Inflammation of one or more of the mammary glands is referred to as mastitis. It is generally caused by an acute bacterial infection, although it can become chronic. In the lactating sow, clinical onset is about 12 hours postpartum, having started at farrowing. Mastitis can affect individual animals or a significant proportion of the herd due to environmental contamination. Mastitis reduces milk production, leading to poor intake of colostrum and milk by the piglets. This, in turn, will cause poor growth rates and potentially a greater likelihood of disease. Also of economic importance is the reduction in sow longevity.
Causes of mastitis
The most common cause of mastitis in pigs is coliform bacteria, including E. coli and Klebsiella species. They release an endotoxin that makes the sow unwell and reduces milk yield. Staphlococcus and streptococcus are also fairy common but may be less severe infections.
Bacteria either enter the mammary gland through the teat opening or via a wound. It can also be a secondary infection following a disease outbreak.
Symptoms
The first signs of mastitis are a high temperature and refusal to eat. Inappetence, even before farrowing, can indicate the start of mastitis. Nursery staff may also notice that the sow isn’t willing to suckle the piglets. The mammary glands appear red, swollen and are painful when palpated. The skin of the affected glands or whole udder can also be discolored. Bluing of the ears and tail is also reported, along with a red appearance of the area around the eye. Observation of a sow’s litter may also give an indication of cases of mastitis. Piglets may initially appear empty and hungry — squealing due to lack of milk, subsequently becoming quiet and sleepy.
Prevalence
“We see more cases of mastitis in the summer,” said Grace Webster, veterinarian at G W Pig Consultants. “But it is an all-year-round problem.” She described the two main types of mastitis she sees in practice. “The first is a sub-clinical infection, where one gland is affected. This is often picked up after weaning and whilst the sow is not unwell the condition is already chronic.” The second but most important type of cases is acute mastitis. “Most of the glands may be affected and it will be obvious that her piglets aren’t thriving.”
Risk factors
The possibility of mastitis being associated with another other health condition or disease should also be explored. “Anything that affects the immune system, for example PRRS, could mean that mastitis is seen as a secondary infection,” explained Webster. Mastitis may also occur following udder edema or the failure of milk letdown.
Increased intake of a low-fiber, high-energy diet in the days up to farrowing, along with reduction in exercise and drinking, all affect gut motility — causing constipation. “Coming up to farrowing, I would advise cutting back a bit on sow’s feed," said Webster. "Modern genetics mean that sows produce a lot of colostrum prior to farrowing, and the pressure caused by this can damage the mammary tissues." Webster also suggested that the ration should include a good source of fiber to prevent constipation. “In this situation, endotoxins from bacteria in the gut can cause hard udder, which can lead to the development of mastitis.”
Control strategies
One of the main ways mastitis infections are spread is via flies. “In outdoor-reared herds, you aren’t able to control flies; there aren’t any products licensed for use in pigs as there are for other species,” said Webster. Wallowing does help create a physical barrier, so producers should be vigilant in warm weather that wallows don’t dry up. “For indoor herds, fly control should be a top priority, particularly in the summer.”
In terms of bacterial control, Webster highlighted the importance using good quality bedding. “Use the best products available for sow and piglet housing; if bedding is damp or poorly produced, it can harbor microorganisms. Klebsiella is usually associated with wood shavings so if this organism is a problem on a unit, either change the source or I would recommend using shredded paper or chopped straw — if the slurry system can cope with this,” she explained. Webster also noted that end of season straw that has been poorly stored can also cause problems.
Hygiene in the sow’s environment is key to controlling bacteria and preventing infections. “Feces should be removed regularly, and pens need good drainage so they stay as dry as possible. Bacteria like damp, so using a desiccant type disinfectant can be helpful,” said Webster. The integrity of the flooring itself is also important as poor surfaces can cause traumatic injury, allowing bacteria into the mammary glands. “The other common damage to teats is from piglets teeth, which is why teeth clipping or grinding is a consideration. If there is a regular problem via this route, it is justified to employ one of these methods in the first few days of a piglet’s life,” said Webster.
Diagnosis and treatment
While there are a lot of risk factors that producers can help to manage, the most important thing is to ensure early diagnosis. “Milk samples can be taken from the affected glands in order to culture microorganisms. When investigating cases of mastitis, identifying the sources of infection is important. From that you can devise a targeted control plan,” said Webster. It may also be advisable to test the water source and bedding.
An early diagnosis is required to treat mastitis effectively and prevent long-term damage.
Determining antibiotic sensitivity can be useful for future cases. However, individual treatment of affected animals should begin immediately. “Generally, sows are given injections of antibiotics for three to four days. Oxytocin is also used to encourage milk-let down and the expulsion of infected matter [pus]. Non-steroidal anti-inflammatory drugs will reduce pain, inflammation and fever; fluids can also be given in severe cases,” said Webster. Even if the sow is successfully treated, serious infections will reduce milk production. “Supplementary milk should be given to piglets but if they are very young they may need to be fostered straight away,” she added.
Sub-clinical infections, that don’t affect all the glands, are possible during lactation. “Ideally, they should be similarly treated with intramuscular antibiotics. But they are often not detected until later when the condition has become chronic and an antibiotic at this stage would not be effective,” said Webster. In these cases nothing can be done to regain function in the gland and it can mean the sow has to be culled. “If she’s a really good sow and has only lost the use of one or two teats, it may be decided to keep her. However, where a producer is using hyperprolific genetics, once a sow has less than 12 functioning teats culling would be appropriate,” said Webster.
Conclusions
Failure to diagnose or treat mastitis can have a significant effect on a producer’s bottom line. Death of the sow and or the litter is the most obvious loss, but the effect on performance of surviving piglets and sows are not insignificant. Litters with a poor start in life may take some time to recover in terms of body weight. Poor development of the gut due to inadequate milk intake could also affect feed conversion.
Not all infections are preventable, but there are a number of straightforward management strategies that could help to reduce the number of cases. Close attention to the sow at farrowing and at weaning is important to spot infections quickly. Maintaining a high standard of hygiene both before and after farrowing is essential, along with effective fly control.
