161 The Impact of Sex, Birth Weight, and Nutrient Density on the Growth Restriction and Compensatory Gain of Finishing Hogs After a Three- or Six-Week Period of Nutrient Restriction

The objective of this analysis was to investigate the effect of pig phenotype on growth restriction and compensatory ability after receiving a nutrient-deficient (97% corn) diet for 3 or 6 weeks. Sixteen hundred and sixty mixed-sex pigs (DNA Genetics, Columbus, NE) were tagged with radio frequency identification tags (LeeO, Prairie Systems, Spencer, IA) at birth with litter information and body weight (BW) measured at birth, weaning, and the end of the nursery phase. At a starting BW of 73.5 ± 2.2 kg, pigs were blocked by BW to 140 pens and assigned to a 2:3:1 factorial. The seven treatments were comprised of a combination of 2 restriction lengths (3 weeks vs. 6 weeks) and 3 lysine inclusion levels at re-alimentation (Lys:ME of 100%, 110%, or 120% of the genetic margin over feed curve), and a control that remained nutrient unrestricted. Individual BW was measured on trial d 0, 21, 41, and market to calculate individual average daily gain (ADG) for each phase. Percent change in ADG between each phase was calculated using the previous ADG of each pig. Observational analysis was conducted in SAS 9.4 (Cary, NC) with pig as the observational unit. When fed the restrictive diet, gilts had a greater reduction in ADG (P < 0.01) than barrows (64 vs. 59 % decrease in ADG from previous period). Furthermore, pigs with lower birth weight, thus lighter starting trial weight, had a greater decrease (P < 0.01) in growth in response to nutrient restriction. Validating the biological requirements of finishing pigs, animals with a greater lysine requirement, gilts, and lighter weight pigs had a more severe reduction in growth than those with a decreased lysine requirement.