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The highland maize varieties (Kuleni, Jibat, and Kolba) were grown at the Holetta agricultural research center, which is located 29 km west of Addis Ababa, Ethiopia. The center is located at 9°03'28.82" E latitude and 38°30'17.59" E longitude and at an elevation of 2,400 m above sea level. The region receives 1,144 mm of rain on average each year, and the average daily temperature ranges from 6 to 21 °C.
A factorial randomized complete block design containing three factors, including varieties, cultivars, and genotypes (Kuleni, Jibat, and Kolba), harvesting stage (milk and dough stage), and length of ensiling periods (4, 6, and 8 weeks) with each combination replicated five times, was used to evaluate the quality of the silage.
Maize planting was made on a gross plot size of 15 m2 (3 m × 5 m) with a recommended space of 0.75 m between rows, followed by 0.25 m between plants. The space between plots and blocks was 1 and 1.5 m, respectively. A fine seedbed with good soil moisture content was used for planting. Two seeds were inserted into each hole before being filled with fine soil. During the sowing season, diammonium phosphate (200 kg·ha−1) was used. To maintain the ideal plant population, undesirable plants were removed after 15 d of planting. Additionally, urea (120 kg·ha−1) was administered via sprinkling during the growing season and top-dressing at the knee-high stage. The maize was harvested above the ground (10–15 cm). The part of the block in each variety was harvested at the milking stage (after 75 d of growing), and the remaining biomass was harvested at the dough stage (after 120 d of growing) after removing the cob or grain for human consumption.
For adequate compaction and consolidation, the biomass obtained at both harvesting stages was chopped (1−3 cm). For simultaneous compacting purposes, the chopped biomass was weighed, put into a plastic bag (20 cm × 30 cm), and put into a 4-L plastic bucket. By hand and intermittent tamping with a wooden stick, all plastic bags were filled to the same packing density (1,000 g per plastic bag on a fresh matter basis). The plastic bags were immediately sealed within the buckets after being neatly packed. A heavy load was placed on top of the plastic bag and incubated at room temperature to eliminate oxygen from the materials that had been ensiled.
Silage fermentation parameters
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After the ensiling periods (4, 6, and 8 weeks), the corresponding small silos were opened for the sensory parameter evaluation of the silages. As soon as the silage was opened, the thermometer was put into the silos, and then the silage temperature was recorded. The pH meter (Hanan Benchtop pH meter) was calibrated with buffer solutions (pH 4 and 7), and it was used to measure the pH values of the silage. Following a mold inspection, the silage was well mixed, and representative samples were collected and refrigerated to evaluate the pH and chemical composition of the silage. To measure the pH of the silage, a 20-g sample was taken into a beaker, mixed with 100 mL of distilled water, blended with a glass stirrer, and kept for 1 h.
Total dry matter loss was calculated as (DM of forage − DM of silage)/DM forage × 100)/DM of forage weight loss in the silage.
Physical characteristics/sensory evaluations
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The physical characteristics (colour, smell, texture, and moldiness) were assessed immediately after the silo was opened and appraised subjectively by a panel of five individuals with experience assessing the quality of silage. Before starting the real review, the panelists who were from the department of animal feeds and nutrition research program were given an introduction to the criteria (Table 1) and given an exercise. On a scale of 1−4, the silage's physical quality criteria were graded[18].
Table 1. Sensory evaluations and fermentation characteristics.
Sensory parameters Rating scale 1 2 3 4 Color Dark Olive yellow Light olive green Olive green Smell/aroma Offensive Moderately pleasant Pleasant Very pleasant Texture Slimy Soft Fairly firm Firm Mold coverage Highly moldy Moderately moldy Scattered mold spot No mold 1 = Bad, 2 = Moderate, 3 = Good, 4 = Excellent. Chemical composition
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The chemical composition and in vitro digestibility of maize silages were determined at the Holetta agricultural research center in the animal nutrition laboratory. Representative samples were taken after each ensiling period. The samples were dried in an oven at 60 °C for 72 h. The dried samples were ground to pass through a 1 mm sieve in a Wiley mill. Dry matter, crude protein, and ash contents of the silage were determined with the AOAC (1990) procedure[19]. Neutral detergent fiber, acid detergent fiber, and acid detergent lignin were determined by Van Soest et al.[20].
