20 Assessment of lysine requirement in lipopolysaccharide-challenged pigs

This study was conducted to investigate the effect of immune challenge (IC) on digestible lysine (Lys) requirement of growing pigs using the Goettingen approach. Twenty-four 19kg-pigs were used in three nitrogen balance (NB) trials. The trials were performed in a complete randomized block design, with six nitrogen levels (NL), two sanitary status (control and IC) and two individual replicates per treatment (6 x 2 x 6). Dietary NL concentration ranged from 1.06 to 4.48 % in DM, being Lys limiting in all the levels assessed. For two consecutive days, Escherichia coli lipopolyssacharide (LPS) was intramuscular injected in challenged pigs at 30 and 34μg/kg. Data were fitted to nonlinear models to estimate nitrogen requirement for maintenance (NMR) and the maximum nitrogen deposition (NDmaxT). Both information were associated with the maximum nitrogen retention (NRmaxT), Lys efficiency (bc-1) and nitrogen retention (NR) to determine Lys requirements as follows: Lys = (lnNRmaxT-ln(NRmaxT-NR))/(16×bc−1). The NRM of pigs from control group was estimated in 152mg of N/kg of BW0,75/day, whereas LPS-challenged pigs had such requirements estimated in 197 N/kg of BW0,75/day. NDmaxT was estimated in 3525 and 2078mg of N/kg BW0,75/day in for pigs form control and LPS-challenged group, respectively. Requirements for Lys were estimated based on 68% and 54% of NDmaxT, being such percentage based on the mean value of ND for each group. Pigs from control group had the requirements for Lys estimated in 1.42 and 1.58%, based on a feed intake of 1000 and 900g/day, respectively, whereas Lys requirements of LPS-challenged pigs were estimated in 0.76 and 0.84%, based 893 and 803g/day of feed intake, respectively. Compared with control, LPS group exhibited a reduction of approximately 11% in feed intake. The model enables to estimate Lys requirement, taking into account protein deposition potential, feed intake, and immune challenge.