Effect of in-water iodine supplementation on weight gain, diarrhea and oral and dental health of nursery pigs
Introduction
Environmental contamination by pathogenic bacteria is an ongoing concern in the pork industry. During the period immediately after weaning, piglets are introduced to numerous stresses, which make them particularly susceptible to enteric disease such as Escherichia coli diarrhea. It is important to minimize disease challenge during this period in order to reduce digestive disorders and maintain growth (1). Consequently, most producers strive to eliminate environmental pathogens by operating nursery rooms on an all-in/ all-out basis, with thorough cleaning and disinfection of the facilities between batches. However, bacterial challenges continue during the weeks following weaning and therefore, continued disinfection may be beneficial. A clean source of water is an essential element in this process and is important for maintaining good health and growth in young pigs.
Iodine is an affordable and widely available compound for treating water. It provides broad-spectrum antiseptic activity and has proven effective against antibiotic-resistant bacteria (2). It also shows low potential for bacterial resistance after both short- and long-term exposure (3). In addition to reducing environmental pathogens, iodine has been shown to be a powerful oral antiseptic (4,5) and may therefore be effective in preventing the development of deleterious oral conditions. One advantage of treating water rather than feed in the post-weaning period is that piglets will often go through a period of anorexia, during which feed intake is low or non-existent but water intake and water utilization are high (6,7).
The purpose of this study was to evaluate the effect of in-water iodine on piglet growth, the incidence of diarrhea, and the development of deleterious oral conditions. We predicted that piglets receiving the sanitizing treatment would have improved growth, lower incidence of diarrhea, and better oral conditions than those piglets not receiving the treatment.
Materials and methods
Herd
A research trial was conducted from February to April 2009 on a commercial farrow-to-feeder swine farm located in southwestern Ontario. The herd consisted of approximately 600 sows with maternal genetics being a cross of Yorkshire and Landrace and sire genetics originating from the Duroc line. The farm was on an antibiotic-free program and no antibiotics were used therapeutically or added to feed. The herd was positive for porcine reproductive and respiratory syndrome (PRRS) virus, but clinical expression of the disease was absent in the nursery. Likewise, post-weaning E. coli diarrhea had been reported by the producer as occurring sporadically between weaning batches over the previous 6 mo.
Animals
A total of 208 piglets from 38 litters was examined across 3 weaning cohorts. Piglets had their 4 erupted needle teeth (i, i3, c, c1) clipped within 24 h of birth (see Figure 1), and were processed (tail-docked, injected with iron, boars castrated) before 7 d of age. Piglets remained with their mothers in standard farrowing crates until the day before weaning when individual ear tags were attached. Across the 3 cohorts, weaning age ranged from 17 to 27 d. The following day, half the piglets in each litter were randomly assigned to the iodine treatment and half to the control treatment. They were then moved to 1 of 3 on-site nursery rooms (1 room/weaning cohort), which were operated on an all-in/all-out basis and washed and disinfected before being used. Each room contained 8 pens (4 control pens and 4 treatment pens), housing from 25 to 30 piglets each. Pens were balanced as much as possible based on litter origin, gender, and weaning weight. For convenience, all 4 pens receiving the iodine treatment were located on the same side of each room. Natural lighting was provided and air temperature was maintained at 23°C to 25°C. A corn- and soybean-based nursery diet fortified with a vitamin and mineral premix (Natures Blend; Grand Valley Fortifiers, Cambridge, Ontario) was provided ad libitum to each pen in 2, 4-hole stainless steel feeders. Piglets were weighed 3 times: within 24 h of weaning, and 3 wk and 6 wk after weaning. All procedures were approved by the University of Guelph Animal Care Committee in accordance with the Canadian Council on Animal Care.
