Effect of urinary acidifier on reproduction performance in sows

Introduction
Urinary tract infections (UTI) and Postpartum Disgalactia Syndrome (PPDS) syndrome are among the most common health problems in sow herds. Both diseases are caused by bacterial infections and influence the fertility of the sow herd. From 17 to 40% of sows suffer from UTI, which consequentially leads to increased non-productive days, early cullings and decreased litters/sows/year (Saoulidis et al., 2000). The UTI include cystitis, inflammation of the urinary bladder, and pyelonephritis, ascendant inflammation into kidneys. Furthermore UTI are considered as predisposing factor for the upper genital tract inflammations (oviduct and uterus), which also lead to PPDS problems. The bacteria attach to the mucosa of urogenital tract by interactions between bacterial surface adhesions and complementary epithelial cell receptors, and stimulate cytokine release resulting in an inflammatory response and symptoms. However, the clinical signs of UTI are commonly overlooked in commercial farms or they are absent. Typically sows with significant bacteriuria are more often seen in the dog sitting position, have inferior body condition, longer weaning-to-service interval, low fertility rates and tend to wean small litters. Various health, environmental and management factors can contribute to UTI. For example, constipation, traumas to the urethra and bladder at parturition, assistance at farrowing, retained placenta or fluids, poor sanitized floor in farrowing crates, poor water quality, which leads to reduced water intake in sows, and ultimately reduced urination (Maes et al., 1998).

The flora of the vagina of healthy sows consists of a wide range of bacteria, including Streptococcus spp., Staphylococcus spp., Enterobacteria, Corynbacterium, Micrococcus spp. and Actinobacillus spp. Many of these bacteria especially E. coli, Actinobaculum suis, Pseudomonas aeruginosa, Klebsiella spp., Streptococcus faecalis, Streptococcus suis are frequently reported in clinical cases of urogenital tract infections. The highest isolation rates of these bacteria were obtained on the day of farrowing and the second highest number of positive samples was found immediately after mating. It is reported that parturition and a dietary change result in an upgrowth of E. coli and other bacteria in the reproductive tract of sows (MacLean and Thomas, 1974). The bacteria invasion is favored by acid-base unbalance in sows' diets, bringing out an increase of urine pH. Various studies have confirmed that acid-base balance (ACB) of the diet directly correlates with urinary pH value and total bacteria colony forming units in urine (Dee et al., 1994; DeRouchey et al., 2003). The ACB of conventional sows diets have a range of +200 to +600 mmol/kg feed, which makes the urine pH greater than 7. It is known that a urinary pH below 6.5 can significantly reduce the number of bacteria excreted with urine. The alkaline environment also inhibits the growth of competitive microflora and promotes the precipitation of the urinary salts and crystals. Such precipitates not only further increase inflammatory changes in the bladder mucosa but also provide a nidus for the bacterial growth and protection from antibiotics and host defense mechanisms.

Diets supplemented with urinary tract acidifier based on a combination of natural plant extracts, inorganic acids and anionic substances decreases the urinary pH via lowering the ACB of the diet by means of the anionic substances and inorganic acids. Moreover, due to the mode of action of inorganic acid and anionic substances Ca-mobilization mechanisms is triggered resulting in the higher Ca2+ availability in the blood. High Ca2+ amounts are necessary for the uterus muscle contraction at farrowing, preventing laborious, long lasting farrowing and saving healthy piglets from condemnation to death. Additionally it is known that the natural plant extracts containing proanthocanidins inhibit the adhesion of pathogenic bacteria, especially E. coli to urinary tract cell walls.

In the present study, the efficacy of the urinary tract acidifier on the decrease of urine pH and reproductive performance in sows was evaluated.

Materials and methods
A number of 48 sows were assigned to two different treatments. The control group received commercial gestation and lactation diets, whereas the trial group received the same gestation and lactation diets supplemented with 0.5 % of a blend of natural plant extracts, inorganic acids and anionic substances (Biomin^® pHD, BIOMIN, Austria) (PEx_InA_AS). The gestation diet was provided from d 108 of pregnancy until farrowing and then from d 1 weaning to d 1 mating, whereas the lactation feed from d 1 farrowing to d 1 weaning. On d 108 of gestation the sows (parities 3-4) were moved into farrowing facility and assigned to their treatments. The sows were penned individually within farrowing crates. The sows were allowed to access feed and water ad libitum. The conventional gestation and lactation diets were based on corn, soybean meal and rice bran, and they were formulated to contain 16.50 % crude protein.

