Unit 6 -- Part 5
Ruminant Reproductive Health
J. Nielsen

 

Critical Role of Herd Manager

Accurate and complete record keeping is vitally important to all reproduction programs. (Refer to Additional Resources:  Workable Herd Health Program) Important information to be included in records are:

    • All observations of estrus (heat)
    • Breeding date(s)
    • Veterinary examination(s), pregnancy confirmations
    • Date of birth, number of offspring, any abnormalities such as dystocia, abortion, death, retained placenta, etc.

Good records will allow the herd manager to quickly identify problems such as:

    • increased calving interval
    • increases in number of abortions
    • decreases in conception rate
    • increases in calving mortality

Estrus detection is another very important element in a good reproduction program. The ability to identify animals that are eligible to be bred and to breed them within the window of time established for the particular enterprise is vital.

Good insemination technique includes:

    • Proper timing of insemination
    • Proper handling of semen
    • Quality semen

Performance of Reproductive exams allows the herd manager to:

    • Identify quickly an increase in number of open animals
    • Rebreed or cull open animals

There are a variety of causes of reproductive inefficiency, and again the triad of host, environment and agent should be considered.

  • Host influences
    • Nutritional factors
      a. negative energy balance of dam
      b. overconditioning
    • Stud power
      a. inferior semen quality
      b. lameness/other trauma
      c. too many females/male
    • Genetics -- hermaphrodites, freemartins
    • Dystocia
      a. dam/calf size disparity
    • Retained placenta

  • Environmental influences
    • High heat and humidity
    • Toxins -- lupine pasture (crooked calf )

  • Agent influences -- infectious causes of infertility, may be due to:
    • Systemic infection
    • Nonspecific infections of reproductive tract
    • Bacterial agents that target the reproductive system

1. examples -- Brucella, Coxiella burnetti, Chlamydia psittaci, Listeria monocytogenes, Campylobacter fetus

2. mechanisms of targeting, survival ­ example of Brucella

    • target cells - chorioallentoic trophoblasts
    • specific membrane receptor
    • growth substrate - erythritol

3. Consequences of reproductive tract infection

    • infertility due to either testicular, epididymal or uterine infection
    • fetal death (mummification, abortion, stillbirth) due to either placental or fetal infection
    • inappartent infection of offspring

4. Bacterial agents that target the reproductive tract are often venereal diseases spread through coitus

    • Viral agents causing reproductive disease

1. examples -- BVD, IBR

2. consequences:

      • fetal death with early embryonic loss (resorption) and delayed return to estrus, mummification, abortion
      • congenital infection - BVDV and Bluetongue virus target the central nervous system of fetus and result in arthrogryposis, hydrocephalis, cerebellar hypoplasia (see Unit 1 instructional module illustrations)
      • inapparent persistent infection of offspring (BVDV)

    • Protozoal agents that target the reproductive tract

1. Toxoplasma -- sheep, goats (any species)

      • spread by cat feces
      • animals build up immunity after infection

2. Neospora -- similar to Toxo - seen in cattle, sheep, horse, goat, dog, etc.

      • infects fetal brain and heart
      • dairy cattle in California
      • recurring problem with individual cows
      • dogs recently identified as definative host

Management techniques for Reproductive Health

  • Keep good records!!
  • Test and quarantine new additions, sick +/or aborting animals
  • Do a complete diagnostic work-up when problems arise
  • Establish a good vaccination program for problem agents in your herd/area

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