Livestock Research for Rural Development 20 (supplement) 2008 Guide for preparation of papers LRRD News

Citation of this paper

Effect of coconut oil and cassava hay supplementation on rumen ecology, digestibility and feed intake in swamp buffaloes

A Phengvilaysouk and M Wanapat*

Livestock Research Center, National Agriculture and Forestry Research Institute,
Ministry of Agriculture and Forestry, P O Box 811, Vientiane, Lao PDR

ammalyp@yahoo.com
*bTropical Feed Resources Research and Development Center (TROFREC), Department of Animal Science,
Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand

Abstract

This experiment focused on the effect of cassava hay (CH) and coconut oil (CO) supplementation on feed intake, digestibility and rumen ecology in swamp buffaloes. The experiment was arranged in a 4*4 Latin square design with 4 treatments and 4 replications. The treatments were: C: control, rice straw ad libitum (no supplementation), CH: rice straw ad libitum plus supplementation of cassava hay at 1 kg/hd/d, CO: rice straw ad libitum plus supplementation of coconut oil at 2 ml/kg of BW. CH+CO: rice straw ad libitum plus cassava hay at 1 kg/hd/d plus coconut oil at 2 ml/kg of BW. Four male of swamp buffaloes of 252±6.13 kg live weight were used.

The results show that supplementation of CH or CH+CO significantly increased (p<0.05) NH3-N and blood urea nitrogen (BUN) concentration. The pH, and VFA concentration was not significantly different among treatments, but VFAs tended to increase when supplemented with CH or CH+CO. Supplementation of CO significantly reduced (p<0.05) protozoa population in the rumen. Total DM intake was highest (p<0.05) with supplementation with CH (8.4 kg/d) followed by CH+CO (8.2 kg/d) and supplementation of CO or without supplementation (6.8 and 6.2 kg/day, respectively). The digestion coefficients for DM, OM, CP, NDF and ADF were highest (p<0.05) with supplementation with CH (58.4, 59.8, 61.0, 53.4 and 60.7%, respectively) as compared with supplementation with coconut oil and with no supplementation (p<0.05). The results obtained from this study lead to the conclusion that supplementation affected rumen ecology, diet digestibility and feed intake in swamp buffaloes. When supplemented with CH or CH+CO rumen ecology and digestibility were improved. Supplementation with only CO significantly decreased roughage intake due to reduced numbers of protozoa.

Keywords: cassava hay; coconut oil; digestibility and feed intake; rumen ecology; swamp buffalo


Introduction

In recent years, the human population has increased rapidly, and the demand for food, in particular livestock products is expected to increase in all developed and developing countries. Livestock plays a major role in the livelihoods of small-farmers in Southeast Asia and contributes to the regional and national economic development.

The Lao PDR is a predominantly rural society with 85% of the population depending on agriculture for their livelihoods, and with most of the rural households producing food mainly for their own consumption. Agriculture, including livestock, accounts for 52% of GDP and over 95% of all livestock is owned by smallholders (Stur et al 2002). Livestock provide many benefits, including draft power to cultivate the land, transport of agricultural products, and manure for vegetables, fruit and crop production. Animals act as a safety net for the family when cash is needed, especially for sending children to high school. In developing countries, smallholders commonly use crop wastes after harvest to feed to animals (Chantalakkana 2001).

Most swamp buffaloes are fed on low-quality roughages, agricultural crop-residues, and industrial by-products, which basically contain high levels of cellulose, hemi-cellulose and lignin, as well as low levels of fermentable carbohydrates and poor-quality protein. However, crop residues are an available feed resource in local areas from crop cultivation and are a very important source of roughages for ruminants. Farmers usually give these feed resources, particularly rice straw, to buffaloes as their main diet during the dry season in many Asian countries. These diets result in low performance, productivity and poor health due to their low quality, because rice straw is low in available energy, protein and vitamin, has an imbalance of essential minerals, and contains a large pool of structural carbohydrates (Wanapat 1999). However, The rumen has been long recognized as an essential fermentation vat that is capable of producing end-products, particularly the volatile fatty acids (VFA) and microbial proteins as major energy and protein sources for the ruminant host.

