Evaluation of water spinach (Ipomoea aquatica) as a protein source for Ba Xuyen and Large White sows

Le Thi Men, Brian Ogle*, Vo Van Son and T R Preston**

Department of Animal Science, College of Agriculture, Can Tho University, Vietnam
ltmen@ctu.edu.vn
* Swedish University of Agricultural Sciences, Department of Animal Nutrition and Management, PO Box 7024, 750 07 Uppsala, Sweden
** TOSOLY, AA48 Socorro, Colombia

Abstract

Two on-station trials and a feeding experiment were conducted at the experimental pig farm, Can Tho University, to determine the intake and the apparent digestibility of fresh chopped and whole water spinach (WS) by pregnant sows. The effect on reproductive performance of feeding WS to local Ba Xuyen and Large White sows was also evaluated. The first (intake) trial included 6 multi-parity local Ba Xuyen and 6 Large White  sows. The sows were mated by AI with the same Large White boar. The trial was designed as 3 multiple Latin Squares with two diets for each breed as follows: 1 kg DM concentrate/day plus whole water spinach (WWS) ad libitum; 1 kg DM concentrate/day plus chopped water spinach (CWS) ad libitum.

For the Large White and Ba Xuyen sows, respectively, results were: fresh WS intake per sow/day, 7.3 and 6.1 kg (604 and 504 g DM) and % of DM intake from WS 37.6 and 33.4 % (P<0.01). Consumption of fresh CWS and WWS by pregnant sows was 6.9 and 6.4 kg/sow/day, respectively (DM intake 575 and 533 g/sow/day, respectively) and  % of DM intake from WS  36.4 and 34.7 % (P<0.01) for CWS and WWS,  respectively.

The digestibility trial included 3 local Ba Xuyen and 3 Large White sows in the first month of pregnancy, kept in individual cages and was a two-way random complete design with breed of sow as one factor and diet as the other factor. Each breed was given 3 diets in a 3*3 Latin Square design. The experimental diets were as follows: Ba Xuyen sows: 1.7 kg DM/day of a control diet (a concentrate based on local feed resources); 1.1 kg DM/day of the control diet plus 0.5 kg DM whole water spinach (WWS); 1.1 kg DM/day of the control diet plus 0.5 kg DM chopped water spinach (CWS).  Large White sows: 2 kg DM/day of the control diet; 1.3 kg DM/day of the control diet plus 0.6 kg DM WWS; 1.3 kg DM/day of the control diet plus 0.6 kg DM  CWS.

Apparent digestibility  (%) of WS was calculated by the difference method, and for pregnant Large White and Ba Xuyen sows of fresh CWS and WWS , respectively, was 77.7 and 65.1% for DM and 77.9 and 73.8 % for CP (P<0.01). The apparent digestibility (%) for CWS and WWS diets, respectively, was for dry matter (DM) 68.4 and 60.0, organic matter (OM) 76.0 and 71.5, crude fibre (CF) 71.6 and 70.8 and for nitrogen free extract (NFE) 91.3 and 85.6 (P<0.01).

The reproduction experiment included 6 Large White and 6 Ba Xuyen sows, and was designed as a 2*2 factorial with two breeds and two diets: Gestation period for Ba Xuyen: 1.7 kg DM daily of a control diet based on local feed resources; 1.1 kg DM/day of the control diet plus 0.5kg DM of CWS; Gestation period for Large White: 2 kg DM/day of the control diet; 1.3 kg DM/day of the control diet plus 0.6kg DM  of CWS. In lactation the same concentrate was given as in gestation, the daily amounts depending on litter size. Between 4-6 kg (fresh weight) of WS was given to the sows on the experimental diet.

