| Livestock Research for Rural Development 26 (4) 2014 | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
An experiment was conducted to investigate the effects of processing, additive and silo type on the quality of elephant grass silage. Four treatments were imposed on the forage before it was ensiled in either earth pits or concrete silos. The treatments were chopped elephant grass with 3 %, chopped grass without molasses, unchopped grass with 3 % molasses and unchopped grass without molasses. The treatments were arranged in a factorial design of 2 x 2 x 2 with two replications. The silage was opened and sampled after 90 days, analysed for dry matter (DM) losses, chemical composition, fermentation and sensoric qualities, in vitro DM and organic matter (OM) digestibility and DM degradability. The rate of silage intake in g DM/minute was determined using six dairy heifers.
Both chopped and 3 % molasses treated silages showed lower (P < 0.05) DM losses as compared to chopped and unmolassed silage. The DM losses did not differ significantly between the silo types. Chopped silage had more (P < 0.05) crude protein (CP) and water soluble carbohydrate (WSC) contents than unchopped silage. Addition of 3 % molasses significantly increased (P < 0.01) the CP and WSC of the silage. The CP content however, was significantly (P < 0.05) higher earth pit than concrete silos. The fermentation quality of the silage was highly (P<0.05) improved by chopping and addition of 3 % molasses at ensiling. Lower pH (3.99 vs 4.64), NH3N of total N(4.03 vs 6.37) and butyric acid concentration (2.6 vs 7.5 g/kg DM) and higher content of lactic acid (37.3 vs 14.2 g/kg DM) and acetic acid 38.5 vs 21.8 g/kg DM were observed in chopped than unchopped silage. Lower pH, NH3N and butyric acid (4.21 vs 4.43, 4.09 vs 6.31 % and 3.8 vs 6.4 g/kg DM, respectively) and higher lactic and acetic acids concentrations were observed in molasses treated as compared to untreated silage. The sensoric scores of silage were significantly (P < 0.05) better for chopped and molasses silages. Chopping and addition of molasses produced silages with significantly higher (P < 0.05) in vitro DM and OM digestibility and in sacco DM degradability than unchopped and without molasses. There was a significant (P < 0.05) improvement in intake rate of silage when the animals were fed chopped and molasses treated silages. It can be concluded that chopping and addition of at least 3 % molasses to elephant grass at ensiling can produce good quality silage.
Key words: earth and pit silos, degradability, fermentation quality, molasses, sensoric score
In many tropical regions, there is inadequate and inconsistent supply of good quality pasture and fodder to support maintenance, reproduction and production of ruminant livestock throughout the year. The problem is more evident during the dry season which may last about 5 to 7 months per year (Mbwile and Madata 1984). The situation seems to be more serious among the smallholder dairy farmers, particularly those who practice zero grazing systems in high potential areas in East African Highlands because of scarcity of land to produce forage (Urio 1987). In these high potential areas most of the land is used for food and cash crop production leaving very small area for pastures and fodder production that cannot meet forage demand during the dry season. However, many dairy farmers in these high potential areas have adopted home fodder garden technology (Mtengeti et al 2001). The fodder gardens are planted with high yielding fodder grasses such as elephant grass, guatemala grass and giant setaria which produce large quantities of fodder in the rain season and if left to grow and mature in the fields loose their nutritive value, thereby resulting into wastage of valuable feed resources. In order to avoid such losses and to maintain higher productivity of dairy animals even during the dry season, there is a need to develop the most efficient methods of conserving the surplus forages available during the wet season. Silage making is one of the methods that could be used to achieve this objective. Among the main fodder established in East African highlands, elephant grass has been extensively adopted by dairy farmers due to its high productivity and persistence than the other fodder grass (Kitaly 2005). With application of nitrogenous fertilizer and other forage management practices, elephant grass can offer sufficient and good quality fodder, and the excess fodder can be conserved in form of silage, thereby ensuring availability of good quality feed for feeding dairy animals throughout the year. Silage making and utilization has been practiced for a long period by dairy farmers in temperate countries (Woodard et al 1992) and in a few tropical countries. The objective of this study was therefore to evaluate the quality of unchopped and chopped elephant grass silage ensiled with or without molasses in earth pit or concrete silos.