The farrowing duration, intervals between litter mates, number of born alive, mummified, stillborn and condemned piglets, litter weight at birth and weaning were determined. The sows' urinary pH was measured at the beginning of the trial, d 108 and d 112 of pregnancy, at farrowing, d 14 and d 21 post-farrowing and d 1 after weaning and d 1 after insemination. All urine samples were collected in the morning between 7:00 and 8:00 before feeding. The urinary pH value was measured with pH-meter (Checker^® 1, Hanna Instruments) in samples taken from the mid stream urine.

Results and discussion
The lower urine pH is a natural barrier against the pathogens. A urinary pH below 6.5 can significantly reduces the number of bacteria excreted with urine. The urinary pH is a function of ACB of the diet, therefore it may vary depending on the composition of the diet and time ingested. Urine samples after a meal may have an alkaline pH. The electrolyte balance greater than 350 kEq/kg results in the respiratory and metabolic alkalosis and in an alkaline pH in the urine (pH > 7), thus increases the risk of UTI. The alkaline urine could be caused by certain bacteria, e.g. Staphylococcus, Proteus, producing urease, which metabolize the urea into ammonia and alkalize the urine. During these infections the urinary pH might reach values between 8 to 9, which leads to the further bacterial multiplication (Suzuki et al., 1979; Dee, 1992). The results of the present study showed that supplementation with the blend of PEx_InA_AS decreased the urinary pH ranging from 0.08 to 0.54 pH units during gestation and lactation periods (Table 1). It might be assumed that the dietary supplementation with the blend of PEx_InA_AS decreased the ACB of the diet consequentially reducing the urine pH. The highest decrease in pH was on d 112 of gestation, following d 1 post-artificial insemination (AI) and d 14 post-farrowing. The results of the present study are in good agreement with other studies, where decrease in ACB of the diet led to reduction of the urinary pH (DeRouchey et al., 2003). The reduction of urinary pH at farrowing and mating is crucial, because during that time the cervix is opened, therefore the sows are more susceptible to infections. Moreover, the reduced counts of pathogenic bacteria in urogenital tract lead to healthier farrowing crates and benefit newborn piglets ultimately encountering lower counts of Streptococcus suis, E. coli after birth and before suckling the colostrum. Additionally the plant extracts have reduced the risk of bacterial infection preventing the bacterial adhesion to the urinary tract walls. For example, the adherence of E. coli is a critical step in the pathogenesis of UTI. The bacteria been found to have specific binding sites which can attach the specific receptors on urothelial cells of urinary tract wall. It is well known that, cranberry extracts contain high amounts of proanthocanidins, which prevent the attachment of E. coli to the urinary tract wall by occupying the specific binding cites for the uroepithelial cells in bacteria (Foo et al., 2000).

Table 1. Efficacy of the bled of of natural plant extracts, inorganic acids and anionic substances on sows urine pH reduction.

Collection Time	Control Group ¹	Trial Group ²	Δ
No of sows	n = 24	n = 24
108 d gestation	6.29	6.17	0.12
112 d gestation	6.42	5.88	0.54
1 d post-farrowing	6.04	5.96	0.08
14 d post-farrowing	7.61	7.35	0.26
21 d post-farrowing	7.48	7.57	0.09
1 d post-weaning	7.15	7.10	0.05
1 d post-AI³	7.35	6.94	0.41

¹ Control group = no blend of natural plant extracts, inorganic acids and anionic substances
² Trial group = with blend of natural plant extracts, inorganic acids and anionic substances
³ AI = artificial insemination

In the present study the duration of the farrowing time between the first and the last piglet was shortened by 37.16 min and the interval between the littermates was reduced by 7.87 min (P<0.10) in the group supplemented with the blend of PEx_InA_AS compared to those in the control group (Table 2). Due to supplementation of the blend PEx_InA_AS the reproduction performance of sows in the trial group was improved. In the trial group the total number and born alive were increased by 8.4 and 16.2 percentage units, respectively, whereas the number of the stillborn decreased by 26.1 percentage units compared to the control group. The shorter farrowing period and the reduction of the stillborn number are related to the activation of the Ca-mobilization mechanism, which is triggered by supplementation with the inorganic and anionic substances.

The blend of PEx_InA_AS through the light acidification of the blood stimulates the parathyroid gland to release parathyroid hormone, which attempts to rebalance blood pH value 7.4. Parathyroid hormone is deputed to control Ca2+ levels, leading to enhanced Ca2+ absorption from gut lumen and its mobilization from the bones, a decrease phosphate re-adsorption in the kidneys, and less Ca2+ excretion through kidneys. Ca-mobilization into blood stream is important for the uterus muscle contraction. It is known that hypocalcemia decreases the strength of uterine contractions and contribute to a prolonged farrowing, thus predisposing higher number of stillborns and lactation failure (Cline and Richert, 2001).The lack of Ca2+ at farrowing results in laborious farrowing and economic losses due to higher number of fully developed piglets born dead. The stillborns are frequent in sow units, favored mainly by low motility during gestation, stress and constipation.

