Effect of supplementation with tropical protein-rich feed resources on rumen ecology, microbial protein synthesis and digestibility in swamp buffaloes

Suphawat Joomjantha and Metha Wanapat

 Tropical Feed Resources Research and Development Center, Department of Animal science,
Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002,Thailand.
jyjoe28@hotmail.com

Abstract

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

Key words: cassava hay; digestibility; local feed resources; Phaseolus calcaratu; ruminants; swamp buffalo; sweet potato vine; urinary purine derivatives; volatile fatty acid

Introduction

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.
 

Materials and methods

Location

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%.

Animal, experimental design, dietary treatments and feeding

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

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)

Data collection, chemical analysis and sampling

Weight monitoring

The live weight of each animal was determined in the morning prior to feeding at the start and at the end of each period.

Feeds and fecal sampling

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 sampling

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).

Rumen fluid sampling 

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).

Statistical analysis

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
 

Results

Chemical composition of feeds

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.

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

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.

Volatile fatty acids (VFA) production

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.