A ten weeks regrowth of elephant grass at Sokoine University of Agriculture farm, Tanzania was harvested and subjected to four treatments before ensiling in either earth pits or concrete silos. Concrete silos were built above the ground. Both earth pit and concrete silos dimensions were 1 m deep, 1m wide and 1 m long. The treatments were: 5 cm chopped grass and 3 % molasses, 5 cm chopped grass without molasses, unchopped grass and 3 % molasses and unchopped grass without molasses. The forage was chopped by a tractor driven chopper. Each treatment was replicated twice and in total there were16 silos.
Plastic sheets were spread to cover all the side walls of each silo to prevent contamination of the ensiled forage and soil or rough concrete surface. At the bottom surface of each silo, a layer of about 5 cm depth of dry grass was laid to allow seepage of effluent and to prevent direct contact between ensiled material and soil or rough concrete surface. Ensiling material was thoroughly compacted by using a concrete block (fitted with a metallic handle and weighing approximately 50 kg) on layer after layer until each silo was filled up with 500 kg of ensiling material The topmost layer of each silo was then covered by an overlapping plastic sheet, followed with a heap of soil so as to create constant pressure to exclude air throughout the ensiling period of 90 days.
Before ensiling, two samples each weighing 400 g were taken from each treatment, dried and later used for degradability studies and chemical composition analysis. After 90 days of ensiling the silos were opened and all parts of spoiled silage was carefully removed and weighed and 200g sample was collected for the determination of dry matter used in the calculating dry matter losses. Thereafter the remaining spoiled sample was discarded. Five samples each weighing 400g were also collected from unspoiled silage (i.e. good silage) immediately before it was put in large plastic bags and weighed and then used for intake rate trial. The samples were also used to determine volatile fatty acids, ammonium-nitrogen, dry matter percentage, chemical composition, digestibility and degradability.
On opening each silo, the silage was physically assessed in terms of appearance, smell and texture. This was done by a panel of 10 assessors each marking the appropriate score grade on an arbitrary organoleptic test chart. The dry matter contents (DM) of the ensiling material and silages were determined by freeze-drying. The ash, crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), water soluble carbohydrates (WSC) and in vitro dry matter digestibility (IVDMD) were analysed from the freeze dried samples while the ammonia-nitrogen (NH3N) was analysed from fresh silage samples. The ash, CP and NH3N were analysed according to AOAC (1990) procedures. Water soluble carbohydrate was determined according to Thomas (1977). The NDF and ADF were analysed according to Van Soest et al (1991). A pH meter (model 219-MK 2; Pye Unicam) was used to measure the pH of the silages. Samples of 40g from each silo were soaked in 200 ml of cool distilled water for 12 hours then filtered and the supernatant used for the determination of the pH. The silages were analysed for lactic acid and volatile fatty acid (VFA) contents according to Playne (1985). The in vitro dry matter and organic matter digestibility were determined according to Tilley and Terry (1963). The dry matter lost from silos was calculated as the difference between the kg DM in the original ensiled material and that found in the silage recovered as follows: kg DM loss = kg DM of ensiled material – kg DM of recovered silage; whereby: kg DM recovered silage = kg DM of good silage + kg DM of spoiled silage.
Six dairy heifers (Friesian x Ayrshire cross) each weighing on average 255 kg live weight were used in the silage intake rate trial. In order to accustom the animals to the experimental diets 7 days prior to intake trial, each animal was offered 14 kg of elephant grass silage (19.2 % DM) and 2 kg of concentrate 0900 hours and 7 kg of fresh Brahiaria ruziziensis (29.4 % DM) at 1600 hrs. In the evening before feeding the experimental silage, heifers were not given any feed till morning so as to activate intake of the experimental silage. During the intake trial the heifers were given each 5 silage meals (each meal weighing 5 kg) from good silage of each silo. The heifers were allowed to eat each silage meal for 10 minutes. The remaining part of each meal after 10 minutes was weighed and subtracted from 5 kg to get the amount eaten per meal of fresh silage. Thereafter, the amount eaten was converted into dry matter intake rate per minute (g DM/mn.).