The total litter weights at birth and at weaning were higher (P<0.05) for CWS sows. Total feed DM/kg piglet at birth, at 21 days and at 35 days were lower (P<0.05) for the CWS sows. The gross weight gain of the sows in pregnancy for the control group was lower (P<0.05) than for the CWS diet. The weight loss during the lactation period was 10.3 % for the control diet and 12.0 % (NS) for the CWS diet.  Mean piglet live weight at birth was 1.4 vs 1.0 kg, total litter weight 14.0 vs 9.5 kg and total feed DM/kg piglet 13.3 vs 16.8 (P<0.01) for the Large White and Ba Xuyen sows, respectively. The average gross gain in gestation of Large White sows was higher (P<0.01), but weight loss in lactation was higher (P<0.01) compared with the Ba Xuyen sows. 

Key words: Apparent digestibility, intake, piglet, reproductive performance, water spinach, sow breed

Introduction

The Mekong Delta is situated in the South of Vietnam and has a population of 22 million. It is the biggest of the two granaries of the country, accounting for about 50 % of the total national food production. The delta is about four million hectares of flat lowland plain with alluvial, acid and saline soils watered by the Mekong River and its canal networks (Nguyen Thi Kim Dong 2005). Most of the arable land is used intensively for rice cultivation or other crops throughout the year, and therefore large quantities of agricultural by-products are available as feed resources for livestock (Thong et al 1995). The delta region also has extensive water surfaces, which give opportunities for the widespread, year-round cultivation of water plants, especially water spinach.

Water spinach (Ipomoea aquatica) grows in marshy or wet sandy areas or floating on water in many parts of tropical regions in the world (Bruemmer and Roe 1979). The plant has creeping, hollow, water-filled stems and shiny green leaves, and large purple or white 2-5 cm long funnel-shaped flowers. It is used as human food and animal feed throughout Southeast Asia. Crude fibre and ash concentrations are around 12 % and 19 % of DM, respectively (Gohl 1975). The fresh leaves and stems contain 20 to 31 % CP on a DM basis (Bui Huy Nhu Phuc 2000; Ly Thi Luyen and Preston 2004; Prak Kea et al 2003; Chhay Ty and Preston 2006; Chhay Ty et al 2007; Phiny et al 2008; Sokha et al 2008), with balanced essential amino acids, i.e. 1.3 % lysine, 0.4 % methionine  and 1.1 % threonine  on a DM basis (Le Thi Men 2002 unpublished data,  2006). Water spinach is readily eaten by pigs and is a used as a feed resource throughout the Mekong Delta. It has been used successfully to replace part of the protein in a diet of sugar cane juice for breeding sows (Le Thi Men and Bui Hong Van 1994). 

An indigenous pig breed, the Ba Xuyen, which has traditionally been reared in the remote areas of the Delta, has a number of advantages in these areas as it survives well under the harsh environmental conditions and on poor quality feeds. It is used for breeding, and the sows are usually mated with an exotic boar to produce crossbred fattening pigs. The aims of the study were:

• To determine the intake and apparent digestibility of chopped and whole water spinach (WS) by Ba Xuyen and Large White sows

• To evaluate the effects on reproductive performance of feeding WS to pregnant Ba Xuyen  and Large White sows

Materials and methods 

Effect of chopping water spinach on intake and total tract digestibility by pregnant Ba Xuyen and Large white sows

Experimental design and pigs

An intake study with pregnant sows fed whole and chopped water spinach was carried out at the experimental pig farm of Can Tho University. The experimental animals were 6 multi-parity local Ba Xuyen (6^th litter, average live weight 180 kg) and 6 Large White (5^th litter, average live weight 202 kg) sows. The sows were mated with the same Large White boar by AI, and were then placed in individual concrete-floored pens. The trial was designed as 3 multiple Latin Squares with two diets given to each breed. The dietary treatments were:

• 1 kg DM concentrate/day (a concentrate based on local feed resources)  plus whole water spinach (WWS) ad libitum

• 1 kg DM concentrate/day plus chopped water spinach (CWS) ad libitum

The WS was chopped by hand into 4-5 cm lengths. The trial was divided into 2 periods, including 2 days for adaptation and 2 days for collection of data per period. The amounts of water spinach offered and refused were recorded to estimate the intake, and the chemical composition (DM, crude protein, crude fibre, ether extract and ash) was determined by standard methods (AOAC 1990). 

