Producer question: My herd's reproductive performance is waning. No disease issues are evident. Where else should I look?

Thacker's response: Although great strides have been made in diagnosing infectious reproductive problems, cases continue to go undiagnosed. Some reasons why include:

  • The belief that only infectious agents cause reproductive failure. The most important diagnostic activity in many situations is watching herd personnel do their jobs.
  • The failure to recognize that, regardless of the facilities and labor situation, if the biological requirements such as animal comfort, sow condition, sanitation and floor moisture are not met, fertility will be poor.
  • Noninfectious causes of infertility should be suspected if: the problem is long term; overt reproductive failure such as abortions, mummies and stillbirths are not prominent; if no overt disease is apparent in other age pigs.

Infectious infertility refers to specific reproductive pathogens like parvovirus, porcine reproductive and respiratory syndrome, psuedorabies, leptospirosis and others. I consider contamination of the reproductive tract by environmental organisms as noninfectious infertility because the control methods tend to be management based.

Step 1: Production Record Analysis

Records will define the outcome and provide clues to the problems. I prefer to categorize problems using the following scheme:

Low number of pigs weaned per litter:

a. Low total number of pigs born – gilts vs. sows vs. both.

b. High piglet losses – mummified fetuses, stillbirth, pre-weaning mortality.

Low farrowing rate:

a. Low conception rate – less than 28 days of pregnancy.

b. High fallout rate – abortions, NIP, sow mortality.

Delayed onset of estrus: Gilts (puberty) vs. sows (after weaning).

High non-productive days: Number of intervals X interval length.

The next step is to analyze records in more detail to further characterize deficiencies. It's important to identify parameters that will provide clues about worker performance. The following parameters can be used for this:

Wean-to-estrus intervals:

a. Prolonged – parity, estrus stimulation, heat detection, lactation feed intake, season.

b. Too short – often not recognized or appreciated.

Services per week: (look at the average and variation)

a. Influence on total output – average value.

b. Detrimental to pig flow management: wide weekly variation.

Matings per service: (depends on the plan)

a. High percentage of single matings with artificial insemination programs.

b. High percentage of triple matings if sows are mated once a day.

Repeat estrus intervals: High percentage greater than 24 days – inconsistent or inaccurate post-breeding heat and pregnancy diagnosis, rough handling during moving.

Late pregnancy fallouts:

a. Poor inventory management and unobserved abortions.

b. Pseudo pregnancy – early pregnancy management, mycotoxins.

Low total born:

a. Gilts – number of heats prior to service.

b. Sows – genetics, lactation length, lactation feed intake.

High death loss:

a. Stillbirth – parity, observed farrowings, carbon monoxide.

b. Pre-weaning mortality – induced farrowings, birth weights.
This is not an exhaustive list. It does, however, present common or relatively new causes. Without accurate records, it is nearly impossible to accurately diagnose noninfectious reproductive failure.

Step 2: Interview Personnel

The goal is to get a perspective of the management plan, including pig flow, animal introductions, mating strategy, timing of weekly and daily tasks.

Detailed records usually answer these questions, so in some respects the interview is a test of how well the personnel know the herd. Discover attitudinal clues that provide potential reasons for the problem. For example, you might hear: "If weaned sows are not in strong heat by six days after weaning, we mate them anyway just to be on the safe side."

Characterize production inputs including:

a. Genetics – The breeds and level of heterosis will have a major impact on total born, as well as disease status and durability.

b. Nutrition – Feeding levels throughout the reproductive cycle. Common problems include:

Not enough feed in early gestation (especially in late summer and early autumn, which results in abortion and pregnancy loss.)

Over feeding in mid-gestation, resulting in over-conditioned sows and reduced feed intake in lactation.

Not increasing feed in late gestation, resulting in low birth weights and low pig viability.