Two rumen fistulated Friesian steers with on average weight of 320 kg live weight were used in degradability study. The animals were fitted with cannulae of 10 cm effective diameter. Throughout the study period the steers were fed ration comprised of 70 % grass hay and 30 % concentrate. Preparation of samples for incubation using nylon bag technique was done as described by Ǿrskov et al (1980). Freeze dried silage samples were ground in a hammer mill to pass through 2 mm sieve. Test samples (each weighing 2g) of ensiling material and silage were put in two sterilized and weighed nylon bags per animal per incubation time. The nylon bags had effective size of 270 x 115 mm and mean pore size of 40 µm. The bags containing the samples were labeled, fastened using rubber bands and anchored into three separate plastic tubes which were then ready to be incubated in the rumen. The rumen degradability of samples was assessed at six different incubation times i.e. 12, 24, 48, 96 and 120 hours. After which they were withdrawn, washed in running tap water and then dried in an oven at 60oC, cooled in the desiccator, weighed and dry matter loss calculated. The degradability at zero hour was determined by soaking the duplicate bags with samples in water for 24 hours. The bags were then dried for 48 hours at 60oC, cooled in the desiccator, weighed and dry matter loss calculated. The percentage DM degradability and degradation constants were calculated according to mathematical model proposed by Ǿrskov and McDonald (1979): P = a +b (1- e-ct); where: P = the % degradability at time t, a =water soluble fraction assumed to disappear instantly, b = not water soluble but potentially rumen degradable part, a +b = potentially rumen degradable, c = rate constant at which insoluble material is degraded, e = the base of natural logarithms, t= incubation time. The calculation of degradability constants and fitted degradability values were executed using SAS program Proc “NAWAY” (SAS 1988). Effective degradability of the samples were calculated by using SUPERCAL computer package at a passage rate of 0.1 using formula of Ǿrskov and McDonald (1979): Y = a + bc/(c+k); where: Y= effective degradability, a = water soluble component, b = water insoluble but potentially rumen degradable part, c = rate of degradability of insoluble material, k = passage rate.
Data on chemical composition and degradability of pre-ensiled elephant grass were analysed under 22 factorial arrangements. The data for chemical composition, in vitro DM and OM digestibility, fermentation products, sensoric quality, dry matter loss, intake rate and DM degradability were analysed under 23 factorial arrangements. General linear model (GLM) procedures of Statistical Analysis System (1988) were used to analyse the data. The mathematical model used for analysis of chemical composition and degradability of the four pre-ensiling treatment of elephant grass was: Yij =µ + ai +bj + abij + eij; where: Yij = quality attributes of pre-ensiling treatment of elephant grass, µ=fixed general effect, ai= effect of ith physical preparation method (i.e. chopped and unchopped), bj = effect of jth additive level, abij = ineraction of ith preparation method and jth additive, eij = random error. The effects of the three factors (i.e. silo type, chopping and additive level) was analysed using the following mathematical model: Yijk = µ + ai +bj + ck + abij + acik + bcjk + abcijk + eijk; where: Yijk = quality attributes of elephant grass silage, µ = fixed general effect, ai = effect of ith type of silo (i.e. earth pit and concrete), bj = effect of jth = pre-ensiling preparation method, ck = effect of kth additive level, abij = interaction of ith silo and jth pre-ensiling physical preparation, acik = interaction of ith silo and kth additive level, bcjk = interaction of jth pre-ensiling physical preparation and kth additive level, abcijk = interaction of ith silo, jth pre-ensiling physical preparation and kth additive level, eijk = random error. The F-ratios were used to test any significant difference between the main effects for the factors studied, and the mean values compared using the Least Significance Difference.
Mean chemical composition, in vitro dry matter digestibility and rumen dry matter degradability of fresh elephant grass and pre-ensiling treatments are shown in Table 1. The DM content of freshly harvested elephant grass was rather lower than the recommended DM of ensiling material (250 to 300 g/kg DM) (Nussio 2005). However, almost similar values were reported by Muinga et al (1991) for elephant grass harvested at the same stage of growth as for this study. Addition of 3 % molasses slightly improved the DM content of elephant grass before ensiling. This was expected since molasses itself had DM content of 651 g/kg DM. Dixon (1982) and McCullough (1983) suggested that the best silage from high moisture forage can be obtained when the fodder is wilted to a minimum of 250 g/kg DM. This may be rather difficult under tropical conditions with irregular periods of rains. The CP content observed in this study was within range of those reported elsewhere at the same stage of growth (Muinga et al 1991). There was no significant variation of fibre content of the materials used for ensiling in this experiment. However, the fibre values were lower than those reported by Otieno et al (1990) possibly due to different ecological position and age of the fodder grass used for ensiling. The digestibility and effective degradability of the pre-ensiling material was higher in molasses treated material possibly due an increase in WSC content. The lower effective degradability (49 %) for elephant grass harvested at about 1.5 m tall that was reported by Muinga et al (1991) could be due to the lower CP and higher NDF values of 56 and 709 g/kg DM, respectively when compared to those of the pre-ensiling forage treatments used in the current study.
