novel approaches to expression and detection of oestrus in dairy cows

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2.4 DISCUSSION The objective of this study was to identify factors associated with the activity increase at oestrus. Activity increases at the time of oestrus between 2 and 4 fold (Kiddy, 1977). In this study the increases in activity were reported expressed as maximum activity at oestrus and the percentage increase in activity from baseline. There was a moderate positive correlation between percentage increase and maximum activity. This could be explained because some cows may have a high average baseline activity but a small maximum activity and thus their oestrous expression is decreased, or vice versa where cows are generally inactive yet at oestrus become very active. Several cow factors were found to have a significant effect on maximum activity at oestrus; parity, oestrous number, time of year and milk yield (P
(361 vs. 578 points, respectively, from the table of behavioural scores, determined by the authors’ scoring system), with multiparous cows displaying more intense oestrus (Van Eerdenburg et al., 1996). In another study oestrus activity was lower in heifers, 5.5 mounts per hour, increasing to 7.9 mounts per hour for cows in the 4 th lactation or above (Gwazdauskas et al., 1983), indicating increased expression with increasing lactation number. This could be due to conditioning and sexual experience, but when heifers were removed from the analysis the results became insignificant and there was less of a pattern (Gwazdauskas et al., 1983). In the current study it was possible that the reduction in activity, with increasing parity, was influenced by differences in milk yield. However when analysing the effect of both milk yield and parity (Table 2.4) on activity the interaction was not significant. It could be explained however that cows in later lactations have greater milk yields per lactation, with maximum yield around the 4 th lactation (Garnsworthy et al., 2008). Higher milk yields could negatively influence oestrous expression (Lopez et al., 2004). Changes in energy balance with each successive lactation (Coffey et al., 2002) and altering metabolic profiles between 1 st lactation cows and older (Wathes et al., 2007a), can affect oestrus expression through metabolite effects on hormones controlling the oestrous cycle. Cows in their first lactation use nutritional ingredients for growth as well as for lactation and reproduction i.e. for conception and for pregnancy (Sheldon et al., 2006). This may result in a proportionately more severe NEBAL and hence cows have difficultly recovering (Meikle et al., 2004). This may continue and affect expression of oestrus in subsequent lactations; therefore activity may also be decreased in later lactations. Furthermore because cows in later lactations are more likely to produce greater milk yields (Garnsworthy et al., 2008) they may suffer increased NEBAL (Macmillan et al., 1996). The extent of the effect of lactation on fertility, and oestrus, is more severe in cows fed on concentrates and conserved forages (>20%) compared to cows fed at pasture (
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NOVEL APPROACHES TO EXPRESSION AND
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TABLE OF CONTENTS TABLE OF CONTENTS
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2.2.3 Statistical Analyses ........
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5.3 RESULTS .......................
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Furthermore, automated software was
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LIST OF FIGURES Figure 1.1 Hormonal
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LIST OF TABLES Table 1.1 Trends in
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LIST OF ABBREVIATIONS ˚ ˚C μM 2D
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CHAPTER 1 - Introduction & Literatu
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the past 50 years and duration of o
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Oestrus growing follicle (Staigmill
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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 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: Table 2.4 The effects of the intera
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
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observed matched with increases in
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5.3 RESULTS Results demonstrate pos
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Figure 5.2 Graph showing mounting b
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Table 5.1 Results from POC 2 showin
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Table 5.3 Efficiency and accuracy o
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oestrus and oestrus it is clear to
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P4 Concentration, ng/ml P4 Concentr
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Activity Activity Activity Activity
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5.4 DISCUSSION The aim of this work
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averaged 70% which was lower than t
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when the cows lie down, especially
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the level of oestrous activity was
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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
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CHAPTER 6 - Overall Discussion & Co
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oestrus, h 2 =0.27 (Lovendahl et al
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The final section of this thesis de
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ate. By using UWB in a commercial s
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provides an insight the potential o
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BLOWEY, R. (2005) Factors associate
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ovine gonadotrophin releasing hormo
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GINTHER, O. J., KOT, K., KULICK, L.
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associated with embryonic survival
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ody condition at parturition on end
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Signs in a 24-h Tie-Stalled Dairy H
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SHERMAN, E. L., NKRUMAH, J. D., MUR
Page 193 and 194:
Influence of negative energy balanc
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