March, 1999 ^. Volume 22, Number 2

The breeding and gestation period can be divided into distinct critical periods. The proper understanding of these periods allows breeding herd managers to analyze and improve their estrus detection, breeding, and gestation management programs. From a physiological perspective, gestation management should be a time of "stress reduction" management. Thirty to forty percent of potential pigs are lost during gestation (prenatal mortality) and about two-thirds of this loss occurs during the first 30 days of pregnancy (embryonic mortality). Figure 1 illustrates these "critical periods" and the following biological and management points can be used to further understand what is occurring at this time.

Weaning to Estrus

Fighting and high temperatures can significantly reduce feed intake which can impact a sow's ability to adequately recover from farrowing and can lead to longer wean-estrus intervals and reduced ovulation rate. Most sows will be in a negative energy balance for about a week post-weaning. Plenty of feed should be offered, especially when sows are in poor condition from lactation. Maintain temperatures < 85º F to stimulate feed intake.

Day 0

Fertilization (day 0) takes place about 2 days post-estrus onset. The percentage of eggs that are successfully fertilized (fertilization rate) determines the upper limit of potential litter size. Heat stress on the sow or boar can negatively affect fertilization rate.

Days 1 through 12

Embryos travel down the oviduct and enter the uterus about 2 days after fertilization. Embryos stay near the utero-tubal junction (ends of the uterine horns) unitl about day 7. Between days 7 to 10 they migrate throughout the uterus. Early embryos in the oviduct and uterus are susceptible to stressors on the sow such as heat stress and fighting. Avoid high temperatures and minimize unnecessary movement during this time span. Sows housed in groups should be commingled or moved to stalls during this time because of the decreased susceptibility of the embryos at this stage. Follow recommended practices for group size and monitor sow temperament and fighting in commingled groups to prevent overheated animals.

Days 11 through 14

Around day 11 embryos are hollow, flacid sacks called blastocysts and they undergo a radical transformation as the trophoblast (portion that will become embryonic membranes) elongates substantially. Blastocysts morph from round flacid sacks to long thin filamentous strands. Embyros begin to secrete estrogens into the uterine lumen that serve as the primary signal for maternal recognition of pregnancy and progesterone production by the corpora lutea (CL) is continued to maintain pregnancy.

Days 14 through 20

Implantation (attachment) of the trophoblast (extra-embryonic membrances) begins at about day 13 and is very firm by day 20. Attachment in swine is 'non-invasive' as the trophoblast never invades the uterine tissue and only attaches like velcro to the uterine endometrium. Attachement is also 'diffuse' in that diffusion of nutrients takes place across the entire placenta and failure to maintain an adequate attachment results in embryonic death. Sows should not be moved, re-mixed or unnecessarily handled, other than routine pregnancy detection, to promote good attachment and placental development.

Days 21 through 70

Checking for retrun to estrus (17 to 25 days post-mating) and(or) mechanical ultrasound devices are commonly used to assess pregnancy status and reduce non-productive sow days.

Days 30 through 114

By day 35 the embryo is considered a fetus and fetal mortality can occur when there are more fetuses than there is uterus to support them. Around day 40 to 45 calcification of the fetal skeleton occurs and after this point, fetuses cannot be reabsorbed by the uterus as dead embryos were. Fetuses that die become mummified and are expelled at farrowing.

Gestation feeding programs must provide sufficient energy, as well as other essential nutrients to meet the needs for maintaining sow body functions, development of the fetuses, associated uterine tissues, and the mammary gland, and a modest increase in maternal body weight. Successful gestation management includes monitoring and evaluating body energy status throughout gestation and adjusting feeding levels to achieve desired energy status at the time of farrowing. Feed intake adjustments are often needed to meet desired gestation weight gain and body condition scores.

Days 84 through 114

Stress on the sow in the last 30 days of pregnancy will often lead to increased number of stillborn pigs.

Todd See

What are the benefits of the Accelerated Pseudorabies Eradication Program?

The accelerated program gives producers with infected herds another option to eliminate pseudorabies from their herds. Risk to uninfected herds will be decreased. Progress of the existing National Pseudorabies Eradication Program has recently been threatened because of the economic crisis in the pork industry. A number of producers have stopped vaccinating their herds as they have not been able to afford the purchase of the pseudorabies vaccine. This seriously affects progress in the National Pseudorabies Eradication Program by allowing the virus to spread more rapidly from pseudorabies-infected herds to unvaccinated, uninfected swine herds.

A resurgence of pseudorabies in the United States would put additional economic stress on already distressed producers, delay completion of the national program leading to additional industry and government costs, and delay the opportunities afforded to the industry in being pseudorabies free.

Who is eligible to participate?

All herds known to be infected with pseudorabies may participate regardless of geographic location, size, and duration of quarantine status. Newly infected herds must apply for eligibility with the State Pseudorabies Committee.

Participation in the accelerated program is voluntary. Producers need to visit about their particular herd situation with the State or Federal animal health official that has been working with them on their herd clean-up plan and their veterinarian. Individual farm situation questions about premises, site, or barn participation need to be addressed through the farm's official pesudorabies herd clean-up plan and the official pseudorabies epidemiologist. Producers with affected herds who choose not to participate must still adhere to established pseudorabies eradication standards.

North Carolina:

State Veterinarian: Dr. John Atwell (919-733-7601)
AVIC: Vacant (919-513-4170); ask for Dr. Terry Clark or acting AVIC

How are producers being compensated for depopulation?

Producers with known pseudorabies-infected herds will be compensated based on present fair market value. The compensation will be based on a per pound basis for the net weight of swine removed from the farm and a fixed amount per head based on the class of swine, termed the Producer Cost Offset.

