Effects of sugar cane syrup on performance and digestibility of growing-finishing pigs

Nguyen Nhut Xuan Dung, Luu Huu Manh, Nguyen Ngoc Thanh Lam* and Toshihico Kamada**

Cantho University, Cantho, Vietnam
nnxdung@ctu.edu.vn
* CanTho College of Economics and Technology
** Tokyo University of Agriculture and Technology

Abstract

Twelve Yorkshire  pigs (initial live weight 20 ±1 kg), in a random complete block design with 4 replicates, were used in a growth and digestion study to determine the value of low levels of sugar cane syrup (SCS) at 0 (control), 4 and 6% as a supplement to the basal diet of maize and rice byproducts.  The trial lasted 3 months comprising a growth study and 5 days digestion trial at the end of the growing period.

The growth and feed conversion of pigs fed SCS were better than for the control, with no changes in back fat thickness. Apparent digestibility coefficients  of dry matter and protein were improved with inclusion of SCS.

Key words: back fat thickness, feed intake, plasma urea nitrogen

Introduction

Sugar cane juice is an energy-rich feed, which has been demonstrated to support high growth rates when fed as the basal diet of cattle (Sanchez and Preston 1980) and pigs (Mena el al 1981; Sarria et al 1990; Speedy et al 1991; Bui Hong Van and Le Thi Men 1992; Bui Huy Nhu Phuc 1993). Sugar can syrup (SCS) is an intermediate product in the production of crystalline sugar and is made from extracted juice of sugar cane, which has been evaporated to a concentration reflected in a Brix value of 62-67^o (equivalent to total sugars). ^. As fermentation is stopped at this concentration of sugars, it can be stored for certain periods prior to being processed into crystalline sugar. Takada et al (2004) found that rats fed diets that included 1% of SCS had improved live weight gain, while plasma urea nitrogen (PUN) and lysine-oxoglutarate reductase activity in liver, an enzyme that inhibits the lysine degradation, were decreased as compared with the control diet. At a level of 2 to 4% in the pig diet, SCS improved the live weight gain (Yamasaki et al 2005) and nutrient digestibility but also slightly reduced plasma urea nitrogen (Luu Huu Manh et al 2005).

Therefore, the present study was designed to investigate further the effect of graded levels of sugar cane syrup on performance, apparent digestibility, PUN and back fat thickness of pig during the growing and fattening periods.  

Materials and Methods

Experimental animals, treatments and design

Twelve Yorkshire pigs with initial live weight of 20 ±1 kg and two months of age were randomly allocated according to a complete block design with four replicates and 1 pig per replicate, and distributed into the three dietary treatments:

• Control: basal diet
• SCS4:  basal diet with 4% of sugar cane syrup
• SCS6: basal diet with 6% of sugar cane syrup

The pigs were housed individually pens following the experimental design and adapted to the condition of the experiment for 7 days.

Experimental diets

The main dietary ingredients were rice bran, ground maize, fish meal and soybean meal.  Sugar cane syrup (SC) was obtained from the local sugar cane mill, where the extracted sugar cane juice (Brix of 15-16o) was processed by liming and heating for two to three hours and allowed to settle in a sedimentation tanks to clarify. The clarified juice was evaporated and concentrated to a syrup (Brix of 65-67o). The diet formulations were divided into two phases, growing (12 to 50 kg) and finishing (50 to 90 kg). Feeds, diet formulations and composition are presented in Tables 1, 2, and 3, respectively.

Digestibility trial

The digestibility trial was conducted when the pigs reached approximately 50 kg (at the end of the growing phase). The collection period was 5 days;  feces were quantitatively collected daily and stored at -18^oC. At the end of the trial, sub-samples were taken, mixed and dried at 60^oC and store at 4^oC prior to analysis.

Data collection and management

The pigs were weighed at the start, every two weeks and at the end of the trial. Feed intake and refusals were recorded daily. Feeds were offered at close to ad libitum feeding at 9.00 h and 15.00 h and water was available throughout the experiment. At the end of the trial, back fat thickness was measured with an ultrasound device (Lenco Lean-meter) detected between the 10^th and 12^th ribs.

Chemical analysis

Feed samples were analysed in duplicate for dry matter (DM), ash, and ether extract (EE) according to the standard procedure of AOAC (1984).  For determining crude protein (CP = N x 6.25) of feces, fresh samples were analysed to avoid losing ammonia. Neutral detergent fibre (NDF) was analysed according to Robertson and Van Soest (1991), but instead of boiling for one hour, samples were incubated in the oven at 90^oC over night according to Chai and Udén (1998). Gross energy (GE) was determined by adiabatic bomb calorimeter. Blood samples were taken via external jugular vein at the end of the trial and placed in ice prior to centrifugation. Plasma was collected from blood and urea nitrogen (PUN) was analysed by enzymatic method using urease to produce ammonia and CO₂, the ammonia produced combines with 2-oxoglutarate and NADH in presence of GLDH to yield glutamate and NAD.        

