| Workshop-seminar, 23-25 May, 2005, MEKARN-CTU |
| Contents |
Longan seeds were collected from longan pulp processing units in Hung yen province for this study. After collecting the Longan seeds, they were dried and ground at each unit. To investigate chemical composition and nutritive values of Longan seeds as a feed resource for ruminants, measurements were made of total phenolics; tannins and in vitro gas production assay. Nine milking goats were allotted 3 diets: LS-0, (Control) goats given concentrate feeds without Longan seed meal; LS-15, and LS-20 the concentrate feeds with 15 and 20% Longan seed meal.
Crude protein of Longan seed was similar to maize (9.06 in DM
basis), but NDF content was much higher than maize
(36.8%). Total phenols, tannins and condensed tannins were 5.86, 4.4 and
2.44%. Net gas production at 24 h of incubation was lower than for King grass (19.1 ml vs
37.0 ml), but when incubated with PEG 6000, gas
volume at 24 h increased to 24.8 ml. Concentrate intake and milk production of
the goats was reduced when Longan seed meal was included in the concntrate.
Longan trees are grown in large numbers in both northern and southern parts of Vietnam and longan fruit is a kind of very special food for human consumption and export. According to statistical data from Ministry of Agriculture and Rural Development (2002), total area for longan trees in Vietnam is about 31,200 ha. With this area, it is estimated that around 130 thousand tonnes of longan fruit could be produced yearly. Longan fruits are utilized in both fresh and dried form and nowadays, due to very high demand from China, longan fruit exportation has quickly increased. In order to increase longan fruit production for exportation, the fruits now are processed to get dried pulp. In Hung yen province (it is about 40 km from Hanoi) there are 600 longan processing units with capacity of 1-2 tonnes of fruit/day. With high proportion of skin and seed, longan by-products are estimated at over 30 thousand tonnes/year. Up to now longan by-products are used as a fuel resource for cooking. The main constraint to utilization of these by-products is the high tannin content in seeds. Tannins can have both beneficial and adverse effect (Getachew et al 2000). Beneficial effects of tannins in ruminants include bloat suppression and protection of dietary protein in the rumen and subsequently enhancement of amino acid absorption and utilization by the ruminant animals (Waghorn et al 1987). Adverse effects of tannins include : lower intake and digestibility, inhibition of digestive enzymes and loss of endogenous protein. Apart from tannins, longan seed contains high level of starch (40-60%).
The objectives of this study were to
determine the nutritive value of longan fruit by-products and their utilization
potential as feed resources for dairy goats in small farm conditions
.
The analysis of chemical composition, determination of total
tannin and condensed tannins of longan seed meal, and in vitro gas
production were done in the laboratories of NIAH.
Longan seeds were collected from longan pulp processing units in Hung yen province. They were dried and ground at each unit based on available equipment.
Dry matter and organic matter of longan seeds were determined according to AOAC (1990). Crude protein (N x 6.25) was measured by the Kjeldahl procedure. NDF and ADF were determined following the method of Van Soest and Robertson (1985). Total phenols and tannins were determined by the Folin-Ciocalteu method (Makkar et al 1990) and condensed tannins using the butanol-HCl-Fe reagent (Porter et al 1986).
Dried samples of longan by-products (skins and seeds) were ground to pass through a 1 mm sieve. In vitro gas incubations were carried out using the method of Menke and Steingass (1988) in 40 ml buffered rumen fluid. Samples (0.5 g) were incubated in triplicate in the presence and absence of 1 g polyethylen glyocol (PEG) (MW 6000). Rumen fluid was taken before morning feeding from a rumen-cannulated steer fed a roughage-based diet. Rumen fluid was collected into a pre-warmed thermos bottle, homogenized in a laboratory blender, strained using nylon cloth and then filtered through glass wool. All handing was done under continuous flushing with CO2. During incubation, gas volumes at 2, 4, 6, 8, 10, 12, 16 and 24 h were recorded. The net gas production was calculated by subtracting values from a blank. Organic matter digestibility (OMD) and metabolizable energy (ME) of longan by-products were calculated by using the following relationships (Makkar et al 1996) :
OMD (%) = 14.88 + 0.889*Gv + 0.45*CP
ME (MJ/kg DM) = 2.20 + 0.136*Gv + 0.057*CP.
Where : CP = Crude protein in percent; Gv = net gas production
in ml from 200 mg dry matter after 24 h of
incubation.
The milking goats used in this trial were given diets based on green forages, cassava chips (CSC), hay mixture (HM) and concentrate. The green forages were chopped whole sugar cane (CWSC) and guinea grass. Chopped hay mixture consisted of hay (36%), cassava root meal (14%), cassava leaf meal (18%), sugar cane molasses (24%), mineral premix (6%) and salt (2%). The concentrate used in the experiment was mixed from ingredients bought at the local market and contained 16% crude protein (CP). It consisted of rice bran, maize, cassava root meal, soybean meal, molasses, vitamin-mineral premix, urea, di-calcium phosphorus (18% P), limestone and salt.
