The goal of this project was to determine if changes in body condition that incur during gestation affect mammary development of gilts on d 110 of gestation. Gilts of a similar BW (138.1 ± 8.2 kg) and backfat thickness (BF, 16.4 ± 1.0 mm) at mating were fed different amounts of a commercial gestation diet to create 3 groups of animals based on body condition at the end of gestation. These were low (LO; 12–15 mm, n = 13), medium (ME; 17–19 mm, n = 13), and high (HI; 21–26 mm, n = 13) BF. All gilts were weighed and had their BF measured ultrasonically at P2 the day of mating and on d 30, 50, 100 and 110 of gestation. Blood samples were obtained on d 109 of gestation to measure IGF-1 and adiponectin concentrations. Gilts were then slaughtered on d 110 to collect mammary glands for compositional analyses. The MIXED procedure of SAS using a univariate model (3 levels) was used for statistical analyses and means were compared using the Tukey’s test. As expected, BW and BF were similar across all groups at mating (P > 0.10). Treatment differences were present for both variables as of 30 d of gestation onward (P < 0.01). Neither IGF-I nor adiponectin concentrations were affected by treatment (P > 0.10). Mammary extraparenchymal tissue weight was lesser in LO than in ME or HI gilts (1074.7, 1360.2 and 1578.4 ± 64.3 g, respectively, P < 0.01) and tended to be lesser in ME than in HI gilts (P = 0.06). Weight of parenchymal tissue was also affected by treatment (P < 0.05), being lesser in LO than HI gilts (P < 0.05), and tending to be lower in LO than ME gilts (P = 0.12). Values for LO, ME and HI gilts were 1058.6, 1369.6 and 1443.9 ± 198.7 g, respectively. Mammary cell number (DNA) in parenchyma was not affected by treatment, whereas metabolic activity (RNA) was greater in LO than HI gilts (P < 0.05). Total parenchymal fat was also lesser in LO than ME or HI gilts (P < 0.001). Body condition of gilts therefore has an impact on mammary development at the end of gestation. Thanks to Swine Innovation Pork for partial funding.