In vitro digestibility
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The in vitro digestibility of the feed was determined by using the two-stage method of Tilley & Terry[21]. Rumen liquor was collected and transported to the laboratory using thermos flasks and pre-warmed to 39 °C before the daily meal of the three cannulated Boran-Friesian steers. The steers were 42 months old and weighed 590 kg. The steers were fed natural pasture hay (6% CP, on a DM basis) ad libitum and a 2-kg concentrate (19.86% CP, on a DM basis) per day/head every morning. The sample (0.5 g) was incubated in a test tube at 39 °C for 48 h with 10 mL of rumen fluid and 50 mL of buffer solution. After the microbiological digestion, the enzymatic digestion with acid pepsin solution (i.e., 5 mL per tube) was continued for another 48 h. Blank samples were also incubated in duplicate with buffered rumen fluid for correction of in vitro organic matter digestibility. Digestible organic matter in the dry matter (DOMD) was determined after drying and burning the residues. Estimated metabolizable energy (ME) was calculated by using ME (MJ/kg) = 0.16*g DOMD/kg DM[22].
Statistical analysis
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Data was analyzed by using the statistical analysis system, version 9.3[23]. A 3 × 2 × 3 factorial randomized block design containing three factors such as variety (Kuleni, Jibat and Kolba) harvesting stage (milking and dough stage), and length of ensiling periods (4, 6 and 8 weeks) were subjected to analysis. Significances of differences among treatments were determined by using Tukey tests (p < 0.05). The following statistical model was used Yijkl = μ + Vi + Pj + Hk + VPHijk + Eijkl, Where, Yijkl = the dependent variable, μ = overall mean, Vi = effect of variety (i = 1, 2, 3), Pj = effect of ensiling period (j = 1, 2, 3), Hk = effect of harvesting stage (k = 1, 2), VPHijk = interaction effect, Eijkl = experimental error.
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The sensory and fermentation quality of the maize silage, including colour, aroma, texture, temperature, pH, mold and dry matter loss, showed significant variation (p < 0.05) with the interactional effect of variety × harvesting stage × ensiling period (Table 2). The Jibat maize variety harvested at the dough stage and ensiled for 6 weeks has a better (p < 0.05) silage quality (colour, aroma, and texture). However, the Kuleni variety harvested at the dough stage and ensiled for 4 and 8 weeks had a higher (p < 0.05) pH value and dry matter loss of the silage, respectively. The total dry matter loss of the silage in the Kuleni variety was higher than the silage prepared from the Jibat and Kolba maize varieties. As the incubation period increased, dry matter loss in the silage increased, but its pH value decreased. The silage prepared from Jibat and Kolba cultivars has a superior textural quality than the Kuleni cultivar.
Table 2. Effect of variety × harvesting stage × ensiling period on sensory and fermentation characteristics of the maize silage.
