ABSTRACT
Laying hens require adequate calcium for bone and eggshell formation as well as other physiological functions. Limestone, dicalcium phosphate, oyster shell, bone meal, meat and bone meal are important calcium sources used in formulating diets for laying hens. Of these, limestone is widely used in Kenya because it is readily available and inexpensive. The objectives of this study were: (i) to determine the physical and chemical characteristics of limestone from two sources in Kenya. (ii) to evaluate the effects of limestone source and level of dietary Ca on layer performance and eggshell quality(iii) to determine effect of time of lay on eggshell quality. Limestone was purchased from Athi River (AR) and Ukunda in Kenyan Coast (UKC). Particle size and solubility of the limestones were determined. The specific minerals content was determined according to the AOAC procedures of 2016. One hundred and 144 birds at 25 weeks of age were selected from a layer flock at the Poultry Unit, University of Nairobi and used in this study. The birds were allocated randomly to experimental cages. Six experimental diets, the first three based on UKC and the others on AR limestone were formulated. Each limestone source was included in the diet such that calcium level was 1%, 2% or 4% in a 2X 3 factorial design. A depletion diet containing less than 1% calcium was also formulated. The birds were fed on the experimental diets for a period of 60 days. Each diet was fed to a group of six birds and was replicated four times, giving 24 birds per treatment. Prior to this the birds had been placed on a depletion diet for about 10 days until production of thin shelled eggs was observed. Egg weight (g), hen-day egg production (%), egg breakage (%), feed intake (g/bird/day), feed conversion ratio (kg/dozen), specific gravity (g/cm3), shell weight (g), shell thickness (mm), shell percentage (%) and cost of feed (Kshs/kg or Kshs/dozen eggs) were determined. Data on time of lay was collected on the 1st, 4th and 7th week of lay at 9.00am, 12.00 noon and 3.00pm, respectively. Data analysis was done using GenStat Statistical package and significant treatment means separated using Tukey’s test. Results showed that UKC was superior in calcium concentration (42%) to AR (34%). In vitro solubility was 63.0 % and 29.4% for UKC and AR respectively. The mean hen-day egg production was 76 %, feed intake 118.5g, egg weight 58.03g and feed cost Kshs. 68.49. Limestone source (LS) had no effect (P > 0.05) on these parameters. However, LS had an effect (P < 0.05) on FCR, which was 1.9 and 2.0% in UKC and AR based diets, respectively. It also had an affect (P <0.05) on egg breakage at 5.82 and 11.72 % for UKC and AR, respectively. The effect of Ca level on performance of the layers was evaluated. Feed intake of 124 was higher (P<0.05) by 8-9g when Ca was at 2% than when it was 1 or 4%. Hen-day egg production was 66.8% at 1% Ca and increased (P< 0.05) to 81.9 and 79.1% at 2 and 4% Ca, respectively. FCR improved (P < 0.05) from 1.29 to 1.10 and 1.06 kg per dozen eggs as dietary Ca was increased to 2 and 4%, respectively. At 1% dietary Ca, egg breakage was 17.49%, which declined (P < 0.05) to 5.50 and 3.33% at 2and 4% Ca, respectively. Feed cost per dozen eggs was Kshs 74.58 at 1% Ca and declined to 63.64 and 66.78 at 2 and 4% Ca, respectively. The eggshell quality evaluated indicated that, mean egg specific gravity was 1.06 g/cm3, which was not influenced by LS. The mean shell weight was (4.06g), shell thickness (0.33mm) and shell percentage (8.05%), which were higher for eggs from birds fed UKC limestone by 15.8, 12.9 and 13.8 % than those fed AR limestone. Ca level affected parameters used as eggshell quality indicators. At 1% Ca, the specific gravity of the eggs was 1.03 g/cm3, which increased significantly to 1.07 at 2% Ca. The egg shell weight increased (P < 0.05) from 3.83 to 4.68 and 5.54g as Ca level increased from 1 to 2 and 4 %, respectively. Calcium level (P< 0.05) increased eggshell thickness from 0.28 at 1% Ca to 0.33 and 0.38 mm at 2 and 4% Ca, respectively. There was a significant increase in eggshell percentage from 6.76 to 8.15 and 9.23% as Ca increased from 1 to 2and 4%, respectively. The time of lay had significant (P<0.05) effects on egg weight, shell weight, shell thickness and shell percentage. Eggs laid in early morning weighed 59.24g and had a shell weight of 4.93g, shell thickness 0.36 mm and shell percentage of 8.2. However, eggs laid in the afternoon were lighter by 2.7% and had a lower egg shell weight, egg shell thickness and shell percent by 9.9, 11.1 and 7.2 %, respectively. The conclusions of this study are: (i) UKC limestone had a higher proportion of coarse particles (1-2 mm) and solubility than AR limestone, (ii) the two limestone sources contained trace amounts of Fe, Cr, Cu and Zn, but UKC had a high content of Aluminium (1.07 mg /kg), (iii) limestone source had no effect on feed intake, hen-day egg production, specific gravity and egg weight but had an effect on feed conversion ratio and egg breakage. (iv) layers fed on UKC limestone laid eggs with better eggshell quality in terms shell weight, thickness and percentage than those fed on AR limestone. (v) dietary Ca level affected feed intake, hen day egg production, feed conversion ratio and egg breakage. (vi) Increasing dietary Ca improved eggshell quality characteristics i.e. shell weight, thickness and percentage.
(vii) Eggs laid early in the morning had higher weights than those laid in late afternoon. In addition, they had stronger shells expressed as shell percentage and thickness than those laid in the afternoon.
Recommendation from this study are: (i) where possible UKC limestone should be used in formulating diets in Kenya because of its superior physical characteristics reflected in high egg production and good shell quality in this study. (ii) Further study be done on UKC limestone on layers growth and bone mineral content. (iii) There is also need to investigate the effect of particle size on digestibility of limestone. (iv) effect of midnight feeding on time of lay and eggshell quality.
