ABSTRACT
The objective of the study is to, evaluate and optimize the process parameters for effective drying of two high energy forage plant species indigenous to South-east Nigeria for hay making. Two forage grasses which includes Andropogon tectorum (Gamba grass) and Pennisetum purpureum (Elephant grass) was identified and selected based on their proximate compositions. The forage grasses were dried from 70.9 - 10 ± 3 % to 60 – 10 ± 1% (w.b) for Elephant and Gamba grass respectively using sun, hot air oven (40 -70 oC) and microwave oven (180 to 720 W) drying methods. In hot air oven drying method, increasing the drying temperature, rapidly increased the drying rate from 31.5 to 64.5 kg water/kg dry matter/hour for Elephant grass (Pennisetum purpureum) and from 5.8 to 51.0 kg water/kg dry matter/hour for Gamba grass (Andropogon tectorum) within the first one hour of drying. Similarly, increasing microwave power increased drying rate from 915.6 to 2790.2 kg water/kg dry matter/hour and 189.5 to 1432.3 kg water/kg dry matter/hour within the first 3 minutes of drying Elephant grass (Pennisetum purpureum) and Gamba grass (Andropogon tectorum), respectively. The result of analysis showed that specific energy consumption in hot air oven drying ranges between 12.2 to 14.7 kWh/ kg water, and 24.1 to 29.1 kWh/kg water for Elephant grass (Pennisetum purpureum) and Gamba grass (Andropogon tectorum) varieties, respectively. While the specific energy consumption in microwave drying is between 22.9 to 51.5 kWh/kg water and 33.2 to 81.5 kWh/kg water for Elephant grass and Gamba grass varieties respectively. Again, specific moisture extraction rate in hot air oven drying is between 0.65 to 0.94 kg water/kWh and 0.28 to 0.38 kg water/kWh for Elephant grass (Pennisetum purpureum) and Gamba grass (Andropogon tectorum) varieties respectively. Whereas, specific moisture extraction rate in microwave drying is between 6.3 to 10.0 kg water/kWh, and 2.2 to 8.9 kg water/kWh for Elephant grass (Pennisetum purpureum) and Gamba grass (Andropogon tectorum) varieties respectively. Also the nutrient content analysis showed that increasing drying temperatures and microwave radiation generally increased the dry matter from 29.4 to 94.5% and crude fiber from 9.2 to 55.1%, whereas, the crude protein content decreased from 10.8 to 5.3% in the dried samples. Again, whereas total colour difference showed sharp variation with temperature changes, changes in microwave power level showed slight variation. There was a decreasing trend of rehydration ratio when the hot air oven drying temperatures and microwave power levels were increased. Using response surface methodology (RSM), reliable prediction equations were developed, and the following optimum drying conditions were indicated: maximizing drying rate resulted in a drying time of 1.4hours, drying temperature of 68.8℃ at a drying rate of 52.5 kg water/kg dry matter/hour for hot air oven drying method, whereas it gave a drying time of 0.083hours, drying power level of 720W and drying rate of 416.1 kg water/kg dry matter/hour in microwave method. The optimization of crude fiber (%) in hot air oven method resulted in a dry matter of 92.4, drying temperature of 70℃ with a crude fiber of 51.7%, while in microwave method, optimum conditions were achieved at drying power level of 360W, with 47.6% crude fiber and 93.13% dry matter values. Optimal value of 10.8 % crude protein in hot air oven was reached at drying temperature of 28.5oC, and dry matter of 39.8 (%), while 11.03% crude protein was reached at drying power level of 59.5W and 49.50% dry matter in microwave method.
