novel approaches to expression and detection of oestrus in dairy cows

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condition is worsened through selection for angularity and lower subcutaneous fat (Veerkamp and Beerda, 2007). NEBAL can extend for up to 10-12 weeks post partum which can affect the interval to first ovulation (Garnsworthy et al., 2008). Oestrous expression is affected both by the level of NEBAL and body condition of cows. Heat detection rates have been reported to be significantly increased to 84.2% from 58.7% for cows that had a lower BCS loss over the first 100 days of lactation (0.3 vs 0.6 BCS; Mayne et al., 2002). Consistent with this, high yielding cows with more severe NEBAL (9.9MJ/d compared to 2.6MJ/d) showed decreased oestrous expression (Mayne et al., 2002). Significant NEBAL has also been associated with low oestradiol concentrations during the periovulatory period (Mackey et al., 1999) explaining the associated decrease in oestrous expression. Changes in the metabolic status of the cow cause the mobilization of body tissues that affect the levels of hormones involved in fertility. NEBAL attenuates LH pulse frequency which inhibits oestradiol secretion which in turn prevents ovulation. Low energy status coupled with suppressing LH pulses also seems to reduce the responsiveness of the ovary to LH, again inhibiting the production of oestradiol (Butler, 2003) with subsequent impacts upon oestrous expression. Furthermore NEBAL is strongly associated with low levels of blood glucose, insulin and IGF-1 post partum which can limit oestradiol production by the dominant follicle. Metabolic demand causes a reduction in levels of glucose, insulin and IGF-1. Glucose and insulin are associated with the up regulation of LH receptors in the ovary. Indeed insulin and IGF-1 are linked as IGF-1 production is affected by circulating insulin concentrations. IGF-1 levels are also directly related to energy levels are correlate with oestradiol concentrations. This results in an alteration of the sensitivity of the response of the pituitary gland to GnRH, affecting LH pulses, influencing ovarian follicular development and the capability of the follicles to produce oestradiol (Butler, 2003). Therefore factors affecting feed intake and appetite in the periparturient period can affect the linked reproductive and somatotropic axes (Chagas et al., 2007) and thus where possible the amount of body fat and protein mobilization should be minimised to reduce the extent of NEBAL and BC loss (Garnsworthy et al., 2008). In conclusion dietary intake can impact on the concentration of many hormones associated with reproduction. For example levels of nutrition can 30
influence the ability of the ovary to produce oestradiol, thus affecting oestrous expression. 1.4.3.4 Genetic Factors The over focus of genetic selection for greater milk yield with the associated changes in nutrition and management that accompany this has resulted in neglect for other production traits in selection. This has resulted in a significant negative impact on fertility. Cows selected for high milk yield are genetically more susceptible to NEBAL (Boer et al., 2009). Furthermore the reduction in fertility associated with increased milk yield is supported by increasing evidence suggesting that changes in genotype have a significant role in reducing fertility (Chagas et al., 2007). Increased use of Holstein genetics is thought to be the root cause of reduction in reproductive performance because of the over focus on milk yield. However it is possible to maintain production and fertility as demonstrated from evidence in red (Ayrshire) type breeds (Berglund, 2008) and ensuring the appropriate nutritional management (Garnsworthy et al., 2008). BCS is also a result of genetic selection because modern cows are genetically thinner according to Garnsworthy et al., (2008). This is associated with selection for angularity and reduced subcutaneous fat (Veerkamp and Beerda, 2007). In comparing data from 1980-1993 with data from 2000-2006 BCS was shown to decrease from 2.5 to 2.1, respectively (Garnsworthy, 2007). This may therefore predispose the modern dairy cow to lower LH pulses and the associated oestradiol decrease, with reduced oestrous expression as discussed previously. 1.4.4 Herd Factors The intensity and duration of oestrus varies between individual, cows but there are several factors within the herd which can also influence oestrus expression. The degree of calving spread has been shown to affect oestrous expression due to the number of cows in oestrus at any one time (Ball and Peters, 2004). If the calving spread is 365 days it is more likely that fewer cows will be in oestrus together (also depending on herd size). Oestrous expression could be reduced compared with block calving systems, or following oestrous synchronization, in which a group of cows will be in oestrus together (Ball and Peters, 2004). The number of mounts per oestrus can range from 11 per cow, increasing to 36 mounts with 2 31
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: 1.4.3.2 Milk Yield and Nutrition Di
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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