Veterinary control of fertility in cattle Flashcards
History for individual infertile cow or heifer
Age and parity
Time since calving
History of dystocia, retained foetal membranes, or other puerperal problems
Previous heats or services
whether the animal is running with the bull
Results of previous examination or treatments
What should the vagina be assessed for?
Abnormalities, such as scar tissue or tears and an assessment can be made of vaginal tone, and whether pneumovagina is present
What sould the cervix be examined for?
lesions and to check its patency
How often shoud a farm have a routine fertility visit?
at least twice a year
What is the calving interval?
the interval in days for an individual cow between one calving and the next
What is the calving index?
the average (usually the mean) of the calving intervals of all cows within a herd at any given time
What is the calving to conception interval?
the average (usually the mean) of the calving intervals of all cows within a herd at any given time
an up-to-date and more relevant version of the calving index
Meaning of days open
The interval in days from calving to conception of cows that conceive, and from calving to culling or death of cows that do not conceive is described as days open
Calving to first service interval
The interval from calving to when a cow receives her first service
Non-return rate
a crude estimation of pregnancy rate (and often called the assumed pregnancy rate), and is useful if no pregnancy diagnosis is performed
measured as a percentage of cows that have been inseminated and have not been presented for a repeat insemination within a specific period of time (usually 30 to 60 days)
often more than 20% higher than the actual conception rate
Conception rate
The number of services given to a group of cows, over a given period of time which results in a diagnosed pregnancy.
(The reciprocal of this is often used and described as the number of services per conception).
What two measurements give an indication of oestrus detection accuracy?
the first service submission rate
the distribution of Inter-oestrus Intervals (period between services)
First service submission rate
measured as the percentage of cows that receive a first service in the 24-day period (the upper end of a normal oestrus cycle) following the voluntary waiting period (The 24-day Submission Rate)
gives an indication of the heat detection accuracy in the first part of the service period
The distribution of inter-oestrus intervals
indicator of heat detection accuracy in the subsequent service period
expressed as the percentage of normal oestrus interval at 16 to 24 days and 36 to 48 days, and may be presented as Percentage Normal Oestrus Cycles.
Oestrus detection rate
21 divided by the mean interservice interval
Target: >70%
Oestrus detection efficiency
Warren equation; (B+D)/(A+B+C+2[D+E])x100*
Target: >50%
First service submission rate
Number of eligible cows served within 21 or 24 days of the end of the voluntary waiting period divided by the number of eligible cows
Target: >70%
Mean or median calving to first service interval
Mean or median days from calving to first service interval for all cows served
Target: 65 to 75 days
Preganancy diagnosis-positive rate
Number of cows with positive pregnancy diagnosis divided by the total number of cows presented for pregnancy diagnosis
Target: >70 (if scanning after 30 days) to >85%‡ (if manual diagnoses after 42days)
Reproductive efficiency
Also known as the fertility factor
A derived factor calculated by multiplying the preganancy rate by the oestrus detection rate
Culling for failure to conceive
cows that are culled are excluded from some calculations and so cows that are slow to get in calf may be culled before they can affect these figures (namely the calving index and calving to conception intervals) and the fertility may appear better than it actually is.
Routine visit findings
Retained foetal membranes >10%
Metritis >10%
Vulval discharge at 21 to 35 days >20%
Cystsic ovarian disease >10%
Anovulatory anoestrus >5%
PD positive <80%
Target calving index
365-370 days
Target calving to first service interval
65 days
Target calving to conception interval
85 days
Target pregnancy rate to first insemination
60%
Target pregnancy rate to all inseminations
55%
Target abortion rates
<2%
Target culling for failure to concieve rate
<7%
Factors involved in calving to first service interval
Uterine involution and resumption of ovarian activity
Voluntary waiting period
Oestrus detection efficiency
Oestrus detection accuracy analysis
Oestrus detection accuracy can be determined using milk progesterone assays by taking milk samples of at least the next 10 services and calculating the number served in the luteal phase
Oestrus detection efficiency analysis
assessed by looking at inter-oestrus intervals- should fall between 18 to 24 days and 36 to 48 days
Why could an inter-oestrus interval occur under 17 days?
Gnereally a measure of poor oestrus identification, or due to cows showing nymphomaniac behaviour (cystic ovaries)
What could cause an inter-oestrus period of between 25-35 days?
may be due to poor oestrus identification, late embryo death and may also occur if early PDs (less than 42 days) are performed together with use of luteolytic agents (PGF2α) for those that are not in-calf
What could cause an inter-oestrus period of more than 49 days?
difficult to interpret but may be related to poor oestrus detection and ovarian activity ceasing after initial resumption
Q-sum
The cumulative sum - used for generating first service, subsequent, and overall pregnancy rates
Target BCS at calving
3-3.5
Target BCS prior to first service
2-2.5
Target BCS in mid-lactation
2.5-3
Target BCS at drying off
3-3.5
Which metabolites are commonly measured to test nutrition?
BHB
Glucose
Non-esterified fatty acids (NEFA)
Urea nitrogen (UreaN)
Albumin
Globulins
Also magnesium, phosphorus, calcium, copper, GSHPx (selenium), and thyroxine (T4)
β-Hydroxybutyrate (BHB)
A ketone body, its concentration is increased when animals are under increasing energy stress
Glucose
Not as sensitive to changes in energy balance as BHB. In some circumstances it may be only metabolite to change
Non-esterified fatty acids (NEFA)
A direct measure of fat mobilisation. This is a more useful measure in dry cows.
Urea nitrogen (UreaN)
Reflects current daily protein intake and protein metabolism.
Albumin
Protein synthesised by the liver. Measure of long term protein status.
Globulins
Antibodies of type associated with chronic inflammation.