Digestibility trial with sows

Based on the results of the intake of water spinach, diets were formulated for the digestibility trial. The experimental animals were 3 local Ba Xuyen and 3 Large White sows in the first month of pregnancy, kept in individual cages. The trial was a two-way random complete design with breed of sow as one factor and diet as the other factor. Each breed was given 3 diets in a 3*3 Latin Square design. The experimental diets were as follows:  

Ba Xuyen sows:

• 1.7 kg DM/day of a control diet (a concentrate based on local feed resources)

• 1.1 kg DM/day of the control diet plus 0.5 kg DM whole water spinach (WWS) fed separately

• 1.1 kg DM/day of the control diet plus 0.5 kg DM chopped water spinach (CWS) fed separately  

 Large White sows:

• 2 kg DM/day of the control diet

• 1.3 kg DM/day of the control diet plus 0.6 kg DM whole water spinach (WWS) fed separately

• 1.3 kg DM/day of the control diet plus 0.6 kg DM chopped water spinach (CWS) fed separately 

The daily allowances were based on the mean live weights of the two breeds. The concentrate was given first, twice a day, and the fresh chopped or whole WS was available throughout the day. The experimental period was 7 days for adaptation and 5 days for collection of faeces. During the experimental period intakes of the control diet and WS were measured daily by weighing amounts offered and refused. Samples of water spinach, including the refusals, were analysed immediately for DM in a microwave oven. The sub-samples for later analysis were prepared by drying in an oven at 60°C, ground and stored in a fridge at 4°C. The total amount of faeces was collected and weighed every day. An aliquot of 10 % faeces/sow was stored in a freezer at –10°C and at the end of each period was mixed thoroughly, and representative samples taken for analysis. DM and N were determined on the fresh samples. A sub-sample of faeces was dried at 60°C in a drying oven for analysis of ether extract, crude fibre and ash, determined by AOAC methods (1990).  

Effect of feeding WS on the reproductive performance of Ba Xuyen (BX) and Large White (LW) sows

Experimental design and pigs

The experiment included six LW and six BX sows and was designed as a 2*2 factorial with two breeds and two dietary treatments. The sows were allocated at random to one of two treatments three weeks after mating with the same Yorkshire boar by AI.

Diets and feeding

The daily allowances were based on the mean live weights of the two breeds.

Ba Xuyen:

•   1.7 kg DM daily of a conventional diet based on local feed resources (control)

•  1.1 kg DM/day of the control diet plus 0.5 kg DM chopped water spinach (CWS) fed separately

Large White:

•  2 kg DM/day of the control diet

•  1.3 kg DM/day of the control diet plus 0.6 kg DM chopped water spinach (CWS) fed separately 

The sows were kept in individual concrete-floor pens. Three weeks after mating, the sows were fed the experimental diets, and were given the restricted amount of concentrate twice daily in the morning and afternoon, and then fresh clean chopped water spinach three times per day. The amount of feed and WS consumed was recorded. The lactating sows were fed increasing amounts of concentrate according to the litter size (2 kg/sow plus 0.5 kg/piglet). Sows were given only very small amounts of WS (1-2 kg/d) for the first two weeks after farrowing, as they were reluctant to consume larger amounts. Then they were given 4-6 kg of fresh WS divided between three occasions each day, the amount being restricted because of fears of piglet diarrhoea. Piglets were given the same complete creep diet for each treatment. 

The parameters recorded were:

•   Litter size at birth, 21 and 35 days

•   Litter weight at birth, 21 and 35 days

•   Piglet mortality

•  Total feed DM per kg piglet at birth, 21 and 35 days

•   Sow weight changes          

Statistical analysis

Data were analysed by ANOVA using the General Linear Model, and Tukey means separation in the Minitab Statistical Software version 13. 

Results and discussion 

Chemical composition of WS and dietary ingredients

Analytical data for the diet ingredients are in Table 1. 