Statistical analysis

All data were analysed by analysis of variance using the General Linear Model option of the Minitab software (version 13, Ryan et al 2000). The model used was the following:

Xij = μ + Ti + Bj+ e     

where,

Xij is the individual observation, μ the overall mean, Ti treatment effect (i=1 - 3); Bj block effect (j=1-4) and e is residual error. If the treatment effect was significant (P<0.05), differences between means were tested with the Tukey procedure of the Minitab software.
 

Results

Feed intake

During the growing phase, DM intakes were similar among diets (Table 4).  However, during the finishing phase, and for the overall period, the SCS4 and SCS6 pigs had a higher DM intake than the control pigs

Pig performance

During the growing phase, daily gain feed conversion were similar among diets. Whereas, during the finishing phase, and for the overall period, SCS4 and SCS6 pigs had better growth rates and feed conversion than the control pigs (Table 5). Back fat thickness was similar among diets, although with a tendency (P=0.20) to be slightly lower for SCS4 and SCS6 pigs than for the control pigs.

Digestibility and plasma urea nitrogen (PUN)

The apparent digestibility coefficients of DM and OM were generally high (Table 6) with higher values for SC4 and SC 6 pigs Protein digestibility tended (P=0.13) to be higher for the pigs fed the SC diets. PUN values increased with increasing level of SC in the diet.

Discussion

There is a paucity of studies in the literature on the use of sugar cane syrup for pigs, although many experiments have been carried out on the use of sugar cane juice and molasses (Sarria et al 1990; Mena el al 1981; Elliott and Preston 1981; Speedy et al 1991; Bui Hong van and Le Thi Men 1992; Bui Huy Nhu Phuc 1993). The similar in daily intake and daily gain obtained during growing phase in the present study may be explained by the fact that the experiment was started during rainy season; it was cold and humid, leading to coughing and diarrhea, particularly on the SCS6 diet. On the other hand, the increase in feed intake and daily gain of the SCS4 and SCS6 pigs during the finishing phase may be attributed to the sweet taste of SCS in these diets. Animals often prefer sweet tasting substances and consume palatable feeds in larger volume than feeds which are less palatable (Furudono et al 2005).

McDonald et al (1995) said that in short term feed regulation, glucose absorbed from the intestinal tract may cause a reduction in feed intake, but the control feeding centre in pigs is not sensitive as that in poultry and other animals. In an experiment on rats, Wilson and Heller (1975) concluded that blood glucose level per se is not an important feedback parameter in long-term control of feed intake. In the present study, all diets were iso-energetic since SCS replaced broken rice. Therefore the supplementation of SCS did not increase dietary energy density.

The higher levels of DM and OM digestibility can be ascribed to the higher sucrose content in SCS, that is known to be 100% digestibility (Ly et al. 2000). Fuller et al (1977) found that a high amount of available carbohydrate in the diet increases nitrogen retention and inhibits protein degradation (Fulks et al 1975).

The increased live weight gain in pigs supplemented with sugar cane syrup can be explained by the associative effects of high total DM intake and improved digestibility of the SCS diets. These results are in agreement with Yamasaki et al (2005) and Luu Huu Manh et al (2005), who also found that the pigs grew faster with SCS supplements.  

Recently, plasma urea nitrogen (PUN) has been widely used to evaluate protein status of animals (Kohn 2005). Manh et al (2005) reported that SCS reduced PUN in growing pigs. According to Eskeland (1974), glucose is the most effective energy source for nitrogen formation in sheep and glucose results in increasing nitrogen retention in man (McNair 1960; Forse et al 1990). Glucose decreases net protein breakdown, and thereby reduces nitrogen excretion and thus improves nitrogen balance (Howard 1987). However, the PUN in our experiment tended to increase with increasing sugar cane syrup in the diets. Possible reasons are that the fish meal used in higher concentrations in the SC diets could have contained high amounts of non-protein nitrogen. Also the blood samples were taken in the pigs at the time of slaughter; while protein deposition is relatively higher in the period before the pigs reach 45 kg live weight (McDonald et al 1995).

Back fat thickness is one of criteria to evaluate the effect of the diet; it is interesting to note that Fernandez et al (1979) and Mena et al (1981) reported that pigs fed with a solution of glucose before slaughter had higher carcass yields.  Speedy et al (1991) and Camp (2003) also considered that sucrose improved growth performance, but did not affect carcass yield of pigs. Schumacher (1986) reported that sucrose in the diet improved dressing percentage and reduced fat thickness.

Conclusions

• When sugar cane syrup was used at low levels ( 4-6%) in pig diets based on maize and rice byproducts, growth rates and feed conversion were improved with no effect on back fat thickness.

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Received 2 November 2009; Accepted 23 May 2010; Published 1 August 2010

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