Effects of mangosteen (Garcinia mangostana) peel and sunflower and coconut oil supplementation on rumen fermentation, milk yield and milk composition in lactating dairy cows
 

Suchitra Kanpukdee and Metha Wanapat

Tropical Feed Resources Research and Development Center, Department of Animal Science,
Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand
nunim_su@yahoo.com

Abstract

An experiment was conducted on-farm in Muang district, Khon Kaen Province, Thailand. Five crossbred dairy cows (75% Holstein-Friesian), at 100-150 days-in-milk (DIM) and with 450±50 kg BW were used to evaluate the effects of mangosteen (Garcinia mangostana) peel, sunflower oil and coconut oil supplementation on feed intake, nutrient digestibility, ruminal fermentation, milk yield and milk composition. Experimental design was a 5 x 5 Latin square design. Cows were fed rice straw and ruzi grass (Brachiaria ruziziensis) ad libitum. Concentrate was fed based on milk production of 1 kg concentrate to 1.5 kg milk production. Five supplemented treatments were control (no supplement) and two levels of mangosteen peel at 100 and 200 gDM/hd/d with (MSP100-SFCO, MSP200-SFCO) or without (MSP100, MSP200) addition of 6% vegetable oils (3% sunflower oil and 3% coconut oil) in the concentrate. Each feeding period lasted for 21 days, during which feed intakes and milk yield were recorded.

The results revealed that level of mangosteen peel supplementation or supplementation with vegetable oils did not affect nutrient digestibility, blood-urea nitrogen, milk production and composition. However, dry matter intake was significantly reduced with supplementation of mangosteen peel with vegetable oil: 3.1, 3.1, 3 2.8 and 2.7 % BW for control, MSP100, MSP200, MSP100-SFCO, and MSP200-SFCO, respectively. Ruminal ammonia-nitrogen and acetic acid (C2) concentrations were significantly lower, while propionic acid concentration (C3) was higher in supplemented groups, especially with mangosteen peel supplementation with vegetable oils as compared with the control group. Supplementation of mangosteen peel without or with vegetable oils in the diet reduced rumen protozoal population significantly (P<0.05) (13.7 11.9 12.8, 8.8 and 9.7x10⁵ cell/ml for control, MSP100, MSP200, MSP100-SFCO, and MSP200-SFCO, respectively), while rumen bacterial population was significantly increased as compared to the control group. The MSP100-SFO group had a higher milk yield (FCM) and higher fat content and hence, resulted in higher income return.

Based on this study, a conclusion can be made that supplementation of mangosteen peel at 100 gDM/d with vegetable oils could be beneficial for dairy cattle fed a rice straw and ruzi grass (Brachiaria ruziziensis) based diet. The benefits were improved rumen ecology, especially bacterial population, and reduced concentrate cost, hence with higher economical return.

Key words:  Condensed tannins, local feed resources, rumen ecology, saponins
 

Introduction

Practically, 95 to 99 % of dairy farms in Thailand can be classified as small scale or small-holder farms under mixed crop-livestock farming systems (Wanapat 1995a; Chantalakhana and Skunmum 2002). Crop residues, shrubs, and tree fodders are locally available in large amounts and are important in small farms to alleviate shortages of feed and increase the efficiency of the production systems in the tropics (Leng 1993) including the northeast of Thailand (Wanapat 1999). Concentrate supplementation for lactating dairy cows has been practiced by many small-holder farmers in the tropics by giving 0.5 kg concentrates per 1 kg of milk (ratio of 1:2), as a rule of thumb, without taking into account the nature of the roughage used and the actual nutrient requirements (Wanapat 1999). In some areas of Thailand, concentrate use was found to be even higher than 1:1 concentrate to milk yield, which could possibly result in rumen acidosis, especially when effective sources of fibre are not available. Although, high level of fed concentrates usually achieve greater levels of milk production, is not often that they have been economically efficient (Rowlinson 1997). Feed costs are about 70% of total operating costs, the largest being expenditure on concentrates (65- 80 %), resulting in increasing production costs (Wanapat 1995b). Therefore, strategic supplementation of local feed resources at lower ratios of concentrate to milk yield, from 1:2 to 1:3 or lower should be advantageous. Mangosteen (Garcinia mangostan) peel is a fruit by-product which is easy to collect, and therefore is recommended for use as a dietary supplement to improve rumen ecology and rumen productivity. Mangosteen peel contains both condensed tannins and crude saponins, which exert a specific effect against rumen protozoa, while the rest of the rumen biomass remains unaltered (Ngamsaeng and Wanapat 2005). Ngamsaeng and Wanapat (2005) suggested that supplementation of mangosteen peel (100 gDM/d) in cattle can increase rumen bacteria and decrease the protozoal population, and maintain the fungal zoospore population. However, there are no investigations of the effect of condensed tannins and saponins in mangosteen peel in lactating dairy cattle.