TABLE OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of Content vi
List of Tables ix
List of Figures xv
List of Plates xix
Abstract xx
CHAPTER 1: INTRODUCTION 1
1.1 Background of the Study 1
1.2 Statement of the Problem 6
1.3 Objectives of the Study 8
1.4 Specific Objectives of the Study 8
1.5 Justification of the Study 9
1.6 Scope of the Study 9
CHAPTER 2: REVIEW OF RELATED LITERATURE 11
2.1 Nigeria Forage Resource Profiles 11
2.2 Quality of Forage Feedstuff 14
2.3 Forage Conservation Methods 20
2.4 Drying Methods for Agricultural Products 23
2.5 Effect of Drying Process Parameters on Drying Kinetics and
Quality of Agricultural Products 29
2.6 Knowledge Gap 37
CHAPTER 3: MATERIALS AND METHODS 38
3.1 Sample Selection and Preparation 38
3.2 Experimental Drying Procedures 39
3.3 Analytical and Sensory Test Procedures 40
3.3.1 Nutrient content analysis 40
3.3.1.1 Determination of crude protein 41
3.3.1.2 Determination of fat 41
3.3.1.3 Determination of crude fibre (lipid) 42
3.3.1.4 Determination of ash content 43
3.3.1.5 Determination of carbohydrate content 43
3.3.2 Colour analysis 44
3.3.3 Statistical analysis and optimization 45
3.3.4 The grass hay shelf life quality test 46
3.4 Determination of Moisture Levels, Drying Kinetics and
Energy Consumptions 47
3.4.1 Determination of moisture content levels 47
3.4.2 Determination of moisture ratio for oven, microwave and sun drying 48
3.4.3 Determination of drying rate for oven, microwave and sun drying 48
3.4.4 Determination of energy consumption in hot air oven drying method 49
3.4.5 Determination of specific energy consumption in hot air oven drying 50
3.4.6 Determination of specific moisture extraction rate for hot air drying 50
3.4.7 Determination of energy consumption in microwave drying method 51
3.4.8 Determination of specific energy consumption in microwave drying 51
3.4.9 Determination of specific moisture extraction rate for microwave drying 51
3.4.10 Determination of the rehydration ratio 52
CHAPTER 4: RESULTS AND DISCUSSION 53
4.1 Response of Drying Kinetics under Different Drying Treatments
of Elephant grass (Pennisetum purpureum) and
Gamba grass (Andropogon tectorum) 53
4.2 Energy Consumption and Moisture Extraction Rate at
Different Treatment Levels 65
4.3 Effect of Drying Treatments on Nutritional Quality of the
Forage Grasses 82
4.4 Effect of Drying Treatments on the Surface Colour of the
Forage Grasses 96
4.5 Rehydration Ratio (Index) of Forage Grasses after Different
Drying Treatments 99
4.6 Comparing Nutrient Value after 30 Days of Storing the Dried Grasses 101
CHAPTER 5: CONCLUSION AND RECOMMENDATION 105
5.1 Conclusion 105
5.2 Recommendations 107
5.3 Contribution to Knowledge 107
References 108
Appendices 113
LIST OF TABLE
2.1: Nutrient content of different hays 15
2.2: Proximate composition of selected forage grasses 20
4.1: ANOVA evaluation of linear and interaction terms for
response (drying rate) on drying of Elephant grass
(Pennisetum purpureum) in hot air oven 58
4.2: ANOVA evaluation of linear and interaction terms for
response (drying rate) on drying of Gamba grass
(Andropogon tectorum) in hot air oven 59
4.3: ANOVA evaluation of linear and interaction terms for
response (drying rate) on drying of Elephant grass
(Pennisetum purpureum) in microwave dryer 62
4.4: ANOVA evaluation of linear and interaction terms for
response (drying rate) on drying of Gamba grass
(Andropogon tectorum) in microwave dryer 62
4.5: ANOVA evaluation of linear and interaction terms for
response (Specific Moisture Extraction Rate) on drying of
Elephant grass (Pennisetum purpureum) in hot air oven 69
4.6: ANOVA evaluation of linear and interaction terms for
response (Specific Moisture Extraction Rate) on drying of
Gamba grass (Andropogon tectorum) in hot air oven 69
4.7: ANOVA evaluation of linear and interaction terms for
response (Specific Moisture Extraction Rate) on drying of
Elephant grass (Pennisetum purpureum) in microwave dryer 73
4.8: ANOVA evaluation of linear and interaction terms for
response (Specific Moisture Extraction Rate) on drying of
Gamba grass (Andropogon tectorum) in microwave dryer 73
4.9: ANOVA evaluation of linear and interaction terms for
response (Specific Energy consumption) on drying of
Elephant grass (Pennisetum purpureum) in hot air oven 76
