March, 1997 ^. Volume 20, Number 2

What

Atypical "cases" are classified as herds that see:

1. Large proportion of sow herd off feed with fevers between 104 and 106° F (North Carolina cases up to 108° F.)
2. 10% to 50% of sow herd aborts within 5 weeks.
3. Sows abort at ANY STAGE of gestation, not only in late gestation.
4. Variable, but potentially severe levels of sow mortality. Between 5% to 10% of the sows have died within the 5-week period.

All outbreak herds to date have been vaccinated, and many have experienced "normal" PRRS outbreaks before.

Outbreaks have lasted up to 3 months, with production returning to normal afterwards.

Where

Approximately 35 "cases" have been reported to date. Most "cases" have occurred in southeast Iowa. Some "cases" have been reported from Minnesota, Illinois, Colorado and Missouri. North Carolina has had 4 "cases" to date, beginning this past summer.

Causes

There is no consensus on the exact cause of these outbreaks at this time. The disease has not been successfully reproduced experimentally with any of the virus isolates to date, but experiments are underway or being planned.

However, PRRS virus has been isolated, or a strong antibody response detected, after the onset of the severe clinical signs in ALL BUT ONE HERD. The experts assembled by NPPC generally felt that at this time the majority of evidence points to a type of PRRS. It was very disappointing to all present that the commercially available vaccine has apparently not stopped these outbreaks. Aggressive investigations into other possible causes of these and any new cases are ongoing.

What can I do?

Extended isolation of all breeding stock introductions/purchases!

If this is truly another form of PRRS virus, isolation of new breeding stock for a MINIMUM OF 60 DAYS is one management practice most likely to minimize the risk of introducing the virus into your herd. This recommendation is based upon earlier clinical experiences reported by Dr. Scott Dee DVM, MS, PhD, which parallel our recent experiences in an integrated North Carolina swine production company using his recommendations.

It is obvious that isolation alone will not be an absolute protection against this "new" PRRS syndrome. However, it appears that breeding stock replacements that are isolated long enough for their antibody levels to fall and disappear are much less likely to carry clinical disease (PRRS) into the receiving herds than if they were introduced directly into the herd, shortly after having been infected, with high antibody levels, and therefore a relatively higher likelihood of shedding virus to the receiving herd.

ASK BLUNT QUESTIONS DIRECTLY TO THE SUPPLIER AND THEIR VETERINARIAN BEFORE RECEIVING EACH SHIPMENT OF BREEDING STOCK WHETHER THEIR HERD OR OTHER CUSTOMERS' HAVE SEEN SIGNS OF ATYPICAL PRRS. It is your investment that is at risk, and you don't need to purchase stock from any supplier which refuses to give you direct answers about the current health of their herd. REALIZE THAT THERE IS NO DIAGNOSTIC TEST YET TO IDENTIFY ANIMALS INFECTED WITH THE CAUSE OF THIS TYPICAL PRRS SYNDROME. Therefore, herds (and therefore suppliers) could still be infected with such an agent even though they have HONESTLY not seen clinical signs of the syndrome. Hence, again, you need to isolate all introductions to reduce the likelihood of them shedding the "virus" to your stock upon addition to the herd.

Extended isolation will also help you spot problem animals and better prevent other economically devastating diseases such as TGE.

What should I do if we think we're having a break?

Call your herd veterinarian and have them collect the following samples to send to the veterinary diagnostic laboratory:

1. Live sows that are currently sick with the disease.

2. Weakborn piglets collected before they could suckle colostrum.

3. Suckling or nursery pigs with pneumonia or their tissues including tonsils, lungs, liver, kidney, spleen, brain, uterus, placenta, ovaries and whole fetuses with umbilical cords.

4. Immediately collect blood samples and collect convalescent blood samples 3 to 4 weeks later.

Minimize shipments of piglets or pigs to other premises or ship them to a minimum number of sites with no other sources of pigs. Notify Dr. Gene Erickson (919-733-3986) at the state diagnostic laboratory or myself (Dr. Monte McCaw, 919-829-4294) at NCSU College of Veterinary Medicine.

Monte McCaw

Detection of estrus is an important component in A.I. breeding programs and is difficult to optimize. The keys to successful detection of estrus are to be observant, prevent over-exposure to boars and understand the physiological and behavioral signs that occur prior to the standing reflex. These signs should be used as a guide with regards to how much time should be spent trying to stimulate sows.

Identification of the physiological signs of estrus is not difficult. These include increased activity and vocalizations; swelling of the vulva and enlargement of the clitoris; the presence of a sticky discharge; elevation of the ears and immobilization in response to manual back pressure. However, estrus often is missed or misdiagnosed because many of these signs are overlooked. Accurate and efficient identification of estrus requires two things: (a) a thorough knowledge of the chronological order in which these signs occur as females enter their period of sexual receptivity ; and (b) establishment of heat detection protocols that enhance the expression of estrous behaviors.