Nine lactating goats were used in the trial. The goats were of
the Bachthao and Barbary breeds with initial weight from 55 to 64
kg and in the third or the fourth lactation. The animals
were individually penned. Three lactating goats were allocated to
each of the three treatments. Animals in all treatments were given
the same ration (kg/head/day) (CWSC : 0.9-1.3; HM : 0.7-1.1; CSC :
0.13-0.33 and concentrate 1.2-1.6). In treatment LS-0 (control), the
animals were fed concentrate without LSM; in treatments LS-15 and LS-20 the
concentrate had 15% of LSM + 0% of
urea and 20% of LSM + 0.5%, urea respectively.
The goats were milked twice a day (06: 30 h and 16:30 h) and the
milk yield was recorded. The kids were kept separate from their
mothers and were let in for suckling for 30 minutes after milking time.
The milk sucked was measured by weighing the kids before and after
suckling. Total milk yield was calculate as the sum of milked and
sucked milk. The experimental period started at the 5th
week of lactation, for a total of 8 weeks.
All the feeds offered and refused were recorded daily for calculation of daily dry matter intake and feed conversion ratio. Milk samples were taken every 15 days for analysis of total solids, CP, fat, total ash, Ca and P. The goats were weighed at the beginning and end of the study period.
In comparison with maize and cassava root meal, longan seed had a content of crude protein the same as maize and nearly 3 time higher than cassava chip. Longan seed had high content of crude fibre, NDF and ADF in comparison with maize and cassava root meal.
|
Table 1 : Chemical composition of dried longan seed, maize and cassava chips used in the study (% in DM). |
||||||||
|
|
CP |
EE |
CF |
Ash |
NDF |
ADF |
Ca |
P |
|
Maize |
9.45 |
4.67 |
2.61 |
1.61 |
12.8 |
3.77 |
0.14 |
0.35 |
|
Longan seed |
9.06 |
4.32 |
6.96 |
2.22 |
36.78 |
8.71 |
0.37 |
0.28 |
|
CSRM |
3.18 |
0.73 |
2.66 |
2.25 |
9.42 |
6.32 |
0.16 |
0.13 |
|
CSRM : Cassava root meal |
||||||||
Total phenols, total tannins and condensed tannins concentration were very different according to the components of the seed (husk and seed without husk) and variety of longan tree. Total phenols and condensed tannins concentration were higher in the seed of big seed longan. In both longan varieties, tannins and condensed tannins were concentrated mainly in the kernel of the seed..
|
Table 2 : Concentration of total phenols, total tannins and condensed tannins in the different parts of longan seed (% in DM) |
|||
|
|
Total phenols |
Total tannins |
Condensed tannin |
|
Big seed longan |
|
|
|
|
Black husk |
2.69
|
2.02 |
1.00 |
|
Seed without husk |
3.17 |
2.42 |
1.44 |
|
Whole seed |
5.86 |
4.44 |
2.44 |
|
Small seed longan** |
|
|
|
|
Black husk |
2.22
|
1.95
|
0.44
|
|
Seed without husk
|
2.96
|
2.55
|
0.99
|
|
Whole seed |
5.18 |
4.50 |
1.43 |
|
*Big longan is a variety of longan commonly grown in south Vietnam **Small longan is a variety of longan commonly grown in north Vietnam |
|||
Gas production at 24 h of incubation of
dried longan seed was very low, less than rice straw and
much lower than King grass. ME value and OMD of dried longan seed,
calculated based on gas production at 24 h of incubation and crude
protein were the same as rice straw, but after addition of PEG, gas
production, ME and OMD of longan seed increased significantly (Table 3).
|
Table 3: Gas production at 24 h of incubation, and estimated ME value and organic matter digestibility (OMD) of dried longan seed in comparison with rice straw and King grass. |
|||
|
|
Net gas production at
24 h incubation |
ME value |
OMD |
|
Dried Longan seed |
19.1 |
5.32 |
36.0 |
|
Dried Longan seed + PEG |
24.8 |
6.91 |
46.9 |
|
King grass |
37.0 |
7.78 |
52.1 |
|
Rice straw |
21.5 |
5.35 |
35.8 |
Intake of concentrate and of totalo DM decreased with increasing concentration of longan seed meal in the diet (Table 4).