Fat is an important energy component in the diet of ruminants. Over the last decade fat supplementation has become a common practice to increase the energy density of the diets for high producing dairy cows (Bauman et al 2003). Fat supplementation in dairy cows can increase milk yield (Amaral et al 1997; Avila et al 2000; Ruppert et al 2004) as well as increase milk fat and the content of long-chain fatty acids in milk (Aldrich et al 1997). Looper (2001) suggested a limit of total fat of 6-7% percent in the ration DM of dairy cows. Feeding fat above a certain level (6-7%) reduces feed intake and reduces fiber digestion by inhibiting microbial fermentation in the rumen. Coconut oil and sunflower oil are sources of fat that can be used for supplementation. Coconut oil is high in saturated fat (over 90 %) and is rich in lauric acid. Saturated fatty acids have a higher digestibility in ruminants than in non-ruminants (Palmquist and Jenkins 1980). Coconut oil 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) and 3% stearic (C18:0) acid (Scientific Psychic 2005).  Sunflower oil contains 12% saturated fatty acids and 88 % unsaturated fatty acids (Grant and Kubik 1990), consisting of 8% palmitic (C16:0), 3% stearic (C18:0) 13.5% oleic (C18:1), 75% linoleic (C18:2) and 0.5% linolenic (C18:3) acid (Palmquist 1988).

Chantaprasarn and Wanapat (2005) suggested that the use of sunflower oil at 2.5 % in dairy cow diets has the greatest advantages in milk yield and composition, especially conjugated linoleic acid (CLA) content. Pilajun et al (2005) studied the effects of coconut oil and sunflower oil on rumen fermentation and rumen microorganisms in dairy steers and found that a ratio of 50% coconut oil and 50% sunflower oil supplementation gave the greatest improvement in DM and NDF digestibility, ruminal concentration of total VFA and acetic acid, when compare with the control. Therefore, the objectives of this study were to examine the level of mangosteen peel supplementation, alone or combined with sunflower and coconut oils, on rumen fermentation, digestibility and production of lactating dairy cows.
 

Materials and methods

Location and duration

This experiment was conducted on-farm in Muang district, Khon Kaen province, Thailand and at the Tropical Feed Resources Research and Development Center (TROFREC), Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Thailand, from July to October 2006. During this experiment, the mean daily temperature was 29 ⁰C (26-32 ⁰C) and mean relative humidity was 82%.

Experimental design, diet and treatments

The experimental design was a 5x5 Latin square design with 21 days for each period. The treatments were: no supplementation (control) and two levels of mangosteen peel with or with out a combination of vegetable oils (sunflower oil and coconut oil), and were as follows:

• CON = Control (no MSP, SFO and CO supplementation)

