novel approaches to expression and detection of oestrus in dairy cows

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oestrous expression for a number of reasons including stress (see section 1.4.2.3). 1.4.1.4 Temperature and Season Effects of the environment can influence oestrous expression. Weather, day length, temperature, photoperiod and even lunar cycle have all been reported to have an effect on sexual receptivity and reproductive efficiency; however management systems that eliminate or reduce fluctuations can prevent the effects of seasonality (Orihuela, 2000). When temperatures increase or decrease the oestrous cycle can become disrupted and oestrous expression becomes affected. Heat stress can be caused by hotter temperatures; duration of oestrus reported as 11 hours in hot climatic conditions, compared to 20 hours in cooler climatic conditions in Holsteins (Gangwar et al., 1965), and in summer months Holsteins averaged 4.5 mounts compared to 8.6 mounts in the winter (Nebel et al., 1997). However there are contradictory reports concerning the effects of temperature on oestrous expression. In one study increased number of standing events was reported in hotter months (Peralta et al., 2005). A cause of reduced expression in hotter months can be due to heat stress, affecting the steroidogenic properties of the developing follicle as the components of the reproductive system become susceptible to extreme temperatures (Wolfenson et al., 2000). Heat stress affecting peripheral concentrations of oestradiol at oestrus (Wilson et al., 1998) coupled with changes in hypothalamic-pituitary-stress axes which evoke a stress response can impact upon behavioural oestrus. It has also been suggested that decreased expression of oestrus in colder climates is due to the carry over effects of heat stress into the cooler months (Wolfenson et al., 2000). The introduction of cooling systems, aiding thermoregulatory mechanisms was increased, as farmers are more aware of the effects of heat (Peralta et al., 2005). However, it is important to note that the reproductive effects of heat are less applicable to UK dairy cows compared to countries where there are extreme changes in climate. Seasonal variation can also affect the reproductive capability and influence oestrous expression, as cows were originally seasonal breeders. Return to cyclicity is longer if calving is in the winter compared to the summer (Hansen, 1985). Season of birth and season in which puberty is reached can influence the age at which puberty occurs in heifers (Schillo et al., 24
1983). Exact explanations and mechanisms for these effects are unknown, but it could be due to the influence of oestrogens on LH depending on season. For example, in sheep reproduction can only occur at a certain times of the year due to photoperiod and the effect on reproductive hormones (Legan et al., 1977). Seasonal changes in concentrations of gonadotrophins have also been reported in cattle (Critser et al., 1987), and increases in LH have been reported to be larger in summer compared to winter (Hansen et al., 1982), perhaps due to the inhibitory effects of oestrogens thus affecting oestrous expression. 1.4.2 Health 1.4.2.1 Lameness Lameness is a one of the most important diseases affecting the dairy industry around the world at present. It is estimated to cost the UK dairy industry on average £240 per case due to veterinary and treatment costs, loss of production and major effects on fertility (Kossaibati and Esslemont, 1997). Lame cows are 3.5 times more likely to suffer from delayed cyclicity than healthy herd mates (Garbarino et al., 2004). The difference in frequency of standing to be mounted between lame and sound herd mates was reported as 2.4 vs 8.0 events per oestrus, respectively (Sood and Nanda, 2006). However these workers reported that mounting and other secondary oestrous behaviours were similar between groups. Lame cows were also reported to resist mounting on more occasions and also had a shorter duration of oestrus. Furthermore, duration and intensity of oestrus in lame cows are reduced by approximately 50%. Non ovulating lame cows were reported to have reduced LH pulse frequency and lower (0.53 vs 0.76) pulses per hour compared to healthy herd mates, respectively. Thus it is suggested that the stress of lameness reduces the LH pulsatility which drives oestradiol production, therefore low oestradiol production results in reduced oestrous behaviour (Dobson et al., 2008). Progesterone concentration prior to oestrus was lower in lame cows than in non-lame cows (Walker et al., 2008a) where previous progesterone exposure has been reported to affect the intensity of oestrous expression in ewes (Fabre- Nys and Martin, 1991). 25
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: engage in more natural behaviours i
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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