Intrauterine growth restriction in newborn piglets associated with piglet characteristics, colostrum intake, litter size and parity number in prolific sows

The genetic selection of highly prolific sows has increased the number of fetuses within the uterus, directly affecting piglet quality due to limited placental space. This results in placental insufficiency and fetal intrauterine growth restriction (IUGR). This study aimed to investigate the incidence of IUGR in newborn piglets within a commercial swine herd under tropical conditions and to examine its association with piglet characteristics, birth order, litter size, sow parity, colostrum intake, and mortality rate during the first 24 h of life. The experiment was conducted in a commercial swine herd in Thailand. Data were collected from 114 litters of French Landrace x Yorkshire crossbred sows. Immediately after birth, the degree of IUGR was determined in 1868 piglets, comprising 1743 live-born and 125 stillborn piglets. Sows were categorized into four groups based on parity number: 1 (n = 28), 2 (n = 34), 3-5 (n = 33), and 6-8 (n = 19). Litters were further classified by total litter size into three categories: 7-14 (n = 18), 15-19 (n = 51), and >= 20 piglets (n = 45). On the day of parturition, IUGR was visually assessed in both live-born and stillborn piglets. Various farrowing and piglet parameters were recorded, including farrowing duration and litter traits. Birth weight was measured before and after colostrum ingestion, and individual colostrum intake was calculated. The incidence of IUGR in newborn piglets was 16.2 % (302/1868 piglets), with moderate and severe IUGR observed in 10.8 % and 5.4 % of piglets, respectively. The percentage of IUGR piglets in litters with 7-14 piglets (8.5 %) was lower than in litters with 15-19 piglets (17.1 %, P = 0.008) and >= 20 piglets (17.2 %, P = 0.005). IUGR piglets exhibited significantly lower birth weights (832 +/- 28.6 g vs. 1274 +/- 16.8 g, P < 0.001) compared to normal piglets. They also consumed less colostrum (257.1 +/- 14.2 g vs. 414.3 +/- 7.4 g, P < 0.001) and had a higher percentage of individuals with insufficient colostrum intake (<300 g) (77.3 % vs. 27.6 %, P < 0.001). At 24 h postpartum, IUGR piglets exhibited lower rectal temperatures (37.7 +/- 0.1 vs. 38.1 +/- 0.1 degrees C, P < 0.001) compared to normal piglets. Additionally, IUGR piglets experienced a higher mortality rate within the first 24 h of life compared to normal piglets (18.5 % vs. 6.1 %, P < 0.001). In conclusion, the results demonstrate that IUGR piglets exhibit lower birth weights, reduced colostrum intake, and poorer thermoregulation. These factors contribute to the higher mortality rate observed in IUGR piglets compared to their normal counterparts. Moreover, the proportion of IUGR piglets increases with larger litter sizes, emphasizing the impact of uterine crowding. This study underscores the importance of managing sow productivity to minimize the prevalence of IUGR and improve piglet survival and welfare.