It has been suggested that supplementation of good quality protein can improve roughage intake and digestibility by improving the rumen ecology. Cassava is one of the most important crops as a source of protein for animals, and cassava leaf has a high crude protein concentration of from 16.7 to 39.8%, according to Allen (1984). Furthermore, cassava hay has been reported to manipulate the rumen in terms of improving rumen ecology and enhancing by-pass protein (tannin-protein complex) and hence could improve DM digestibility of low quality feed (Wanapat 2000). In addition, it is possible to improve feed intake, digestibility and the feeding value of rice straw with oil supplementation, particularly coconut oil, which is a fat, consisting mainly of highly saturated (over 90%), and is rich in lauric acid. Saturated fatty acids are more digestible in ruminants than in non-ruminants (Palmquist and Jenkins 1980). The purpose of this experiment was to determine the effect of cassava hay and coconut oil supplementation on feed intake and digestibility, and on rumen ecology and fermentation end-products. Supplementation of coconut oil could increase the energy concentration of the diet, and reduce the protozoa population in rumen, and the combined use of cassava hay and coconut oil could thus be beneficial for small farmers in the tropical areas.
 

Materials and methods

Location

The experiment was conducted at the Livestock Research Center (Nam Xuang), National Agriculture and Forestry Research Institute, Ministry of Agriculture and Forestry, Vientiane Lao PDR, situated 44 km from Vientiane City. The climate in this area is divided into two seasons: dry and wet. The wet season is from May to October. Annual rainfall is on average 1400-1800 mm, and the peak rainfall occurs in the period July to August. The dry season is from November to April. Only about 1 to 2% of the annual rainfall occurs during the dry season. The average minimum and maximum temperatures are about 15oC and 32oC, respectively. This experiment was started in June 2006 and finished in December 2006.

Experimental animals

Four male buffaloes, approximately 2-2.5 years of age with live weights of 252±6.13 kg were used. All animals were confined in separate pens. Fresh water was available all times during the whole experiment. Cleaning of the pen was done daily. A vaccination program, de-worming and a vitamin A, D3, E injection were given before the commencement of the experiment. Each animal was weighed at the beginning and the end of each period.

Experimental design, diet treatment and management

The experiment was arranged in a 4*4 Latin square design with 4 treatments and 4 replications. Four male swamp buffaloes were randomly assigned to treatments. The diets comprised of basal roughage, rice straw (RS), which was fed ad libitum, and with a rumen supplement of 200 g/hd/d. Rice straw was collected from local farms around the Livestock Research Center and transported to a store. Feed offer and feed refusals were weighed every day to calculate feed intake during the first 14 d. Cassava hay (CH) was harvested 3 months after planting by hand, and the green part cut at a height of 50-70 cm above the ground. The foliage was chopped into small pieces (2-3 cm) by chopping machine (hand-operated). After that, it was sun-dried for 2-3 days to reduce moisture (DM>85%) and hydro-cyanic acid (HCN) content. Cassava hay was stored and fed to the buffaloes according to the following treatments in two equal parts in the morning (07:00h) and in the afternoon (16:30h). Coconut oil was bought from the market. The treatments were supplementation of cassava hay or coconut oil according to respective experiments as follows:

All animals were offered fresh water ad libitum and a rumen supplement at 200 g/hd/d of concentrate (50 g urea, 10 g suphur, 50 g salt, 50 g bone meal and 40 g molasses). Buffaloes were adapted to the diets for about 30 days prior to the first period and for intake measurement and sample collection periods during 14 and 5 d, respectively for each period.

