- Email: [email protected]
Degradability of leaves from three Erythrina species in Lao PDR
Livestock Science 155 (2013) 273–276
Contents lists available at SciVerse ScienceDirect
Livestock Science journal homepage: www.elsevier.com/locate/livsci
Short communication
Degradability of leaves from three Erythrina species in Lao PDR Daovy Kongmanila a, Jan Bertilsson b, Inger Ledin b, Chalermpon Yuangklang c, Ewa Wredle b,n a
Faculty of Agriculture, National University of Laos, P.O. Box 7322, Vientiane, Lao Democratic People’s Republic Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Box 7024, SE-750 07 Uppsala, Sweden c Faculty of Natural Resources, Rajamangala University of Technology-Isan, Sakon nakhon Campus, Sakon nakhon 47160, Thailand b
a r t i c l e i n f o
abstract
Article history: Received 18 June 2012 Received in revised form 28 May 2013 Accepted 30 May 2013
A study was conducted to determine the chemical composition and degradation value of leaves of three Erythrina species in Lao PDR. The degradability of Erythrina indica, Erythrina subumbrans and Erythrina variegata leaves (including petioles) was assessed by in vitro gas production and in sacco degradation in four 3-year-old fistulated male crossbred goats (Thai native Boer) weighing 30 kg (SD ¼ 1.4). Crude protein (CP) content of E. indica leaves was 156 g/kg dry matter (DM) significantly lower compared to E. variegata and E. subumbrans (203 and 211 g/kg DM). The highest in vitro gas production after 96 h incubation (121 ml/g DM) and in vitro organic digestibility after 24 h incubation (67.2%) were found in E. variegata (P4 0.05). Leaves from E. variegata and E. subumbrans had a higher in sacco CP effective degradability than E. indica leaves (Po 0.05). Thus E. variegata and E. subumbrans appear to be a better option in terms of nutritive values and degradability. & 2013 Elsevier B.V. All rights reserved.
Keywords: Erythrina indica Erythrina subumbrans Erythrina variegata Chemical composition In vitro gas production In sacco degradation
1. Introduction Erythrina is a leguminous fodder tree that can be found throughout the tropical and warm temperate regions. There are three Erythrina species found in different areas of Lao PDR. These species are generally used for fencing around houses or crop fields or as shade trees (Kongmanila et al., 2012). One of these Erythrina species, Erythrina variegata, is also used as a food or as traditional medicine for humans (Kongmanila et al., 2012), and has a high CP content in the foliage, which leads to high intake, digestibility and nitrogen (N) retention in goats (Kongmanila and Ledin, 2009). While there are no studies yet examined on n
Corresponding author. Tel.: +46 18672699. E-mail addresses: [email protected] (D. Kongmanila), [email protected] (J. Bertilsson), [email protected] (I. Ledin), [email protected] (C. Yuangklang), [email protected] (E. Wredle). 1871-1413/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.livsci.2013.05.029
Erythrina indica and Erythrina subumbrans, available in Lao PDR, the objectives of the present study were thus to determine the chemical composition and degradation value of leaves of three Erythrina species in Lao PDR. The hypotheses were that the nutritive values of leaves from E. variegata and leaves from Erythrina spp. growing in the south have higher nutritive values. 2. Materials and methods 2.1. Sample collection, chemical analyses and animals Samples of E. indica, E. subumbrans and E. variegata were randomly collected from 60 different trees in the centre, north and south of Lao PDR, located at 200, 400 and 4700 masl, respectively. Poor soil quality with acid hydromorphic, low organic matter (OM) and nutrient content are found in the central area, while more fertile
274
D. Kongmanila et al. / Livestock Science 155 (2013) 273–276
