Nutrition: What do dental and oral conditions at weaning tell us about future growth?

Thursday, June 10, 2010

Research suggests that it could be beneficial to be able to select for earlier eruption of teeth as a way to improve feeding behaviour

by JANICE MURPHY

Although past studies have suggested that market pigs and breeding sows can suffer from serious oral and dental problems, this whole area continues to be overlooked in the field of swine research. Evidence suggests that there are significantly higher culling rates for sows, regardless of parity, which have damaged or worn teeth. This is most likely attributable to the discomfort associated with these conditions.

Recent studies involving piglets have shown that various dental and oral conditions (broken teeth, inflammation and oral lesions) can affect comfort and willingness to feed at a critical stage in development. One particular study reported considerable staining and cavities on the primary incisors of some piglets from every litter in a herd.

Given that staining and early onset of cavities have been linked to developmental abnormalities and poor growth rates in children, it begs the question whether piglets displaying these same characteristics may also be predisposed to poor health or suboptimal growth rates. To date, this type of information has not been reported for populations of piglets.

After weaning, pigs often face challenges in consuming enough feed, and normal tooth eruption has been proven to influence the development of feeding behaviour. Although there are differences among piglet populations in the age that eruption and occlusion of premolars take place, it is not yet known whether individual populations remain stable over time. Knowing the age at which the majority of piglets develop the tools necessary for coping with solid feed would be useful for producers, as they attempt to determine the optimum weaning age.

Researchers at the University of Guelph recently set out to examine the prevalence of abnormal dental and oral conditions in newly weaned piglets and to assess the associated weight gain over a three-week period. They also examined the eruption and occlusion status of weaned piglets to determine whether there is any consistency within a population over time. Occlusion refers to the manner in which the upper and lower teeth come together when the mouth is closed.

To accomplish their goals, the researchers performed oral examinations on 735 piglets (345 gilts, 390 barrows) from 70 litters at weaning from a commercial, 600-sow, farrow-to-grow operation. Deciduous teeth were recorded as being erupted or not (Figure 1) and occlusion between premolars was observed and noted. For example, p3 is the third maxillary premolar while p4 is the fourth mandibular premolar. Prevalence of tooth damage, oral lesions and staining or cavities was also determined and recorded. Pig weights were recorded at weaning and three weeks later. In a follow-up study, premolar eruption and occlusion data from 2009 (208 piglets) were compared to 2007 (180 piglets) from the same commercial herd.

The results.  Piglets averaged 21.5 days of age and 5.25 kilograms bodyweight at weaning, and 10.13 kilograms three weeks after weaning. In general, weight gain increased as weaning age increased and decreased as the number of live-born piglets per litter increased. The overall prevalence of abnormal oral and dental conditions, as well as eruption and occlusion status of all deciduous teeth at the time of weaning, is summarized in Table 1.

The eruption of p3 and p4 were positively correlated with weight gain at three weeks after weaning, with eruption of i1 showing a similar, but statistically insignificant, trend. Piglets that had the p3 erupted at weaning weighed 1.9 kilograms more after three weeks than piglets without this particular premolar. Similarly, piglets with the p4 and i1 erupted were 1.51 and 1.14 kilograms heavier, respectively, than their counterparts without these teeth at weaning.

Cavities or staining on i1 had a negative impact on weight gain. About one-third of piglets had one of the three reported abnormal conditions. The majority of affected piglets (29.7 per cent) had staining and/or cavities, or had oral lesions, while 4.5 per cent of the population had both. Very few piglets had broken incisors (1.25 per cent) and the researchers noted that these individuals were often difficult to examine; they exhibited pain-responsive behaviours, such as high frequency squealing, when the researchers touched the affected area. No piglets exhibited all three abnormal conditions. Only dental cavities or staining, or both cavities and staining, on the i1 were negatively associated with future weight gain. Piglets with one of these conditions at weaning weighed 0.56 kilograms less after three weeks than piglets without these challenges.

In the follow-up study, the results showed that dentition was more advanced at two, three and four weeks of age in 2009 when compared to 2007. Significantly more piglets in 2009 had eruption of p3 and p4 and occlusion between p3 and p4 at two weeks of age. This pattern of earlier eruption in 2009 continued on for three-week-old piglets in the eruption of p3.

The implications. Dental eruption and oral health are new areas of research for the swine industry and this study suggests that they are likely to provide novel insights into the growth, health and development of pigs. Although body weight is the standard measure for growth, assessment of teeth could provide a more reliable marker since their development is more resistant to nutritional disruptions in comparison to other tissues, such as fat, muscle or bone.

Dental eruption provides a unique area of research. The relationship between dental eruption and growth may offer mechanisms to help improve feed efficiency, aid digestion through mechanical chewing of food, and reveal related genetic linkages. The general lack of knowledge in all three of these areas suggests more research is needed to investigate the fundamental development of teeth in pigs and their key role in consumption, breakdown and digestion.

In this study, only the eruption of certain teeth (p3 and p4) was associated with weight gain, which may give some indication of the functional role of these teeth for animals at weaning. Alternatively, it may reflect the fact that these teeth are better indicators of growth rate or potential. A previous study by these researchers also found that feeding behavior was influenced by eruption of these premolars, along with the occlusion of p3 and p4, although this was only evident during the pre-weaning period.

Regardless of why more piglets in this herd achieved earlier eruption and occlusion in 2009 compared to 2007, the fact that this shift occurred may present an opportunity for geneticists and producers. It could prove beneficial to be able to select for earlier eruption of teeth, given that piglets are known to be more interested in feed after premolar eruption has occurred. However, the exact mechanism necessary to genetically influence eruption times has yet to be established. BP

Source: Tucker A.L., Widowski T.M., Friendship R.M. Associations between dental and oral conditions at weaning and future growth. J Swine Health Prod. 2010;18(2):68–74.

Janice Murphy is a former Ontario agriculture ministry swine nutritionist who now lives and works in Prince Edward Island.