novel approaches to expression and detection of oestrus in dairy cows

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have both been associated with embryo survival and fertilisation rate (Khatib et al., 2008a;Khatib et al., 2008b). SNPs in the LH receptor gene have also been reported for their association with days to first service and calving interval (Hastings et al., 2006). However, as yet there is no report of relationships between SNPs and their effects on oestrous expression. Therefore SNPs previously reported both for their involvement in the oestrous cycle and for their effects on fertility were investigated using a candidate gene approach to see if they were linked to activity increases at the time of oestrus. Identifying SNPs encoding for higher levels of oestrous expression would allow the development of breeding programs to improve oestrous detection rates, both cumulatively and permanently. By improving oestrous expression more cows would be detected in oestrus, thus increasing submission rates for AI and at a more optimal time coinciding with ovulation. This would lead to improved conception rates. Therefore, the objective of this work was to identify DNA polymorphisms that would provide a means of identifying those cows that exhibit oestrus more strongly, in order to improve productivity through improved oestrous detection rates. 3.2 MATERIALS AND METHODS 3.2.1 Animals & Phenotypic Data Animals used in this study were 205 Holstein Friesian dairy cows housed at Nottingham University Dairy Centre, as described in Chapter 2. Oestrous detection was measured by activity monitors and activity data analysed, as described in Chapter 2, to determine a measurement of oestrous expression calculated as maximum activity at each oestrus. 3.2.2 Blood Sampling, DNA Extraction and Genotyping Blood samples were collected from the coccygeal vein of each cow under ethically approved Home Office License regulations. Oestrus, insemination and pregnancy, and activity data were known for all animals. Blood samples were then sent off to be extracted and genotyped commercially by KBiosciences Ltd (Herts, UK), using primer extension. DNA was genotyped at 41 loci, in 18 genes as listed in Table 3.1. SNP results were given levels; 0 as the most common genotype within this sample of cows (although these cows may not be a true representation of a general wildtype 68
population owing to previous selection within the herd), 1 as the heterozygote and 2 as the mutant homozygote, for inclusion in analysis. 3.2.3 Gene Selection SNPs were chosen for analysis that had previously been identified on the basis of their involvement in reproductive processes. Genes were chosen for association with i) hypothalamic/ ovarian/ uterine function and ii) a role in central nervous pathways controlling oestrous behaviour and iii) association with production traits such as milk yield, energy balance and feed intake and metabolic influences which can all impact upon fertility and oestrous expression. The genes, positions of SNPs and variations in the DNA, and the previously reported effects on certain traits, are reported in Table 3.1. Many genes could be associated with oestrous behaviour as they encode for or influence key hormones that regulate oestrus. Genes that encode transcription factors and signalling molecules can influence oestrus because they in turn control gene expression of receptors and important molecules. These in turn affect the production and concentrations of oestrus inducing hormones, mainly oestradiol, and related pathways that control behaviour induced by elevated oestradiol. Therefore genes selected for study were those that have been linked to certain observed phenotypes associated with reproduction and could be associated with the expression of oestrus. 69
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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
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calf at 40-50 days post partum; inv
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al., 2006). However, aged sperm hav
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can occur within 2-3 days, but if t
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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 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: CHAPTER 3 - Single Nucleotide Polym
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
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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
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Influence of negative energy balanc
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