Key words: Limestone, egg production, eggshell quality, source, dietary calcium
TABLE OF CONTENTS
DECLARATION AND APPROVAL i
ACKNOWLEGEMENTS iii
TABLE OF CONTENTS iv
LIST OF FIGURES viii
LIST OF PLATES ix
LIST OF APPENDICES x
LIST OF ABBREVIATIONS xii
ABSTRACT xiii
CHAPTER ONE
1.0.INTRODUCTION
1.1 BACKGROUND INFORMATION 1
1.2 STATEMENT OF THE PROBLEM 3
1.3 JUSTIFICATION 3
1.4 OBJECTIVES 4
1.4.1 Overall Objective 4
1.4.2 Specific Objectives 4
1.4.3 Null hypotheses 5
1.4.4 Scope and limitation 5
CHAPTER TWO
2. 0 LITERATURE REVIEW
2.1 INTRODUCTION 6
2.2 CALCIUM METABOLISM IN LAYING HENS 6
2.3 CALCIUM SOURCES AND UTILIZATION BY LAYING HENS 9
2.3.1 Calcium sources 9
2.3.2 Calcium requirements 10
2.3.3 Factors affecting calcium utilization and eggshell quality 12
2.3.4 Effect of age on eggshell 15
2.3.5 Effect of ambient temperature on eggshell quality 15
2.4 PHYSICAL AND CHEMICAL CHARACTERISTICS OF LIMESTONE 16
2.5 EFFECT OF TIME OF LAY ON EGGSHELL THICKNESS 18
2.6 CONCLUSIONS 19
CHAPTER THREE
3.0 Physical and chemical characteristics of limestone mined in Kenya Coast (UKC) and Athi river(AR).
3.1 INTRODUCTION 21
3.2 MATERIALS AND METHODS 21
3.2.1 Source of limestone 21
3.2.2 Determination of particle size 22
3.2.3 CHEMICAL ANALYSIS OF LIMESTONE 23
3.2.4 Determination of solubility of limestone samples 24
3.3 : RESULTS AND DISCUSSION 25
3.3.1 Chemical composition 27
3.4 CONCLUSIONS 29
3.5 RECOMMENDATION 29
CHAPTER FOUR
4.0 Effect of source of limestone and level of calcium in the diet on layers performance and eggshell quality in layers
4.1 INTRODUCTION 30
4.2 MATERIALS AND METHODS 31
4.2.1. Chemical analysis of raw materials 31
4.2.2 Experimental diets 31
4.2.3 Experimental birds 32
4.2.4 Experimental design 34
4.2.5 Data collection 34
4.3 DATA ANALYSIS 37
4.4 RESULTS AND DISCUSSION 38
4.4.1 Chemical composition of raw materials and experimental diets 38
4. 4. 3 EGGSHELL QUALITY 50
4.5 CONCLUSIONS 57
CHAPTER FIVE
5.0 Effect of time of lay and limestone source on eggshell quality
5.1 INTRODUCTION 59
5.2 MATERIALS AND METHOD 59
5.2.1 Experimental diets 59
5.2.2 Data collection 60
5.3 RESULTS AND DISCUSSION 61
5.3.1 Egg weight 61
5.3.2 Eggshell weight 64
5.3.3 Shell percentage 65
5.3.4 Shell thickness 66
5.4 CONCLUSION 68
CHAPTER SIX
6.0 GENERAL DISCUSSION, CONCLUSION AND RECOMMENDATION
6.2 GENERAL RECOMMENDATIONS 71
6.3 WAY FORWARD 71
REFERENCES 72
APPENDICES 82
LIST OF TABLES
Table 1: Classification of limestone based on calcium and magnesium levels (%) 10
Table 2: Sources of calcium and their mineral content 11
Table 3: In vitro and in vivo solubility of limestones particles of different sizes 17
Table 4: Methods used for analysis of minerals in limestone 24
Table 5: Particle size of limestone samples from Ukunda (UKC) and Athi River (AR) 26
Table 6: Category of particle size limestone samples 27
Table 7: Concentration of analyzed minerals in UKC and AR limestone 28
Table 8: In vitro solubility and acid insoluble ash (AIA) of UKC and AR limestone 29
Table9:Composition of layer diets used in the experiment 32
Table10: Weight of NaCl dissolved in three litres of water for given specific gravity 36
Table 11: Chemical composition of the main raw materials used in experimental diets 38
Table 12: Chemical composition (% air dry basis) and cost of the depletion and experimental diets 38