Measurements
Body weight, feed intake and digestibility

Buffaloes were weighed at the beginning and at the end of each period for 2 consecutive days (28 days per period). Feed offer and refusals were measured daily to determine feed intake. Feed samples were randomly collected daily, and all samples were combined together and randomly sampled for dry matter (DM), ash and crude protein (CP) analysis according to AOAC (1990). The contents of neutral-detergent fiber (NDF), acid-detergent fiber (ADF) and acid-detergent lignin (ADL) were determined according to the procedure of Goering and Van Soest (1970).

The fecal samples were collected from rectum before feeding in the mornings during the last 5 days of each period. The samples were kept in the refrigerator until analyses for DM, OM, CP, NDF and ADF, with acid insoluble ash (AIA) used as an internal indicator to calculate digestibility of feed according to Galyean (1989).

Blood sampling

Blood samples of about 10 ml were taken from jugular vein into a tube by needle at 0 and 4 hr post-feeding on the last day of each period. The samples were refrigerated for 1 hr and then centrifuged at 3500 x g for 20 min. The plasma was removed and was analyzed for blood-urea nitrogen (BUN) composition according to the method of Roseler et al (1993).

Rumen fluid

Rumen fluid samples (80 ml) were taken at 0 and 4 hr post-feeding on the last day of each period by using a stomach tube connected with a vacuum pump. Rumen fluid pH was determined immediately after sampling by pH meter and rumen fluid was fixed by adding 10% H2SO4 solution (1 ml H2SO4 to 9 ml of rumen fluid) for later analysis of NH3-N concentration (AOAC 1990) and VFA concentration by HPLC (Samuel 1997). Methane (CH4) production was estimated from the concentrations of C2, C3 and C4 according to the equation of Moss et al (2000). The subsequent rumen fluid was immediately fixed with 10% formalin solution (1:9 v/v, rumen fluid: 10% formalin) for measuring the protozoa population (Galyean 1989).

Statistical analysis

All data were analyzed of Variance (ANOVA) according to Latin square design using the General Linear Model (GLM) of Minitab Software Version Release 14 (2003), treatment means which showed significant differences with probability level of p<0.05 were compared using Tukey's pairwise comparison procedures. Statistical model was as follows: Yijk = µ +Ti + Cj + Rk +eijk Where = Yijk = The criteria under study, in treatment were (i); column (j); row (k). µ = Overall sample mean. Ti = Effect of treatment (i). Cj = Effect of treatment (i) at column (j). Rk = Effect of treatment (i) at row (k). eijk = Error
 

Results

Chemical composition of feedstuffs

The chemical composition of the experimental feeds is shown in Table 1. The rice straw contained 92.4% DM. The content of crude protein in rice straw, cassava hay (CH) and rumen supplement was 3.0, 21.3 and 54.6% of DM, respectively, and the level NDF, ADF and ADL in rice straw and CH was 78.2, 51.7, 12.9 and 52.4, 34.0, 10.8% of DM, respectively. Coconut oil (CO) comprises 6% oleic (C18:1); 2% linoleic (C18:2); 6% capric (C10:0); 47% lauric (C12:0); 18% myristic (C14:0); 9% palmistic (C16:0); 3% stearic (C18:0) acid (Scientific Psychic 2005).


Table 1.  Feedstuffs used in the experiment and their chemical composition

Rumen supplement

Rice straw

Cassava hay

Ingredients, %

Urea

25.0

-

-

Suphur

5.0

-

-

Salt

25.0

-

-

Bone meal

25.0

-

-

Molasses

20.0

-

-

Chemical composition, % in DM, except for DM which is on fresh basis

Dry matter

89.4

92.4

91.9

Ash

9.3

13.5

6.7

Crude protein

54.6

3.0

21.3

Neutral-detergent fiber

-

72.8

52.4

Acid-detergent fiber

1.6

51.7

34.0

Acid-detergent lignin

-

12.9

10.8

Condensed tannins

-

-

3.6


Rumen ecology and BUN

Rumen ecology parameters are presented in Table 2. Rumen pH, total VFA and their proportions were not affected by supplementation of CH and CO. Supplementation of CH and CH+CO resulted in significantly higher NH3-N and BUN concentration when compared with the control and CO supplemented groups. Supplementation of CO was significantly reduced (P<0.05) protozoa population (1.2 x105 cells/ml) vs (4.8 x105 cells/ml) when without supplemented oil.