|
Table 4: Effect of different levels of longan seed meal in concentrate feed on feed intake of lactating goats (g/head/day) |
||||
|
|
LS-0 |
LS-15 |
LS-20 |
SEM |
|
CWSC |
154 |
151.8 |
156.5 |
4.7 |
|
Guine grass |
416a |
437a |
445b |
7.8 |
|
Hay mixture |
424a |
441a |
453b |
7.3 |
|
Cassava chips |
217 |
219 |
212 |
3.9 |
|
Concentrate |
1082a |
910b |
778c |
9.6 |
|
DM intake, total |
2295a |
2159b |
2046c |
11.3 |
|
DM intake, % of BW |
4.39a |
4.19b |
3.76c |
0.22 |
|
abc Means in the same row without common letter are different at P<0.05 |
||||
Lowest milk production and the poorest fed conversion was on the LS-20 treatment (Table 5). Milk composition was not affected by level of longan seed meal in the concentrate.
|
Table 5: Effect of different levels of longan seed meal in concentrate feed on milk yield and feed utilization of lactating goats. |
||||
|
|
LS-0 |
LS-15 |
LS-20 |
SEM |
|
Weight changes (kg) |
|
|
|
|
|
Initial body weight |
53.3 |
51.5 |
54.5 |
2.1 |
|
Final body weight |
50.8 |
49.1 |
51.3 |
2.3 |
|
Weight change |
-2.5 |
-2.4 |
- 3.2 |
0.9 |
|
Milk yield and milk composition |
|
|||
|
Milk yield (g/head/day) |
2689a |
2601a |
2314b |
42 |
|
Total solids (%) |
28.6 |
29.0 |
28.9 |
0.5 |
|
Protein (%0 |
3.20 |
3.25 |
3.20 |
0.09 |
|
Fat (%) |
4.55 |
4.47 |
4.49 |
0.13 |
|
FCR (kg DM/kg milk) |
0.85a |
0.83a |
0.88b |
0.04 |
|
abc Means in the same row without common letter are different at P<0.05 |
||||
Longan seed had similar crude protein level to maize, but
lower overall nutritive value because of high content of cell walls and of
condensed tannins. The low gas production in vitro was probably the
results of the high tannin content in longan seed, as according to Makkar (2003), gas production
in vitro is
inhibited by presence of tannins, especially condensed tannins in
the sample.
Total tannins and condensed tannins in longan seed were very
high in comparison with Flemingia foliage and Jackfruit foliage.
According to Mui et al (2001), total tannins and condensed tannins
of Flemingia and Jackfuit foliage are 2.4% and 0.207% and 3.4% and
0.501%, respectively. Because tannins are considered to play an important role in
the plant's defense against environmental stresses and in disease
resistance, the tree leaves and agro-and forestry-based by-products
in the tropics are likely to have high levels of tannins (Makkar
2003). Longan seed is one of the forestry by-products with high taninns
content. In the feeding trial a low concentrate intake was found in
lactating goats given concentrate with longan seed meal. Tannins in the longan seed makes it become bitter
and this may have been the cause of the lower concentrate intake. The lower milk
on the longan seed treatments was almost certainly the result of the lower
concentrate intake. Additional research should
be carried out in order to fully exploit the potential benefits of incorporating longan seed
in livestock feed.
The nutritive value of Longan seed meal, as
measured by the in vitro gas production test, was relatively low probably
because of the condensed tannins in the seed. In turn this led to reduced
feed intake and milk production of goats
when Longan seed meal was included in the concentrate.
AOAC 1990 Official methods of Analysis 15th Edition. Association of Analytical Chemists. Washington DC.
Getachew G., Makkar H P S and Becker K 2000 Stoichiometric relationship between short chain fatty acid and in vitro gas production in presence and absence of polyethylene glycol for tannin containing browses, EAAP Satellite Symponium, Gas production: fermentation kinetics for feed evaluation and to access microbial activity. 18-19 August 2000., Wageningen, The Netherlands.
Makkar H P S 1996 Application of in vitro gas method in the evaluation of feed resources, and enhancement of nutritional value of tannin-rich tree/brouwse leaves and agro-industrial by-products. Techcondox.
Makkar H P S 2003 Quantification of Tannins in Tree and Shrub Foliage. A Laboratory Manual. Kluwer Academic Publishers.
Nguyen Thi Mui, Ledin Inger, Uden P and Dinh Van Binh 2001 Foliage of Flemingia (Flemingia macrophylla) or Jackfruit (Artocarpus heterophyllus) as a substitute for a rice bran -soya bean concentrate in diet of latating goats. MSc thesis.
Van Soest P J and Robinson J B 1985 A laboratory manual for animal science. Ithaca, N.Y: Cornell University.
Waghorn M J, Ulyatt A J and Fisher T 1987 The effects of condensed tannins on the site of digestion of amino acids and other nutrients in sheep fed on lotus corniculatus L, Br. J. Nutr. 57. 115-126.