basaltic soils are found in the south (Kashio and White, 1996). The Erythrina samples were cut 50–60 cm from the tip of the second youngest branch at the top of each tree. Leaves and petioles were included in the sample according to the proportions present in the foliage (DM basis). The 60 samples were then pooled based on area, species and last cutting time, giving 20 samples for the degradability study: 4 samples (6–18 months from last cutting time) of E. indica in the central area, 8 samples (never cut, 0–24 months from last cutting time) of E. variegata in the centre and north, and 8 samples (0–12 months from last cutting time) of E. subumbrans in the north and south. The 20 samples (milled pass 1-mm screen) were used for analysis of DM (method 934.01), ash (ID 942.05) and N (method 984.13) content according to AOAC (1990). Neutral detergent fibre (NDF, without heat-stable amylase) and acid detergent fibre (ADF) were expressed inclusive of residual ash, using the procedure of Van Soest et al. (1991). Four fistulated male crossbreed (Thai native Boer) goats, 3 years of age, with an average body weight (BW) of 30 kg (SD¼ 1.4), were used as experimental animals for in vitro gas production and in sacco degradation (two goats for each method). The goats were fed a diet of 1.5 kg Para grass (Brachiaria mutica (Forsk.) Stapf) and 0.5 kg concentrate consisting of 54.0% cassava chips, 20.7% tomato pomade, 15.8% soybean meal, 1.0% urea, 0.8% salt, 1.0% mineral mix, 0.7% fat and 6.0% molasses. 2.2. Degradation The Erythrina samples (milled through a 1-mm screen) were incubated in vitro with rumen fluid in calibrated glass syringes as proposed by Menke and Steingass (1988). Duplicate samples consisting of 500 mg DM were placed in the syringes (100-ml) with 5 ml of rumen fluid and 20 ml of buffered solution. The mixed rumen liquid was collected before the morning feeding. Gas production was recorded before incubation (0), hourly for 1–12 h, every 3 h until 24 h, every 6 h until 72 h and at 96 h of incubation. Gas production at 24 and 48 h of incubation, together with the concentrations of chemical components, was
used to predict organic matter (OM) digestibility (IVOMD). IVOMD (%)¼ 15.38+0.8453 GP+0.0595CP+0.0675 Ash, where GP is gas volume at the incubation time (Menke and Steingass, 1988). In sacco degradation of DM was determined by incubating 3 g DM sample, milled to pass through a 2-mm screen, in nylon bags (7 10 cm2, 45 mm of pore size) in the rumen of two fistulated male goats, according to Ørskov (1982). Duplicate bags of each sample were incubated for 2, 4, 8, 16, 24, 48 and 96 h. Zero time washing losses were determined by washing with cold water in a washing machine for 30 min until the water ran clear and colourless. After each incubation time, the bags were washed using the same method as in zero time washing to reduce microbial CP contamination in the residual samples, then washed bags were dried at 60 1C for 48 h, weighed and then the residues in the bags were used for analysis of N content. The CP (Nn6.25) disappearance was calculated as the difference between the original incubated and the residual. 2.3. Statistical analyses The kinetics of in vitro and in sacco degradation profiles were described using the exponential equation of Ørskov and McDonald (1979). The data were analysed statistically using the GLM procedure of Minitab Software, version 16.1.1 (Minitab, 2010). Means that showed significant differences at the probability level P o0.05 were compared using Tukey's pair-wise comparison procedure. Four pairwise comparisons based on two independent factors, species and area, using the last cutting age as replications, were performed. There were no significant effects from area, and therefore area was excluded in the final model with Yij ¼m+Ei+eij where Yij is the dependent variable, μ is the overall mean, Ei is the fixed effect of Erythrina species and eij is the random error effect. 3. Results and discussion The DM content of the samples is presented as the predried material (Table 1). The leaves of the three Erythrina
Table 1 Chemical composition and in sacco CP degradation characteristics of the leaves (including petioles) of three Erythrina species. E. indica No. of samples Chemical composition DM, g/kg g/kg DM Ash CP NDF ADF CP degradation characteristics Soluble protein Potential degradable protein Fractional degradation rate Effective degradability
E. subumbrans
E. variegata
SEM
P-value
4
8
8
a
b
926b
4.1
0.013
90ab 211a 569 412
103a 203a 540 425
6.0 10.7 22.3 14.0
0.014 0.012 0.550 0.734
945
75b 156b 556 423 0.44 0.88 0.07 0.74b
927
0.55 0.99 0.10 0.77a
0.60 0.92 0.09 0.83a
0.04 0.05 0.02 0.02
0.067 0.759 0.832 0.021
In the table, DM was the pre-dried value on the 60 individual samples; in sacco CP degradation obtained by fitting the data to the equation y¼ a+b(1−e−ct); a ¼ soluble protein; b¼ potentially degradable protein; c¼ rate of degradation; ECPD ¼ effective CP degradability with rumen passage rate (k) of 0.03; a,b means of the Erythrina species are significantly different (Po 0.05).
