novel approaches to expression and detection of oestrus in dairy cows

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treatment, followed by AI 48 hours later. However, pregnancy rates did not differ between Ovsynch and Heatsynch protocols (Pancarci et al., 2002). Progestagens can also be used to synchronise oestrus in cattle by use of internal releasing devices; PRID (progesterone-releasing intravaginal device) and CIDR (controlled-internal drug release) are progesterone releasing devices inserted into the vagina. Other devices are implanted into the ear, such as Norgestomet or are feed additives such as MGA (Melengestrol acetate; Yavas and Walton, 2000). Progesterone supplementation maintains progesterone concentration above 1ng/ml which suppresses oestrus and the LH surge, blocking ovulation (Lucy et al., 2004). Progesterone treatments are particularly useful for treating anoestrus; by decreasing LH initially then increasing LH pulsatility by priming hypothalamic centres to induce oestrus and then ovulation (Yavas and Walton, 2000). Progesterone can also overcome cystic ovaries in cows with a persistent dominant follicle that will not ovulate because of continuous exposure to high frequency LH pulses (Garverick, 1997). Administration of GnRH will can also remove the cystic structure by luteinisation (Garverick, 1997). Progesterone devices were initially used for 14-21 days and upon removal oestrus occurred within 3 days incurring a high oestrus response (Macmillan and Peterson, 1993), although conception rates in cows treated for long periods with progesterone are 10- 15% lower than those using short term protocols such as 7-9 days (Lucy et al., 2004). Here short progesterone treatments are now used with a luteolytic dose of PGF 2α 0-2 days before device removal (Lucy et al., 2004). If PGF 2α is administered before progesterone withdrawal there is a higher degree of synchrony (Macmillan and Peterson, 1993) due to removal of any functioning CL. Overall reproductive efficiency is still reportedly low in animals treated with both PGF 2α analogues and progesterone; calving rate was no different between treated (52%) and control (43%) cows (Roche, 1976). Furthermore, cows bred at a detected oestrus compared to fixed timed AI after prior progesterone synchronisation treatments have similar calving rates (Roche et al., 1977). Oestrous synchronisation has merit for synchronising whole herds in block calving systems, removing the need for oestrous detection as fixed time AI can be used (Lucy et al., 2004) and increasing the intensity and duration of oestrous symptoms as more cows are in oestrous at the same time (Hurnik et al., 1975;Van Vliet and Van Eerdenburg, 1996). Synchronisation also 14
educes the incidence of problem cows not showing oestrus as anoestrus and cystic cows can be induced into oestrus (Lucy et al., 2004). Therefore the advantages are that the submission rate of cows can be increased, and although conception rate is not necessarily higher, pregnancy rates may be increased through better detection of oestrus or removing the need for oestrus (Lucy et al., 2004). The availability of hormones and veterinary treatments can vary widely in cost and between countries due to local legislation and regulations. For example, the use of oestradiol is banned in the EU and US, but actively used in Australia and New Zealand. One major consideration in use of synchronisation to remove the need for oestrous detection is whether the benefits outweigh the cost. Profit from return of increased pregnancy rates and shortening the calving interval must outweigh the cost of hormones, labour and potential veterinary treatments for oestrous synchronisation to be widely used. This questions whether an accurate and efficient method of oestrous detection may be more beneficial over use of hormonal treatments as one major negative aspect of synchronisation is the consumer attitude to use of hormones in food production. Oestrous synchronisation is not a tool to improve fertility; the main benefit is improved oestrous detection because of more consistent results in detection. 1.3 OESTROUS DETECTION 1.3.1 General Overview Oestrus is the period of the oestrous cycle which is accompanied by overt behavioural characteristics caused by changing hormonal profiles, which is the signal for the physiological mechanism of ovulation (Roelofs et al., 2010). It has been reported that part of the reproductive decline is associated with the failure to observe oestrus and failure to interpret the signs of oestrus correctly (Reimers et al., 1985). More recently, Van Eerdenburg et al. (2002) reported oestrous detection rates on farm at less than 50%, but showed they could be up to 100% in cows displaying oestrous behaviour, if monitored continuously. Expression of oestrus is a problem as the intensity of oestrus has declined, averaging only 8.5 standing events per cow, and duration of oestrus (time between first and last sign of behavioural oestrus or episode of standing to be mounted) has shortened from 15 to 5 hours (Dobson et al., 2008), lasting only 7 hours 15
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 and 26: calf at 40-50 days post partum; inv
Page 27 and 28: al., 2006). However, aged sperm hav
Page 29: can occur within 2-3 days, but if t
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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