• MSP100 = 100 gDM of MSP/hd/d

• MSP200 = 200 gDM of MSP/hd/d

• MSP100-SFCO = 100 gDM of MSP/hd/d +3% sunflower oil and 3% coconut oil

• MSP200-SFCO = 200 gDM of MSP/hd/d + 3% sunflower oil and 3% coconut oil

Animals and housing

Five crossbred dairy cows (75% Holstein-Friesian) in lactations 1-3 were used. The cows were in mid-lactation (100-150 DIM) and with an average liveweight of 450 ± 50 kg, and were fed ad libitum on rice straw and fresh ruzi grass (Brachiaria ruziziensis) at a ratio 1:1 rice straw to ruzi grass. A supplement of 1 kg concentrate (18% CP) per 1.5 kg milk yield per head per day was offered two times a day during milking. Mangosteen peels (MSP) were collected from fruits and were sun-dried and ground into powder form. Ground MSP was mixed with the concentrate before feeding, according to treatment. The concentrate was offered in two equal portions during milking times. The diets were fed for 21 days during each experimental diet 14 days adaptation and last 7 days for data collection. Clean fresh water and mineral blocks were available at all times. Cows were milked by bucket milking machine twice a day (05.00h and 16.00h). After milking, the cows were confined together in the barn. During the last 5 days of each period cows were individually penned to measure their feed intakes and to collect rumen fluid, blood samples, and fecal collection by rectal sampling.

Samplings and analysis

Weight monitoring

The cows were weighed at the beginning and the end of each period to monitor live weight changes.

Feed sampling

All feeds were weighed before feeding and supplied separately to the cows and feed refusals were weighed each morning for calculation of daily feed intake. In the last 5 days of each period, feed samples were collected then combined together and randomly collected for analyses of DM, Ash, CP and EE (AOAC 1990), neutral-detergent fiber (NDF) and acid-detergent fiber (ADF) according to the method of Goering and Van Soest (1970). Condensed tannins contents in MSP were analyzed by using the vanillin-HCl method (Burns 1971) modified by Wanapat and Poungchompu (2001). Crude saponins were measured by using methanol extraction following the method of Kwon et al (2003) as modified by Wanapat and Ngamsaeng (2004).

Faecal sampling

During the last 5 days of each period faecal samples were collected from the rectum of individual cows and dried in a hot-air oven (60°C), and dried samples were analyzed for DM, Ash, CP and EE (AOAC 1990), NDF and ADF (Goering and Van Soest 1970) and acid-insoluble ash (AIA) (Van Keulen and Young 1977). AIA was used as an internal indicator to calculate the digestion coefficients.

Blood sampling

Blood samples were collected from the jugular vein at 0 and 4 h post feeding from 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) composition according to the method of Roseler et al (1993).

Rumen fluid sampling

Samples of rumen fluid (80ml) were taken at 0 and 4 h post feeding from each cow via a stomach tube connected with vacuum pump. Rumen pH was immediately determined by using a glass electrode pH meter. Then 50 ml of fluid were collected and fixed by adding 5 ml of 2M H₂SFO₄ to stop microbial 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 further analysis in the laboratory. Rumen fluid was analyzed for NH₃-N by the hypochlorite-phenol procedure (Beecher and Whitton 1978) and volatile fatty acids (VFAs) by using High Pressure Liquid Chromatography (HPLC; Model Water 600; UV detector, Millipore Crop.) according to the method of Samuel et al (1997). The subsequent 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 (Holotrichs and Entodiniomorphs) and fungal zoospores was made using the procedure of Galyean (1989) by 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).

Milk yield and composition

Daily milk yields in the morning and in the afternoon of each individual cow were recorded. Milk samples were taken from morning and afternoon milking (morning milk to afternoon milk = 60:40) at the last two days of each period. Milk samples were collected from two consecutive a.m. and p.m. milkings of each cow and were analyzed for milk composition (fat, protein, lactose, total solids fat and solids not fat) using Milko scan. Milk-urea nitrogen (MUN) was analyzed by using the Sigma diagnosistics procedure.

