novel approaches to expression and detection of oestrus in dairy cows
novel approaches to expression and detection of oestrus in dairy cows novel approaches to expression and detection of oestrus in dairy cows
1.5.1.1 Behavioural Scoring Van Eerdenburg et al., (1996) developed a scoring system to aid visual detection (Table 1.2). Standing to be mounted was included as the top score that a cow was in oestrus but behavioural scoring also takes into account secondary signs of oestrus (see Section 1.3). Using primary and secondary signs of oestrus allowed all aspects of oestrus to be monitored and the associated scores accumulated a total for oestrous behaviour (Van Vliet and Van Eerdenburg, 1996). When a score of over 100 points was achieved within a 24 hour period the cow was deemed in oestrus. Using this scale and 12 observations for 30 minutes per day in a 6 week study a detection rate of 100% was achieved for all normally cycling cows (Van Eerdenburg et al., 1996). However 12 observations per day is impractical and time consuming. Therefore a more practical method of 3 observations for 30 minutes per day and a threshold of 50 points was developed which achieved 74% detection rate (Van Eerdenburg et al., 1996). Behavioural scoring is a reliable method of visual observation because it includes all behaviour that is associated with oestrus. Yet this method does not give an indication of the onset of oestrus and therefore does not relate to the optimal time for AI. Table 1.2 Table of behavioural scores relating to particular oestrous behaviours. When a total of 100 points is reached within a 24 hour period the cow is judged to be in oestrus (Van Eerdenburg et al., 1996) Oestrus Symptoms Scoring Scale Other Symptoms Mucus vaginal discharge 3 Cajoling 3 Restlessness 5 Sniffing/licking of the ano-genital region 10 Chin resting/ rubbing 15 Mounting Symptoms Mounted by other cow but resisting mount 10 Mounting (or attempting to mount) other cows 35 Mounting head of other cows 45 Standing heat 100 1.5.1.2 Fertility Records Recording all heats is essential for good breeding management and in cases of infertility is the first thing to refer to. Animals must be clearly identifiable by ear tag, freeze mark or other method which should be detectable from a distance when observing. Breeding records should include: 1) animal I.D., 2) calving date (plus information relevant to 36
calving), 3) pre-breeding heat dates, 4) service dates, sire and inseminator, 5) date of pregnancy and 6) expected calving date and any previous problems such as post partum diseases (Diskin and Sreenan, 2000). Records allow improved efficiency allowing farmers to work out the cycles of particular cows calculating approximate dates of oestrus and identifying any cows that have not shown oestrus for further attention, although do not directly aid identification of cows in oestrus. 1.5.1.3 Synchronization To aid oestrous detection and improve submission rates synchronisation protocols (discussed in Section 1.2.2.3) can be used to synchronise the oestrous cycle. Synchronisation allows for a predetermined time period in which cows should display oestrus which aids detection as the herdsmen knows when and which cows to observe (Diskin and Sreenan, 2000). Furthermore some protocols involved fixed timed AI which removes the need for detection of oestrus altogether (Thatcher et al., 1989). Detection is also enhanced by synchronising the oestrous cycles of a group of animals; therefore the intensity of oestrus is increased making detection easier (Hurnik et al., 1975). 1.5.1.4 Teaser Animals A bull among the herd can aid visual detection by detecting subtle signs of oestrus that humans cannot, identifying cows in oestrus. Bulls are often more accurate at detecting oestrus than humans. Vasectomised bulls known as teasers are a useful aid to detecting oestrus as they still allow for controlled breeding (Holmann et al., 1987) and have been reported to marginally improve submission rates, 69% vs 61%, on 5 herds (Gordon, 2006). Androgenised (treated with testosterone or oestradiol) cows or steers, or cows with follicular cysts (with elevated oestradiol production) have increased expression of oestrus (Van Eerdenburg et al., 2002) and can act in the same way as a teaser bull to encourage displays of oestrus and identify cows in oestrus. However use of bulls can incur problems as bulls may develop a preference for certain cows mounting these more frequently and ignoring others. This can complicate detection. Preference may also be given to the SAG ignoring any cows in oestrus outside of this group (Foote, 1975). The presence of a bull can also upset the herd dynamics and decrease female-female mounting. This can make detection of cows in oestrus more difficult as responsibility for oestrous detection is 37