Iodine supplementation
Water was provided ad libitum to piglets in bowl drinkers (2 drinkers/pen) (Egebjerg Drik-O-Mat weaner bowl drinker, No. 93.569; Bosman Agri, Moorefield, Ontario). An iodine-based sanitizer containing 1.75% titratable iodine (Premise Aqua; West Penetone, Montreal, Quebec) was premixed with water at a 1% concentration in a 20-L container before being pumped into the water system by a H5NN Fixed Rate Chemilizer Injector pump (Chemilizer Products, Largo, Florida, USA), giving a final concentration of 1 ppm iodine. The 20-L container was refilled as necessary throughout each trial. Iodine testing was performed at the drinkers on days 1, 2, 4, 8, and 12 post-weaning in the 1st cohort, d 2, 5, 18, and 25 post-weaning in the 2nd cohort, and days 3, 4, 5, 11, and 18 in the 3rd cohort, with a Taylor Iodine Test (Kit # K-1267, Lot # 2040A; Taylor Technologies, Sparks, Maryland, USA). Concentrations of iodine averaged 0.96, 0.68, and 0.91 ppm in cohorts 1, 2, and 3, respectively. During trial 2, concentrations of iodine were lower than desired due to a technical problem that caused excessive waterline flushing and dilution of the premixed iodine solution.
Bacterial isolates
Swabs (BD BBL CultureSwab; Becton Dickinson and Company, Sparks, Maryland, USA) were taken from all water nipples and water lines 3 times during the trial: before piglets were introduced to the nursery pens, 3 wk after weaning, and at the end of the trial. Fecal samples (5 to 7 samples/pen) were collected from all pen floors at the same time as water nipples and water lines were swabbed. Fecal samples were pooled for each pen and chosen based on apparent freshness. In addition, fecal samples were collected from all sows at weaning.
The swabs and fecal samples were tested for the presence of Salmonella according to the MFLP-34 protocol of the Laboratory Service Division at the University of Guelph. For fecal samples, the MFLP-34 procedure required a 10% fecal suspension in 0.85% saline, with subsequent 1 mL transfer to 10 mL of pre-warmed (35°C) buffered peptone water (BPW). Swabs were transferred to a sterile stomacher bag containing 100 mL of BPW and homogenized in a stomacher unit for 2 min. Both pre-enriched mixtures were incubated at 35°C for 18 to 24 h. For both samples, a 500-μL culture was removed and reacted with 10 μL of anti-Salmonella Dynabeads (DYNAL AS, Oslo, Norway), which were pre-washed in 500 μL of phosphate-buffered saline containing 0.01% Tween 20 (PBST). The inoculated samples were concentrated using an automated immuno-magnetic separator (IMS) (DYNAL AS) and transferred into 10 mL of Rappaport Vassilliadis Soya peptone broth (RVS). The samples were incubated at 42°C for 18 to 24 h and subsequently looped onto bismuth sulfite (BS) and brilliant green sulfapyridine (BGS) plating media. Agar plates were then incubated at 35°C for 18 to 24 h. Confirmation of Salmonella isolates was carried out by serotyping at the Laboratory for Foodborne Zoonoses in Guelph, Ontario.
The swabs were additionally tested for E. coli according to the Petrifilm E. coli-Coliform Count Plate Method (MFHPB-34). Swabs were transferred to a sterile stomacher bag containing 10 mL of 0.85% saline solution and homogenized in a stomacher unit for 2 min. A 1-mL sample was then pipetted onto the center gel patch of the bottom film (Petrifilm Plate; 3M, London, Ontario). The top film was placed over the sample and a spreader was used to evenly disperse the inoculum. The film was then left to react for at least 1 min before being incubated at 35°C for 48 h. Escherichia coli colonies were then counted manually from the film plates and the isolates were submitted to Gallant Custom Laboratory in Cambridge, Ontario for serotyping.
Dental and oral condition
In the first weaning cohort, 6 piglets from each pen were chosen for oral examinations and in subsequent cohorts, 10 piglets were examined from each pen (N = 208). Piglets were initially selected if they did not show any evidence of a previous or current health problem, for example, they did not require surgical castration or hernia repair and had no arthritic joint swelling, and were in a good weight category for their size.
