| Livestock Research for Rural Development 9 (2) 1997 | Citation of this paper |
University of Tropical Agriculture, Thu Duc, Ho Chi Minh City
*Instituto de Investigaciones Porcinas, Carretera del Guatao Km 1, Punta Brava, La
Habana, Cuba
Growing Mong Cai pigs (10-14 kg live weight) were used in a 4*4 Latin square arrangement of 4 treatments, which were: ensiled cassava leaves, fresh foliage of cowpea, fresh duckweed, and silage made from a mixture of cassava and trichantera (Trichantera gigantea) leaves. These were given as the sole protein source in diets in which fresh sugar cane juice was the source of energy.
The intake of leaves, as percent of the total dry matter, ranged from 4% (cowpea) to 30% (ensiled cassava leaves). The digestibility of diet dry matter decreased with increase of leaves in the diet: from 96% (4% of leaves in diet dry matter) to 86% (30% of leaves in diet dry matter). On the basis of the regression of digestibility on percent leaves in diet dry matter it was estimated that the apparent dry matter digestibility of the leaves was on average 77%. N retention increased linearly as the proportion of leaves in the diet increased and was highest for ensiled cassava leaves.
Ensiled cassava leaves appeared to be the most palatable (highest N retention) of the foliages followed by duckweed. The fresh cowpea foliage was not liked by the Mong Cai pigs.
In the central region of Vietnam, the traditional protein sources are expensive. Duckweed and leaves of cassava and trichantera (Trichantera gigantea) and cowpea foliage are alternative sources of protein which are locally available. These feeds can be produced by the small scale farmer using family labour. The protein content of these potentially useful feed resources is relatively high.
The aim of this research was to contribute some information on the nutritive value of non-conventional and local feeds for pigs. The feed resources that were evaluated were: ensiled cassava leaves, fresh foliage of cowpea and duckweed, and silage made from a mixture of cassava and T. gigantea leaves. These were given as the sole protein source in diets in which fresh sugar cane juice was the source of energy.
The experiment was carried out in Finca Ecologica on the campus of the University of Tropical Agriculture, Thu Duc district in Ho Chi Minh City.
Four Mong Cai male pigs (10 - 14 kg live weight) were used.
The cages were made of bamboo (2.8 m length and 0.9 m wide) for 4 animals in separate compartments in which the pigs could move freely according to the suggestions of Rodríguez and Preston (1996). The cages were fitted with automatic water drinkers. Plastic netting suspended 5 cm below the floor served to collect the faeces. Urine passed through the net and was collected over a sheet of polyethylene leading to a filter placed in a funnel suspended over a plastic bucket.
Cassava leaves were ensiled with 5% of "A" molasses; the mixture of leaves of cassava and trichantera (85:15) were also ensiled with 5% molasses. Storage was in 50 litre plastic bags which were pressed and the air extracted with a vacuum pump, prior to sealing.
This was a 4*4 latin square arrangement for four treatments:
These were given as the sole protein source in diets in which fresh sugar cane juice was the source of energy. The composition of the feeds is given in Table 1. Each experimental treatment was for 10 days; the first 5 days for adaptation; the last 5 days for collection of faeces and urine.
During the experimental period, records were kept of feed offered and refused. Faeces
and urine were weighed daily. Samples of sugar cane juice, the foliages offered and the
residues were collected daily to measure the dry matter and the N content. Urine was
collected over H2SO4. 10 N to keep the pH below 4 in order to
preserve the N. The faeces were stored in a freezer (-18 oC) and at the end of
the period were thoroughly homogenized, pH measured with a glass electrode and
representative samples taken for analysis of N (on the fresh faeces) and dry matter.
Samples of feed, urine and faeces were analyzed for N (AOAC 1990). Dry matter
determination in feed and faeces was by microwave radiation until constant weight
(Undersander et al 1993). Brix of the sugar cane juice (total dissolved solids) was
measured with a hand refractometer.
Table 2 shows the data on the faecal indices. Duckweed caused a highly significant increase in daily faecal output of fresh material (P<0.05) and water (P<0.05). This was due to a very low concentration of dry matter in the faeces of the pigs receiving this supplement (18.2%; P<0.05). There were no significant differences among the diets containing ensiled cassava leaf. These faecal ouput data are comparable to those found by Ly et al (1996) in pigs fed sugar cane "B" molasses. On the other hand, a very low daily faecal output of fresh material and water was observed with the cowpea foliage. In fact, fresh cowpea was not liked by the Mong Cai pigs, and therefore a verly low voluntary intake was the primary cause of the unexpected faecal indices found in this treatment.
There were significant differences in faecal pH (P<0.01) among treatments but all reflected the excretion of alkaline end-products of digestion. A trend was observed of watery faeces to be significantly correlated with lower values of pH in faeces (r2 = 0.79; P<0.05).
Digestibility of the dry matter was high for all diets (Figure 1) and negatively related with the proportion of the diet consumed as leaves:
Y= 94.4 - 0.171 X; r2 = 0.40.......(1)
where X is percent of diet dry matter as foliage. Rodriguez and Preston (1996) reported a
similar relationship with Mong Cai pigs fed sugar cane juice and duckweed.
Y = 96.9 - 0.356X; r2 = 0.69........(2)
The predicted dry matter digestibilities of the forage component of the diet was 77% from our data compared with 61% using the equation derived by Rodriguez and Preston (1996). The implication from this comparison is that the ensiled cassava leaf (accounting for almost half of the forages used in our experiment) has a higher dry matter digestibility than duckweed. Nitrogen retention increased linearly with increasing N intake (Figure 2) according to the equation:
Y = -0.871 + 0.321X.....(3)
The corresponding equation for sugar cane juice and duckweed, calculated from the data of
Rodriguez and Preston (1996), was:
Y = -0.565 + 0.422X .........(4)
The higher value of the "X"coefficient in the equation (4) implies that the
biological value of the protein in duckweed may be superior to the average of the forages
used in our experiment.
The results of this experiment indicate that:
AOAC 1990 Official Methods of Chemical Analysis. Association of Official Analytical Chemists. 15th edition. Arlington
Ly J, Lon-Wo E and Castro M 1996 N and energy balance in pigs fed sugar cane molasses diets and natural zeolites from different deposits. Cuban Journal of Agricultural Science 30;287-293
Rodriguez L 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 duckweed. Livestock Research for Rural Development. Volume 8, Number 1: 72-81
Undersander D, Martens DR and Thiex N 1993 Forage
analysis procedures. National Forage Testing Association. Omaha pp 154
Received 1 May 1997