Bovine Therio part 1 Flashcards
Dairy cattle
Heifers should have calves @ 2
Lactating cows should have a predetermined, economically calving interval optimized for milk production and replacement rate
Beef cattle
Heifers should have calves @ 2
One calf per year
70% calvings from first cycle of breeding season
Relationship between sire and daughter’s reproductive function
Sire scrotal size correlates positively with age @ puberty of daughter
Environmental major determinants
Nutrition, health, proximity to bulls, season of birth
How does nutrition affect puberty?
Leptin, IGF-1 and somatotropin
Kisspeptin signaling in hypothalamus impt. role in generating GnRH pulses
Important condition that should be satisfied to have the best reproductive performance?
heifer development to reach 65% of mature height and weight @ breeding age 14-15 mon
Major problems if heifers too small or too young to get pregnant
Dystocia and first calving @ 22-24 months of age
Estrous cycle
Duration: 18-24 days
Follicular: 4-6 days
Luteal: 14-18 days
Follicular phase
2 waves (3 sometimes)
Gonadotrophin dependent follicles
Phases: emergence, selection, dominance, ovulation/ atresia
Recruitment/emergence under follicular phase
5-20 follicules
Transient ↑ in FSH
Selection under follicular phase
↑ in estradiol and inhibin
Suppression of FSH
↑ responsiveness to LH
Dominance under follicular phase
Most follicles underwent atresia
Large follicles receptive to LH
Ovulation
1 follicle emerged and has the ability to ovulate if no progesterone present
Regression (atresia) in presence of progesterone
Insufficient frequency of LH to cause final maturation and ovulation
Factors that affect the length of estrus in cattle
PGF2a treatment (short cycling)
Ovulation synchronization and timed AI
PGF2a admin in the luteal phase
Injection of PGF2a or analog (cloprostenol) causes regression of CL and estrus in 2-5 days
PGF2a admin during recruiting phase
Estrus starts 5 days after injection
PGF2a admin with follicle already selected
Estrus starts 3-4 days after injection
Clinical aspects of estrus
Dominant follicle
High estrogen (estrodiol)
Max tone of the uterus
LH surge: maturation and ovulation
Estrus behavior
Cow standing to be mounted**
Mucous, discharge, reddening and swelling of the vulva, ↑ activity, chine resting, lip curling, drop in milk production
Length of estrus
15-18 hours
Most important limiting factor to reproductive efficiency in dairy cattle
Heat detection
Corpus luteum development and function
Luterinization of the theca and granulosa cells
Production of progesterone
Alteration of gene expression in the uterus
Immediately after ovulation
Dominant follicle replaced by an ovulation depression (OVD)
Uterus has some tone or edematous
Vaginal discharge may be bloody
Early diestrus
Metestrus
Corpus hemorrhagicum (CH)- soft structure
Uterine edema
Diestrus (day 5-16)
CL cavitary or non-cavitary: crown and demarcation line with ovarian stroma (fully functional)
Uterus relaxed
High progesterone
End of diestrus (luteolysis)
Lack of interferon tau (maternal recognition of pregnancy)
Role of PGF2a and oxytocin in propagating episodic secretion of PGF2a from the uterus
Genital examination of the cow
Inspect cows for abnormal demeanor, signs of lameness, mastitis, abnormal manure, vaginal discharge
Body condition
Normal uterus
Estrus: toned
Just after ovulation: edematous
Diestrus: relaxed
Uterus abnormalities
Rudimentary intersex/ free martin
Flaccid (anestrus)
Content: pyometra
Adhesions, masses, etc.