4.10: ANOVA evaluation of linear and interaction terms for
response (Specific Energy consumption) on drying of
Gamba grass (Andropogon tectorum) in hot air oven 76
4.11: ANOVA evaluation of linear and interaction terms for
response (Specific Energy consumption) on drying of
Elephant grass (Pennisetum purpureum) in microwave dryer 79
4.12: ANOVA evaluation of linear and interaction terms for
response (Specific Energy consumption) on drying of
Gamba grass (Andropogon tectorum) in microwave oven 79
4.13: ANOVA evaluation of linear and interaction terms for
response (Crude protein) on drying of Elephant grass
(Pennisetum purpureum) in hot air oven 86
4.14: ANOVA evaluation of linear and interaction terms for
response (Crude fibre) on drying of Elephant grass
(Pennisetum purpureum) in hot air oven 86
4.15: ANOVA evaluation of linear and interaction terms for
response (Crude protein) on drying of Gamba grass
(Andropogon tectorum) in hot air oven 87
4.16: ANOVA evaluation of linear and interaction terms for
response (Crude fibre) on drying of Gamba grass
(Andropogon tectorum) in hot air oven 87
4.17: ANOVA evaluation of linear and interaction terms for
response (Crude protein) on drying of Elephant grass
(Pennisetum purpureum) in microwave oven 91
4.18: ANOVA evaluation of linear and interaction terms for
response (Crude fibre) on drying of Elephant grass
(Pennisetum purpureum) in microwave oven 91
4.19: ANOVA evaluation of linear and interaction terms for
response (Crude protein) on drying of Gamba grass
(Andropogon tectorum) in microwave oven 92
4.20: ANOVA evaluation of linear and interaction terms for
response (Crude fiber) on drying of Gamba grass
(Andropogon tectorum) in microwave oven 92
A1: Weight of Sun-dried sample (g) of the grass varieties 113
A2: Weight of Hot Air Oven dried sample (g) of Elephant grass 113
A3: Weight of Hot Air Oven dried sample (g) of Gamba grass 113
A4: Weight of Microwave dried sample (g) of Elephant grass 114
A5: Weight of Microwave dried sample (g) of Gamba grass 114
A6: Moisture Content (Mt), (kg water/kg dry matter) at time t,
(hour), the dimensionless Moisture ratio (MR), and the Drying
rate (DR) (kg water/kg dry matter/hour) during the hot air oven
drying process of Elephant grass variety 115
A7: Moisture Content (Mt), (kg water/kg dry matter) at time t,
(hour), the dimensionless Moisture ratio (MR), and the Drying
rate (DR) (kg water/kg dry matter/hour) during the hot air oven
drying process of Gamba grass variety 116
A8: Moisture Content (Mt), (kg water/kg dry matter) at time t,
(hour), the dimensionless Moisture ratio (MR), and the Drying
rate (DR) (kg water/kg dry matter/hour) during the Microwave
drying process of Elephant grass variety 117
A9: Moisture Content (Mt), (kg water/kg dry matter) at time t,
(hour), the dimensionless Moisture ratio (MR), and the Drying
rate (DR) (kg water/kg dry matter/hour) during the Microwave
drying process Gamba grass variety 119
A10: Moisture Content (Mt), (kg water/kg dry matter) at time t,
(hour), the dimensionless Moisture ratio (MR), and the Drying
rate (DR) (kg water/kg dry matter/hour) during the Sun drying
process of Elephant grass and Gamba grass varieties 121
B1: Nutrient composition (%) of fresh grass varieties 122
B2: Nutrient composition (%) of grass varieties Sun dried 122
B3: Nutrient composition (%) of Elephant grass dried with Hot
Air Oven 122
B4: Nutrient composition (%) of Gamba grass dried with Hot
Air Oven 123
B5: Nutrient composition (%) of Elephant grass
dried with Microwave 123
B6: Nutrient composition (%) of Gamba grass
dried with Microwave 124
C1: Colour wavelength values for Elephant grass
dried with hot air oven 125
C2: Colour wavelength values for Gamba grass
dried with hot air oven 125
C3: Colour wavelength values for Elephant grass
dried with microwave 125
C4: Colour wavelength values for Gamba grass
dried with microwave 126
C5: Colour wavelength values for grasses dried in the Sun 126
C6: Values of Colour parameters from Hot Air Oven dried
sample of Elephant grass 127
C7: Values of Colour parameters from Hot Air Oven dried
sample of Gamba grass 127
C8: Values of Colour parameters from Microwave dried
sample of Elephant grass 128
C9: Values of Colour parameters from Microwave dried
sample of Gamba grass 129
D1: Energy consumption (E_c), (kWh) per batch, the specific