Within 24 h of being weighed (at weaning and 3 wk and 6 wk after weaning), a complete oral examination was performed on each piglet with all deciduous teeth in each dental arch (right and left maxilla, right and left mandible) being recorded as erupted or not (Figure 1). Eruption was considered to have occurred when any portion of the tooth crown had penetrated the gingiva (8). Dental nomenclature follows that of Tucker and Widowski (9) whereby all deciduous incisors, canines, and premolars are referred to by a lowercase i, c, or p. A superscript or subscript number follows each tooth to indicate its position within the maxilla or mandible, respectively. For example, p is the 3rd maxillary premolar, whereas p4 is the 4th mandibular premolar.
In addition to tooth eruption, 3 different dental or oral conditions were scored as being present or not: (1) dental staining or dental caries (cavities) on the i, (2) gingivitis around any teeth, and (3) oral lesions on the gingiva, tongue, cheeks, or throat.
Statistical analyses
All data were entered into an Excel 2000 spreadsheet (Microsoft, Redmond, Washington, USA) and then imported into SAS (Version 9.13; SAS Institute, Cary, North Carolina, USA). PROC UNIVARIATE was used to examine data for normality and comprehensive residual analyses were conducted to assess the analysis of variance (ANOVA) assumptions. Residuals were plotted against explanatory variables and predicted values in order to check for equality of variance and outliers. Outliers not evenly distributed between treatment and control groups were removed. A repeated measures analysis of covariance (PROC MIXED) was used to assess the association between weight gain and iodine treatment. Covariates included in the model were piglet gender, weaning weight, weaning age, and number of live-born piglets per litter. Weaning cohort (or trial), litter origin, and pen number were accounted in the RANDOM statement.
For treatment differences in those oral conditions that were present at all 3 observation periods (dental staining or caries, and oral lesions), a repeated measures analysis of covariance was used (PROC GLIMMIX). For treatment differences in gingivitis, which was only seen at the last observation period, a non-repeated analysis of covariance was used in favor of a repeated measures analysis (PROC GLIMMIX). The binary distribution was best suited for those analyses examining dental conditions. Piglet gender, weight, weaning age, and number of live-born piglets per litter were used as covariates.
Pair-wise differences between treatment means in all models were assessed using t-tests. Associations were reported as statistically significant if P < 0.05.
Herd
A research trial was conducted from February to April 2009 on a commercial farrow-to-feeder swine farm located in southwestern Ontario. The herd consisted of approximately 600 sows with maternal genetics being a cross of Yorkshire and Landrace and sire genetics originating from the Duroc line. The farm was on an antibiotic-free program and no antibiotics were used therapeutically or added to feed. The herd was positive for porcine reproductive and respiratory syndrome (PRRS) virus, but clinical expression of the disease was absent in the nursery. Likewise, post-weaning E. coli diarrhea had been reported by the producer as occurring sporadically between weaning batches over the previous 6 mo.
Animals
A total of 208 piglets from 38 litters was examined across 3 weaning cohorts. Piglets had their 4 erupted needle teeth (i, i3, c, c1) clipped within 24 h of birth (see Figure 1), and were processed (tail-docked, injected with iron, boars castrated) before 7 d of age. Piglets remained with their mothers in standard farrowing crates until the day before weaning when individual ear tags were attached. Across the 3 cohorts, weaning age ranged from 17 to 27 d. The following day, half the piglets in each litter were randomly assigned to the iodine treatment and half to the control treatment. They were then moved to 1 of 3 on-site nursery rooms (1 room/weaning cohort), which were operated on an all-in/all-out basis and washed and disinfected before being used. Each room contained 8 pens (4 control pens and 4 treatment pens), housing from 25 to 30 piglets each. Pens were balanced as much as possible based on litter origin, gender, and weaning weight. For convenience, all 4 pens receiving the iodine treatment were located on the same side of each room. Natural lighting was provided and air temperature was maintained at 23°C to 25°C. A corn- and soybean-based nursery diet fortified with a vitamin and mineral premix (Natures Blend; Grand Valley Fortifiers, Cambridge, Ontario) was provided ad libitum to each pen in 2, 4-hole stainless steel feeders. Piglets were weighed 3 times: within 24 h of weaning, and 3 wk and 6 wk after weaning. All procedures were approved by the University of Guelph Animal Care Committee in accordance with the Canadian Council on Animal Care.