Table 13: Effect of dietary calcium source and level on egg production, feed intake, egg breakage, egg weight and feed conversion ratio in laying birds 40
Table14: Effects of calcium source on performance of layer chicken 41
Table 15: Effects of dietary calcium level on performance of layer chicken 41
Table16: Effect of dietary calcium source on specific gravity, shell weight, g, shell thickness and eggshell percentage in layers 51
Table 17: Effect of source of limestone eggshell quality 52
Table 18: Effect of level of calcium in the limestone on eggshell quality 52
Table 19: Chemical composition (% air dry basis) and costs of experimental diets 60
Table 20: Effect of time of lay on eggshell quality 62
Table 21: Effect of limestone source and time of lay on eggshell quality 63
LIST OF FIGURES
Figure 1:Effect of source of limestone and dietary calcium level on feed intake 43
Figure 2: Effects of dietary calcium level on hen-day egg production 44
Figure 3: Calculated calcium intake at set dietary calcium level. 45
Figure 4: Percentage egg breakage for a set dietary calcium level 47
Figure 5: Effect of dietary calcium level on feed conversion ratio 48
Figure 6: Feed cost per dozen eggs 49
Figure 7: Egg weight for a set dietary calcium level 50
Figure 8: Effect of dietary calcium level on shell weight 54
Figure 9: Effect of dietary calcium level on shell thickness 55
Figure 10: Effect of time, source of limestone and dietary calcium level on shell thickness 56
Figure 11: Effect of dietary calcium level on shell percentage with time 57
Figure 12: Effect of source of limestone on eggshell weight 65
Figure 13: Effect of source of limestone on shell percentage 66
Figure 14: Effect of source of limestone on shell thickness. 67
LIST OF PLATES
Plate 1: White (AR) and Brown (UKC) limestone 22
Plate 2: ABN sieves and the collector 23
Plate 3: Cages used in the experiment showing the lower and upper tiers 33
Plate 4: Eggs of different sizes obtained during experiment 35
LIST OF APPENDICES
Appendix 1: ANOVA table showing the effect of calcium level on feed consumed on layers feed with limestone from different sources 82
Appendix 2: ANOVA table showing the effect of calcium level on egg production on layers feed with limestone from different sources. 82
Appendix 3: ANOVA table showing the effect of calcium level on feed conversion ratio on layers feed with limestone from different sources 83
Appendix 4: ANOVA table showing the effect of calcium level on egg weight on layers feed with limestone from different sources 83
Appendix 5: ANOVA table showing the effect of calcium level on specific gravity on layers feed with limestone from different sources 84
Appendix 6: ANOVA table showing the effect of calcium level on shell weight on layers feed with limestone from different sources 84
Appendix 7: ANOVA table showing the effect of calcium level on shell thickness on layers feed with limestone from different sources. 85
Appendix 8: ANOVA table showing the effect of calcium level on shell percentage on layers feed with limestone from different sources 85
Appendix 9: ANOVA table showing the effect of calcium level in layers feed and time lay on egg weight with limestone from different sources 86
Appendix 10: ANOVA table showing the effect of calcium level in layers feed and time lay on eggshell weight with limestone from different sources 87