Statistical analysis

All data were subjected to Analysis of variance (ANOVA) according to a Latin square design using the General Linear Models (GLM) of the SAS System for Windows (SAS 1998). Treatment means were compared using Duncan's New Multiple Range Test (Steel and Torrie 1980). The statistical model was:

Y_ijk = m + T_i + C_j + R_k + e_{ijk ,}

where:

Y_ijk = The criteria under study, in treatment i; column j; row k,
m = Over all sample mean,
T_i = Effect of treatment i, C_j = Effect of column j,
R_k = Effect row k and
e_ijk = Error
 

Results

Chemical composition of the experimental feeds

The composition of the concentrate and the chemical compositions of feeds, and feedstuffs are shown in Table 1. The CP, NDF and ADF were 17.4 28.7 and 19.5% of DM; 2.9, 79.5 and 53.5 % DM; 6.7, 73.5, and 45.5 of DM, and 21.5, 5.5 and 50.0% of DM, in concentrate, rice straw, ruzi grass, and MSP, respectively. Ground MSP contained 15.8% and 9.8% (w/w) of condensed tannins and crude saponins, respectively. The estimate price of concentrate was 0.16 USD/kg (as fed basis).

Ruminal temperature, pH, ammonia-nitrogen (NH₃-N) blood-urea nitrogen (BUN) and milk-urea nitrogen (MUN)

Rumen ecology parameters, temperature, pH, NH₃-N, BUN and MUN are presented in Table 2. The values of ruminal temperature, pH, BUN and MUN were similar at 0 and 4 h post feeding and among all treatments. Mean values were stable at 38.9 º C, 7.0 16.6 mg% and 17.6 mg% for temperature, pH, BUN and MUN, respectively. Ammonia-nitrogen concentrations (NH₃-N, mg %) in the rumen fluid were significantly lower (P<0.05) in MSP200-SFCO and higher in MSP100 (9.3 and 12.5, respectively). Supplementation of vegetable oils tended to lower the concentration of BUN and MUN, although the response to MSP supplementation was not consistent.

Volatile fatty acids and methane (CH₄) production  

The influence of MSP, SFO and CO supplementation on acetic acid (C2), propionic acid (C3), and butyric acid (C4) proportions, and acetic acid to propionic acid (C2/C3) ratios are shown in Table 3. Supplementation of MSP, SFO and CO did not affect TVFA production and butyric acid. However, acetic acid (C2), propionic acid (C3), and acetic acid to propionic acid (C2/C3) ratios were significantly different (P<0.01) as compared to control. Supplementation of MSP, without or with vegetable oil, significantly affected C2 and C3 production by decreasing C2 and thus lowing the C2/C3 ratio. The mean values of methane (CH₄) production in the rumen were significantly lower (P<0.01) for MSP supplementation, without and with vegetable oil supplementation, as compared to the control group (34.1, 32.5, 32.8, 31.9 and 32.1 mmol/L for Control, MSP100, MSP200, MSP100-SFCO and MSP200-SFCO respectively).

Ruminal microorganism populations

The effects of MSP, SFO and CO supplementation on ruminal microorganisms, total counts of bacteria, protozoa and fungal zoospores, measured at 0, and 4 h post feeding, are shown in Table 4. Total bacterial and protozoal counts were significantly different (P<0.01) at 0 and 4 h post feeding. As shown, supplementation of MSP without and with vegetable oils significantly (P<0.05) increased the bacterial population compared to the  control group, and ranking from the highest to lowest, bacterial populations were MSP200-SFCO, MSP100-SFCO, MSP100, MSP200, and control, respectively. Supplementation of MSP with or without vegetable oils decreased protozoal populations, while the fungal zoospore population was not affected. However, supplementation of MSP200 with or without supplementation of vegetable oils tended to change the rumen microbial population.

Feed intake and body weight

The effects of MSP, SFO and CO on feed intake and body weights are presented in Table 5. Roughage, concentrate and total dry matter intakes in terms of intake kg/d in cattle were significantly higher (P<0.05) in MSP100 and lower in MSP200-SFCO, respectively. Supplementation MSP with vegetable oils reduced (P<0.05) roughages and concentrate DMI. However, increasing levels of MSP supplementation in the diet tended to decrease concentrate DMI. Body weight changes were not affected by MSP, with or without vegetable oils supplementation, and thus all animals in all treatment groups could maintain liveweight throughout the experimental period.