Iodine supplementation
Water was provided ad libitum to piglets in bowl drinkers (2 drinkers/pen) (Egebjerg Drik-O-Mat weaner bowl drinker, No. 93.569; Bosman Agri, Moorefield, Ontario). An iodine-based sanitizer containing 1.75% titratable iodine (Premise Aqua; West Penetone, Montreal, Quebec) was premixed with water at a 1% concentration in a 20-L container before being pumped into the water system by a H5NN Fixed Rate Chemilizer Injector pump (Chemilizer Products, Largo, Florida, USA), giving a final concentration of 1 ppm iodine. The 20-L container was refilled as necessary throughout each trial. Iodine testing was performed at the drinkers on days 1, 2, 4, 8, and 12 post-weaning in the 1st cohort, d 2, 5, 18, and 25 post-weaning in the 2nd cohort, and days 3, 4, 5, 11, and 18 in the 3rd cohort, with a Taylor Iodine Test (Kit # K-1267, Lot # 2040A; Taylor Technologies, Sparks, Maryland, USA). Concentrations of iodine averaged 0.96, 0.68, and 0.91 ppm in cohorts 1, 2, and 3, respectively. During trial 2, concentrations of iodine were lower than desired due to a technical problem that caused excessive waterline flushing and dilution of the premixed iodine solution.
Bacterial isolates
Swabs (BD BBL CultureSwab; Becton Dickinson and Company, Sparks, Maryland, USA) were taken from all water nipples and water lines 3 times during the trial: before piglets were introduced to the nursery pens, 3 wk after weaning, and at the end of the trial. Fecal samples (5 to 7 samples/pen) were collected from all pen floors at the same time as water nipples and water lines were swabbed. Fecal samples were pooled for each pen and chosen based on apparent freshness. In addition, fecal samples were collected from all sows at weaning.
The swabs and fecal samples were tested for the presence of Salmonella according to the MFLP-34 protocol of the Laboratory Service Division at the University of Guelph. For fecal samples, the MFLP-34 procedure required a 10% fecal suspension in 0.85% saline, with subsequent 1 mL transfer to 10 mL of pre-warmed (35°C) buffered peptone water (BPW). Swabs were transferred to a sterile stomacher bag containing 100 mL of BPW and homogenized in a stomacher unit for 2 min. Both pre-enriched mixtures were incubated at 35°C for 18 to 24 h. For both samples, a 500-μL culture was removed and reacted with 10 μL of anti-Salmonella Dynabeads (DYNAL AS, Oslo, Norway), which were pre-washed in 500 μL of phosphate-buffered saline containing 0.01% Tween 20 (PBST). The inoculated samples were concentrated using an automated immuno-magnetic separator (IMS) (DYNAL AS) and transferred into 10 mL of Rappaport Vassilliadis Soya peptone broth (RVS). The samples were incubated at 42°C for 18 to 24 h and subsequently looped onto bismuth sulfite (BS) and brilliant green sulfapyridine (BGS) plating media. Agar plates were then incubated at 35°C for 18 to 24 h. Confirmation of Salmonella isolates was carried out by serotyping at the Laboratory for Foodborne Zoonoses in Guelph, Ontario.
The swabs were additionally tested for E. coli according to the Petrifilm E. coli-Coliform Count Plate Method (MFHPB-34). Swabs were transferred to a sterile stomacher bag containing 10 mL of 0.85% saline solution and homogenized in a stomacher unit for 2 min. A 1-mL sample was then pipetted onto the center gel patch of the bottom film (Petrifilm Plate; 3M, London, Ontario). The top film was placed over the sample and a spreader was used to evenly disperse the inoculum. The film was then left to react for at least 1 min before being incubated at 35°C for 48 h. Escherichia coli colonies were then counted manually from the film plates and the isolates were submitted to Gallant Custom Laboratory in Cambridge, Ontario for serotyping.
Dental and oral condition
In the first weaning cohort, 6 piglets from each pen were chosen for oral examinations and in subsequent cohorts, 10 piglets were examined from each pen (N = 208). Piglets were initially selected if they did not show any evidence of a previous or current health problem, for example, they did not require surgical castration or hernia repair and had no arthritic joint swelling, and were in a good weight category for their size.
