Parameters of digestion and N metabolism in Mong Cai piglets having free access to sugar cane juice and soya bean meal

Lylian Rodriguez, Thomas R Preston, Julio Ly^* and Nguyen Van Lai

Finca Ecologica, College of Agriculture and Forestry, National University, Thu Duc, Ho Chi Minh city, Vietnam
* Present address: Swine Research Institute, Carretera del Guatao km 1, Punta Brava, La Habana, Cuba

Abstract

The basal diet fed to "local" Mong Cai pigs (14-21 kg live weight) consisted of fresh sugar cane juice and four levels of soya bean meal estimated to provide protein levels of of 4, 8, 12 and 16% in dry matter. The quantities of cane juice and soya bean meal were adjusted according to live weight, based on an anticipated total intake of dry matter of 4.4% of live weight. The experimental design was a 4*4 Latin square with periods of 8 days, four for adaptation and 4 for collection of faeces and urine. The piglets were adapted to the soya bean meal for 2 weeks before being allocated to the treatments.

There was an almost linear response in nitrogen retention as the offer level of soya bean meal was increased. This was in marked contrast with the pig's behaviour as most of them refused to eat more than the equivalent of 10 g N per day in the form of soya bean meal.. Based on these observations, and the recorded data, it is proposed that a level of about 50 g/day of apparently digestible protein is adequate for growing Mong Cai pigs in the weight range of 10-20 kg.

Key words: Pigs, Mong Cai, sugar cane juice, soya bean meal, protein levels, digestibility, N retention

Introduction

The local breed of Mong Cai pigs seems to perform better than exotic (Large White) pigs on diets based on local resources (Rodriguez and Preston 1996). In the typical management system (Rodriguez et al 1996) of local indigenous breeds, such as the Mong Cai, the sows are often fed considerable quantities of "green plants" or are allowed to roam freely, scavenging for a wide range of natural and cultivated plants (vegetable wastes, grasses, weeds and water plants). Typical diets in the central region of Vietnam were found to contain less than 10% protein in dry matter (Nguyen Thi Loc et al 1997). Our recent observations (Rodriguez and Preston 1997) indicate that at least during the period of gestation and lactation Mong Cai sows perform well with protein levels not exceeding 50 g/day derived exclusively from duckweed (Lemna minor).

The following experiment was carried out to determine the response in digestibility and N retention parameters in Mong Cai pigs when fed increasing levels of soya bean meal, which is the conventional protein supplement used in "modern" pig production systems.

Materials and Methods

Location

The experiment was carried out at the Finca Ecologica on the University Campus (College of Agriculture and Forestry, Thu Duc District, Ho Chi Minh city). The area is close to sea level with a range of temperature from 24 to 38 C, and relative humidity in the range of 40 to 100%.

Animals

Four Mong Cai male piglets (14-21 kg) were bought at the local market. They were immediately put in a metabolism cage made from bamboo fixed to a wooden frame in a composite unit (2.8 m length and 0.9 m wide) for 4 animals (Rodriguez and Preston 1996). The floors were composed of lengths of bamboo poles of 1-2cm diameter with 1 cm spacing to facilitate passing of the faeces. The cages were fitted with automatic water drinkers and the feeds were offered in ceramic dishes. Area per pig was 0.5m (70*70cm) and the divisions of half bamboo sections were 50cm high. The faeces collector, suspended 5cm below the floor, was a rigid sheet of plastic net used traditionally for sealing windows against entrance of insects. Urine fell through the net and was collected over a sheet of polyethylene suspended in the form of a shallow"V" with the lowest point emptying into a filter placed in a funnel suspended over a plastic bucket. The total cost of each unit for 4 animals (materials and labour) was US$35.00.

Experimental design and treatments

The basal diet consisted of fresh sugar cane juice and soya bean meal. The four treatments were offer levels of protein in the diet equivalent to 4, 8, 12 and 16% of protein in dry matter. The quantities of cane juice and soya bean meal were adjusted according to live weight, based on an anticipated total intake of dry matter of 4.4% of live weight (Rodriguez and Preston 1996) . The experimental design was a 4*4 Latin square with periods of 8 days, four for adaptation and 4 for collection of faeces and urine. The piglets were adapted to the soya bean meal for 2 weeks before being allocated to the treatments.

Diets and feeding system

Sugar cane stalks were purchased from local farmers and crushed every morning using a 3 roll mill and a local Vietnamese (Chinese yellow breed) lactating cow to provide traction. The soya bean meal was purchased in the local market.

The daily quantities of sugar cane juice and soya bean meal were weighed each morning and fed separately in small amounts 6-8 times per day in order to avoid wastage. However, on the 12 and 16% offer level the amounts eaten were much less than the planned quantities. Mixing the soya bean meal with the cane juice enabled higher intakes to be obtained but these were still less than the intended levels. This action proved to be counter-productive as it created complications in recording of the residues and data were lost because of this. The pigs had free access to water from automatic drinkers strategically located outside the cages to avoid leaks into the faeces and urine containers.

Measurements

During the experimental period intakes of sugar cane juice and soya bean meal were measured daily (by weighing amounts offered and refused). Samples of sugar cane juice offered and residues were collected daily and the Brix measured (% total soluble solids) with a hand refractometer. pH was also recorded as an indicator of fermentation. The juice residues were what remained in the bucket used to dispense this feed. In contrast, the residues of soya bean meal were mainly what was recovered from the ceramic dish in which the supplement was offered. Samples of soya bean meal offered were analysed for dry matter and nitrogen. Dry matter was determined by microwave radiation until constant weight as recommended by Undersander et al (1993). Nitrogen was determined by the standard Kjeldahl method. The nitrogen in the cane juice was determined on a single sample as previous experience (Du Than Hang et al 1997) indicated that variation among samples was minimal and so low as to be almost insignificant.