Table 2.  Effect of cassava hay, with or without coconut oil supplementation on rumen ecology in swamp buffaloes

Control

Supplemented groups

SEM

CH

CO

CH+CO

pH,

0 h post-feeding

7.2

7.1

7.1

7.1

0.11

4 h post-feeding

7.1

7.0

7.0

7.1

0.09

NH3-N, mg%

0 h post-feeding

5.8a

13.5b

6.5a

11.6b

0.93

4 h post-feeding

6.6a

17.4b

6.3a

15.7b

1.45

TVFA, mM

93.1

108.4

98.1

103.4

7.49

Acetate

0 h post-feeding

65.4

67.0

62.3

66.0

5.37

4 h post-feeding

57.8

65.9

57.6

59.0

4.99

Propionate

0 h post-feeding

24.3

31.2

28.4

30.6

3.06

4 h post-feeding

21.3

28.7

24.9

28.0

2.35

Butyrate

0 h post-feeding

10.3

12.5

12.3

13.1

1.38

4 h post-feeding

8.8

11.5

8.4

10.9

0.91

BUN, mg%

0 h post-feeding

8.6a

12.3b

6.9a

11.5b

1.55

4 h post-feeding

11.7a

16.9b

7.6a

15.0b

1.06

Protozoa, x105

0 h post-feeding

4.9a

3.7b

1.2c

1.2c

0.11

4 h post-feeding

4.6a

3.3b

1.1c

1.1c

0.10

a,b,c Values on the same row with different superscripts differ (P<0.05)

NH3-N = Ammonia nitrogen; TVFA = Total volatile fatty acid; BUN = Blood-urea nitrogen.

SEM = Standard error of the mean.

Control = No supplementation (fed rice straw ad libitum).

CH = Fed rice straw ad libitum + cassava hay supplementation at 1 kg/hd/d.

CO = Fed rice straw ad libitum + coconut oil supplementation at 2 ml/kg of BW.

CH+CO = Fed rice straw ad libitum + cassava hay at 1 kg/hd/d + coconut oil at 2 ml/kg of BW.


Feed intake and digestibility

Total dry matter intake was significantly higher (p<0.05) in buffalo supplemented with CH, with or without CO, as compared with control and CO supplemented alone (Table 3). Moreover, rice straw intake was higher (p<0.05) in CH without CO supplementation. Digestibility of nutrients is presented in Table 4, and were significantly different (p<0.05) among supplemented groups. Buffalo supplemented with CH had significantly higher diet digestibility than those supplemented with only CO or control treatment. However, there was no difference in digestion in the CH and CH+CO supplemented groups. Digestibility of CP was significantly higher for the treatment with CH. Buffalo live weight changes (LWC) during the experimental period are shown in Table 3. There was a significant difference in LWC among supplemented groups. Buffaloes on diets CH and CH+CO maintained live weight better than animals on C and CO (188 and 100 vs 53 and 45 g/hd/d, respectively.