Within 24 h of being weighed (at weaning and 3 wk and 6 wk after weaning), a complete oral examination was performed on each piglet with all deciduous teeth in each dental arch (right and left maxilla, right and left mandible) being recorded as erupted or not (Figure 1). Eruption was considered to have occurred when any portion of the tooth crown had penetrated the gingiva (8). Dental nomenclature follows that of Tucker and Widowski (9) whereby all deciduous incisors, canines, and premolars are referred to by a lowercase i, c, or p. A superscript or subscript number follows each tooth to indicate its position within the maxilla or mandible, respectively. For example, p is the 3rd maxillary premolar, whereas p4 is the 4th mandibular premolar.
In addition to tooth eruption, 3 different dental or oral conditions were scored as being present or not: (1) dental staining or dental caries (cavities) on the i, (2) gingivitis around any teeth, and (3) oral lesions on the gingiva, tongue, cheeks, or throat.
Statistical analyses
All data were entered into an Excel 2000 spreadsheet (Microsoft, Redmond, Washington, USA) and then imported into SAS (Version 9.13; SAS Institute, Cary, North Carolina, USA). PROC UNIVARIATE was used to examine data for normality and comprehensive residual analyses were conducted to assess the analysis of variance (ANOVA) assumptions. Residuals were plotted against explanatory variables and predicted values in order to check for equality of variance and outliers. Outliers not evenly distributed between treatment and control groups were removed. A repeated measures analysis of covariance (PROC MIXED) was used to assess the association between weight gain and iodine treatment. Covariates included in the model were piglet gender, weaning weight, weaning age, and number of live-born piglets per litter. Weaning cohort (or trial), litter origin, and pen number were accounted in the RANDOM statement.
For treatment differences in those oral conditions that were present at all 3 observation periods (dental staining or caries, and oral lesions), a repeated measures analysis of covariance was used (PROC GLIMMIX). For treatment differences in gingivitis, which was only seen at the last observation period, a non-repeated analysis of covariance was used in favor of a repeated measures analysis (PROC GLIMMIX). The binary distribution was best suited for those analyses examining dental conditions. Piglet gender, weight, weaning age, and number of live-born piglets per litter were used as covariates.
Pair-wise differences between treatment means in all models were assessed using t-tests. Associations were reported as statistically significant if P < 0.05.
Results
The treatment differences for piglet, sow, and litter variables are shown in Table I. Weaning age ranged from 17 to 27 d and weaning weights ranged from 2.2 to 9.9 kg. A wide range of parities (1 to 16), live litter size (3 to 18), and stillbirths per litter (0 to 7) were represented within the study population.
Table I
Mean (± SEM) production parameters by treatment group (control versus iodine) for 208 piglets
| Control | Iodine | ||||
|---|---|---|---|---|---|
| Variable | Mean | SEM | Mean | SEM | P-value |
| Piglet level | |||||
| Weaning age (d) | 21.65 | 0.24 | 21.83 | 0.24 | 0.60 |
| Weaning weight (kg) | 5.28 | 0.14 | 5.32 | 0.14 | 0.87 |
| Weight at 3 wk (kg) | 10.18 | 0.22 | 10.17 | 0.24 | 0.98 |
| Weight at 6 wk (kg) | 19.37 | 0.36 | 19.14 | 0.37 | 0.87 |
| ADG (kg/d) from wk 1 to 3b | 0.228 | 0.004 | 0.226 | 0.004 | 0.74 |
| ADG (kg/d) from wk 3 to 6b | 0.438 | 0.006 | 0.443 | 0.006 | 0.58 |
| Sow level | |||||
| Parity | 6.63 | 0.38 | 6.44 | 0.35 | 0.73 |
| Litter level | |||||
| Number of live-born piglets | 11.26 | 0.36 | 11.49 | 0.32 | 0.63 |
| Number of stillbirths | 2.23 | 0.14 | 2.21 | 0.13 | 0.89 |
SEM — Standard error of the mean.