Digestion coefficients and nutrient intake

Digestion coefficients, estimated nutrients and energy intakes are shown in Table 6. Digestibility of DM, OM, CP, NDF and ADF was not significantly different (P>0.05) among treatments, but supplementation of MSP100, with or without vegetable oils, slightly increased digestibility compared to MSP200, with or without vegetable oils. Digestible nutrient intakes of CP, NDF and ADF were significantly lower (P<0.05) in supplementation with MSP100 and MSP200 with vegetable oils groups.

Milk yield and milk composition

The effects of MSP, SFO and CO on milk yield and milk composition are shown in Table 7.  Supplementation SFO and CO tended to give higher milk fat, other treatments were similar.

Discussion

Chemical composition

The CP, NDF and ADF contents in untreated rice straw and ruzi grass were similar to the values reported by Kiyothong and Wanapat (2003) (4.3, 78.6, and 47.2 in untreated rice straw and 8.2, 77.9 and 38.7 % in ruzi grass, respectively). The CT value in MSP (15.2%) was similar to Ngamsaeng and Wanapat (2005) (16.8%). Crude saponins in MSP (9.8%), were higher than in other plants, such as Yucca schidigera (4.4%) (Eryavuz and Dehority 2004), seed of Moringa oleifera (2.2%) (Anhwange et al 2004), Enterolobium cyclocarpum (1.9%) and Pitheecellobium saman (1.7%), but were lower than in Sapindus saponaria (12%) (Hess et al 2003). The high levels of CP, CT, and CS in MSP could be of interest for it to be used as an alternative feed resource for ruminants due to its possible interactive effect.

Effect of MSP supplementation on rumen ecology parameters 

The ruminal temperature and pH were similar among treatments and were in normal ranges, which have been reported as optimal for microbial digestion of fiber (39 to 41 ºC and 6.5 to 7.0, respectively) (Hoover 1986; Firkins 1996; Wanapat 1990). The average values of NH₃-N in this study were 9.5 to 12.5 mg/dl. According to numerous reports, the optimal ammonia concentration in ruminal fluid for microbial growth ranges from 5.0 to 25.0 mg% (Preston and Leng 1987) 15 to 30 mg% (Perdok and Leng 1990; Wanapat and Pimpa 1999), and 8.5 to over 30 mg/dl (McDonald et al 1996). The average values of NH₃-N in the present study were within the ranges of those reported above. Supplementation of sunflower and coconut oil tended to reduce the NH₃-N concentration, which in MSP200-SFCO was significantly lower (P<0.05) than in the other treatments. This result agrees with Preston and Leng (1987) who reported that adding high levels of fat affects microbe activities. BUN and MUN values in this study ranged from 16.0 to 17.3 and 17.0 to 18.2 mg/dl, respectively. Recently, Abeni et al (2000) reported that BUN concentrations relate to dietary CP to energy ratio in the diets. Therefore, in healthy ruminants, BUN and MUN concentrations reflect protein to energy ratio in the diet (crude protein: digestible organic matter, CP: DOM ratio). Preston (1996) suggested that the quantity of ammonia absorbed from the rumen is reflected in circulating BUN. Diets which are balanced in P/E have BUN concentrations of 12.7 mg%, while BUN levels lower than this could be due to an insufficiency in CP per unit of digestible energy (Hwang et al 2001).  Increases in the NH₃-N levels also result in an increased level of BUN. In previous studies, Preston et al (1965) and Lewis (1975) reported that the concentration of BUN is correlated to the level of ammonia production in the rumen. Urea in the blood has been found to reach a maximum 3 h post feeding (Eggum 1970) and is commonly considered to reflect the protein quality in the diet. Moreover, Gustafson and Palmquist (1993) observed diurnal variations in BUN, ruminal NH₃-N and MUN for the whole day, and reported that typical BUN concentrations peak about 4 to 6 h post feeding. Overall, MUN concentrations were above the recommended maximum of 16 mg/dl, indicating over-consumption of CP or RDP, and inefficient N use, which decrease fertility and potential loading development (Ferguson et al 1993; Butter et al 1996). Schroeder (2002) reported that cows with MUN levels less than 10 to 12 mg/dl and higher than 16 to18 mg/dl result in higher feed costs, reduced health, lower productive performance and low milk production. According to those references above, the MUN of all treatments in the present study was within range and indicated an adequate protein intake for this milk yield.