Table 3.  Effect of cassava hay, with or without coconut oil supplementation, on feed intake and live weight change in swamp buffaloes

 

 Control

Supplemented groups

 SEM

 

CH

CO

CH+CO

Rice straw DMI

 

 

 

 

 

kg/hd/d

6.2a

7.4b

6.4a

6.8c

0.05

% of BW

2.5a

2.9b

2.5a

2.7c

0.02

Cassava hay DMI

 

 

 

 

 

kg/hd/d

-

1.0

-

1.0

0.01

% of BW

-

0.4

-

0.4

0.01

Coconut oil intake

 

 

 

 

 

kg/hd/d

-

-

0.4

0.5

0.04

% of BW

-

-

0.2

0.2

0.01

Total DMI

 

 

 

 

 

kg/hd/d

6.2a

8.4b

6.8c

8.2b

0.05

% of BW

2.5a

3.3b

2.7c

3.3b

0.02

Live weight change

 

 

 

 

 

Initial/kg

253.0

251.2

254.7

252.7

0.98

Final/kg

254.5

256.5

256.0

255.5

0.98

Live weight gain, kg/d

0.053a

0.188b

0.045a

0.100c

0.01

a,b,c Values on the same row with different superscripts differ (P<0.05).
SEM = Standard error of the mean.
DMI = Dry matter intake; kg/hd/d = Kilogram per head per day; % of BW/hd/d = Percent of body weight per head per day; g/kg W0.75 = g nutrients per kg metabolic body weight per head per day;
Control = No supplementation (fed rice straw ad libitum).
CH = Fed rice straw ad libitum + cassava hay supplementation at 1 kg/hd/d.
CO = Fed rice straw ad libitum + coconut oil supplementation at 2 ml/kg of BW.
CH+CO = Fed rice straw ad libitum + cassava hay at 1 kg/hd/d + coconut oil at 2 ml/kg of BW.


Digestion coefficients and nutrient intake

The supplementation of CH, with or without CO significantly increased digestibility coefficients of all nutrients (DM, OM, CP, NDF and ADF) leading to significantly higher digestible nutrient intakes. CO supplementation alone did not additionally improve digestibility and digestible nutrient intake when compared with the control group.


Table 4.  Effect of cassava hay, with or without coconut oil supplementation, on digestibility and digestible nutrients intake in swamp buffaloes

Control

Supplemented groups

SEM

CH

CO

CH+CO

Digestion coefficients, %

Dry matter

47.6a

58.4b

51.5a

54.8ab

0.92

Organic matter

50.6a

59.8b

51.8a

54.5a

0.92

Crude protein

55.4a

61.0b

52.4a

62.3b

0.77

Neutral-detergent fiber

52.3a

53.4a

47.7b

51.6a

0.85

Acid-detergent fiber

54.8a

60.7b

51.9a

52.7a

0.80

a,b,c Values on the same row with different superscripts differ (P<0.05).

SEM = Standard error of the mean.

Control = No supplementation (fed rice straw ad libitum).

CH = Fed rice straw ad libitum + cassava hay supplementation at 1 kg/hd/d.

CO = Fed rice straw ad libitum + coconut oil supplementation at 2 ml/kg of BW.

CH+CO = Fed rice straw ad libitum + cassava hay at 1 kg/hd/d + coconut oil at 2 ml/kg of BW.


Economical returns

The effect of CH and CO supplementation on economical returns is shown in Table 5. Supplementation of CH with or without CO gave significantly higher incomes, of 8.0 and 17.2 USD/hd/month, as compared to the other treatments while supplementation of CO alone significantly improved in economic returns.


Table 5.  Effect of cassava hay, with or without coconut oil supplementation, on economical returns in swamp buffaloes

Control

Supplemented groups

SEM

CH

CO

CH+CO

Expenditure, USD/hd/d

Rice straw

0.31a

0.37b

0.32a

0.34c

0.002

Cassava hay

-

0.19

-

0.19

0.002

Coconut oil

-

-

0.53

0.52

0.006

Rumen supplement

0.30

0.30

0.30

0.30

0.000

Total

0.61a

0.86b

1.15c

1.35d

0.010

LWG/hd/d

0.06a

0.19b

0.05a

0.10c

0.010

Income, USD/hd/m

4.53a

17.14b

3.14a

8.08c

0.760

a,b,c Values on the same row with different superscripts differ (P<0.05).
USD/hd/d or m = United states of dollar per head per day or month;
LWG/hd/d = Live weight gain per head per day; SEM = Standard error of the mean
Control = No supplementation (fed rice straw ad libitum).
CH = Fed rice straw ad libitum + cassava hay supplementation at 1 kg/hd/d
CO = Fed rice straw ad libitum + coconut oil supplementation at 2 ml/kg of BW
CH+CO = Fed rice straw ad libitum + cassava hay at 1 kg/hd/d + coconut oil at 2 ml/kg of BW