D. Kongmanila et al. / Livestock Science 155 (2013) 273–276
275
Table 2 In vitro organic matter digestibility and gas production obtained by fitting the data for Erythrina species over 96 h of incubation to the equation y¼ a+b (1−e−ct). E. indica E. subumbrans E. variegate SEM P-value No. of samples 4 8 8 Gas production characteristic parameters1 bgas (ml) 89.7 99.7 108.9 cgas (%/h) 0.04b 0.05ab 0.06a a+b (ml) 114.1 106.0 117.3
8.1 0.048 0.01 0.031 6.6 0.084
In vitro organic matter digestibility (IVOMD), % IVOMD24 62.3 65.6 67.2 IVOMD48 68.9 70.7 76.5
1.2 2.4
0.416 0.090
Fig. 1. Gas producton volume (ml/g DM) of E. variegata leaves from the centre of Lao PDR at different last cutting times. Never cut and cutting at 24 months interval differed significantly (Po 0.01).
1 bgas ¼ fermentation of insoluble fermentable with time; cgas ¼ rate of gas production; (a+b) ¼ potential extent of gas production; a,bmeans of two Erythrina species area are significantly different (Po 0.05).
species had CP contents of 156–211 g/kg DM. E. indica had significantly lower CP content compared to E. variegata and E. subumbrans (P o0.05). This is within the range cited by many authors examining the CP content in different Erythrina species, e.g. 193 g/kg DM in E. variegata (Kongmanila and Ledin, 2009), 118–213 g/kg DM in Erythrina standleyana and E. indica (Monforte-Briceño et al., 2005) and 221–264 g/kg DM in Erythrina poeppigiana (Camero et al., 2001). In the present study, petioles, which generally have a lower CP content, were included whereas in many of the previous studies leaves only were analysed. Longer time between cutting of the leaves and older trees are a likely reason for the lower CP content of E. indica (Table 1). Interestingly, the different geographical conditions, especially poor soil quality (low pH, OM and fertility), in the centre of Lao PDR (Kashio and White, 1996) had no effect on the chemical composition of Erythrina leaves in the present study. Tropical forages generally have a high proportion of lignified cell walls, resulting in low digestibility rates (Ibrahim et al., 1995). At 48 h of incubation time, IVOMD in Erythrina species leaves ranged between 69% and 77% (Table 2), which was higher than values reported previously for the same legume family with similar cutting time of leaves, such as 42–51% in Leucaena leucocephala and 60–63% in Gliricidia lepium (Edwards et al., 2012). Higher NDF and ADF, and probably also higher lignin content, could be the reason for the lower IVOMD in the two leguminous species, compared with Erythrina species in the present study. The leaves of E. indica, which contained 556 g/kg DM of NDF, had a lower rate of gas production (cgas, 0.04%/h) than E. variegata leaves, which contained 540 g/kg DM of NDF (cgas ¼0.06%/h) (Table 2). The faster rate of gas production was possibly due to the soluble carbohydrate fractions being readily available to the microbial population because of high fermentation of plant cell walls. The in vitro gas production as a mean for different last cutting times during the fermentation periods did not differ significantly, indicating that the content of degradable carbohydrates was quite similar in the Erythrina species. Gas production parameters indicate differences in nutritional values generally closely related to chemical composition
Fig. 2. In sacco CP degradability (%) over 36 h of incubation of three Erythrina species, with no significant difference between species.
(Cerrillo and Juárez, 2004), especially aspects of the carbohydrate fraction or the fibre content such as the extent of lignification of NDF (Fonseca et al., 1998). Cutting at longer time intervals (24 months) and foliage with high NDF and ADF content resulted in lower gas production resulting from low fermentation rate by rumen microbes. Foliage of E. variegata, from tree never cut, resulted in the highest gas production (P o0.01) (Fig. 1). One possible explanation could be that the tree (by random) was younger than other trees. Over 85% of total CP (Fig. 2) was degraded in the rumen after 96 h of incubation for all three Erythrina species. Degradation kinetics was high in leaves of E. variegata and E. subumbrans, but low in the leaves of E. indica. Older age of trees and/or re-growth of the leaves with low CP content in E. indica could be main reason for lower effective degradability. 4. Conclusions Erythrina variegata, E. indica and E. subumbrans leaves have high potential as protein forage (156–211 g/kg DM). Based on the data presented here on CP content and in vitro fermentation and in sacco degradation characteristics, leaves of the three Erythrina species, especially E. variegata and E. subumbrans, can be recommended as a nutrient source for goats. Conflict of interest There is no conflict of interest about this manuscript.