Appendix 11: ANOVA table showing the effect of calcium level in layers feed and time lay on shell % with limestone from different sources 88
Appendix 12: ANOVA table showing the effect of calcium level in layers feed and time lay on shell thickness with limestone from different sources 89
Appendix 13: ANOVA table showing the effect of calcium level on egg breakage on layers feed with limestone from different sources 90
Appendix 14: ANOVA table showing the effect of calcium level on cost of layers feed with limestone from different sources 90
LIST OF ABBREVIATIONS
ABNT Brazilian Association of Technical Standards
ANOVA Analysis of variance
AOAC Association of Official Analytical Chemists
AR Athi River limestone
UKC Ukunda Kenya Coast limestone
CF Crude fibre
CLS Calcitic limestone
CP Crude protein
DLS Dolomitic limestone
DM Dry matter
DMD Dry matter digestibility
EE Ether extract
FCR Feed conversion ratio
GE Gross Energy
KeBS Kenya Bureau of Standards
LS Limestone source
ME Metabolizable energy
MOLFD Ministry of Livestock and Fisheries Development
Mcal Mega calories
NFE Nitrogen free extracts
NRC National Research Council
CHAPTER ONE
INTRODUCTION
1.1 Background information
Poultry farming is a major contributor in the Kenyan economy. Agriculture contributes 25% of GDP with the 30% being from poultry sector. The industry is important in meeting the ever- growing demand for nutritious food.
The poultry industry in Kenya is characterized by dualism in that large- and small-scale producers are involved in the enterprise (Aila et al., 2012). Poultry farming in Kenya is mostly small-scale, and predominantly for domestic consumption. However, it is fast gaining popularity as a business activity especially in the urban and peri-urban areas. There are 31 million birds in Kenya consisting of indigenous chicken (75%), commercial chicken (22%), breeding stock (1 %) and other types of poultry such as water fowls, turkeys, ostriches and guinea fowls accounting for about 2 % of the total (National Census, 1999; MOLFD, 2012). The chickens are important for production of eggs for consumption, meat as well as fertile eggs for hatching into day old chicks. The key drivers of the growth of the poultry industry in Kenya are: increase in human population, increased per capita income, urbanization and improvement in technology that influence efficiency of production (Gikunju et al., 2018).
The level of production in terms of eggs or meat is affected by several factors such as genotype of the birds, nutrition, diseases and prevailing policies. Nutrition requires provision of those chemical substances or nutrients that will promote growth, ensure good health, improved production of egg and good quality of the food products. Therefore, to achieve the level of production desired, the laying hen must be fed a diet that provides adequate amounts of all nutrients. Adequate intake of calcium is important so as to meet the need for various functions such as formation of the skeleton, as co-factors of enzymes and for the maintenance of osmotic pressure. For the growing bird most of the calcium is used for bone formation. However, as the bird approaches sexual maturity some calcium is stored in the medullary bone for future eggshell formation. For the laying hen, most of the calcium is used for eggshell formation.
