novel approaches to expression and detection of oestrus in dairy cows

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1.2.1.1 Follicular Phase There are a fixed number of primordial follicles established during foetal development (Webb et al., 2004), which deplete thereafter as many follicles become atretic because follicle growth occurs continuously throughout the cow’s reproductive life (Fortune, 1993). Cattle are monovular therefore as primordial follicles are recruited most become atretic and do not progress through to selection of the single dominant follicle, and few follicles (4mm in diameter, until follicles reach 6-8mm diameter, when one follicle is selected for continued growth and becomes dominant and will either ovulate or undergo atresia (Webb et al., 2003). Follicular development is governed by a period of gonadotrophin independence followed by a period of dependence (Webb et al., 2004). During recruitment, each wave is preceded by increases of FSH secretion lasting 1-2 days, stimulating growth of smaller follicles,
ecomes the main inhibitor of FSH and dependency switches to LH (Ginther et al., 1997). Growth of the dominant follicle continues, and the increase in oestradiol causes increased GnRH pulse frequencies, promoting LH secretion. This in turn stimulates oestradiol production by the granulosa cells (Fortune, 1994). This has a local effect on follicle development, but also a systemic effect, acting upon the hypothalamic-pituitary axis to increase LH production further, by positive feedback (Aerts and Bols, 2010). This ultimately results in oestrus, controlled by oestradiol, and the LH surge resulting in ovulation. 1.2.1.2 Oestrus & Ovulation It is this rise in oestradiol; enhanced by LH, stimulating production of androgen in the theca cells (Garverick et al., 2002) and the subsequent androgens being converted into oestradiol by aromatase enzyme from granulosa cells, which causes oestrus (Fortune, 1994). The positive feedback mechanism between oestradiol and LH, causes LH pulse frequency to increase to about 1 pulse per hour (Roche, 2006). The increase in LH concentration causes a cascade of events that induce the release of the oocyte into the oviduct, by an inflammatory response; involving prostaglandins, particularly prostaglandin E (PGE), produced by the follicle (Aerts and Bols, 2010). Prostaglandins stimulate the proliferation of cells and production of proteolytic enzymes to disrupt the follicle wall, releasing the oocyte (Espey, 1980). This process is ultimately under the control of the follicle itself, timing when it is appropriate to trigger the LH surge for ovulation by production of oestradiol (Roelofs et al., 2010), usually about 10-14 hours after oestrus (Forde et al., 2011). 1.2.1.3 Luteal Phase LH is the key hormone stimulating luteinisation of the theca and granulosa cells post ovulation, forming the CL from the cells of the ruptured cavity (Alila and Hansel, 1984). The CL consists of small and large luteal cells, which have steroidogenic properties (Smith et al., 1994), which secrete progesterone, along with a range of other cell types. The function of the CL is to produce progesterone, in order to maintain pregnancy if a conceptus is present (Forde et al., 2011). Sustained production of progesterone suppresses GnRH pulse frequency and hence LH secretion to prevent ovulation, but does allow enough LH for the continuation of follicular waves and dominant follicle growth (Savio et al., 1990). 7
Page 1 and 2: NOVEL APPROACHES TO EXPRESSION AND
Page 3 and 4: TABLE OF CONTENTS TABLE OF CONTENTS
Page 5 and 6: 2.2.3 Statistical Analyses ........
Page 7 and 8: 5.3 RESULTS .......................
Page 9 and 10: Furthermore, automated software was
Page 11 and 12: LIST OF FIGURES Figure 1.1 Hormonal
Page 13 and 14: LIST OF TABLES Table 1.1 Trends in
Page 15 and 16: LIST OF ABBREVIATIONS ˚ ˚C μM 2D
Page 17 and 18: CHAPTER 1 - Introduction & Literatu
Page 19 and 20: the past 50 years and duration of o
Page 21: Oestrus growing follicle (Staigmill
Page 25 and 26: calf at 40-50 days post partum; inv
Page 27 and 28: al., 2006). However, aged sperm hav
Page 29 and 30: can occur within 2-3 days, but if t
Page 31 and 32: educes the incidence of problem cow
Page 33 and 34: oestradiol, the LH surge and ovulat
Page 35 and 36: The secondary signs of oestrus can
Page 37 and 38: There are also changes in normal be
Page 39 and 40: engage in more natural behaviours i
Page 41 and 42: 1983). Exact explanations and mecha
Page 43 and 44: 2006) and disruption of LH secretio
Page 45 and 46: 1.4.3.2 Milk Yield and Nutrition Di
Page 47 and 48: influence the ability of the ovary
Page 49 and 50: cyclicity can be delayed if dietary
Page 51 and 52: indication for the optimal time to
Page 53 and 54: calving), 3) pre-breeding heat date
Page 55 and 56: 1.5.2 Physiological Changes Physiol
Page 57 and 58: 1.5.2.3 Body and Milk Temperature T
Page 59 and 60: physical activity and stage of the
Page 61 and 62: caused by the general environment t
Page 63 and 64: may be gained. This is because data
Page 65 and 66: In summary the objective was to for
Page 67 and 68: diet, with concentrates at milking.