Discussion

Rumen ecology and blood-urea nitrogen (BUN)

Buffalo generally have the ability to utilize and consume a wide range of natural grass and crop residues. They are left to graze freely, with limited available feed resources, especially in the dry season, or where there is intensive cropping. During this time, the animals have low performance due to shortage of feeds. Several improvements can be made to the system, and one common strategy is to dry cassava foliage to cassava hay, which is mostly used for ruminants. Whatever, based on this experiment it was found that the rumen pH was similar among treatments, which is similar to the findings of Mom Seng et al (2001), Nguyen van Thu (2001), Promkot and Wanapat (2003) and Yuangklang et al (2001). Vongsamphanh and Wanapat (2004) reported that pH was not significantly different when ruminants were supplemented with different cassava hay diets. Optimum pH for maximum microbial growth is between 6.5 and 7.0 (Hungate 1966).

The mean values of ammonia-nitrogen (NH3-N) concentration in the rumen fluid of buffaloes was affected by supplementation, and were 16.2, 12.6, 6.6 and 7.1 mg%, respectively, with supplementation with cassava hay, cassava hay plus coconut oil, coconut oil and without supplementation. The results were similar to the findings of Wanapat et al (2005), who found that the ammonia-nitrogen concentration in the rumen fluid was not significantly affected by increasing level of oil, but ammonia-nitrogen trended to be increase when supplemented with a high level of 4% urea. These results are similar to those of Vongsamphanh and Wanapat (2004), who showed that ammonia-nitrogen concentration in the rumen ranged from 12.5 to 14.3 mg% when supplemented with cassava hay (600 g/hd/d). In addition, rumen NH3-N was increased from 4.5 to 12.4 mg% in cows fed with untreated and urea-treated rice straw, respectively (Promkot and Wanapat 2003), which is imilar to the findings of Chanthai et al (1989) who found that in cattle fed untreated rice straw NH3-N was less than 2 mg% and increased to 9 mg% when the straw was treated with urea.

Maximum microbial growth efficiency is highly affected by the digestion of poor quality forages in ruminants. Bryant (1973) reported that in principle cellulolytic bacteria species utilize ammonia as the main source of nitrogen. The most suitable rumen NH3-N levels for microbial activities were 5-20 mg/100ml in ruminants fed on low-quality roughages (Boniface et al 1986; Perdok and Leng 1989). Wanapat and Pimpa (1999) found that optimum range of NH3-N was 13.6-34.4 mg/100 ml for microbial protein synthesis and digestibility in buffaloes. A similar result was obtained by Nguyen Van Thu and Preston (1999), who demonstrated that a concentration of rumen NH3-N of 15-30 mg/100ml was optimum for maximum feed intake and digestibility. Preston and Leng (1987) also reported that the optimum level of NH3-N in rumen fluid for microbial growth ranged from 5 to 25 mg/dl and a range of 8.5 to over 30 mg/dl was considered optimum by McDonald et al (1996).