Variety HS EP (weeks) Colour Aroma Texture Mold pH T0 TDML Kuleni Milk 4 3.24h 3.08j 3.48j 3.72g 4.04g 19.84d 11.13p 6 3.44f 3.40h 3.64h 4.00a 3.98i 20.40b 16.40k 8 2.28j 2.48k 2.60l 2.60i 3.80i 19.54f 20.07e Jibat 4 3.36g 3.08j 3.60i 3.72g 4.00h 19.46g 6.30r 6 3.72c 3.84b 3.88c 3.80e 3.88k 21.58a 12.05o 8 3.56d 3.52g 3.76f 3.84d 3.70n 19.68e 16.59j Kolba 4 3.00i 3.20i 3.64h 3.72g 4.00h 20.06c 7.36q 6 3.00i 3.80c 3.84d 3.92b 3.74m 20.40b 13.20m 8 3.00i 3.08j 3.32k 3.60h 3.70n 19.38h 17.52h Kuleni Dough 4 3.36g 3.60f 3.76f 3.76f 4.38a 18.70k 16.76i 6 3.36g 3.60f 3.72g 3.88c 4.16d 18.74j 20.64d 8 3.56d 3.64e 3.72g 3.84d 4.04g 18.74j 22.15a Jibat 4 3.52e 3.20i 3.84d 3.80e 4.24b 18.66l 13.10n 6 4.00a 4.00a 4.00a 4.00a 4.06f 18.60n 18.09g 8 3.76b 3.84b 3.88c 3.88c 2.90o 18.60n 20.87b Kolba 4 3.00i 3.20i 3.80e 4.00a 4.22c 18.62m 14.32l 6 3.00i 3.68d 3.88c 3.80e 4.10e 19.14i 19.16f 8 3.00i 3.80c 3.92b 3.84d 3.96j 19.14i 20.67c LSD 0.006 0.006 0.006 0.004 0.006 0.005 0.006 SEM 0.01 0.02 0.01 0.005 0.01 0.02 0.01 Overall average Kuleni 3.20 3.30 3.48 3.63 4.06 19.32 17.85 Jibat 3.65 3.58 3.82 3.84 3.79 19.43 14.50 Kolba 2.99 3.30 3.73 3.81 3.94 19.45 15.37 4 3.24 3.22 3.68 3.78 4.14 19.22 11.49 6 3.42 3.72 3.82 3.90 3.98 19.81 16.59 8 3.19 3.39 3.53 3.60 3.68 19.18 19.64 Statistical effect V *** *** ** *** ** *** *** HS *** *** *** *** *** *** *** EP *** *** *** *** ** *** *** V × HS *** *** ** *** *** *** *** V × EP *** * *** *** *** *** *** HS × EP *** *** ** *** *** *** *** V × HS × EP *** *** *** *** ** *** *** a−r Means with different superscripts within the same column are significantly different (p < 0.05); V = variety, HS = harvesting stage, EP = ensiling period, LSD = least significance difference, To = silage temperature; TDML = total dry matter loss; SEM = Standard error of the mean * = p < 0.05, ** = p < 0.01, *** = p < 0.001. Chemical composition and in vitro digestibility
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The interaction effect of genotype × harvesting stage × ensiling period has a significant variation (p < 0.05) on partial dry matter (PDM), ash, crude protein (CP), and metabolizable energy, but neutral detergent fiber (NDF), acid detergent fiber (ADF), and in vitro organic matter digestibility in the dry matter (DOMD) showed no significant variation (p > 0.05) (Table 3). The PDM was higher (p < 0.05) in the Kuleni variety harvested at the dough stage and ensiled for 4 weeks, while the value of the CP was higher (p < 0.05) in the Kolba variety harvested at the milk stage and ensiled for 8 weeks. As the ensiling period lengthened, the fiber fractions of the silage declined, but the digestibility of the silage increased. The NDF, ADF, and acid detergent lignin contents of silage made up of the Jibat and Kolba maize cultivars were lower than those of silage prepared from the Kuleni maize variety, but the values of DOMD in the silage prepared from Jibat and Kolba cultivars were higher than the silage made up of the Kuleni cultivar. The higher ash and crude protein contents and the lower fiber fractions in Jibat and Kolba maize variety silages demonstrate that they are potential ruminant fodder because increasing the concentration of cell wall compounds limits feed intake and energy availability of forages in ruminants.
Table 3. Effect of variety × harvesting stage × ensiling period on chemical composition (%, DM basis) and metabolizable energy (MJ/Kg DM) of the maize silage.