The cumulative percentage of piglets with erupted deciduous teeth is shown in Table II and the time by treatment differences for the 3 dental conditions examined is shown in Table III. The presence of dental staining and dental caries on the i significantly increased during the time from weaning to the next exam period 3 wk later. Oral lesions increased successively through each exam period, while gingivitis increased between week 3 and week 6 only.
Table II
Cumulative percentage of piglets with erupted deciduous teeth (N = 208)
| Deciduous tooth | Dental examination period | ||
|---|---|---|---|
| Weaning | 3 wk after weaning | 6 wk after weaning | |
| i2 | 0.0 | 1.0 | 26.0 |
| i2 | 0.0 | 29.0 | 96.0 |
| p2 | 0.0 | 0.5 | 8.2 |
| p3 | 99.6 | 100.0 | 100.0 |
| p3 | 74.4 | 100.0 | 100.0 |
| p4 | 38.3 | 100.0 | 100.0 |
| p4 | 100.0 | 100.0 | 100.0 |
Table III
Cumulative percentage of piglets in each treatment (control versus iodine) with various oral or dental conditions
| Oral/dental characteristic | Control | Iodine | ||||
|---|---|---|---|---|---|---|
| Weaning | Week 3 | Week 6 | Weaning | Week 3 | Week 6 | |
| Stains or caries on i1 | 29.0b | 38.5c | 40.2c | 24.3b | 31.1c | 34.8c |
| Oral lesions | 6.5a | 45.2b | 59.6c | 9.3a | 37.5b | 54.8c |
| Gingivitis | 0b | 0b | 13.5c | 0b | 1.0b | 9.6c |
No significant difference was found in growth (P > 0.05) or dental conditions (P > 0.05) among treatment groups during the period that iodine was added to the drinking water. Of the 3 deleterious oral conditions examined, only the presence of gingivitis was shown to be associated with weight, as affected piglets were lighter (P < 0.05). The mean weight for individuals displaying gingivitis 6 wk after weaning was 16.05 ± 1.44 kg, while unaffected piglets weighed 17.30 ± 1.38 kg.
In total, 72 fecal samples were collected from the nursery rooms and 38 from sows. Salmonella was cultured only twice from fecal samples: Salmonella Livingstone from the control pigs and Salmonella Agona from treated pigs. Only 1 sow tested positive for Salmonella and this isolate was serotyped as Salmonella Agona. No Salmonella was recovered from the 72 swabs that were collected from water nipples. E. coli tended to be cultured only rarely from the water nipples, with 14% of swabs (5 out of 36) positive in the control group and 19.4% (7 out of 36) positive in the treatment group. The E. coli strains were serotype O139: K82, O157:K”V17”, or cross-reacted with several different enterotoxigenic Escherichia coli (ETEC) typing sera. There were no incidences of diarrhea noted throughout the study.
Discussion
The purpose of this study was to determine the on-farm effect of an aqueous iodine supplement on weight gain, oral condition, and the incidence of post-weaning diarrhea in newly weaned piglets. The underlying principle was that iodine would exert a biocidal effect on the oral and gastrointestinal bacterial load and reduce their growth-inhibiting properties. Bacteria can reduce optimal growth in piglets in a number of ways, such as through the development of sub-clinical or realized infections, the production of growth-depressant metabolites, or by competing for essential nutrients that are required for tissue maintenance (10).
However, analysis did not indicate any differences between trials for any measured parameters. Contrary to our first prediction, no significant differences were seen in the weight gain of piglets that had iodine supplemented in their drinking water compared to those without it. There could be several reasons for this result, including the possibility that an insufficient concentration of iodine was added to the drinking supply, insufficient time was allowed for bacterial contact, a true inability for iodine to affect bacterial load occurred, or there was an overall insufficient bacterial load present in the base water supply to reduce weight gain for even the control group of piglets.
Iodine, similar to other oxidizing halogens, such as chloride and fluorine, is a well-recognized disinfectant that is widely used by humans worldwide. In fact, it provides several advantages over both chlorine and fluorine in that it has lower reactivity to nitrogenous contaminants, is safer over a wider range of concentrations, has a higher palatability (by human standards), and is more stable in both storage and aqueous suspension (11,12). A number of conditions preclude its effectiveness for use in a water supply, however, including: 1) prior chlorination, 2) high alkalinity, and 3) a high concentration of organic matter in the water. Consequently, producers must first determine the suitability of iodine based on the specific water conditions at the farm.