|
Table 1: Chemical composition, in vitro dry matter digestibility and rumen dry matter degradability of fresh elephant grass and pre-ensiled treatments |
|||||||
|
Parameter |
Fresh |
Chopped |
Chopped |
Unchopped |
Unchopped |
SEM |
P-Value |
|
Chemical composition and in vitro DM digestibility |
|||||||
|
DM % |
16.0 |
18.3 b |
16.1c |
17.8b |
16.1c |
0.15 |
0.0019 |
|
g/kg DM |
|||||||
|
CP |
71.9 |
71.8 |
71.7 |
71.2 |
71.3 |
0.93 |
<0.0001 |
|
Ash |
125.7 |
132.0 |
125.6 |
127.8 |
124.1 |
3.92 |
0.6743 |
|
NDF |
561.5 |
566.6 |
562.5 |
553.7 |
560.4 |
11.24 |
0.2867 |
|
ADF |
341.5 |
341.8 |
340.4 |
341.5 |
342.6 |
5.88 |
0.0089 |
|
ADL |
36.8 |
36.2 |
37.2 |
37.7 |
36.4 |
0.70 |
<0.0001 |
|
WSC |
29.0 |
54.5a |
29.2b |
43.8a |
29.3 b |
4.32 |
0.0015 |
|
IVDMD % |
57.1 |
64.9 a |
56.9b |
61.5a |
57.3 b |
2.09 |
<0.0001 |
|
IVODMD % |
57.2 |
64.2a |
56.7b |
62.9a |
57.4 b |
1.83 |
0.0007 |
|
Degradability constants |
|
||||||
|
A |
30.9 a |
23.4 b |
30.7 a |
23.2 b |
1.04 |
0.0050 |
|
|
B |
42.0 b |
47.3 a |
41.9 b |
47.8 a |
0.96 |
0.0061 |
|
|
A+B |
72.9 |
70.7 |
72.6 |
71.0 |
0.80 |
0.0122 |
|
|
C |
0.044 a |
0.029 b |
0.045 a |
0.029 b |
0.0019 |
0.00013 |
|
|
Effective degradability % |
65.1 a |
58.5 b |
64.9 a |
58.7 b |
0.81 |
0.0231 |
|
|
48 hrs DMD % |
67.7 a |
58.8 b |
67.5 a |
58.9 b |
1.03 |
0.0536 |
|
|
Mean values within the same row followed by different superscripts are different at P < 0.05
|
|||||||
The significantly lower (P < 0.05) fibre contents in chopped than unchopped silages (Table 2) could be due to improved fermentation in chopped than unchopped silages since chopping exposed mores surfaces of the plant for enzymatic hydrolysis of the linked sugar molecules in hemicellulose. This agrees with the argument of Fairbarn et al (1988) that increased proteolysis in uncontrolled fermentation of poorly consolidated high moisture crops may reduce more than 50 % of the total N present in the herbage. Higher amount of WSC content was retained in chopped silage as compared with unchopped silage and this agreed well with Panditharatne et al (1996), that chopping of forages prior to ensiling restricts losses of carbohydrates due to aerobic deterioration because of thorough compaction and thus expulsion of air and encouragement of early decline of the pH of ensiled mass (Mushi et al 2000). Organic matter digestibility of elephant grass silage were improved by chopping of forage prior to ensiling as more than 50 % of the organic matter in chopped silage was digested compared with only 41.4 % in unchopped silage. This was contributed by better fermentation qualities and more nutrients retention especially protein and energy in chopped compared to unchopped silage. The chopped silage had lower pH and NH3N values than long silage. The lower pH of chopped (3.99) was nearly similar with findings of other workers elsewhere for well preserved high moisture grass silages (Catchpoole and Henzel 1971, Panditharatne et al 1986, Ojala et al 1988, Yakota et al 1998). The observed lower pH and NH3 N values in chopped than unchopped silage could be a result of increased affinity of the forage tissues for multiplication of lactic acid bacteria and rapid achievement of optimum anaerobic condition due to well compacted chopped pre-ensiling material that facilitated better exclusion of air. The lactic acid of chopped silage was more than 50 % of the total organic acids and butyric acid value was less than 0.5 % suggested as being important indicators of well preserved grass silage (Humphreys 1991). High DM losses observed in unchopped silage were probably due to poor fermentation because of prolonged aerobic deterioration and purification in an inefficient consolidated ensiling material. This is supported by McDonald et al (1991) who noted that oxidation of soluble sugars present in ensiled forage by the action of heterolactic bacteria result into losses of some organic constituents of the plants through carbon dioxide production. The DM in chopped silage was more degradable than in unchopped silage and thus high effective degradability values. The higher intake rate of the chopped than unchopped silage may have been indirectly influenced by its good smell, texture as well as low levels of ammonia and butyric acid concentrations.
