novel approaches to expression and detection of oestrus in dairy cows

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Table 2.1 Definitions of cow factors analysed for their effects on the activity increase at oestrus Variable Definition Days in Milk Number of days post partum until each individual oestrus event (DIM) were investigated for the association between DIM and activity at oestrus. Milk Yield at The average milk yield was calculated over each oestrus period Oestrus to investigate the effect of level of production at the time of oestrus on the activity increase. Milk yield at oestrus was calculated as the average of 5 days before, the day of oestrus and 5 days post oestrus. This accounted for daily variation and decrease in yield that is reported at oestrus. Average Daily The total milk yield to each oestrus event was divided by the Milk Yield number of DIM to calculate a representative daily average. This variable was used to assess whether the overall level of daily production within each lactation had an effect on oestrous expression. Cumulative The total milk yield produced per lactation up to each individual Lactation Yield oestrus event was used to assess the effect of overall level of production on activity. Parity Cows were grouped into parity 1, 2 and 3 corresponding to cows in their 1 st parity, 2 nd parity and cows in their 3 rd parity and above. These were analysed for the effect of age and lactation number on oestrous expression. Oestrous Successive oestruses per lactation were analysed for the effect of Number multiple oestrous cycles on the expression of oestrus. The whole data set was analysed with oestrus events per lactation included in statistical analysis as variates, n=930. However this analysis may include poor cows or cows that were later culled for infertility. The average number of oestrous cycles per lactation in the total data set was 3.12, therefore cows that conceived at their 3 rd oestrous cycle were analysed separately for the effect of oestrous number on expression. Further investigation then looked at the difference between the 1 st and 2 nd oestrus event. Time of Year This variable takes into account the time of year in which each oestrus event occurred; 1 - Jan-Mar, 2 – Apr-June, 3 – July-Sept and 4 – Oct-Dec. This was to account for environmental variables such as day length which could physiologically affect the expression of oestrus. Successful Activity increase at oestrus was analysed for its effect on whether Conception successful conception was related to oestrous expression. 54
The interaction between parity and milk yield were then analysed for the combined effect on activity at oestrus using GLMM. The resulting model was: Y ijk = µ + MY i + P j + C k + ε ijk where Y ijk is activity at oestrus, the fixed part of the model consists of µ the overall mean, MY i the effect of milk yield; at oestrus, daily average and cumulative yield, P j the effect of parity C k the random effect of Cow, and ε ijk the residual error. 2.2.3.1 Statistical Analysis of Successful Conception The effect of activity on the probability of conception was analysed using a Binomial model with logit link function. Activity was analysed as part of the fixed model, with cow number included in the random model. Pregnancy (classified as 1 = pregnant and 0 = not pregnant) was analysed as the response variate with insemination (1 = yes inseminated) included as the binomial totals. All inseminated cows were included in analysis. 2.3 RESULTS The results reported in this section are the significant associations between activity and the cow factors discussed in Table 2.1. Maximum activity at oestrus ranged from 26 to 150, averaging 68 activity units. Percentage increase in activity at oestrus ranged from 31 to 200%, averaging 87%. However, the maximum increase in activity at oestrus was not the biggest percentage increase from baseline. This was also the same for the minimum activity increase at oestrus, where this was not the smallest percentage increase from baseline. The correlation between percentage increase from baseline and maximum activity at oestrus was r=0.57, showing a moderate positive correlation. 55
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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
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 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: oestrus was defined as 3 consecutiv
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
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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
Page 191 and 192:
SHERMAN, E. L., NKRUMAH, J. D., MUR
Page 193 and 194:
Influence of negative energy balanc
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