Impact of Feed Intake and Body Fat Deposition on Reproductive Performance and Placental Function of Shaziling Sows: A Pilot Study

Excessive body fat deposition during pregnancy is believed to have an adverse effect on the reproductive performance of sows. Feed intake regulation (REG) is an effective method to modulate energy intake and fat deposition. This study aimed to explore the impact of feed intake and body fat deposition on reproductive performance. A total of 24 Shaziling sows (parity 3–6) were divided into two groups based on their BF on day 30 of gestation, and subsequently randomly assigned to control (CON) and REG groups: (1) BF between 12 and 16 mm (LB-CON, n = 6), (2) BF between 12 and 16 mm (LB-IF, n = 6), (3) BF between 18 and 22 mm (HB-CON, n = 6), and (4) BF between 18 and 22 mm (HB-RF, n = 6). Sows in the LB-CON and HB-CON groups were fed a basic diet at a dosage of 1.88 kg/d. The LB-IF and HB-RF groups received REG and were fed a basic diet at dosages of 2.07 kg/d and 1.69 kg/d, respectively. Higher total litter weight and live litter weight were observed in HB-RF sows (p < 0.05). In addition, HB-CON sows displayed higher serum levels of IL-6, TG, and GLU when compared with LB-CON sows (p < 0.05), whereas HB-RF sows exhibited lower levels of these markers than HB-CON sows (p < 0.05). The lipid droplet area fraction was higher in HB-CON sows than in LB-CON sows (p < 0.05), and this fraction was reduced in HB-RF sows compared with HB-CON sows (p < 0.05). The placental level of TC increased in HB-CON sows when compared with LB-CON sows (p < 0.05). The placental levels of T-AOC and GPX increased in HB-RF sows when compared with HB-CON sows (p < 0.05). Moreover, the mRNA expression of FABP3 was higher in HB-CON sows when compared with LB-CON sows (p < 0.05). The mRNA expression of GLUT3 and PlGF increased in HB-RF sows when compared with HB-CON sows (p < 0.05). In addition, HB-RF sows exhibited increased Shannon, Simpson, and ACE indices when compared with HB-CON sows (p < 0.05). The characterization of the fecal microbiota revealed that HB-RF sows displayed a lower ratio of Firmicutes/Bacteroidota and an increased relative abundance of Limosilactobacillus when compared with HB-CON sows (p < 0.05). Collectively, these observations suggested that reduced feed intake in Shaziling sows with high backfat thickness improved reproductive indices, alleviated placental oxidative stress and inflammatory status, elevated placental nutrient transport and angiogenesis-related gene expression, and reshaped fecal microbiota. These results provide valuable reference for pig production.