|
Table 2: Effects of chopping elephant grass on chemical composition, in vitro dry matter digestibility, fermentation products, sensory quality, dry matter losses, rumen dry matter degradability and intake rate of the silage |
|||||
|
Parameter |
Chopped |
Unchopped |
SEM |
P- Value |
|
|
Chemical composition and in vitro digestibility |
|||||
|
DM % |
18.4 a |
17.1 b |
0.31 |
0.0189 |
|
|
g/kg DM |
|||||
|
CP |
61.1 a |
54.9 b |
0.57 |
<0.0001 |
|
|
Ash |
121.8 |
119.8 |
2.37 |
0.5668 |
|
|
NDF |
630.9 b |
674.6 a |
10.70 |
0.0206 |
|
|
ADF |
402.6 b |
444.3 a |
8.50 |
0.0298 |
|
|
ADL |
49.8 b |
60.9 a |
2.18 |
0.0067 |
|
|
WSC |
17.8 a |
13.2 b |
0.71 |
0.0018 |
|
|
IVDMD % |
51.8 a |
40.4 b |
1.06 |
<0.0001 |
|
|
IVOMD % |
52.3 a |
41.4 b |
0.92 |
<0.0001 |
|
|
Fermentation products |
|||||
|
pH |
3.99 b |
4.56 a |
0.008 |
<0.0001 |
|
|
NH3N % of total nitrogen |
4.03 b |
6.37 a |
0.293 |
0.005 |
|
|
VFA’s (g/kg DM) |
|||||
|
Lactic acid |
37.3 a |
14.2 b |
0.77 |
<0.0001 |
|
|
Acetic acid |
38.5 a |
21.8 b |
0.73 |
<0.0001 |
|
|
Propionic acid |
1.7 b |
3.7 a |
0.23 |
0.0003 |
|
|
Butyric acid |
2.6 b |
7.5 a |
0.29 |
<0.0001 |
|
|
Sensoric scores |
|||||
|
Appearance |
3.3 a |
2.6 b |
0.06 |
<0.0001 |
|
|
Smell |
3.0 a |
2.1 b |
0.06 |
<0.0001 |
|
|
Texture |
2.7 a |
1.7 b |
0.05 |
<0.0001 |
|
|
Dry matter losses |
|||||
|
DM loss as % of forage ensiled |
17.4 b |
25.7 a + |
0.89 |
0.0029 |
|
|
DM useful silage as % silage recovered |
96.3 a |
91.4 b |
0.80 |
0.0075 |
|
|
Degradability constants |
|||||
|
A |
17.2 a |
13.2 b |
0.37 |
<0.0001 |
|
|
B |
48.3 b |
52.1 a |
1.01 |
0.0298 |
|
|
A + B |
65.5 |
65.3 |
0.98 |
0.9012 |
|
|
C |
0.033 |
0.025 |
0.004 |
0.1667 |
|
|
Effective degradability % |
53.6 a |
49.6 b |
0.57 |
0.0011 |
|
|
48 hours DMD % |
54.6 a |
48.3 b |
1.23 |
0.0071 |
|
|
Intake rate |
|||||
|
Intake rate (g DM/Min) |
28.4 a |
23.3 b |
1.05 |
0.0017 |
|
|
Mean values within the same row followed by different superscripts are different at P < 0.05, Scores for sensoric quality, |
|||||
Molasses treated silages had higher DM and CP contents (Table 3). The same trend was reported for molasses treated elephant grass silage in Kenya by Otieno et al (1990). Differences in ash and fibre content between molasses treated and untreated elephant grass were not statistically significant. However, as expected molasses improved the WSC source to the lactic acid bacteria and thus produced silages with significantly high concentrations of lactic acid and low pH that inhibited the wasteful activities of clostridial bacteria which were indicated by lower levels of NH3N. Addition of molasses produced silage with high total sensoric score value that was manifested by good appearance and a pleasant smell sensed just after opening the silo. Foul smell of ammonia was sensed from unchopped silage without molasses. This was in agreement with the results of Otieno (1990). The lower DM losses observed in molasses treated than untreated silages were within the normal range of 10 to 20 % noted by Crowder and Chedda (1982) from well preserved unwilted tropical grass silages. Molasses improved the soluble fraction but could not change significantly the insoluble material and potential degradability and thus the rate of degradation of the actual rumen degradable fraction of the silage. However, effective degradability and the digestibility of the silages estimated from the 48 hours in sacco DM degradability and intake rate showed improvement through addition of molasses prior ensiling.