Supplementation of cassava hay or coconut oil did not significantly affect total VFA concentration, but they tended to be higher with supplementation with cassava hay and cassava hay plus coconut oil as compared to supplementation of coconut oil alone or no supplement (108.4, 103.4, 98.1 and 93.1 mM, respectively). Wanapat (2001b) showed that total VFA concentrations at 0 and 4 hr post-feeding in ruminants fed on rice straw were 85.7 and 80.5 mM, respectively. Wanapat et al (2005) found that different supplementation levels of coconut oil significantly affected VFA in the proportions in the rumen. There was a significantly higher level of acetate when animals were supplemented with 2% coconut oil, while propionate and butyrate proportions were increased with supplementation of 4% coconut oil. Nguyen Van Thu (2005) also showed that total VFA were significantly lower when buffaloes were fed rice straw, and were higher when supplemented with sesbania (Sesbania grandiflora) leaves, and similar results were found by Nguyen Van Thu (2001). As Leng (1982) pointed out, the efficiency of microbial growth in the rumen depends on rumen biochemistry, mainly the factors that are involved in the production of VFA in fermentative processes. However, total VFA concentrations in all diets were within the normal range of 70 to 130 mM (France and Siddons 1993)

Blood-urea nitrogen was affected by supplementation of cassava hay and cassava hay plus coconut oil; it was increased when buffalo were supplemented with cassava hay and cassava hay plus coconut oil (14.6 and 13.3 mg%, respectively) as compared to supplemented with coconut oil and not supplemented (9.4 and 10.9 mg%, respectively). These results are in agreement with Vongsamphanh and Wanapat (2004) who found that with supplementation of cassava hay at 600 g/hd/d, BUN concentrations at 0 and 4 hr post-feeding were 10.7 and 13.6 mg%, respectively. Earlier work by Wanapat et al (2005) showed that blood-urea nitrogen was affected by supplementation with a high level of coconut oil (4%) (20.3 mg%). However, BUN has been known to be related to inefficient utilization of dietary CP in ruminants (Lewis 1957).

Coconut oil supplementation reduced the protozoa population in the rumen. The results obtained from this study agree with various earlier studies (Nguyen Thi Hong Nhan et al 2001; Mom Seng et al 2001; Nguyen Thi Hong Nhan et al 2005; Wanapat et al 2005) that found that supplementation of coconut oil or an oil drench significantly reduced protozoa. However, the mean number of protozoa in this study, for animals fed untreated rice straw, was 4.8 x105 cells/ml, while Nguyen van Thu (2001), Yuangklang et al (2003) and Vongsamphanh and Wanapat (2004) reported protozoa numbers of 3.5; 3.9 and 5.3 x105 cells/ml in cattle, respectively. In contrast, this result was lower than the finding of Nguyen Van Thu (2005). In the treatment with supplementation with coconut oil the protozoa population (1.2 x105) was similar to that reported by Nguyen Thi Hong Nhan et al (2005), who concluded that drenching with soy bean oil at levels of 6 and 8 ml/kg BW resulted in a major reduction of the population of protozoa, and in the period 26 to 30 days after giving oil the numbers of protozoa were 1.2 and 0.8 x105 cells/ml, respectively. In contrast with the reduction of protozoa, the numbers of bacteria were increased by oil supplementation (Nguyen Thi Hong Nhan et al 2005a). As reported, supplementation of coconut oil could improve rumen fermentation in terms of the fermentation end-products (Wanapat et al 2005). However, the rumen microbes of native cattle and swamp buffalo fed typical local diets were found to be different, in that buffalo exhibited higher cellulolytic bacteria and fungal zoospores, but had a lower protozoa population (Wanapat et al 2000a).

Feed intake and live weight

Supplementation of cassava hay significantly increased (p<0.05) both DM rice straw and total DM intake. This is similar to the results of Wanapat et al (1989), Wanapat (2001a), Vongsamphanh and Wanapat (2004) and Tran Quoc Viet and Dao Duc Kien (2005), who found that supplementation of cassava hay increased total rice straw DM intakes, growth rate and digestibility of cattle and buffaloes. In the current study, supplementation of cassava hay increased rice straw intake (6.8 and 7.4 kg/d) with and without supplementation of coconut oil (CH+CO and CO, respectively). The results agree with Yuangklang et al (2003), who reported that DM intakes of buffaloes were higher for cassava hay than rice straw treated groups (10.4 and 6.7, respectively). Supplementation of coconut oil alone significantly decreased feed intake (6.4 kg/d), which is in agreement with Mom Seng et al (2001) and Nguyen Thi Hong Nhan et al (2001; 2005a). On the other hand, cassava hay has been used successfully as a source of high protein roughage in lactating diary cows, and when supplementing cassava hay at 0.5-1.7 kg/hd/d, levels of concentrate could be reduced by 0.1-1.6 kg/hd/d, respectively (Wanapat et al 2000).