Effect MSP supplementation on ruminal microorganism population

It appeared that MSP, SFO and CP might play an important role in changing rumen microorganism populations as a result of fatty acid, CT and/or CS. The results show that bacterial population increased, while protozoal population decreased when MSP, SFO and CO were supplemented, and fungal zoospores population changed only slightly. The result was similar to Wina et al (2003), who evaluated the effect of saponin containing plant materials such as Morinda citrifolia (fruit), Nothopanax scutellarium (leaves), Sesbania sesban (leaves), and Sapindus rarak (fruit) on in vitro fermentation, and found that protozoal populations were lowest in the treatments with Sapindus rarak, and concluded that saponin-rich plants have a potential as a natural defaunating agent. However, in the study done by Rowe et al (1985), the total number of bacteria was considerably higher in defaunated animals. The higher bacterial growth efficiency in the absence of the protozoa in the rumen is probably related to the fact that protozoa engulf and digest bacteria (Coleman 1975 cited by Nguyen et al 2005). This is supported by Leng (1990), who discovered that removal of protozoa or a decrease in protozoal density in the rumen can be expected to increase ruminant production under most feeding conditions pertaining to roughage fed ruminants. Diaz et al (1993) found that using Sapindus saponaria as a defaunating agent in mature tropical crossbred sheep reduced protozoal population (84%), total viable bacteria, and increased cellulolytic bacteria and fungi in a treatment which included 50 g of S.saponaria compared with the control (0 g of S.saponaria), due to a reduction in ruminal protozoal numbers. Therefore, effects of saponins and/or condensed tanins on overall ruminal fermentation were in good agreement with the studies discussed above. It was indicated that MSP could be used as a defaunating agent, especially in straw based feeding.

Effect of MSP, SFO and CO supplementation on volatile fatty acids production

As shown, there were no significant effects (P>0.05) of feeding level of MSP, SFO and CO on TVFA production and butyric acid, except for acetic acid, propionic acid, and acetic acid to propionic acid (C2/C3) ratios (P<0.05). Supplementation of SFO and CO resulted in changing acetate and propionate production and decreased acetate, thus lowing the C2/C3 ratio. The results are similar to McGinn et al (2004), who reported that adding sunflower oil to the diet clearly decreased ruminal fermentability of the fiber, as evidenced by lower acetate concentration, higher propionate concentration, and a lower acetate:propionate ratio. The result is in agreement with Church (1976), who pointed out that adding fat to diets also influenced the pattern of rumen fermentation and resultant VFA production. Most evidence indicated that there was likely to be a reduced percentage of acetate.  Numerous studies have been carried out on the effects of supplementation of tannins and/or saponins on VFA production, such as from Yucca Schidigera (Hristov et al 2004), Sapindus saponaria, (Diaz et al 1993) and with alfalfa root (Klita et al 1996). Hristov et al (1999) and Hess et al (2003) found a significant increase in propionate production in studies with both animals and in vitro trials, respectively. Moreover, effects of saponins on higher propionate and reduced acetate to propionate (C2/C4) ratio have been found to vary with diets and applications. Ngamsaeng and Wanapat (2005) conducted an in vitro study by using CT and/or CS concentrations in local plants and reported that the proportion of propionate production was slightly higher and C2/C3 ratio was lower in the group which contained CT than without CT. The effect of CT on TVFA and molar proportions of individual VFA could be due to reduced protozoal and increased bacterial populations, since acetate and butyrate are the major fermentation end-products of protozoa (Jouany 1994). Therefore, the molar ratio of acetate: propionate has been used to evaluate the substrates. Rapidly fermentable carbohydrates yield relatively higher propionate compared to acetate, and the reverse takes place when slowly fermentable carbohydrates are incubated (Makkar et al 1995). Steve (2001) reported that under optimal rumen fermentation conditions, the acetate to propionate (C2/C3) ratio should be greater than 2.2, and high levels of acetate can indicate a high fiber, low fermentable carbohydrate ration. High levels of propionate acid can indicate reduced fiber digestion and acidosis in cattle. The average values of acetate to propionate (C2/C3) ratio in the present study were 2.6 to 3.2, in which lower ratio was influenced by supplementation of MSP and with oil.

