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UTIs are among the most frequent bacterial infections in the herd but they are rarely diagnosed or taken into consideration by veterinarians. Due to the fact that in standard rearing conditions the sow’s vulva is often in strict contact with the fecal material, it is quite simple to understand how the infection can proceed quickly and easily through the opened parturition channel.
UTIs are one of the most common and unidentified causes of death or discharge of sows, and a significant correlation has been established between urinary, genital and mammary infections in lactating sows (Wanyoike and Bilkei, 2006).
The increasing need for accuracy on swine breeding farms, specifically focused on the management of hyperprolific genotypes in the area of parturition and lactation will probably, in the near future, require paying more attention to UTI management in pig units, with three main objectives:
- Favor quick achievement of maximum feed intake by sows.
- Reduce piglet mortality or discharge in lactation to well below 10%.
- Reduce wean to service interval.
It is quite obvious that such a program needs to be 100% multifactorial, and that no “golden bullet” is actually available: nevertheless, increasing attention to UTI and a nutritional management of the same would probably prove helpful.
An extensive study conducted in Italy in 2010-2011 confirmed a very high incidence of positive bacteriuria in sows, with an increasing percentage of positive samples correlated with age and physiological phase (lactation vs. pregnancy):
Table 1. Bacteriuria positive in sows urine samples (Grattarola et al., 2010-2011).
| Negative | Positive | Total | |
| Nulliparous in gestation | 91% (n=60) | 9% (n=6) | 100% (n=66) |
| Primiparous in lactation | 79% (n=39) | 21% (n=10) | 100% (n=49) |
| Multiparous in gestation | 77% (n=58) | 23% (n=17) | 100% (n=75) |
| Multiparous in lactation | 60% (n=36) | 40% (n=24) | 100% (n=60) |
| Culled | 70% (n=50) | 30% (n=22) | 100% (n=72) |
In almost all the studies Escherichia coli is the prevalent microorganism involved, reaching percentages as high as 90% of the isolates: it is well-known that a relatively acidic urinary pH is a barrier for ascending bladder infections from E.coli, which grows much better in a neutral/slightly basic environment.
The possible role of nutrition in the achievement of a stable, low urinary pH in lactating sows has been widely and extensively studied. We too, in a previous study (Piumatti et al., 2007), testing separately in a Latin-square experiment the efficacy of three single nutritional actions on the sows urinary pH, achieved a maximum effect when substituting limestone with microencapsulated CaCl2, an intermediate effect with the substitution of limestone with calcium sulphate (gypsum), and the lowest effect by simply adding a blend of organic acids to the control feed.
More recently, we have tested a simple nutritional strategy intended to obtain strong acidification of the lactating sows’ urine, based on 4 actions:
1. Substituting the majority of calcium sources from limestone with:
a. Microencapsulated CaCl2 (inclusion rate: 0,5%)
b. Calcium sulphate (inclusion rate: 0,5/0,7%)
c. Calcium formiate (inclusion rate: as needed)
2. Elimination of any other alkaline salts from the feed formulation, mainly magnesium oxide and sodium bicarbonate.
3. Use of a proper, not just cosmetic, dose of organic acid (inclusion rate: 0,7/1%) preferably benzoic acid, but potassium diformate has also been used successfully.
4. Obviously, the use of phytase to reduce the global need of mineral supplementation of the feed: if a phosphorus supply is still required, do not use bi- or tri-calcium phosphate, but preferably a monocalcium source.
The results are quite consistent, with an average increase of urine acidity equal to a 1,5 reduction in pH compared to the control diet, when the comparison is done on different sows fed the control diet or the “Low ph” feed, as well as when it is done testing the pH of the same sows, with the control day being day zero of administration of the “Low pH” feed and testing after 14/21 days of administration.
We have seen no negative effect on sows’ feed intake or on other zootechnical parameters during lactation, although we have noted a tendency of reduction of the wean to service interval in the treated sows: this very important fact, to be validated, would obviously need an extensive, controlled test.
We are currently investigating if (and up to which extent) it is possible to use raw CaCl2 instead of the microencapsulated form with no detrimental effect on feed intake, as this would greatly reduce the cost of the treatment.
Right now, we know that the lactating sow bladder is often subject to infections during lactation, and that in the majority of cases, E.coli is involved.
We also know that the same microorganism is frequently implicated in udder and uterine/vulvovaginal infections.
Finally, we also know that via this nutrition tool it is possible to significantly reduce the urinary pH of the sows, and make it difficult for the infection to continue ascending.
What we still do not know precisely is to what extent this extended level of urinary tract infections impacts a sow’s productivity: whatever the case may be, the fight against infections is one of the bases of biosecurity, and one of the minimal pre-requisites in the area of animal welfare preservation.