|
Table 3: Effects of addition of molasses on chemical composition, in vitro dry matter digestibility, fermentation products, sensory quality, dry matter losses, rumen dry matter degradability and intake rate of the elephant grass silage |
|||||
|
Parameter |
3 % Molasses |
0 %Molasses |
SEM |
P- Value |
|
|
Chemical composition and in vitro DM digestibility |
|||||
|
DM % |
18.6 a |
16.9 b |
0.31 |
0.0032 |
|
|
g/kg DM |
|||||
|
CP |
59.5 a |
56.5 b |
0.57 |
0.0056 |
|
|
Ash |
122.6 a |
118.9 b |
2.37 |
0.3168 |
|
|
NDF |
644.3 |
661.2 |
10.70 |
0.2957 |
|
|
ADF |
410.9 |
426.1 |
8.50 |
0.0896 |
|
|
ADL |
59.9 |
60.7 |
2.18 |
0.0084 |
|
|
WSC |
19.3 a |
11.7 b |
0.71 |
<0.0001 |
|
|
IVDMD % |
50.1 a |
42.1 b |
1.06 |
0.0070 |
|
|
IVOMD % |
50.7 a |
43.0 b |
0.93 |
0.0040 |
|
|
Fermentation products |
|||||
|
pH |
4.21 b |
4.43 a |
0.008 |
<0.0001 |
|
|
NH3N % of total nitrogen |
4.09 b |
6.31 a |
0.300 |
0.0007 |
|
|
VFA’s (g/kg DM) |
|||||
|
Lactic acid |
36.8 a |
14.7 b |
0.77 |
<0.0001 |
|
|
Acetic acid |
40.3 a |
20.1 b |
0.73 |
<0.0001 |
|
|
Propionic acid |
1.9 b |
3.5 a |
0.23 |
0.0010 |
|
|
Butyric acid |
3.8 b |
6.4 a |
0.29 |
0.0003 |
|
|
Sensoric scores |
|||||
|
Appearance |
3.3 a |
2.5 b |
0.059 |
<0.0001 |
|
|
Smell |
2.9 a |
2.3 b |
0.061 |
<0.0001 |
|
|
Texture |
2.4 a |
1.9 b |
0.056 |
<0.0001 |
|
|
Dry matter losses |
|||||
|
DM loss as % of forage ensiled |
19.1 b |
24.0 a |
0.89 |
0.0124 |
|
|
DM useful silage as % silage recovered |
95.8 a |
91.9 b |
0.80 |
0.0249 |
|
|
Degradability constants |
|||||
|
A |
17.2 a |
13.1 b |
0.37 |
<0.0001 |
|
|
B |
48.7 |
51.8 |
1.01 |
0.0631 |
|
|
A + B |
65.9 |
64.9 |
0.98 |
0.4803 |
|
|
C |
0.032 |
0.026 |
0.004 |
0.2958 |
|
|
Effective degradability % |
53.2 a |
49.9 b |
0.57 |
0.0040 |
|
|
48 hours DMD % |
53.4 a |
49.5 b |
1.23 |
0.00180 |
|
|
Intake rate |
|||||
|
Intake rate (g DM/Min) |
29.2 a |
22.5 b |
1.05 |
0.0001 |
|
|
Mean values within the same row followed by different superscripts are different at P < 0.05,
|
|||||
The overall quality of elephant grass silage recovered from the earth pit silos was slightly better than the one recovered from concrete silos (Table 4). This was shown by slightly higher percentages of DM, as well as CP content, associated with reasonable fermentation as shown by significantly lower pH and higher total sensoric score from silages recovered from earth pit than from concrete silos. Earth pit silos had also significantly (P < 0.05) higher in vitro DM and OM digestibility coupled with higher effective DM degradability and 48 hours percentages DM degradability. This was probably attributed by the cool environment which was maintained