Section 2: Bovine Flashcards
describe the bovine uterus
binornual with a short body
how many caruncles does the normal bovine uterus have?
70-120
how does the uterine tone change in estrus and diestrus?
estrus: turgid
diestrus: more flaccid
do cows have a suburethral diverticulum?
yes
how many annular rings does the bovine cervix have?
4-5
does the bovine cervix tone change appreciably during the estrous cycle?
no
more open during estrus
what does the vagina of the bovine extend between?
from fornix with external os of cervix to vestibule with urethral orifice and suburethral diverticulum
in the bovine uterus, the ____________________ is caudal to the external bifurcation
internal bifurcation
what is the size of bovine ovaries?
1cm in quiescent
5 to 6cm in cows with cysts or large corpus luteum
what are the four palpable characteristics of the corpus luteum?
size
irregular shape
waist
crown
what is puberty defined as in heifers?
first behavioral estrus accompanied by spontaneous ovulation and a normal luteal phase
when do dairy heifers usually reach puberty?
10-12 months
what estrous cycle do cattle have?
non-seasonally polyestrous
what is the normal estrous cycle length in cattle?
18-24 days
average 21 days
what are the four stages of the estrous cycle?
proestrus
estrus
metestrus
diestrus
in which stage of estrous will a cow stand to be ridden?
estrus
when does ovulation occur?
10-15 hours after the end of estrus
what is the metestral “bleed off”?
second or third day post-estrus petechial hemorrhage in endometrium
when do follicular waves occur?
2-3 per estrous cycle
heifers more apt to have 3
continue during pregnancy
what type of placenta do ruminants have?
synepitheliochorial placenta
what produces progesterone throughout pregnancy?
corpus luteum
placenta can maintain pregnancy 150-250 days gestation
at what point can the placenta maintain pregnancy in ovariectomized cows?
150-250 days gestation
when does the fertilized egg or zygote enter the uterus?
3 to 3.5 days after ovulation
what is the average gestation length in cows?
280 days
when does maternal recognition of pregnancy occur in cattle?
16-17 days
what is parturition induced by?
signaling from maturing fetal hypothalamic-hypophyseal-adrenal axis
what is a major sign of impending parturition in cows?
relaxation of the pelvic ligaments
what is stage I of labor?
dilation of cervix
how long does stage I of labor take?
2-6 hours
may approach 24 hours in primigravid heifer
what is stage II of labor?
fetal expulsion
how long does stage II of labor take?
2-4 hours
heifers can go longer
how long is the pituitary insensitive to gonadotropin releasing hormone postpartum?
8-10 days
when will uterine involution be histologically complete?
about 45 days postpartum
what is uterine involution indicative of?
female’s ability to become gravid
what type of penis do bulls have?
fibroelastic penis
has sigmoid flexure
what accessory sex glands do bulls have?
seminal vesicles
prostate
bulbourethral glands
ampulla
when are bulls usually sexually mature?
9-10 months
what is the definition of puberty in bulls?
can intromit and produce an ejaculate containing 50 million spermatozoa with at least 10% progressive motility
what is the volume of average ejaculate of a bull?
5-8 ml
how many spermatozoa are in an average bull’s ejaculate?
5-15 billion spermatozoa
what is indicative of a yearling bull’s sperm output and to some extent its fertility?
scrotal circumference measurements
bulls are attracted to cows displaying ______________________________________________
estral homosexual mounting behavior
what is the breeding weight of holsteins?
750-850 lb at 49-51 inches at the withers
when do most dairies target breeding?
14-15 months
what is the goal of breeding heifers at 14-15 months on dairies?
to have a holstein heifer calve at 1250-1300 lb at 24 months
what are breeding recommendations based on?
weight and height at withers (body frame)
what are the two categories for estrous detection?
observation
heat detection aids
what is the primary sign of estrus?
cow standing to be mounted by other cows
are secondary signs of estrus more or less reliable than primary signs?
less reliable
what is the optimum time period to inseminate cows?
mid-estrus to 6 hours post estrus
what is the process of daughter proven sire for choosing bulls?
a bull sires 40 daughters
milk production records of daughters compared, only those that were good enough kept as AI studs
takes 4-5 years
what is used now to select young bulls?
genomic proven sire
young bulls genotypes through DNA analysis
what is semen from AI bulls evaluated for?
morphology
motility
concentration
volume
what is the goal of cow/calf operators?
45-60-day calving season
when bulls are put into herds, how many cows per bull are there?
25-40 cows per bull
what are some factors that affect cows’ fertility?
nutrition
lactational anestrus
infectious disease
why do beef cows experience lactational anestrus?
suckling inhibition of luteinizing hormone
what are the ovarian structures?
stroma
follicles
corpus hemorrhagicum
corpus luteum
corpora albicantia
what is the first behavioral estrus at puberty preceded by?
increase in the frequency of luteinizing hormone pulses leading to ovulation with resulting short lived rises in progesterone
if there is a corpus luteum present and progesterone levels are high, what happens to the dominant follicle?
undergoes atresia
what does prolonged exposure to progesterone in the luteal phase result in?
down regulation of endometrial progesterone receptors and increases in endometrial estrogen receptors
in what stage does estrogen climb to the peak?
proestrus
what are hormones doing in metestrus?
estrogen drops
progesterone rises
what are hormones doing in diestrus?
progesterone high
estrogen has slight rise with follicular waves
what are hormones doing in estrus?
estrogen declining
luteinizing hormone peak
when does placental attachment occur?
begins 30 days after ovulation
complete by 45 days
what are the connective tissue changes leading up to parturition thought to be due to?
relaxin from bovine corpus luteum
is dystocia more prevalent in dairy or beef cattle?
dairy cattle
what is the rate of dystocia in heifers?
30-60%
why do beef cattle have lactational anaestrus?
suckle stimulus
what has a significant impact on resumption of postpartum cyclicity?
energy balance
how long does it take a bull to ejaculate?
1.3 seconds
how many days is most profitable to have a cow milking and not?
305-335 days milking
40-60 days not
what is the optimum calving interval?
12-13 months depending on milk production
why does the voluntary waiting period exist?
uterine involution takes 30-45 days
breeding at estrus prior to uterine involution results in very poor conception/pregnancy rates
what are some heat detection aids?
pressure mount devices
paint sticks
activity monitors
video camera
how long does fertile semen live after being thawed?
24 hours
what is added to semen before it is frozen?
extender: egg yolk, milk, or soy based
glycerol: protects sperm against freezing damage
when can a cow be diagnosed with pregnancy?
day 28: transrectal ultrasound
day 30: palpation
day 35: chorioallantoic membrane can be palpated
what does the dominant follicle’s increasing estrogen trigger if there is no corpus luteum present?
luteinizing hormone surge
ovulation
for what portion of pregnancy does the corpus luteum produce progesterone?
whole time
placenta can maintain 150-250 days
what is the prevalence of dystocia in mature cows?
2-8%
when can the first ovulation occur after parturition?
20 days postpartum
when does the first ovulation after parturition usually occur in beef cattle?
60 days postpartum
why do beef farmers wait to rebreed their nursing cows until their calves are less dependent on nursing (2-3months)?
lactational anestrus due to suckling inhibition of luteinizing hormone
