[Excerpts of a presentation by Carter J. Bisgard, Iowa State University, USA and colleagues at Pillen Family Farms, and DNA Genetics, during the 2025 Leman Swine Conference]

Pigs are born with 8 sharp pairs of teeth – four canines and four incisors. These teeth are referred to as needle teeth and are commonly used to fight for teats. The fighting can cause facial scarring and injury among littermates, and damage to the sow's underline. The most common way to combat this is to clip or resect the needle teeth. The practice of clipping needle teeth can be viewed as painful and unnecessary and requires additional care by farm crews. 

This study evaluated the impact of clipping needle teeth on pre-weaning mortality, piglet growth rates, piglet facial scarring, and sow underline lesions. Data was collected on 85 sows who were randomly assigned to treatments within parity blocks (42 with teeth not clipped and 43 with teeth clipped). The average parity for this trial was 3.1, ranging from 1 to 6. Cross fostering took place within 24 hours after birth and was performed within treatments. There was an average of 14 piglets per sow. 

Facial and udder lesions were scored on days 7, 14, and 21 before weaning, and conducted by designated personnel to ensure consistency. 

Lesion scores were classified into four categories: 

• None
• Low: Superficial scratches not penetrating the full derma thickness
• Moderate: Superficial scratches with some deeper wounds
• Severe: Deep and large wounds or lacerations or signs of infection 

Birth weights and weaning weights were collected to calculate average daily gain (ADG), and all death loss was recorded. Piglets whose teeth were intact had heavier weaning weights and increased ADG compared to the piglets with teeth clipped. On day 7, there was a significant increase in lesions from the litters with intact teeth compared to those with clipped teeth, specifically in the moderate to severe categories. On day 21 (at weaning) the teeth not clipped treatment had a greater number of piglets and sow underlines classified in the moderate to severe categories. 

Pre-weaning mortality averaged 17.9% for piglets with intact teeth and 15.7% for those with clipped teeth; however, this difference was not statistically significant. The teeth-clipped group weaned one additional pig per litter on average; a significant increase compared to the intact teeth group. 

When evaluating specific causes of death there was a numerical increase in injury trauma and joint infection from the treatment with teeth not clipped. In this trial teeth clipping resulted in decreased lesions in piglets and sow underlines, a numerical reduction in pre-wean mortality, but also decreased growth performance in piglets. These results indicate that producers may need to investigate when it is best to use the practice of teeth clipping to maintain the longevity of sow underlines and reduce facial scarring in piglets.