within the underground earth pits, whereas the concrete silos which were built above the ground, were more exposed to direct changes in ambient temperatures thereby increasing chances of the walls of the silos to absorb the excess heat which might have intervened the normal microbial fermentation and even increased the amount of DM losses. These findings agree with those of Pizarro and Vera (1980) who observed higher total DM losses on forage maize ensiled in concrete bunker and clamp silos than in trench silo with averages of 25, 35, and 9 %, respectively. The authors thus suggested the need of insulating the properly sealed concrete silos. This can be achieved by construction of a thatched roof to shade the above ground concrete silos.
|
Table 4: Effects of silo type on chemical composition, in vitro dry matter digestibility, fermentation products, sensory quality, dry matter losses, rumen dry matter degradability and intake rate of the elephant grass silage |
|||||
|
Parameter |
Earth pit silo |
Concrete Silo |
SEM |
P-Value |
|
|
Chemical composition and in vitro DM digestibility |
|||||
|
DM % |
18.7a |
16.9b |
0.31 |
0.0033 |
|
|
g/kg DM |
|||||
|
CP |
61.6a |
54.4b |
0.57 |
<0.0001 |
|
|
Ash |
126.2a |
115.4b |
2.37 |
0.0119 |
|
|
NDF |
648.1 |
657.4 |
10.74 |
0.5567 |
|
|
ADF |
417.2 |
434.1 |
8.55 |
0.2015 |
|
|
ADL |
52.2 |
68.5 |
2.18 |
0.0769 |
|
|
WSC |
15.9 |
15.1 |
0.71 |
0.4791 |
|
|
IVDMD % |
48.7a |
43.5b |
1.06 |
0.0089 |
|
|
IVOMD % |
48.9 a |
43.5 b |
0.93 |
0.0141 |
|
|
Fermentation products |
|||||
|
pH |
4.28 b |
4.35 a |
0.008 |
<0.0001 |
|
|
NH3N % of total nitrogen |
5.27 |
5.12 |
0.293 |
0.7241 |
|
|
VFA’s (g/kg DM) |
|||||
|
Lactic acid |
25.9 |
25.6 |
0.77 |
0.7095 |
|
|
Acetic acid |
26.3 b |
34.1 |
0.73 |
<0.0001 |
|
|
Propionic acid |
2.5 |
2.9 |
0.23 |
0.0010 |
|
|
Butyric acid |
4.8 |
5.3 |
0.29 |
0.2574 |
|
|
Sensoric scores |
|||||
|
Appearance |
3.1 a |
2.7 b |
0.059 |
<0.0001 |
|
|
Smell |
2.7 a |
2.4 b |
0.060 |
<0.0001 |
|
|
Texture |
2.4 a |
1.9 b |
0.050 |
<0.0001 |
|
|
Dry matter losses |
|||||
|
DM loss as % of forage ensiled |
23.0 a |
20.1 b |
0.89 |
0.0807 |
|
|
DM useful silage as % silage recovered |
94.9 a |
92.8 b |
0.80 |
0.1245 |
|
|
Degradability constants |
|||||
|
A |
17.1 a |
13.3 b |
0.37 |
<0.0001 |
|
|
B |
49.4 |
51.0 |
1.01 |
0.2932 |
|
|
A + B |
66.5 |
64.4 |
0.98 |
0.1604 |
|
|
C |
0.030 |
0.027 |
0.004 |
0.6059 |
|
|
Effective degradability % |
53.9 a |
49.3 b |
0.57 |
0.0005 |
|
|
48 hours DMD % |
54.3 a |
48.6 b |
1.23 |
0.0108 |
|
|
Intake rate |
|||||
|
Intake rate (g DM/Min) |
25.9 |
25.7 |
1.05 |
0.8452 |
|
|
Mean values within the same row followed by different superscripts are different at P < 0.05
|
|||||
Chopped and molasses treated silages had the lowest pH value and butyric acid concentration but had the highest concentrations of lactic and acetic acids (Table 5). Even with molasses, the unchopped silage had significantly (P < 0.05) higher pH value and butyric acid concentration. However, addition of molasses increased significantly acetic acid concentration in unchopped silage.
