Livestock Reproduction Flashcards
Initiation of Puberty: Heifers
4 mo - 2 yrs
Sires with larger scrotal size = earlier
Autumn birth earlier than spring
BW: occurs when heifer reaches 40 - 50% of mature weight
Estrus Cycle: Heifers
Non-seasonal breeders
Cycles: 3 weeks duration
Estrus = d0, 12-18h
Metestrus = d1-3, ovulation 24-30h after onset of estrus
Diestrus = d4-18
Proestrus = d19, behavioral estrus begins
Characteristics of Proestrus
Period of rapid follicular growth
Progesterone low
Estrogen increasing
Characteristics of Estrus
Period of sexual receptivity
Stands to be mounted
Clear vaginal mucus (cattle)
Estrogen high
Spike in LH
Characteristics of Metestrus
Short period after estrus
Bloody vaginal mucus (cattle) = too late to breed
Progesterone increasing
Characteristics of Diestrus
Luteal phase
Significant concentrations of progesterone
LH pulsatile decreases
Pulses of prostaglandin secreted by uterus cause regression of CL
How many ovulations per cycle are associated with cattle?
Typically 1
Less 2
Rare 3+
Reproductive Management Goals: Heifers
Heifers should have 1st calf by 2yr of age
Maximize beef heifers to calve early in season
Estrus Detection: Heifers
Standing to be mounted
Secondary: attempting to mount others, mucous vulval discharge, vulval swelling/reddening, bellowing, restlessness, trailing other cows, chin resting
Synchronization: Heifers
Improves pregnancy rates and reduces days open in lactating dairy cows
Initiation of Puberty: Does
6 - 8m
Intro of buck will synchronize group
Breeding should be delayed until 60% adult weight attained
Breeding Season: Does
August - March (Esp. Oct - Dec)
Seasonally polyestrus
Estrus Cycle: Does
Estrus: 12-24h, restless, bleats, wags tails, slight vaginal discharge
Metestrus: refusal to mate until CL formation, no vulvar hemorrhage
Ovulation: spontaneous (12-36h after onset of heat)
Diestrus: CL function, 18d
Proestrus: 1 day duration, buck closely follows but doe will not stand
Estrus Detection: Does
Teaser buck: introduced at beginning of season doe will show heat 5-8d
Buck jar
Side-to-side or up-and-down tail flagging
Speculum exam of cervix (vaginal mucosa reddened at beginning of hear, increases as head progresses, cloudy at end)
Synchronization: Does
Extending luteal phase through progesterone products - intravaginal sponges, controlled internal drug release devices, feed supplementation
Shortening of luteal phase through prostaglandin products