Page 69 and 70: oestrus was defined as 3 consecutiv
Page 71 and 72: The interaction between parity and
Page 73 and 74:
individual oestrus was not signific
Page 75 and 76:
Table 2.4 The effects of the intera
Page 77 and 78:
(361 vs. 578 points, respectively,
Page 79 and 80:
oestrous expression with increasing
Page 81 and 82:
the blood (Sangsritavong et al., 20
Page 83 and 84:
CHAPTER 3 - Single Nucleotide Polym
Page 85 and 86:
population owing to previous select
Page 87 and 88:
Table 3.1 Cont. Follicle Stimulatin
Page 89 and 90:
3.2.4 Sequencing of DNA in the Labo
Page 91 and 92:
was achieved. PCR products were rem
Page 93 and 94:
3.4 DISCUSSION The objectives of th
Page 95 and 96:
fertility and oestrous expression.
Page 97 and 98:
CHAPTER 4 - Development of a Novel
Page 99 and 100:
In summary UWB seems a good option
Page 101 and 102:
Initial tests were carried out to i
Page 103 and 104:
Therefore this demonstrates that X
Page 105 and 106:
which is most important for achievi
Page 107 and 108:
Figure 4.9 Horizontal - Vertical Di
Page 109 and 110:
that UWB is matching the ‘truth
Page 111 and 112:
mounting cow. For example height ch
Page 113 and 114:
Backpack 1 st put on in AI stalls E
Page 115 and 116:
Cows’ behaviour was assessed at 5
Page 117 and 118:
or that the cows were in an area of
Page 119 and 120:
plane, but mostly in achieving high
Page 121 and 122:
Develop techniques for analysis of
Page 123 and 124:
in elastic silicone moulded over a
Page 125 and 126:
and time of mount, duration of moun
Page 127 and 128:
observed matched with increases in
Page 129 and 130:
5.3 RESULTS Results demonstrate pos
Page 131 and 132:
Figure 5.2 Graph showing mounting b
Page 133 and 134:
Table 5.1 Results from POC 2 showin
Page 135 and 136:
Table 5.3 Efficiency and accuracy o
Page 137 and 138:
oestrus and oestrus it is clear to
Page 139 and 140:
P4 Concentration, ng/ml P4 Concentr
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Activity Activity Activity Activity
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
5.4 DISCUSSION The aim of this work
Page 155 and 156:
averaged 70% which was lower than t
Page 157 and 158:
when the cows lie down, especially
Page 159 and 160:
the level of oestrous activity was
Page 161 and 162:
technology larger herds must be mon
Page 163 and 164:
monitoring could also monitor non-l
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antennae which could affect accurac
Page 167 and 168:
predispose cows to illness e.g. met
Page 169 and 170:
CHAPTER 6 - Overall Discussion & Co
Page 171 and 172:
oestrus, h 2 =0.27 (Lovendahl et al
Page 173 and 174:
The final section of this thesis de
Page 175 and 176:
ate. By using UWB in a commercial s
Page 177 and 178:
provides an insight the potential o
Page 179 and 180:
BLOWEY, R. (2005) Factors associate
Page 181 and 182:
ovine gonadotrophin releasing hormo
Page 183 and 184:
GINTHER, O. J., KOT, K., KULICK, L.
Page 185 and 186:
associated with embryonic survival
Page 187 and 188:
ody condition at parturition on end
Page 189 and 190:
Signs in a 24-h Tie-Stalled Dairy H
Page 191 and 192:
SHERMAN, E. L., NKRUMAH, J. D., MUR
Page 193 and 194:
Influence of negative energy balanc
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novel approaches to expression and detection of oestrus in dairy cows

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