Amino acid analysis showed that most of the important essential amino acid concentrations in WS are higher than those of the ideal protein (ARC 1981), and superior to the balance of amino acids in soya bean meal, particularly with respect to methionine, threonine, isoleucine and valine (Table 2) 

Water spinach intake and total tract digestibility by pregnant Ba Xuyen and Large White sows

Intake of WS by pregnant sows

Effect of breed

Fresh WS intake (kg/sow/d) for the Large White and Ba Xuyen sows was significantly different (P<0.01) between the 2 breeds (Table 3).

Even adjusted for live weight, the amounts consumed by the Large White sows were higher (P<0.01) than for the Ba Xuyen breed, which implies that this improved breed has successfully adjusted to the environment of the region. The sows consumed around 6-7 kg (500-600 g DM) of fresh WS/day, plus 1 kg DM of concentrate. The proportions of the total DM intake from WS were higher (P<0.01) for the Large White than for the Ba Xuyen sows. These results can be largely explained  by the fact that the Large White sows, with a higher live weight (202 kg) than the Ba Xuyen (180 kg) sows, were fed the same limited level of concentrate (1 kg DM/d). The high intakes of WS showed that it was very palatable for the sows.

Effect of chopping WS

Fresh and DM intakes, and % of DM intake of CWS, were higher (P<0.01) than of WWS (Table 4), probably due to the decreased bulk of the CWS.

This was not unexpected, as it is well known that reducing particle size increases the consumption of high fibre feeds. Although the relative amounts of leaves and stem in the refusals were not determined , it was observed  that the proportion of  stems in the refusals  was higher than in the whole plant. This was confirmed by the chemical analysis, as the crude protein of the CWS refusals (20.5 %) was lower than in the whole plant (26.7 %) (Table 5), indicating that the sows had selected the leaves before the stems. However, it was observed that a few individual sows preferred the crisp stems.     

Total tract digestibility of water spinach by pregnant sows

Effect of breed

Apparent digestibility (%) of DM (83.0 vs 80.0) and crude protein  (84.8 vs 81.0) was  higher (P<0.05) for Large White sows than for the Ba Xuyen breed, but the values for OM, crude fibre and NFE digestibility were not significantly different between the two breeds.  

The digestibility of the WS was calculated by the difference method (Table 7) using the formula: 

100*Dig coeff. of mixed diet = (100-X)*Dig coeff. of concentrate  + (X)*Dig coeff. of WS

Where X is percent of WS in the diet, DM basis 

The apparent digestibility coefficients of water spinach were for DM 77.7 vs 65.1 %, and for crude protein 77.9 vs 73.8 %, for Large White and Ba Xuyen, respectively,  the difference being higher P<0.01) for the Large White breed (Table 6).    

Effect of diet

The total tract apparent digestibilities of DM, OM, CF and NFE were higher (P<0.01) in CWS than in WWS. Crude protein digestibility was similar for the two physical forms of WS (Table 7).

The generally higher apparent digestibility of the nutrients in CWS was probably a result of the physical disruption of the cell walls of the plant by chopping, and the increased surface area exposed to enzyme action. Bitende (1994) reported that physical preparation of feeds to improve digestibility includes chopping, chaffing, grinding or cooking. Chopping and grinding are common processes of communition for roughage. Coarse fibrous particles may be retained in the caecum longer than more finely ground particles of the same fibre source. Unchopped roughage can also result in increased DM digestibility due to selection of the better components of the diet i.e. leaves versus stems. However, in our second trial the sows were offered the same limited amount (30 % of dietary DM) of CWS and WWS, so there were no refusals by the sows and no selection of the leaves in the WWS treatment. Consequently most nutrient digestibilities were higher for the chopped water spinach than for the whole plant.   

Effect of feeding water spinach on the reproductive performance of Ba Xuyen and Large White sows

Chemical composition of diets and ingredients

The basal diet for breeding sows included conventional feeds, such as broken rice, rice bran, soybean extract, fishmeal, and premix (Table 8a).

