A preliminary survey examining the effect of oral health on feeding behaviour and efficiency in culled sows

Although the effect of oral disease in growing pigs on weight gain has been recognised and the incidence of dental disease has been observed to be high in sows (Knauer et al. 2007), the relationship between oral disease and feeding efficiency in pigs has not been examined. As the rate of sow culling has been linked to inadequate nutritional intake (Hughes et al. 2010), the role of dental disease should be considered. The high level of sow wastage has been identified as an important limitation on production. The hypothesis tested in this study was that oral disease of culled sows is related to feeding behaviour and efficiency.

Thirteen commercial-strain sows selected for culling at a large piggery in Victoria were examined in this study. Sows ranged from parity two to parity four. A feeding test was given in the piggery on the day prior to slaughter: 475 g of feed was placed inside a 25 by 25 cm square in a designated floor space, and each sow was video-taped until it consumed the meal in its entirety or left the area. The time taken to consume was recorded (feeding time) as well as the amount of feed remaining (if applicable). If eating stopped for 10 s then subsequent feeds were considered as a separate event. The rates of chewing (the number of mandible chewing motions per minute) with the head down and raised were calculated from the video data.

The oral cavities of the sows were examined post-mortem (at the abattoirs) (data presented in Table 1). The maxilla and mandibular lengths were recorded. The number of teeth that were chipped or cracked, displaced, missing or not erupted, and broken were recorded. The degree of periodontal disease, determined by the degree of gingival disruption around the tooth (mild or not present, n = 0 moderate, n = 4; advanced, n = 9) and calculus accumulation (mild or not present, n = 0 moderate, n = 4; advanced, n = 9) was estimated. A Dental Wear Index (DWI) was determined (the number of teeth with signs of wear multiplied by the severity of wear; from 0, not worn, to 3, severe). The relationships within the data were examined for significance using regression analysis and Fisher’s exact test (Minitab^®, Version 16.0; USA).

Missing or non-erupted teeth was negatively correlated to DWI (R² = 0.73, F-test = 29.9, P = 0.023). Sows with advanced calculus accumulation were more likely to have advanced periodontal disease (Fisher’s exact test; P = 0.014). The number of chipped or cracked teeth was positively correlated to feeding time (R² = 0.48, F-test = 4.83, P = 0.032).

It is concluded that there is a high incidence of dental degenerative degree occurring over the life of the sow and that dental abnormalities affect the efficiency of feed intake. This study was not able to take into account the factors that may predispose sows to dental issues, although it appears morphological factors such as jaw alignment and size may be important. As there has been little selective pressure for jaw and teeth morphology the high incidence of abnormalities identified was not surprising. The small numbers of sows limits the analysis of the correlation of the measurements. Further investigation of the time course of the degenerative processes may indicate when these abnormalities have an impact on feeding efficiency. The relationship of feeding efficiency to growth and production needs to be investigated. To be fully evaluated, the relative importance of the described dental abnormalities on sow growth, health and welfare needs further study.

Table 1.  Survey of dental abnormalities and feeding behaviour in culled sows. Values are mean ± SE