novel approaches to expression and detection of oestrus in dairy cows

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progesterone decrease gave the least precise indication for oestrus and ovulation. Time from luteolysis to oestrus ranged between 24 to 40 hours and from luteolysis to ovulation, 64-136 hours (Starbuck et al., 2006). Furthermore, cows with long follicular phases were reported to have longer intervals from luteolysis to the LH surge, oestrus and ovulation (Starbuck et al., 2006) highlighting the variability of the timing of follicular events when using progesterone concentration for oestrous detection. However progesterone monitoring is an efficient method to monitor the overall cycle of the cow, for pregnancy detection and to determine any ovarian problems (Opsomer et al., 1998). Oestradiol on the other hand correlates more precisely with ovulation (Lopez et al., 2002) but because of the low concentration is harder to detect. Furthermore peak oestradiol concentration at oestrus differs between cows as each has a different physiological threshold (Lopez et al., 2002) therefore difficulties will arise determining a universal threshold to define oestrus. However, sampling and further processing reduces the efficiency of hormone monitoring for the purpose of oestrous detection (Friggens and Chagunda, 2005), although this can be overcome by use of automated biosensors (Delwiche et al., 2001a;Lovendahl and Friggens, 2008). 1.5.2.2 Milk Yield Milk yield has been reported to significantly decrease at the time of oestrus by 2-6% and it is reported that cows housed in free stall barns exhibit an 8.2% decrease on the day of oestrus (reviewed by Firk et al., 2002). It has also been reported that cows presented with an oestrogen challenge to mimic oestrus have a 2kg reduction in milk yield (Britt et al., 1986). The drop in milk yield at oestrus has been explained by the increased restlessness in cows at oestrus and decreased feed intake, and upon resumption of normal behaviour yield has been seen to increase at the following milking post oestrus (Britt et al., 1986). However, yield is an unreliable method for determining oestrus due to the variation between cows and the effects of disease and environmental factors that can cause milk yield to decrease. It has been reported that some do not show a decrease in yield at oestrus and in one herd only 33% of cows showed a significant reduction in milk yield (Schofield et al., 1991). 40
1.5.2.3 Body and Milk Temperature The normal body temperature of a cow is approximately 38.6˚C. This has been reported to decrease a few days prior to oestrus, with minimum temperatures recorded 2 days before, increasing at oestrus by 0.1 to 0.5˚C (reviewed by Firk et al., 2002). Body temperature at oestrus has also been reported to increase by 1.3˚C every 21 days to identify time of oestrus, however this was also reported to fluctuate with changing seasons (Piccione et al., 2003). Measurements of body temperature can be taken via implants inserted into the rectum, vagina or ear of the cow or manually. Temperature measurements are useful although manual measurements would be time consuming and unpractical. However temperature can be affected by environmental conditions, level of physical activity which increases at oestrus and local inflammatory responses (reviewed by Firk et al., 2002).Temperatures of 38.0 to 39.3˚C were recorded from milk in 95% of cows showing oestrus; with a small increase of 0.2˚C for the preceding 3 days, however these results brought about a high incidence of false positives (Mcarthur et al., 1992). Milk temperatures are also still influenced by housing systems and the environment. 1.5.2.4 Vaginal Mucus Resistance An increase in mucus production during oestrus caused by oestradiol secretion (discussed in Section 1.3.3) can be used as a predictor of cows in oestrus. The same hormonal changes also affect the electrical resistance of the reproductive tract (Firk et al., 2002) alongside swelling from tissue hydration which alters resistance (Ezov et al., 1990). It is reported that electrical resistance is highest in the luteal phase and decreases during the follicular phase, lowest coinciding with the onset of oestrus and surge of LH (Leidl and Stolla, 1976). Vaginal resistance is reported to correlate with milk progesterone concentration during the oestrous cycle, r=0.22 (Gartland et al., 1976). There is a high degree of variation in electrical resistance at oestrus between cows (Gartland et al., 1976) which makes this method unreliable for a universal method of detecting oestrus. This variability was confirmed by Rorie et al. (2002) who reported that not all animals have low resistance during oestrus causing difficulty for accurate detection. Generally, low readings between 30 and 40 ohms indicate oestrus and pregnancy rates of 82% have been achieved for 874 cows using resistance below 30 ohms as a detector of oestrus and basis for insemination (Leidl and Stolla, 1976). However, vaginal resistance can be 41
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 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: 1.5.2 Physiological Changes Physiol
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
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Page 151 and 152:
Page 153 and 154:
5.4 DISCUSSION The aim of this work
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averaged 70% which was lower than t
Page 157 and 158:
when the cows lie down, especially
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the level of oestrous activity was
Page 161 and 162:
technology larger herds must be mon
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monitoring could also monitor non-l
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antennae which could affect accurac
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predispose cows to illness e.g. met
Page 169 and 170:
CHAPTER 6 - Overall Discussion & Co
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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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