energy consumption (kWh/kg), and the specific moisture
extraction rate (kg water/KWh/h) during the process of hot air
oven drying of Elephant grass variety 130
D2: Energy consumption (E_c), (kWh) per batch, the specific
energy consumption (kWh/kg), and the specific moisture
extraction rate (kg water/KWh/h) during the process of hot air
oven drying of Gamba grass variety 131
D3: Energy consumption (E_c), (kWh) per batch, the specific
energy consumption (kWh/kg), and the specific moisture
extraction rate (kg water/KWh/h) during the process of
Microwave drying of Elephant grass variety 132
D4: Energy consumption (E_c), (kWh) per batch, the specific
energy consumption (kWh/kg), and the specific moisture
extraction rate (kg water/KWh/h) during the process of
Microwave drying of Gamba grass variety 133
E1: Rehydration ratio of sample of Elephant grass
variety dried in hot air oven 134
E2: Rehydration ratio of sample of Gamba grass
variety dried in hot air oven 134
E3: Rehydration ratio of sample of Elephant grass
variety dried in Microwave 134
E4: Rehydration ratio of sample of Gamba grass
variety dried in Microwave 135
E5: Rehydration ratio of sample of Elephant grass
and Gamba grass varieties dried in Sun 135
F1: Nutrient composition (%) after 30 days of drying
Elephant grass with Hot Air Oven 136
F2: Nutrient composition (%) after 30 days of drying
Gamba grass with Hot Air Oven 136
F3: Nutrient composition (%) after 30 days of drying
Elephant grass with Microwave 137
F4: Nutrient composition (%) after 30 days of drying
Gamba grass with Microwave 137
LIST OF FIGURE
4.1: Moisture ratio of Pennisetum Purpureum and Andropogon Tectorum for different drying treatments (A) Pennisetum Purpureum hot air oven (B) Andropogon Tectorum hot air oven (C) Pennisetum Purpureum Micro wave oven (D)
Andropogon Tectorum Microwave Oven 53
4.2: Drying Rate of Pennisetum Purpureum and Andropogon
Tectorum for different dying treatments (A) Pennisetum
Purpureum hot air oven (B) Andropogon Tectorum hot air
oven (C) Pennisetum Purpureum Micro wave oven (D) Andropogon Tectorum Microwave Oven 55
4.3: Moisture ratio for sun drying 56
4.4: Drying Rate for sun drying 57
4.5: Effect of drying temperature and time on drying rate shown in (A) 3D plots for hot air oven dried Pennisetum purpureum (B) Contour plots for hot air oven dried Pennisetum purpureum grass sample, (C) 3D plots for hot air oven dried Andropogon tectorum grass sample (D) Contour plots for hot air oven dried Andropogon Tectorum grass sample 61
4.6: Effect of Drying power level and Time on drying rate of shown in(A) 3D plots and (B) Contour plots for microwave dried
Pennisetum purpureum grass sample, (C) 3D plots and
(D) Contour plots for microwave dried Andropogon
tectorum Grass sample 65
4.7: Effect of hot air oven drying on (A) Specific Energy
Consumption (SEC) of Pennisetum purpureum, and
Andropogon tectorum grass (B) Specific Moistrue Extraction
Rate (SMER) of Pennisetum purpureum and
Andropogon tectorum grass 66
4.8: Effect of microwave drying on (A) Specific Energy Consumption (SEC) of Pennisetum purpureum, and Andropogon tectorum grass (B) Specific Moistrue Extraction Rate (SMER) of Pennisetum purpureum and Andropogon tectorum grass 67
4.9: Effect of Drying Temperature and Drying Time on Specific
Moisture Extraction Rate shown in, (A) 3D plot and (B) Contour plot for Pennisetum purpureum dried sample, and (C) 3D plot and (D) Contour plot for Adropogon tectorum dried sample 72
4.10: Effect of Drying Power Level and Drying Time on Specific
Moisture Extraction Rate shown in (A) 3D plot and (B) Contour plot for Pennisetum purpureum dried sample, and (C) 3D plot and (D) Contour plot for Adropogon tectorum dried sample 75
4.11 Effect of hot air oven drying temperatures and drying time on specific energy consumption shown in, (A) 3-D plot and (B) contour plot for Elephant grass (Pennisetum purpureum)
dried sample 78
4.12 Effect of hot air oven drying temperatures and drying time on specific energy consumption shown in, (A) 3-D plot and (B) contour plot for Gamba grass (Andropogon tectorum)
dried sample 78
4.13: Effect of microwave drying power levels on nutrient content of Pennisetum purpureum grass 81
4.14: Effect of microwave drying power levels on nutrient content of Andropogon tectorum grass 82
