0
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. In addition to reducing environmental pathogens, iodine has been shown to be a powerful oral antiseptic 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.
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.
A research trial was conducted on a commercial farrow-to-feeder swine farm. The farm was on an antibiotic-free program and no antibiotics were used therapeutically or added to feed. A total of 208 piglets from 38 litters was examined across 3 weaning cohorts. Piglets had their 4 erupted needle teeth (i3, i3, c1, c1) clipped within 24 h of birth. 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. Piglets were weighed 3 times: within 24 h of weaning, and 3 wk and 6 wk after weaning.Water was provided ad libitum to piglets in bowl drinkers (2 drinkers/pen). An iodine-based sanitizer containing 1.75% titratable iodine was premixed with water at a 1% concentration in a 20-L container before being pumped into the water system, giving a final concentration of 1 ppm iodine.
Swabs 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. In addition, fecal samples were collected from all sows at weaning.The swabs and fecal samples were tested for the presence of Salmonella. The swabs were additionally tested for E. coli .
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. Eruption was considered to have occurred when any portion of the tooth crown had penetrated the gingiva. 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 i1, (2) gingivitis around any teeth, and (3) oral lesions on the gingiva, tongue, cheeks, or throat.
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.
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.
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. 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.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. 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, 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.
Anita L. Tucker, Abdolvahab Farzan, Glen Cassar, and Robert M. Friendship. Effect of in-water iodine supplementation on weight gain, diarrhea and oral and dental health of nursery pigs. Can J Vet Res. 2011 October; 75(4): 292?297.