The chemical composition of the basal diet is shown in Table 8b.

The WS had an average DM content of 8.3 %, and nutrients as % of DM were: CP (26.7), CF (15.5) and ash (14.1). Ca and P contents were 0.90 and 0.50 %, respectively (Table 1). Analysis of the amino acids showed that most of the important essential amino acid concentrations in WS were higher than those of the ideal protein (ARC 1981). The balance of essential amino acids in the basal diet was also similar to that of the ideal protein, except that threonine and isoleucine levels were lower (Table 2).  

Feed intake

Pregnancy

Most of the pregnant sows consumed CWS without any refusals, except that two Ba Xuyen sows left around 250 g fresh CWS/day in the week before farrowing. For each breed CWS replaced 30 % of the DM of the basal diet.

Lactation

There were no refusals noted when 15 % CWS (DM basis) substituted for the basal diet to sows.   

Reproductive performance of the sows

Effect of diet

Litter weights at birth, 21 and 35 days were higher (P<0.05) for sows fed the CWS (Table 9).

Vestergaard and Danielsen (1998) stated that there are nutritionally induced effects on reproductive performance, especially by vitamin A, which is very important for fertility. Levels of vitamin A are high in green plants, and it is possible that active levels in the control diet were too low, as this vitamin is rapidly destroyed in hot, humid conditions. Comparing the colostrum and milk from ten sows on pasture and ten sows in dry lot, it was reported that mean vitamin A levels (as retinol) tended to be higher for sows on pasture (Bowland 1949). 

Welfare indicators when pregnant sows are fed only concentrate diets are often very low, as the sows are usually hungry and this causes stress. By providing WS, the bulkiness of the diet is increased and the sows should be less hungry and therefore less stressed. In the present study, the control sows were extremely noisy and obviously stressed before feeding time, while the sows given WS were generally calm and contented. These observations agree with Mroz (1986), who concluded that feeding diets with a high fibre content will increase the time needed to consume the daily allowances and decrease competition between pen mates. The total gross weight gain of the sows in pregnancy was lower (P<0.05) on the control than on the WS diet but the mean net gains were not different. The weight loss during the lactation period was 10.3 % for the control diet and 12.0 % for the WS treatment (NS). This agrees with the conclusion of Vestergaard and Danielsen (1998) that high fibre diets increase the gut fill of the sows, leading to a large gross body-weight gain during the pregnancy period, but also to a larger weight loss at farrowing, when the food is changed to a standard lactation diet.  In our study, WS was not provided immediately post-farrowing. The higher total litter weight at birth of the CWS sows would also have contributed to their higher gross pregnancy weight gains.  

Effect of breed

Litter size at birth and weaning was similar for the two breeds. However, the Large White sows produced heavier piglets than the Ba Xuyen breed (Table 10).

The higher mean piglet birth weights would be mainly the result of the higher (by about 10 %) mature body weights of the Large White breed. As a result of the early commencement of eating of the crossbred piglets (LW*BX) and their higher creep feed consumption, piglet and total litter weights between two breeds were similar at the end of lactation. Net pregnancy live weight gains were almost identical for the two breeds, but lactation losses were higher (P<0.01) for the Large White sows (12.9 % of body weight) than for the Ba Xuyen sows (9.5 %). 
 

Conclusions 

•  Diets including fresh water spinach can be used effectively by breeding sows. 

  
  

•  Fresh chopped water spinach can replace 30 % of the DM of concentrate diets for gestating sows and 15 % of the diet of lactating sows of both local and exotic breeds, resulting in somewhat improved reproductive performance and welfare.

Acknowledgements 

The authors are grateful to the Swedish International Development Authority, Department for Research Cooperation (Sida/SAREC) for financing this study. We are also grateful to the College of Agriculture, Can Tho University, for use of their facilities. The Senior Author is thankful to her colleagues and assistants, Khang, Loan, Tam, Hau, Phuong, Duc, Huong and Binh for their help.

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Received 10 February 2010; Accepted 28 February 2010; Published 1 April 2010

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