Sow and gilt health maintenance in gestation is impacted by a host of factors. The traditional approach to sow and gilt health uses “health” and “disease” synonymously. It is more correct to consider disease status as one element of overall health.
Each new veterinary discovery reveals that diligent attention to nutrition, management and environment can enhance the ability of the immune system to neutralize disease challenges to the sow or gilt. Disease challenges are increasingly complex; disease organisms are increasingly evasive of the immune system, and some, like porcine reproductive and respiratory syndrome (PPRS) virus, attack the immune system directly and use immune cells to replicate.
Managing sows and gilts to insure the immune system has maximum ability to neutralize challenges is critical.
Observation is Critical
It is also clear that when treatments exist for a particular disease, the effectiveness of treatment improves when it is applied early in the infection process. Early detection requires that caretakers have keen observation skills, so the disease is detected before clinical signs become severe.
Subtle changes are the first signs of disease onset. Detecting these changes in sow and gilt health requires consistent, daily observation and detailed communication of changes in animal status among multiple caretakers.
A consistent process for observing animals is the most important. Subtle changes in animal attitude or behavior, respiratory rate, activity level and general appearance can indicate the start of a disease problem. If a different person observes a sow from a different position at a different pace, at a different time of day, subtle changes in behavior and appearance can exist that have little to do with changes to the sow's disease or health status. This is especially the case in chronic conditions that develop slowly over time but have significant impact on lifetime performance.
Typically, observation of gestating sows occurs only at feeding. This allows detection of very sick animals that are off feed or fail to rise and eat, but it does not allow for detection of subtle changes in respiratory rate.
Gestating sows are best observed at rest, when they are calm. Finding a time when the barn is at rest will facilitate observation of subtle and earlier signs of infection. All animals should be observed every day.
Traditional approaches to sow and gilt gestational health have focused on acute disease conditions. This is because acute illness in the gestating sow or gilt frequently has repercussions for the current litter. When the disease or health condition results in abortion, the economic loss is obvious and the urgency to address the disease problem is highest.
Other authors of this Blueprint have made strong cases for the significant economic impact of chronic, non-disease impacts on health. The discussion that follows begins with general recommendations targeted to management of health in sows and gilts, followed by some specific consideration of hoof lesions and cystic ovaries.
Acute Health Management
Work with your veterinarian to identify the specific diseases in your system. Acute disease management is a very farm-specific activity.
Successful farms utilize veterinary diagnostic assistance to characterize the specific diseases present and the best interventions for each situation. Additionally, successful managers recognize that all medications and vaccines have some degree of negative impact on the performance of the sow and gilt.
In situations where a disease is present (in the case of antibiotic use) or exposure occurs (in the case of vaccine), there is a clear overall benefit to the correct use of these interventions. However, when the treatment or vaccine is misapplied or unnecessary, the benefit will not be realized and harm may even result.
In addition to increasing cost and adding labor, using vaccines that are not necessary can stress sows because they are designed to elicit an immune response. This immune response can limit feed intake and redirect energy resources away from pig development or replacement of sow or gilt body condition.
Needles have been shown to transfer viral diseases. And, the risk of abscesses and broken needles is a reality.
Antibiotics that are not needed, even when applied via feed or water, can have negative impacts on the normal, protective bacteria of the intestinal tract. Additionally, research shows that bacteria have the ability to trade genetic material, which contributes to the spread of antibiotic resistance. Developing resistance in non-pathogenic bacteria may have repercussions when pathogenic bacteria arrive at the farm.
The least effective, and even detrimental to health on sow farms, is the use of so-called “preventive shots.” Eliminate these preventive injections, which commonly consist of antibiotics plus other pharmaceuticals designed to provide blanket protection against several conditions that may be problems in the herd.
Considering a few characteristics of antibiotics in general helps illustrate the limited value of this practice. Few antibiotic formulations remain in the sow or gilt's system at effective levels for extended periods of time. The only bacteria that are affected are those present at the time of injection. Additionally, to effectively treat most bacteria requires multiple treatments.
