novel approaches to expression and detection of oestrus in dairy cows

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genetics, therefore using sexed semen to produce a greater number of heifer calves is advantageous for herd development (Olynk and Wolf, 2007). AI also reduces the need to move livestock, improves biosecurity, and eliminates the transmission of disease (Nicholas, 1996). Therefore, AI enhances the dairy industry, but the main challenge in using AI is insemination at the optimal time for conception to occur in order to achieve high conception rates. 1.2.2.2 AI at the Optimum Time for Conception AI must occur relative to the time of ovulation in order to result in successful conception. Standing oestrus is the most accurate symptom of oestrus in relation to ovulation, although the exact timing of onset is rarely known (Dransfield et al., 1998). Oestradiol, the hormone responsible for oestrous behaviour, stimulates the surge in LH which results in ovulation and which usually occurs after the display of oestrus, Figure 1.1. Oestrous behaviour is the overt signal for ovulation, which is the internal, physiological mechanism. Therefore insemination must occur relative to the timing of overt oestrus; important for the viability of the oocyte in the female reproductive tract and fertile lifespan of the spermatozoa (Roelofs et al., 2006). Figure 1.2 shows the window of opportunity for AI at the optimal time for maximising conception post behavioural oestrus, ensuring the likelihood of viable sperm and ova coming together in the female reproductive tract. Ovulation occurs 28-32 hours post oestrus (Walker et al., 1996), whereas the fertile lifespan of the oocyte is only 6-12 hours (Brackett et al., 1980). The viable life of the sperm capable of fertilising the egg in the female reproductive tract is 24-30 hours (Hunter and Wilmut, 1983). Therefore the optimal time to inseminate post oestrus is 4- 12 hours (Dransfield et al., 1998) in order to ensure the sperm reach the oocyte whilst viable and whilst still capable of fertilisation. Spermatozoa require approximately 8 hours in the female reproductive tract to undergo capacitation and become capable of fertilising the oocyte. If insemination occurs to close to ovulation then sperm are not mature enough to fertilise the egg (Hunter and Wilmut, 1983). However, if insemination occurs too early before ovulation then the sperm have to reside in the female reproductive tract for too long which could conversely affect their fertilising ability. Roelofs et al. (2006) reported that early insemination (approximately 36 hours prior to ovulation) does not affect either the number or the fertilization capabilities of the sperm (Roelofs et 10
al., 2006). However, aged sperm have been reported to incur damage to their DNA if they are in the reproductive tract too long. This is reported to affect the oocyte’s development after fertilisation which could result in early pregnancy loss due to impaired embryo development (Ahmadi and Ng, 1999). AI after ovulation can also compromise fertility rates because the oocyte becomes aged, impacting upon fertility and development (Roelofs et al., 2006). Instability in the nuclear and cytoplasmic organelles, disruption of cortical granules and the zona block can increase the chances of polyspermy in an aged oocyte, increased further by late insemination as there are a larger number of active sperm (Hunter and Greve, 1997). A further problem of late insemination is that the reproductive tract conditions alter post ovulation, therefore the environment becomes hostile to sperm compromising the chance of conception (Hunter and Greve, 1997). There are conflicts in reports concerning the optimal time to inseminate post-standing to be mounted (see Figure 1.2). Early studies established the a.m.-p.m. guideline; cows in oestrus during the a.m. should be submitted for AI during the next p.m., and cows in oestrus during the p.m. should be submitted for AI during the next a.m. (Pursley et al., 1998). It has been reported that the pregnancy rates of cows inseminated at the earliest; 0 hours and latest times; 32 hours, post-standing oestrus had significantly lower pregnancy rates per AI. Considerably higher pregnancy rates were achieved in cows bred at 16 hours (middle time period) after the onset of standing oestrus (Pursley et al., 1998). Dransfield et al., 1998, reported similarly, that conception rates were increased 4-12 hours after the onset of standing activity. Therefore, oestrous detection is imperative for the correct timing of AI and getting cows in calf for the efficiency of dairy production. 11
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 and 22: Oestrus growing follicle (Staigmill
Page 23 and 24: ecomes the main inhibitor of FSH an
Page 25: calf at 40-50 days post partum; inv
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
Page 165 and 166:
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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