4.15: Effect of Sun drying on nutrient content of forage grass species 83
4.16: Effect of hot air oven drying temperatures on nutrient content of Elephant grass (Pennisetum purpureum) 83
4.17: Effect of hot air oven drying temperatures on nutrient content of Gamba grass (Andropogon tectorum) 84
4.18: Effect of microwave drying power levels on nutrient content of Elephant grass (Pennisetum purpureum) 84
4.19: Effect of microwave drying power levels on nutrient content of Gamba grass (Andropogon tectorum) 85
4.20: Effect of Drying Temperature and Dry Matter on crude protein and fiber shown in (A) Crude Protein 3D plot for Pennisetum purpureum (B) Crude Protein Contour plot for Pennisetum purpureum (C) Crude Fiber 3D plot Pennisetum purpureum (D) Crude fiber Contour plot for Pennisetum purpureum (E) Crude Protein 3D plot for Adropogon tectorum (F) Crude Protein Contour plot for Adropogon tectorum (G) Crude Fiber 3D plot for Adropogon tectorum (H) Crude fiber Contour plot for Adropogon tectorum 90
4.21: Effect of Drying Power Level and Dry Matter on Crude Fiber shown in (A) 3D plot and (B) Contour plot for Pennisetum purpureum dried sample 94
4.22: Effect of Drying Power Level and Dry Matter on Crude Protein shown in (A) 3D plot and (B) Contour plot for Pennisetum purpureum dried sample 95
4.23: Effect of Drying Power Level and Dry Matter on Crude Fiber shown in (A) 3D plot and (B) Contour plot for Andropogon tectorum dried sample 95
4.24: Effect of Drying Power Level and Dry Matter on Crude Protein shown in (A) 3D plot and (B) Contour plot for Andropogon tectorum dried sample 96
4.25: Variation of colour parameter values during hot air oven
drying of (A) Pennisetum purpureum grass, (B) Andropogon
tectorum grasses at 40, 50, 60 and 70oC 97
4.26: Variation of colour parameter values during microwave
drying of (A) Pennisetum purpureum grass, (B) Andropogon
tectorum grasses at 180, 360, 540 and 720W 98
4.27: Effect of hot air temperature, microwave power and sun
drying on the rehydration ratio of Pennisetum purpureum grass 100
4.28: Effect of hot air temperature, microwave power and sun
drying on the rehydration ratio of Andropogon tectorum grass 101
4.29: Effect of hot air oven drying temperatures (40, 50, 60 and 70oC) on nutrient content after 30 days of dried sample of (A)
Pennisetum purpureum grass, (B) Andropogon tectorum grass 102
4.30: Effect of microwave drying power levels (180, 360, 540 and 720W) on nutrient content after 30 days of dried sample of (A) Pennisetum purpureum grass, (B) Andropogon tectorum grass 103
LIST OF PLATE
1.1: Young Gamba Grass (Andropogon tectorum cv. ikporoto) plant 1
1.2: Matured Gamba Grass (Andropogon tectorum cv. ikporoto) plant 1
1.3: Young Elephant Grass (Pennisetum Purpureum. cv. Achara Nwankita) plant 2
1.4: Matured Elephant Grass (Pennisetum Purpureum. cv. Achara Nwankita) plant 2
3.1: Preparing the Sample Grasses for Drying 38
G1: Bales of Hay of various type and colour 138
G2: alfalfa hay 138
G3: orchard grass hay 139
G4: another colour of orchard grass hay 139
G5: Timothy grass hay 140
G6: oat hay 140
G7: straw hay 141
G8: Drying samples in a Hot air oven 141
G9: Drying samples in Microwave 142
G10: Dried grass sample 142
G11: Analyzing dried samples in NRCRI Laboratory 142
G12: Dried Samples prepared for analysis 143
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Generally, forage consists of plant materials (including plant stems and leaves) eaten directly as pasture by grazing animals or cut for fodder and carried to the animals as hay or silage. It forms the basic feedstuff for ruminant livestock production, and is sorted into different categories as grasses, legumes, forbs and woody plants (de Lima et al., 2015). The main constituent of forage in pasture fields and silage (cut and carry method) across South-eastern Nigeria is grasses, and these include common species such as Elephant grass (Pennisetum Purpureum. cv. Achara Nwankita), Gamba grass (Andropogon Gayanus. cv. ikporoto), and Guinea grass (Panicum maximum) usually collected and fed to tethered animals (goats and sheep), Plate 1.1, 1.2, 1.3 and 1.4. Others are Cynodon dactylon, Andropogon tectorum, Bracharia decumbens, Cenchrus ciliaris, Cynodon plectostachyus, Digitaria decubens, Hyparrhenia rufa, Melinis minutfilora, and Tripsacum laxum.
