novel approaches to expression and detection of oestrus in dairy cows

More documents

Recommendations

Info

on average in Holsteins (Dransfield et al., 1998). The percentage of cows actually standing to be mounted has also declined from 80% to 50% (Dobson et al., 2008). This results in only 50% of cows being observed in oestrus (Van Eerdenburg et al., 2002). Hence detection of oestrus is increasingly more difficult and to improve the decline in fertility oestrous detection rates must be improved. 1.3.1.1 Endocrine, Neural and Genomic Changes Associated with Oestrous Behaviour Oestradiol is the key regulator that synchronizes the endocrinological and behavioural events to drive oestrus; resulting from the action of ovarian steroids on behavioural centres in the brain (Roelofs et al., 2010). The production of oestradiol from the ovary synchronises mating and ovulation; rising above its threshold in an all or nothing response (Allrich, 1994). During follicle development increasing concentrations of oestradiol are produced and secreted mainly from the dominant follicle (Staigmiller et al., 1982). This increases follicular oestradiol 3-4 days before oestrus, causes circulating concentrations of oestradiol to increase (Roelofs et al., 2010), acting at the level of the hypothalamus to trigger a series of programmed neurological events that result in behavioural oestrus (Reames et al., 2010). Other centres in the brain also trigger the closely related LH surge which is required for ovulation and occurs 28-32 hours after oestrus (Walker et al., 1996). In contrast progesterone from the CL also controls oestrus by inhibiting GnRH and LH pulses which reduces oestradiol concentration (Smith and Jennes, 2001). Often in the post partum period there is a silent oestrus which involves ovulation without overt oestrous expression. This is thought to be caused by high oestradiol levels following gestation inducing a refractory period (Allrich, 1994). Oestrus can be affected through the duration of progesterone and progesterone amplitude during the luteal phase which can influence the increase in levels of oestradiol. It is suggested that this occurs by the influence of progesterone on the neural mechanisms controlling release of GnRH, influencing the elements targetted by oestradiol to induce the preovulatory LH surge in the ewe (Skinner et al., 2000). It has also been reported in the ewe that previous progesterone exposure can affect the intensity of oestrous expression (Fabre-Nys and Martin, 1991). However, in the cow these mechanisms differ and oestrus can occur without progesterone exposure. Even with low levels of 16
oestradiol, the LH surge and ovulation can still occur; demonstrating that hypothalamic sensitivity to LH and oestradiol differs and could also differ between individual cows (Reames et al., 2010). Oestradiol is thought to alter neuronal networks, including dendritic connections between cells and receptors, and neurotransmitter release in order to facilitate oestrous expression (Boer et al., 2009). The shift to oestradiol stimulation causes elevated GnRH receptor gene expression in gonadotroph cells which can result in increasing LH pulses stimulated by synthesis and secretion of GnRH (Boer et al., 2009). The increased oestradiol has a self amplifying effect, stimulating the expression of oestrogen receptors in the brain (Pfaff, 2005). Therefore oestradiol indirectly synchronises mating and ovulation. Oestradiol affects certain areas in the brain in order to regulate female sexual behaviour. Specific areas reported to be involved in behavioural oestrus are the arcuate nucleus, ventromedial nucleus, the preoptic area of the hypothalamus and in particular the hippocampus and amygdala are related to behavioural oestrus (Molenda-Figueira et al., 2006). Oestradiol and other hormones, for example IGF-1 and GnRH, can cause up and down regulation of a number of genes in these brain areas known to be involved in oestrous behaviour (reviewed by Boer et al., 2009). Some preliminary work carried out investigating gene expression in the brain at oestrus compared to luteal phase Holstein Friesian heifers has found that oestrous behaviour may be linked to different patterns of gene expression in the pituitary gland, hypothalamus, amygdala and ventral tegmental area (Beerda et al., 2008). The majority of the research into the genomic control of oestrus has been carried out in rodents where increased oestrogen receptor expression in hypothalamic areas at oestrus have been reported (Pfaff et al., 2008) resulting in expression of genes to facilitate oestrous behaviour, stimulating behavioural oestrus and mediating neurotransmission resulting in oestrus (reviewed by Boer et al., 2009). However, parallels can be drawn between the brain areas involved in behavioural oestrus between rodents and ruminants (Stormshak and Bishop, 2008). Increased oestrogen receptor expression has also been linked to an increase in locomotion (Smith and Jennes, 2001), which is a similar oestrus response to that seen in cattle (Kiddy, 1977). 17
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: educes the incidence of problem cow
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
show all

novel approaches to expression and detection of oestrus in dairy cows

Create successful ePaper yourself

Delete template?

Save as template?