Effect of MSP, SFO and CO supplementation on methane production (CH₄)

As shown, the mean value of methane (CH₄) production in the rumen was significantly lower (P<0.01) with supplementation of MSP, SFO and CO than CON group. The results from this study may due to the condensed tannins from MSP, as tannins have been found to decrease methane inhibition, which is beneficial for reducing energy loss in the form of methane. Many types of forage which contain condensed tannins have been shown to decrease methane production, both in vivo and in vitro. Tannins present in Callindra calothyrus reduced nutrient degradation and methane release per gram of organic matter degraded in in vitro experiments with rumen simulation technique apparatus (Hess et al 2003). A decrease in NDF digestion (Dohme et al 1999) and a decrease in protozoal numbers (Lovett et al 2003; Machmüller et al 2003) have been identified as explanations for the reduction in CH₄ emissions after the inclusion of CO in the diet. Ruminal ciliated protozoa rely on an H₂-producing fermentation process that is inhibited by a high concentration of H₂. A symbiotic relationship with ruminal methanogens (Finlay et al 1994) has been established to allow an interspecies H2 transfer, thereby lowering the concentration of H₂ for the ciliated protozoa. Therefore, less H₂ is available for the formation of CH₄ after defaunation, and there is a decrease in symbiotic methanogen numbers; however, a corresponding increase in free-living methanogens has been reported (Sharp et al 1998). The observed decrease in total ruminal VFA molar concentration also may explain some of the decrease in CH₄. A decline in ruminal VFA molar concentration is most likely the result of decreased ruminal VFA production, which has been linked with lower ruminal CH₄ output because of the decreased availability of H₂ in the rumen (Dohme et al 1999). Although not measured in this experiment, a direct toxic effect of CO on methanogens has been reported (Dohme et al 1999; Machmüller et al 2003), which would be expected to contribute to the decrease in CH₄ output. As shown in this experiment, CH₄ was significantly reduced by MSP and with oils.

Effect of MSP, SFO and CO supplementation on voluntary feed intake

Roughage (RS and RZG), concentrate and total dry matter intakes in terms of kg/d and %BW in cattle were significantly different among treatments (P<0.05). Total DMI was highest in MSP100 and lowest in MSP200-SFCO (15.12 and 13.23 kg/hd/d, respectively). The results agree with Hristov et al (1999), Eryavuz and Dehority (2004) and Mader and Brumm (1987). Diaz et al (1993) and Klita et al (1996) demonstrated that high levels of saponins and/or tannins in diets resulted in decreased apparent digestibility, especially of N. Tannins are known to decrease protein degradability by complexing with feed protein, which may lead to inhibition of protein degradation in the rumen by the high concentrations of condensed tannins. On the other hand, Allen (2000) found that adding fat in the diet increased energy but reduced feed intake. A decrease in DMI from the inclusion of CO has been widely reported (Sutton et al 1983; Dong et al 1997; Machmüller and Kreuzer 1999; Lovett et al 2003). Jordan et al (2004) reported a linear decrease in digestibility in response to increasing levels of CO. However, no significant effect on digestibility was observed up to and including 250 g of CO/d (2.7% DMI). Chantaprasarn and Wanapat (2005) reported that, supplementing sunflower oil in dairy cattle diets tended to lower DMI in lactating dairy cows.