The per pound compensation will be based on the simple average of the previous week's, Wednesday, Thursday and Friday Iowa/Southern Minnesota weighted average base market price for a 185-pound carcass (49-51% lean) multiplied by .74 to arrive at the live price. The per pound compensation amount will be updated each week. This per pound price will apply to all swine depopulated, without regard to class, size, age, or weight.

The Producer Cost Offset is intended to cover the producer costs to participate in the accelerated program and is dependent on the time period during which the producer contacts USDA to express interest in the program. The first time block will be 30 days from the starting day of the program. The second will be the next 30 days with the third and final time block to the end of the program.

The producer's final compensation will consist of adding the per head compensation that is based on the number of swine multiplied by the appropriate Producer Cost Offset to the per pound compensation, that is based on the total weight of the depopulated swine multiplied by the appropriate market price.

How will the herds be depopulated? When can producers repopulate?

USDA will oversee the depopulation and disposal. Hog supplies exceeding current packing plant capacity have precipitated the economic crisis in the pork industry. Therefore, other routes for disposal will be utilized that meet Federal, State, and local regulations. Producers can repopulate their herds in accordance to the National Pseudorabies Program Standards.

For more information on this program, contact the APHIS Pseudorabies Hotline for further information at 1-800-601-9327 or visit the APHIS home page at http://www.aphis.usda.gov. In addition, interested practitioners may contact the AASP office for further information at 1-515-465-5255.

American Association of Swine Practitioners

Water is at the basis of any form of life that we know, and there is no doubt that pigs need it. A question, however, is how much water is needed for raising pigs. This question may seem irrelevant since the water bill of a typical farm is not major compared to other cost factors. This, though, paints only a small portion of the picture; disposal of water increases production cost, and this problem will only get bigger with the environmental regulations on the horizon.

Most swine farms use water as a medium to collect swine waste, or to flush waste from the building. As a result, the waste coming out of a swine barn contains only 2 to 4% dry matter. This waste is then collected in a lagoon, from which it is irrigated on a spray field (based on nitrogen). According to Kelly Zering, NC State's economist, this process of waste disposal costs approximately $1 per pig finished.

In the future, this form of waste disposal will not be acceptable. Waste will have to be applied to cropland at a rate such that nutrients, including nitrogen and phosphorus, do not accumulate. This means that the "spray field" required is much larger than current spray-field requirements. Thus, waste will have to be transported over larger distances or other solutions to deal with the waste will have to be sought. This transport will increase the cost, a cost that is mainly caused by the high water content of the waste.

The US government is talking about manure export "banks"; centrally managed organizations that collect manure from swine farmers and then arrange for transport to crop producing regions. In Europe such banks exist, to the dismay of most farmers. These banks charge a hefty fee (about 3 cents per gallon) to the farmers for collecting manure (sometimes, participation is not voluntary), and it is a fee in which the water content of the manure plays a major role; the more concentrated the manure, the cheaper the transport becomes on a per pound basis. As this manure is more concentrated, the transport cost per unit of nutrients thus decreases even further.

One way to make waste management and transport easier is to make it more concentrated, thus to reduce water. This is unfortunately a recommendation that most farmers do not appreciate . Current facilities are build to work with flush or pit-recharge systems, and on the surface it seems difficult and expensive to alter this. But let's look at the potential. If swine manure was obtained with a low moisture content, it could be pelleted and shipped back to the crop producing regions were the feedstuffs came from.

So what can be done to reduce water waste? Obviously, flush systems are responsible for a major portion of the water. This water is typically recycled from the lagoon, but it still results in a very diluted waste stream. If remodeling of a barn is in order, consider other waste collection streams. Deep pit systems result in waste with 12-15% dry matter, a step in the right direction (but odor and ammonia might be a larger concern in those systems). An alternative deep pit system is being explored in the Midwest; manure is deposited in a very deep pit on top of wood shavings, though which air is blown. With this system, it should be possible to generate a very dry waste product with minimal odor. A problem in this case may be that by adding wood shavings, the waste volume might increase again.

Another solution is to use a scraper system. Scrapers have been used in animal housing for many years, and most farmers were glad to see them replaced with other systems as a cable breakage meant a couple hours stuck in a dirty pit to fix the system. Scrapers are expensive, too, but have the potential to allow for the collection of fairly dry waste. Belts, as used in the poultry industry, are another potential solution. Again expensive, but if very dry manure is desired then they are the way to go.

Another important source of water in the waste stream is rainfall. This is only a problem since manure is stored in open lagoons, a system which appears doomed by the US government.

Water wastage may be reduced through management methods as well. Fix leaking drinkers and water lines. Install cups under the drinkers, or even better, install wet/dry feeders, where any spilled water mixes with the feed such that it is consumed. Wet/dry feeders were shown to reduce manure volume in deep-pit systems with a third. Liquid feeding systems allow for even further reductions, but such systems are expensive and not well suited for corn-soy diets as these ingredients do not mix well with water. In principle, pigs can get by with less than 2 parts of water per part of feed (if it is not too hot), while pigs typically lead to the disappearance of about 4 to 5 parts of water per part of feed if water is provided through a regular drinker.

Another source of water is cleaning water. Although cleaning the barn is one of the most important housekeeping items in a farm, water usage can be reduced substantially by presoaking the barn, preferably with a foaming agent rather than water. Subsequently, the barn should be washed with a high-pressure washer.

The most important of all is to start considering what the impact is of water on your waste strategy. If water does not pose a problem since ample spray-field area is available, then the above is of no concern. However, if a more concentrated manure would be of interest, start paying attention to how much water is added to the waste and how this can be reduced.

Theo van Kempen

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Last modified February 23, 1999.