Antibiotics do not sterilize the animal of pathogens, and recovery from disease still relies on the animal's immune system. Additionally, the mixing of several pharmaceuticals for injection constitutes a practice called “compounding” which, except for specific circumstances, is an illegal practice.
The true cost of so-called preventive shots is a sense of false security and a relaxed diligence in finding and correcting the sources of the problems these injections are thought to address. Again, in addition to all of the health-related issues, the practice of preventive shots contributes to higher economic costs on the sow farm.
Feed, Water Medications
Remember that most clinical diseases can be accompanied by decreased feed and water intake. Consequently, administering antibiotics via feed and water can miss the most affected animals.
Often, water and feed medications are consumed at the highest rate by the healthiest animals, since they are unaffected by disease. The animals most in need of treatment frequently consume the least feed or water medication due to the adverse impacts of the disease condition they are experiencing. Rely on individual animal treatment using injectable antibiotics as much as possible for clinical cases.
Recognize that disease profiles on farms change over time. Make sure that you are not treating for, or attempting to prevent, a disease problem that does not currently represent a risk to your operation. Eliminate treatments and vaccinations that do not address a problem diagnosed in your herd. Use only vaccines and antigens against diseases diagnosed in your herd or for which exposure is likely.
Substantial savings can occur when producers eliminate combination vaccines that include antigens for diseases sows are not exposed to. Be sure to consult your veterinarian before making changes to a successful program.
If you're concerned about removing the potential protection of certain antigens, the use of sentinel animals to assess risk might be useful. This generally involves removing the vaccine from a small subset of the herd, and monitoring them for the disease of concern before committing to a whole herd change.
Focus on Prevention
Realize that prevention is always the cheapest and, in the case of some diseases, the only intervention available. It is time for pork producers to begin applying rational, science-based biosecurity interventions in earnest.
Often, the simplest interventions are most effective. For example, changing boots and coveralls and washing hands have been shown to interrupt the transmission of many swine pathogens. This must be done diligently. Each lapse undermines the efforts of the whole operation.
When implementing a biosecurity program, it is important to keep a few concepts in mind:
Simple tasks are more likely to be done regularly and correctly.
Avoid the “all or none” mentality. Biosecurity is about reducing risk. Every little improvement reduces the risk over time.
Divide and conquer. Separate ages and different health status animals as much as possible with different apparel and equipment.
If it stinks, wash it. Manure and pig secretions are often as effective at transferring pathogens among animals as animals themselves.
Focus on what you can control. Keep employees focused on this. Do not allow risks that you cannot control to become an excuse to relax effort against risks you can control.
Help employees understand what is at risk. Most employees are motivated by contributing to a successful team.
Keep pets out, control rodents and birds and know where visitors have been before they arrive.
The most recent slaughter evaluation of cull sows at Iowa State University (ISU) evaluated 3,158 animals and found more than 67.5% (2,131 animals) had foot lesions. Additionally, there were 6.3% (199 animals) with cystic ovaries.
Preliminary evaluation suggests hoof lesions were widespread. Sows with higher body condition scores were more likely to have cystic ovaries. This may indicate that sows with cystic ovaries remain undetected in inventory and gain weight while not contributing to the productivity of the herd.
A relatively low prevalence of cystic ovaries can impact farm productivity significantly and yet remain difficult to diagnose and treat.
The first step is to monitor and record sow reproductive performance so that animals that repetitively fail to conceive can be identified and targeted for further examination. Cystic ovaries remain challenging to identify in the live animal, but progress has been made.
Research has demonstrated that cystic ovaries can be diagnosed by transrectal as well as transabdominal real-time ultrasound similar to that used for pregnancy detection.
Additionally, serum progesterone levels are reportedly elevated in sows with cystic ovaries. These levels can be detected by recently developed commercial enzyme-linked immunosorbent assay kits, which are also used for identifying elevated progesterone levels in pregnant sows.