Effect of MSP, SFO and CO supplementation on nutrients digestibility

As shown, apparent digestibilities of DM, OM, CP, NDF, ADF and EE were not affected by treatments. Supplementation of MSP with 3% sunflower oil and 3% coconut oil in this study did not affect nutrient digestion but had an effect on nutrient intake (P<0.05). Normally the diet of lactating dairy cows typically contains 4 to 5% fat, and if higher than 6-7 % would affect rumen microbial fermentation (Jenkins 1993; Doreau et al 1997; NRC 2001). On the other hand, Church (1988) stated that in practice 2-4 % fat is commonly added to diets for lactating dairy cows and did not alter apparent ruminal DM, NDF and ADF digestibility. However, increasing sunflower oil and coconut oil in the diet tended to lower digestion coefficients. Therefore, adding oils at high level to the rumen caused a depression in digestibility of fibrous components (Church 1976; Preston and Leng 1987). High levels of CT and/or CS in this study tended to lower digestion coefficients. Similar, Diaz et al (1993) and Klita et al (1996) demonstrated that high levels of saponins and/or tannins in diets resulted in decreased apparent digestibility, especially of N. Tannins decreased protein degradability by complexing with feed protein, which may lead to inhibition of protein degradation in the rumen as a result of the high concentrations of condensed tannins (Ngamsaeng and Wanapat 2005).

Milk yield and milk composition

There were no significant effects (P>0.05) of feeding level of MSP, SFO and CO supplementation on milk yield and milk composition. Added SFO and CO tended to increase milk yield (FCM) and milk fat as compared to supplementation of only MSP or CON, respectively. Milk yield and 4% FCM were 10.2 10.4 11.5 10.8 and 10.9 11.1 12.3 11.6 kg/day for CON, MSP100, MSP200, MSP100-SFCO and MSP200-SFCO, respectively. These results agree with those of Amaral et al (1997), Avila et al (2000) and Ruppert et al (2004), who reported that adding fat to dairy cow diets increased milk yield. Chantaprasarn and Wanapat (2005) found that supplementation of sunflower oil in cassava hay based diets did not affect milk composition, and was similar with the results of LaCount et al (1995). Moreover, percentages of fat, protein, lactose, solids-not-fat and total solids in milk in this study were not affected by treatment. Supplementation of fat to dairy cows slightly decreased milk protein, although the magnitude of this depression in milk protein percent varies, but is usually up to about 0.3 % units (Schneider et al 1988).
 

Conclusions and recommendations

• Supplementation of MSP at 100 gDM/d with 3 % sunflower oil and 3% coconut oil could be beneficial for dairy cattle fed on a rice straw and ruzi grass (Brachiaria ruziziensis) based diet. The benefits were improvement of rumen ecology, especially increased bacterial population and reduced protozoa.

• Supplementation of MSP with 3 % sunflower oil and 3% coconut oil could also reduce concentrate cost, hence with higher economical return. Moreover, methane production in the rumen was reduced significantly when MSP, sunflower oil and coconut oil were supplemented.

• As MSP is a fruit by-product and can be simply collected it is therefore recommended to use as alternative feed strategy in ruminants, particularly for small-holder farmers, to improve feed efficiency and production.

• Further research relating to feeding fat by combining SFO and CO with MSP supplementation should be conducted in production trials to more clearly understand the mode of action of CT and/or CS and fatty acid on ruminant microbes, milk yield and milk quality, especially the conjugated linoleic acids (CLA).
   

Acknowledgements

The authors would like to express their most sincere thanks to all who have assisted and supported the research in this study, particularly the MEKARN project financed by SIDA-SAREC. We wish to thank to the farmer, Mrs. Nongyouw Kujapun for allowing the research to be conducted on her farm, providing dairy cows, facilities and housing. Appreciation is also extended to the Tropical Feed Resources Research and Development Center (TROFREC) of the Department of Animal Science, Faculty of Agriculture, Khon Kaen University for research facilities, laboratory and analyses. Appreciation is also extended to staff of the Milk Quality Control Laboratory of the Dairy Farming Promotion Organization of Thailand (DPO), Northeast Region, for milk quality analyses.
 

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