Urine was collected and weighed daily. 4N H₂SO₄ was used to keep the pH below 4 in order to preserve the N. An aliquot of 10% of the total daily quantities per piglet were stored in one plastic container per animal until the end of the period when a representative sample was taken to analyse for N. Faeces were collected and weighed daily. The total amount of faeces/piglet was stored in a freezer (-18C) and at the end of the period was mixed carefully by hand and representative samples taken for analysis of N (on the fresh faeces) and for dry matter.

Results and Discussion

Composition of diet ingredients

The composition of the soya bean meal and sugar cane juice is given in Table 1. The sample of soya bean meal used in period 1 had a lower than normal content of nitrogen, apparently due to adulteration with other ingredients. There was only a slight reduction in Brix and decrease in pH of the sugar cane juice during the day (compare values for offer and residue) thus the energy value could be assumed to have remained more or less constant during the 12 hour period during which the juice was offered.

Digestibility and N balance

The complete data are in annex 1. The pigs on the treatments with the two highest levels of soya bean meal did not consume the quantities offered, the maximum intake stabilizing at about10 g/day of N from the soya bean meal (Figure 1). In fact, for two pigs on the 16% offer level and one given the 12% level, the meal had to be mixed with the sugar cane juice to induce the pigs to eat it. As a result it proved to be impossible to determine accurately the composition of the residues. The data for these three animals were therefore omitted from the statistical analysis of variance and replaced with missing values for deriving means for the treatments (Table 2). The data for these pigs were excluded from the regression analysis.

The high values for apparent digestibility of dry matter and nitrogen are similar to those reported in earlier studies with diets based on sugar cane juice (Rodriguez and Preston 1996; Du Thanh Hang et al 1997). In view of the variation within and between treatments in the intake of the soya bean meal, regression analysis was used to relate N balance with protein supply (Figure 2).

The best fit was a quadratic equation:

Y = -1.85 + 0.143X - 0.00042X*X
r² = 0.86

relating the "consumed" apparently digestible protein (X=g/day) and the N retained (Y=g/d). According to this equation N retention would be expected to increase at levels of protein supply beyond those used in the present study. This is in contrast with the observed responses of the pigs and their refusal to eat the indicated amounts of soya bean meal even, in some cases, at the 12% protein level.

Based on these observations it is proposed that the optimum daily allowance of digestible protein for Mong Cai piglets in the weight range 10-20 kg is about 50-60 g/day. This compares favourably with the recommendations of Fuller (1988) for "unimproved" pigs in the tropics of comparable live weight (Figure 3).

Conclusion

There was an almost linear response in nitrogen retention as the offer level of soya bean meal was increased. This was in marked contrast with the pig's behaviour as most of them refused to eat more than the equivalent of 10 g N per day in the form of soya bean meal.. Based on these observations, and the recorded data, it is proposed that a level of about 50 g/day of apparently digestible protein is adequate for growing Mong Cai pigs in the weight range of 10-20 kg.

Acknowledgements

Acknowledgement is made to SAREC (Swedish Agency for Research Cooperation with Developing Countries) for financial support for the study visit in Vietnam of Dr Julio Ly. Nguyen Van Lai is a student in the Master's course on Sustainable Use of Natural Renewable Resources, an activity of the University for Tropical Agriculture (UTA), supported partially by the Danish Embassy in Hanoi.

References

Du Thanh Hang, Nguyen Van Lai, Ly J and Rodriguez D 1997 Nitrogen digestion and metabolism in Mong Cai pigs fed sugar cane juice and different foliages as sources of protein. Livestock Research for Rural Development (9) 2:45-48

Fuller M F 1988 Nutrition and feeding. In: Pig productivity in tropical and sub-tropical regions. FAO; Rome

Nguyen Thi Loc, Preston T R and Ogle B 1997 Protein supplementation of traditional diets for crossbred pigs under village conditions in Central Vietnam. Livestock Research for Rural Development (9) 2:8-11

Rodríguez Lylian and Preston T R 1996 Comparative parameters of digestion and N metabolism in Mong Cai and Mong Cai Large White cross piglets having free access to sugar cane juice and duck weed. Livestock Research for Rural Development (8) 1: 72-81

Rodríguez Lylian, Preston T R and Dolberg F 1996 Participatory Rural Development: "Experiences in Binh Dien and Xuan Loc Villages in Central Vietnam. Livestock Research for Rural Developement (8) 2:1-39

Rodríguez Lylian and Preston T R 1997 Alimentación de cerdos criollos con recursos locales; experiencias en el Sureste de Asia con jugo de caña, Lemna minor y hoja ensilada de la yuca. In: V Seminario-Taller Internacional "Sistemas Sostenibles de Producción Agropecuaria" and Primer Seminario "Internacional Palmas en Sistemas de Producción Agropecuaria para el Trópico" 31 July to 3 August 1997. CIPAV Foundation, Cali, Colombia (Electronic version)

Undersander D, Mertens D R and Thiex N 1993 Forage analysis procedures. National Forage Testing Association. Omaha pp 154

Received 18 August 1997

Annex 1: Parameters of intake, digestion and N retention for individual pigs

mv Missing values fitted in analysis of variance. Data for these pigs were not included in the regression ananlysis

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