novel approaches to expression and detection of oestrus in dairy cows

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adipose tissue to centres in the brain to regulate feed intake, energy balance and metabolism during milk production (Chagas et al., 2007). Circulating concentrations of metabolites and hormones associated with these processes are controlled by the balance between milk production levels, nutrient intake and body tissue reserves. This is also affected by the genetic potential of the animal (Garnsworthy et al., 2008). Therefore milk yield, nutrition and genetics are all interlinked and can influence oestrous expression. 1.4.3.1 High Milk Yield Milk production has been increasing since the 1950s to the present, with a more dramatic increase in recent years (Lucy, 2001). There has been a simultaneous decrease in reproductive parameters and a marked association with the decreased duration of oestrus (Lopez et al., 2004), which still persists. Milk production in the UK has increased from 7375 litres per cow in 2010/11 and now stands at 7617 litres for 2011/12 (provisional data for 2012; DairyCo, 2012a). This has been associated with low oestrous detection in the UK which has declined to only 50% (DairyCo, 2009). Oestrous expression has been reported to decrease with increased milk production; Lopez et al., (2004) reported that a significant number of low producers had more periods of high intensity and longer duration of oestrus than high producers. Significantly more high producers also had oestrus events of shorter duration and lower intensity compared to low yielding cows. The duration of oestrus was reported to be longer in low yielders than high yielders (10.9 vs 6.2 hours), total number of standing events increased (8.8 vs 6.3) and total standing time increased (28.2 vs 21.7 seconds; Lopez et al., 2004). Lactation yield over 305 days has been confirmed to influence oestrous expression. High yielders producing 10814kg compared to average yielders producing 6912kg showed decreased expression of oestrus and a higher incidence of silent heats (Harrison et al., 1990). At first ovulation post partum none of the high yielding group displayed overt oestrus compared to 50% of average yielding cows. At the second ovulation post partum 50% of the high yielding group displayed oestrus compared to 100% of the average yielding group (Harrison et al., 1990). 28
1.4.3.2 Milk Yield and Nutrition Dietary improvements to cope with high levels of milk production can result in changes in the pattern of energy metabolism (Gutierrez et al., 2006), which can alter endocrine signalling (Roche, 2006), therefore can affect expression of oestrus. High milk production requires a high plane of nutrition as there is a close correlation, r=0.88, between milk production and dry matter intake (Harrison et al., 1990). Hence lactating cows require higher energy from concentrates to meet the requirements for high milk production (Lopez et al., 2004). This causes an increase in liver blood flow and results in rapid metabolic clearance of steroids, progesterone and oestradiol, by the liver from the blood stream (Sangsritavong et al., 2002). This can result in shorter duration of oestrus due to lower oestradiol concentrations in the circulation (Sangsritavong et al., 2002). Particularly as oestradiol concentrations on the day of oestrus are significantly correlated with duration (r=0.57; Lopez et al., 2004). Therefore metabolic clearance of steroids provides a possible mechanism for the effect of high yield reducing the expression of oestrus; high yielders displaying shorter and less intense oestruses (Lopez et al., 2004). 1.4.3.3 NEBAL and BCS Nutrition can also affect oestrous expression through its effect on the length of NEBAL at the early stage of lactation. Energy balance is the balance between energy intake and output for maintenance and milk production. However additional pressures during late gestation and early lactation for foetal growth and milk synthesis can also put strain on the energy requirements (Wathes et al., 2007b). As output (milk yield) exceeds intake the cow can’t meet the energy it requires just through feed intake. Body fat and protein are mobilized from the cow’s reserves for production, shifting nutritional requirements and altering metabolic status and energy partitioning (Garnsworthy, 2007). This induces a period of NEBAL, which is often unavoidable and can cause weight loss (up to 50- 75kg in weight; Roche, 2006), combined with a loss of body condition (Garnsworthy et al., 2008). However because of selection for higher milk production and an increased ability to mobilize fat and muscle to support production, NEBAL is exacerbated and loss of body condition is more prevalent and prolonged in high producers. Many factors can affect the extent of NEBAL including genetic merit for milk production where the 29
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: 2006) and disruption of LH secretio
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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