Table 2. Efficacy of the bled of of natural plant extracts, inorganic acids and anionic substances on farrowing duration and reproduction performance.

Collection Time	Control Group ¹	Trial Group ²	Δ
No of sows	n = 24	n = 24
1st-last piglet, min	191.33	154.17	37.16
Interval between littermates, min	22.00 ^A	14.13 ^B	7.87
Litter size at birth Total Born alive Mummified Stillborn Condemned	9.92 8.50 1.70 1.80 2.00	10.75 9.88 2.50 1.33 1.00	0.83 1.38 0.80 0.47 1.00
Litter weight at birth, kg	11.91	12.92	1.01
Litter size at weaning	7.33 ^A	9.08 ^B	1.75
Survival at weaning, %	85.00 ^A	92.29 ^B	7.29
Litter weight at weaning, kg	54.22	65.29	11.07

¹ Control group = no blend of natural plant extracts, inorganic acids and anionic substances
² Trial group = with blend of natural plant extracts, inorganic acids and anionic substances
^{A, B} Different superscript between groups differed at P<0.10

Moreover, in the trial group litter weight at birth and at weaning were increased by 8.4 and 20.4 percentage units, respectively, compared to the control group. The higher litter size at weaning and survival rate in the group supplemented with the blend of PEx_InA_AS was improved (P<0.10), which is in good agreement with other studies (Saoulidis et al., 2000; DeRouchey et al. 2003). In the trial group the higher litter size and survival rates at weaning could be related to the higher amount of Ca2+ in the blood stream, which is essential for the lactogenesis (Miller et al., 1994). It is known that the high piglet mortality is associated with low milk production during the first days after the farrowing, because the glycogen stores decrease rapidly 12 to 18 h. Thus improvement of milk yield and milk composition during the 1st week of lactation improved vigor and survivability of piglets.

Conclusions
The dietary supplementation with the blend of natural plant extracts, inorganic acids and anionic substances in the diets improved the farrowing and reproduction performance of sows. This blend could be considered as efficient in promoting a more efficient farrowing process, guaranteeing presence of Ca2+ in blood, preventing partly stillborn animals, and rebounding positive effects along lactation. Moreover, the acidification of urine concomitant with good farm management practice can be a preventive measure that minimizes or eliminate the risk factor for occurrence the urogenital tract infections and PPDS.

References
Cline T.R. and Richert B.T. 2001. Feeding growing-finishing pigs. In Swine Nutrition (ed. A.J. Lewis, L.L Southern). pp. 717-724.

Dee S.A. 1992. Porcine urogenital disease. The Veterinary Clinics of North America Food animal Practice 8:641-660.

Dee S.A., Tracy J.D. and King V. 1994. Using citric acid to control urinary tract disease in swine. Veterinary Medicine 89:473-476.

DeRouchey J.M., Hancock J.D., Hines R.H., Cummings K.R., Lee D.J., Maloney C.A., Dean D.W., Park J.S. and Cao H. 2003. Effects of dietary electrolyte balance on the chemistry of blood and urine in lactating sows and sows litter performance. Journal of Animal Science 81:3067-3074.

Foo Y.L., Lu Y., Honwell A.B. and Vorsa N. 2000. A-typer proanthocyanidin trimers from cranberry that inhibit adherence of uropathogenic P-fimbriated Escherichia coli. Journal of Natural Products 63: 1225-1228.

MacLean C.W. and Thomas N.D. 1974. Faecal and vaginal bacteriology of sows during the reproductive cycle. British Veterinary Journal 130:230-237.

Maes D., Verdonck M. and de Kruif A. 1998. Vaginal microecology and vulval discharge in swine. In Vaginal Flora in Health and Disease (ed. P. Heidt, P.B. Carter, V.D. Rusch, D. van der Waaij). pp. 39-48.

Miller M.B., Hartsock T.G., Erez B., Douglass L. and Alston-Mills B. 1994. Effect of dietary calcium concentrations during gestation and lactation in the sow on milk composition and litter growth. Journal of Animal Science 72:1315-1319.

Saoulidis K., Kritas S.K., Sarris K., Roubies N. and Kyriakis S.C. 2000. Case report of urinary tract infection in sows of a commercial pig unit. Journal of Hellenic Veterinary Medical Society 51:272-276.

Suzuki K., Benno Y., Mitsuoka T., Takebe S., Kobashi K. and Hase J. 1979. Urease-producing species of intestinal anaerobes and their activities. Applied and Environmental Microbiology 37:379-382.