Food Animal Repro

Dairy vs calf-cow

o For dairies: tighter 12-month calving intervals maximize milk production and ensure cows are bred back soon after calving.

o For beef cow-calf: aim for a compact calving window (spring calving, fall weaning) to produce uniform calf crops and market groups.

Age at first calving

Heifers should calve by ~24 months. Earlier calving (without compromising growth) means more lifetime productivity.

Why are extra days open important?

Costs money! $2-5 per day to feed the animal

Natural cover (bulls)

Used more so in calf-cow operations. The bulls detect estrus, less labor is required.

Risks of natural cover

Variable conception, STI transmission, bull maintenance cost

Heat detection + AI

Required careful observation since standing heat only lasts 12-18hrs. Can use tail paint or activity monitors to improve success

What is the AM-PM rule?

If cow shows heat in the morning, inseminate that evening

Timed AI example

o Example: Ovsynch (GnRH → PGF → GnRH → AI).

o Why it works: synchronizes follicular waves and luteal regression, so ovulation timing is predictable.

Timed AI limitation

Less effective in anestrus cows (no CL to regress)

CIDR synch (progesterone implant + PGF)

o Supplies progesterone, resets ovarian cycle, prevents persistent follicles.

o More reliable than Ovsynch in non-cycling cows.

Rectal palpation pregnancy detection

o Can detect as early as ~30-35 days (amnionic vesicle, membrane slip).

o Risk: very early palpation may increase embryonic loss.

Ultrasound pregnancy detection

o Accurate at 28-32 days.

o Can identify twins, nonviable embryos, and fetal sex (>60 days).

o Why often preferred: early, safe, and provides more information.

Hormone assays pregnancy detection

o Progesterone (d21-24): high = CL present, but not specific for pregnancy.

o PAG tests (BioPryn, DG29): sensitive/specific but can stay positive after abortion/parturition.

Freemartinish

o Female twin to a male; ~90% sterile.

o Why: male hormones + anti-Müllerian hormone from shared placenta suppress female tract development.

Other anomalies leading to incomplete tracts and infertility

unicornuate uterus, hypoplasia, segmental aplasia

Types of anestrus

o Behavioral anestrus: cycling but silent heats (esp. high producers).

o True anestrus: no CL, minimal follicles. Common in underfed heifers or early lactation cows.

Why do cows have anestrus?

energy deficiency suppresses GnRH/LH pulses

What is cystic ovarian disease?

Fluid-filled structure >3 cm or persisting >10-14 days

Follicular cyst

thin-walled, low P4, high estrogen

Luteal cyst

thick-walled, high P4 → anestrus

Why are cysts important?

Prolongs interval to conception, lowers fertility.

Cyst treament

-Transvaginal ultrasound guided cyst ablation

-GnRH then PGF 7-10 days later

-CIDR-synch — most reliable way to treat

Granulosa cell tumor

o Most common ovarian neoplasm.

o May produce steroids → abnormal behavior.

o Treatment: surgical removal → normal fertility if contralateral ovary intact.

Retained fetal membranes

>24 hrs, often immune dysfunction, dysfunction, milk fever, Vit E/Se deficiency,, possibly PGF deficiency

Retained fetal membranes treatment

Takes 8 days for the villous attachments to necrose. Stay out of the uterus, leave the membranes, and monitor rectal temp. If rectal temp >103, begin treatment for metritis with systemic antibiotics

Retained fetal membranes consequences

Expensive, delayed conception, and comorbidities (metritis, ketosis, LDA, pyometra)

Metritis

o <10 DIM, foul discharge, large flaccid uterus, systemic illness possible.

o Treat with systemic antibiotics if febrile/sick (e.g., ceftiofur).

Metritis protocol

watch discharge and temp for first 10 days in milk. If abnormal discharge AND sick/fever = give antibiotics. Can use flunixin only if endotoxic

Endometritis

o >26 DIM, purulent discharge, enlarged cervix, no systemic signs. Cervix > 7.5cm

o Delays conception, ↑ culling.

o Treatment: hormonal (PGF), intrauterine therapies (limited evidence).

Pyometra

o pus-filled uterus + persistent CL, cow is anestrus.

o Why: infection at first ovulation prevents PGF release → CL persists.

o Treatment = PGF to lyse CL, evacuate uterus.

Relationship of uterine diseases

o RFM → metritis → endometritis → pyometra (continuum).

o All reduce fertility, extend days open, ↑ culling risk.

Diagnostic approach to infertility

1. Rule out pregnancy.

2. Evaluate anatomy (congenital issues, adhesions).

3. Assess ovarian function (cycling vs. anestrus, cystic).

4. Review history (nutrition, disease, calving).

5. Consider bull infertility if herd-level problem.

Early embryonic death

<40 days; appears as open. Up to 20% loss is normal

Abortion

40-260 days; ~3-4% pregnancies; 80% infectious

Premature delivery

260 days-term; calf may survive

Stillbirth

full-term but born dead. Often dystocia/asphyxia.

Neonatal death

survive <24 hrs; congenital, dystocia, or infectious.

Venereal transmission abortion

Trichomoniasis and campylobacter venerealis

Trichomoniasis

protozoa from carrier bulls → EED, pyometra, repeat breeders, test and cull bulls. Reportable. Cull positive bulls and test with preputial scraping

Campylobacter venerealis

-Presents very similarly to trich. Prologned estrus cycle/return to heat

-Culture/histopath, vaccinate!

-SS fetus or C jejune causes sporadic abortion in cattle and CAN infect humans

Reportable infectious cause of abortion

Brucella abortus and trichomonas

Brucella abortus

zoonotic, eradicated in most US herds, but persists in wildlife (Yellowstone). Causes 5-7 mo abortions, leathery placenta. Milk ring test, vaccinate calves

BVDV

fetal infection outcomes vary with gestation (EED, PI calves, congenital defects). If suspect, collect ear notch from all calves before the next breeding season!

IBR (herpesvirus)

abortion storms, autolyzed fetuses. Shed in semen. Vaccinate

Lepto

late-term abortion, hemolytic disease, poor conception (esp. L. hardjo in first lactation animal). Vaccinate

Neospora caninum

abortion storms, vertical transmission → lifelong carriers. Diagnose with histopath of fetal brain

Mycotic abortion

thickened placenta, dermatitis on fetus

Diagnostic work up of abortions

• History: stage of gestation, herd vaccination, environment, nutrition.

• Samples: placenta (best tissue), fetus, dam's blood (paired serology), herd-mates' samples.

• Expectations: only ~25-40% of bovine abortions get a definitive diagnosis, even with full work-up.

• Why limited success: tissue often autolyzed, multiple causes possible, and many sporadic toxins/stresses leave no trace.

Puberty

when cow reaches 45% mature body weight

When to breed cow

when she is 55% mature body weight and 90% mature body height

When to calve cow

when she is 85% mature body weight and 95% mature body height

Post partum onset of cyclicity

• Direct correlation to energy balance!!! First ovulation is 15-25 days but can be 50-70 days if she is energy deficient

• It is also LH dependent

• Number of pre-breeding ovulations is directly correlated with subsequent conception rate

Rectal palpation CHART