These tools can be more effectively applied to identify cystic ovaries in a targeted, at-risk population than as a screening tool for the whole farm. It also reinforces the necessity for good records to help accurately identify the high-risk sows in your herd.
The lesions most commonly seen in the ISU survey were large, bilateral, multicystic ovaries without gross structures such as corpus lutea that indicated recent pregnancy or ovulatory activity. Most of these ovaries had a gross appearance of cysts with thickened walls that suggested luteinized tissue was present.
The presence of luteinized tissue would be expected to produce progesterone, inhibiting estrus activity and behavioral signs of estrus. The fact that they were usually bilateral suggests a systemic problem, such as a disruption of routine hormone fluctuations in the sow, rather than structural problems with the ovaries themselves.
The causes of cystic ovaries are many, but the most commonly recognized include causes of impaired luteinizing hormone (LH) surge that lead to ovulation failure, which subsequently leads to the development of cystic ovaries. Increased incidence of cystic ovaries has been associated with shortened lactation lengths, zearalenone toxicity and other stressors. In the current study, an increased incidence of cystic ovaries was associated with heavier body condition.
The hoof lesions observed in this ISU study were significantly more prevalent than expected by the research team. A range of factors and combinations of factors, including injury and nutritional deficiencies, undoubtedly causes hoof lesions.
A key concern with a survey analysis of the problem, especially postmortem, is that the foot is a complex structure designed to endure cuts, abrasions and limited, small cracks.
The hoof is primarily composed of dense, hard tissue that is no longer supplied with blood and nutrients. As a result, cuts, cracks and abrasions are not repaired, but rather replaced by new growth from the top of the hoof. The difference between normal wear and a problem is difficult to discern. Another result of the normal hoof growth process is that treatment interventions may not have immediate results. Disciplined patience is critical in order to correct the problem long-term.
In live animals, evaluating soundness can guide decisions regarding hoof lesions. Given the limited capacity for hoof repair, maintaining an environment that preserves hoof integrity and foot health is key. The first and most obvious steps are to eliminate injury hazards.
Keep in mind that some injuries can be traumatic, such as cuts or splits due to uneven or sharp surfaces or the protrusion of bolts from penning. Injuries can also be the result of chronic impact on the foot. Slick surfaces can change the animal's gait and weight distribution, resulting in abnormal wear or cracks over time. Several studies have agreed with the ISU study, which found that lesions are more common in rear feet. No cause for this has been confirmed.
Flooring, crates, crowding and handling as gilts have all been indicated as key contributors to lameness in sows. Creating the desired flooring conditions is a delicate balance between too rough and too slick for heavy sows.
Concrete floors certainly can be used with success, but are particularly difficult to design with the correct balance. Concrete floors that are too rough result from the use of particulates that have incorrect grain size and consistency, or floors that have broken down due to organic acids and wear.
New concrete can be slippery and have sharp edges, and chemicals that result from the curing process can be irritating to sensitive structures of the foot. Poor flooring can be improved by altering texture, taking steps to reduce moisture, providing padding or removing sharp points.
Biotin, also known as vitamin H, supplementation has received attention as a potential treatment for hoof problems, but its impact depends on several factors, and results are limited to a narrow range of circumstances. Biotin supplementation has been useful in diets that are deficient, but additional supplementation in diets that have adequate biotin has not been shown to improve hoof lesions.
Corn is a good source of biotin, but other substrates such as milo and barley may be deficient. Biotin can only be expected to improve hoof integrity. Lameness issues that result from pad or sole injuries should not be expected to respond to biotin supplementation. Close inspection of both the diet and the feet of lame sows can provide direction on the use of biotin supplementation.
Both acute and chronic disease problems in gestation rely on accurate diagnosis and individual animal approaches to treatment. Research continues to show significant associations between body condition and acute disease problems such as pneumonia, as well as chronic problems such as lameness.