In formulating poultry diets a good source of calcium is required. Some of the common sources of calcium are limestone, oyster shell, eggshell, fish meal, bone meal, meat and bone meal and di-calcium phosphate. The use of any of the sources depends on availability and the cost and any risk associated with the raw material. In Kenya, limestone is widely used as a calcium source because of availability and relatively low cost. Different limestones vary in their Calcium contents (Aila et al., 2012) which may be attributed to the locations in which they are mined. Limestone varies in the levels of Calcium and the concentration of other minerals, which can affect its utilization by the laying hen (Chambers et al., 2017).
The producer is interested in producing efficiently a high number of eggs that have shells of good quality. Eggshell quality is of major concern in the industry, since eggs with shell quality that is inferior lead to economic loss to poultry producers. It has been reported that the average number of eggs cracked and lost prior to reaching the point of consumption range from 13% to 20% (Anwar et. al., 2017). Therefore, better understanding of the factors that affect the quality of eggshells in layers is important (Ricke, et al., 2015).
In 2016, 0.287 million metric tons of poultry feed were manufactured in Kenya with a use of 20,664 kg of UKC limestone or 26,117 kg of AR limestone (MoALF annual report 2016). The limestone is mined in three main areas in Kenya, which are the Kenyan coast, Athi River plains and Fort Ternan in Western Kenya. There is no information available on chemical attributes and nutritional value of limestone from various sources.
1.2 Statement of the problem
Limestone is the main source of calcium used in making Animal feeds for the laying hens in Kenya. Approximately 95% of the eggshell is made up of calcium carbonate. The level of dietary Ca affects the eggshell quality that is essential in the egg industry. Eggs with inferior shell quality are a leading cause of economic losses to poultry producers.
It is therefore, important to identify suitable and sustainable sources of limestone, so as to have a better eggshell quality and minimise losses due to breakages. The attributes of limestone obtained from the various sources in Kenya have not been studied. Such attributes include content of calcium, other minerals, solubility and particle size and the effect of feeding this limestone on performance, eggshell quality and time of lay.
1.3 Justification
The rapid growth in poultry production has increased the demand for feed as well as raw materials. This growth is reflected in the increase in the number of eggs produced annually. There is need to improve the efficiency of egg production through reducing losses caused by egg breakage (Sultana et al, 2007), Eggshell thickness, influences the ability of the shell to withstand external pressure and hence resistance to breakage. This leads to the question of how eggshell quality can be improved, especially through diet manipulation. It is therefore, important to identify economically suitable and sustainable source of calcium in order to improve eggshell quality and minimize losses due to breakages. The purpose of this study was to investigate the attributes of two sources of limestone used in feeding poultry in Kenya.
1.4 Objectives
1.4.1 Overall Objective
To determine effects of feeding limestone from two sources on layer performance and eggshell quality.
1.4.2 Specific Objectives
(1) To assess the physical and chemical characteristics of limestone used in layer feeds in Kenya
(2) To evaluate the effects of limestone source and level of dietary Ca on layer performance and eggshell quality
(3) To explore the effect of time of lay on eggshell quality.
1.4.3 Null hypotheses:
• There are no differences in the physical and chemical properties of UKC and AR limestone
• Source of calcium has no effect on layer performance and egg shell quality
• The level of dietary calcium has no effects on layer performance and eggshell quality.
• Time of lay has no effect on eggshell quality.
1.4.4 Scope and limitation
The study was limited to limestone mined in Ukunda in Kenyan Coast (UKC) and that mined at Athi River (AR). A total of 144 laying hens were used. The study encountered challenges in that only a few minerals were analysed because of the limited facilities available. It would have been desirable to determine the digestibility of calcium in the two limestone sources but this was not possible within the time and resources available
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