.2 |
2.5 |
|
CP |
57.7a |
82.7b |
67.7a |
67.4a |
3.3 |
|
NDF |
74.1 |
76.8 |
70.4 |
69.0 |
3.0 |
|
ADF |
67.9 |
71.6 |
61.7 |
61.7 |
3.6 |
|
a,b,c Means in the same row with different superscripts differ (P<0.05) DM = dry matter, OM = organic matter, CP = crude protein, NDF = neutral-detergent fiber, ADF = acid-detergent fiber,
UTS = urea-treated rice straw,
CH = cassava hay, |
|||||
Bacterial and fungal zoospore populations were not significantly different among treatments. Protozoal population tended to be lower in control and UTS+CH than in other treatments.
|
Table 5. Effect of cassava hay, Phaseolus calcaratus hay and sweet potato hay on ruminal microorganism population in swamp buffaloes |
||||||
|
Item |
UTS |
CH |
PH |
SH |
SEM |
|
|
Bacteria, x 109 cells/ml |
|
|
|
|
||
|
0 h-post feeding |
2.2 |
2.9 |
2.3 |
2.5 |
0.26 |
|
|
4 |
4.2 |
4.5 |
3.9 |
4.3 |
0.41 |
|
|
Mean |
3.2 |
3.8 |
3.2 |
3.4 |
0.29 |
|
|
Protozoa, x 105 cells/ml |
|
|
|
|
||
|
0 h-post feeding |
9.3ac |
7.4a |
14.0bc |
16.6b |
1.80 |
|
|
4 |
10.1 |
13.3 |
14.4 |
25.3 |
4.90 |
|
|
Mean |
9.7a |
10.4a |
14.2ab |
21.0b |
2.75 |
|
|
Fungal zoospores, x 106 cells/ml |
|
|
|
|||
|
0 h-post feeding |
2.8 |
2.0 |
2.4 |
2.5 |
0.43 |
|
|
4 |
4.7 |
3.4 |
3.9 |
4.4 |
0.66 |
|
|
Mean |
3.8 |
2.7 |
3.1 |
3.5 |
0.51 |
|
|
a,b,c
Means in the same row with different superscripts differ
(P<0.05) |
||||||
Excretion of purine derivatives
The estimated daily production of microbial protein, the efficiency of rumen microbial protein synthesis and the P/E ratio in products leaving the rumen, were highest for the treatment with CH supplementation and lowest for the control diet (UTS) with intermediate values for the PH and SH treatments (Table 6). The calculated values of methane production showed no differences among the treatments.
|
Table 6.
Effect of cassava hay, Phaseolus calcaratus hay and sweet
potato hay on rumen microbial protein |
|||||
|
Item |
UTS |
CH |
PH |
SH |
SEM |
|
1/ Allantoin, m mol/d |
67.1a |
138.4b |
86.5ac |
95.3c |
6.9 |
|
1/Total PD, m mol/d |
78.9a |
162.8b |
101.7ac |
112.2c |
8.1 |
|
2/PD absorption, m mol/d |
56.4a |
155.0b |
83.3ac |
95.3c |
9.5 |
|
2/Microbial protein supply, g N/d |
41.0a |
112.7b |
60.5ac |
69.3c |
6.9 |
|
3/EMNS gN/kg OMDR |
13.1a |
28.9b |
19.6c |
19.0c |
1.6 |
|
4/VFA production, MJ/d |
9.9 |
9.7 |
9.6 |
10.7 |
1.1 |
|
P/E ratio, g/MJ |
5.0a |
13.5b |
6.8ab |
6.7ab |
2.0 |
|
5/ CH4 production, mol/100mol |
33.4 |
34.0 |
32.2 |
35.5 |
1.8 |
|
a,b,c Means in the same row with different superscripts differ (P<0.05) 1/Allantoin in urine of cattle estimated to be 80-85% of total purines (IAEA 1997); 2/PD absorption was calculated according to Verbic et al (1990) 2/Microbial N synthesis was calculated according to Chen et al (1993) 3/OMDR = organic matter digestible in the rumen estimated to be 65% of organic matter digested in total tract 4/VFA production = 7.5 mol VFA/1 kg dry matter digested (Czerkawski et al 1986) 5/CH4 production = 0.5*(acetate) – 0.25*(propionate) + 0.5*(butyrate) (Moss et al 2000)
UTS = urea-treated rice straw, CH
= cassava hay, PH = Phaseolus calcaratus hay, |
|||||
