Hi rwmalin456,
Presuming that the cow is healthy, the very first clue you would have
as to whether a cow is in calf or not is her estrous cycle -
observation is the key to successful animal husbandry. In a normal
cycle, an ovuum (egg) is released every 21 days. Therefore, watch your
cow closely 18 to 23 days after insemination. If she shows signs of
restlessness or bellowing, swelling of the vulva, mucus discharge or
stands to be mounted by other cows, chances are she is in heat again
and is not in calf. If she is the only cow around, you can try
scratching her just at the base of her tail bone - if she is in heat,
she *may* react favourably by lifting her tail up and to the side
(ofcourse she may do that anyway). Other visual cues of pregnancy
don't appear until much later. In time, you will probably be able to
detect movement of the calf, at first with your hand and eventually
you'll be able to see it move. Later still, the udder and vulva will
swell and a mucous discharge will appear.
That said, the best way to determine if a cow is in calf is to ask a
large-animal veterinarian to stop by and perform an examination. The
quickest and easiest method to confirm pregnancy is by ultrasound. An
ultrasound of the uterus can be performed as early as 25 days to
determine pregnancy. At thirty to thirty-five days, palpatation by
rectal exam can be performed, however, it is best to wait forty-five
days for better accuracy and to reduce the chances of abortion.
Determining Pregnancy in Cattle: Palpating to Determine Pregnancy:
"The following is a description of pregnancy determination. This
determination, called palpation, is made by inserting the arm into the
rectum and feeling the reproductive tract for pregnancy indications."
http://animalscience.tamu.edu/ansc/publications/beefpubs/B1077-pregnancydeterm.pdf
Pregnancy:
- average gestation 280 days
- veterinarian can diagnose pregnancy 35 days after breeding by a
rectal examination, but it is recommended that examination not occur
until 45 days to reduce the hazard of induced abortion
- in 60 days the fetus can be felt by the veterinarian
- rate of growth accelerates throughout gestation, greatest increase
in size during the last third of pregnancy
- udder enlarges
- vulva becomes enlarged
- mucus discharged from the vulva may appear weeks before calving
http://www.scottishhighlandcattle.com/repro.htm
Determining Pregnancy in Cattle:
http://www.ca.uky.edu/agc/pubs/asc/asc61/asc61.htm
Pregnancy Scanning - Cattle:
"Ultrasound scanning in cattle is a safe quick and simple way of
confirming pregnancy from as early as 25 days gestation, right through
to full term."
http://www.animalscan.freeserve.co.uk/scan2.htm
The Reproductive Function of Dairy Cattle:
"The heat cycle is the interval (21 days average length) between two
heats (Figure 2). A heat, or estrus, lasts six to 30 hours and is the
period of sexual receptivity (Day 1 of a cycle)."
http://babcock.cals.wisc.edu/de/html/ch8/reproduction_eng_ch8.html
Estrus:
"Estrus is described as the time of increased sexual and activity and
receptivity. Primary behavioral signs include standing when mounted by
other cows, mounting other cows, vulvar swelling, restlessness, clear
vaginal mucus discharge, and bellowing. In cows this rhythmically
occurs on average every 21 days. Estrus lasts approximately 18 hours
with ovulation occurring around 12 hours after the end of standing
estrus."
http://edis.ifas.ufl.edu/BODY_DS115
Additional Links:
Cattle Today Gestation Table / Calving Date Calculator:
http://www.cattletoday.com/gestation.shtml
A Field Guide to Cows:
http://www.amazon.com/exec/obidos/tg/detail/-/0140273883/ref=ase_crazyforlife/102-4373028-3818525?v=glance&s=books
I hope I've been able help but if you have any questions, please post
a clarification request before closing/rating my answer.
Thank you to blazius-ga for help with this question - I hope I can
reciprocate before too long.
Happy New Year!
hummer
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