Variety HS EP (weeks) PDM Ash CP NDF ADF ADL DOMD ME Kuleni MS 4 20.50k 7.98n 4.43d 60.78 33.97 3.54def 54.76 8.80i 6 19.28n 10.31i 4.24ef 59.65 32.68 3.40fg 56.46 9.00h 8 18.82o 11.12f 3.64h 59.99 32.74 3.36gh 57.36 9.20f Jibat 4 22.35h 11.96d 4.88b 59.97 31.75 3.26ghi 57.28 9.20f 6 20.98j 12.52b 5.28a 59.28 31.15 3.06kl 58.70 9.40c 8 19.89m 13.31a 4.28ef 58.70 30.24 2.73m 59.90 9.60a Kolba 4 21.54i 9.76j 4.19f 60.35 31.42 3.16ijk 56.74 9.10g 6 20.17l 10.33i 4.69c 59.23 30.94 3.01l 57.92 9.30e 8 19.22n 10.89g 5.14a 58.89 30.43 3.11jkl 58.35 9.30e Kuleni DS 4 27.05d 4.58q 3.93g 61.28 34.47 4.04a 54.46 8.70j 6 25.79f 5.74p 3.74h 60.15 33.18 3.90ab 56.16 9.00h 8 24.71g 6.07o 3.14i 60.49 33.24 3.86b 57.06 9.10g Jibat 4 28.75b 8.28m 4.38de 60.47 32.25 3.76bc 56.98 9.10g 6 27.10d 8.98l 4.78bc 59.78 31.65 3.56de 58.40 9.35d 8 25.93f 9.38k 3.78h 59.20 30.74 3.23hij 59.60 9.50b Kuleni 4 29.51a 10.49h 3.69h 60.85 31.92 3.66cd 56.44 9.00h 6 27.84c 12.36c 4.19f 59.73 31.44 3.51ef 57.62 9.20f 8 26.85e 11.36e 4.64c 59.39 30.93 3.61de 58.05 9.30e LSD 0.15 0.15 0.13 0.15 0.14 0.12 0.16 0.15 SE 0.02 0.01 0.03 0.04 0.02 0.03 0.03 0.01 Overall average Kuleni 22.69 7.63 3.85 60.39 33.38 3.68 56.04 8.97 Jibat 24.17 10.74 4.56 59.57 31.30 3.27 58.48 9.34 Kolba 24.19 10.87 4.42 59.74 31.18 3.34 57.52 9.20 4 24.95 10.36 4.25 60.62 32.63 3.57 56.11 8.98 6 23.53 10.04 4.49 59.64 31.84 3.41 57.54 9.21 8 22.57 8.84 4.10 59.44 31.39 3.32 58.39 9.33 Statistical effect V *** *** *** *** *** *** *** *** HS *** *** *** *** *** *** *** *** EP *** *** *** *** *** *** *** *** V × HS *** *** NS NS NS NS NS NS V × EP *** *** *** *** *** *** *** *** HS × EP *** *** NS NS NS NS NS ** V × HS× EP ** *** * NS NS ** NS *** a−r Means with different superscripts within the same column are significantly different (p < 0.05); V = variety, HS = harvesting stage, EP = ensiling period, LSD = least significance difference, To = silage temperature; TDML = total dry matter loss; SEM = Standard error of the mean * = p < 0.05, ** = p < 0.01, *** = p < 0.001, NS = Non significance, DS = Dough stage, MS = Milk stage, neutral detergent fiber (NDF), and acid detergent fiber (ADF). -
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
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Cite this article
Kitaw G, Terefe G, Faji M, Mengistu G, Dejene M, et al. 2024. Effect of maize (Zea mays L.) genotypes, harvesting stages and ensiling periods on fermentation and nutritional value of silage. Grass Research 4: e009 doi: 10.48130/grares-0024-0006
Sensory parameters | Rating scale | |||
1 | 2 | 3 | 4 | |
Color | Dark | Olive yellow | Light olive green | Olive green |
Smell/aroma | Offensive | Moderately pleasant | Pleasant | Very pleasant |
Texture | Slimy | Soft | Fairly firm | Firm |
Mold coverage | Highly moldy | Moderately moldy | Scattered mold spot | No mold |
1 = Bad, 2 = Moderate, 3 = Good, 4 = Excellent. |