Rumen pH values were similar to those reported by Chanjula et al (2004), who observed that cassava hay supplementation to urea-treated rice straw (50:50 ratio), in diets of buffaloes, did not affect rumen pH (6.7-6.9) when compared with the control group. There are no reports of rumen pH in diets with sweet potato and PC hay supplementation fed to swamp buffaloes. However, the pH values in this study were within the normal range which has been reported as optimal for microbial digestion of fiber (Lyle et al 1981). Rumen NH3-N concentrations in this study were higher than in that of Wanapat (2001) and Chanjula et al (2004) who fed similar roughages. Ammonia-N in the rumen is a pool of several inputs and outputs. Ammonia is derived from degradation of dietary protein and dietary NPN, from the hydrolysis of urea recycled to the rumen, and from the degradation of microbial crude protein. Ammonia disappears from the rumen pool due to uptake by the microbes, absorption by the microbes, absorption through the rumen wall, and flushing to the omasum (NRC 1996). Changes in any of these factors will alter NH3 concentration in the rumen (Ørskov 1982). Thus, NH3 concentration is too dynamic to be a good indicator of the nitrogen status of the ruminal environment. However, rumen ammonia concentrations for all treatments were in the optimum levels (15 to 30 mg %) for efficient rumen digestion as reported by Perdok and Leng (1990) and Wanapat and Pimpa (1999).
In the present study BUN levels reflected those for rumen ammonia. Preston (1996) suggested that the quantity of ammonia absorbed from the rumen was reflected in circulating BUN.
The 10% increase in DM intake and the higher apparent digestibility of crude protein for the diet supplemented with cassava hay probably reflected the higher intake of crude protein on this diet. Chanjula et al (2004) reported that apparent digestibility coefficients of all nutrients were linearly increased when cassava hay replaced 0, 25, 50 and 100 % of urea-treated rice straw in diets of growing buffaloes.
Chanjula et al (2004) reported that cassava hay supplementation to urea-treated rice straw in buffalo diets led to a trend for increasing cellulolytic and proteolytic bacterial populations whilst total protozoal counts were dramatically decreased. These findings are in contrast to those in the present study where there were no effects on populations of bacteria, protozoa and fungi, due to cassava hay supplementation. The lack of differences in VFA production among treatments also suggests that the protein-rich forages had little effect on the pattern of rumen fermentation.
The greater efficiency of rumen microbial protein synthesis, and the higher P/E ratio output from the rumen, with cassava hay compared with hays made from Phaseolus calcaratuse or sweet potato vines, indicates there was a better balance of the available fermentable energy and degradable crude protein in the rumen with the cassava supplement. The apparently superior nutritive value of cassava foliage compared with sweet potato vines is supported by the findings of Ffoulkes and Preston (1978) that growth rates were 80% higher (870 vs 390 g/day) when cassava foliage rather than sweet potato vines was protein supplement for fattening cattle fed a basal diet of molasses/urea.
Cassava hay was superior to hays made from Phaseolus calcaratuse or sweet potato vines, as a supplement for growing swamp buffaloes fed a basal diet of urea-treated rice straw.
The authors would like to express their sincere thanks to all who have assisted and supported the research in this study, particularly the MEKARN project financed by SIDA-SAREC, and the Tropical Feed Resources Research and Development Center (TROFEC) of Khon Kaen University facilitating the use of the experimental animals, equipment and laboratory analyses.
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