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D. Kongmanila et al. / Livestock Science 155 (2013) 273–276
Acknowledgements The authors gratefully acknowledge the Swedish International Development Agency/Department for Research Cooperation with Developing Countries (Sida/SAREC) for financial support for this research, and the Faculty of Natural Resources, Rajamangala University of Technology-Isan, Sakon Nakhon Campus, Thailand and the Faculty of Agriculture, National University of Laos, for making the facilities available during the experiments. References AOAC, 1990. Official methods of analysis. Association of Official Analytical Chemists, 15th ed. Arlington, Virginia I, pp. 69–90. Camero, A., Ibrahim, M., Kass, M., 2001. Improving rumen fermentation and milk production with legume-tree fodder in the tropics. Agrofor. Syst. 51, 157–166. Cerrillo, M.A., Juárez, R.A.S., 2004. In vitro gas production parameters in cacti and tree species commonly consumed by grazing goats in a semiarid region of North Mexico. Livest. Res. Rural Dev. 16, 1–7. Edwards, A., Mlambo, V., Lallo, C.H.O., Gracia, G.W., 2012. Yield, chemical composition and in vitro ruminal fermentation of the leaves of Leucaena leucocephala, Gliricidia sepium and Trichanthera gigantean as influenced by harvesting frequency. J. Anim. Sci. Adv. 2, 321–331. Fonseca, A.J.M., Dias-da-Silva, A.A., Ørskov, E.R., 1998. In sacco degradation characteristics as predictors of digestibility and voluntary intake of roughages by mature ewes. Anim. Feed Sci. Technol. 72, 205–219.
Ibrahim, M.N.M., Tamminga, S., Zemmelink, G., 1995. Degradation of tropical roughages and concentrate feeds in the rumen. Anim. Feed. Sci. Technol. 54, 81–92. Kashio, M., White, K., 1996. Eucalyptus in Lao PDR-Bounphom Mounda. Reports submitted to the regional expert consultation on eucalyptus, vol. II. 〈www.fao.org/DOCREP/005/AC772E/AC772E00.HTM〉. Kongmanila, D., Ledin, I., 2009. Chemical composition of some tropical foliage species and their intake and digestibility by goats. Asian–Aust. J. Anim. Sci. 22, 803–811. Kongmanila, D., Bertilsson, J., Ledin, I., Wredle, E., 2012. Utilisation of some Erythrina species and biomass production of Erythrina variegata. Livest. Res Rural Dev. 24 (8), 1–8. Menke, K.H., Steingass, H., 1988. Estimation of the energetic feed value from chemical analysis and in vitro gas production using rumen fluid. Anim. Res. Dev. 28, 7–55. Minitab, 2010. Minitab User's Guide. Data Analysis and Quality Tools. Release 16.1 for Windows. Minitab Inc., Pennsylvania, USA. Monforte-Briceño, G.E., Sandoval-Castro, C.A., Ramírez-Avilés, L., Leal, C.M.C., 2005. Defaunating capacity of tropical fodder trees: effects of polyethylene glycol and its relationship to in vitro gas production. Anim. Feed Sci. Technol. 123–124 (Part 1), 313–327. Ørskov, E.R., 1982. Protein Nutrition in Ruminants. Academic Press, London (Chapter 2). Ørskov, E.R., McDonald, I., 1979. The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage. J. Agri. Sci. Cambridge 92 (Part 2), 499–503. Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for dietary fiber, neutral detergent fiber, and non-starch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74, 3583–3597.
