Viability prediction and evaluation methods for neonatal piglets with low body weight gain and intra-uterine growth restriction

Increased litter sizes of modern sows have led to the birth of underweight and intra-uterine growth restriction (IUGR) piglets. This study aimed to predict the viability of neonatal piglets with low body weight (BW) and body weight gain (BWG) in day 1 and day 5 after birth. It also sought to determine if physical properties and alternative evaluation methods for IUGR could serve as reliable parameters for identifying piglets with low BWG. The physical characteristics of 108 piglets ([Landrace × Yorkshire] × Duroc) were measured. Thirty evaluators provided IUGR scores using an alternative method (Cronbach's α exceeding 0.9). These were compared with those using the conventional evaluation method, and the piglets were classified into normal, mildly IUGR, and severe IUGR groups. In the results, BW on the first day after birth was highly associated with head and left eye scores obtained in the IUGR evaluation, rectal temperature, and body lengths (P < 0.05 for all). These associations remained significant until day 5 (P < 0.05), except for the left eye score. In the conventional IUGR evaluation, head score, body mass index on days 1 and 5, and body lengths (excluding crown-to-rump and eye lengths) were higher in normal piglets than those of IUGR piglets (P < 0.05). Regarding BWG, using 0 g as the standard, piglets with negative BWG showed higher head scores than those with positive BWG (P < 0.05), while other body morphology scores for IUGR determination and physical properties were unrelated to BWG. When average weight gain (660 g) was used as the standard, piglets with BWG >660 g had longer body lengths than those with BWG <660 g (P < 0.05). However, morphology scores and piglet traits did not exhibit significant differences. In conclusion, significant variations were observed in BW, BWG, physical traits, and IUGR scores of piglets within five days after birth, highlighting the importance of proper management of low-vitality piglets to optimise their survival. Furthermore, our findings suggest that head score assessment may be a reliable, efficient method for identifying piglets with IUGR.