The water in the current study was unchlorinated and supplied from a deep, cold spring well, thus satisfying the first prerequisite. Alkalinity values obtained from the water sources supplying the well were also stable over the period that the experiment was conducted and ranged from 7.4 to 7.6. The water delivery system itself used bowl drinkers, however, that allowed water to pool and interact with organic matter in between drinking bouts of pigs in the pen. This factor may have impeded the effectiveness of iodine as a disinfectant. Further studies should consider using nipple-style drinkers to prevent any possible contamination of the water.
Other factors that determine the level of disinfection achieved by iodine are its concentration within the aqueous solution, the time in contact with microorganisms, and the temperature of the solution (13,14). The recommended doses for water disinfection for human consumption range from 0.2 to 16 ppm depending on the method of treatment (tablet, solution, resin filter) (15). The average iodine concentration during the 2nd weaning cohort, however, was only maintained at approximately 70% of the desired 1 ppm. As water temperature increases, increased concentrations of iodine are required. For example, using a resin filter at room temperature achieves acceptable disinfection at 0.2 ppm, but this must be increased to 6 to 10 ppm if temperatures reach 71°C (15). As this study was conducted throughout the early spring and the water supply was pumped from an underground well to the weaning room, the water temperature was colder than room temperature. Water also sat in the plastic water lines after being mixed to 1 ppm, however, and therefore may have been heated to room temperature (~23°C to 25°C). Given that piglets require increasing amounts of water due to their fast rate of growth, however, there would be less time available for the mixed solution to sit at room temperature.
It is possible that adding iodine to drinking water may support improved growth rate on farms where disease challenge is much greater and where contaminated water plays a role in increased incidence of enteric disease.
To our surprise, there were no cases of post-weaning diarrhea in either the treated or control groups of nursery pigs. The prevalence of E. coli isolated from the water nipples was quite low, which suggests that the water supply was relatively clean and safe. The shedding of Salmonella was very low and the presence of diarrhea due to E. coli was not identified as a problem during the study. Overall, there were few signs of enteric disease in either treatment or control pigs.
With regard to oral and dental condition, this is the first study, to the authors’ knowledge, in which the progression of deleterious conditions has been examined in domestic piglets. As oral disease in humans is linked to severe systemic conditions such as cardiovascular disease (16), bacterial pneumonia (17), diabetes mellitus (18), and compromised or failed pregnancies (19), a reduction in oral bacteria may prove beneficial to the overall health and longevity of the herd. Given that gingival inflammation and bleeding have been reported in weaned piglets as a result of both deciduous tooth eruption and earlier teeth clipping (9,20), it was thought that sanitization of the drinking supply may prove beneficial for reducing oral pathogens and preventing the development of oral disease.
Overall, the presence of staining and caries on the primary incisors increased between weaning and week 3 in the current study, while the incidence of gingivitis increased between week 3 and week 6. Oral lesions increased throughout the entire 6-week study period. Nevertheless, there were no treatment differences resulting from the supplementation of iodine for any of these oral conditions.
The fact that oral lesions were found to affect such a high percentage of piglets by the last examination period (over 50% of individuals in both treatment groups) may reflect the fact that pigs are highly motivated to investigate and manipulate objects orally. As most equipment, such as feeders and drinkers, as well as penning materials, are made of steel or durable hard plastics, it is quite possible that they could cause abrasions within the mouth when manipulated, particularly if there are broken or jagged edges. For the newly weaned piglets, it was noted that most of the oral lesions appeared to be related to tooth clipping, with the surrounding gin-giva and soft tissues being affected by fragments of broken teeth. These lacerations were often still present by week 3 and week 6, indicating the persistence of such injuries.
The fact that gingivitis was seen in piglets only at wk 6 after weaning (excluding 1 individual who had the condition at week 3) may reflect the progressive nature of the disease. Gingivitis is inflammation of the gingival tissues caused by the accumulation of bacterial plaque on the surface of the teeth. It is not known whether or not the majority of individuals would eventually develop this condition or only those individuals with a predisposition to the condition. That pigs displaying gingivitis weighed less than their pen-mates who were unaffected may indicate a state of increased immune challenge and subsequent growth depression, or it may simply mean that smaller pigs are predisposed to this type of dental disease.