|
Table 5: Effects of chopping and addition of molasses on pH and volatile fatty acids concentration of elephant grass silage |
||||||
|
Parameter |
Unchopped |
Chopped |
SEM |
P-Value |
||
|
Molasses |
Molasses |
Molasses |
Molasses |
|||
|
pH |
4.67a |
4.63b |
4.19c |
3.79d |
0.011 |
0.0010 |
|
Lactic acid |
10.9c |
17.5b |
18.4b |
56.2a |
1.08 |
0.0078 |
|
Acetic acid |
9.9d |
33.7b |
30.2c |
46.8a |
1.03 |
0.0051 |
|
Butyric acid |
8.1a |
7.0a |
4.6b |
0.7c |
0.41 |
0.0012 |
|
Means within the same row followed by different superscripts are different at P < 0.05 |
||||||
Addition of molasses significantly (p < 0.05) lowered the pH value of silage and this was highly observed in earth pit silos than concrete silos (Table 6). Molasses significantly increased the concentration of acetic acid in the silage and this was more pronounced in silages obtained in concrete than earth pit silos. With an exception of chopped and molasses treated silages, all other silages from concrete silos had significantly (P < 0.05) lower proportion of soluble materials than all silages from earth pit silos. Essentially chopping facilitated better packing and consolidation of forage material inside the silos while molasses improved the WSC source to the lactic acid forming bacteria and thus gave a merit to earth pit silos as the most suitable structures for preservation of elephant grass silage, while chopping and addition of molasses had additional value of improving the stability of the produced silage.
|
Table 6: Effects of silo type, chopping and addition of molasses on pH, acetic acid concentration, smell and proportion of soluble materials (A) in elephant grass silage. |
||||||
|
Silo type |
Physical |
Additive |
pH |
Acetic acid |
Smell |
A |
|
Earth pit |
Chopped |
3 % Molasses |
3.81f |
43.4b |
3.6a |
18.8ab |
|
0 % Molasses |
3.96e |
25.4d |
2.5c |
17.6b |
||
|
Unchopped |
3 % Molasses |
4.67ab |
26.6d |
2.8bc |
18.9ab |
|
|
0 % Molasses |
4.70a |
9.2e |
2.1d |
12.9c |
||
|
Concrete |
Chopped |
3 % Molasses |
3.77f |
50.2a |
3.0b |
20.2a |
|
0 % Molasses |
4.41d |
34.6c |
2.8bc |
12.1cd |
||
|
Unchopped |
3 % Molasses |
4.60c |
40.9b |
2.1d |
11.0cd |
|
|
0 % Molasses |
4.64bc |
10.6e |
1.6e |
9.9d |
||
|
SEM |
0.016 |
1.46 |
0.12 |
0.74 |
||
|
P-Value |
<0.0001 |
0.0145 |
0.0014 |
0.1321 |
||
|
Means within the same column followed by different superscripts are different at P < 0.05 |
||||||
It can be concluded that in order to produce good quality elephant grass silage chopping and addition of molasses prior ensiling is necessary. The results of this study suggest that silage fermentation can be enhanced in earth pit rather than above ground concrete silos. Therefore chopping, molasses addition and earth pit silos are important in producing good quality silages from tropical fodder grasses.
The authors extend their sincere thanks to NORAD for financial support for this study.
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Received 12 March 2014; Accepted 12 March 2014; Published 5 April 2014