Poor lactation feed intake due to feeding program.

c. Facilities – Capacity of farrowing and breeding-gestation facilities.

d. Disease – Biosecurity, historical presence of diseases and disease problems.

Step 3: General Herd Observation

The herd "walk through" is an important practice and should address the following:

Animal factors, such as sow condition, sow health (lameness, shoulder ulcers) and vulvar discharges.

Environmental factors, such as air temperature, floor temperature, moisture and sanitation, and light intensity – especially in the weaned-sow area.

Management factors, such as feeder sanitation, sow cards, equipment storage and semen storage temperature.

Step 4: Watch Reproductive Procedures

This is often the most revealing activity, but workers may not function normally because they are being watched. Procedures to
observe include:

Heat stimulation of gilts and sows to induce puberty and after weaning. Focus on boar exposure, length of time, frequency and boar aggressiveness.

Heat detection of gilts and weaned sows. (Same factors as above, plus relationship to mating strategy. Is heat detection done at mating, or is heat detected first and matings performed later?)
Mating management factors include:

Frequency and timing of matings during estrus. For example, with weaned sows that return to estrus early, the first mating can be delayed 12 to 24 hours.

Sanitation – environment should be sufficiently clean so cleaning vulvas is not necessary in most animals.

Stimulation – boar exposure, operator contact, use of belts or harnesses. Time should mimic natural mating (greater than 5 minutes of belt or back pressure, an additional 5 to10 minutes of boar exposure only).

Prevention of estrus females from going refractory – organization of labor and facility design to separate females that are being mated from those waiting.

Technique – proceed gently, use lubrication if needed. But lubrication isn't usually necessary if animals are in good standing heat and stimulation is adequate.

Pregnancy management includes:

Post-breeding heat detection – frequency, effective use of boars, lack of distractions.

Pregnancy diagnosis – accuracy, consistent timing, serial testing with A-mode ultra-sound machines.

Inventory management – tendency to neglect after the sow is diagnosed pregnant. Daily observation for abortion and health problems – visual pregnancy exam two to three weeks prefarrowing.

Step 5: Special Diagnostics

Anestrus diagnosis can be done by measuring serum progesterone levels. Two negative tests at 10-day intervals indicate that the animal is anestrus.

Alternatively, examining the ovaries at slaughter for corpus luteum can help determine cycling status. Examining the reproductive tract at slaughter or necropsy can assist in diagnosing other conditions, such as developmental defects, cystic ovaries and retained fetuses.

Mycotoxin and water testing also are helpful.

In pen mating situtations, it is nearly impossible to sort out what is wrong. Often the issue is not enough boars, feed problems (especially in cold weather and late summer), space, bedding, cooling, grouping by size or age. Deficiencies related to housing also will impact fertility in hand-mating and AI programs.

With natural, hand-mating programs, many of the factors related to AI need to be considered. One of the bigger controversies concerns how many matings a sow needs per service. Previous recommendations were "more is better." However, a single natural mating at the right time can result in equal or better fertility than two or three matings. This is based the hypothesis that uterine defense mechanisms wane as the female exits heat. Therefore, semen deposited during late estrus create an unfriendly environment for the developing embryo.

This also occurs with AI, but is less likely because a semen dose contains 10 to 20 times fewer sperm, and a female is less likely to stand for an AI mating as she goes out of heat.

Mating quality also is a consideration. A mating is rated as "good" when a boar breeds the sow for more than four minutes without a dismount, and the sow stands still.

Step 6: Improving Fertility

In nearly all noninfectious-reproductive failure cases that I have seen, the failure is the result of multiple deficiencies, and it's nearly impossible to identify them all.

These deficiencies require changing the management plan and day-to-day execution. The most effective strategy is to develop a new, all encompassing management plan for the breeding herd vs. attempting to change one thing at a time. Getting the advice of a veterinarian and/or a swine reproductive physiologist is critical.

Brad Thacker is with the Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, Iowa.
Brad Thacker, DVM, PhD