The first sign that females are coming into heat is an increase in activity and vocalizations. When housed in crates, sows commonly move backward and forward or from side to side within the crate and often attempt to nibble or nose females in adjacent crates. In addition, they sometimes will paw at the front door of the crate and "chant" to animals in crates beside them. When housed in pens, characteristic activities include sniffing; nuzzling the rear and fore flanks; and attempting to mount or ride other females. It is important to remember that sows attempting to mount or those actually riding other females are not in heat, but rather either just coming in or going out of their period of sexual receptivity.

Reddening and swelling of the vulva usually either accompanies or occurs shortly after the increase in activity. The change in the size and color of the vulva is the result of an increase in blood flow and retention of fluids in the female external genitalia. As a result, the external lips of the vulva often are pushed outward exposing a portion of its inner lining which is highly vascular. Due to these changes, the opening to the vagina often appears to increase in size. In contrast, in females that are not in heat, the external lips of the vulva are curled inward and block the opening to the vagina giving it a small, puckered appearance. Reliance on only the appearance of the vulva as an indication of sexual receptivity and the cue for breeding is a common mistake associated with A.I. The size and color change of the vulva actually is greatest just prior to the period of estrus in which females will "stand" for breeding or exhibit the immobilization reflex. In addition, reddening and swelling of the vulva often do not occur in older parity sows during estrus. It is common for the skin around the vulva to become stretched or loose during farrowing. Thus, in older sows, even though the physiological changes which normally cause swelling and reddening still occur, the change in color and size are masked by the loose, flabby skin around with the vulva. The appearance of red, swollen vulvas should be recorded on breeding records and used as a reminder by breeding technicians to spend additional time over the next few days examining those sows or gilts for the immobilization response.

The presence of a "sticky" discharge and enlargement of the clitoris are changes that usually occur immediately before and during the standing reflex. The clitoris is a small, finger like structure which is located inside the base of the vulva in the crease formed by the two lips. When females are in heat, the clitoris is engorged with blood which causes it to protrude outward and have a bright red color. When females are not in heat, the clitoris is flat and has a pale, light pink color. To observe the clitoris, it is necessary to pull the external lips of the vulva apart and outward. This exposes the internal fold where the lips join and the clitoris is located.

Mucous obtained from the inside lining of the vulva from sows that are not in heat has a slimy or slick feel to it. Just prior to the initiation of the standing reflex, the consistency of the mucous changes and becomes tacky or sticky. This change in composition is caused by hormone changes that normally occur during sexual receptivity. Assessment of the consistency of the mucous commonly is referred to as the "thumb check". The thumb check is performed by wiping the inside lining of the vulva with the thumb to obtain a sample of mucous. Next, the thumb and first finger (pointer) are pressed together and slowly pulled apart. The sample is considered sticky or tacky is small strands of mucous remain connected to both the thumb and pointer as they are drawn apart. In most cases, an engorged clitoris and sticky mucous are good indications that the female is in standing heat or within several hours of exhibiting the immobilization reflex.

The best indication that sows are sexually receptive and ready to be inseminated is the occurrence of the standing reflex or immobilization response. When provided with the appropriate stimuli, receptive females will initiate isometric contractions of most of their skeletal muscles. This results in the female remaining rigid or "locked up" in anticipation of being mounted by a boar for breeding. Often the ears of sows and gilts will become erect during the standing reflex. This is commonly called the "ear popping" response.

Pheromones produced by boars are the most potent and effective inducer of the standing reflex in receptive females. For sows housed in crates, running a boar in front of sows while a breeding technician applies back pressure is a common and effective method of estrous detection. Sows in crates that are in heat will move forward and assume the standing reflex as the boar moves in front of the crate. In addition, when back pressure is applied, females that are truly in heat will actually push back when pressure is applied. This is a natural response as she is preparing herself to be mounted by the boar for breeding. Sows in crates that actually try and move away from back pressure, even though they may exhibit other positive signs, probably are not in estrus. In pens, sows will move to the front of the pen as the boar passes by. If back pressure is applied and the sow is in heat, then she will exhibit the standing reflex. If back pressure is applied and the sow is not in heat, then she usually will run away from the back pressure in an attempt to escape. Estrous females housed in pens will sometimes attempt to follow the movement of a boar as he passes in front of their pen. This is due to the fact that sexually receptive females seek out males more so than males finding sows that are in heat.

The manner in which boar exposure is presented to sows and gilts can influence the accurate detection of the standing reflex. Because it involves isometric muscle contractions, maintenance of the standing reflex requires a considerable amount of energy. As a result, estrous females exhibiting the standing reflex can become fatigued or tired. If a female becomes fatigued, then she usually can not resume a standing reflex for several hours. Consequently, boar exposure during estrous detection should be restricted to small groups of sows, either 5 to 10 crates or 1 to 2 pens. These small groups should be examined carefully and receptive females identified. Exposure of the boar to larger groups of females could result in detection errors due to estrous females becoming fatigued and not exhibiting a standing reflex when checked with the back pressure test.