A linear increase in DM intake was found as level of oil drench increased (Nguyen Thi Hong Nhan et al 2005). Similar results were found by Nguyen Xuan Trach and Mai Thi Thom (2004) who reported that groundnut oil (5 ml/kg live-weight) could improve feed intake, growth rate and profitability. Church (1976) and Preston and Leng (1987) found that adding high levels of fat increased microbial activities. Normally, the fat content of ruminant diets is low (< 50 g/kg), and if it is increased above 100 g/kg the activities of rumen microbes are reduced (McDonald et al 2002). Looper et al (2001) suggested a limit in total fat of 6-7% of the ration dry matter. The live weight changes of buffaloes were significantly improved with supplementation. Supplementation of cassava hay gave the significantly highest gain (188 g/d), while the treatment with cassava hay plus coconut oil gave higher gains than supplementation with coconut oil or no supplementation (100, 45 and 53 g/d, respectively). All the buffaloes could at least maintain body weight during the course of the experiment.

Digestion coefficients and nutrient intake

Supplementation of cassava hay plus coconut oil or supplementation of cassava hay alone significantly improved digestion coefficients of DM, OM, CP, NDF and ADF as compared to the supplementation of coconut oil or no supplementation. This finding is in agreement with Wanapat et al (2005), who illustrated that digestion coefficients of DM, OM and CP were significantly improved by supplementation with 4% coconut oil plus 2% urea (57.3, 60.7 and 59.1%, respectively). Digestion coefficients of DM, NDF and ADF were significantly improved when buffalo were supplemented with sesbania (Sesbania grandiflora) leaves, but was reduced when they were fed with rice straw (Nguyen Van Thu 2005). Vongsamphanh and Wanapat (2004) found that digestion coefficients of DM, CP, NDF and ADF were increased with increased level of supplementation of cassava hay. Apparent digestibility coefficients of DM and OM were significantly different between rice straw and cassava hay (51.0 and 56.4 and 60.0 and 62.0%, respectively (Yuangklang et al 2003). Nguyen Thi Hong Nhan et al (2005a) found that when cattle had been drenched with soybean oil at 8 ml/kg BW, in the periods 20 to 25 days, and 26 to 30 days, after giving the oil the DM digestibility was 52.6 and 54.6%, respectively. Several reports have indicated that cassava hay is a good source of rumen by-pass protein (Ffoulkes and Preston 1978; Wanapat et al 1997), due to the condensed tannins acting to protect the protein from fermentation in the rumen, thus increasing the supply of amino acids to the small intestine. The supplementation should be the aimed at contributing fermentable energy and protein to the rumen to stimulate fibre digestion (Silva and rskov 1985). Cassava hay supplementation, especially at 1-2 kg/hd/d, clearly improved rumen efficiency, reduced production costs and increased economical returns (Wanapat et al 2000).
 

Conclusions and recommendations


Acknowledgements

The authors are extremely grateful to the Swedish International Development Agency (Sida), Department for Research Cooperation with Developing Countries (SAREC), through the MEKARN regional project for supporting this thesis research. Thanks also to the National Agriculture and Forestry Research Institute (NAFRI), Livestock Research Center (LRC) and Tropical Feed Resources Research and Development Center (TROFREC), Department of Animal Science, Faculty of Agriculture, Khon Kean University, Thailand, for permission to use their research facilities and for their cooperation.
 

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