Contents lists available at SciVerse ScienceDirect
Livestock Science journal homepage: www.elsevier.com/locate/livsci
Short communication
Degradability of leaves from three Erythrina species in Lao PDR Daovy Kongmanila a, Jan Bertilsson b, Inger Ledin b, Chalermpon Yuangklang c, Ewa Wredle b,n a
Faculty of Agriculture, National University of Laos, P.O. Box 7322, Vientiane, Lao Democratic People’s Republic Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Box 7024, SE-750 07 Uppsala, Sweden c Faculty of Natural Resources, Rajamangala University of Technology-Isan, Sakon nakhon Campus, Sakon nakhon 47160, Thailand b
a r t i c l e i n f o
abstract
Article history: Received 18 June 2012 Received in revised form 28 May 2013 Accepted 30 May 2013
A study was conducted to determine the chemical composition and degradation value of leaves of three Erythrina species in Lao PDR. The degradability of Erythrina indica, Erythrina subumbrans and Erythrina variegata leaves (including petioles) was assessed by in vitro gas production and in sacco degradation in four 3-year-old fistulated male crossbred goats (Thai native Boer) weighing 30 kg (SD ¼ 1.4). Crude protein (CP) content of E. indica leaves was 156 g/kg dry matter (DM) significantly lower compared to E. variegata and E. subumbrans (203 and 211 g/kg DM). The highest in vitro gas production after 96 h incubation (121 ml/g DM) and in vitro organic digestibility after 24 h incubation (67.2%) were found in E. variegata (P4 0.05). Leaves from E. variegata and E. subumbrans had a higher in sacco CP effective degradability than E. indica leaves (Po 0.05). Thus E. variegata and E. subumbrans appear to be a better option in terms of nutritive values and degradability. & 2013 Elsevier B.V. All rights reserved.
Keywords: Erythrina indica Erythrina subumbrans Erythrina variegata Chemical composition In vitro gas production In sacco degradation
1. Introduction Erythrina is a leguminous fodder tree that can be found throughout the tropical and warm temperate regions. There are three Erythrina species found in different areas of Lao PDR. These species are generally used for fencing around houses or crop fields or as shade trees (Kongmanila et al., 2012). One of these Erythrina species, Erythrina variegata, is also used as a food or as traditional medicine for humans (Kongmanila et al., 2012), and has a high CP content in the foliage, which leads to high intake, digestibility and nitrogen (N) retention in goats (Kongmanila and Ledin, 2009). While there are no studies yet examined on n
Corresponding author. Tel.: +46 18672699. E-mail addresses: [email protected] (D. Kongmanila), [email protected] (J. Bertilsson), [email protected] (I. Ledin), [email protected] (C. Yuangklang), [email protected] (E. Wredle). 1871-1413/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.livsci.2013.05.029
Erythrina indica and Erythrina subumbrans, available in Lao PDR, the objectives of the present study were thus to determine the chemical composition and degradation value of leaves of three Erythrina species in Lao PDR. The hypotheses were that the nutritive values of leaves from E. variegata and leaves from Erythrina spp. growing in the south have higher nutritive values. 2. Materials and methods 2.1. Sample collection, chemical analyses and animals Samples of E. indica, E. subumbrans and E. variegata were randomly collected from 60 different trees in the centre, north and south of Lao PDR, located at 200, 400 and 4700 masl, respectively. Poor soil quality with acid hydromorphic, low organic matter (OM) and nutrient content are found in the central area, while more fertile
274
D. Kongmanila et al. / Livestock Science 155 (2013) 273–276
basaltic soils are found in the south (Kashio and White, 1996). The Erythrina samples were cut 50–60 cm from the tip of the second youngest branch at the top of each tree. Leaves and petioles were included in the sample according to the proportions present in the foliage (DM basis). The 60 samples were then pooled based on area, species and last cutting time, giving 20 samples for the degradability study: 4 samples (6–18 months from last cutting time) of E. indica in the central area, 8 samples (never cut, 0–24 months from last cutting time) of E. variegata in the centre and north, and 8 samples (0–12 months from last cutting time) of E. subumbrans in the north and south. The 20 samples (milled pass 1-mm screen) were used for analysis of DM (method 934.01), ash (ID 942.05) and N (method 984.13) content according to AOAC (1990). Neutral detergent fibre (NDF, without heat-stable amylase) and acid detergent fibre (ADF) were expressed inclusive of residual ash, using the procedure of Van Soest et al. (1991). Four fistulated male crossbreed (Thai native Boer) goats, 3 years of age, with an average body weight (BW) of 30 kg (SD¼ 1.4), were used as experimental animals for in vitro gas production and in sacco degradation (two goats for each method). The goats were fed a diet of 1.5 kg Para grass (Brachiaria mutica (Forsk.) Stapf) and 0.5 kg concentrate consisting of 54.0% cassava chips, 20.7% tomato pomade, 15.8% soybean meal, 1.0% urea, 0.8% salt, 1.0% mineral mix, 0.7% fat and 6.0% molasses. 2.2. Degradation The Erythrina samples (milled through a 1-mm screen) were incubated in vitro with rumen fluid in calibrated glass syringes as proposed by Menke and Steingass (1988). Duplicate samples consisting of 500 mg DM were placed in the syringes (100-ml) with 5 ml of rumen fluid and 20 ml of buffered solution. The mixed rumen liquid was collected before the morning feeding. Gas production was recorded before incubation (0), hourly for 1–12 h, every 3 h until 24 h, every 6 h until 72 h and at 96 h of incubation. Gas production at 24 and 48 h of incubation, together with the concentrations of chemical components, was
used to predict organic matter (OM) digestibility (IVOMD). IVOMD (%)¼ 15.38+0.8453 GP+0.0595CP+0.0675 Ash, where GP is gas volume at the incubation time (Menke and Steingass, 1988). In sacco degradation of DM was determined by incubating 3 g DM sample, milled to pass through a 2-mm screen, in nylon bags (7 10 cm2, 45 mm of pore size) in the rumen of two fistulated male goats, according to Ørskov (1982). Duplicate bags of each sample were incubated for 2, 4, 8, 16, 24, 48 and 96 h. Zero time washing losses were determined by washing with cold water in a washing machine for 30 min until the water ran clear and colourless. After each incubation time, the bags were washed using the same method as in zero time washing to reduce microbial CP contamination in the residual samples, then washed bags were dried at 60 1C for 48 h, weighed and then the residues in the bags were used for analysis of N content. The CP (Nn6.25) disappearance was calculated as the difference between the original incubated and the residual. 2.3. Statistical analyses The kinetics of in vitro and in sacco degradation profiles were described using the exponential equation of Ørskov and McDonald (1979). The data were analysed statistically using the GLM procedure of Minitab Software, version 16.1.1 (Minitab, 2010). Means that showed significant differences at the probability level P o0.05 were compared using Tukey's pair-wise comparison procedure. Four pairwise comparisons based on two independent factors, species and area, using the last cutting age as replications, were performed. There were no significant effects from area, and therefore area was excluded in the final model with Yij ¼m+Ei+eij where Yij is the dependent variable, μ is the overall mean, Ei is the fixed effect of Erythrina species and eij is the random error effect. 3. Results and discussion The DM content of the samples is presented as the predried material (Table 1). The leaves of the three Erythrina
Table 1 Chemical composition and in sacco CP degradation characteristics of the leaves (including petioles) of three Erythrina species. E. indica No. of samples Chemical composition DM, g/kg g/kg DM Ash CP NDF ADF CP degradation characteristics Soluble protein Potential degradable protein Fractional degradation rate Effective degradability
E. subumbrans
E. variegata
SEM
P-value
4
8
8
a
b
926b
4.1
0.013
90ab 211a 569 412
103a 203a 540 425
6.0 10.7 22.3 14.0
0.014 0.012 0.550 0.734
945
75b 156b 556 423 0.44 0.88 0.07 0.74b
927
0.55 0.99 0.10 0.77a
0.60 0.92 0.09 0.83a
0.04 0.05 0.02 0.02
0.067 0.759 0.832 0.021
In the table, DM was the pre-dried value on the 60 individual samples; in sacco CP degradation obtained by fitting the data to the equation y¼ a+b(1−e−ct); a ¼ soluble protein; b¼ potentially degradable protein; c¼ rate of degradation; ECPD ¼ effective CP degradability with rumen passage rate (k) of 0.03; a,b means of the Erythrina species are significantly different (Po 0.05).
