LAUSR

Gilt progeny (GP) often have restricted growth performance and health status in comparison to sow progeny (SP) from birth, with the underlying mechanisms responsible for this yet to be fully understood. The current study aimed to compare differences in growth and development between GP and SP in the first 24 h after birth and in the peri-weaning period. Two cohorts of pigs including 36 GP and 37 SP were euthanized at 1 of 4 timepoints: a birth cohort (at birth before suckling, 0 h; and 24 h after birth, 24 h; n = 33) and a weaning cohort (at approximately 29 d of age; 'pre-weaning', PrW; and 24 h after weaning; 'post-weaning', PoW; n = 40). Pigs were individually weighed at 0 h, 24 h, PrW and PoW up until the point of euthanasia, at which time the weights of selected tissues and organs were recorded and analyzed relative to BW. The length of the small intestine (SI), femur and body were also measured, and a serum sample was collected and analyzed for immunoglobulin G (IgG) concentration. Samples of jejunal and ileal mucosa were collected and analyzed for total protein and specific activity of lactase. Euthanized GP were lighter (P < 0.01) than SP at all timepoints. At all timepoints the ratios of quadriceps weight to femur length, BW to body length, spleen to BW (all P < 0.05) and SI weight to length (P < 0.10) were lower in GP than SP. There was no difference (P ≥ 0.05) in stomach or heart to BW ratios between GP and SP in either cohort. The brain to liver weight ratio was greater (P = 0.044) in GP than SP in the birth cohort, and the brain to BW ratio was greater (P < 0.01) in GP in both the birth and weaning cohorts. The liver to BW ratio was similar (P = 0.35) at birth but greater (P = 0.014) in GP around weaning. Total mucosal protein content in the jejunum and ileum was lower (P = 0.007) in GP at 24 h compared to SP, and specific activity of lactase was greater (P = 0.022) in GP in the birth cohort, whereas there were no differences in the weaning cohort (P ≥ 0.10). Gilt progeny had lower (P < 0.001) serum IgG concentration compared to SP at 24 h, but there was no difference (P ≥ 0.10) in the weaning cohort. Collectively, these findings suggest that the early development of GP may be delayed compared to SP, and that a number of the anatomical differences between GP and SP that exist after birth are also present at weaning.