In conclusion, these results indicate that deleterious oral conditions do develop and increase throughout the weaning period, with gingivitis being negatively associated with piglet weight. Adding an aqueous iodine supplement of 0.68 to 0.99 ppm to nursery piglets, however, does not provide an advantage for either growth or oral condition.
Abstract
A farm trial was conducted to evaluate the effect of in-water iodine on piglet growth, the incidence of diarrhea, and the development of deleterious oral and dental conditions. A total of 208 weaned piglets were included in the study. Piglets were weighed 3 times: within 24 h of weaning, and 3 wk and 6 wk after weaning. A concentration of 1 ppm iodine was provided in their drinking water. Swabs were taken from all water nipples and water lines and pooled fecal samples were collected from all pen floors. Fecal samples were also collected from sows at weaning. The swabs and fecal samples were tested for the presence of Salmonella and Escherichia coli. Within 24 h of each weighing, a complete oral examination was performed on each piglet. No significant difference in growth (P > 0.05) or dental conditions (P > 0.05) was found among treatment groups during the period that iodine was added to the drinking water. After weaning, all deleterious oral conditions increased (oral lesions from weaning to 6 wk, staining and caries from weaning to 3 wk, gingivitis from 3 wk to 6 wk; P < 0.05). Only gingivitis was found to be negatively associated with piglet weight (P < 0.05). Salmonella was cultured only twice from fecal samples and never from water nipples. Only 1 sow tested positive for Salmonella and E. coli O139: K82 and O157:K”V17 were cultured only rarely from the water nipples. No signs of diarrhea were noted throughout the study. Adding an aqueous iodine supplement to nursery pigs, therefore, did not provide an advantage for either growth or oral condition. Deleterious oral conditions do increase after weaning, with gingivitis being associated with lower piglet weight.
Résumé
Un essai à la ferme a été réalisé afin d’évaluer l’effet de l’ajout d’iode dans l’eau sur la croissance des porcelets, l’incidence de diarrhée, et le développement de conditions orales et dentaires délétères. Au total, 208 porcelets sevrés ont été inclus dans l’étude. Les porcelets ont été pesés à trois occasions : en-dedans de 24 h à partir du moment du sevrage, et 3 et 6 sem suite au sevrage. Une concentration de 1 ppm d’iode était fournie dans l’eau de boisson. Des écouvillons ont été pris de tous les abreuvoirs et lignes d’eau, et des échantillons de fèces combinés ont été prélevés de tous les planchers d’enclos. Des échantillons de fèces ont également été prélevés des truies au moment du sevrage. Les écouvillons et les échantillons de fèces ont été vérifiés pour la présence de Salmonella et Escherichia coli. Dans les 24 h suivant chaque pesée, un examen oral complet était effectué sur chaque porcelet. Aucune différence significative dans la croissance (P > 0,05) ou les conditions dentaires (P > 0,05) n’a été trouvé entre les groupes de traitement durant la période d’ajout d’iode à l’eau. Après le sevrage, toutes les conditions orales délétères augmentèrent (lésions orales du sevrage jusqu’à 6 sem, taches et caries du sevrage jusqu’à 3 sem, gingivite de 3 sem à 6 sem; (P < 0,05). La présence de Salmonella a été détectée seulement deux fois à partir d’échantillons de fèces mais jamais des abreuvoirs. Seulement une truie s’est avérée positive pour Salmonella et E. coli O139:K82 et O157:K”V17 n’ont été isolées que rarement des abreuvoirs. Aucun signe de diarrhée n’a été noté tout au long de l’étude. Ainsi, l’ajout d’un supplément aqueux d’iode aux porcs en pouponnière n’a pas avantagé la croissance ou la condition orale. Les conditions orales délétères augmentent après le sevrage, la gingivite étant associée à un poids inférieur chez les porcelets.
(Traduit par Docteur Serge Messier)
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