Billy Flowers
1996 Pork Profitability Summit

Pork producers who want to optimize their pigs' genetic potential should not overlook the role of vitamins in the swine diet. A recent study conducted at Iowa State University measured the rate of gain and feed efficiency of pigs fed diets containing five B vitamins at various levels. Researchers found that optimum performance did not occur until pigs received vitamins at 3-5 times the level currently recommended by the National Research Council (NRC).

Diets were formulated to contain 70%, 170%, 270%, 370% or 470% of the NRC requirements of the B vitamins: riboflavin, niacin, pantothenic acid, B12 and folic acid. These vitamins are all critically involved in supporting protein synthesis and muscle development. Researchers analyzed the animals' response by genotype and found that one group had a high capacity to grow muscle. ISU swine nutritionist Dr. Tim Stahly estimates that they would grade between 57% to 59% muscle at 240 lbs. The other group was more moderate in its lean growth and muscle capacity. Pigs were fed from 18 lbs to 75 lbs and, when results were averaged for the length of the entire trial, scientists found that rate of gain was greatest at 470% for the high-lean growth pigs and 370% for the moderate-lean growth group.

Stahly points out that the B vitamin needs were estimated 20-30 years ago. "Since then, we've had a significant change in the animal's capacity to grow muscle. These results suggest that as we increase that capacity, the needs for certain vitamins are substantially greater than what we previously estimated," he adds.

HogHealth
Vol. 6, No. 6

The Chicago Mercantile Exchange listing of contract hog prices for 1997 or later has caused pork producers to scratch their heads in bewilderment. "Some think the listings are extremely high live hog prices when in actuality the listing are carcass prices," explains Bill Luce, Oklahoma Cooperative Extension swine specialist. Thus, a $70 per hundredweight carcass price, assuming a 74% carcass yield, equates to a live price of $51.80 per hundredweight.

Luce points out that the new swine carcass futures contracts differ significantly from the traditional live hog contract; they are carcass contracts rather than live weight contracts and they are cash settled. Sellers could be required to deliver hogs to a designated delivery point to settle an open contract under the traditional live hog contract.

"With the new contract, the cash prices used to settle the contract in the designated delivery month is an average of the previous 2 days' prices reported by the USDA for the western Corn Belt, eastern Corn Belt and the Mid-South direct carcass weight markets," he explains.

The new contracts are in 40,000-lb trading units and are based on a 170- to 190-lb carcass with 0.80-0.99 inch of backfat at the last rib. "The price quote is in cents per pound and the minimum fluctuation is 0.025 cent per pound. The daily price limit is 1.5 cents with no limits on the last 2 trading days," Luce adds.

HogHealth
Vol. 6, No. 6

If pigs are 3 weeks or older when weaned, producers should supply one nipple waterer for every 10 pigs. A minimum of two per pen is suggested and, if pigs are younger, supply one nipple water for every eight pigs.

To prevent metal corrosion in hog builds, University of Illinois agricultural engineers suggest using galvanized and painted galvanized metal to prevent corrosion. Producers should also keep all surfaces clean in the building, use ventilation, keep atmospheric humidity below 70%-80% and avoid condensation whenever possible.

The National Office of Animal Science, United Kingdom, reports that without the use of feed additives, over 1 million tons more feed would be needed each year for finishing pigs in European herds. They also report that using feed additives has reduced manure output by an estimated 7 million cubic meters annually.

HogHealth
Vol. 6, No. 6

The December Hogs and Pigs Report was more positive than expected, according to Glenn Grimes, NPPC market consultant. If '97 marketings are consistent with the report, we would expect first quarter prices at the five major markets to average $53-55 per cwt. While hog slaughter year-to-date was down about 4 percent, cash prices at the five major markets were up 27 percent. Typically we would see about a 12 percent increase in price, said Grimes.

Pork Leader
January 3, 1997
Vol. 16, No. 1

Hog producers need to become more attentive to feed waste in the face of high grain prices, according to Jerry Shurson, swine specialist, University of Minnesota. Well-managed nursery, grower and finisher feeders can still waste 2%-11%, depending on feeder design. "Some studies show that feed waste may exceed 25%," he adds. "Waste not only increases feed cost per pound of pork produced, but it also increases waste storage and handling costs."

Shurson cites a 1994 Texas Tech University study evaluating 17 commercially available nursery feeders from 13 different manufacturers. Feed waste for the feeders ranged from 2.55%-10.2%. As a result, differences between feed per pound of gain without feed waste and feed per pound of gain including waste ranged from .01 to .23 lb. The waste increased feed cost from $ .05 to $1.10 per nursery pig.

"Proper feeder adjustment is also critical for preventing excessive waste, but adjusting feeders too tightly can limit feed intake, resulting in slower gains," says Shurson. He recommends checking feeders at least 3 times a week to minimize waste. A good rule is to adjust feeder settings so that there is slightly less than 50% of the feed trough covered. This keeps feed fresher, minimizes spoilage and reduces feed buildup that contributes to waste.

Using a low-cost, growth-promoting antibiotic throughout the grower-finisher phase also will help to optimize feed usage and daily gains.

HogHealth
Vol. 6, No. 5

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Last modified August 1, 2000