D. Kongmanila et al. / Livestock Science 155 (2013) 273–276
275
Table 2 In vitro organic matter digestibility and gas production obtained by fitting the data for Erythrina species over 96 h of incubation to the equation y¼ a+b (1−e−ct). E. indica E. subumbrans E. variegate SEM P-value No. of samples 4 8 8 Gas production characteristic parameters1 bgas (ml) 89.7 99.7 108.9 cgas (%/h) 0.04b 0.05ab 0.06a a+b (ml) 114.1 106.0 117.3
8.1 0.048 0.01 0.031 6.6 0.084
In vitro organic matter digestibility (IVOMD), % IVOMD24 62.3 65.6 67.2 IVOMD48 68.9 70.7 76.5
1.2 2.4
0.416 0.090
Fig. 1. Gas producton volume (ml/g DM) of E. variegata leaves from the centre of Lao PDR at different last cutting times. Never cut and cutting at 24 months interval differed significantly (Po 0.01).
1 bgas ¼ fermentation of insoluble fermentable with time; cgas ¼ rate of gas production; (a+b) ¼ potential extent of gas production; a,bmeans of two Erythrina species area are significantly different (Po 0.05).
species had CP contents of 156–211 g/kg DM. E. indica had significantly lower CP content compared to E. variegata and E. subumbrans (P o0.05). This is within the range cited by many authors examining the CP content in different Erythrina species, e.g. 193 g/kg DM in E. variegata (Kongmanila and Ledin, 2009), 118–213 g/kg DM in Erythrina standleyana and E. indica (Monforte-Briceño et al., 2005) and 221–264 g/kg DM in Erythrina poeppigiana (Camero et al., 2001). In the present study, petioles, which generally have a lower CP content, were included whereas in many of the previous studies leaves only were analysed. Longer time between cutting of the leaves and older trees are a likely reason for the lower CP content of E. indica (Table 1). Interestingly, the different geographical conditions, especially poor soil quality (low pH, OM and fertility), in the centre of Lao PDR (Kashio and White, 1996) had no effect on the chemical composition of Erythrina leaves in the present study. Tropical forages generally have a high proportion of lignified cell walls, resulting in low digestibility rates (Ibrahim et al., 1995). At 48 h of incubation time, IVOMD in Erythrina species leaves ranged between 69% and 77% (Table 2), which was higher than values reported previously for the same legume family with similar cutting time of leaves, such as 42–51% in Leucaena leucocephala and 60–63% in Gliricidia lepium (Edwards et al., 2012). Higher NDF and ADF, and probably also higher lignin content, could be the reason for the lower IVOMD in the two leguminous species, compared with Erythrina species in the present study. The leaves of E. indica, which contained 556 g/kg DM of NDF, had a lower rate of gas production (cgas, 0.04%/h) than E. variegata leaves, which contained 540 g/kg DM of NDF (cgas ¼0.06%/h) (Table 2). The faster rate of gas production was possibly due to the soluble carbohydrate fractions being readily available to the microbial population because of high fermentation of plant cell walls. The in vitro gas production as a mean for different last cutting times during the fermentation periods did not differ significantly, indicating that the content of degradable carbohydrates was quite similar in the Erythrina species. Gas production parameters indicate differences in nutritional values generally closely related to chemical composition
Fig. 2. In sacco CP degradability (%) over 36 h of incubation of three Erythrina species, with no significant difference between species.
(Cerrillo and Juárez, 2004), especially aspects of the carbohydrate fraction or the fibre content such as the extent of lignification of NDF (Fonseca et al., 1998). Cutting at longer time intervals (24 months) and foliage with high NDF and ADF content resulted in lower gas production resulting from low fermentation rate by rumen microbes. Foliage of E. variegata, from tree never cut, resulted in the highest gas production (P o0.01) (Fig. 1). One possible explanation could be that the tree (by random) was younger than other trees. Over 85% of total CP (Fig. 2) was degraded in the rumen after 96 h of incubation for all three Erythrina species. Degradation kinetics was high in leaves of E. variegata and E. subumbrans, but low in the leaves of E. indica. Older age of trees and/or re-growth of the leaves with low CP content in E. indica could be main reason for lower effective degradability. 4. Conclusions Erythrina variegata, E. indica and E. subumbrans leaves have high potential as protein forage (156–211 g/kg DM). Based on the data presented here on CP content and in vitro fermentation and in sacco degradation characteristics, leaves of the three Erythrina species, especially E. variegata and E. subumbrans, can be recommended as a nutrient source for goats. Conflict of interest There is no conflict of interest about this manuscript.
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