Plate 1.1: Young Gamba Grass (Andropogon tectorum cv. ikporoto)
Plate 1.2: Matured Gamba Grass (Andropogon tectorum cv. ikporoto)
Plate 1.3: Young Elephant Grass (Pennisetum Purpureum. cv. Achara Nwankita)
Plate 1.4: Matured Elephant Grass (Pennisetum Purpureum. cv. Achara Nwankita)
Oyeleye (2016) revealed that research studies showed clear nutritional advantages from beef, milk, and milk-derived foods obtained from 100 per cent grass-fed ruminants (cows, goats and sheep). These forage grasses are vegetation consisting of short plants with long, narrow leaves, growing wild or cultivated on lawns and pasture, and as a fodder crop (Oyeleye, 2016). Literature surveyed showed that Nigerian forage grass resources have a well-established profile, which has been distorted by the activities of felling, clearing and burning of trees, leading to the replacement of the trees with a mixture of grasses and scattered trees at the inland side of the tropical high forest vegetative zone of the country which include the South-eastern Nigeria. It has also been shown that these forage grasses have been found to adapt to, and are suitable for production at the south of derived savanna vegetative zone of Nigeria (Reynolds, 2009).
Similarly, the herdsmen discovered that communities in South-east are very suitable for grazing their cattle (Okoli, 2017). This ensuing profile attracted the nomadic herdsmen to move their livestock to the South-east sub humid zone, which has a high potential for ruminant production because of high rainfall and vast land area for forage production, especially the grasses. Additionally, the Fulani herdsmen were said to have fled their home towns following the activities of Boko Haram sect in some Northern parts of the country to seek for better grazing field in South-east of the country (Usman, 2016).
Moreover, Animal grazing (livestock feeding on the grasses at the pasture sites) is preferred where enough pasture or range land is available (Opejobi, 2016), and when the weather permits grazing (Ball et al., 2001). But the scanty land area available for grazing does not support extensive or free range livestock management system in the South-east.
Therefore, these challenges endorse the call by the Minister of Agriculture and Rural Development, Chief Audu Ogbeh (2015-2019) for Nigeria to change the system of ruminants (cattle, sheep and goat) husbandry in Nigeria from extensive system to intensive system of keeping animals in paddocks and feedlot (Oyeleye, 2016). These animals kept in confined environments will require adequate supplies of quality grasses and other forms of animal feeds. Consequently, the opportunity cost of conserving the grasses in the form of silage or hays especially during the rainy season and stored or sold to herders during the dry season to keep feed supply constant all-year-round (Oyeleye, 2016) is thus uncovered. More so, the grazing land is limited and apparent need to feed the livestock round the year within South-eastern enclave has become a problem, therefore the option of silage and hay making is considered more practical solution to provide stored and transportable fodder which can be fed to cattle, goat, sheep and other ruminants in this zone.
The forage grass conservation methods include cutting, drying, hay making and the silage making. (de Lima et al., 2015). The purpose of conservation of forage after cutting is to speed up drying, or may be to cart them for further processing (e.g. pellets) and storage (Porter, 2009; de Lima et al., 2015). Hay making remains an important conservation method in terms of total production of fodder amongst most of the developed countries (Culpin, 1981). Hay is fed as livestock feed to confined ruminants where grazing is not suitable due to unfavorable weather, or restriction of animal movement due to state law or due to practice of intensive system of husbandry. It is fed to animals kept in paddocks, feedlot or ranches which are unable to access pasture. Grass hay is the base of the ration for all grazing livestock, (Buffett, 2010) and can supply the sufficient feed required by these animals. However, deferent types of livestock require grass hay similar to grasses suitable for their consumption while grazing. The produced hay must meet the taste of the cattle, sheep and goats (generally referred to as ruminants) in nutrient content, palatability, digestibility, appeal, storability (Oyeleye, 2016) and obtained at affordable production cost.