- 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 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: indication for the optimal time to
- 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
calv<strong>in</strong>g), 3) pre-breed<strong>in</strong>g heat dates, 4) service dates, sire <strong>and</strong><br />
<strong>in</strong>sem<strong>in</strong>a<strong>to</strong>r, 5) date <strong>of</strong> pregnancy <strong>and</strong> 6) expected calv<strong>in</strong>g date <strong>and</strong> any<br />
previous problems such as post partum diseases (Disk<strong>in</strong> <strong>and</strong> Sreenan,<br />
2000). Records allow improved efficiency allow<strong>in</strong>g farmers <strong>to</strong> work out the<br />
cycles <strong>of</strong> particular <strong>cows</strong> calculat<strong>in</strong>g approximate dates <strong>of</strong> <strong>oestrus</strong> <strong>and</strong><br />
identify<strong>in</strong>g any <strong>cows</strong> that have not shown <strong>oestrus</strong> for further attention,<br />
although do not directly aid identification <strong>of</strong> <strong>cows</strong> <strong>in</strong> <strong>oestrus</strong>.<br />
1.5.1.3 Synchronization<br />
To aid oestrous <strong>detection</strong> <strong>and</strong> improve submission rates synchronisation<br />
pro<strong>to</strong>cols (discussed <strong>in</strong> Section 1.2.2.3) can be used <strong>to</strong> synchronise the<br />
oestrous cycle. Synchronisation allows for a predeterm<strong>in</strong>ed time period <strong>in</strong><br />
which <strong>cows</strong> should display <strong>oestrus</strong> which aids <strong>detection</strong> as the herdsmen<br />
knows when <strong>and</strong> which <strong>cows</strong> <strong>to</strong> observe (Disk<strong>in</strong> <strong>and</strong> Sreenan, 2000).<br />
Furthermore some pro<strong>to</strong>cols <strong>in</strong>volved fixed timed AI which removes the<br />
need for <strong>detection</strong> <strong>of</strong> <strong>oestrus</strong> al<strong>to</strong>gether (Thatcher et al., 1989). Detection<br />
is also enhanced by synchronis<strong>in</strong>g the oestrous cycles <strong>of</strong> a group <strong>of</strong><br />
animals; therefore the <strong>in</strong>tensity <strong>of</strong> <strong>oestrus</strong> is <strong>in</strong>creased mak<strong>in</strong>g <strong>detection</strong><br />
easier (Hurnik et al., 1975).<br />
1.5.1.4 Teaser Animals<br />
A bull among the herd can aid visual <strong>detection</strong> by detect<strong>in</strong>g subtle signs <strong>of</strong><br />
<strong>oestrus</strong> that humans cannot, identify<strong>in</strong>g <strong>cows</strong> <strong>in</strong> <strong>oestrus</strong>. Bulls are <strong>of</strong>ten<br />
more accurate at detect<strong>in</strong>g <strong>oestrus</strong> than humans. Vasec<strong>to</strong>mised bulls<br />
known as teasers are a useful aid <strong>to</strong> detect<strong>in</strong>g <strong>oestrus</strong> as they still allow for<br />
controlled breed<strong>in</strong>g (Holmann et al., 1987) <strong>and</strong> have been reported <strong>to</strong><br />
marg<strong>in</strong>ally improve submission rates, 69% vs 61%, on 5 herds (Gordon,<br />
2006). Androgenised (treated with tes<strong>to</strong>sterone or oestradiol) <strong>cows</strong> or<br />
steers, or <strong>cows</strong> with follicular cysts (with elevated oestradiol production)<br />
have <strong>in</strong>creased <strong>expression</strong> <strong>of</strong> <strong>oestrus</strong> (Van Eerdenburg et al., 2002) <strong>and</strong><br />
can act <strong>in</strong> the same way as a teaser bull <strong>to</strong> encourage displays <strong>of</strong> <strong>oestrus</strong><br />
<strong>and</strong> identify <strong>cows</strong> <strong>in</strong> <strong>oestrus</strong>. However use <strong>of</strong> bulls can <strong>in</strong>cur problems as<br />
bulls may develop a preference for certa<strong>in</strong> <strong>cows</strong> mount<strong>in</strong>g these more<br />
frequently <strong>and</strong> ignor<strong>in</strong>g others. This can complicate <strong>detection</strong>. Preference<br />
may also be given <strong>to</strong> the SAG ignor<strong>in</strong>g any <strong>cows</strong> <strong>in</strong> <strong>oestrus</strong> outside <strong>of</strong> this<br />
group (Foote, 1975). The presence <strong>of</strong> a bull can also upset the herd<br />
dynamics <strong>and</strong> decrease female-female mount<strong>in</strong>g. This can make <strong>detection</strong><br />
<strong>of</strong> <strong>cows</strong> <strong>in</strong> <strong>oestrus</strong> more difficult as responsibility for oestrous <strong>detection</strong> is<br />
37
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