Good quality hay is green and not too coarse, and includes plant heads and leaves as well as stems (Porter, 2009; de Lima et al., 2015). Samples of different types of hay product are shown in Appendix plates G1 to G7. High quality hay grasses are generally highly palatable and the higher the palatability and forage quality, the higher the intake and digestibility. Once digested, it is the provision of adequate level of nutrients that can produce the desired animal response. These nutrients are divided into two categories: (1) cell content components, such as protein, sugar, and starch. (2) Structural components of the cell wall, such as the cellulose, hemicelluloses, and lignin (Ball et al., 2001). Grass hay making operations generally, consist of cutting, drying, and storing of the forage grass for use as animal feedstuff for ruminants (Porter, 2009). The drying operation has more influence on the hay quality than the other two operations.
Drying operation as a process of reducing moisture content in any fresh grass, to a safe and stable shelf level, thereby playing main role in converting green, fresh, forage to a product which can be safely stored and transported without risk of spoilage (de Lucia and Assennato, 1994). This implies that the process parameters employed in drying the materials must be suitable, and methods applied must be appropriate to ensure optimum and economical drying system. Similarly, the essential quality requirement of forage grasses must be assayed through standard analytical and sensory evaluation processes (Ball et al., 2001).
In natural drying of forage crop for hay making, the stems dry last; the leaves dry first and become brittle and drop to the ground (Culpin, 1981). Conditioning which involves crushing or cracking of the cut plant, is usually introduced to equalize the drying of the stems and the leaves, and enhance the drying process (Stone and Gulvin, 1977). Hay making reduces the effect of sun bleaching, rain and dew leaching, and the chances of rain damage. However, hay conservation process may still result in losses of nutrients contained in the crop. The waste are both visible waste due to leaching and shatter losses in the field, as well as waste due to respiration and molding losses before and during storage (Ball et al., 2001). However, as the moisture content of the plant leaves and stems fall, the respiration activities subside and molding effect greatly reduced. Therefore, lowering of the moisture content through the drying process is imperative, to achieve a stable longer shelf life of the hay grasses.
Drying is defined by (Erbay and Icier, 2010) as a unit operation that converts a liquid, solid, or semi-solid feed material into a solid product of significantly lower moisture content. The drying thermal energy employed causes water to evaporate into the vapour phase, and picking up of moisture by a stream of drying air depends on the fact that the moisture in the crop/grass tends to come into a state of equilibrium with the drying air (Valarmathi et al., 2017). However, the amount of water that a given volume of air can carry increases rapidly with temperature. Drying temperatures employed are usually as high as they can safely be, without causing damage to the hay grass being dried, or leading to inefficient operation in any way (de Lucia and Assennato, 1994; Valarmathi et al., 2017), especially with the increasing fuel cost, which substantially increases the drying cost. Hence, this reason justifies the need to determine the optimum drying temperatures and other processing parameters of forage grass species for livestock feed preparation within the South-eastern Nigeria. Optimizing drying operation consists of rationalizing both the consumption of energy required and safeguarding the quality of the dried product (Koukouch et al., 2016). Moreover, drying process greatly impacts on the hay quality, especially the nutrient content. If proper consideration is not given to the drying methods and processes, it may reduce animal’s performance level, which in turn reduces potential income. Therefore, this study seeks to evaluate the effect of drying temperatures and methods on grass hay quality through the analysis of the proximate composition of the dried product. Proximate composition analysis is test performed to determine the amounts of protein, moisture, fat, fiber, and ash (magnesium and phosphorus) contents of the forage grass samples. Similarly, forage colour can change during drying due to chemical and biochemical reactions, depending on drying methods and the processing parameters used (Bonazzi and Dumoulin, 2011). The change in colour is indicative of the forage quality and nutrient digestibility, therefore the colour parameter is also evaluated. Equally, other process parameters of the drying process are determined to provide information for effective drying of grasses.
1.2 STATEMENT OF THE PROBLEM
Forage plants such as forage grasses and legumes growing on the vast fertile land of South-Eastern communities of Nigeria are extremely suitable for ruminants (cattle, sheep and goats) husbandry. It is so available in large quantity to attract the roaming Nomadic Fulani herdsmen, who move their herds to the South-east zone to graze their cattle on these forage grasses, as well to escape the activities of Boko Haram sect in some Northern parts of Nigeria. However, the massive incursions of the extensive free range and livestock roaming into crop farms in the South-east communities for uncontrolled cattle grazing could not be sustained because of insufficient grazing field, lots of devastation on crops and degradation of farmlands unprotected to erosion, and ensuing feud between herdsmen and farmers which resulted in bloodbath. Hence there is need to change the extensive method of nomadism and roaming of livestock to the intensive method and better organized system of keeping animals in paddocks and feedlot within the South-east Nigeria. This proposed change in husbandry, goes with the challenge to produce adequate supply of feeding stuff for such livestock in confinement, which must include conserved grasses of same type, nutrient content, palatability, digestibility and appeal as the ones they graze on at the pastures.
Furthermore, grasses cut and carried to the animals as fodder or conserved during the long rainy season in the form of silage or hay are to be stored to provide adequate supply of feed all year round. However, the main operation in the processing of grass hay (forage) capable of influencing the quality, shelf life and acceptability of the product is drying. Good drying process should enhance preservation and storage of the forage grass, retain nutrient adequately, maintain natural colour of the grasses, and remain palatable, digestible, of good appeal and economical. Therefore, information on the optimized process parameters and its effect on drying kinetics and quality in artificial drying of the forage species indigenous to South- east Nigeria are relevant to achieve optimal design and operation of the drying systems and production of high-quality forage. In view of the scanty information of these data in literature, this study is imperative to determine the optimized process parameters for artificial drying of forage grass which will be of great benefits to farmers engaged on hay making. It will also encourage and promote hay making amongst South- eastern Nigeria livestock farmers.
1.3 OBJECTIVES OF THE STUDY
Since the main operation in hay making is the drying process, the overall objective of this study is to experimentally evaluate and optimize the effect of process parameters and methods in drying of the two species of these forages’ grasses: Elephant grass (Pennisetum purpereum) and Gamba grass (Andropogon tectorum) in Hay making.
1.4 SPECIFIC OBJECTIVES OF THE STUDY
The specific objectives of the study are to determine:
i. the drying kinetics of Andropogon tectorum and Pennisetum purpereum under different drying treatments.
ii. the energy consumption and moisture extraction rate for different drying treatments
iii. the effect of drying treatments on the nutritional quality of Andropogon tectorum and Pennisetum purpereum during drying and storage
iv. the effect of drying treatments on the colour quality of Elephant grass and Gamba grass used for haymaking
v. the rehydration ratio (index) of grasses after drying for different treatments
vi. the optimization of drying parameters for the forage grasses using response surface methodology (RSM)
vi. comparing nutrient value after 30 days of drying process
1.5 JUSTIFICATION OF THE STUDY
The need to know the forage drying operations and thereby guarantee that it is carried out as efficient as possible within the economic limitations of the market (Lopez et al., 2015) justifies the determination of information on the optimum drying process parameters for the artificial drying of forage grass. The data will help hay makers produce at optimum condition, a high nutrient content forage, and at acceptable product colour. These data can also facilitate the production of palatable, digestible and longer shelf life grass hay. More so, new enterprise on the production of grass hay to be sold to the livestock farmers will develop, and as such a new source of income to the crop farmers will be created. The livestock farmers can now be encouraged to adopt the intensive method and better organized system of keeping animals in paddocks and feedlot with full assurance of being supplied with forage grass that is sufficient throughout the year, particularly through the period of drought or dry season, and at affordable price. This system will boost dairy production and supply chain, create business opportunities and reduce the country’s dependence on importation of dairy products. Further processing of dried grass can extend to production of pellets and addition of other feed ration to improve the feeding quality and well-being of the livestock.
1.6 SCOPE OF THE STUDY
This present study is limited to the evaluation and optimization of the drying process parameters for two species of forage grass: Southern Gamba grass (Andropogon tectorum cv. ikporoto), and Elephant grass (Pennisetum purpereum Schumach cv. achara nwankita) indigenous to South-east Nigeria. It will further consider the comparative analysis of the hot-air oven and microwave methods of drying grasses, as well as the physico-chemical properties such as moisture, ash, crude fibre, protein, carbohydrate contents and colour.
The study however, was initiated at the mid of the rainy season of 2018. Hence, the drying experiments of the grasses were carried out at verge of the end of rainy season of 2018. The sensory and shelf life quality test were performed 30 days after completion of the drying operations.
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